[nilak (OP)]

  The issue of singularities, infinities, and the "moment zero" at the Big Bang involves both space and time. In standard cosmological models, the singularity is often discussed in terms of both infinite densities and the nature of time. But let?s break it down:

    Moment Zero and Time:
When we talk about "moment zero" at the Big Bang, we?re also talking about the beginning of time itself (at least in the standard interpretation). If there?s no past?no "before" the Big Bang?the concept of time itself becomes tricky. Theories like general relativity describe time and space as interconnected (spacetime), and at the singularity, spacetime itself is said to "break down."

In general relativity, when you rewind the clock, spacetime curvature increases, and at moment zero, this curvature theoretically becomes infinite. This is part of why singularities appear, because we?re dealing with spacetime itself, not just density.

 Is the Infinity from the Moment Itself?
If we were to stop at "moment zero" without extrapolating past it (since there?s no past), the issue isn?t purely about density. The problem lies in how our equations treat spacetime. The closer we get to moment zero, the curvature of spacetime increases, which also suggests that all distances and intervals shrink to zero, leading to these infinities.

So, even if we don't think in terms of infinite density, at moment zero, general relativity still predicts infinite curvature of spacetime and the breakdown of time itself into meaningless intervals. This breakdown doesn?t only come from densities or temperatures, but from the way time and space behave under extreme conditions in the early universe.

  Can This Be Avoided?
Many modern theories of quantum gravity (which would combine quantum mechanics and general relativity) attempt to avoid this issue by proposing that spacetime is "quantized" at small scales. This could prevent both infinite densities  and the singularity in spacetime at moment zero. In these models, time could have a smallest unit, meaning the universe starts at a finite, but very small, moment.


- The infinities at moment zero come from both the way time and space behave according to general relativity and from density extrapolations.
- If we stop at "moment zero" in a more finite, reasonable way (as some quantum theories suggest), the infinities could be avoided altogether.


Here is a. hypothesis that touches on the peculiar nature of light and time. The idea that at the moment of the Big Bang there may have been only photons (or radiation) and no time in the way we usually understand it connects with the nature of how light interacts with spacetime.

    The Nature of Light and Time:
Photons, or particles of light, travel at the speed of light, and according to special relativity, time doesn't pass for objects moving at that speed. From a photon's perspective, the distance between any two points is contracted to zero, and the time it takes to traverse that distance is also zero. In other words, a photon traveling through space experiences no time at all.

So, if the early universe were dominated by photons (or radiation) immediately after the Big Bang, this suggests something quite unusual about time and spacetime. From the photon's point of view, the moment it was created and the moment it interacts with matter (or anything else) would be effectively simultaneous.

     What Could This Mean for Moment Zero?
If we consider the idea that at moment zero there were primarily photons (or perhaps a very dense form of radiation), the concept of time may become ambiguous because of how photons experience spacetime. This could mean:
- Time is not well-defined. If the universe were made entirely of photons at moment zero, then time as we experience it, which is deeply tied to the motion of massive particles, might not have existed in the same way. The passage of time, at least for photons, is irrelevant.
- A timeless state at the Big Bang: If the early universe was in a state where radiation dominated, it might have been a "timeless" state in some sense?time might only emerge as the universe cools down and particles with mass begin to dominate, leading to the expansion of spacetime as we know it.

     Photon Dominance in the Early Universe:
In fact, the early universe  was radiation-dominated for a very short period after the Big Bang. Immediately following the Big Bang, the universe was filled with extremely high-energy radiation (photons), and only later, as the universe cooled, did particles with mass start to form, creating a more familiar spacetime structure where time passes for massive objects.

   Weirdness of the Early Universe:
This photon hypothesis underscores that something strange indeed happens around the moment of the Big Bang. It could imply:
- Time, in the conventional sense, may not have existed as we understand it at the Big Bang.
- The very nature of spacetime, and whether time "exists" for light, could give us clues about the origin of time itself.
- The moment zero might not be a moment where time begins but rather where the conditions (such as mass and the emergence of spacetime curvature) allow time to begin.

Quantum Theories and Time Emergence:
Some quantum cosmology models suggest that time itself is an emergent property, meaning it only appears as a meaningful concept after certain conditions in the universe are met. In these models, before the Big Bang (or at the moment zero), the universe might exist in a timeless or even spaceless state. Once particles with mass appear and the universe expands, time as we experience it begins to make sense.

  Summary:
    The fact that photons do not experience time can mean that the early universe might have been in a very different state from what we currently understand, where time, as a concept, didn?t exist or was not well-defined. Time may be intimately tied to the matter and energy content of the universe, and may not even have existed in the earliest ?moments?.We can view it as  an initial expansion that since it takes no time, the moment zero begins with an already vast volume filled with light and the first ever particles.

[Eternal Student]

Hi.

Did you want a discussion,  some appraisal of what you've written, just some place to display your thoughts .... or something else?
If you want an appraisal or discussion there's quite a lot of positive things that could be said but would you also want any negative comments?    The main thing is, you've got an interest in physics and that's a good thing.   Saying something that puts you off the topic is clearly not a good thing that we should do.   Spend a moment thinking about what you want from this forum and let us know.

Best Wishes.

[nilak (OP)]

I was interested in any thoughts about the moment zero since fractions of seconds later things have been fairly explained

[Eternal Student]

Hi.

      We would seem to be in uncharted territory at what you call moment zero, based on the theory of General Relativity (GR).  We may need some sort of new science and/or some new language to discuss it.   Most of our language hinges around concepts of space and time - which may not be there.
     
      Mainstream science is currently working under the assumption that GR is just an approximation.  As you imply in your original post, we may need some other theory for these extreme situations.   In this respect the early moment(s) of the universe probably aren't as GR describes.   With some luck it'll be even more bizarre but it may be quite simple and ordinary.

Best Wishes.