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How big is the Universe and When is the beginning o Time





therimalaya
I'm currently reading the Book of "The Universe" from Stephen Hawkins. I'm on the second chapter. I'm wondering about the Universe, How big is it. Is is infinite? If it is finite, what is beyond it, Is there another universe? How all these stuffs started? Or is these only the consequence of our perception and are illusion in reality? What about time? Is it an object or some phenomena? Can we go backward or jump into some point in Future?

I'm very confused? I am waiting for some good discussion on this matter in this forum?
badai
How big is it?
the observable universe is a sphere with a radius of about 46 billion light years. beyond that, you can't measure what you can't see.

Is is infinite? If it is finite, what is beyond it, Is there another universe?
again, you can't measure what you can't see. you won't know what you can't see and measure.

How all these stuffs started?
big bang

is these only the consequence of our perception and are illusion in reality?
illusion is what our brain think it is, but it isn't. obviously, the universe is something not only we can sense, but can be measure by experiment. and those device used on any experiment is inanimate without awareness and consciousness. they don't have any perception.

What about time? Is it an object or some phenomena? Can we go backward or jump into some point in Future?
on macroscopic level, it just a concept for us human to measure lapse. like imaginary number, so you can tell how long and when.
on microscopic level, it's tied together with space, so i guess if you are a cute little neutrino, sure, you can jump off any when you want.
read his previous book, brief history of time to understand.
ocalhoun
therimalaya wrote:
I'm currently reading the Book of "The Universe" from Stephen Hawkins. I'm on the second chapter. I'm wondering about the Universe, How big is it. Is is infinite? If it is finite, what is beyond it, Is there another universe? How all these stuffs started? Or is these only the consequence of our perception and are illusion in reality? What about time? Is it an object or some phenomena? Can we go backward or jump into some point in Future?

I'm very confused? I am waiting for some good discussion on this matter in this forum?

A lot of those questions have no proven answer.

Is the universe infinite? Nobody knows really, but since it is expanding, there is a limit to the portion of it that we can possibly observe or interact with, so the only portion of the universe that matters to us in any way is finite.
Beyond the border of that (though we'll never be able to observe it) presumably is more universe, just like the part that we're familiar with. That part, though, is receding away at faster than the speed of light, so there is no way we can observe or interact with it.

How it all started? Well, there is one popular theory called 'big bang'... though that doesn't fully explain why the big bang happened in the first place.
My personal theory is, you could keep recursively asking the same question over and over: "what came before that?" ... Eventually the only permanent answer could be "It has always been that way".

Is it all an illusion? It might be. That's another untestable/unprovable question. The results of any test you perform on the subject could be just as illusory as the rest of the world. "I think, therefore I am" gives you a starting point - it at least lets you know that your mind is real. (Real in the sense that it exists and works as a mind. It may not be the same as you think it is though.)

Is time an object or a phenomena?
No.
It is a dimension.
The four dimensions we experience on a day-to-day basis are the three spatial (up/down, left/right, forward/back) and one temporal (time).
We seem to move through the spatial dimension at will (subject to laws of physics), but move through the time dimension (apparently) at a constant rate, in only one direction.
There may be exceptions to this... but those are mainly speculation.
It may theoretically be possible to travel in the time dimension in different directions or at different rates. It may also be possible to use an extra dimension to go 'around' it. (The same way you could use a third spatial dimension to go around a 2D obstacle.)
--That, of course, requires the existence of that extra dimension, and requires us to figure out a way to travel through it.
Peterssidan
ocalhoun wrote:
That part, though, is receding away at faster than the speed of light,

I thought nothing could travel faster than light. Am I missing something? (Ignoring the recent CERN findings)
Bikerman
Yes and no.
Nothing can travel through spacetime faster than light.
The expansion of the universe, however, is an expansion of spacetime itself. Therefore objects in spacetime can apparently 'move apart' faster than c. You can imagine it as the space between the two objects stretching - so although the objects don't actually move, they appear to be flying away from each other.
If you want an analogy....
Take a long elastic band. Thread beads onto it and arrange them at intervals of 1cm.

.....B1.....B2.....B3.....B4.....B5.....B6.....

Now stretch the band.

The beads 'move apart'. The speed at which they move apart depends on the distance. B3 recedes from B1 at twice the rate that B2 recedes from B1.

Does that make sense?
Peterssidan
That reminds me of an exercise we had in a physics course. It was two rockets that travelled away from the earth in opposite directions with a speed of 0.6C. The task was to calculate at what speed the two rockets moved away from each other. I don't remember the exact answer but I'm sure it was lower than C.
Bikerman
Yes, it is slower.
The formula is simple:
w=(u+v)/(1+uv/c^2)
where w is the velocity observed at either point, v and u are the velocities of the 2 viewpoints and c is speed of light.

So we get w = 1.2/1+0.36 = 0.88c
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