The older we get, the less we know (cosmologically)

May 22, 2012
New research finds that the ideal time to study the cosmos was more than 13 billion years ago, just about 500 million years after the Big Bang - the era (shown in this artist's conception) when the first stars and galaxies began to form. Since information about the early universe is lost when the first galaxies are made, the best time to view cosmic perturbations is right when stars began to form. Modern observers can still access this nascent era from a distance by using surveys designed to detect 21-cm radio emission from hydrogen gas at those early times.

(Phys.org) -- The universe is a marvelously complex place, filled with galaxies and larger-scale structures that have evolved over its 13.7-billion-year history. Those began as small perturbations of matter that grew over time, like ripples in a pond, as the universe expanded. By observing the large-scale cosmic wrinkles now, we can learn about the initial conditions of the universe. But is now really the best time to look, or would we get better information billions of years into the future - or the past?

New calculations by Harvard theorist Avi Loeb show that the ideal time to study the cosmos was more than 13 billion years ago, just about 500 million years after the Big Bang. The farther into the future you go from that time, the more information you lose about the early .

"I'm glad to be a at a cosmic time when we can still recover some of the clues about how the universe started," Loeb said.

Two competing processes define the best time to observe the cosmos. In the young universe the cosmic horizon is closer to you, so you see less. As the universe ages, you can see more of it because there's been time for light from more distant regions to travel to you. However, in the older and more evolved universe, matter has collapsed to make gravitationally bound objects. This "muddies the waters" of the cosmic pond, because you lose memory of initial conditions on small scales. The two effects counter each other - the first grows better as the second grows worse.

Loeb asked the question: When were viewing conditions optimal? He found that the best time to study cosmic perturbations was only 500 million years after the .

This is also the era when the first began to form. The timing is not coincidental. Since information about the early universe is lost when the first galaxies are made, the best time to view cosmic is right when stars began to form.

But it's not too late. Modern can still access this nascent era from a distance by using surveys designed to detect 21-cm radio emission from hydrogen gas at those early times. These radio waves take more than 13 billion years to reach us, so we can still see how the universe looked early on.

"21-centimeter surveys are our best hope," said Loeb. "By observing hydrogen at large distances, we can map how matter was distributed at the early times of interest."

The accelerating universe makes the picture bleak for future cosmologists. Because the expansion of the cosmos is accelerating, galaxies are being pushed beyond our horizon. Light that leaves those distant galaxies will never reach Earth in the far future. In addition, the scale of gravitationally unbound structures is growing larger and larger. Eventually they, too, will stretch beyond our horizon. Some time between 10 and 100 times the universe's current age, cosmologists will no longer be able to observe them.

"If we want to learn about the very , we'd better look now before it is too late!" Loeb said.

Explore further: How baryon acoustic oscillation reveals the expansion of the universe

More information: This research was published in the Journal of Cosmology and Astroparticle Physics (JCAP) and is available online.

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User comments : 14

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julianpenrod
1 / 5 (14) May 22, 2012
Again, the unbiverse is not accelerating. Only galaxies five billion light years away have been described as "accelerating". Those closer in, nearer to us in time, show no sign of this accelerating. They all proceed outward at an orderly Hubble Constant rate. Out to five billion light years, the same one constant works for all galaxies. At five billion light years, the speed purportedly suddenly changes.
But, again, even that report is suspicious. Because the galaxies listed as five billion light years away were calculated as that far away by their adherence to the Hubble Constant, too! The "discovery" was that "the galaxy was further away than expected". The "expected" was distance based on recession velocity. Which means the Doppler determined recession velocity is in conformity with the non-accelerated Hubble velocity! Even if it is "space that is expanding not the galaxy moving through space", it still expresses itself by Doppler shift.
komone
not rated yet May 22, 2012
Information loss? Hmmm. I too am suspicious of the present conclusions.
El_Nose
not rated yet May 22, 2012
ahh i don't think so
simplicio
4.6 / 5 (9) May 22, 2012
Again, the unbiverse is not accelerating. Only galaxies five billion light years away have been described as "accelerating".

With all the knowledge we have today, you are saying nonsense. Do you have any ref for your support (from scientific source)?
dan42day
4.6 / 5 (9) May 22, 2012
The best time to analyze the universe is when sufficient intelligence has evolved to do so.
travisr
5 / 5 (2) May 22, 2012
This is old, this same headline was done maybe a year or so ago. Sadly, it was also done much better then this piece as well...
julianpenrod
1 / 5 (10) May 22, 2012
simplicio is so rabidly devoted to contradicting me and defending "the official story", they don't realize they are defeating their own purpose! The 2011 Nobel Prize was won by "scientists", Perlmutter and the others, who claimed to have "discovered" that galaxies five billion light years away are "accelerating"! But those same "scientists" did not say galaxies closer in were accelerating! It's only those five billion light years away that they essentially "scientifically" claimed were further away than five billion light years! Those less than five billion light years away are where they're supposed to be!
simplicio
5 / 5 (6) May 22, 2012
simplicio is so rabidly devoted to contradicting me and defending "the official story", they don't realize they are defeating their own purpose!

You use many quotations marks in reply but do not give any scientific journal quotation refs for your position (whatever it is).
DavidW
1 / 5 (4) May 23, 2012
The best time to analyze the universe is when sufficient intelligence has evolved to do so.


The only time anything can be done is in the now. Time/space is abstract observation/thought in the brain of a living animal on this planet, same as numbers and speech.
aroman_ro
not rated yet May 23, 2012
The 21 cm hydrogen line is redshifted due of expansion, so '21 cm surveys' are not exactly the best hope. The frequency can go down to 9 MHz, depending on the distance.
antialias_physorg
5 / 5 (9) May 23, 2012
simplicio is so rabidly devoted to contradicting me

Nope. He just seems devoted to calling people on it when they post BS. And since you post nothing but it's no wonder it seems like he's following you around.

The only time anything can be done is in the now.

The question in the article is about how much information becomes inaccessible over time. With an expanding universe we will eventually come to the point where there are no other galaxies visible to us (in about 100 billion years - so still some time left for galaxy-gazing).
An intelligence that evolves at that time would conclude that the universe is 'steady state' and that this galaxy is all there is to it (even the CMBR will likley have dropped below observation threshold by then).
Au-Pu
1 / 5 (1) May 27, 2012
The opening paragraph about loss of information is, as the English would say, "stating the bleeding obvious".
Doesn't anyone think it remarkably convenient that the "age" of the universe equals the distance from where we are to our event horizon?
Break the mental bonds, think outside the hide bound Big Bang Theory.
Terriva
1 / 5 (1) May 27, 2012
The older we get, the less we know (cosmologically)
In AWT the appearance of distant universe is given with scattering of light with density fluctuations of vacuum, not with evolution of Universe as such. The result is indeed the same: the farther the objects are, the more difficult is their observation (which is trivial), so we should use the radiation at the wavelength, which don't disperse so much, the wavelength of CMBR in particular (which is less trivial conclusion). The photons scatter in the smallest extent, when they're of the same wavelength.
Burnerjack
not rated yet May 27, 2012
I don't know about "cosmologically" but I DO know that when I was a teenager I knew ALOT MORE than I do now!...LOL!