If the big bang happened 13.8 billion years ago, and the universe is 93 billion light years in diameter, how did the universe expand faster than light?

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If the big bang happened 13.8 billion years ago, and the universe is 93 billion light years in diameter, how did the universe expand faster than light?

In: Physics

24 Answers

Anonymous 0 Comments

If we send a spaceship at the speed of light in one direction from earth, and send an identical ship at the same speed in the other direction. Aren’t they moving away from each other faster than the speed of light?

Anonymous 0 Comments

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Anonymous 0 Comments

The rule is “no known object can travel faster than the speed of light…”

Space itself however is not an object, and may bend or warp at any speed.

Anonymous 0 Comments

If you stretch space the distance between two points can be increasing even if they are not moving in space.

If all of space if stretching, two far away points can have the distance between them increasing faster than the speed of light even if neither is moving. So in 13 billion years two points far apart can spread to be 93 billion light years apart even if they are not moving.

Anonymous 0 Comments

Real answer, we don’t really know. Theoretically the simulation you are in was launched yesterday, everybody and everything else is part of it and your memories are just starting defaults.

Anonymous 0 Comments

Space can expand faster than the speed of light. There’s no law that says it cannot. This happened during the inflationary period of the universe by a ridiculous amount.

There was a very very very short period of time at the beginning of the universe called “The Inflationary Epoch”. To get an idea of how short this period of time was, the difference between the entire length of the inflationary epoch and one second is the same ratio as the difference between one second and 31,000,000,000,000,000,000,000 years (roughly). And actually it may have been even shorter than that.

During this period, the universe stretched itself out a little. The space between everything grew.

A nanometer is a very very very small distance. The difference between a nanometer and a meter is the same as the difference between 1 meter and the distance to the moon, and back, and then almost to the moon again.

During the inflationary epoch, every nanometer of distance between things turned into about 10 light years, the distance to most of the nearby stars in the sky.

At least, that’s the hypothesis. There are other hypotheses, but none that match all the data we’ve collected quite so well as this one does.

Why did the universe stretch so much so quickly? Lots of scientists spend their careers trying to answer questions like that.

https://en.m.wikipedia.org/wiki/Inflationary_epoch

I’ll end this by alighting your imagination a little bit: if space can be stretched, and can be stretched faster than light, what might happen if *we* found a way to control that stretching? Well, maybe it would let us move through space faster than light too. (Probably not, but it’s a fun idea).

Anonymous 0 Comments

Follow up question though, the diameter of the known universe is based on how far we can observe. If the universe is expanding faster than C, then how come we can observe light from 93 billion light years away?

Wouldn’t it be more logical to assume that the universe expands slower than C so light can still reach us albeit at a much longer amount of time? Just like walking up an escalator that is going down. If you walk faster than the escalator going down, you will still reach the top but at a much longer amount of time.

Sorry if this is stupid

Anonymous 0 Comments

Those numbers are just guesses. The universe might be infinite for all we know. There is no proof for the big bang and no proof whatsoever when it happened. You can say the observable universe diameter but not the whole universe.

Anonymous 0 Comments

The ELI5 answer is: We don’t know, but the Physics community has come up with a host of answers that are in some cases long winded and convoluted that (if stated concisely) means this is our best guess so far.

Anonymous 0 Comments

The Universe is actually not 93 billion light years in diameter. That’s only the *Observable* Universe, which is the portion of the Universe that is potentially observable from Earth since light would have had time to travel from there to Earth since the Big Bang. The entire Universe is much larger (at least 23 *trillion* light years across according to Wikipedia) and possibly infinite.