Normal

It's true T=0 is a placeholder, but what is stopping time from existing at T=0?

We could say anything is T=0, including the creation of earth 4 billion years ago. That does not mean time didn't exist at T=0.

By saying "Time didn't exist at T=0" you are making two assumptions which I don't think you can make.

A) Space did not exist at T=0, or space did not exist before T=0.

B) Time cannot exist without space.

For the first assumption, we have no evidence either way. Space within our universe might not have existed, but is that all the space that exists?

And explain B to me, why is it impossible to have 0 spatial dimensions and 1 dimension of time?

ex-xian

Zero is a place holder, but it is more than that. Just because it is not in the set of natural numbers doesn't mean that it isn't a number. If you admit -1 as a "number," then you have to admit 0. There is a difference between an empty set and a set that includes zero.

But here's something that I don't think anyone has brought up. Could time, going backwards, infinitly approach zero, but zero reach it?

___0(____________________>

Where time "began" at the paranthesis. But it doesn't really have a beginning, just a limit infinitly close to zero.

Normal

Provocative idea, but what are the implications?

Are you saying our universe never really "began"?

Hawkingfan

Nothing, unless it is in conjunction with the singularity. It couldn't mean anything more than the absence/non-existence of space (or "space-time"), because time didn't exist.
Right, and I'm afraid it does look like I'm making that case, but I'm really not. I'm simply saying you are wrong about time not existing at the the bb. Who cares if T=0 at the bb or not?
If YOU say that T=0 at the bb (an assumption I NEVER made), and conclude that time existed because YOU have assigned a value to T, I am saying you are wrong. So my statement time did not exist at the bb if T=0 at the bb, would be correct. I don't care if you said T=a million at the bb, time did not exist. To me, it seemed like you were saying since T=0 at the bb, that time existed then because there is some sort of value assigned to it.
Yes. The universe=all that exists. Besides, space cannot exist without particle/antiparticle annihilation.
You misunderstood me. I wasn't saying that. I'm just saying that time would have no effect at zero.

Hawkingfan

No. -1 and 0 are both "integers", but they are not both "numbers".

Normal

Where's the proof the singularity existed in 0 dimensional space?

All I did was relate the age of the universe back to the time when galaxies were a distance of 0 away from each other, and say that is the base of time that is used to gauge the beginning of the universe.

Unproven assertion, but it's all we can assume to be true, hence, Occam's Razor.

When did I deny this?

So time exists at zero spatial dimentions, but has no effect. How is this different to what I was saying about the relevancy of talking about time prior to T=0 in relation to the start of our universe?

ex-xian

Umm...yes they are. I assume you're only calling something a "number" if it is in the set of natural numbers, eg, 1, 2, 3, .... But there are many different types of numbers. Complex numbers, irrational numbers, integers, trancendental numbers, transfinite numbers.

Besides, -1, and 0 can be legitimate values. Have you taken a class in differential calculus? If so, then you should be familiar with the relationship between positive or negative values of position, velocity, and acceleration.

Hawkingfan

I have not taken a class, but I am familiar (probably not near as familiar as you). The value of x can approach zero or equal zero yes, but it can also approach infinity, no?

Hawkingfan

No proof. Where's the proof time existed before the bb?
Fine. But why would someone say "distance existed at the bb" because D=0. It's just as silly to say "time existed at the bb" because T=0. It doesn't matter. It is unreasonable to say time existed before the bb.

Hawkingfan

When you asked how we know if that is all the space that exists. If it can't exist without those particles/antiparticles, and those particles/antiparticles are compacted into the singularity, then why would you ask such a question?