I’m watching How the Universe Works on the Science Channel and they said that during the period of Cosmic Inflation the universe went from being the size of a grain of sand to the size of the sun faster than the speed of light.
But they don’t say how fast that is. I can’t find any webpage that puts a warp speed of how fast cosmic inflation was.
Does anyone know how fast - in terms of warp speed - cosmic inflation happened?
I really like How the Universe Works, but that show is so badly written! It explains things either very badly or not at all.
It’s hard to define the precise speed because at that point, space was rapidly expanding. which really messes up measuring speed. And makes things look weird, like they’re moving FTL, when they’re really not.
At least that’s my limited comprehension of the phenomenon.
The reason nobody gives a speed is because there isn’t a speed. How fast it happened depends on what scale you’re looking at.
We don’t know all the details, but estimates are usually that, during inflation, the Universe doubled in size every 10^-35 to 10^-34 seconds. Estimates for the duration of inflation range from 10^-33 seconds to “infinite”, but let’s be conservative here and say that the duration was about 100 times the doubling time. That means that, during inflation, the Universe would have expanded by a factor of about 10^30.
I have no idea, but I can add to the confusion. From what I understand**, the inflation during the Big Bang wasn’t the only period of inflation. Apparently the expansion of the universe sped back up again about 5 billion years ago, and physicists aren’t sure why.
** My source is a physics podcast called Daniel and Jorge Explain the Universe. Daniel is a particle physicist at the large hadron collider.
That the speed of expansion of space doesn’t correlate well to the speed of things inside space is a concept that human brains don’t wrap well around. Worse, speed depends on a specific starting point and ending point, which also are the subjects of hot debate. A quick search will show a range of doublings, times, and every other variable. When the deepest theorists argue over concepts the rest of us need to just duck.
I just read an article in the current Scientific American that I understood as little of as you would if I tried to explain infinity-categories to you in three paragraphs. But one thing I did come away with was that there is a reason to believe that expansion was by at least a factor of e^{70}, which is something like 103 doublings.
All the previous caveats are well and good, but they aren’t very satisfying.
What we think of as the universe was probably about 0.9 mm across when inflation stopped, and a doubling took about 10^-35 s. That means that the distance between two points at opposite sides increased by 0.45 mm in that time. Dividing through, and then again by c, we get a “speed” of about 1.5x10^23 c.
“Warp speed” varies by Star Trek series, so there’s no one right answer. However, probably the most sensible one was used in TNG (though not consistently), where warp 10 was “infinite”, and warp 9, warp 9.9, etc. asymptotically approached infinity.
It’s difficult to map a multiple of light speed to this range, and the online calculators I’ve seen break down at these speeds. However, a very rough version of the formula is just V = 1/(10-W) (some small constant factor isn’t going to change much). In that case, our warp factor is roughly:
9.99999999999999999999999
I used the last doubling time before it stopped, which was the fastest one. Or, at least when it stopped in our local bubble of the universe. And our understanding of inflation is correct, and so on.
And the only reason I kept a significant digit in the “0.9 mm” figure is because it gave a clean “1.5x10^23” after dividing by the speed of light . In reality, all these figures could be off by a few orders of magnitude (or maybe more than a few). But that just adds/subtracts a few 9s to the warp figure at the end, which almost no one will notice…
I still don’t understand the problem here. Speed is distance divided by time, right? So if we know how much space expanded during the inflation (and we do – approximately), and we know how long the inflation lasted (and we do – more or less) and we know the speed of light (pretty darn accurately), shouldn’t figuring out the warp be just a matter of basic math?
We know (approximately, to an extremely loose value of the word “approximately”) by what factor space expanded. We can’t say what distance that was. If space is infinite, then the distance was infinite. If space is finite, then we’d need to know how big it is, which we don’t.
It explains things either very badly or not at all.
. In reality, all these figures could be off by a few orders of magnitude (or maybe more than a few). But that just adds/subtracts a few 9s to the warp figure at the end, which almost no one will notice…