
The Disappearing Universe - vilda
https://medium.com/@startswithabang/the-disappearing-universe-d7447467c63a
======
p1mrx
If there's any possible way to corrupt spacetime, resulting in a sphere of
destruction that expands outward at the speed of light, then maybe an
accelerating universe could act as a firewall. What if we're here because the
non-accelerating universes with intelligent life tend to get wiped out?

~~~
dtbx
There is a novel about that. "Schild's Ladder", by Greg Egan.

But in that novel, the sphere of destruction expands only at c/2.

~~~
stcredzero
If it expanded at C, it would be a shorter book.

------
dave809
Leonard Susskind talked about this idea and expanded on it in his talk 'Why is
time a one way street'

Highly recommend the talk.

[http://www.youtube.com/watch?v=jhnKBKZvb_U](http://www.youtube.com/watch?v=jhnKBKZvb_U)

~~~
hcarvalhoalves
That was very interesting, thanks for sharing.

I can see the elegance of using fractal math to explain the big bang,
cosmological expansion and the apparent structure our universe exhibits (as
opposed to being an inert soup).

------
nkoren
I first read about this many years ago, in Olav Stapledon's brilliant _Star
Maker_ , about a man who takes a magical mystery tour through the whole of
time and space:

    
    
       "Then the Star Maker said, "Let there be light." And there was light. From all
        the coincident and punctual centers of power, light leapt and blazed. The 
        cosmos exploded, actualizing its potentiality of space and time. The centers 
        of power, like fragments of a bursting bomb, were hurled apart. But each one 
        retained in itself, as a memory and a longing, the single spirit of the whole; 
        and each mirrored in itself aspects of all others throughout all the cosmical 
        space and time.
        
        "No longer punctual, the cosmos was now a volume of inconceivably dense matter 
        and inconceivably violent radiation, constantly expanding. And it was a 
        sleeping and infi-nitely dissociated spirit.But to say that the cosmos was 
        expanding is equally to say that its members were contracting. The ultimate 
        centers of power, each at first coincident with the punctual cosmos, 
        themselves generated the cosmical space by their disengagement from each other. 
        The expansion of the whole cosmos was but the shrinkage of all its physical 
        units and of the wave-lengths of its light. Though the cosmos was ever of 
        finite bulk, in relation to its minutiae of light-waves, it was boundless and 
        center-less. As the surface of a swelling sphere lacks boundary and center, so 
        the swelling volume of the cosmos was boundless and center-less. But as the 
        spherical surface is centered on a point foreign to it, in a "third dimension," 
        so the volume of the cosmos was centered in a point foreign to it, in a 
        "fourth dimension."
    
        "The congested and exploding cloud of fire swelled till it was of a planet's 
        size, a star's size, the size of a whole galaxy, and of ten million galaxies. 
        And in swelling it became more tenuous, less brilliant, less turbulent. 
        Presently the cosmical cloud was disrupted by the stress of its expansion in 
        conflict with the mutual clinging of its parts, disrupted into many million 
        cloudlets, the swarm of the great nebulae.
    
        "For a while these were as close to one another in relation to their bulk as 
        the flocculations of a mottled sky. But the channels between them widened,
        till they were separated as flowers on a bush, as bees in a flying swarm, as 
        birds migrating, as ships on the sea. More and more rapidly they retreated 
        from one another; and at the same time each cloud contracted, becoming first 
        a ball of down and then a spinning lens and then a featured whirl of star-
        streams.
    
        "Still the cosmos expanded, till the galaxies that were most remote from one 
        another were flying apart so swiftly that the creeping light of the cosmos 
        could no longer bridge the gulf between them."
    

Written, impossibly, in 1936.

~~~
fsiefken
Yes, I remember that as well, great book by the way. As much as I'd like to
attribute clairvoyance to Olaf Stapledon also with regard to his fictional(?)
mystical out of body experience, I'm skeptic. There already was a big bang
theory and the red- and blueshift of starlight was already discovered. So I'd
think speculation that some galaxies are speeding away from us faster then the
speed of light was not impossible in 1936, am I right?

~~~
nkoren
Georges Lemaître had proposed an early version of the Big Bang theory in 1931.
In 1936 it was nowhere near the scientific consensus -- that didn't happen
until the discovery of the Cosmic Microwave Background, 29 years later.

But knowledge of the Big Bang and the Hubble redshift aren't, by themselves,
sufficient to explain what Stapledon wrote. Those things just show that the
universe _has_ expanded. For most of the 20th century, people assumed that the
acceleration of the universe would diminish -- either asymptotically
approaching zero, or reversing into a "Big Crunch". For the galaxies to
accelerate beyond the point where photons can bridge the gaps between them,
they need to not only have been accelerated, but to _keep accelerating_ ,
which is a very unintuitive notion (what would be driving the acceleration?)

My guess is that Stapledon was influenced by Einstein's Cosmological Constant,
which predicted exactly this kind of acceleration, but which Einstein himself
had repudiated several years earlier, calling it "his biggest blunder". When I
first read Star Maker in 1997, I figured that even if Stapledon had been up-
to-the-minute about the Big Bang, he somehow hadn't gotten the memo about the
Cosmological Constant. So I chalked this passage up as one of several things
that Stapledon had definitely gotten wrong.

A year later, Dark Energy was discovered, and suddenly it appeared that
Stapledon was right all along. This did my head in a bit. Somehow, Stapledon
had been spectacularly smart/lucky in crafting his story from a mix of
freshly-proposed and freshly-discarded theories. So no, clairvoyance isn't
strictly necessary to explain this. But just to be safe, I'll retain that
parenthetical question mark after "fictional(?)" when describing Star Maker.

~~~
mcguire
If I understand correctly, Einstein's cosmological constant was intended to
produce a steady-state universe, not an accelerating one.

20th century cosmology could be seen as a long argument over the sign of
Einstein's constant.

~~~
nkoren
I think you're correct about the motivation for the cosmological constant. By
adjusting the sign of the sign of the constant, you could produce a universe
which was expanding, contracting, or steady-state. When Hubble's constant got
nailed down, that definitively meant that the universe was expanding, and
Einstein was happy to accept that. The problem was that if you tweak the
constant to produce that result, then it also says that the universe is not
only expanding, but _accelerating_. Which didn't seem to make the slightest
bit of sense, so Einstein dropped it, and Stapledon didn't.

(Standard disclaimer: I'm not a cosmologist, and probably have no idea what
I'm talking about.)

~~~
fsiefken
Fascinating! I think it's better to look at Hubble's law then the cosmological
constant in this particular regard. Hubble's law was published at the end 20's
decade. If you contemplate the law it follows naturally (although counter-
intuitively) that very far away galaxy's might speed away from each other
faster then the speed of light. How this can be understood with regard to
relativistic effects or the uncross-able universal light speeding law is
another intriguing topic. So perhaps Stapledon thought of this or someone else
thought about this (Lemaitre?) and Stapledon read or heard it. With regard to
the cosmological constant, Einstein dropped it but Lemaitre didn't. Lemaitre
argued in the early 1930's that the rate of expansion of the universe was
accelerating. [http://www.amazon.com/The-Day-Without-Yesterday-
Cosmology/dp...](http://www.amazon.com/The-Day-Without-Yesterday-
Cosmology/dp/1560259027)

"Lemaître was then invited to London in order to take part in a meeting of the
British Association on the relation between the physical Universe and
spirituality. There he proposed that the Universe expanded from an initial
point, which he called the "Primeval Atom" and developed in a report published
in Nature.[15] Lemaître himself also described his theory as "the Cosmic Egg
exploding at the moment of the creation"; it became better known as the "Big
Bang theory," a pejorative term coined during a BBC radio broadcast by Fred
Hoyle who was an obstinate proponent of the steady state universe, even until
his death in 2001."
[http://en.wikipedia.org/wiki/Georges_Lema%C3%AEtre](http://en.wikipedia.org/wiki/Georges_Lema%C3%AEtre)

So some have (mistakenly) attributed intuition of dark energy to Einstein and
his cosmological constant or some like you would argue that Stapledon was
spectacularly smart or lucky but I think I'd attribute it to Lemaitre and I
think indirectly (or directly) Stapledon heard or read about this. Perhaps as
an academic he was even present at the "British Association" meetup on science
and spirituality.

But if so, why did Lemaitre keep Einstein's cosmological constant in his own
work and why did he think the expansion rate of the universe was increasing?

Even so I'd like to believe Stapledon really was traveling among the stars 'in
some way', also his description of the out of body experience is oddly similar
to credible accounts later in the 20th century and might be autobiographical
but if not could be explained by him reading earlier accounts of this
psychological effect.

edit: apparently Lemaitre discovered Hubble's law before Hubble did!
[http://www.universetoday.com/90862/the-expanding-universe-
cr...](http://www.universetoday.com/90862/the-expanding-universe-credit-to-
hubble-or-lemaitre/)

~~~
nkoren
This kind of comment is what keeps me coming back to Hacker News. I didn't
know that Lemaître had proposed that the expansion was accelerating --
actually, I didn't know much about Lemaître at all, truth be told. ( _The Day
Without Yesterday_ just went on my reading list -- thanks!). In any case, I
guess Stapledon must have been working off of Lemaître's model, rather than
cooking up something unique.

Still, like you, I do like to imagine that Stapledon tapped into _something_
that was somehow beyond the ordinary. I don't feel like speculating beyond
that, but however he did it, Star Maker is an extraordinary book.

~~~
fsiefken
As a humble scientist Lemaître didn't take the credit of the discovery of the
expanding universe. Appearently there was a nice presentation by experimental
particle astrophysicist Ariel Goobar at "Symposium - Georges Lemaître’s Big
Bang In Modern Cosmology: A Celebration" last month:
[https://fys.kuleuven.be/ster/meetings/lemaitre/programme](https://fys.kuleuven.be/ster/meetings/lemaitre/programme)

At the end it states: "SNIa cosmology provides stunning conﬁrmation of cosmic
expansion – as predicted by Lemaitre in 1927! • Expansion currently
accelerating – as proposed early on by Lemaitre to explain the age of the
Universe • Is it Einstein’s CC or some exotic new phenomena? Observers busy
trying to ﬁnd out. Theory badly needed!"

Perhaps the dark energy is the combined weight of all those unproven
undiscovered astral dimensions :-) Or perhaps it's something more mundane as
unproven strings or quintessence:
[http://blogs.scientificamerican.com/critical-
opalescence/201...](http://blogs.scientificamerican.com/critical-
opalescence/2012/06/11/is-dark-matter-a-glimpse-of-a-deeper-level-of-reality/)
[http://www.newscientist.com/article/dn12261-is-dark-
energy-l...](http://www.newscientist.com/article/dn12261-is-dark-energy-
lurking-in-hidden-spatial-dimensions.html)
[http://en.wikipedia.org/wiki/Quintessence_(physics)](http://en.wikipedia.org/wiki/Quintessence_\(physics\))

------
dkural
It is very interesting that essentially there are causally disconnected
subsets of the universe - each a sub universe onto their own. Although
globally not possible, is the gravitational collapse scenario plausible for
some of these causally disconnected subsets? Tying it with the fact that
galaxies seem to be slowly eaten by their black hole centers, would this be an
example of a local gravitational collapse?

And when this process is over, what happens to all the black holes, isolated
from everything else.. do they just dissipate out, creating a uniform, cold,
low entropy universe?

~~~
bronson
Correct. As we understand it now, the black holes will slowly evaporate
through Hawking radiation.

[http://en.wikipedia.org/wiki/Future_of_an_expanding_universe...](http://en.wikipedia.org/wiki/Future_of_an_expanding_universe#Black_Hole_Era)

And, after that, oblivion.

[http://en.wikipedia.org/wiki/Heat_death_of_the_universe#Curr...](http://en.wikipedia.org/wiki/Heat_death_of_the_universe#Current_status)

------
Gobiel
If we could achieve near-light speed, how would time work for those traveling
at that speed relative to the universe ? Wouldn't time "feel" normal but
"stopped" relative to the other slower bodies of the universe ? As such,
couldn't that near-light speed "slow down" the rate at wich we see the
expansion of the universe, making possible star traveling ?

~~~
Udo
Being aboard a spaceship that's accelerated to such speeds would feel pretty
normal internally, but the outside universe would pass by very quickly and
processes in that universe would appear to be impossibly fast. Accelerated to
a very significant fraction of c would allow you to visit practically
everywhere in the galaxy within a few years of ship time. But on the outside,
millennia will have passed.

You can see why that's not practical, because everything you left behind would
be gone. Still, there are scenarios where this might be a valid solution.

However, you could never reach a destination that's speeding away from you
faster than the speed of light. Because you can't accelerate your spacecraft
beyond that speed, parts of the universe will always be unreachable - which is
the point of the article.

You might wonder why galaxies moving away from each other faster than the
speed of light works at all given the cosmic speed limit. The answer is that
their "movement" is not normal, inertial movement as we know it. Instead you
might imagine that new space is being created in between them, driving them
away from each other by simply scaling up the distances involved.

Given the practical and theoretical limits on spacecraft acceleration, people
have been thinking about a different way to travel, a way that doesn't involve
momentum but instead manipulates spacetime to simply shift an object to
another position without acceleration. The article hints at this as well. It
makes sense because technically the acceleration and deceleration part of a
journey is wasteful and limiting. At this time, it's the only way we know how
to get from A to B, but we're all hopeful that one or more alternatives can be
researched which allow us to simply go somewhere else without using
traditional movement.

------
emeraldd
I wonder if this has any impact on the Fermi Paradox? Could it be that any
sufficiently advanced civilization finds itself beyond the "red out" horizon
before having a chance to say hello to anyone else? (Pure speculation of
course, but so is the question in the first place.)

~~~
lisper
Almost certainly not. You don't need to leave our galaxy to make the case for
Fermi's paradox. Something more like a Great Filter
([http://en.wikipedia.org/wiki/Great_Filter](http://en.wikipedia.org/wiki/Great_Filter))
is more likely in play.

------
2Pacalypse-
Lawrence Krauss talked about this in his entertaining and famous talk, A
Universe From Nothing[1].

[1] -
[http://www.youtube.com/watch?v=7ImvlS8PLIo](http://www.youtube.com/watch?v=7ImvlS8PLIo)

------
jofo25
I seem to remember from physics class that mass cannot travel faster than the
speed of light, so how is it possible for galaxies to be unreachable if you
managed to travel at the speed of light?

~~~
gerhardi
Imagine that you go running with a friend. You run at 0.9 * speed of light and
your friend runs at 0.8 * speed of light in the exact opposite direction. How
fast are you getting away from each other?

~~~
epi16
I'm not sure I understand. It seems like you're implying that the two people
would be moving away from each other faster than the speed of light, but I was
under the impression that that's not the case. I thought that each person
would observe the other travelling at C?

~~~
VexXtreme
I think they would observe each other traveling at C but would experience
visible time dilation (in the other person's frame of reference).

------
ivanca
I'm looking at the bright side, it means that we don't even need to achieve
speed of light to travel to other galaxies, because the universe is ever-
expanding it means that some planets will occupy the space our planet is in
now, so theoretically if we can figure how to live in a static point in the
universe (e.g, absolute position, not relative to our solar system) some day
in the future (millions of years from now) we could visit other galaxies.

~~~
maaku
what? No. there is absolutely no such thing as an absolute position in the
universe.

~~~
edem
What if we find the point where the Big Bang happened?

~~~
rlpb
There is no such point (or it is everywhere if you like, as someone else had
said).

The best analogy I've seen is that of ants on a balloon. They live in what
appears to them to be a two dimensional universe. As you inflate the balloon,
they observe their own universe getting bigger. But the "point where the Big
Bang happened" to them is not a point that even exists in their universe any
more. They cannot get back there, since the higher third dimension does not
exist in their universe.

~~~
edem
That's a nice analogy. Now I understand!

------
glbrew
Now I'm sad

~~~
VanillaCafe
On the bright side, we'll probably never explore much of our galaxy, let alone
the universe at large.

~~~
spullara
I'm pretty convinced we will either die out or fill the galaxy with people. If
we can start the reaction by going one other place and inhabiting it I think
it will ultimately set off a chain reaction. Lots of work to do between now
and then but it seems like its mostly engineering now vs new discoveries.

~~~
hueving
> Lots of work to do between now and then but it seems like its mostly
> engineering now vs new discoveries.

I'm not sure what you mean by this. There are still lots of issues with just
surviving the journey, let alone making a foreign planet habitable and
establishing a society. We need lots more discoveries in energy and
understanding human physiology before it becomes just an engineering problem.

