Far-future astronomers could still deduce the Big Bang

Apr 14, 2011
Artist’s conception of the cosmic view a trillion years from now. Credit: David A. Aguilar (CfA)

(PhysOrg.com) -- One trillion years from now, an alien astronomer in our galaxy will have a difficult time figuring out how the universe began. They won't have the evidence that we enjoy today.

Edwin Hubble made the first observations in support of the model. He showed that galaxies are rushing away from each other due to the universe's expansion. More recently, discovered a pervasive afterglow from the Big Bang, known as the , left over from the universe's white-hot beginning.

In a trillion years, when the universe is 100 times older than it is now, alien astronomers will have a very different view. The Milky Way will have merged with the to form the Milkomeda galaxy. Many of its stars, including our Sun, will have burned out. The universe's ever-accelerating expansion will send all other galaxies rushing beyond our "cosmic horizon," sending them forever out of view.

The same expansion will cause the cosmic microwave background to fade out, stretching the wavelength of CMB photons to become longer than the visible universe. Without the clues of the CMB and distant, receding galaxies, how will these far-future astronomers know the Big Bang happened?

According to Harvard theorist Avi Loeb, clever astronomers in 1 trillion C.E. could still infer the Big Bang and today's leading cosmological theory, known as "lambda-cold dark matter" or LCDM. They will have to use the most distant light source available to them - hypervelocity stars flung from the center of Milkomeda.

"We used to think that observational cosmology wouldn't be feasible a trillion years from now," said Loeb, who directs the Institute for Theory and Computation at the Harvard-Smithsonian Center for Astrophysics. "Now we know this won't be the case. Hypervelocity stars will allow Milkomeda residents to learn about the cosmic expansion and reconstruct the past."

About once every 100,000 years, a binary-star system wanders too close to the black hole at our galaxy's center and gets ripped apart. One star falls into the black hole while the other is flung outward at a speed greater than 1 million miles per hour - fast enough to be ejected from the galaxy entirely.

Finding these hypervelocity stars is more challenging than spotting a needle in a haystack, but future astronomers would have a good reason to hunt diligently. Once they get far enough from Milkomeda's gravitational pull, these stars will get accelerated by the universe's expansion. Astronomers could measure that acceleration with technologies more advanced than we have today. This would provide a different line of evidence for an expanding universe, similar to Hubble's discovery but more difficult due to the very small effect being measured.

By studying stars within Milkomeda, they could infer when the galaxy formed. Combining that information with the star measurements, they could calculate the age of the universe and key cosmological parameters like the value of the cosmological constant (the lambda in LCDM).

"Astronomers of the future won't have to take the Big Bang on faith. With careful measurements and clever analysis, they can find the subtle evidence outlining the history of the universe," said Loeb.

Explore further: Planets with oddball orbits like Mercury could host life

More information: This research appears in a paper accepted for publication in the Journal of Cosmology and Astroparticle Physics and available online.

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User comments : 17

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jamesrm
3 / 5 (12) Apr 14, 2011
such arrogance
Gawad
5 / 5 (5) Apr 14, 2011
Interesting, but how they might avoid thinking that Milkomeda (Androway?) isn't the centre of their universe. With all the hyper-velocity stars originating from the galactic centre that would be hard. They'd have the expansion part right, but when they "roll back" their universe to its spacial "origin" (their galactic centre) they run into a severe inhomogeneity problem. I.e., why is matter so unevenly distributed in the cosmos. Then there would be the stellar/galactic evolution problem. They'd know their universe can't be rolled back infinitely-there would be no more main sequence stars in their present. On reflection, their galaxy would BE the centre of *their* universe, but they might hypothesize a multiverse of universes that have galaxies at their centre. They might even imagine that those separate universes were once in contact before being sent over the cosmic horizon, and even maybe have a common origin. Of course, all that would be completely speculative and unfalsifiable :)
Quantum_Conundrum
1.1 / 5 (12) Apr 14, 2011
Yeah, incredibly arrogant article.

What even makes you think that life could survive this alleged galactic merger, or that the galaxy would somehow be inhabitable/inhabited by human level intelligence at any time after such an even?

Oh yeah, nobody really cares about absurd projections of a trillion years into the future.
GeeDoubleYa
1.4 / 5 (9) Apr 14, 2011
Astronomers of the future may come to realize that light loses a very small amount of energy as it traverses vast distances over billions of years. This causes a photon's frequency to become lower and its wavelength to become longer, creating the illusion of red-shift and the notion of an ever-expanding universe.

A trillion years from now, the universe will be very much the same as it is today in a relative way: evolving, changing, and unbounded, with its cosmic background radiation simply emanating from an eternity's worth of detritus, kept 'warm' in an infinite soup of photons.

Astronomers of the future may come to realize that Hubble jumped to an erroneous conclusion -- he was wrong.
zevkirsh
3 / 5 (5) Apr 14, 2011
we don't know enough about our universe ( no unified theory) now to know how it will look in a trillion years. even if we give ourselves an array of possibilities, we could be missing key information and leave out the very outcome amongst these possibilities.

if it weren't hard to enough to keep believing in scientifically deduced truths like the origins of the heavy elements all coming from supernova, i do feel that speculation like this is where science becomes science fiction, or just plain fiction.
J-n
5 / 5 (4) Apr 14, 2011
light loses a very small amount of energy as it traverses vast distances over billions of years


Not being horribly versed in many areas of physics this statement brings up a question. Where does this energy go, and Why does it loose energy?
GeeDoubleYa
1.3 / 5 (3) Apr 14, 2011
J-n,
I thought about conservation of energy and the best that I could come-up with was that a photon looses (transfers) energy due to some sort of an interaction with space-time (gravity), sub-atomic particles (like neutrinos), or perhaps with other lower-energy photons.

It's easy to speculate but it's going to be darn difficult to prove.
GSwift7
4.3 / 5 (6) Apr 14, 2011
The energy doesn't get lost, it just stretches out and is diffused to the point that it is undetectable. With a wavelength larger than the visible universe, it would appear to us that it ceased to exist but that's just a limit of observation.
rynox
2.7 / 5 (3) Apr 14, 2011
It seems to me some 'external' force must have been at work to initiate the big bang. I've always wondered, if this is true, is this external force still acting on our universe?
GSwift7
4 / 5 (4) Apr 14, 2011
that's almost a meaningless question. That's kinda like wondering if it is possible that there are other universes and whether it is possible for ours to collide with one of them as they both expand. If we expand into a negative (antimatter?) universe, would they cancel each other out as they overlap?

Even if we could derive an answer, is there any way to prove it?

Is it even sane to ponder such things? Are such questions the result of our limited ability as observers? We are after all a biological organism, with basic limitations like brain capacity and sensory organs.
Gawad
5 / 5 (7) Apr 14, 2011
Astronomers...may come to realize that light loses a very small amount of energy as it traverses vast distances
Tired of tired light. You're wrong; Hubble was right.
A trillion years from now, the universe will be very much the same as it is today.
Unless you can make fresh hydrogen magically, spontaneously appear in the void of space and clear out an *eternity's worth* of stellar and planetary remnants your static universe is a dead end. The C-Field is old news. Time to move on.
...the best that I could come-up with was that a photon looses (transfers) energy due to some sort of an interaction with space-time (gravity), sub-atomic particles (like neutrinos)
Ergo, you haven't come up with anything...but you've decided that Hubble was just wrong. Priceless.
Gawad
3.9 / 5 (7) Apr 14, 2011
What even makes you think that life could survive this alleged galactic merger
What makes you think life wouldn't? The average stellar density in both galaxies means that nearly 100% of their stars will still pass by each other at distances of lightyears. So where's the problem? If anything, such a merger would lead to increased star creation, giving life additional chances to emerge.
...or that the galaxy would somehow be inhabitable/inhabited by human level intelligence at any time after such an even?
On the timescales of the article the 2 galaxies will have been merged for 98% of the universe's lifetime, so the point is moot. So again, why not?
Oh yeah, nobody really cares about absurd projections of a trillion years into the future.
That's right! S**t like this is almost as stupid as imagining yourself riding a photon. What a stupid mental image. Just goes to show what useless dead ends day dreaming like this can lead to. No understanding to be had here. Move on.
frajo
4.5 / 5 (4) Apr 14, 2011
The Milky Way will have merged with the Andromeda galaxy to form the Milkomeda galaxy
That's an ugly misnomer, perhaps in the tradition of corporation mergers.
The term "Milky Way" was coined after the Greek word "galaxia" where "gala" is Greek for "milk". The mythos tells that Heracles was trying to drink from the breasts of goddess Hera but was pushed back whereby she spilled her milk all over the sky.
Andromeda was a mythical name, too.

"Milkomeda galaxy" thus would be something like a "Milkomeda Milky Way". A linguistic atrocity.
CHollman82
3.7 / 5 (3) Apr 14, 2011
What even makes you think that life could survive this alleged galactic merger


Sorry QC... but you're pretty dumb.
ZephirAWT
Apr 15, 2011
This comment has been removed by a moderator.
Thrasymachus
3 / 5 (1) Apr 15, 2011
Here I thought the whole Universe only had about another 30 billion years or so, as the expansion of space-time accelerates to the point where molecular and atomic forces are overwhelmed by that expansion.
Gawad
not rated yet Apr 15, 2011
Oh yeah, nobody really cares about absurd projections of a trillion years into the future.
That's right! S**t like this is almost as stupid as imagining yourself riding a photon. What a stupid mental image. Just goes to show what useless dead ends day dreaming like this can lead to. No understanding to be had here.
Oh, and just in case anyone thought I was being serious, that was sarcasm. PO doesn't handle and tags very well.
omatumr
1 / 5 (3) Apr 16, 2011
Here I thought the whole Universe only had about another 30 billion years or so, as the expansion of space-time accelerates. . . .


If the rest of the universe, like our tiny corner, is powered by dynamic competition between

a.) Attractive forces of gravity, and
b.) Repulsive forces between neutrons

Then the universe may be infinite and cyclic [1,2] rather than finite and restricted to one direction of evolution.

1. "On the cosmic nuclear cycle and the similarity of nuclei and stars", Journal of Fusion Energy 25 (2006) pp. 107-114:
http://arxiv.org/...511051v1

2. Neutron Repulsion, The APEIRON Journal, in press, 19 pages:
http://arxiv.org/...2.1499v1