Advanced technology

Great Debates
21

jb_farley - it’s still a perpetual motion system though. From it we can extrapolate the possiblity of a smaller system that works on the same principle. (prehaps somthing similar to a blackhole)

Exactly. The very same principle that suposedly caused a bigbang in the first place, right? PPM.

Though I won’t argue the point anymore. I think Matt has done a far better job explain myself than I ever could =]

**Matt **-
I’m curious as to your postion on the artical that I posted above concerning the speed of light exceding its own limit. I’m not saying that it means “we” can go faster than light, but it does seem rather interesting that light can go faster than what we have generaly considered c to be.

22

ted, no, you are missing the point. the universe is definitely not a perpetual motion device. i think the fact that a breathing universe will last forever and cycle perpetually is what’s throwing you off. that doesn’t make it a perpetual motion machine.

i understand that i didn’t explain it clearly enough last time. there is a crucial difference between matter moving and space moving. space can move and carry the matter with it, but that’s not ‘motion’. it not an anally semantic definition.

it takes energy for me to swim across the english channel. but i can lay there and not expend any energy, and be carried away into the atlantic. the former is like the ‘motion’ in ‘perpetual motion machine’. the latter is not.

23

Myrr21

That’s why it’s impossible. If your PMM doesn’t leak energy, then there’s nothing impossible about it.

No, I don’t see. The second law of thermodynamics does not say that perfect efficiency is impossible. And let’s just pretend that there is such a law. Why would it preclude the existence of a PMM?

24

Ted wrote:

I can’t see the article you’ve linked to (I don’t subscribe to the NY Times Online), but if you’re talking about certain recent experiments I think you’re talking about, some clarification is in order:

Yes, given the right propagation medium, some scientists were able to shine light through it in such a way that it “moved” at 300 times the speed of light. This is actually not a new phenomenon. It has been observed and predicted to happen at a few (much less than 300) times the speed of light in the tenuous, electrically charged Van Allen belts as well.

BUT,

The thing in this light that’s propagating faster-than-light is the phase velocity of the photons. The group velocity is always c or slower. And it is the group velocity, not the phase velocity, that carries the energy and information.

It’s like this. Imagine a spinning barber pole hurtling lengthwise through space. If it’s spinning in the right direction, the stripes on the barber pole will appear to travel forward, faster than the barber pole itself. But these stripes will not actually reach you until the barber pole itself reaches you. Similarly, although the phase velocity of a bunch of photons can exceed c, the photons themselves won’t travel any faster than c.

It’s not like you could use this effect for FTL travel, or even FTL communications. It’s only use might be to increase the data-transfer rate of communications at a given frequency.

25

Ted:

You seem convinced that there is enough matter density in the universe to bring it all back together in the Big Crunch. But it seems that the Big Crunch will never happen…at least it seems so now.

And anyway, even if we had a Big Crunch, that does not imply that the universe will undergo another Big Bang, or that the new baby universe after the second Big Bang will have the same amount of energy/mass as our universe.

The trouble with invoking the Big Bang as proof that physical laws aren’t absolute is that past a certain point the Big Bang/Big Crunch are scientifically unknowable. There’s no way we can know anything about what existed previous to the Big Bang, since all matter/energy was compressed into a single point, obliterating any structure.

And saying that we got energy for free in the big bang doesn’t help you if you want to constuct a perpetual motion machine here and now on earth.

Here’s a common-sense refutation of perpetual motion. Suppose some one came to you with a perpetual water machine. Nothing goes in, but water comes out. He could point to all kinds of valves and pipes and pulleys and chambers that “multiply” the water, but unless there is a source of water from outside the machine you’ll never get more water from the machine than you put in. There’s no need for you to examine every pipe to know that he’s not multiplying water. Yes, it’s possible to make a machine that extracts water from the atmosphere or the ground, but it is not creating water out of nothing. Well, as you know, modern theory holds that matter and energy are the same thing. If it is impossible to create water from nothing, it is just as impossible to create energy from nothing.

And don’t say “The Big Bang”. What evidence do you have that the Big Bang created energy from nothing? It is accurate to say that we don’t know–and almost certainly cannot know where the energy for the Big Bang came from, but we don’t know that it came from nothing.

26

tracer - http://www.spie.org/web/oer/july/jul00/lightlimit.html
Try this one it’s the same artical as in the NYT. And thanks for the info, allthough I must admit I really don’t follow it that well. =] I’ll look back on it later and see if I can figure it out. heh.
Lemur866 - All this was allready pointed out.
Besides, I’m not even convinced that there “was” a big bang. The only point I was trying to make was that it is possible to have a PPM with the given laws of our universe. (Even more possible than it is to break the speed of light if I understand tracer properly)

And I’m not talking about a PPM that creates energy from nothing, I’m talking about a PPM that perfectly recycles engery. See Matt’s reply. He say’s it better than I.

27

Ted, I know you are not a physics expert. neither am i. may i ask you discuss what type of perpetual motion machine you are thinking of? or do you rather not have any specific ideas, just the knowledge that all theories are just that, theories, and an exception unthought of by you or me or anyone else may come along in the future?

jb

28

** jb_farley ** - Specficly? As far as the universe example is concerned I’m thinking of the second type (check matt’s listings) a machine which uses the same energy over and over again.
If it’s true that the big bang was caused because of a crictical mass, then I would say just create the same thing only on a smaller principle. (if such a thing could be done)
I do admit however, that I don’t understand what you mean when you say that it is space moving, not matter with the big bang. So prehaps I am wrong.

This is how I would see it though… You an infinitely large vaccume, which I would call space. Somewhere with in that space you have this large amount of mass. The mass explodes and expands in all directions. Evenutaly the mass Cools down and spreads out. Gravity however eventualy pulls everything back togehter to recate that large amount of mass again. The process repeats.

The only thing I could think of when you say it is space moving and not mass is that the universe is limited to this expanding mass, and there is no empty space around it as I had assumed. Is this how things are? If so, I acced your point that it is not a PMM, but otherwise I honestly don’t follow. (If it is true, could you point me to some links that better explain the situation to me? Like I said, I’m rusty on my Physics)

As far as somthing we could make though? I would say it is close to impossible to build a PMM of the second sort then. At least so long as we hold with probablities… There’s still a possiblity of it happening though. And I’m talking about under the given laws of the universe as we know them, not by some chance we were mistaken about them.

I say this because the second law of theremo dynamics states, “Energy spontaneously tends to flow only from being concentrated in one place to becoming diffused and spread out.”
It’s only when we apply probablity to this that entropy becomes a reality. … so in theory, given an infinite number of potentail PMMs in an infinite amount of time, one of them will be a true PMM. (at least of the second order)

29

I am a happy owner of Faster than light, a great book which covers lots of ways to break the speed of light. It includes moving the spot of a laser pointer across the wall, the intersection point of a pair of scissor blades, rip tides, green sunglasses (that’s a neat one!), radio wave propagation through ionised gases, quantum entanglement and a few more.

A central principle is that relativity forbids the transmission of information faster than light. Moving spots of light or intersection points on scissors can’t be used to transmit information faster than light, so they don’t contravene relativity. (So far, neither can quantum entanglement, but that doesn’t stop some enterprising folks from trying.)

To transmit information with light, you have to be able to change the light in some way, i.e. modulate it. Simply turning it on and off will do.

Normally, if you point a lamp in empty space and turn it on, the light waves emerge at c. You can imagine a “rod” of light propagating through space, its end advancing at light speed. The end of the rod is the “signal”, the part carrying information.

Now, let’s say instead of light we use a radio beam, and the beam enters ionised gas. Something rather weird now happens. The “end” of the “rod” continues to propagate through the gas, but slower than c. This is the group velocity.

The radio waves within the “rod” now travel faster than c but dissapear when they hit the “end” of the “rod”. This is the phase velocity, which exceeds c. It doesn’t violate relativity because you can’t transmit information faster than c with it. No modulations of your radio beam will exceed c, in fact, they’re slower.

Another way to look at it is that the phase velocity is an illusion. You have a radio beam passing through the ionised gas;- the gas ions absorb and re-emit the radio beam in such a way that the interference of all the radiobeams make something appear to go faster than light. But nothing really does, it’s like that intersection of your scissor blades again.

Now to the link Ted provided: - some people think it’s a special case of the situation given above. A subluminal signal crosses a chamber and causes it to kick out a particular shaped pulse from the far side slightly before an identical trigger pulse enters on the near side.

Other people are not so sure. Guess we’re going to have to wait and see.

I really hope it does turn out to be superluminal information transmission, there’s nothing like a shattered paradigm to wake you up in the morning! :slight_smile:

30

Lemur866 said:

"And don’t say “The Big Bang”. What evidence do you have that the Big Bang created energy from nothing? It is accurate to say that we don’t know–and almost certainly cannot know where the energy for the Big Bang came from, but we don’t know that it came from nothing."

Well now I’m going to sulk!

MY perpetual water machine gets its water from the same, “not nothing” source that Big Bang got its energy.

So there.

31

The yahoo link is invalid (not that I trust yahoo anymore than the NY Times).
I don’t know anything about newscientist, but that article isn’t relevant, anyway. A bunch of people talking about how maybe the speed of light might have changed isn’t evidence that light can move faster than c.

32

**matt ** - thanks for the information! Very educactional.

The Ryan - You’re right. I with draw my postion that it has been broken.
At least so far as I could understand matt’s explaination and others’ explaination of what was going on. The experiemnt only sugests that it might be able to get around c. There’s still not nearly enough evidence to say. I guess we’ll just have to wait and see what happens.

33

Special Relativity says that nothing can go faster than light, because if it did you could have “frames of reference” where information travels backwards in time.

That said, when most people think of FTL travel in a science fiction context, what they mean is “I want to visit that solar system five light-years away and return home, in less than ten years”.

Oddly enough, this just might be possible. Special Relativity is so called because it addresses the special case of uniform movement; General Relativity is the broader theory that incorporates acceleration and gravity into the picture. The full mathematics of GR are notoriously difficult, but they seem to imply that two points of space can be connected in a shortcut that would substantially shorten the trip. Einstein himself addressed such a possibility. So provided that fast roundtrip interstellar travel is possible, it wouldn’t matter if you never “technically” went faster than light.