eli5 : Why can’t science explain what happened between Os and 10^-43s after Big Bang?
In: Physics
We have sets of equations that we use when trying to explain what happens when things are very small. This is quantum mechanics.
We have a different set of equations that we use when trying to explain what happens with things that are very massive. This is relativity.
Things that are very small are usually not very massive. And things that are very massive are usually not very small. So we are usually either using quantum mechanics *or* relativity.
But some things are very small **and** very massive. Like black holes, or the conditions of the universe a long time ago.
This means we have to use both sets of equations at the same time and when we try to do this, we get answers that don’t make sense. Like infinities. This is the limit of our scientific knowledge. It represents a break down in our laws of physics and prevents us from accurately modeling these kinds of conditions.
When you hear about scientists working on things like String Theory and Quantum Gravity or The Theory of Everything, these are attempts to try and resolve or replace quantum mechanics/relativity with something that doesn’t break down under these conditions.
The main problem is that we only know the “after” state. We have no clue what “before” was like. It’s hard to explain what’s happening in the transition between Before and After if all you know is After.
We can’t take a peek into that time frame, and as far as we know nothing in the universe behaves the way now as it did back then, so we are struggling to even imagine it.
For the most part, our model breaks down, because it is sorely ignorant (along with it’s makers) of what happens at “time = 0”.
One thing is that at the dimensions of the universe at that period, we’d need a theory that unifies gravity and quantum theory. It is almost certain that our latest theories are incomplete. And it is really not possible at this time for humans to replicate the conditions of the early universe so experimental observations are not possible. One foundational principle in quantum mechanics is Heisenberg’s uncertainty principle – and that fundamentally restricts our current theories from being applied when things get too small or time periods get too short.
If you’re 5, the explanation is we can’t simulate it yet. We have an idea of how to simulate it (quantum computing) but the computers we have now aren’t good enough, it would take thousands of years.
Science: look at stuff, see it do stuff, assume it will do it again in that situation.
Big Bang: Situation doesn’t happen often
We try, but some events are rare and so our data is limited. We look at events that are similar to the Big Bang, but we need more data.
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