[Luigi73]

What is the age of the universe and how do we know that? ;)

[Curlyben]

It is VERY VERY VERY old, we don't know for 100% certainly, but it can be calculated.

Age of the universe - Wikipedia, the free encyclopedia

[Capuchin]

It is VERY VERY VERY old, we don't know for 100% certainly, but it can be calculated.

Age of the universe - Wikipedia, the free encyclopedia

We know within 0.8%, that's pretty good going I think.

[lalla1995]

Nobody knows the age of the universe, many scientists are searching about this topic but nobody had find out.

[Capuchin]

Nobody knows the age of the universe, many scientists are searching about this topic but nobody had find out.

No, we know quite accurately what the age of the universe is.

[DuBas07]

14.7 billion years old is the answer I come across most frequently but the general accepted time frame is 12-20 billion. They usually explain by using the rate of expansion they figured this out but a couple of questions pop up in my mind. 1) we don't know how big our universe is. 2) our rate of expansion logically had to vary in speed thus throwing off the calculation but admittedly Im not a smart man by any means.

[Capuchin]

14.7 billion years old is the answer I come across most frequently but the general accepted time frame is 12-20 billion. They usually explain by using the rate of expansion they figured this out but a couple of questions pop up in my mind. 1) we dont know how big our universe is. 2) our rate of expansion logically had to vary in speed thus throwing off the calculation but admittedly Im not a smart man by any means.

I'll try to answer the queries you have.

1) We don't NEED to know how big the universe is. Imagine you had an explosion on a sandy beach. About a second after the explosion you would only need to measure the position and velocity of a few of the sand particles in order to estimate when the explosion happened. (this isn't a perfect analogy - as the big bang wasn't really an explosion).

2) We know fairly well how the rate of expansion varied - as we have many lines of evidence that have to fit with big bang theory. For example the nearly uniform microwave background means that at some point all points in the universe had to be in thermal contact. We infer from this that there must have been a period of slow expansion for this to happen, followed by rapid expansion to drive the points out of thermal contact - we call this theory "inflation".

I hope that gave you a little taste of ways to get around not having absolute knowledge of what happened - we just make the best model that fits all the evidence.

[jrwild62]

What is the age of the universe and how do we know that? ;)

Last time I watched the Discovery channel, they said 4.5 billion. It is supposed be the halfway point. This is directly related to the big bang. It's just mind boggling how they figured out or rather 'theorized' that everything originated from a point of near nothingness. It must have been an explosion many times larger than a firecracker. Maybe even an M-80. So the universe expands in all directions for 4.5 billion years, then stops (12-21-12?? ) Then retracts back to it's original single point. Yikes, good luck with that one...

[Capuchin]

Last time I watched the Discovery channel, they said 4.5 billion. It is supposed be the halfway point. This is directly related to the big bang. It's just mind boggling how they figured out or rather 'theorized' that everything originated from a point of near nothingness. It must have been an explosion many times larger than a firecracker. Maybe even an M-80. So the universe expands in all directions for 4.5 billion years, then stops (12-21-12????) Then retracts back to it's original single point. Yikes, good luck with that one...

4.5 billion years is the age of the Earth, not the universe.

I don't think that any body thinks the Universe is going to stop expanding, in fact the universe is still expanding at an increasing rate. It's certainly not going to stop by 2012.

[ebaines]

Cap is right - best estimates for the age of the universe are about 13.7 billion years. Whether the rate of expansion is slowing, or speeding up, or remaining constant is still subject to debate. Until recently it seemed obvious that it would be slowing, as the mutual gravity attraction between all the parts of the universe should cause it to slow. However, recent measurements seem to show that the expansion is actually speeding up, perhaps powered by some mysterious "dark energy," which no one really understands. So while we know with some certainty that the universe is 13 billion years old, no one knows the universe's ultimate fate. Perhaps we are ultimately destined for the rate of expansion to slow, then stop, then start collapsing in the "big crunch.. If that's out fate, it clearly won't happen for a lot more than another 14 billion years. But if the universe always keeps expanding, then we are ultimately doomed by entropy to a cooling and dieing unverse, one where ultimately there is no more fuel to power the stars any more - call it the "big sleep." That would take many trillions of years to occur. So don't lose sleep over it. After all, as our own sun reaches its end of life it will first become a red giant and incinerate the earth. This will be long before we need to worry about a big crunch or big sleep. You have about 5 billion years left. Have a nice day!

[jrwild62]

4.5 billion years is the age of the Earth, not the universe.

I don't think that any body thinks the Universe is going to stop expanding, in fact the universe is still expanding at an increasing rate. It's certainly not going to stop by 2012.

Yes, that's right. Sorry.

[XxRoosterXx]

Thank you for the question. It gave me the opportunity to learn something new. Awesome answers also. Love this forum!