Nice gravitational lens observation! We're hoping to use the same technique with the Sun to observe exoplanets by launching a fleet of small satellites to 547 AU (80 billion km / ~3 light days). The craft would sample the distorted Einstein ring around our Sun from that vantage point, then combine and reconstruct an image of the disk of an Earth-like exoplanet up to 100 light-years beyond, at a resolution of 25 kilometers / pixel.
That depends on the planet used. If it works for earth, the next step might be Jupiter or Saturn, something that might be possible by only repositioning the spacecraft. It may even be possible to use the sun's atmosphere, the transparent part, as a lens.
How does the lensing work? Why doesn't the galaxy in the middle between us and the faraway galaxy pollute the image with its own light? It it separated by frequency or some trick?
And how would you get them out to, and stop at, 550 AU? Voyager 1 and 2 are nuclear powered with RTGs and they are respectively about 150 AU and 125 AU from the sun, and they are going really fast. The Voyager RTGs are also fairly depleted at this point. I’m guessing these spacecraft would need a faster, more efficient mode of propulsion, like a nuclear thruster or ion drive (or Epstein drive?!). One could also get a lot more fuel for the journey if the the probes didn’t have to launch fully fueled from the Earth’s surface.
No need to stop at 550AU, the gravitational lens keeps working beyond that(theoretically all the way to infinity).
As for how to get there, yes, innovative propulsion is required. My idea is that the probe would dive close to Sun and use solar energy (sail? electric propulsion?) to accelerate itself out to hundreds of km/s.
Voyager-1 is the fastest at 38,000 mph (61000 km/h) with respect to the Sun, but currently about 90,000 mph (144000 km/h) relative to earth (I guess this fluctuates annually).
That webpage says a tech demo is due 2024, with launch in 2034 and the constellation would reach 550AU by 2064, so probably a lot of how this will work is still WIP.
The problem with dates like that is they are pure best wishes. They might have funding for a demo in 2024 – although it isn't even clear they've got that yet, it sounds like they may just have funding to develop their proposal further. Even assuming the tech demo is successful, it sounds like they don't even yet have a detailed costed proposal for a 2034 launch, and no idea how likely that it will actually get funded.
Politicians and bureaucrats want immediate results, so a "launch now and see results in 30 years" mission – by which time many of the senior decision-makers will likely be dead – is going to be less attractive than competing missions offering results much sooner.
If you go back through the history of space exploration, it is full of proposals that "by year X we will be doing Y!" which never came to pass, because the money never turned up.
The downside of electoral democracy, is if you are only going to be be in power for 5-10 years max, why care about the state of the country in 30 years time, except out of the goodness of your heart? And electoral politics often does a rather poor job of selecting leaders with goodness in their hearts.
Of course, non-democratic systems have their own, equally serious downsides. Consider China: a system which is arguably much better at making long-term investments in public infrastructure than most democratic countries are (witness China's high-speed rail system), but also a system which ruthlessly suppresses dissent and locks up over a million of its citizens in "re-education camps"
>This makes me sad. The entire point of Government is to be an enterprise spanning multiple generations.
Not in a democracy. The point of a government in a democracy is to serve the current will of the people. The government itself might last many generations, but its goals and motivations change with every election cycle.
Even without politicians, the effective limit to most enormous projects is a human life span. Even if you look at projects that spanned 100-200 years like some cathedrals, they tended to be built in chunks: the main hall might be the first and largest, but things like trancepts, side chapels etc. would come later
In a hereditary absolute monarchy, the son (or more rarely daughter) may feel motivated to continue to the projects of his father (or more rarely mother), out of a sense of filial duty. In principle, it seems like hereditary absolute monarchy may avoid the problem you describe.
In practice, hereditary absolute monarchy suffers from the problem of the dud heir: Marcus Aurelius is remembered as one of the greatest Roman Emperors, his son and successor Commodus is remembered as one of the worst.
for downlink can't they launch a few extra sats that just sit around the Sun and form a big virtual dish (via baseline interferometry or what's that occult DSP magic called these days)?
> it’d still take 25 to 30 years for them to reach a vantage point
....
> mission designers would have to pick carefully because they could observe only a single target
It will take 30 years to get in position but then we can only look at one target? While it sounds very neat, I'd rather fund something we can use more than once, and sooner.
You CAN use for more than 1 target, you just need to reposition the telescope a bit. See [1], is a great great video on the subject. I can't recommend enough
If that can be done, it means the light and the info is there. Meaning here. The lensing and the 550 AU are just ways to catch it.
I should be highly surprised if we do not - long before 2064 - have optical and computational trickery to catch such resolution with snapshots from somewhere very close to home.
That's four times as far away as Voyager 1 is. I see from the link that it would take 25 to 30 years to reach that distance, and only one target could be observed: we would have to have one particular exoplanet we want to image and go to the right point for the sun to focus the image to.
Your link suggests the satellites word need to be around 2000 AU to avoid the corona, though I suppose the delta v requirements would be pretty small for such a large change so far from the sun (but my only source for the intuition is kerbal so take it with a grain of salt).
That's really cool. If it's good enough to detect geographic features, will it be possible to photograph the same planet from the night side later in its orbit?
That is incorrect. It's approximately at 150 AU[0]. For reference, that's about three times the distance of Pluto at aphelion. 547 AU is about 11 times the distance of Pluto at perihelion.
i guess i was thinking more about the complexity of arranging a constellation of telescopes around sol versus just sending one much closer to a target star.
All right hackernews. Genuine question, not sure where else to ask.
If galaxies and stars at the other “end” formed out of matter resulting from the big bang, just as the matter we are made of, how did we get here at the same time that that matter got there?
Is it because speeds faster than light are possible, and around the big bang all matter was spread near instantly at that speed? I don't understand how matter of the same “kind” was spread throughout the universe all at the same time without traveling at speeds greater than the speed of light. Because if we watch the ”opposite” direction from where the big bang occurred we don't really observe matter in a state closer to its original state, or parts of the universe in radically different states - which should result from that matter traveling further than the matter we are made of, as for us to now catchup with light that is “younger” than that towards the core of the universe. Am i missing something?
this is because things aren’t ‘moving apart’— space itself is expanding (into what? nobody knows). it’s not that the galaxies are being propelled apart from a force in a particular place either; everything is expanding away from everything else.
On the traditional balloon model, the surface of the balloon represents space itself. Those dots on the surface of an expanding balloon are not moving relative to space (the surface of the balloon), and so despite the distance increasing between us, the rate of increase of that distance is not bound by the speed of light, which only limits passage through spacetime.
> On the traditional balloon model, the surface of the balloon represents space itself...
For any still confused, there is also a 'raisin bread' model (which I prefer because it's 3D, unlike the surface of a balloon). The raisins are galaxies, and the bread is the space between them. As it bakes, the raisins get further apart, even though the raisins aren't moving through the dough.
(Although galaxies also have movement through space, this isn't what is causing them to get further apart.)
Omg, thank you for this! The balloon model always confused me because I could never understand what was in the middle of the balloon, and why we were on top of it. It's an odd 2d example using an object that is 3d, the balloon.
The raisin bread is a 3D expansion in 3D space. So from the viewpoint of a specific raisin the others are moving differently depending on what direction you look and you can use that to determine where the center of the bread is.
The balloon is a 2D expansion in 3D space, which is a better analogy for our 3D universe expanding in 4D space. From the viewpoint of a particular dot you see the exact same thing no matter what 2D direction you look. There is no center.
I agree that the balloon is more confusing, but it is more correct in that it doesn't lead to ideas like "the point where the big bang happened".
Your last point resonates with me. I had neither previously considered where the big bang might have taken place, nor that this would somehow be an erroneous concept. I scrolled through a bunch of disjointed answers on Quora that left me more confused than before. Could you point me to some good resource on that topic?
Is the a term for the 4-dimensional coordinate of the 'inflationary center', like there a 3d coordinate for the center of the balloon (inaccessible from the flat universe on its surface)?
Imagine that the balloon is actually completely flat and (to all intents and purposes) stretches infinitely in X and Y directions without wrapping around. As I understand it, we currently believe we're in a 3D version of that:
I wanted to propose bread with sunflower seeds, because raisins are gross. But now I'm intrigued: wouldn't chocolate melt when the bread is baked? Is it effectively ‘chocolate blob’ bread?
In case anyone is confused, I prefer to explain the expansion of space without metaphors.
Space itself is getting larger, everywhere, all at once. The scale factor of the universe is getting larger. New space is constantly being "made". Every second, every kilometer in the universe grows by 2.2×10^-18 centimeters. If no other forces were in play, it'd carry everything along with it and pull everything a bit further apart. However, local forces like gravity and the strong and even the weak nuclear force are more than sufficient to hold everything together despite this, so the expansion cannot be locally observed.
That's a small number, but the universe is very big. The hubble constant is usually represented in km/s/Mpsc (kilometers per second per megaparsec), and in those units it comes out to 68. So, every second, every Megaparsec in the universe grows by 68 kilometers. The more parsecs between us and some distant thing, the more space is growing between us and them every second.
For reference, our nearest galactic neighbor is Andromeda, which is 67 kpc away, so about 100 meters of new space is created between our galaxies every second. That being said, Andromeda is heading towards the Milky Way at 110 km/s, so it easily overcomes this and will crash into us any day now^W^W^Win 4.5 billion years.
>Every second, every kilometer in the universe grows by 2.2×10^-18 centimeters. If no other forces were in play, it'd carry everything along with it and pull everything a bit further apart
This sounds like a measurable (in principle) pressure. But you say it cannot be locally observed. So how do we actually know it is happening?
I have heard for many, many years that "space itself" is expanding, but never got a sense of what that meant from all the explanations. It's always sounded to me like doubletalk. Probably because I'm dumb.
What I have heard about observations of the expansion of the universe is that objects appear to be moving away, and I've never been able to understand how we know it is not "ordinary" motion.
The motion is consistent with an expanding universe. It gets exponentially greater the further away you go, and everything is moving away from everything else - not away from some "center" position. Also, some of this movement is faster than the speed of light, and the expanding of space explanation is consistent with our understanding of physics whereas proper motion is not consistent with our understanding of physics.
Ok, so given a bunch of objects, there are some configurations of velocities that prove different physics are at work, than other configurations.
This just sounds weird, like I thought that Newtonian or Einsteinian physics explained objects with velocities regardless of what those velocities are. I thought there were somehow complete, you know?
I don't really understand any of it, but I read a popular account of relativity by Einstein, and you know, the examples were very 100 years ago, trains, light, geometry and stuff. No magic.
Space literally expanding seems like this star trek thing jumping out of nowhere, and it's confusing to me where it comes from, even though I appreciate that it's orthodoxy nowadays.
Maybe the point is the magic has something to do with general relativity?
So the I wonder if everything expands along with the universe, does it mean that from outside, things moving at the speed of light in our universe, are potentially moving at speeds greater than the speed of light within our universe? If i was watching from outside, a rectangle moving at the speed of light in our universe, would one of its edges be moving away from me at the speed of light + the speed of expansion? If it makes sense.
That question is too abstract for me to reason about. A "rectangle" couldn't move at the speed of light; light is point-like (oh dear, saying that could get me in trouble). Anything with mass cannot move at the speed of light, and anything without mass must move at the speed of light, and all known objects without mass are point-like. And then there's the question of observation in the first place - observation itself is governed by fundamental particles, and observing a fundamental particle at its scale is theoretically impossible.
I know you want me to cheat and set aside all of these complications and just imagine a rectangle moving at the speed of light, but such an answer would be nonsensical.
But the answer to the more specific question, "does the expansion of space make something move faster than the speed of light?", is "no", but it does cause the distance between objects to increase faster than the speed of light. To an external observer (which is inherently difficult to reason about, for the record), these objects would appear to "move" away from one another faster than lightspeed. However, the very idea of "movement" is rooted in the context of spacetime, and is bounded by the speed of light, so it's a confusing/nonsensical question.
See also the observable universe: https://en.wikipedia.org/wiki/Observable_universe. As the universe's expansion speeds up, we will never receive further information from some parts of the universe as it "moves away from us" faster than the speed of light.
Space is growing, not the matter within it. The diameter of a hydrogen atom is dominated by the fundamental forces, and the expansion of space is insufficient to overcome this force.
I thought it was explained. Local gravity is moving things together much faster than general expansion is moving them apart. At super super long distances, gravity is weaker than expansion, so something very far is disappearing while something nearby may be collapsing.
However, that questions a different future I’ve seen in popular science talks: That the future becomes dark because of expansion. That makes less sense to me now, since it would seem that a merged set of galaxies would keep plenty of local stars in the skies. Assuming that stars are born as fast as they die (but I don’t recall seeing an answer to the ratio of star births vs star deaths at a local level).
The rate of expansion is speeding up. If it continues to increase, eventually it'll have observable effects at interstellar scales, and even interplanetary scales, and ultimately tear everything apart in the "big rip". Note that I'm omitting a lot of context here, there's a lot of other factors which make the big rip scenario much less likely.
Also, the age of star formation will eventually end. Stars will stop forming somewhere between 1 trillion and 100 trillion years in the future.
If I understand what you’ve written already, the essence of the answer in terms of mekkkkkk’s question (for reference: “ Sorry for also asking a space 101 question, but since the fabric of space is expanding, does that mean that things are getting bigger as well? Naively, it would seem that way. In your balloon example, the dots would get bigger.”), I think the answer would be:
Anything held together (for example by gravity, or the force that keeps out atoms together) is not growing along with the universe simply because those forces are (for now) stronger than the expansion.
This does produce an interesting side question though: aren’t we (humans) shrinking in relation to the universe?
Or, without the click-baity phrasing: isn’t the universe growing without us?
>This does produce an interesting side question though: aren’t we (humans) shrinking in relation to the universe? Or, without the click-baity phrasing: isn’t the universe growing without us?
> However, local forces like gravity and the strong and even the weak nuclear force are more than sufficient to hold everything together despite this, so the expansion cannot be locally observed.
OK, we have a meter stick. It's made of pure iron and, for whatever physical reasons, it is 1 meter long exactly.
After some time, the scale factor of the universe grows, so that 1 new meter is 1.05 old meters. But, by hypothesis, as this happens, our meter stick contracts, so that it ends up being just 0.952 new meters (= 1 old meter) long. Why? Did the physical laws governing iron atoms change so that they pack more densely than before?
And if so, why do all particles pack at exactly the same new density? Shouldn't it differ from molecule to molecule?
But the scale of quarks increases just as much as every other scale, doesn't it? Why did the iron rod shrink while space grew? Why are the iron atoms closer together now than they were before? Why are the protons in each iron atom closer together now than they were before?
The iron rod didn't shrink, it's more like it just held together. If I have a rubber sheet with a ball on it, and I pull at the ends of the rubber sheet, it's not going to pull the ball apart. The binding force of the ball's constituent atoms is sufficient to overcome the pulling force. And in the case of dark energy, the pulling force is absoultely miniscule at those scales.
>The iron rod started out being 1 meter long, and now it's 0.952 meters long. In what sense did it not shrink?
In the sense that it did not become 0.952 meters long. It didn't "become" anything - it did not change at all. The universe grew around it, or perhaps "underneath" it. More space appeared for it to exist in. It's like putting an iron rod in a 10 meter square house, then moving the walls out another meter.
Edit: let me phrase this another way. Let's imagine that you and I were pulling on the bar at either end. We could pull it forever and ever and it would never come apart (unless it rusted and became brittle or something, but let's imagine it doesn't). That's because we aren't putting in enough force to overcome the forces which are holding it together. Well, the expansion of the universe is putting like 10^-20 times less force into it than our arms would be.
This is a very different idea from "it's the same amount of space, but bigger", which is what I understand by the claim that a scale factor is increasing.
Well, space isn't a tangible (and finite) thing. It's the manifold in which the universe exists. Increasing the scale factor doesn't "stretch" space, it just makes... more of it.
>"space itself is expanding (into what? nobody knows)"
I have a terrifying theory on this (granted, the Earth will be long gone). What if the universe is not actually expanding in the sense that it is being propelled by an initial explosion, but instead falling towards a much greater mass - the end of time so to speak, where all mass ends. Considering that gravity is a "weak force", the scale of such a mass makes me uncomfortable to think about.
Perhaps what we observe as the fabric of space-time itself "stretching" is actually a similar process to what happens to matter as it enters a black hole?
Interesting, this adds to a thought I had a couple of weeks ago.
We can see the past, but we can’t go there, like an observer inside event horizon looking out, they can see light coming in, but can’t leave.
We can’t see the future, but when we are going there, like an observer falling into the event horizon. They can’t see what’s inside, but they can fall inside.
As we experience time, it’s like we are falling into a black hole made of time.
It's possible. The issue is that the we really don't have any information beyond what we have. We have an idea of the big bang and the expansion of the universe. We have knowledge of certain factors etc. But really, we're not really equipped to handle the scale of the cosmos.
From my layman's perspective, I think this is plausible, and many physicists seem to agree it's plausible. Maybe another plausible explanation could be the reverse: maybe before the Big Bang, our/the universe was in the state you describe, and the Big Bang is our perception of it "snapping back" and exploding violently outward (aka a white hole).
Carlo Rovelli and others propose that black holes actually only appear as they do to us due to the extreme time dilation, and similar to how a photon's "perspective" is that it's experiencing all of time at once, a black hole's perspective is that it's basically a massive explosion that occurs at essentially the same moment it forms. So under this hypothesis, a black hole never reaches a true singularity, but as close to a singularity as physically possible, and then it almost instantaneously bounces back like a taut rubber band that's stretched back as far as it'll go. From our perspective on the outside, it's an intense explosion occurring in very slow motion, and from the perspective on the inside, it's an intense explosion happening all at once.
Rovelli posits a Planck star, not a singularity, exists past the black hole's event horizon, and the Planck star is the state of maximal compression between the black hole and white hole phases. And somewhat related to this, if I understand the theories correctly, our universe might be a supermassive white hole, and we might hold the perspective of being inside of a super(super)massive black hole that's turned into a white hole and is exploding and jettisoning everything inside of it. Or some stage after that. The ultra-compressed energy before the Big Bang would be an (extremely massive and dense) Planck star.
I have no idea how likely the Planck star theory or white hole universe theory might be, but my blind speculation is that if it's true, maybe dark energy is whatever's fundamentally responsible for gravity/curvature causing our white hole explosion to bend some outer medium - the hypothetical potential medium which our black hole/universe originally formed in - and interact with other extreme contractions and explosions also happening in that medium, in complex and multivariate ways. Maybe a white hole being pushed into or prodded or yanked by many other black holes and white holes from different directions and angles could be perceived from the inside as accelerating expansion of space at certain scales.
Maybe this is happening recursively, even; maybe that outer medium is itself within another even greater medium, which also is within another greater medium, etc. Maybe the nesting depth is small, or near-infinite, or infinite. Or maybe there is no outer medium to our universe, in which case that whole idea's shot.
And I'm not sure if this could be related, but Rovelli suggests the hypothetical Planck star cycle of black hole to white hole applied to primordial black holes that formed in our early universe could explain dark matter, so even without the outer medium idea there could be something here that helps us understand our large-scale observations. Maybe there could be some relation to the "dark fluid" and negative energy idea, too: https://en.m.wikipedia.org/wiki/Dark_fluid
I have absolutely no clue if your or my speculation is reasonable or not (there's currently zero evidence of any sort of outer medium, as far as I know), but the general concept of our universe being the result of a black and/or white hole does definitely seem to interest a lot of physicists.
> Carlo Rovelli and others propose that black holes actually only appear as they do to us due to the extreme time dilation, and similar to how a photon's "perspective" is that it's experiencing all of time at once, a black hole's perspective is that it's basically a massive explosion that occurs at essentially the same moment it forms. So under this hypothesis, a black hole never reaches a true singularity, but as close to a singularity as physically possible, and then it almost instantaneously bounces back like a taut rubber band that's stretched back as far as it'll go. From our perspective on the outside, it's an intense explosion occurring in very slow motion, and from the perspective on the inside, it's an intense explosion happening all at once.
I’ve been yelling like a crank for a while that a black hole is actually a massive explosion we see in (ultra) slow motion, so it’s really cool to hear I’m not alone, and that other people call it a “planck star”. I haven’t heard anyone connect that to the big bang being a white hole, but it does make a lot of sense, even if we currently have no direct observable evidence or even any theoretical predictions.
Thanks for sharing, now I can follow along the research.
Don't know why you're being downvoted. It's definitely not too crazy of an idea, given what's been known since general relativity was confirmed and the discovery that black holes do indeed exist. I haven't looked into it, but I wouldn't be surprised if many other people have proposed it in the past. I haven't heard or thought of it before, but when I first read it it definitely made a lot of sense, intuitively.
Maybe the downvotes (which seem to no longer outweigh the upvotes?) are because you said "is actually" rather than "might actually be". Humility and uncertainty is crucial in science. Even for a field that's much more testable, and even for a leading scientist in a field, let alone some random speculator on the internet. It's fun to think and talk about these things, but especially as total amateurs, we should never claim anything with even a little bit of confidence.
My own speculative stuff I posted above is probably all dead wrong and hopelessly confused; I'm just throwing it out there as stuff that's popped into my head. And Rovelli may be wrong, too, though he's a highly-respected theoretical physicist and has published several papers about it. And even if the Planck star and black hole/white hole theory is true, it may not necessarily mean it has anything to do with how our universe started; that's just additional unsubstantiated speculation by me and some other people, and not anything Rovelli has claimed, though his theory seems to have increased discussion about that topic.
You’re dead-on about humility. I meant it was nothing more than my idle speculation based on my shallow understanding of physics. I was just so excited to see there’s an entire theory around it! Thanks for sharing more resources. Cosmology continues to fascinate me.
I don't know why you were downvoted, the theories you referenced sound as plausible as any other to me (but then again I tend to assume everything comes with a touch of bullshit).
The situation you described would result in a game of universal pong, in which matter is passed from one side of the universe to the other before reaching a critical point where it bounces back. Obviously I have no means of validating the "Plank star beyond the horizon" theory, but nor can anyone else can prove differently at this point.
>So under this hypothesis, a black hole never reaches a true singularity, but as close to a singularity as physically possible, and then it almost instantaneously bounces back like a taut rubber band that's stretched back as far as it'll go.
Kind of like a graph of 1/x, where everything behaves predictably, but there's that one point that doesn't fit?
I'm absolutely terrible and uneducated when it comes to math, so I'm not sure exactly what you mean. But if you mean 1/x where x = infinity, then yes, the classical idea of a singularity (such as what's been theorized to exist within a black hole, curving to an infinitely small point) is basically like 1/infinity or dividing by zero.
Rovelli hypothesizes this never actually happens and is not physically possible, and rather, when the most physically extreme possible level of curvature does occur, it "snaps back". If true, this ensures black holes do actually behave predictably, and physics doesn't actually break down; it just gets as extreme as it can possibly get.
So under this hypothesis, x gets really high, but the universe prevents it from ever reaching infinity. This would also potentially resolve some paradoxes related to black holes.
I'm not terribly educated either, but if you don't mind a minor possible correction, I suppose GP would have meant x = 0, which is the only point where the function would be typically undefined, and the closer x gets to 0, the more f(x) approaches infinity. Conversely, the more x approaches infinity, the more f(x) approaches 0. Also, because of the way these things are usually defined, it doesn't make sense to say x = infinity, it only makes sense to say x approaches infinity (but it might make sense in nonstandard calculus, where infinitesimals are defined - here my ignorance already shows).
I really appreciate your comments! If you're interested in hypothesizing about physics, I think it would do you a lot of good to learn at least a bit of math to go with it.
> "I really appreciate your comments! If you're interested in hypothesizing about physics, I think it would do you a lot of good to learn at least a bit of math to go with it."
Not disagreeing, I just wanted to suggest that the ideas come first, right? The math simply frames the ideas in a way that we can quantify and discuss, while also providing a "line in the sand" that other ideas must be compatibile with in order to be accepted among other the ideas that have already crossed that line. Those are very important things, but I would suggest that they are merely supporting an original idea that does not require math to intuit.
Thanks, I knew it had to be either zero or infinity. A singularity would indeed be like dividing by zero, which is why, if they exist, physicists would have a lot of trouble describing them mathematically.
I almost never really think or talk about physics in general. This thread just caught my eye.
Although there is projective space where it does make sense to say x = infinity (and also that f(0) is defined). In projective space all of the conic sections (lines, hyperbolas, ellipses, parabolas) are connected loops.
My high school physics professor had a great take on this: The universe is defined as “everything”. If we ever find anything outside the universe, we’ll call that the universe too.
That doesn't really answer the question, what the parent is really asking about is whether we are living on the surface of a manifold that's due for some kind of a collision with something else.
Sorry for also asking a space 101 question, but since the fabric of space is expanding, does that mean that things are getting bigger as well? Naively, it would seem that way. In your balloon example, the dots would get bigger.
Not in practice. In practice, this provides a very tiny force pulling subatomic particles apart in an atom's nucleus, or pulling atoms away from each other in a molecule, or pulling a celestial body's molecules away from each other. It makes no difference at all, because that force is absolutely dwarfed by the strong nuclear force, electromagnetism, or gravity, respectively. Systems that are coupled together by those forces, up to and including galaxies, are impacted only very minutely by this expansion.
For the expansion to have a significant impact on relative distances, the distances involved have to be so extreme that there's no real other interaction between the objects you're measuring from.
Yes, it will create some additional potential energy.
That doesn't contradict strict conservation of energy - it just adds another energy source that has to be accounted for when balancing everything.
It might contradict the aphorism "energy is never created or destroyed", but I'm not sure that was ever science.
It's more fun to think about it in terms of thermodynamics. Can that extra energy be used to reverse the second law of thermodynamics? I'm guessing not - it's so diffuse that it's probably impossible to use it to reduce entropy. The math for actually doing those calculations is well beyond what I know, though, so I'll just say that one's no more than a guess.
Like other gravitational effects, locally, spatial expansion would manifest as a pseudo-force, but be too weak to overcome the nuclear and electromagnetic forces that keep matter bound.
However, Friedmann cosmology is only a large-scale approximation. A more realistic model is swiss-cheese cosmology, which comes with a different metric within the 'holes', and spatial expansion might indeed not act on galactic scales (though I would image it to have an indirect effect as boundary conditions at the edge of the hole have to be matched; I'm no expert on this part of the story, though).
The usual response of “it only affects space between galaxies not inside galaxies” is deeply unsatisfying, and feels like it must be an oversimplification.
What I think is meant, but I absolutely want someone wiser to confirm or refute, is that the rate of expansion is proportional to distance, and therefore so small inside a single galaxy it can be ignored.
What I don’t know is: can any orbits still be stable in an expanding universe?
(In theory I could simulate the orbits question easily; in practice, last time I tried to do astrophysics maths I made an elementary mistake).
it only affects space between galaxies not inside galaxies
It obviously affects all space, inside galaxy or outside of it. Let's just check the rough math, not even bothering about the fact that expansion was not linear. The universe expanded to around 100BLY in about 10BY, i.e. got ten times bigger than its potential light cone. So, for every "initial" 1km, there is additional 9km in 10BY timespan, or 0.0009mm per year, or 0.00003nm per second. The general ratio is around 1e-17 per second per length unit.
Proton size is around 1e-15m, Planck size is around 1e-35m. A thousand Planck units per second is not that much, really. And on sub-milliseconds it just loses its effect completely, due to that Heisenberg guy. (If we take my bullshit math seriously, I mean.)
Yes, because the "Hubble Constant" is expressed as km/s/Mpc (that's Megaparsec), and the value is thought to be around 70. 70km/s seems crazy fast, until you divide by the 3,300,000ish light years (each light year being about 6,000,000,000,000 miles).
Of course, if you calculate out far enough time, you would eventually end up with the observable universe getting smaller (because the stretching of spacetime would take away more space than was added by light reaching us from further away), down to our galaxy, and eventually everything getting torn to shreds, even down to protons...
In the "near" term, the effect is so small that we have much more to worry about from the sun expanding in a few billion years than the Big Rip.
> What I think is meant, but I absolutely want someone wiser to confirm or refute, is that the rate of expansion is proportional to distance, and therefore so small inside a single galaxy it can be ignored.
I am not that person. But I feel like this can't work -- if all space is expanding equally, in proportion to its own extent, then we would perceive no expansion at all. If two points start out 1 light year apart, and over time 1 light year expands to be 10% longer than it was before... and also, everything in the universe expands to be 10% larger in all spatial dimensions... then the distance in meters between the two points hasn't changed, because meters grew too.
The problem with that model is that as was previously said, the electromagnetic, nuclear, and gravitational forces easily countermand the expansion on non-inter-galactic scales, to the point of not being measurable on the scale of a meter. Ultimately the molecular structure of your meter-stick is determined by various structure constants that aren’t changing, so the expansion can’t affect it unless it starts ripping bonds apart.
> Ultimately the molecular structure of your meter-stick is determined by various structure constants that aren’t changing
Really? These structure constants never involve any units of distance? Isn't distance changing at all levels?
If I have a meter stick, and then space expands by 10%, you're saying that my meter stick will end up being 0.91 new-meters long, yes? Wouldn't that require the structure constants to change, to allow for the same molecules to take up less space?
Structure constants are unitless by design. But obviously constants like the speed of light that do involve distance are unchanged too so that’s not a satisfying end to the story.
Let’s come at this from the other direction: if everything including the space between atoms and galaxies expands by 10%, how do you tell the difference between an old-meter and new-meter? For this to be observable, something has to still scale by the old-meter, or you wouldn’t be able to observe a difference at all. That something would be the physical constants with units, like the speed of light. This means the electrical force governing the chemical bonds in your meter stick will still try to restore the distance between them to their original old-meter distance, but in new-meter units.
Then if you define the actual meter by the length of your meter stick, or the physical constants, you end up getting the same meter that everything not macro-scale “snaps back” to.
So just to clarify, the new-meter would be smaller if judging solely by the extent in space? But not compared to any other physical object since they are all kept together by forces that are constant regardless of space?
It's not the idea of a meter that's expanding. It's the physical space that starts out a meter long/deep/wide that's expanding.
The meter-long stick you put into that space to measure it is still one meter long at some time in the future because the force that pulls the space apart (dark energy) doesn't pull on the matter that makes up the meter stick strong enough to overcome the forces that hold the stick together. But even if it did, the idea of one meter hasn't changed its definition. It's just the tool you used to measure one meter has broken.
I came up with the analogy of 2 pairs of independent dancers on a large checkerboard floor. Lets say the tiles are 10cm^2 and the two couples start out 10 tiles apart.
Every second, the tiles on the floor push away from all their neighboring tiles by one tile width and new tiles appear in their place. The tiles are small enough that the dancers are easily able to adjust their step/grip on eachother to simply maintain their dance routine.
However, even tho the dancers can stay together, the couples drift apart at an ever increasing rate. They start 10 tiles apart, after one second the couples will be 20 tiles apart from eachother, 40 tiles apart after 2 seconds, 80 tiles apart after 3 seconds (a new tile is being inserted between each pair of existing tiles). My tiling math is probably slightly off, but I think this illustrates the exponential increase in expansion.
The dancers are quarks, atoms, molecules, planets, galaxies, etc. Their grip on eachother is big enough to overcome the relatively small adjustment in the space that was created between them.
A few questions using this analogy arise.
Do the new tiles actually appear between the dancers, or is it more a case of the force of friction the dancers are applying to the floor prevents those tiles between them from moving apart ?
So when 'new space' is being created, is it created around strongly bound things and the things simply slide around through this new space to maintain their current configuration, or do the 'strong' forces prevent new space being formed around them ?
If the new space is not being created, what happens to the energy that would have gone into the creation of the new space ? Does it simply get applied to the nearest point where it can squeeze in more space ?
If the space is being created and the dancers pull themselves together to overcome it, where does this extra energy come from ?
As for the big rip, I always thought it was the equivalent to the dancers finally getting tired and not being able to hold onto eachother hence giving in to the expansion of space. ie. It happens around the heat death of the universe when everything has dissipated its kinetic energy so much that the energy of the expansion is more than is left in the system to keep things together.
Interesting analogy. So in effect to someone “watching” from outside our universe anything moving at the speed of light in our context, is moving either faster or slower than the speed of light in their context. Since the ballon and everything inside is expanding it means that either things are moving at the speed of light + speed of expansion, or speed of light - speed of expansion, when watched from outside. Assuming that everything expands along with the balloon. If I understand this correctly, and according to:
“Due to the expansion increasing as distances increase, the distance between two remote galaxies can increase at more than 3×108 m/s, but this does not imply that the galaxies move faster than the speed of light at their present location (which is forbidden by Lorentz covariance).”
But from outside we can move faster than the speed of light? Sorry having trouble getting my head around this.
> Since there's no frame of reference outside the universe
That's unknown. The observable universe is all we know for sure and there's evidence that there is both something beyond what we can observe, which conforms to what we know as space and matter, and something beyond that (whatever existed around the big bang locality).
That's an arbitrary definition. We can't observe our local past events or even non-local events, yet we use them as theories/evidence depending on context (eg Red Shifted galaxies as evidence of expansion). Reasoning about past events would affect other future events is just as much evidence. That's how physics experiments are generally conducted.
Then explain the Hubble volume: unless you believe the Earth is at the center of the universe, basic reasoning tells you that there is a sphere beyond which is outside our light cone, and yet outside which the universe still exists.
Are you saying the observable universe is bounded to our Hubble volume?
>basic reasoning tells you that there is a sphere beyond which is outside our light cone, and yet outside which the universe still exists.
Of course, but basic reasoning isn't evidence. Again... "evidence" implies something that can be observed, and something that can be observed, by definition, lies within the observable universe.
>Are you saying the observable universe is bounded to our Hubble volume?
I'm saying the observable universe is bounded to what we can observe, and evidence of something beyond the observable universe is a contradiction in terms.
great sci fi plot, the earth is the center of the universe because anything out side of our sphere can’t be observed by our consciousness and ‘collapse’ into existence :)
kind of yes, relatively from an "outside observer" that would be the case.
but if the usual laws of physics apply to that outside "observer" then it will not be able to observe photons from those objects.
the usual assumption is that space is basically infinite but we can only observe our own "observable universe" sphere of it. every point in space has its own universe basically.
>space itself is expanding (into what? nobody knows)
This is a conflation of two different things. Most of the current evidence points to a universe which, when it began, was already infinite in size, but infinitely dense. In that model, it remains infinite in size, but is also expanding.
To give you specific terms to research on, in cosmology this is called the "horizon problem" or the "homogeneity problem," basically put as "Why is the stuff over there so similar to the stuff right here when they're so far away? They ought to be causally disconnected by distance!"
The answer to this in the early universe is called inflation, which you can tag onto Alan Guth around 1981 or so. It involves spacetime itself stretching. Originally, everything was nearby and so it was all evened out -- about the same temperature, density, and so on, then it just gets pulled apart and "writ large" in a twinkling.
The universe may have alway been infinitely large. Its just that 14.8 billion years it started expanding, first at inflationary rates, then a slower strain of 10E-18 / second.
Its a lot like looking at a number line. That is infinitely long in both directions. And if consider all real numbers, it is infinitely expandable.
I don't fully understand your question to give a direct answer, but I think that's mostly due to a number of misconceptions you hold about the universe. So I'll just try to clear those up instead.
First of all, the big bang didn't happen somewhere, it happened everywhere. There's no "center" of the universe that everything is moving away from. The universe did not start from a point, it started from a small scale factor and the scale factor rapidly increased.
Assuming the universe is infinite (we're not sure), you could think of it as expontentially more infinities being created all the time. Say you take a 1-dimensional line and put tick marks 1cm apart, to positive and negative infinity. Then you multiply every tick mark position by 2. Two times infinity is still infinity, but the nature of the infinity has changed: it's scaled up by a factor of two. You could then subdivide it again, adding markings in between, 1 cm apart. You can think of these new markings as representing new centimeters which have appeared on your 1D line. This is happening to the universe in three dimensions.
Now, instead of doing this by discrete intervals, just do it constantly, so the scale factor is always expanding. Any two points are always moving apart from each other at the rate of this expansion, let's say 1cm/cm/sec. Now, introduce an attractive force between objects (e.g. gravity) which obeys the inverse square law. If the objects are sufficiently close to one another, they'll move towards each other at a rate faster than 1cm/sec, which would overcome the expansion force and allow them to remain together. In the real universe, the fundamental forces have this effect, and this is why we don't observe everything flying apart on local scales.
Now let's say that the maximum speed limit is 10cm/sec, and light travels at this speed across our 1D line. If we have two objects 2cm apart, then the distance between them will grow by 2cm in one second. In that time, light from each will have travelled the same distance and met one another. Now, they're 4cm apart, and in the next second will travel 4cm apart, twice as fast. Light can still make this journey. At the next tick, they're 8cm apart, and light still makes it. 2/16th of a second later and they'll be 10cm apart and moving away from each other at the speed of light.
At this point, no future emissions will reach them. However, we haven't been emitting discrete light pulses - galaxies continuously emit staggering amounts of light. So, the space between them is full of light which is constantly making the journey towards the other end. If no other factors were at play, they'd still be receiving old light from each other forever. But there are other factors at play: the inverse square law, combined with the increasing redshift, will eventually reduce the light to effectively nothing.
These factors are sufficient to extend the effective observation duration of distant objects well after they've crossed the lightspeed event horizon. To recontextualize this into our real universe, we can look at extremely distant objects like GN-z11, which is 32 billion light years away. If light were to re-tread this distance, it would require twice the current age of the universe to complete the journey. However, this light only took 13.4 billion years to reach us, because it was emitted when the universe was much closer together, and carried towards us on the "flow" of expanding space time, while the object was carried away from us on that same "flow" - faster than the speed of light.
Ok, thanks for clarifying - indeed i seem to have had quite a few misconceptions. But from outside the universe, are things inside of our universe moving faster than the speed of light due to our universe expanding, and as such, things traveling at the speed of light when seen from the outside are traveling at the speed of light + speed of expansion?
But I'll give you another analogy anyway. Say you put two rocks into a mass of water in an environment without gravity (e.g. the ISS), then freeze the water, causing it to expand. The expanding ice will cause the rocks to become more distant from each other, but they're not "moving" in local terms - the manifold in which they exist is itself expanding. That said, the frozen water and the rocks both exist in space, and the expanding ice moved the rocks through space. But, in this metaphor, there is no second, external "space" - the water itself represents space.
And so to for our universe. Space itself isn't a part some other, second "space" that it's expanding into (at least not so far as we're aware). The existence of somewhere for space to expand "into" is not necessary for the expansion to take place. Remember, it's the scale factor which is changing, not a discrete object (i.e. the universe) physically expanding.
There is nothing outside the universe. The cosmic background radiation is, in a sense, the furthest thing we can observe, which is the remnant of the big bang. And yet it is the same everywhere. So the surface of the bubble actually represents a single historical point! That implies some strange geometry! The universe may seem static on a small scale (like Earth) or an expanding sphere at a larger scale (inter-galactic), but at the universal scale something even weirder is happening. It may be more useful to think of the "expansion of the universe" as an illusion created by zooming into that singularity, which is itself fixed, even unchanging, but your inexorable motion "into" it makes it look like things are flying apart. (In this case, "you" is an astronomer looking at distant galaxies; you can't really notice this effect at human-scale, and apparently you can't even measure it at lower-than-human scale, which is why quantum gravity is ...difficult shall we say.)
We don't understand why expansion is occuring, so we can't say for certain. It would be a very long time in the future if that were to come to pass, and that's a whole lot of time for poorly-understood physics to happen in.
But yes, it is accellerating, and if it continues to do so, eventually it will overcome gravity. But like I said, this depends on an incomplete understanding of physics, and the current evidence suggests (inconclusively) that this outcome is unlikely. Check out dark energy if you want to learn more.
Sometimes a simple upvote just doesn’t seem enough. So here’s a heartfelt Thank You for this and your other explanations - I really appreciate your knowledgeable and thoughtful responses!
>>> Like this one, it’s not understood how it can exist.
I don't like that phrase. It suggests the possibility that this galaxy might not exist, that this could be observational error. I think it does exist. We understand exactly how it exists because we can observe it existing. The more accurate phrasing might be "it's not understood how it could have evolved so quickly".
This could absolutely be observation error. Messups in science happen all the time. You never take a single data point at face value without question, in any field. The spectrum might be polluted by another more distant object, the line matching might have been faked by some other intervening medium, the modelling for the lensing galaxy could be wrong. I agree, it looks good.
I think the phrase is fine since according to our best models of galaxy formation these galaxies should not be able to exist and yet they do. As such we don't understand how these galaxies can exist and need to do more research to come up with better models that can explain the existence of these galaxies.
Observational error is always a good speculation. It seems to be at the heart of most of these "impossible physics" stories.
Remember not long ago when neutrinos were thought to have been observed moving faster than the speed of light? Cold fusion?
Before people jump on the idea of re-evaluating Einstein's theories, it's always good to get more people looking at the data, independently verifying it, thinking about it. In a few months, it's likely that this blip will disappear like most others.
I find it funny when scientific articles (esp. pop astronomy) describe something as weird, bizarre, or extremely unlikely. We're reversing the effects of gravitational lensing on a galaxy at a distance that's a significant fraction of the radius of the observable universe.
Are astronomers that confident in their models that the inferred shape of this galaxy is bizarre? I'd love to have that level confidence in software.
That is the premise of the article. It is bizarre in relation to our models of the universe. We don't know if it is unusual in relation to the universe itself. As the article states:
>Clearly, the theoretical models are wrong, or at least (and more likely) incomplete. Obviously, there’s more to learn about galaxies that exist at the edge of the observable Universe.
I am reminded of that tale about how "Eureka!" is not exclamation of good science but instead "That's odd.". This article is saying "That's odd." in a way that signals we are on the verge of new scientific discovery.
We can more readily validate gravitational lensing than any early universe physics. So my guess would be that modeling the lensing is the easy part to validate :)
perhaps they look less chaotic because the rays at each point of the the ring when reconstituted was not emitted at the same time, so the picture we computed is a reconstitution of a large spread of time during which movement of the stars in the galaxy blurred substantially giving the impression of a more homogenous and orderly galaxy (a chaotic galaxy at astronomical shutter times might look orderly)
That article explains that the galaxies are only moving faster than light from our perspective since every part of space between us and it is expanding.
So, no it's not moving faster than light. The space between it and everything else is expanding.
I've always been puzzled by the estimated age of the universe at being 13 billion years. That's just the size of the observable universe, correct? Isn't there a future horizon beyond which light will not currently reach us?
No, 13 billion years is the age of the universe. The observable universe is a sphere with a diameter of ~93 billion light years (And is likely to only be a subset of the entire universe).
Whoa, that's crazy precise. They got it down to the tens of thousands?
If so, seems like they should write "13.700 billion" for the first part. I'm a little suspicious of this number as-is.
Looking for a source for those numbers, I found this[0]:
> While previous estimates were 13.7 billion years old, give or take 130,000 years, new predictions hone in with more precision- at around 13.77 billion years, plus or minus 40 million years.
Which is much less precise and feels a lot more believable.
Naive question here - is the 13bn years relative to the surface of the Earth? I assume this matters right? If we're in a bit of a gravity well wouldn't the vacuum of space experience this time a bit longer?
According to [1], the ratio is about 5.56E-10, so I guess this would contribute about a year to the age of the universe, so.. not that much. I guess I answered my own question.
However, this does pose an interesting question about the age of the universe in extreme gravity wells doesn't it? Or am I misunderstanding something?
Well, given that there is no universal clock and time is defined locally for each observer, including each particle, it would be more strictly accurate to say that "the matter which later formed our solar system has experienced 13 billion years of time" since the Big Bang
or maybe 13 billion years is from the frame of reference of the Cosmic Microwave Background? that would make more sense. I'm going to check again then edit this comment.
(i am not a physicist, not an authoritative source on this)
edit: so it turns out that the age of the universe is given from the frame of reference of the CMB rather than from Earth's frame of reference.:
> Measurements of the cosmic background radiation give the cooling time of the universe since the Big Bang
> Cosmic time, or cosmological time, is the time coordinate commonly used in the Big Bang models of physical cosmology.[1][2][3] Such time coordinate may be defined for a homogeneous, expanding universe so that the universe has the same density everywhere at each moment in time (the fact that this is possible means that the universe is, by definition, homogeneous). The clocks measuring cosmic time should move along the Hubble flow.
I have a question: Just over 20 years ago when the accepted view was that the expansion of the universe was slowing down, would you have backed that position with as much certainty as you are backing this one? That the universe is a mere 13.7 billion years old?
We cannot prove the absence of light in a place that is already so far away that it's light will never reach us. Do you agree? We can prove what we can observe, and from that proof we can make inferences about what we cannot observe.
The entire premise of dating our universe is based on its observed rate of expansion. This was accomplished by extrapolating data from observable light and tracing it back to the so called Big Bang.
I see a lot of problems with this one dimensional assumption, which to me seem really obvious.
First of all, let's assume that we actually got it right this time and accurately traced light back to the Big Bang - how can anyone be sure that it was the first and only Big Bang?
Pangea, the super continent, for instance - many may think of as a single place and time in history, but in fact it's more likely that many Pangea's have come and gone in various states as the planet roils on. There will likely be another in the far future.
Perhaps the Big Bang was merely a "localized" event and there are Big Bangs occuring in distant places whose light will never reach us. Perhaps we have gone through many Big Bang / Big Crunch cycles. We simply cannot prove it one way or the other, and so to take a strong position on this would be unscientific.
More food for thought - imagine that the universe has already been through a near infinite number of Big Bang / Big Crunch cycles, it begs the question, do we reset the clock every time or do we let it run?
In my opinion, currently accepted theory is akin to believing that the Earth is the center of the universe and the sun revolves around us. We were wrong about that too.
The problem here is that you are taking a simplified layman's description, making naive assumptions about it and then brazenly dismissing the whole of contemporary cosmology as if you have profound insights that went completely over the heads of some seriously smart physicists.
You then make an analogy about "Pangaea" as if you alone are the brilliant shining light of reason, but if you took just a small amount of time to read even Wikipedia you would find, for example, that several super-continents have formed and broken apart over the history of the Earth. The very first section of the Wikipedia article on Supercontinents lists eleven of them!
[https://en.wikipedia.org/wiki/Supercontinent#Supercontinents...]
I for one see a lot of problems with your one dimensional analysis and obvious lack of awareness on these topics. In my opinion, your currently insufficient knowledge is akin to believing that the Earth is flat because you can't personally see curvature on the horizon.
Seriously though, I recommend you take the time to read about 'the entire premise of dating our universe', all the many decades of development, criticisms, refinements and confirmations of the current best theory. You'll find that it's an amazing subject, that all of your concerns have been poured over for the past century in great detail, that many brilliant people have worked out fantastically brilliant methods for figuring this out... and then finally, maybe, you'll be ready to read about the various cyclic cosmological models.
I get where you're coming from but there is a general frustration out there about physics that a lot of nerds share. We need kicks as well as truth or the heart won't be in it. People invest a lot of energy into something if they feel they are involved with the general effort because it gives meaning and we enjoy that. Our lay ideas will be incorrect - but the urge to ask questions being stifled by a existing body of understanding we don't understand makes us apathetic and prone to leveling.
Somebody like Graham Hancock is actually delivering more people to the pipeline of scientific understanding than Richard Dawkins. We don't want to hear it but it's true. Similar things are true of WebMD and doctors, Elon Musk and space research. All the time the domain experts are shooting themselves in the head because the true opposition isn't a cruder wrong idea - it's apathy. Creationists at least give a shit about what version of events took place, the population that doesn't care is much larger. There is no critical mass of creationists that is going to undermine scientific research but the universities being defunded by an apathetic public turning hostile because they believe we're a waste of dollars - that is only a matter of time.
Science and expertise are an ecology - the people on the edge only exist because of a bigger enterprise capable of providing support. So it's not great that the stories the general public and scientists tell themselves are starting to sound like a protagonist antagonist relationship.
This is a really great point and I believe it is (at least partially) driving the anti-science rhetoric that seems to be metastasizing. When a topic is inaccessible to the general public, and only experts in the field can understand it and hold a monopoly on information, then you inevitably start to see pushback against it.
That being said however, making certain fields more accessible to the populace often comes with the price of a false sense of understanding. You see this a lot in medicine with WedMD, where heuristics that largely ignore the deeper pathophysiology have empowered some to believe they are more knowledgeable than their doctors.
This must be doubly true for the more abstract forms of physics - where any simplified analogy is going to give rise to false notions via extrapolation. I think there has to be some sort of balance between the two
Here is a example solution for the WebMD problem - I think it's about empowerment and tribalism - in positive senses of those words.
In Japan there exists an institution called Ningen Dock. Almost nobody in the West has heard of it outside of Randox Research which is astonishing as most Japanese people visit it once a year. I believe this is a psycho-social-medical institution. It purports to be a medical institution but it's something more.
Youtubers describe their experiences of Ningen Dock if you're curious.
It works like this - most people in Japan visit the 'dock' - a metaphor from shipyards. There is a brain dock, a heart dock, a lung dock and so on. Every major hospital has this department where the patient is checked head to foot once a year. Here is the important part. They are given a grade sheet - the sort a schoolteacher awards students. Here you see your kidney was given a B-, a liver a C-. These are hints about your lifestyle choices. Perhaps you should feel bad. In one more year there will exist another Ningen Dock. I believe this institution is responsible for a superior resilience against lifestyle disease that overwhelms healthcare in other developed states. It's preventative healthcare taken seriously instead of mouthing platitudes about lifestyle choices while back in Western reality you're never far from a fatty who knows they're making mistakes. It could be you or me!
Now Sir Gwern and other analytical thinkers of HN will have spotted the problem. False positives leading to needless surgeries. This is how Western doctors are trained to think and they find Ningen Dock incomprehensible. If though we assume Japanese MDs are not idiots and positive externalities exist from the Ningen Dock then it could easily be paying for itself. The hypochondriacs don't menace the healthcare system. Their energy is redirected to superior choices. For everybody the locus goes away from the doctor and analysis and toward being responsible on your health to the best of your ability - guided by timely medical advice. The system also develops a giant database of longitudinal information which can be used to spot health patterns across populations - to enhance targeting of the analytical process. I'm sure there are lots of other tangible advantages I haven't mentioned.
So that is patient empowerment - but the tribalism aspect is important too. The system is saying to the people - we're on your side, we're on the same team, we are in your corner, we are working for you. A lot of people don't feel that way and it needs to be said. Think of the rise of ASMR videos. Hundreds of millions of people watching supposed doctors treating them. There's something there. Just the insistent affirmation would be positive for mental health.
>Somebody like Graham Hancock is actually delivering more people to the pipeline of scientific understanding than Richard Dawkins. We don't want to hear it but it's true.
This is a pretty bold statement. You are arguing that psuedoscience is resulting more people being scientific than actual science is?
Such an extraordinary claim needs some significant evidence behind it.
Is it really an extraordinary claim? In your own experience have you never settled for a poorer model of something, a lower resolution because you feel either you didn't have the cognitive resources to get there or you felt unmotivated? When the topic becomes more complex - this happens to more and more people.
If you have a compelling story you may be motivated to sip on the subject. After a time you probably shrug off the old understanding and get to something more robust and probably more scientific.
I acknowledge some people will head into annoying dead ends - but you have to respond to the question of whether you prefer some people to be wrong and some people get to better places - or if you want most of those people to have checked out altogether. After all it seems to me that longer people ponder on it the more it is they converge on something - often something true or useful. Those are your choices. If you want to call me a liar then I suggest taking this seriously means getting a whole lot better at telling stories that go in the direction you approve of instead of what to the inside looks like doubling down on accuracy but to the outside looks like obfuscation.
Practical test - A lot of scientists are concerned about CO2 emissions and climate change. A lot of the population thinks they're full of shit because of politics. Some people have noticed though - that there doesn't exist a conflict of interests in getting improved technologies that happen to reduce CO2 emissions. Just as many right wingers are going to buy passive houses, closed loop energy, solar panels, Teslas as left wingers. Instead of perusing this thought a lot of people veer off into sermonizing on the topic - but I have to wonder why anybody gives a shit about the means when it seems like pushing on one lever gets instant blowback and pushing on the technology lever wins friends every time. It's almost as if all these groups have ulterior motives different to the public facing ones.
I don't quite understand how we go from "Ancient aliens" to "real science" - I've never spoken to someone who believed in that stuff as the jumping off point that later went on to being curious about actual science when they weren't previously.
>Just as many right wingers are going to buy passive houses, closed loop energy, solar panels, Teslas as left wingers.
I also don't know that this is actually true. I as only able to find "what do you want to buy" polling for cars, but in a study surveying actual solar usage, it's 34% democrat and 20% republican.
But I think this is also a false premise - that somehow conspiracy theory nuts have the same impact on public perception of science as one of the most public scientific issues with consensus from tens of thousands of scientists including basically 100% of the leading experts in the field. And the fact that there are long term economic advantages for things like solar, etc. that don't take into account at all whether or not you believe in man made climate change.
True - but most people never become scientists - not even amateurs - but there exists a flourishing industry of science books for people who are a bit science curious. Scott Alexander used to be a giant Hancock fan - anecdotal I know but he later realized it was sort of bullshit - but still was interested in deep archaeology. I'll call that a win.
On the stats - that's a rabbit hole I won't go down today but every time I've seen people talk about alternatives to the system the left and right become like a long married couple ending each other's sentences.
>And the fact that there are long term economic advantages for things like solar, etc. that don't take into account at all whether or not you believe in man made climate change.
Sure.
> But I think this is also a false premise - that somehow conspiracy theory nuts have the same impact on public perception of science as one of the most public scientific issues with consensus from tens of thousands of scientists including basically 100% of the leading experts in the field.
There I think you're making a mistake. Literary people think Proust is awesome. A lot of people have read Dan Brown. Who is having more impact? You're making a face now - I can see through the interneticals.
This is just pedantry. Don't get me wrong, these are interesting questions, questions that should be asked and should be thought about, even if the answers are likely unknowable. But taking issue with the age of the universe because we don't know what existed before isn't useful.
Age is a relative thing. I say I'm xx years old based on the date of my birth. But I existed as a fetus before then. I existed as an ovum before that. I existed as stardust for billions of years before that. Perhaps I can mull over what it means to exist, and when "me" came to be, but when I have to enter my age while filling out some form I'm not going to write a philosophy essay. For practical purposes I am xx years old, and for practical purposes the universe is 13.7 billion years old.
I think you are generally critiquing assumptions that most astrophysicists are not making. Most Theorists would not claim with confidence that the big bang was the first or only one, or that future big bangs are not possible. I think your criticism is more valid for the way the history of the universe is portrayed in news articles and high school text books.
The term "multiverse" is used to describe the collection of multiple universes.Some have speculated that time has no direction in the multiverse and that time in each universe may be different. If our universe is cyclic, it makes sense to reset the clock because it may have run in a different direction last time or next time.
> Perhaps the Big Bang was merely a "localized" event and there are Big Bangs occuring in distant places whose light will never reach us. Perhaps we have gone through many Big Bang / Big Crunch cycles.
This was always my view of the state of the universe from childhood onward. The Void of space is infinite, and within that Void our universe could be one of an infinite number of other universes that we will never know about because they are so far outside our ability to observe them. Perhaps there is as as much relative distance between universes in the Void as there is between galaxies in our own universe.
This concept is the only way I've ever been able to accept that our own universe has a measurable size.
I don't think your childhood view holds up with contemporary views. My understanding is that 3 dimensional space, as well as time are properties of our local universe. There is no space outside the big bang and between universes if multiple exist
That's exactly what I have such a hard time wrapping my head around: The concept that there is not even a Void outside of the borders of our own universe, that existence itself doesn't, well, exist. The fact that "space" (as we define it) is finite just feels so wrong, so impossible.
> Just over 20 years ago when the accepted view was that the expansion of the universe was slowing down
Was it ever a mainstream view? I thought it was just a conjecture, leading to the 'big crush', and was disproven long ago, way more than 2 decades ago.
> The entire premise of dating our universe is based on its observed rate of expansion
Also there's the cosmic microwave background radiation. We have mapped it, and this has also allowed us to corroborate when the universe has formed, what temperature it had, and when large scale structures appeared.
There's probably other sources that allows us to estimate the age of the universe.
> how can anyone be sure that it was the first and only Big Bang?
We can't. But it is an irrelevant conjecture outside of philosophy, we can't observe anything before the big bang.
> but in fact it's more likely that many Pangea's have come and gone in various states as the planet roils on
Sure, but that's a planet. We can't extrapolate much from that and apply to the universe at large.
> Perhaps the Big Bang was merely a "localized" event and there are Big Bangs occuring in distant places whose light will never reach us
> imagine that the universe has already been through a near infinite number of Big Bang / Big Crunch cycles
Unless the rate of expansion starts to slow down or we have indication that it will ever reverse, there's no big crunch. The rate of expansion is increasing
> currently accepted theory is akin to believing that the Earth is the center of the universe and the sun revolves around us
Not really. You are dismissing generations of people dedicated to the study of these things. We have a pretty good idea of what's going on based on the scientific method, not conjectures from single individuals.
There are things that we don't know yet. On a macroscopic scale, dark matter. Things don't really behave as they should based on observations, so this is why we have dark matter as a hypothesis. There could be another mechanism, research is ongoing. But as far as the macro universe goes, that's the major thing we don't understand yet.
Most discoveries will likely come from a better understanding of the 'building blocks', of which quantum physics is at the forefront.
There's probably much more we don't know yet. But the age of the universe, as we observe it, is not among them.
>Unless the rate of expansion starts to slow down or we have indication that it will ever reverse, there's no big crunch. The rate of expansion is increasing
Unless space wraps around like a globe and we'll all meet at the "south pole" (with the big bang being the "north pole") or something to that effect. Which is itself wild, unfalsifiable conjecture, but there are other ways for a Big Crunch to happen other than the expansion of space slowing down or reversing
I completely agree. Apologies if my comment above rubbed anyone the wrong way. The point you just made was my overall point. Our concept of time is confined to our current existence / cycle - that's what I meant by the sun revolving around the Earth comment, but others were correct when they responded that as a current metric that's not really useful.
> "Unless the rate of expansion starts to slow down or we have indication that it will ever reverse, there's no big crunch. The rate of expansion is increasing"
What if it is increasing because it is falling towards a great mass on the other side of the universe? That would still count as a big crunch in my opinion.
> "Was it ever a mainstream view? I thought it was just a conjecture, leading to the 'big crush', and was disproven long ago, way more than 2 decades ago."
How would one disprove the ultimate fate of the universe?
Sorry to bikeshed, but I was struck by the word "likely" in your parenthetical. Are there models of the universe that predict our observable universe is _not_ a subset of the entire universe? How would one describe cosmological expansion in such a model?
It depends on the size and topology of the entire universe. It's possible the universe is smaller and sort of wraps around: literally, objects that appear far away are just past images of the back of objects that are closer to us.
More boringly, measurements of the curvature of the universe mean this is probably not the case.
The Cosmic Microwave Background Radiation is a pretty uniform field that exists over the entirety of the observable universe. It was created in the earliest days in our universe. The fact that it exists everywhere we look with high regularity lets us guess that we're only a subset of a larger universe. There are many theories about the unobservable parts of the universe but these are impossible to test with any foreseeable technology that doesn't fundamentally break our understanding of physics.
One analogy I've heard: Imagine the big bang split into 4 spheres and they accelerated away from each other. Because they'll all be expanding and accelerating, there could be 4 equally sized spheres of stuff just like our own, but it would be impossible for us to observe them. Change the number 4 to 2 or 1000 or n. We really would have no idea.
A testable hypothesis is a strong standard in science. Most scientists don't worry about things that cannot or more importantly, will probably never be testable. They can be fun to think about but that's pretty much it.
Some weird geometry where space is curved into a four dimensional sphere. The sphere gets bigger, adding space between all the points. If the sphere is exactly the size of the observable universe, then the observable universe and universe would be the same thing.
The universe has been expanding ever since the Big Bang. Things that are very far away are moving away from us at speeds "faster" than light. No, they're not violating the cosmic speed limit. The fabric of spacetime itself is expanding everywhere, and that makes objects at very large distances apart get even further apart faster than a lightspeed traveler could move them.
When i was a kid, we used to dream about the "ping-pong" machine of light. Basically- the light bending of the black holes allowed for images of the sky to be stored, distorted and bounced around to almost noise - of skys objects in diffrent times..
Drive it through a simulation, and you could see a nova light up, reflected back from the ping-pong machine over the aeons..
There was this nasa book, "Cycles of fire" we sat and daydreamed about..
It bugs me that no one realizes that the “end” refers not to the “edge” but at the closing of the universe - the restaurant is in a frozen time bubble that can watch the universe end.
Our language tenses weren't really designed for distant space phenomena. Should we say Betelgeuse is a red supergiant or was a red supergiant? When we look at the sky it exists "now" for us and there's no way to know if it's exploded since the light that we're seeing now left its surface. And even if we talk about the light that's leaving it in our "now" that's kind of vague since there's no real universal common clock.
Strictly speaking our observations are not continuous. We pointed a large array at it and then the array probably went on to other work and looked elsewhere - so technically “was” is more correct, since we do not know what it “is” doing, rather only what it appeared to be doing.
Either way it’s a pretty uninteresting difference in tense.
I find it a very interesting difference, because it and other fuzzy writing like it has a devastating impact on science literacy, leading to lack of comprehension of concepts. Weak thinking on science in turn contributes to many of the problems we face as societies today.
> The thing is, where they found it is not normal: The light we see from it left the galaxy 12.4 billion years ago, meaning we’re seeing it as it was when the Universe itself was only 1.4 billion years old!
It's not confusing at all. It's because the long-worshipped, conventional big bang theory is wrong. The universe doesn't have a beginning or end. It's eternal. The original sin of that theory is that it's tainted with forced space for a deity belief at the center and always has been. The universe cycles unevenly through phases of motion, it doesn't magically start from nothing and then 'die.' The conventional big bang theory is as bad as any other children's tale going, it's up there with Santa Claus.
We're going to find a lot more supposed abnormalities like this over time. They're not abnormalities, it's the entrenched incorrect theories that are the problem.
The universe (everything that exists) is drastically larger than we already think it is. Humans are arrogant, we didn't realize the extent of the micro world, and the same exact mistake is being made at the macro scale. What they think is a singular ~14-15 billion year old universe, is nothing more than one collection of galaxies, there are many more like it nearby (many as in trillions and trillions). The micro world was far smaller than we imagined; the macro world is far larger than we're imagining. It's the same mental mistake playing out, caused by the same arrogance. What's beyond the 'universe' that we can see so far? More massive collections of galaxies, similar to the one we inhabit that we mistakenly call the universe.
What the universe really is, is a simulation. We are trapped in it.
"Lightspeed limit": this is because the simulation has a finite computing power. You can either move in time normally, or you can move in space. If you go to the max allowed speed, there's no processing left over to simulate time, therefore time stops for that entity. At intermediate speeds, slow down time accordingly.
"Planck length": resolution of the simulation. It's discrete, and you can't go any smaller.
"Heisenberg uncertainty principle": another simulation optimization. Instead of simulating all particles, just use a probabilistic function. You actually don't have to simulate it, just the macroscopic effects, unless there's an observation. In which case you can compute either the position or speed of the particle. See also: atom orbitals
"Superluminal" expansion: it's just so we don't try to get to other galaxies, which are only being simulated in a macro scale. This was left by the developer to turn the 'lightspeed bug' into a feature. Also closes bug UNIVERSE-001 where the background radiation was still visible, but other galaxies visibility was off due to performance concerns. Now they can be enabled.
"Dark matter": other civilization experiments that we don't have permissions to see. Still there and interacting with matter. Bug is still in the backlog.
Any habitual stoner could tell you that. Once your blood THC levels are high enough, the secrets of the universe will unfold before you. And it's 100% certain, because I mean, you totally observed it, Man!
https://orbitalindex.com/archive/2020-07-08-Issue-72/#more-o...