> If time effectively halts at T0, then what possible event could occur (outside of time?) to nudge that infinitely large glob off mass into the motion we observe today?
Anthropic principle explains it. If you need a Prime Mover, you can also replace it with Anthropic principle and random chance.
For example if time halts at T0, physics breaks. Using limes when t->0 you get that v-> Infinity (or c). Slower time moves for you, faster you move in space. At that point, if nothing is there to detect it, every massless particle will be effectively everywhere, all at once. Essentially photons can have Infinite energy and just cause a random Big Bang. This is CCC like explanation.
Another answer is Hawking's North of North Pole time problem (from Universe in a Nutshell). If time halts a T0, you can't ask what's before it. It's just logical impossibility. Like what is North of North Pole? Answer is: Question is invalid. Anthropic principle implies there are however many multiple such configuration so you get a parallel or sequential universe solution.
We arise and wonder how exactly Universe exists that support life, even if we can clearly see, it's only supporting life at this moment. Our existence is a grain in the sand of a universe-sized sand clock that will be the Black Hole epoch.
The universe advanced from T0 because it had to, by definition.
If this seems like a weird cop-out, well, that’s a singularity for you.
Yes.
If you assume that all events have causes.
Our understanding of the world (aka science) is largely based on causality, and if things existed without any cause or reason, our understanding of "science" would probably be very different.
(I'm not a physicist, but this is how I understand things.)
Also, no one is "lazily tossing it aside". It comes out of the mathematics that describe the observations:
Say you find that all observations you make are perfectly described by dx/dt = 1/x with current time t1. If you follow the trajectories backwards, you find that the trajectory can not be extended back past some initial time t0 at which x(t0) = 0 as the equation becomes singular then. You are now at time t1-t0 from the initial singularity. That is the age of the universe since the big bang. Now the trajectory as it approaches t0 has some unusual properties, it moves infinitely fast, etc... These might lead you to postulate that unknown physics will actually invalidate your law as you approach t0. But there is nothing logically or epistemically _wrong_ with the law you have. The finiteness of time flows out of a causal empirical induction argument. It is not introduced ad hoc to avoid some difficulty, it just is how we find nature to be at the most conservative interpretation of the evidence.
You stop at the uncaused first cause or the unmoved mover, of course.
Think of it like a particle decaying - at some point it just happens with no trigger or internal mechanism, and now you suddenly have the decay products wizzing about with some energy and momentum that they just start with.
There is no reason to assume that everything has a cause. It is perfectly logically consistent to have things without cause in the universe.
The big bang could not create universe from nothing, it could only spread matter from a singularity into ever expanding universe (time-space).
is it even possible, to have entirety of universe matter and energy in a single point?
We don't know anything at all about the physics of infinitely small spacetimes, because we don't have a fundamental physics of spacetime at all.
GR is a descriptive approximation of the behaviour of spacetime, but says nothing about the fundamentals that generate that behaviour.
There are proposals for time stretching infinitely back, but we have almost no way of testing them.
And since we know that gravity affects the rate of flow of time, wouldn’t the rate of time be enormously distorted earlier universe?
I’m not trained in any of this, so hopefully there are greater minds here who can help me understand
So there must have been a time when electromagnetism, the weak and even the strong force just didn't exist. They couldn't. So particles would just have totally ignored those forces.
We don't know if gravity is the same, but ... why wouldn't it. Though of course according to relativity gravity just wouldn't care, but that just raises a lot more questions than it answers.
What does it mean to compare ("faster") a velocity and a frequency (inverse time)?
The issue is that movement and time are fundamental to the universe, yes, in the way relativity describes but also in a totally different unknown way. In some ways particles are "just" things moving relative to one another. Which, for one thing, brings the perspective question (if you accelerated to a "real" speed, would you see a different universe? Because you would disagree with us slowpokes here on earth on what particles exist at least in some cases. But would you see an entirely different universe?)
As I understand it, that’s an approximation for Euclidean space because the area of a sphere is also proportional to the square of the radius in such a space, but it’s not true of non-Euclidean spaces like in GR because the area-radius relation is different.
IIRC, the cosmic microwave background has a gamma factor of about 1100, so the area of that shell is the same as one 1100 times closer or 1/1100^2 times the area as a Euclidean sphere with that radius.
> And since we know that gravity affects the rate of flow of time, wouldn’t the rate of time be enormously distorted earlier universe?
Time did indeed slow down then compared to now, although it’s not entirely obvious to me that this has any physical interpretation when it happens “everywhere”: https://youtu.be/66V4RSmDqYM
Well... yes it is, in the rigorous sense of "time" defined by general relativity. There's no "before" for a singularity. It may not be the whole story, but whatever metaphysical notion defines the "before/beyond/outside/why" that drives the big bang, it's not a place on the "time" axis of spacetime.
Similar to the singularities in black holes - everything up to a stone's throw of the event horizon is pretty well explained by GR, but as far as the horizon itself or the region beyond are concerned, there might be dragons as far as we know.
I don’t think that’s right. If we interpret Big Bang theory as claiming that there is a singularity at a finite distance into the past history of every present event, then GR can’t predict what happened at or prior to that singularity. Whether time “began” then or whether there was “more time on the other side” is a question GR alone cannot answer, not a prediction of GR
[1] https://en.m.wikipedia.org/wiki/Fuzzball_(string_theory)
How does that work for black holes? It seems like there would be a 'before' they formed in the time dimension of our universe, if not within the singularity itself.
At least what we currently spend most of time studying/researching in physics right now. We can hope to expand beyond that given enough time.
There might literally not be enough time to expand beyond that, given how cosmological horizons work. Being part of the system we're trying to observe puts some nasty limits on what we can know, even in principle.
Which is to say that there exist respected papers that outline this scenario in great detail, but there’s precious little observable evidence of a previous universal cycle.