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?
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?
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.
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.
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?
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.
Yes, it is slower.
The formula is simple:
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