# What is the age of universe? [closed]

As we know at the time of big bang as mentioned by the scientist the universe expanded faster than the speed of light. So does it mean that at that time all the particles present travelled in the time and the age of universe is different from what we know today or scientist have calculated the age keeping the phenomenon in consideration ?

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## closed as not a real question by Manishearth♦Mar 10 '13 at 7:00

It's difficult to tell what is being asked here. This question is ambiguous, vague, incomplete, overly broad, or rhetorical and cannot be reasonably answered in its current form. For help clarifying this question so that it can be reopened, visit the help center. If this question can be reworded to fit the rules in the help center, please edit the question.

I don't understand what you are asking. Can you elaborate and/or rephrase? –  zhermes Mar 10 '13 at 3:23
we know that if we travel at 99.99% of speed of light we start to travel in time that is time become slower for us and it is said that at the time of big bang universe expanded at a speed greater than the speed of light so does it mean that universe also travlled in time and it's age is different –  Akash Mar 10 '13 at 3:27
Amidst of the many partial theories, Big Bang is also one of the suggested theories to describe the observable universe. Many others support the existence of such a singularity in the past. So, we presume time had a beginning at the instant of big bang because going into past is not gonna do so much good rather than confusion. So, it is just about 14 billion years old. I'm slightly suspicious that you're thinking about: "Would the expansion of universe faster than $c$ make us look into the past??" - I think you may find an answer in CMB –  Waffle's Crazy Peanut Mar 10 '13 at 3:34
How could it be that time didn't exist before the big bang as that thing which exploded would be in some space –  Akash Mar 10 '13 at 3:48
Your question is quite confusing, could you elaborate it? In the meantime I'll keep this closed. –  Manishearth Mar 10 '13 at 7:00

## 1 Answer

The Big Bang occurred about 13.7 billion years ago. This number refers to the time experienced by a co-moving observer - that is, an observer who is moving along with the general flow of matter in the universe throughout its history. Since the universe is homogeneous on the large scale, it doesn't make a difference just where you consider this notional observer to be - co-moving observers everywhere would have measured about the same amount of time since the Big Bang. In that sense we can speak of a consistent age of the universe.

The universe did not "expand faster than light". It's true that if you pick two widely separated points, the distance between them is growing at a rate faster than lightspeed. But this expansion happens everywhere at once, uniformly throughout all the space between the two points, and any matter or light in that space just gets carried along with the stretching. The rate of expansion seen between two points is proportional to how far apart the points are to begin with (that's Hubble's law), so it doesn't make sense to say that the whole universe is expanding faster than light - or at any other particular speed.

The right mental image to think about the expansion of the universe is that of stretching a rubber sheet or blowing up a balloon. Imagine drawing dots on the rubber with a marker pen, then stretching it out - the dots get farther apart although each one stays in exactly the same place on the rubber. It's not that the dots are moving, but that the rubber between them is stretching. The dots represent stars or galaxies and the rubber represents space.

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