
First Successful Test of General Relativity Near Supermassive Black Hole - SiempreViernes
https://www.eso.org/public/unitedkingdom/news/eso1825/?lang
======
magduf
I'm always a little disappointed when these experiments are unable to disprove
General Relativity. I keep hoping that they'll discover something slightly
wrong about it, which will quickly lead to us figuring out how to develop a
practical warp drive which doesn't require negative or nearly infinite energy.

~~~
macspoofing
I never thought of c being a real problem to space travel. Sure, on the
timescale of our lives c is sloooow because moving between stars automatically
necessitates a multi-generational approach and/or huge amount of resources.
The big problem however, is that we have no place to go. We are tied to earth.
Our bodies are made for a specific gravity constant, specific distance from a
specific star, specific atmospheric mix of gases, a pre-existing DNA-based
fauna and flora, etc. Quite simply, when it comes to colonization: there's no
place like home. Every other place sucks for our bodies.

Once we achieve the singularity(tm) and upload our consciousness (or get
replaced by AI), we can turn down the clock speed on the matrix (say turn
1,000,000 real years into 1 matrix year), and like magic c stops being a
practical limitation. Sending message (or travelling) from one side of the
galaxy to another would take a 'matrix month' .. turn the clock down even
further and you can make galactic communication instantaneous.

~~~
rwcarlsen
You could actually reach almost anywhere in the galaxy within a single human
lifetime (the traveler's lifetime that is) using only 1-G constant
acceleration:
[https://en.wikipedia.org/wiki/Space_travel_using_constant_ac...](https://en.wikipedia.org/wiki/Space_travel_using_constant_acceleration)

No FTL required. We just need to figure out how to use propellant efficiently
enough among a few other slightly difficult challenges.

~~~
magduf
The problem with this is that, by the time you get anywhere, a ridiculous
amount of time has passed back on Earth, and also on the destination planet
(since the reference frame for the other planet is very close to Earth's). So
if you travel around to hundreds of planets, pretty soon all the stars have
gone nova and you're nearing the heat-death of the universe, even though you
may not have aged much.

~~~
MLij
I never really understand this. From the Wikipedia link: "At a constant
acceleration of 1 g, a rocket could travel the diameter of our galaxy in about
12 years ship time, and about 113,000 years planetary time." But that's from
the frame of reference of planet earth. If you are on the spaceship, earth
will be moving away from you so time on earth will appear to be slower than
your time. So if you come back to earth you will appear younger than should be
to the people that stayed, but to you people that stayed will appear younger
than should be. Frames of reference are equivalent, aren't they? Maybe I'm
rambling, but I can't figure this out.

~~~
rwcarlsen
[https://en.wikipedia.org/wiki/Twin_paradox#Resolution_of_the...](https://en.wikipedia.org/wiki/Twin_paradox#Resolution_of_the_paradox_in_special_relativity)

~~~
rajacombinator
Great article!

------
delecti
Gravitational lensing has to be the coolest thing ever. That we can use a
black hole as a telescope to see such incredibly distant bodies just leaves me
with a childlike giddiness whenever I think about it. What's almost as
incredible to me is that someone figured it out before we could prove it.

~~~
nine_k
It's also nice that we apparently can "take" a black hole millions of times as
massive as our own system, and use it for our purposes.

It's likely the single biggest part of a scientific instrument. (Not of an
industrial tool... yet.)

~~~
canhascodez
There's not really any materials or conditions beyond one's immediate locality
that would be worth seeking out in space. Interstellar communication is going
to be limited at best, interstellar industry or trade may never be practical,
and even if one is willing to accept the idea that there is some purpose for
which a black hole is useful, I would still be skeptical that a _supermassive_
black hole would be of more use than a smaller one.

~~~
brogrammer5
I agree. I don't think the aeroplanes will ever been able to achieve lift. I'm
skeptical of anyone who attempts anything that hasn't been done before.

~~~
delecti
New revolutions in science have tended to be less "we were totally wrong" and
more "in extreme cases things don't quite fit the models". It's conceivable
that FTL communication and travel aren't as impossible as we currently think,
but that would require that things we've demonstrated fairly well are
completely wrong. The same wasn't true with heavier than air flight, which (as
the other comment notes) we had proof of it being possible (in birds). We knew
it was possible in theory, but figuring out how to actually work out the
mechanics of the process were the sticking points.

[https://chem.tufts.edu/answersinscience/relativityofwrong.ht...](https://chem.tufts.edu/answersinscience/relativityofwrong.htm)

~~~
HeadsUpHigh
There are huge parts of physics that remain a mystery( dark matter, dark
energy, the big bang, like how on Earth does inflation make sense, a ton of
crazy particle physics that go completely over my head). And the funny part is
that a lot of these can't be really fit into our current models in a
meaningful way. So until we deal with all those I still have hope for an FTL
drive.

~~~
canhascodez
Physics is very difficult, and magical thinking is much easier and more fun.
Relativity is a description of the geometry of the universe, and any
subsequent theory will need to explain the same observations. These
observations both prohibit any form of FTL, and suggest that a universe with
FTL would almost certainly contain causality violations. The hope that down
will someday become up is ill-founded, and the effects of this would not be
what you would want.

------
_bxg1
I always hope the images in these articles will be real and not artists'
impressions, but they never are

~~~
magicalhippo
Until we sent a probe, this[1] was the best image we had of Pluto, taken by
the Hubble space telescope.

Pluto has a radius of 1188 km. The supermassive black hole at the center of
our galaxy[2] has a Schwarzschild radius of about 1e7 km, so roughly 10000x
larger than Pluto.

However it's also roughly 50000000x further away than Pluto... which is why it
remains a mysterious blob until the Event Horizon Telescope[3] delivers.

[1]:
[http://hubblesite.org/image/2686/news_release/2010-06](http://hubblesite.org/image/2686/news_release/2010-06)

[2]:
[https://en.wikipedia.org/wiki/Sagittarius_A*](https://en.wikipedia.org/wiki/Sagittarius_A*)

[3]: [https://eventhorizontelescope.org/](https://eventhorizontelescope.org/)

~~~
SketchySeaBeast
Given the sorts of scales, would there be a hard limit to what we can see?
Where we get to such a distance the dispersion of photons from the source
would never allow us to see it? Or do we just have to build bigger and bigger
photon collectors?

~~~
dsr_
[https://en.wikipedia.org/wiki/Diffraction-
limited_system](https://en.wikipedia.org/wiki/Diffraction-limited_system)

The first problem is that we are limited to observing that photons that
originate at the source; there's no way for us to bounce some small-wavelength
photons off of our target and collect them.

So we could do long-baseline interferometry, instead. You need to spread your
sensors over a large area and keep synchronized timing.

[https://en.wikipedia.org/wiki/Radio_telescope#Radio_interfer...](https://en.wikipedia.org/wiki/Radio_telescope#Radio_interferometry)

Naturally, you can build bigger systems in space.
[https://en.wikipedia.org/wiki/Space_Interferometry_Mission#O...](https://en.wikipedia.org/wiki/Space_Interferometry_Mission#Optical_interferometry)

If we sent out satellite telescope stations to orbit the sun, with really good
communications and clocks, we might be able to create a virtual lens that's
really big:

[https://en.wikipedia.org/wiki/Laser_Interferometer_Space_Ant...](https://en.wikipedia.org/wiki/Laser_Interferometer_Space_Antenna)

------
lawlessone
> GRAVITY creates such sharp images that it can reveal the motion of the star
> from night to night as it passes close to the black hole — 26 000 light-
> years from Earth.

Amazing.

------
oblib
I have to admit that when I read this kind of stuff I am always amazed with
those who truly grasp it. I feel the same when listening to great musicians
and viewing great art.

------
eigenloss
"More than one hundred years after he published his paper setting out the
equations of general relativity, Einstein has been proved right once more — in
a much more extreme laboratory than he could have possibly imagined!"

This sounds somewhat like an insult to Einstein's imagination.

~~~
laretluval
Up to his death Einstein denied that black holes could physically form.

~~~
ars
And he is right. Time dilation means it's impossible for them to form. (From
the POV of me, here on earth.)

~~~
codethief
Considering astrophysical evidence to the contrary as well as multiple
simplifications(∆) underlying your argument, I'd say he was probably wrong.

∆) (Some of) the assumptions underlying your argument are the following:

Assumption 1: We're observers at infinity, observing time as given by the
usual Schwarzschild/Kerr coordinate t (let's focus on Schwarzschild for
simplicity). Yes, the argument in favor of this is that such observers observe
Schwarzschild spacetime to be flat at infinity (which is more or less what we
see) but there are certainly other[1] asymptotically flat foliations of
Schwarzschild spacetime which don't have a coordinate singularity at the
horizon and thus don't exhibit the behavior you describe. I have yet to see a
convincing argument for why we, as observers, couldn't perceive _any_ of these
other foliations of Schwarzschild spacetime and for why we _definitely_
wouldn't live to see someone else cross the event horizon. (I mean, the fact
that this doesn't work in the usual Schwarzschild coordinates is really a
consequence of their singular behavior at the horizon, so should be resolved
by _any_ smooth/non-singular choice of coordinates—of which there are
infinitely many.)

Assumption 2: You're talking about a static black hole solution (or a simple
spherical shell collapsing) while realistic scenarios of black hole formation
are an entirely different beast.

Assumption 3: You cannot superpose / easily glue together solutions of
Einstein's field equations. So I'd be at least careful making a statement
about us, here on Earth, when it comes to a distant black hole.

[1]
[https://en.m.wikipedia.org/wiki/Gullstrand–Painlevé_coordina...](https://en.m.wikipedia.org/wiki/Gullstrand–Painlevé_coordinates)

~~~
oldandtired
From our perspective and according to the general consensus idea that the
universe is of finite age and fully in accordance with all black hole models
and general relativity, blacks holes cannot exist in our universe. That does
not mean what we have observed is not interesting, It is, but we don't know
what it is, though we know it is not the "black hole" of theory.

There are no circumstance under the prevailing theories for which any kind of
"black hole" can come into existence anywhere in our universe. Black holes are
wonderful "flights of fancy" just like the Stargate and the Ancients
Hyperdrive and just like the Star Trek Warp Drive.

"Black Holes" require certain assumptions for their formation in the
theoretical sense and since those assumptions are not found in our universe,
all models of "black holes" have an automatic failure point. All discussions
about "black holes" being real, ignore those discrepancies and assume that
they can exist. If you fail to agree with the "reality" of "black hole"
formation, you become persona non grata.

The problem with the "black hole reality" assumption is that we cut off entire
streams of investigation into what the observed phenomena may be. We are stuck
in a very little corner of the universe and we cannot see many things up
close. Our model assumptions colour our understanding of what we see. There
are many of our observations that are anomalous to the prevailing theories
that are considered "correct". Yet, if you (as an observational or
experimental scientist) raise questions in relation to the consensus models,
you will be quickly put in your place.

It is quite interesting that for a supposedly advanced civilisation, much of
our technology and scientific endeavour is ruled by dogma. This does not lead
to the advancement of our understanding of the universe around us. Just as
other people have said before me and as I have said before - "There are no
silly or stupid questions".

Science is one useful tool we have for investigation of the universe around
us. But the outcomes we find using it in our investigations of the universe
around us are predicated on the basic assumptions we bring to the table in
those investigations. It is one tool among many that we have and when people
use it as the only tool that has meaning, they have moved it from being a
useful tool to being a dogmatic tool. they have made science into a religion.

~~~
pdonis
_> There are no circumstance under the prevailing theories for which any kind
of "black hole" can come into existence anywhere in our universe_

You are peddling misinformation here. You really need to get a correct
understanding of black holes.

~~~
oldandtired
I have been occupied with other things and only now have the time to respond.

Every model of "black hole" has as a fundamental underpinning which is time
dilation due to increasing gravity (by whatever definition of gravity you may
use). At whichever "event horizon" you may choose (in discussions with
physicists, they have claimed a minimum of three different event horizons),
time at the event horizon as observed from the universe at large stops. The
underpinnings of "black holes" requires an eternal universe, no "big bang", no
finite age. Formation as we see stops and can never proceed in finite time. We
live in a small isolated part of our galaxy and we are unable to observe
clearly many sections of our own galaxy. We rely on proxies and a belief that
these proxies are adequate to match to the models and theories that are
considered to be correct by consensus.

If you think about "black hole" formation as described by the various models
in use, there are a number of assumptions made that don't actually match what
see in our observable universe or in any practical experiments we do.

I am no mathematician or theoretical physicist, but every source of
mathematics that I have studied and am continuing to study makes it quite
clear that our mathematics is approximate in its mapping to reality. There is
nothing wrong with this technique, but it does mean that one has to take what
results we get with a grain of salt when comparing to the actual universe
around us.

I find that when any of the many mathematical models in use today is declared
as "reality", then I see this as the peddling of misinformation. Mathematics
can and does provide us with a tool that is useful in describing what we see
around us. But it is limited and always has its failure points. It is
interesting that I have had this discussion about disagreeing with the
consensus view with someone (a physicist) who argue for it, yet they
themselves hold a particular non-consensus view over other matters relating to
cosmology and could not see the extended possibilities in looking at different
potential models and theories.

The simple point is that the mathematical models and theories are possible
maps of the territory and are not the actual territory itself. It doesn't
matter how detailed that map appears to be, it is still missing a great deal
of the detail of territory itself. When it is used to decry alternative models
because they are different, without actually testing those models for any kind
of veracity, then we have a problem.

The simple fact is, we actually have little understanding of the universe
about us. When we find discrepancies or phenomena that don't match the current
models, we should be big enough to allow people to investigate alternatives
freely without treating them as pariahs and heretics. It may well be that
those alternatives have no veracity, but then again, they may be the start of
a new outlook and understanding of the universe about us.

It is an unfortunate fact of life that people who disagree with the consensus
view will be treated badly. This is a function of what it is to be human.

~~~
pdonis
_> in discussions with physicists, they have claimed a minimum of three
different event horizons_

Huh? Where are you getting this from?

 _> time at the event horizon as observed from the universe at large stops._

Nope. The event horizon is a null surface--it is "made" of outgoing light
rays. The concept of "time" does not apply to light rays.

 _> The underpinnings of "black holes" requires an eternal universe_

No, they don't. An "eternal" black hole is an idealization, but a real black
hole does not have to be exactly the same as the idealized model. I mentioned
numerical simulations in another post down-thread; any realistic black hole
cannot be exactly described by closed form equations, it needs to be simulated
numerically. Numerical simulations make predictions that match what we see,
and show how realistic black holes can form by gravitational collapse of stars
and star systems.

 _> If you think about "black hole" formation as described by the various
models in use, there are a number of assumptions made that don't actually
match what see in our observable universe or in any practical experiments we
do._

I don't know what assumptions you're talking about.

 _> When we find discrepancies or phenomena that don't match the current
models_

I don't know what discrepancies you're talking about as far as black holes are
concerned.

 _> It is an unfortunate fact of life that people who disagree with the
consensus view will be treated badly._

You can't effectively disagree with the consensus view if you don't understand
it. You clearly don't understand the consensus view of black holes. I am
simply trying to point out incorrect things you are saying about that view.

~~~
oldandtired
> Huh? Where are you getting this from?

From the physicists themselves. Public discussions on their respective blogs.

>Nope. The event horizon is a null surface--it is "made" of outgoing light
rays. The concept of "time" does not apply to light rays.

Are you then saying that all the physicists who say time stops here as viewed
from outside are wrong?

> > The underpinnings of "black holes" requires an eternal universe

> No, they don't. An "eternal" black hole is an idealization, but a real black
> hole does not have to be exactly the same as the idealized model. I
> mentioned numerical simulations in another post down-thread; any realistic
> black hole cannot be exactly described by closed form equations, it needs to
> be simulated numerically. Numerical simulations make predictions that match
> what we see, and show how realistic black holes can form by gravitational
> collapse of stars and star systems.

The theoretical basis for "black holes" is an eternal universe with a single
mass in it. There are many things that can be numerically simulated. However,
one must be very careful what you are simulating and on what basis the
simulation exists. The "black hole" is a solution from a specific model and
that model does not match the real universe as we observe it.

I have no issue with there being large gravitational entities. i do however
have an issue with the declarations that said entities are "black holes". We
do not know what they are. You cannot in any way "prove" that they are "black
holes", no matter what level of consensus you display. We observe by proxy, we
are at this point unable to directly test what we see.

All one can say is that there is a model that is believed to be appropriate to
explain the phenomena observed.

I'll put it this way by example. We observed an entity that we call and
electron that has various observable attributes and we use a variety of models
to describe theoretically that entity. Are those models correct. Well, no.
They are what we use to try and predict further tests and outcomes that we
expect to find. We get some approximate closeness and then move forward. At no
point, are the models "fully correct" or "truth", there are still anomalies
found between theory and experimentation.

When we forget that our models and theories are only approximations to reality
and fall into the trap that they are reality itself, then we will become
incapable of actually advancing our understanding.

> I don't know what assumptions you're talking about.

Single mass existing only, asymptotically flat universe are just two of the
fundamental assuptions required.

> I don't know what discrepancies you're talking about as far as black holes
> are concerned.

We are not in a position to directly observe any such entity. The number of
times that scientists have declared that we have now seen for the first time a
"black hole" over the last how many decades. that alone says that each
previous declaration has been a furphy.

> You can't effectively disagree with the consensus view if you don't
> understand it. You clearly don't understand the consensus view of black
> holes. I am simply trying to point out incorrect things you are saying about
> that view.

When simple questions are raised against the model and are not answered by
those who lead the charge for the model and when their responses amount to
"you don't understand the model, so go away", then you can quite rightly take
the view that they themselves don't have a clue about what they are agreeing
with. I have yet to see a clear exposition of why such entities such as "black
holes" should exist in our universe and answer the various simple questions
that arise in opposition.

If such an explanation was to be given in a logically clear manner, then yes,
we could then put "black holes" back on the table.

~~~
pdonis
I have been tied up myself and am only now able to respond.

 _> From the physicists themselves. Public discussions on their respective
blogs._

Physicists will say all kinds of things in a popular forum. Do you have any
references to textbooks or peer-reviewed paper?

Even on physicists' blogs, I have never seen any reference to three different
event horizons, so if you have any specific ones you can point to, it would
really help me to understand what you are talking about.

 _> Are you then saying that all the physicists who say time stops here as
viewed from outside are wrong?_

If any of them actually are saying that, yes, they're wrong. But I doubt
you'll be able to find any textbooks or peer-reviewed papers that say that. I
don't care what pop science sources say; they're not valid sources for
learning the actual science.

 _> The theoretical basis for "black holes" is an eternal universe with a
single mass in it._

No, it isn't. You are confusing an idealized model used for pedagogy with
actual models used to make predictions about actual objects observed by
astronomers.

 _> I have no issue with there being large gravitational entities. i do
however have an issue with the declarations that said entities are "black
holes"._

If you want to be very careful, you could say that black holes are the only
entities consistent with our current theories that these "large gravitational
entities" could be. It is true that our current theories are incomplete, and
it could be true that a more complete theory would tell us that these entities
are not anything like our current model of black holes. But even if that
happens, it won't be for any of the reasons you are giving.

 _> Single mass existing only, asymptotically flat universe are just two of
the fundamental assuptions required._

Again, you are mistaking an idealized model used for pedagogy with the real
models used to make predictions about real observations. The latter do not
depend on any such assumptions for the universe as a whole. They only require
that a suitable region of spacetime around the object being studied contains
only that object (or objects--models of this sort are used to make predictions
about multi-object systems such as binary pulsars, for example, as well as
black holes) and becomes flat enough at its boundary for asymptotic flatness
in the model to be a reasonable approximation. These conditions are certainly
met by the objects and systems to which the real models in question are
applied.

------
rdiddly
It appears astronomy articles have completely given up reminding us that the
phenomena being observed at x light-years away, happened x years ago (26,000
in this case), so I'll do it. (Maybe it's more soothing to our human egos to
feel like it's "happening right before our eyes" but I liked it better when
talk of space made me feel small and insignificant.)

For example it's good for the ol' ego (and a fun flight of fancy back into the
past) to be reminded that when this star was actually passing near the black
hole, back here on Earth homo sapiens was enjoying his "cave paintings" phase,
using stone tools (maybe juuust starting to get into metallurgy in some
areas), and it was the peak of the last glacial maximum, which would've been
quite noticeable while hunting wooly mammoths with spears in the northern
latitudes.

~~~
EpicEng
Honestly, it would be pretty annoying for anyone even remotely familiar with
high school level physics to he constantly reminded that a light year is the
distance light travels in a year.

~~~
rdiddly
That's presumably why they don't do it, but you're being hyperbolic. An 8th
grader is remotely familiar with high school physics. The janitor of the high
school physics classroom is remotely familiar with high school physics. Yet
they probably could both stand to be reminded a time or two what a light-year
is.

~~~
EpicEng
>Yet they probably could both stand to be reminded a time or two what a light-
year is

Ok, but you said:

>It appears astronomy articles have completely given up reminding us that the
phenomena being observed at x light-years away

So how should the author decide on how often to remind their presumably
educated audience (this is eso.org after all, not some pop-culture magazine)
of the basic of light travel? Once every five articles? Ten? Or maybe they
just assume as I do that anyone reading this article knows this already and to
mention would be at best a waste of screen real estate.

This site is run by the people who run an observatory. It's not LIFE magazine,
the writers know their audience.

~~~
rdiddly
That means first of all that they're somewhat more familiar with high school
physics than "remotely familiar," and secondly that they also probably
shouldn't tolerate factual inaccuracies such as "[new instruments] have now
allowed astronomers to follow one of these stars, called S2, as it passed very
close to the black hole during May 2018." Is that an inelegantly-placed
prepositional phrase (since only the observation took place in May 2018 and
not the passing), or do people in the field refer to these things in the
present tense as a sort of shorthand? (I'm not one of them so I don't know.)

There are signs it's meant for a broader audience, e.g. "one of these stars,
called S2" instead of simply "star S2" (since everybody's already familiar
with it).

Or how about "The new measurements clearly reveal an effect called
gravitational redshift. Light from the star is stretched to longer wavelengths
by the very strong gravitational field of the black hole."

How often should experienced astrophysicists be subjected to the tedium of
this explanation of red-shift? Once every 5 articles? I would say: Since it's
a fact from their own field, they should be reminded of it less often than
they get reminded of what was happening on Earth when this stellar event
actually happened. Because if they're truly specialists, that means they
probably know jack squat about archaeology/anthropology or anything besides
astronomy/astrophysics, and might even appreciate the latter reminder.

------
sgillen
Very cool, it’s too bad we can’t see anything inside the event horizon yet
(and possibly can’t ever). That’s where the really interesting stuff might
happen. We know either our current understanding of GR or our current
understanding of QM is wrong because of the way they handle singularities
differently.

~~~
zerb
The more I think of it, while it's disappointing from a pure-science point of
view, doesn't the lack of our ability to determine whether it's QM or GR that
is flawed imply that each is already sufficiently powerful to probe any
practical realm we'd care about?

------
forapurpose
In the 26,000 light years between the telescope and the star, I would guess
that enough matter would exist, from stars to planets to dust, that it would
complete occlude our view of the star. I would expect that objects would
continuously be moving in and out of the way.

Is it that space is really so empty that you can get a direct view over 26,000
light years, or is it that we are looking at this star because it's one of the
few we can see directly, or is it something else?

~~~
saintgimp
It really is that empty. Science fiction movies mess up our perception, but
reality is way more mind-boggling that we realize.

Check this out: if you want to build a model galaxy to scale and you start
with the Sun as a two-foot-diameter exercise ball, how far away do you have to
travel before you can set down a smaller ball that represents Alpha Centauri,
our nearest(-ish) stellar neighbor?

10,993.3 miles.

Just bask in that for a while.

([http://www.exploratorium.edu/ronh/solar_system/](http://www.exploratorium.edu/ronh/solar_system/))

~~~
tehaugmenter
It is empty, but its filled with "Space Grease"

[https://www.theguardian.com/science/2018/jun/27/space-is-
ful...](https://www.theguardian.com/science/2018/jun/27/space-is-full-of-
dirty-toxic-grease-scientists-reveal)

~~~
monocasa
> found enough for 40 trillion trillion trillion packs of butter

What an incredibly useless unit of measurement. They somehow found something
worse than "olympic size swimming pools".

~~~
logfromblammo
How many packs of butter per Library of Congress?

The problem is that most people just cannot conceptualize really, really,
really large numbers, but journalists and authors try to make them more
relatable anyway, and end up just making it worse.

I think what they meant to say was that it could make a typical globular
cluster satellite of the Milky Way galaxy, containing about 225000 butter-
stars with the same mass as our sun.

~~~
Sean1708
> I think what they meant to say was that it could make a typical globular
> cluster satellite of the Milky Way galaxy, containing about 225000 butter-
> stars with the same mass as our sun.

I don't think it was anything near that complex: 40 trillion trillion trillion
is just the number of tubs of butter it takes to get 10 billion trillion
trillion tonnes if you assume each tub is 250 grams.

~~~
logfromblammo
Even then,

    
    
      10^3 = thousand
      10^6 = million
      10^9 = billion
      10^12 = trillion
      10^15 = quadrillion, or thousand trillion
      10^18 = quintillion, or million trillion
      10^21 = sextillion, or billion trillion
      10^24 = heptillion, or trillion trillion
      10^27 = octillion, or thousand trillion trillion
      10^30 = nonillion, or million trillion trillion
      10^33 = decillion, or billion trillion trillion
      10^36 = undecillion, or trillion trillion trillion
    

One of those numbering conventions is not tremendously useful, and the other
is very very very stupid. It compounds with the knowledge that some people
call 10^9 "a milliard" rather than "a billion". This is why we have SI unit
prefixes, and write numbers ending with an exponent of 10.

And here I was, assuming each "pack of butter" was one of those 10g single-
serving packs (although some are only 7.65g). I didn't check it against the
"tonnes" number in the article. In the US, a "pack of butter" could also be a
box containing 4 sticks 113 g each, totaling 454 grams, because butter in the
US is sold by the pound. Apparently, they are 250g elsewhere.

And a (metric) tonne is already 1000 kg, or 1 Mg. There is also the long ton,
which is 1016 kg, and the short ton, which is 907 kg.

The obfuscated number is therefore 1x10^40 g, which is even larger than
standard metric prefixes can express, so we'd probably write it as 1x10^37 kg,
for some reason.

So my previous math was wrong. That's _5 million_ butter-stars the size of our
sun, or enough butter to form a slippery, spreadable black hole as massive as
the one at the heart of our galaxy. I guess from this, we can calculate the
size of Audthumbla the giant space-cow?

------
mutagen
Anyone know why the black hole is marked well off the axis of the orbit of S2
in diagram [1]? Is there enough mass elsewhere at the center of the galaxy to
have it orbiting a common mass so far off axis? The video of the orbit [2]
seems to show it closer to the axis or the focus I'd expect but still
seemingly a bit of an offset. The fulldome view video [3] does show that there
is quite a bit of stuff moving around there so maybe my imaginations are
wrong, I think of a black hole having so much mass that it completely
dominates the local gravitational field.

1\.
[https://www.eso.org/public/unitedkingdom/images/eso1825c/](https://www.eso.org/public/unitedkingdom/images/eso1825c/)

2\.
[https://www.eso.org/public/unitedkingdom/videos/eso1825g/](https://www.eso.org/public/unitedkingdom/videos/eso1825g/)

3\.
[https://www.eso.org/public/unitedkingdom/videos/eso1825g/](https://www.eso.org/public/unitedkingdom/videos/eso1825g/)

~~~
contact_fusion
Keep in mind that you are viewing the orbit in projection. The axes are simply
the angular offset from the pointing.

Before I give away the punchline, try to imagine the orbit in a reference
frame centered at the location of the black hole. Obviously, the motion should
be elliptic; lets define a Cartesian coordinate system such that, say, the x-y
plane coincides with the plane of the elliptic orbit. Now, we know that the
black hole should reside at the focus of this orbit. But, as a far away
observer, what are the chances that you would be seeing the orbit exactly
face-on - i.e., you are sitting on the z axis, just really far away?

So, yes, the black hole is at the focus of the elliptic _orbit_ , not the
focus of the ellipse formed from the _projection of the orbit_ onto your
plane-of-sky, which geometry tells us is also an ellipse.

BTW, this isn't a problem for the astronomers. You can back out exactly what
that inclination of the orbit is, provided you can measure the line-of-sight
velocities of the star. (Actually, relative velocities will do; no absolute
calibration necessary.) This is easily done by looking for some distinctive
stellar spectral features and noting their relative shifts at different parts
of the orbit. From this you can reconstruct the orbit completely. The key
scientific results they derived was the _even subtler_ redshift of these
spectral features as the gravitational field grew stronger when the star
approached the black hole.

edit: actually, you could do even better, and use the offset of the black hole
from the elliptic focus, and use projective geometry to get the inclination
angle!

~~~
mutagen
Ahhh so simple! Thank you very much for the moment of enlightenment.

------
NizaAfrica
Question, is it possible that our universe could be in a black hole? When you
look at the way our existence is structured, everything has a parent. An an
electron has an atom has it's parent, atoms have molecules has their parent
etc. Germs, bacteria, humans, planets all have parents. Surely our universe
has to have a parent.

~~~
eponeponepon
Possible? Sure, anything is _possible_ \- but apply your argument the other
way round. People contain molecules, molecules contain atoms, atoms electrons
and so on - does it then seem reasonable to ask whether _that_ goes on
forever? And if not, why should it be reasonable if you go upwards in the
scale?

~~~
posterboy
But it does seem reasonable. Very much so if going down far enough you find
micro black holes at the center of atoms.

But you need some really funky geometry to make it more interesting then this
played out trope. Say they are all the same black hole from different times
seen through its own gravitational lense.

------
CosmicSteve
Cool news! I'm curious though, couldn't a quasar possibly cause the
gravitational redshift that was observed?

------
gigatexal
Coolest thing I have seen in a long time. Watched a replay of the livestream
and it is so good!

------
sixothree
Which of that imagery is actual imagery and not artist interpretation?

~~~
cwillu
[https://cdn.eso.org/images/large/eso1825g.jpg](https://cdn.eso.org/images/large/eso1825g.jpg)

[https://cdn.eso.org/videos/ultra_hd/eso1825e.mp4](https://cdn.eso.org/videos/ultra_hd/eso1825e.mp4)

