Food for thought..

Discussion of theories involving time as a dimension, time travel, relativity, branes, and so on, usually applying to the "real" universe which we live in.

Food for thought..

Postby knigitz » Fri Jun 09, 2006 11:32 pm

It's been a while since I posted anything on these boards, just thought I'd give it another go.

Point 1 (Expansion)
All mass and energy potentially was contained in one singularity, and then exploded to create the universe. "Big Bang!"
- Did this singularity contain infinite mass and energy?
- Did this singularity explode mass and energy into the universe, or did it leak mass and energy into the universe?
- If this singularity contained infinite mass and energy what is to stop it from expanding infinitely? What are the conditions for the universe collapsing?
- If this singularity contained limited mass and energy what is left to cause a collapse? In neither this point or the last could the mass and energy dissipation negate space at that singularity to create a fissure to collapse the universe back onto.

Point 3 (Time Travel/FTL Travel)
- What makes light speed the ultimatum for travel speed? Light is made up of photons which have no mass, but have energy and momentum. Since light is massless, anything with mass cannot travel FTL, according to the E = mc^2 conversions. But, what if enough energy was outputted against a mass to allow for that barrier to be broken?

What if we had two machines. The machine in the front would be connected to the one behind, and it's engine being strong enough to push both the machines at max speed (without breaking the barrier), then the back machine releases from the front. Where would that extra energy go, if not into speed?

(I'll be back later to write more)
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Re: Food for thought..

Postby Nick » Fri Jun 09, 2006 11:42 pm

knigitz wrote:- Did this singularity contain infinite mass and energy?
- Did this singularity explode mass and energy into the universe, or did it leak mass and energy into the universe?

Theoretically, singularity's have infintessimal size and an infinite mass and energy. Since infinity is impossible, I would assume that the singularity that created the universe is as close to infinity as possible, but not actually reaching it.

- If this singularity contained infinite mass and energy what is to stop it from expanding infinitely? What are the conditions for the universe collapsing?

I have the same question! :o

- If this singularity contained limited mass and energy what is left to cause a collapse? In neither this point or the last could the mass and energy dissipation negate space at that singularity to create a fissure to collapse the universe back onto.
- What makes light speed the ultimatum for travel speed? Light is made up of photons which have no mass, but have energy and momentum. Since light is massless, anything with mass cannot travel FTL, according to the E = mc^2 conversions. But, what if enough energy was outputted against a mass to allow for that barrier to be broken?

What if we had two machines. The machine in the front would be connected to the one behind, and it's engine being strong enough to push both the machines at max speed (without breaking the barrier), then the back machine releases from the front. Where would that extra energy go, if not into speed?


The only way for that to work is if the following condition must be met (assumming the speed of light is an easy 100 mph.):

- The machines would need to be moving at 99.99999...(infinitly repeating) miles per hour. In other words, the machines must be as close to the speed of light as possible before they can break the barrier.

In order for this to be true, the sum of the mass of the machines would need to be infintessimal to reach that kind of a speed. Therefore, it wouldn't work.
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Re: Food for thought..

Postby knigitz » Sat Jun 10, 2006 12:20 am

irockyou wrote:The only way for that to work is if the following condition must be met (assumming the speed of light is an easy 100 mph.):

- The machines would need to be moving at 99.99999...(infinitly repeating) miles per hour. In other words, the machines must be as close to the speed of light as possible before they can break the barrier.

In order for this to be true, the sum of the mass of the machines would need to be infintessimal to reach that kind of a speed. Therefore, it wouldn't work.


That really doesn't answer my question. I guess a better way to explain it is this:

The speed of light = 299,792,458 m/s
The mass of light = 0

But what sends light out into all corners of the universe? How much energy is required to make 0 mass photons travel at 299,792,458 m/s?

It's certainly not unlimited energy, because then the speed would also have to be unlimited since light is 0 mass, and you need to maintain conversion. Right?

Why can't anything with mass travel beyond that speed?

Edit: And please don't use repeating numbers. They hurt my head.
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Postby Nick » Sat Jun 10, 2006 2:01 am

How are you so sure that light is actually in all four courners of the universe (assuming there are four corners)? Have you actually been there? Light might not have reached the entire universe... it doesn't move infinitly fast.

Nothing can move faster than light because of Einstein's Theory of Relativity. According to him, the speed and direction of an object is relative to your frame of reference. For example, a kid throws a ball to a friend. To both friends, the ball is moving in opposite directions. However, to both of them the ball is moving at the same speed (say, 5 miles an hour). However, to an alien outside of earth, the speed to him is the speed of the earth + 5 miles an hour (assuming the kid threw the ball in the direction of the earth's rotation).

In Einstein's theory, the only physical "thing" that is the same speed for ALL frames of reference, no matter what, is light. That is why nothing can move faster than light... because everything is relative accept for light.
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Re: Food for thought..

Postby jinydu » Sat Jun 10, 2006 2:21 am

knigitz wrote:How much energy is required to make 0 mass photons travel at 299,792,458 m/s?


Perhaps it would he helpful to think of light as an electromagnetic wave. The energy density of an electromagnetic field at a point is given by:

1/2 E^2 epsilon_0 + 1/2 B^2 / mu_0

The total electromagnetic energy present in a system can be obtained by integrating the above expression over all space.

knigitz wrote:Why can't anything with mass travel beyond that speed?


This question has already been answered many, many times in lots of other threads. The short answer is that the energy needed to accelerate a massive object to the speed of light is infinite.

irockyou wrote:According to him, the speed and direction of an object is relative to your frame of reference.


Actually, Einstein was not the first to come up with that idea. In fact, although Newton personally believed in the existence of a universal frame of reference, his theory is fully consistent with the notion that velocity is relative to one's frame of reference. Have you heard of Galilean transformations?

irockyou wrote:In Einstein's theory, the only physical "thing" that is the same speed for ALL frames of reference, no matter what, is light.


No. There are other frame-invariant quantities as well. They include:

Spacetime distance: (ct)^2 - x^2 - y^2 - z^2
Rest mass: m
Proper length: L_0
Proper time: sqrt(Spacetime distance)

In general, the inner product of any 4-vector with itself yields a frame-invariant quantity.
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Postby moonlord » Sat Jun 10, 2006 11:11 am

knigitz wrote:- Did this singularity contain infinite mass and energy?
- Did this singularity explode mass and energy into the universe, or did it leak mass and energy into the universe?
- If this singularity contained infinite mass and energy what is to stop it from expanding infinitely? What are the conditions for the universe collapsing?
- If this singularity contained limited mass and energy what is left to cause a collapse? In neither this point or the last could the mass and energy dissipation negate space at that singularity to create a fissure to collapse the universe back onto.


The singularity contained finite mass/energy, that is the mass/energy of the whole universe nowadays. However, its volume was zero, so the density was infinite. We believe that, for some reason, it exploded. Now about the collapsing: if the universe will collapse depends on several factors. The main idea is, if the gravity between galaxies eventually stops them from expanding, they will collapse. I believe is it not yet sure what happens when all mass/energy goes in a space that small, or if it will eventually collapse to a point.

About the two machine problem: according to Relativity, speeds don't just sum. This means that if you run at 99% the speed of light and launch a missile that normally goes at 99% the speed of light relative to the spacecraft, the missile will not go at 198%*c. It is closer to the speed of light than 99%, but does not reach it.

irockyou wrote:- The machines would need to be moving at 99.99999...(infinitly repeating)


There are several proofs that 0.~9=1. I will post some if you'd like :). So 99.9999... (infinitely repeating) = 100, the speed of light you assumed. Therefore, the hypothesis is false.

jinydu wrote:There are other frame-invariant quantities as well. They include:

Spacetime distance: (ct)^2 - x^2 - y^2 - z^2


Don't massive (with mass) objects cause the spacetime to curve into itself, in such a manner that the formula doesn't hold anymore?

EDIT: Oh, you said, "frame-invariant". It's clear now...
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"Not only does God play dice, but... he sometimes throws them where we cannot see them." -- Stephen Hawking, late 1900's.
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Postby PWrong » Sat Jun 10, 2006 11:29 am

- Did this singularity contain infinite mass and energy?

No. By conservation of energy, we know that the singularity had the same energy as the total universe has today. The energy was contained in a point of zero size, so the density and temperature was infinite.

EDIT: Just realised Moonlord already said this

- Did this singularity explode mass and energy into the universe, or did it leak mass and energy into the universe?

It exploded, inflating spacetime with it.

How are you so sure that light is actually in all four courners of the universe (assuming there are four corners)?

The universe is isotropic and homogeneous, which means it's pretty much the same everywhere. If there's light here, there must be light everywhere else (or at least everywhere where there is space).

About the two machine problem: according to Relativity, speeds don't just sum. This means that if you run at 99% the speed of light and launch a missile that normally goes at 99% the speed of light relative to the spacecraft, the missile will not go at 198%*c. It is closer to the speed of light than 99%, but does not reach it.


It's exactly equal to:
(0.99 + 0.99) / (1+ 0.99*0.99) = 0.999949
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Postby papernuke » Fri Sep 08, 2006 10:57 pm

This is food for thought? What does whatever you said have to do with food?
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