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
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).
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