# Curious about the age of the Universe

## Main Question or Discussion Point

Ok first off, its nice to meet you all.

Second, my knowledge of physics is limited to 5 seasons of The Universe on Netflix. :uhh:

This will be my only question though so bare with me. Physicists seem to be SURE (at this time at least) about the age of the universe being around 13-14 billion years old. The way they arrive at this is by running the camera backwards so to speak and using known variables like the speed of light to calculate the age... more or less (right?). So, this is going to be in layman's terms but, if the universe is expanding and light is traveling, at light speed, across the universe then couldn't that throw off or skew calculations? Or what if time itself is slowing down on a universal scale as it cools and expands and we can't tell because were inside it, like being inside the edge of an event horizon... What I'm getting at is, couldn't there still be unknown variables that could greatly influence/change our idea of how old the Universe is? Or are you guys really THAT positive about it?

Thank you for any advice. I'm gonna go watch some more Netflix now.

mfb
Mentor
The way they arrive at this is by running the camera backwards so to speak and using known variables like the speed of light to calculate the age
Something like this can be used to calculate the age of the universe, right. It is not the only method.
The expansion of the universe and its acceleration is taken into account in those calculations.

Or what if time itself is slowing down on a universal scale as it cools and expands and we can't tell because were inside it
Slows down relative to what? Time is something happening in our universe, it cannot "slow down". In a similar way, if you measure your own height in units of your own height, you always get 1, regardless of your size.

What I'm getting at is, couldn't there still be unknown variables that could greatly influence/change our idea of how old the Universe is? Or are you guys really THAT positive about it?
Well, the universe could have an age of some days or not exist at all. But apart from those weird (and interesting!) concepts, scientists are highly confident that the universe was very hot and small (compared to today) about 13.7 billion years ago. It might be older, but something like the big bang occured at this time.

Muriel777, there are many different theories about the age of the universe, and yes there is a theory that takes in to account the expantion of the universe. I have found that carmelian cosmology explains this well, however you must remember not to take any theory as fact as many seem to think of the big bang theory, not that I want to turn this in to a debate.

for farther reading look up carmelian cosmology if you are really in to this sort of thing.

This will be my only question though so bare with me. Physicists seem to be SURE (at this time at least) about the age of the universe being around 13-14 billion years old. The way they arrive at this is by running the camera backwards so to speak and using known variables like the speed of light to calculate the age... more or less (right?).
Not really. There are several different ways of giving the age of the universe and all of them seem to give the answers. This is important because if we really got something majorly wrong then we wouldn't expect the same number from several different methods.

Also, for the age of the universe, there is a limit that the universe must be older than the oldest thing that we can find. If we found a star that appeared to be 20 billion years old (and we have computer simulations that show what a 20 billion year old star should look like), then we'd have to rethink thing.

For a few examples of things in the universe, we can get a guess for the age of the universe from how quickly stars burn hydrogen, for how much radioactive elements are there, for how old galaxies are, for how quick white dwarves cool. Etc. Etc. These are just a few of the ways we can date things in the universe, and they all give numbers that are less than 13 billion years old. The oldest galaxies are about 10 billion years old, and if you leave some time for galaxies to form that gives you 13 billion years.

So, this is going to be in layman's terms but, if the universe is expanding and light is traveling, at light speed, across the universe then couldn't that throw off or skew calculations? Or what if time itself is slowing down on a universal scale as it cools and expands and we can't tell because were inside it, like being inside the edge of an event horizon... What I'm getting at is, couldn't there still be unknown variables that could greatly influence/change our idea of how old the Universe is?
Most of the measurements that date the universe has a self-check. For example, one piece of evidence for the age of the universe is looking at the microwave vibrations in the background radiation. So you set the universe at specific ages and you calculate a pattern.

Now let's suppose we got things *really* wrong, in that case what we would see would likely look nothing at all like the patterns in any of our calculations. The fact that we get something that fits one of the patterns suggests that there isn't an huge unknown factor.

Or are you guys really THAT positive about it?
There's levels of certainty. I wouldn't bet my life that the universe was between 13 and 14 billion years old, but I would bet US\$50,000 on it.

One thing that I'd like to make clear about cosmology is that there is a lot of "common sense" involved. Suppose you have a watch that you think might be broken, how do you tell? One way is go find an independent way of finding the time.

Another way is to do an experiment that has a self-check. If you look out and you see the sun, you can guess that it's day time. If you look out and see the moon and the stars, then you can guess that it's night. If you look outside, and the sky is purple and you see five moons and two suns, then you know that something really weird is going on, and that there is a basic assumption about the world that you made that is wrong.

phinds
Gold Member
2019 Award
... my knowledge of physics is limited to 5 seasons of The Universe on Netflix. :uhh:
Just as a friendly word of warning, you are NOT learning actual physics on that program and you will in fact be badly misinformed on many occasions. They present popularizations of physics concepts and information and sometimes in an apparent effort to "dumb it down" for a wide audience, they get it basically wrong. Even well-known physicists who appear on these programs do the same. There are numerous threads on this forum decrying the sorry state of popularizations and popularizers. Michio Kaku is particularly singled out as presenting bad science but he's hardly the only one.

I watch lots of these physics TV programs because they are entertaining and usually have terrific graphics and photography, but I REALLY wince from time to time at the boneheaded statements they make.

Just as a friendly word of warning, you are NOT learning actual physics on that program and you will in fact be badly misinformed on many occasions. They present popularizations of physics concepts and information and sometimes in an apparent effort to "dumb it down" for a wide audience, they get it basically wrong. Even well-known physicists who appear on these programs do the same. There are numerous threads on this forum decrying the sorry state of popularizations and popularizers. Michio Kaku is particularly singled out as presenting bad science but he's hardly the only one.

I watch lots of these physics TV programs because they are entertaining and usually have terrific graphics and photography, but I REALLY wince from time to time at the boneheaded statements they make.
Haha yea, whats popular is rarely ever the most correct. Thanks for all of your replies, I didn't expect such a nice response. Its much appreciated. My main curiosity revolved around "when" we figured out the universe was expanding (now we know the actual space between galaxies is expanding, which is pretty crazy) and whether that was figured into the 13-14 billion year estimate. Keep up the good work!

phinds
Gold Member
2019 Award
Muriel777, there are many different theories about the age of the universe, and yes there is a theory that takes in to account the expantion of the universe. I have found that carmelian cosmology explains this well, however you must remember not to take any theory as fact as many seem to think of the big bang theory, not that I want to turn this in to a debate.

for farther reading look up carmelian cosmology if you are really in to this sort of thing.
Uh ... REALLY? I checked out Carmelian cosmology briefy and it sure looks to be way out in la-la land.

EDIT: Jathor, you should check out https://www.physicsforums.com/showthread.php?t=627796 --- I almost got a forum infraction for even MENTIONING such a crackpot "cosmology"

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Chronos
Gold Member
... The oldest galaxies are about 10 billion years old ...
Actually, any galaxy with a redshift above z ~ 1.8 would be over 10 billion years old. Galaxies in the 12.5 billion year age range [Z>5] are well documented, and galaxies in the 13+ billion year old range have probably been detected - e.g., http://www.msnbc.msn.com/id/47774230/ns/technology_and_science-space/t/hawaii-telescope-sees-what-could-be-oldest-galaxy/ [Broken]

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Chalnoth
What I'm getting at is, couldn't there still be unknown variables that could greatly influence/change our idea of how old the Universe is? Or are you guys really THAT positive about it?
With the amount of data we have today, it's difficult to imagine what those unknown variables could possibly be. Changes in the model we use to describe the universe tend to only change the inferred age by about 200 million years or so, if they fit the data at all. At this point, a significant change in the inferred age would require a dramatic rewriting of much of physics, which is highly unlikely.

Chronos
Gold Member
If the universe is cyclical, as some scientists suspect, it could be infinitely ancient, but, the age of the current observable universe is definitely finite. Were this not true we should see stars and galaxies composed of stars that have expended all of their energy and become cold, black cinders. In fact, there would be no reason for any star in the sky to not be a cinder if the universe was more than a trillion or so years old.

Chalnoth
If the universe is cyclical, as some scientists suspect, it could be infinitely ancient, but, the age of the current observable universe is definitely finite. Were this not true we should see stars and galaxies composed of stars that have expended all of their energy and become cold, black cinders. In fact, there would be no reason for any star in the sky to not be a cinder if the universe was more than a trillion or so years old.
The existence of the CMB is also pretty hard to understand in the context of an eternal observable universe. I'd also like to point out that it is not only in a cyclical universe that you might have an infinitely-ancient universe while our observable region remains finite. Some infinitely-inflating scenarios also have this feature.

Hi.

Yes, physics probably breaks down at Planck scale, when distances become comparable to Planck length. Why? Any particle smaller than Planck length slips into singularity, because Planck length is event horizon for elementary particles. See, for example http://en.wikipedia.org/wiki/Planck_length. It is shortest distance that can be measured. So when universe was that small, if ever, back then there was some weird physics at work. So, the answer to Your question - could we be wrong about our notions on the age of universe - has a definite answer: we know exactly that something is wrong at Planck scale. However, we are pretty sure we got everything happening after cosmos broke out of Planck scale egg right.

Cheers.

The evidence seems pretty conclusive that 13.7 billion years ago an event took place we call the big bang but I wouldn't say they have proof that the universe in its entirety is only 13.7 billion years old. Because time and space are interwoven there is a presumption that before the big bang there was no space and therefore no time, however I have never seen anybody describe the instantaneous creation of all 3D space and therefore fail to see how they can date the universe. The limitations of physics prevent them knowing anything about the state of the universe prior a unit of one Planck time.

That said I think its fair to say most scientists would be pretty confident to make a cash bet that our observable universe is around 13 to 14 billion years old but I doubt they would be confident bet their life it wasn't any older :tongue2:

The existence of the CMB is also pretty hard to understand in the context of an eternal observable universe.
It turns out that the *mere existence* of a CMB isn't conclusive proof of finite universe. The steady state models could create a CMB from extremely distant galaxies. Now the CMB as we see it (i.e. very close to black body), precludes an eternal universe, but if took a few years after Penzeias and Wilson to really nail that coffin shut.

Hi.

Hawking, among other physicists, theorized that universe might be curved in higher dimension in a torus-like geometry. When at Planck scale, particles tunnel through a wormhole into higher dimensions or some similar fantasm, and there is actually never a singularity. Universe now looks like a bike tire, in higher dimensions. This is what one would expect having Heisenberg uncertainty acting at Planck scale.

This sounds a bit exotic to me, though.

Cheers.

Twofish, Do you have any pointer to papers / articles that discuss the difference between a call"distant galaxy" CMB versus a blackboard / big bang (or why the CMB isn'tfrom distant galaxies)? I haven't come across this myself and would be very interested to read about it.

Regards,

Noel.

the universe is probably multi-dimensions, unlike what's been proposed by the big bang?
does anyone really know its age?

i've been watch some star trek movies, i.e. voyager, and it's very interesting that spaceship could travel faster than light, i.e. warp speed and transwarp speed :)

if in reality is that nothing can travel faster than light, then there should be no way to time travel, unless you go through a dimension?

Drakkith
Staff Emeritus
the universe is probably multi-dimensions, unlike what's been proposed by the big bang?
does anyone really know its age?
We have no idea if there are other dimensions. The only evidence we have is for 1 universe so far, so we definitely can't say that there are "probably" other dimensions. The age of the universe is approximately 13.6 billion years old.

i've been watch some star trek movies, i.e. voyager, and it's very interesting that spaceship could travel faster than light, i.e. warp speed and transwarp speed :)

if in reality is that nothing can travel faster than light, then there should be no way to time travel, unless you go through a dimension?
Time travel isn't really believed to be possible by most professional scientists. And since we haven't observed it happening we can't say when we can do it and when we can't. Furthermore time travel is not allowed to be discussed per PF rules, as it very quickly gets out of hand since there are practically no rules regarding it. (Because it is an unobserved highly speculative subject that pretty much makes no sense)

Hi.

There exist solutions for wormholes in general theory of relativity, theoretically only, of course, and those are unstable, at very tiny length scales, evaporate too quickly, require exotic matter and exotic effects, such as Casimir effect, to operate, and are not quite well established theoretically yet. There is a brief introduction to this subject on Wikipedia, of course, aimed at broader audience: http://en.wikipedia.org/wiki/Einstein-Rosen_Bridge. So, there isn't much to say, because of lack of full theoretical support, plus, we are very very far away from observing a wormhole experimentally.

Cheers.