Was the first picosecond really a picosecond?

[gib65]

I am told that scientists don’t know what happened within the first picosecond of the universe.

 

If this is true, I have a question:

 

How do they know it was a picosecond? I guess the assumption is that if you extrapolate the current expansion of the universe back to its origin, you don’t have to assume anything unusual in the first picosecond. But what if scientists could somehow see into the first picosecond? Is it possible that what they find is that it was way longer than a picosecond? In other words, the universe originally started expanding very slowly, and for the longest time didn’t grow much bigger than its original size, and then for some reason went through the explosive expansion scientists are familiar with?

[Strange]

7 minutes ago, gib65 said:

How do they know it was a picosecond? I guess the assumption is that if you extrapolate the current expansion of the universe back to its origin, you don’t have to assume anything unusual in the first picosecond.

That is roughly right. If you extrapolate back using the physics we currently know, there is a "time 0" when everything appeared to start.

The trouble is, we know that none of our theories tell us what happened at the very earliest time (much less than a picosecond) because the conditions become so extreme. So we probably need a theory that combines quantum theory and general relativity (among other things).

10 minutes ago, gib65 said:

Is it possible that what they find is that it was way longer than a picosecond? In other words, the universe originally started expanding very slowly, and for the longest time didn’t grow much bigger than its original size, and then for some reason went through the explosive expansion scientists are familiar with?

There are a number of different models that try to explain what happened.

One attempt to combine GR and quantum theory, seems to describe exactly what you say: an infinitely old universe that then expanded. https://arxiv.org/abs/1404.3093

[gib65]

Thank you Strange,

What is the earliest that scientists can "see" the state of the early universe? I mean, I know scientists can look at the early universe by observing the CMBR in deep space, but this happened much after the first picosecond. Can they actually "look" that far back, to the first picosecond, or is it all based on mathematical models at that point?

[beecee]

2 hours ago, gib65 said:

Thank you Strange,

What is the earliest that scientists can "see" the state of the early universe? I mean, I know scientists can look at the early universe by observing the CMBR in deep space, but this happened much after the first picosecond. Can they actually "look" that far back, to the first picosecond, or is it all based on mathematical models at that point?

The LHC and other particle accelerators give us a good idea as to what the early universe back to t+10-43 seconds may have been like. That along with mathematical models, and reasonably logical assumptions such as the ffour known forces, all being combined as one, known as the "superforce". The degree of certainty that scientists are correct does diminish though the further back to that t+10-43 seconds period we approach.