How fast can we go?

[aichip]

To elaborate a bit, if we consider the vacuum to be the "grid lines" that reality is laid upon, stretching out the grid lines does not make the matter within the universe actually move. It is essentially standing still as space expands around it, and the effect is that everything appears to be moving away from it.

Even today, we known that the universe is expanding, and we can see that more distant objects appear to be receding from us even faster than nearby ones. What is really happening is that the objects are standing still (more or less) but space itself is stretching out. This is the same situation as the rubber sheet printed with grid lines.

So since there is no net velocity change for any of the matter within an expanding universe, there is absolutely no acceleration force felt, and there is no relativistic mass problem. From the standpoint of each and every atom within such a universe, it is still moving or not, and it feels no net force in any case.

Can the light of a galaxy vanish under such circumstances? Sure. Expanding space leaves some signatures, and one is red shift. There are something like five different kinds of red shift observable, and spacetime expansion is only one of the causes. But if you were in a region of space that was expanding faster than light, you would see the universe go black around you as the objects all around appeared to recede at the speed of light.

Let's take a test case. You and a friend are shining laser pointers at each other, and then the space you are in expands at ten times the speed of light for one minute. What do you see?

First, as the space begins to expand, the color of his laser pointer drops rapidly down through the infrared to blackness- possibly down to microwave frequencies just as we see in the sky today.

Then, over the course of the next ten minutes, you would see only that faint very red-shifted energy- photons that were emitted into the stretching space, but retained their energy, would eventually show up as extremely faint laser light. Those photons that were "on the way" once the expansion stopped would still appear as the proper color, but spaced far out in time- 1/10 the intensity you would expect.

Then, after ten minutes, you would see your friend's laser pointer as it should be, but removed 180,000,000 kilometers.

Now, why would the photons still be the proper color, unlike te red shifted light we see from distant galaxies? Because those galaxies are still receding from us, and that is what red shifts their light. But in this case, the only red shifted photons are those emitted while the expansion starts. Once the expansion stops, they are still just photons on the way, and there is no recessional velocity.

Some physicists think that if we could make space expand or contract (perhaps with gravitational waves) we might convert this effect into a useful faster than light travel system. Imagine making space contract, stepping across the shortened gap, and then allowing it to expand once more- you could get somewhere pretty rapidly then. Of course, it might not be possible; only time will tell.

[Astrojan]

...as the space begins to expand...

Did you tell me what you call SPACE ??? (which can be expand.. )

[aichip]

Space is the geometry upon which a universe is built. It is flexible and has properties, and is often called the vacuum. But just because you have "nothing" there, it does not mean that the vacuum is featureless.

Consider a pair of empty boxes. Both are chilled to absolute zero, both have a hard vacuum inside, and both are identical in every way possible. The only difference between the two is that one is on the surface of the Earth and the other is in orbit about as far out from the Sun as Neptune.

Now, without any instrumentation, can we detect a difference in the space inside the two boxes? Yes, easily. Drop a small mass inside each box. In one, it will float freely and nothing else will be obvious. In the other, the mass will accelerate and strike the bottom of the box. Why?

Because in one box, the vacuum is curved four dimensionally, and that yields what we call "gravitation". In the other, the space is nearly flat, and so it appears to be in a state of free fall. The actual vacuum inside the two boxes is different in a subtle but pervasive way.

In a similar manner, all the forces alter the vacuum locally in a geometric manner, and in some cases the process produces effects we can detect easily. Electrical charge is the result of the vacuum being modified in such a way that it produces a field of virtual photons- the carriers of the electromagnetic force. Mass curves space as well, but in a different manner. Each force is associated with a type of curvature or distortion of the vacuum (often referred to as the metric by physicists) and there is also a corresponding particle (or particles) that is tied to that curvature.

So while we cannot touch the vacuum or weigh it, it does indeed have specific properties that can be measured, and it is actually something, and not "nothing". It is easiest for some to visualize it as a flexible rubbery sheet, dimpled by mass and forces.

[orin stepanek]

Aichip: Do you really believe that space can expand between galaxies and separate them without the galaxies moving? Wouldn't it seem that the galaxies would seem to be moving as the gap widened between them? While I don't disregard this completely I have trouble accepting it. None of this has actually been proven, has it?
Maybe Bob Lazar has the secret to space travel after all.
Orin

[Wadsworth]

Airchip:

Because the centerpoint of the Big Bang is not "inside" this universe, in the same way that the center of a balloon is not on the skin of the balloon. The centerpoint of the universe is "inward" in a fourth linear dimension, called "time". We cannot see it because we cannot stick our heads out of the universe in that direction.

This is sort of like trying to look back at the old neighborhood you grew up in and that was then demolished to make way for high-rises. No matter where you put your eyes, you cannot see it because it is not in this universe any more.

This helps me with an attempted question I made in another post. Why could we not see it? Our old neighborhood is not in this universe anymore, but the light is. If we could "stick our heads" into the light that was reflected off of our old neighborhood, before it was demolished, then we could in fact see it. Correct? (This would require faster than light travel)
Which brings me to my question. Can the universe be a certain age (13 billion years old) and we be able to see distant light that has a similar age?
That is, if we look through a dark spot in the sky and claim to see our old neighborhood (13 billion years old) we must be traveling within the light that came from the source (old neighborhood or big bang) in order to see it AND be the same age as it is.

ALL of space expanded outward from the point of the Big Bang, in a manner similar to a balloon expanding from one central point. No amount of walking about on the surface of the balloon (present time) can take you to the center of the balloon (past time). This is like trying to find the edge of a planet by walking on its surface. There isn't one and you can't.

Right, one couldn't go to the center of the balloon, but the light from what used to be the edge of the balloon but is now the center, is still traveling outward either ahead of us, with us, or behind us.

[aichip]

Orin Stepanik wrote:

Aichip: Do you really believe that space can expand between galaxies and separate them without the galaxies moving?

No, if space continues to expand, then the galaxies will appear to be moving apart because the distances between them are increasing.

Wouldn't it seem that the galaxies would seem to be moving as the gap widened between them?

Indeed, that is exactly what we are seeing now. Perhaps my explanation above was not quite clear.

None of this has actually been proven, has it?

Well, space does seem to be expanding, or at least the red shifts from distant galaxies tell us that. As for proof, I guess it depends on whether you believe what the data tells you. I can't see myself going a few billion light years to check things out, at least not this weekend... I have things to do.

For Wadsworth:

This helps me with an attempted question I made in another post. Why could we not see it? Our old neighborhood is not in this universe anymore, but the light is. If we could "stick our heads" into the light that was reflected off of our old neighborhood, before it was demolished, then we could in fact see it. Correct? (This would require faster than light travel)

This is correct. The light is expanding outward forever (or at least until the end of the universe, whichever come first). If we could outrace the light waves, yes, we could in theory see the past. But other effects would also be obvious, like running into the past itself, and not just the light waves. Or it seem that this is a possible outcome.

Which brings me to my question. Can the universe be a certain age (13 billion years old) and we be able to see distant light that has a similar age?

Well, yes, maybe. It depends on one crucial factor- the time that the universe became transparent. You see, when the matter was extremely dense and hot, the light could not escape easily, and so the universe would be opaque. Only when it had expanded and cooled sufficiently would the light and energy become thin enough to allow light to travel through space unimpeded.

So if we have a powerful enough telescope, we might in theory see the "opaque boundary" of the early universe, and some think that we might already be capable of this. I think I read somewhere that this would have been about 300,000 years after the Big Bang.

Right, one couldn't go to the center of the balloon, but the light from what used to be the edge of the balloon but is now the center, is still traveling outward either ahead of us, with us, or behind us.

And this is a distinct possibility. Suppose that the universe is just 13.7 billion light years in radius- then we cannot see past that point ever, if the theory is correct. There will be an opaque limit to the distance we could see, due to the brilliance of the earliest universe.

But what if the universe is smaller than 13.7 billion light years? This seems unlikely, because the inflationary period already made it larger by orders of magnitude than simple expansion below the speed of light would have. And, since the light has been "on the way" ever since, the universe would have to be larger by any type of reason that I can come up with. However, in the unlikely event that the universe is somehow smaller than that, then we would probably see space "wrapped around" on itself, and possibly spot our own galaxy on the distant edge of our vision, although it would be pretty young.

This idea has been seriously considered- that space might be smaller in one or more directions than the age of the universe. The answer lies in the geometry of spacetime, something that is being researched now.

Finally, what if the universe is much larger than 13.7 billion light years? It could be, and as a result there would be parts of our universe that we could never see them. It would be physically impossible for light from those areas to ever reach us because we are receding from them essentially at the speed of light, due to expansion. So the universe could actually be 70 or 100 or 1,000 billion light years across, and over that sort of scale, there might even be variations in some of the basic physical laws. There would be no way to know or to feel those effects, because we are effectively isolated eternally from them.

In that case, we would still run into the opaque boundary from the early universe, and we could not tell what might lie on the other side of that implacable wall.

[orin stepanek]

Aichip!! Thank you for letting me pick your brain. I really appreciate the time you took to answer my questions. I believe I have a tiny bit better understanding of the universe than I did. There is something in the heavens that seems to draw man toward it. I hope man learns to live in harmony so that we can, one day; explore the wonders of the universe by being able to walk among the stars. 8)
Orin
P.S. Do you believe that faster than light travel may be probable?

[Astrojan]

Space is the geometry...

Yes, it is. Space is only a geometry which isnt equal with vacuum.
Like a line is a geometry, and a plane a geometry also. Nobody will suppose a line will expand anyhow, because it is endless, so a line cannot be expand. Or a plane will not be expanded because it is infinite by definition in two dimension.

Consequently the space also infinite and cannot be expand.

[aichip]

Astrojan wrote:

Space is only a geometry which isnt equal with vacuum.
Like a line is a geometry, and a plane a geometry also. Nobody will suppose a line will expand anyhow, because it is endless, so a line cannot be expand. Or a plane will not be expanded because it is infinite by definition in two dimension.

Consequently the space also infinite and cannot be expand.

The problem is simple- you are equating Platonic geometric ideals (which are purely mental models) with actual spacetime. The two are not the same.

The vacuum is not the whole story- it is just our perception of spacetime. The true story is more complex, like the wave/particle duality. Our senses do not report everything, that is why we make telescopes and microscopes and other instruments of technology.

Consider the two boxes example that I related. If you do not invoke spacetime curvature (which is considered proven and is an essential part of relativity) then you have a very tough time explaining the difference between the space in the two boxes. But note that the curvature of spacetime also explains very easily the present debate about "speed of gravity".

Think about this. Gravitation as a force is said to be carried by the graviton particle. Since nobody has yet actually detected the graviton, due to its extremely low energy, then it is still a theoretical concept. but in keeping with the other fundamental forces, it makes an excellent symmetry.

But we can also view charge and gravitation as a curvature of spacetime, and we know that curved spacetime easily explains the difference in the flow of time (a measured and proven phenomenon) in clocks moving at different speeds and at different altitudes. But to resolve the problems of "speed of propagation" for gravity, we only need to realize that the spacetime itself is already curved where a mass is passing near another mass- and therefore, we do not need to wait for gravitons to reach out and interact with an object.

With this one simple concept, we now see that gravitation is not "something that has to get there first" but is actually a curved part of space and any object entering that zone is therefore already interacting with an extension of the object.

This is a simple case of us assuming that an object ends where our eyes say it does. It does not. Its mass field (and gravitational effects) extend everywhere. The same is true for a magnet- and this is a case where we can actually feel the rubbery repulsion of two like poles, even though our eyes cannot see that the vacuum itself is polarized by the magnetic field.

This too is another clue to the nature of the vacuum. It is a something, not a nothing, and it can be polarized so that the influence of some objects can be felt far from those objects.

So the vacuum is not the abolute geometry of Plato, it is another thing. It is flexible and can stretch, it can be polarized, it can be affected by objects tht exist within it.

[aichip]

Sorry, I did not mean to forget about you Orin.

I do think that faster than light travel may be possible. It just might be that what we end up doing is not actually travelling through space but some other thing. Some theorize about the use of wormholes (which are geometric things) or the use of bubbles that detach from spacetime and reattach elsewhere.

Some scientists feel that negative energy could be used to create a zone where faster than light travel is possible. There are other schemes involving theoretical entities call tachyons that are supposed to travel faster than light.

Understand that this is all speculative or theoretical, and no real results of this is yet seen. But when we think about the enormous travel times associated with traveling through the universe, faster than light travel is a very appealing concept. Wishful thinking so far, but we can hope.

[toejam]

Australia changed to metric back in the 70's.

Why is USA so backward?.

I have asked myself that same question many times over the last 6 years or so.

Face it, you subconciously regret your treasonous behaviour towards good king George III
So you keep on with the old Imperial measures. The question is why did you screw up so badly with the liquid measures? Getting short-changed on every pint, quart & gallon. Was that some Limey trick? Or was it a form of taxation?.

[harry]

Hello

Your right,,,,,,,smile.

But! metric is so easy to use and funtional. All sciences use it. Only non-scientific people use miles and gallons.

So world ,,,,,,,,,,,,,,all that do not have metric system must change,,,,,,,by order of the APOD

[orin stepanek]

Hi Harry! Even back a few years [50] when I was still in high school; The talk was that the metric system was easier to understand the miles and feet and quarts and cups etc. But it never happened. I guess habit is hard to change.
Orin

[Dr. Skeptic]

NASA's Climate Orbiter was lost in 1999 do to the Colorado navigation team using M/H instead of K/H. Does that mean Lockheed-Martin-Colorado hires non-scientific employees?

[orin stepanek]

http://www.jpl.nasa.gov/releases/99/mcoloss1.html
Dr. Skeptic: you'd expect these things wouldn't happen; but when two systems are in use than it should be made known which system should be used. Human error causes much havoc at times.
Orin

[Dr. Skeptic]

I was referring to blanket statement:

But! metric is so easy to use and funtional. All sciences use it. Only non-scientific people use miles and gallons.

[harry]

Hello Dr Skeptic

We can have humor here.

You said

NASA's Climate Orbiter was lost in 1999 do to the Colorado navigation team using M/H instead of K/H. Does that mean Lockheed-Martin-Colorado hires non-scientific employees?

They probably do, to cut down on costs. Cheaper to use non-scientific employees.

Qev I did not know that you were younger than me.

[Qev]

Qev I did not know that you were younger than me.

How'd I end up in this thread?

[harry]

Hello Qev

The dog leading the dog.

Thats how I ended up here.


What topic are we on? I'm confused.

Oh! Yes

Space is a word cannot expand or contract.

If the galaxies are expanding can someone tell me which one.

Our local galaxies is not
Out local cluster of clusters of galaxy is not
Our super clusters are not.

[orin stepanek]

Just how old are you Harry? I agree just how can something infinite expand?
Orin

[Dr. Skeptic]

The galaxies are not expanding, it is the space/time between them.

How do explain away the "Hubble Constant"?

Ignoring it is not an option.

[Qev]

Just how old are you Harry? I agree just how can something infinite expand?
Orin

Say I have an infinitely-long line of marbles, all touching end-to-end. I push a new marble between two of them. The infinitely-long line of marbles just got one marble longer. It expanded.

It's a rough analogy, as it'd be hard to push an infinitely-long line of marbles. That's why it's called an analogy.

[harry]

Hello Qev

Well I was selling newspapers when Kennedy was shot. I was around when Elvis started.

I think I came after the monkeys.

[Dr. Skeptic]

Say I have an infinitely-long line of marbles, all touching end-to-end. I push a new marble between two of them. The infinitely-long line of marbles just got one marble longer. It expanded.

The analogy misses completely and in fact reinforces my point. Your knowledge of the universe has not developed enough to create a viable concept/model to create a viable analogy.

Today's lesson:

As stated earlier, ∞ is a concept only - it does not exist anywhere in the universe.


The BB did not create everything from nothing. The BB created the beginning of space/time, maybe more, maybe not. To borrow from the M-theory, imagine the pre-BB universe contained only seven dimensions, an event occurred causing the creation of the additional four dimension we know as our universe. The tools of our four dimension do not readily interact with the other seven making it near impossible to quantify or qualify what ever resides within. Because everything in the four dimensional universe is finite by mathematical definition, this model allows the removal of ∞ or 1/∞.

Space, time, or matter cannot be = ∞ or all mathematical representations of the four dimensional universe are null and void.

[harry]

Hello Dr Skeptic

I think you whatch too many fantasy movies to come up with these multi dimensions.

As for any person on this earth to have enough info on the universe to resolve the actual model is very little chance.

We know and see into dep field maybe 13.5 billion years. This is only a sand grain on beach being infinetly long.

We could assume that what happens in a visible universe repeats over and over.

But if we use fantasy land ideas than the bunny rabbit will walk in.