Is the universe really 13.7 billion years old?

[Kurious12]

It is said that the universe is 13.7 billion years old because we have seen light from an exploding star that took place 13.7 billion light years from earth, and it is also said that 13.7 billion years ago the universe was smaller than an atom, so how on earth could anything have been 13.7 billion light years apart? Some scientist say that 13.7 billion light years is the limit of what our technology can see and interpret and that we don't really know the true age of the universe. Isn't giving the universe an age based on the limit of our technology the same thing as standing on a beach back in 1300 AD, looking out on the horizon and saying the earth is flat because that's all we can see?

[joigus]

You are conflating several things here that are actually different.

Surface of last scattering: The surface in the night sky beyond which we cannot see because at times older than that the universe was opaque to radiation.

The distance to us of this layer of the universe changes with time, and is being pushed by expansion towards the kinematical horizon --see below.

Kinematical horizon: In a De Sitter universe, every observer has a limit to how far away he can see the galaxies.

The distance to us of this layer of the universe is fixed in a universe with a constant rate of expansion, and so doesn't change with time. It doesn't depend on technology either, as it is given by a natural limit. Namely, receding velocities greater than the speed of light don't allow you to see anything there due to redshift.

Why the surface of last scattering is "about to disappear" (give or take a couple of billion years) from view in this time of the history of the universe, and whether that is a coincidence, is not known. But it appears to be so.

 

[beecee]

4 hours ago, Kurious12 said:

It is said that the universe is 13.7 billion years old because we have seen light from an exploding star that took place 13.7 billion light years from earth, and it is also said that 13.7 billion years ago the universe was smaller than an atom, so how on earth could anything have been 13.7 billion light years apart? Some scientist say that 13.7 billion light years is the limit of what our technology can see and interpret and that we don't really know the true age of the universe. Isn't giving the universe an age based on the limit of our technology the same thing as standing on a beach back in 1300 AD, looking out on the horizon and saying the earth is flat because that's all we can see?

We did not see any light from any exploding star from 13.7 billion years ago. There was no explosion as such, simply an evolution of space and time (as we know them) an inflationary process and expansion. At that stage around t+10-45th seconds, the four forces were combined as one, and then as expansion took hold, temperatures and pressures dropped, the "superforce" started to decouple, gravity first. As temperatures and pressures dropped and the superforce separated, phase transions and false vacuums were formed and the excesses of energy went into creating our first fundamental particles.  At 3 minutes post BB, our protons and neutrons formed and first atomic nucleii. It took another 383000 years for conditions to be such that electrons were captured and our first light elements took hold. 

The age is being revised and modified as needed, and according to data from more state of the art probes, along with other cosmological figures.

[swansont]

The first stars formed ~100 million years after the big bang

https://www.physics.uu.se/research/astronomy-and-space-physics/research/galaxies/first-stars-galaxies/

[exchemist]

5 hours ago, Kurious12 said:

It is said that the universe is 13.7 billion years old because we have seen light from an exploding star that took place 13.7 billion light years from earth, and it is also said that 13.7 billion years ago the universe was smaller than an atom, so how on earth could anything have been 13.7 billion light years apart? Some scientist say that 13.7 billion light years is the limit of what our technology can see and interpret and that we don't really know the true age of the universe. Isn't giving the universe an age based on the limit of our technology the same thing as standing on a beach back in 1300 AD, looking out on the horizon and saying the earth is flat because that's all we can see?

But since that would be silly, that can't be what science is saying. 

I'm not a cosmologist but as I understand it, the age can be estimated, in the Big Bang model, from the temperature of the observed cosmic background radiation and the observed cosmological red shift. The temperature tells you how much space has expanded since the "surface of last scattering", which was the point at which it would have been effectively emitted, while the cosmological red shift gives you an expansion rate. Put the two together and you have an age estimate, back to the surface of last scattering. Extrapolating back from that on the basis of general relativity, you end up with a singularity about 300,000years earlier.

So the model is based on observations of features of the universe that we have reason to think would be general, rather than specific to what we can observe with current technology. It is quite good at accounting for other observed features of the observable universe as well.

There is more about it here: https://en.wikipedia.org/wiki/Lambda-CDM_model    

[Outrider]

14 hours ago, Kurious12 said:

Isn't giving the universe an age based on the limit of our technology the same thing as standing on a beach back in 1300 AD, looking out on the horizon and saying the earth is flat because that's all we can see?

Others have done a good job addressing some of your misconceptions. You have a lot of reading to do if you really want to understand the mountain of evidence we have on the age of the universe. I suggest "pale blue dot" by Carl Sagan. It's a bit dated but still a great starting point to a wonderful journey should you take it.

 

So whats the difference you asked. Well the person on the beach didn't go look. We (as a species) have. Billions have been spent and many very smart individuals have spent their whole lives investigating the age of the universe question. 

The person on the beach could have found a way to travel in a straight line till they arrived back at the beach. Then would have known the earth isn't flat.

Or they could have used some sticks and shadows like Eratosthenes did over 2,000 years ago.

 

https://www.aps.org/publications/apsnews/200606/history.cfm#:~:text=By around 500 B.C.%2C most,method of estimating its circumference.

[Kurious12]

On 5/31/2022 at 3:24 AM, beecee said:

We did not see any light from any exploding star from 13.7 billion years ago

You're right, it wasn't an exploding star that they were talking about, was watching a documentary called "The Universe" and they were talking about the farthest light detected by Hubble which was a galaxy about 13 billion light years away from earth, the scientist were saying that 13.7 is just the limit of what our technology can see. In a documentary called "How the Universe Works", they were talking about how the standard candle technique that they use to measure the distant of galaxies and the expansion of space may not be as accurate as thought before. I'm sure that there's much more that went into coming up with that number but I was curious as to how all of this would affect the number 13.7 billion years old.

[MigL]

"Is the universe really 13.7 billion years old ?"

Doesn't need to be.
It could have been created yesterday, along with all the evidence of being 13.7 billion years old.
But, since all we have to go on, is the evidence, I guess we'll have to say, yes, it really is.

[Luzephyr]

I should like to see that evidence.

[MigL]

17 minutes ago, Luzephyr said:

I should like to see that evidence.

Have you not read any of the preceding posts ?

Using the equations developed by Meghnad Saha in the 1920s, we can calculate the ionization state of a gas in thermal equilibrium from the temperature and pressure.
All gases in the early universe ( mostly Hydrogen and Helium ) remained completely ionized down to a temperature of about 3000^oK.
In this state, the universe consisted of an opaque plasma, but once it expanded further, and dropped below this temperature, electrons were allowed to bond to nuclei to form atomic Hydrogen and Helium, rendering the universe transparent.
We 'see' the glow of the opaque ionized plasma as the CMB radiation, but it is no longer at 3000^oK, it is now at 2.7^oK, a reduction of about 1040 times.
We can then use your standard statistical thermodynamic gas laws, which relate temperature, volume and pressure, to conclude that the universe must have increased in volume by the equivalent factor of 1040 times, since the recombination era ( when atoms were able to form )

[Airbrush]

On 6/1/2022 at 9:51 PM, Kurious12 said:

You're right, it wasn't an exploding star that they were talking about, was watching a documentary called "The Universe" and they were talking about the farthest light detected by Hubble which was a galaxy about 13 billion light years away from earth, the scientist were saying that 13.7 is just the limit of what our technology can see. In a documentary called "How the Universe Works", they were talking about how the standard candle technique that they use to measure the distant of galaxies and the expansion of space may not be as accurate as thought before. I'm sure that there's much more that went into coming up with that number but I was curious as to how all of this would affect the number 13.7 billion years old.

Keep in mind that the observable universe is limited by the speed of light, and is about 50% further than the most distant visible galaxy.  The CMB is NOW about 46 billion light years away and the most distant galaxies visible are NOW about 30 billion light years away.

"...because the Universe has been expanding all this time, this galaxy isn't just 13.24 billion light years away; it's actually more like 30.35 billion light years distant."

How Far Away Is The Universe's Most Distant Galaxy? (forbes.com) 

"The Universe" and "How the Universe Works" are wonderful documentary series, although somewhat simplified for dramatic effect.  How many episodes of each of these series have you seen?  I think I've seen them all.  Are there new episodes?

Edited July 3, 2022 by Airbrush

[Kurious12]

On 7/3/2022 at 7:40 AM, Airbrush said:

How many episodes of each of these series have you seen?  I think I've seen them all.  Are there new episodes?

I believe that there are about 10 seasons now and I've only seen about 8. Thanks for the very cool and interesting article, that really clears up a lot for me.

[Airbrush]

On 7/7/2022 at 8:19 PM, Kurious12 said:

I believe that there are about 10 seasons now and I've only seen about 8. Thanks for the very cool and interesting article, that really clears up a lot for me.

Coincidentally, I saw parts of "How the Universe Works" last night.  The episode is "Birth of the Cosmos" season 10 episode 12.  That must be new.

They were talking about the first second of the big bang.  Very early, maybe before inflation, as I understood it, the Higgs Field was not in existence yet, so the Higgs Boson didn't have its' mass yet, the very early universe was massless until the Higgs Field was established, which put the breaks on the expansion of the big bang, but it already expanded so far.  I may have this wrong, but that is the impression I got from that episode.  Anyone familiar with that?