I watched this youtube vid recently. You might like it.

https://www.youtube.com/watch?v=uD4izuDMUQA

Choice of words is nowhere more important than in philosophy and science. I maybe completely wrong but I've never heard/read the claim "the universe was created 13.8 billion years ago". What I'm familiar with is, "the universe began 13.8 billion years ago". Perhaps my memory fails me. I do recall people claiming time and space were "created" at the Big Bang.

I like this MinutePhysics video with Sean Carroll: https://www.youtube.com/watch?v=yKbJ9leUNDE. He gets straight to the point, explains in simple terms the (basic) nature of time, and gives an overview of how the universe started and how it's supposed to end. Sean Carroll also proposes an idea (don't know if it can be called a theory or not) in other videos you can easily find on Youtube that quantum fluctuations in empty space may satisfy conditions to initiate a Big Bang, basically beginning a new universe in the death of a previous one.

Yes, scientists don't say that the universe was "created" at the Big Bang, but it is commonly said that matter can't be created or destroyed, which is the only context I see Benj96 using the term.

The first law does not hold on a cosmological scale. Even right now new energy is being created everywhere, which drives the accelerating expansion of space.

The first law does not hold on a cosmological scale. — Pfhorrest

This.

Conservation of energy is, per Noether's Theorem, a consequence of time translation symmetry. At cosmological scales time translation symmetry breaks down and, as a consequence, so does energy conservation. I won't speculate much more than this... but here's a good explanation from Nick Lucid of science asylum:

https://www.youtube.com/watch?v=cnGYMe6GBeQ

The first law does not hold on a cosmological scale. — Pfhorrest

Only holds for closed systems. If you consider the Earth apart from the sun, it gains energy constantly. If you put the sun back in, the sum of energy asset and liability goes to zero.

Yes, scientists don't say that the universe was "created" at the Big Bang, but it is commonly said that matter can't be created or destroyed, which is the only context I see Benj96 using the term. — QuixoticAgnostic

Oh. Thanks for the info. I just remembered something. Many top-notch scientists have publicly confessed about their complete bafflement regarding the question: why the universe was in a low entropy state at the beginning? Do you think this has anything to do with the OP? In my humble opinion, the universe's "creation" for a scientist is not that matter and energy were brought into existence at the Big Bang but is actually the evolution of a system from low entropy to high entropy.

Another way science can be consistent about this is to admit that neither energy nor matter has been created or destroyed in the sense that all energy-matter in our current universe is no more and no less than that contained in the Big Bang singularity but the universe doesn't refer to this total energy-matter but rather to the configuration of energy-matter that is new - different from the Big Bang singularity - and so was created.

It's something like jigsaw puzzle - there are as many pieces in the beginning (before the puzzle is solved) as there are in the end (after the puzzle is solved) - mass-energy conversation - but the configuration of the pieces is new and thus can be thought of as created.

I haven't heard of Sean Carroll, but that sounds like an interesting video, so thanks for the share, QuixoticAgnostic. I have only the most basic grasp of the question of space, time, and the origin of the universe so I don't think I can offer much to the original question.

My largest uncertainty is not understanding what space-time is. If I think about it, it rather sounds like we are describing trajectories. Space... doesn't seem to exist. Does it? What is space? It's simply a dimension as far as I can tell (ie distance, relationship etc). Time is a measure of change. Time depends on matter, in a sense so does space. So wouldn't space-time just be a measure of change in the trajectories of objects?

If we had an infinite space with no matter at all, we couldn't describe that as a "space" (ie there are no dimensions). With no spatial or temporal dimensions, it isn't anything at all, yet it would be infinite. Which suggests that the energy available is infinite, yet unmeasurable until matter exists (after which the dimensions of time and space also exist and can be measured).

So the void or the energy potential is sort of effectively infinite in both dimensions but a universe only exists while there is matter. So the answer to the question is that there is a beginning and an end to the universe, but the energy potential remains infinite.

Does that make any sense?

My largest uncertainty is not understanding what space-time is. If I think about it, it rather sounds like we are describing trajectories. Space... doesn't seem to exist. Does it? What is space? It's simply a dimension as far as I can tell (ie distance, relationship etc). Time is a measure of change. — Graeme M

Time is often defined as change but this is a weak definition; change is evidence of time but not a definition of it. (Space)time is a geometry according to which change happens. That is, time is the way change happens; it is the order according to which change happens. In physical spacetime general relativity describes how change happens. G.R. describes the geometry of time and how things happen in it. That geometry is time.

True story. Back in the 60s - that's the 1960s, not the 1860s - I was an under-grad Physics major. Thermodynamics was not on the undergrad curriculum. To compensate, the department had one of the professors give an optional lecture on the Laws of Thermodynamics.

At the end, during the Q&A period I asked how it was that the universe had such a low entropy value. The professor's response??

"When God created the universe he created the Second Law of Thermodynamics"

The whole class laughed.

Just for the record, I have no religious beliefs. And I also was - and still am - a very mediocre Physicist.

The first law states that energy can not be created or destroyed. So everything (=energy/ God/ love) will exist forever.

Intesting, I think change is a fine definition of time.

I’m not a physics major or anything like that, but I find it fun to think about these things. It’s true that the only way to really observe time is through change. However rather than the changes being time, I like to see time as a universal law that allows for movement. Without movement there is no true indication of time. In reference to the initial thread, I think the universe could have a been an one-dimensional point, but “after” time came to be, movement also became possible. Energy is mass multiplied by speed(of light squared) and speed only exists when time does. In other words all that mass in the point suddenly had energy and walla, big bang. This is all from the perspective that there was a “time” before time.

At the big bang, current hypothesis is quarks and Neutrinos were created.They lost electrons because of the cooling. This created H3 the building block of the universe. Both matter and antimatter were created. Our universe has more matter and antimatter. Black holes are antimatter. We are all made of stardust. the universe is still expanding. Will it expand forever? Does energy exist in black holes?

At cosmological scales time translation symmetry breaks down and, as a consequence, so does energy conservation. — InPitzotl

It breaks down in the sense that in a dynamic, curved and possibly infinite spacetime there is no uniquely correct way of calculating and keeping track of the total energy. Physicists don't seem to be much bothered by that though, because energy is mostly useful as a budget in local transactions.

True story. Back in the 60s - that's the 1960s, not the 1860s - I was an under-grad Physics major. Thermodynamics was not on the undergrad curriculum. — EricH

Wha...? What was on the curriculum?

At the end, during the Q&A period I asked how it was that the universe had such a low entropy value. The professor's response??

"When God created the universe he created the Second Law of Thermodynamics" — EricH

Well, that's a crap answer and not even a good joke. The past hypothesis, as the (supposedly) low initial entropy of the universe is known (after David Albert), is an interesting and contentious issue.

Wha...? What was on the curriculum? — SophistiCat

Hard to re-collect - that was 50 years ago. For whatever reason, even tho I was a physics major, it was a liberal arts degree - I took Philosophy 101/2, World History, French Literature, Art History, etc.

Well, that's a crap answer and not even a good joke. — SophistiCat

It was funny at the time. Guess you had to be there . . . . . .