Where Does Space End? It Must End Somewhere!

[KholdStunner]

well, heres your answer.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

IT DOES END. and ill prove it ( with the help of a steven hawkings book)

 

if the universe was infinit then there would be a star EVERYWHERE we look, and the night sky would be as bright as the sun. But it isnt, and there arent stars in every direction, so the universe has an end. But i bet nobody will ever see it, learn about it, or come near to discovering its mysteries, or whats on the other side of the end.

[Ophiolite]

This is Olber's Paradox. The expanding Universe (whether Big Bang or Steady State) gets around this problem.

[YT2095]

IT DOES END. and ill prove it ( with the help of a steven hawkings book)

 

at this point, I changed channel...

[Bettina]

This is Olber's Paradox. The expanding Universe (whether Big Bang or Steady State) gets around this problem.

 

Ok....I looked at Olbers Paradox but still dont get it. The night sky looks like it should look to me....dark with stars. Why should it be all lit up.

 

I was on a small boat once on a lake at night. It had a hand held spotlight that I was trying to point out over the water. It didnt reflect off of anything and was as if I had the light off.

 

Using that, the night sky looks normal...Please explain.

 

Bettina

[Sayonara]

The basic idea is that in an infinite universe there should (eventually) be a star in any direction you can conceivably look, and therefore we should see light coming from every direction.

[Vladimir]

When we say the universe is infinite, it doesnt actually mean that at this moment there is an infinite region of space.

Say as early the universe is 15 billion years old, then it is conceivable that light from the centre would reach us (presuming we're on the 'edge') in 15 billion years, however for light to reach us fromt the oposite side would take 30billion years, and since the universe is ever expanding, that light has to travel even further. It is beyond human comprehension or ability to see over the 'edge' of the universe, as if say we achieved the speed of light and travelled for those 30billion years, the universe would have increased ever more, and therefore unreachable.

[5614]

Ok....I looked at Olbers Paradox but still dont get it.

Olbers paradox:

http://en.wikipedia.org/wiki/Olbers'_paradox

(read the "Assumptions" part)

 

Read through that, it's quite self explanatory, if ya still don't get it ask

[Bettina]

Olbers paradox:

http://en.wikipedia.org/wiki/Olbers'_paradox

(read the "Assumptions" part)

 

Read through that' date=' it's quite self explanatory, if ya still don't get it ask [/quote']

 

I read it, and the joining links too. I still don't see where its a paradox. If space is expanding (the space between galaxies I mean) then the light from those distant stars may never reach us. How could they if the "total" expansion is faster than light itself. I don't see that light ever getting to us no matter how much time we wait.

 

Sorry, I need more links I think.

 

Bettina

[J.C.MacSwell]

I read it' date=' and the joining links too. I still don't see where its a paradox[b']. If space is expanding [/b] (the space between galaxies I mean) then the light from those distant stars may never reach us. How could they if the "total" expansion is faster than light itself. I don't see that light ever getting to us no matter how much time we wait.

 

Sorry, I need more links I think.

 

Bettina

 

If you believed that back in Olber's time "they locked you up".

 

Olber was a 19th century German astromomer. The expansion of space was not popularized until the 1920s.

[Bettina]

Then Vladimir is right so where is the paradox?

 

Also, if the universe is a sphere, (I'm still reading flatland and sphereland) wouldn't the curvature of space have something to do with that?

 

Bettina

[Hades]

nothingness can never exist. if the edge was a plausible goal, when it is passed, there can not be nothing. the idea of nothingness is impossible. once nothingness is entered, one becomes nothing. and that matter would have to become elementary particles or energy. and if that was the case, the nothingness would cease to be composed of nothing.

[swansont]

Then Vladimir is right so where is the paradox?

 

Also' date=' if the universe is a sphere, (I'm still reading flatland and sphereland) wouldn't the curvature of space have something to do with that?

 

Bettina[/quote']

 

Like a lot of problems, it's not a real paradox. It only seems like a paradox under a certain set of assumptions. But the presence of the apparent paradox serves to show that at least one of the assumptions is incorrect, like using proof by contradiction.

[boxhead]

Ever since I was a young boy' date=' I have wrestled with trying to understand space. In particular, I have never really understood how space is supposed to never end. I really don't see how that's possible. Everything ends somewhere. Where one thing ends the next begins.

 

Can people please provide thoughts on this?[/quote']

 

it is not necessary that it should :END: somewhere but if it is infinite than we need a proof that it is infinite and that is not possible becoz the way we define infinity. and that is why there are chances that is ends somewhere.....

[Anarchaus]

I thought that if you could travel faster than light, and you hit the barrier between space time, and what ever the hecks out side, you would just magically appear at the exact opposite side of the universe, like a classic 2-D arcade game.

[alt_f13]

I thought green monkeys could shoot out of my arse.

[Bettina]

Like a lot of problems, it's not a real paradox. It only seems like a paradox under a certain set of assumptions. But the presence of the apparent paradox serves to show that at least one of the assumptions is incorrect, like using proof by contradiction.

 

Are there any real paradoxes? I mean real ones?

Awhile ago, one of our teachers told us about the "if you go back in time and kill your father you would not have been born.....so if you were not born, how could you go back and kill your father."

I replied to the teacher that you can do it one time. I could go back in time and kill my father and not have been born. I changed time events, so there is no paradox. Time would continue without me.

 

So, in the universe, are there real paradoxes?

 

Bettina

[ecoli]

Are there any real paradoxes? I mean real ones?

Awhile ago' date=' one of our teachers told us about the "if you go back in time and kill your father you would not have been born.....so if you were not born, how could you go back and kill your father."

I replied to the teacher that you can do it one time. I could go back in time and kill my father and not have been born. I changed time events, so there is no paradox. Time would continue without me.

 

So, in the universe, are there real paradoxes?

 

Bettina[/quote']

 

That is a paradox. Because if you were never born, you couldn't have never traveled back in time to kill your father...so you would be born, and could travel back in time to kill your father...

[Bettina]

That is a paradox. Because if you were never born, you couldn't have never traveled back in time to kill your father...so you would[/u'] be born, and could travel back in time to kill your father...

 

Because the teacher made the asumption that I COULD go back in time to kill my father. NOT if time reversed, and I got younger and younger.

 

I stay the same age I am now. Just like "back to the future". I can go back keeping the same age, kill my father AND my mother and cease to exist thus no paradox.

 

Hmmm...how about this then.......I hire my teacher who is MUCH older than me to go back and do the killing. If you want time to reverse and we go back together then I end up not born, but he being a teenager kills him.

 

I know this is off topic, but I want to know more about paradoxes.

 

Bettina

[ecoli]

Because the teacher made the asumption that I COULD go back in time to kill my father. NOT if time reversed' date=' and I got younger and younger.

 

I stay the same age I am now. Just like "back to the future". I can go back keeping the same age, kill my father AND my mother and cease to exist thus no paradox.[/quote']

 

No...You're missing it. If you're father dies before your born, then you could never be born. If your never born, then you could not travel back in time to kill your father. Thus, your father would not die, and you would be born. If you are born, then you can go back in time and kill your father....etc.

 

There's the paradox. By not allowing yourself to gain a life (killing your father) Then you could have never have been born to travel back in time and kill your father. Thus a situation is created were you could be born.

 

Do you see it now?

[Sayonara]

Except that it can only be a paradox on paper, because if the conditions are right for that paradox to exist in real terms then by definition it can never be initiated.

[Johnny5]

There are no paradoxes in reality. It's the law of non contradiction.

 

Not (X and not X), for any statement X.

 

Whenever you encounter something called a paradox, there's always a way out, it's just difficult to see it.

 

Like take the barber paradox for example.

 

Suppose that there is a barber who shaves all those who don't shave themselves, and only those who don't shave themselves.

 

Who shaves the barber?

 

Let 'shave' be a binary relation on the set of those who can be shaved.

Read X-S-Y as "X shaves Y"

 

Denote the barber, by the letter B.

 

Now, consider the meaning of the statement, "The barber shaves all those who don't shave themselves.

 

That means this. Suppose that you are an individual who doesn't shave themself. Then the barber must shave you.

 

So for any X, if not (X-S-X) then (B-S-X).

 

Now consider the meaning of the statement, "The only people the barber shaves are people who don't shave themselves."

 

Think about what that means.

 

It means that if Y is a person who the barber shaves, then it absolutely must be the case that not (Y-S-Y).

 

In other words:

 

For any Y: If B-S-Y then not (Y-S-Y).

 

So you are told this:

 

There is at least one B, such that:

 

For any X, if not (X-S-X) then (B-S-X) AND For any X: If B-S-X then not (X-S-X).

 

Using first order logic, you can simplify the previous expression to the following one, which is logically equivalent (meaning the two expressions denote statements which have the same truth value)

 

There is at least one B such that:

For any X: if not (X-S-X) then (B-S-X) AND If B-S-X then not (X-S-X).

 

Now you can simplify this expression a bit further as:

 

There is at least one B such that:

For any X: not (X-S-X) if and only if (B-S-X)

 

Now you can use the existential and universal quantifiers of first order logic, to write the previous expression like this:

 

$ B "X: not (X-S-X) if and only if (B-S-X).

 

Open scope of your first assumption: Suppose that the barber can shave himself.

 

(B-S-B)

 

We were told that for any X the following is true: not (X-S-X) if and only if (B-S-X)

 

So it would be true for the barber.

Therefore, the following should be true:

 

not (B-S-B) if and only if (B-S-B)

 

Your assumption will now lead you to this:

 

(B-S-B) AND not (B-S-B)

 

So it is impossible that the barber can shave himself, and you know this for sure.

 

Now suppose that the barber doesn't shave himself.

 

You were told that the following is true:

for any X the following is true: not (X-S-X) if and only if (B-S-X)

 

So it is true for B, so that the following is true:

 

not (B-S-B) if and only if (B-S-B)

 

Now, using your assumption, you can reach the following statement:

 

 

(B-S-B) AND not (B-S-B)

 

Which cannot possibly be true.

 

So you now know this for sure...

 

Regardless of whether or not the barber shaves himself: The barber does and doesn't shave himself.

 

But you have no assumptions left what do you do now?

 

Actually, there is one remaining assumption, and it is this...

 

 

"There is at least one barber B, such that... "

 

Therefore, there is no such barber, and there is no paradox.

 

Regards

[ecoli]

Except that it can only be a paradox on paper, because if the conditions are right for that paradox to exist in real terms then by definition it can never be initiated.

 

That's the argument against time travel.

[Johnny5]

The simplest way to conclude that time travel is impossible, is to use conservation of mass.

 

If you vanished from now, and jumped to some moment in time far in the future, or far in the past, the total mass of the universe now would change, which is impossible.

 

If you don't like the term 'mass' you can think in terms of conservation of matter at the fundamental level.

 

If you vanished from now, and jumped far into the future, or far into the past, then the total number of indestructible particles now, would vary, which is impossible.

 

 

Regards

 

PS: If the total mass of the universe varied, then the center of mass of the universe would move. It cannot move. Or perhaps I should say... it cannot move in the preferred frame, and if the mass of the universe could change then the center of mass of the universe would move in the preferred frame.

 

If I am not being clear it doesn't really matter, because time travel into the far past or far future leads to a multiplicity of contradictions.

[Sayonara]

If time travel in that fashion is possible, do you not think that perhaps the temporal location of matter is as relevant to conservation as its spatial location?

[Johnny5]

If time travel in that fashion is possible, do you not think that perhaps the temporal location of matter is as relevant to conservation as its spatial location?

Yes.

 

I worked on this problem several months ago, with some others. They were quite knowledgable about GR by the way.