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.
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).
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
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.
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