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[DreamThorn]

Since this doesn't belong in the 'Future of the Fortress' thread, I have made a new thread.

The negative mass of antimatter doesn't cause repulsion, because, while the force is negative, the mass is also negative, so the acceleration due to gravity is positive.  But the electromagnetic effect is reversed, which is what creates the semblance of opposite charge.

And, to clarify my other stuff, when I say a physical property is zero, I usually mean infinitesimal.  I think that true zero is not a physical thing.

Also, when I said I was a theoretical physicist, I actually meant to say that I have a degree in physics, do theoretical physics as one of my hobbies, and am studying for bigger degrees in physics.  Because I am looking for a unified theory (which requires new ideas) I tend to get a bit unorthodox.  And since this is a public forum, rather than a scientific journal, I don't proofread my posts, so sometimes there are mistakes or ambiguity.

I recall there being other questions, but I can't recall them.

[zagabar]

Really interesting subject.

A pretty good attempt to a unified theory: http://www.youtube.com/watch?v=MxECb7zcQhQ

I have read the books and they are very good and has many good points. What is best is that if you are open minded, it really makes you think.

[dreiche2]

That's in reply to shadow_slicer:

Why does relative speed have to be symmetrical

That's the way it works, in either classical or modern physics...

The fact is that if you are traveling near the speed of light your seconds become much longer than a stationary observer. Your meters become much longer than a stationary observer's

My seconds become longer (and my meters *shorter*, not longer) only from the observer's point of view. From my own point of view, my seconds stay just the same, but it's the observer's seconds that become slower.

No offence meant (really), but I think you don't quite see the core idea of relativity: All (non-accelerating) frames of references are equivalent. There is no preferred, special one. You seem to assume that there is a truly moving frame of reference, me, and a truly stationary one, the observer. But stationary and moving is always relative. In my own frame of reference, it is always me that is stationary.

There is no absolute speed. If I travel past a planet at 0.9c, the planet travels past me at 0.9c. If there are no other objects around, it seems like I will be stationary. Speed is always relative to something, and thus must be symmetrical because of equivalence.

Because if I travel past something at 0.9c from their point of view, that something will travel past me at 0.9c from my point of view, as well. If it was different, then there would be something special about one of those frames of references, like in your argument, where there's something peculiar happening to only me, because I'm the 'moving one'. But there are no special frames of references, and no 'truly stationary' ones.

Hope that made some sense.

As for antimatter having negative mass, I really don't think that is true, and would like to see some references for that. Plus, as someone pointed out, that would imply negative energy as well...

And finally, about the whole photon discussion: I don't see the point in taking the limit from velocity zero to c to try to derive properties of photons. I doubt it makes sense mathematically, and I don't think it does physically, because photons don't start out slow and then get accelerated to c. Nothing can be accelerated to c. Photons 'start out' at c, and that obviously makes them peculiar, but in particular that means there is something qualitatively different about them compared to particles with rest mass. 

For the record, I have a degree in physics as well, though I'm now working in a different scientific field.

[Flaede]

Since this doesn't belong in the 'Future of the Fortress' thread, I have made a new thread.

I am glad to see this happen. There was a lot of cool stuff being laid out there and it deserved a thread (Even a short thread) of its own. I've found physicists are often interesting folk.

[Shades]

There is no absolute speed. If I travel past a planet at 0.9c, the planet travels past me at 0.9c. If there are no other objects around, it seems like I will be stationary. Speed is always relative to something, and thus must be symmetrical because of equivalence.

What always freaks me out about this whole thing is where you have three points A, B and C, where relative to B points A and C are moving at 0.99c in opposite directions but how A relative to C is still moving away at less than 1c.

I know vaguely the reasoning for it but my brain always goes 'no that is silly' when I try to think about it Not really a question more of a this confuses me statement.

[Il Palazzo]

Hello, this is the internets, everyone can claim to be a particle physicist and proceed to talk nonsense. It's really annoying when somebody drops a bomb like the negative mass and doesn't give any explanation apart from "I've got a degree". No offense to any real physicists, but when posting on a layman's forum, like this one, could the more radical ideas be, not necessary reffered to scientific journals, but simply explained properly. When I say properly, I mean in terms understandable for non-physicists. We could probably assume that everyone interested has got at least a highschool level knowledge of maths and physics.
And don't say it can't be done without involving higher mathematics, there are lots of popular books out there that do it, with a broad range of subjects.

For the record, I'm no physicst myself. I did two years of university-level physics before getting flunked out for not attending, and not to mention, that was a long time ago.

So I'm not going to pretend I know better, but the negative mass of antimatter is just a something I've never heard about.

[DreamThorn]

About the negative mass again, it is merely a different way of looking at antimatter.  It behaves exactly as standard theories of antimatter, but is simpler, and therefore, by Occam's razor, I prefer it.

I cannot remember where I read it.  Probably 'A briefer history of time.', by Stephen Hawking.  It was a possible explanation of virtual particles.  The electron and positron appearing and then annihilating, but with no energy input or output, could be viewed as an electron traveling forward and backward in time along different paths.

And, to one of the other questions:

A photon is an oscillation in the electromagnetic field and must always travel at c, as long as there are no disturbances in the field.  Any disturbance slows the photon down.  Why it is the only boson without rest mass (afaik), is something that I have an idea on, but the math has proven to be too difficult for me, so far.

[Kidiri]

Because Photons are assholes and refuse to obey simple things like 'logic' and thus manage to be both a particle and a wave at the same time, and have no mass but some energy; something which should technically be completely impossible.

Basically, Photons are assholes. But they're just the tip of the Quantum Physics Hates You Heisenbrg.

I just couldn't help myself. Such a pun was doomed to come. I erm... have nothing else to say, actually.
I regret nothing!

[Shades]

Most of the stuff I've read on anti-matter and negative mass matter talking about them as different things and negative mass being theoretical and as far as I am aware the various anti-particles that have been created have positive mass.

But I'm certainly no scientist and don't pretend to understand much of the material I have read, which in itself it not close to being at the cutting edge.

[Sean Mirrsen]

It kinda defies all logic. What makes lightspeed so special that no two objects can ever be travelling at more than 1c relative to each other? I don't care what maths or physics say about it, until there's definite experimental evidence of this, I refuse to believe it's right.

Yes, I understood that an outside observer can see two objects moving apart at more than 1c total. But imagine a construction a light second in length, a target at one end, a laser at another, moving at lightspeed along the laser's aiming vector (it's all hypothetical of course). If an observer attached to the laser activated it, would the observer at the target see it? If it hit, would it be a second later? If yes, then how would they explain that technically, in universe terms, light just travelled faster than light? What would happen if another lightspeed object intersected the beam, say, a mirror? Would the 2c laser instantly revert to 1c upon leaving the construction's reference frame? If so, then where would the energy of this instant deceleration go?

I'm not a physicist, so treat me and my opinions like you will, but I only understand experimental evidence. Theories are alright when they work, but completely unintuitive derivations of theories that can't be experimentally proven shouldn't be treated as.. what's that word? Axiom, I think.

Relativity, both general and special, makes sense in a general way, being internally consistent with itself in most instances, but it completely defies logic in cases such as above, and therefore should really be taken with a barrelful of salt when FTL travel is concerned.

[Shades]

Yes, I understood that an outside observer can see two objects moving apart at more than 1c total. But imagine a construction a light second in length, a target at one end, a laser at another, moving at lightspeed along the laser's aiming vector (it's all hypothetical of course). If an observer attached to the laser activated it, would the observer at the target see it? If it hit, would it be a second later? If yes, then how would they explain that technically, in universe terms, light just travelled faster than light?

The light from the laser only has to travel the speed of light relative to the target, there is no absolute speed. If your driving along a road at 30kph your speed is only 30kph relative to the road, with the earths rotation it's a lot faster, either the Earth's orbit it's at a completely different vector than it looks too

From the point of view of an external observer is where things get confused.

[dreiche2]

Yes, the theory of relativity is unintuitive, but it is both internally consistent and there is loads of evidence for it. Your example, Sean, is no different. If you would sit down and do the maths (which is not trivial, of course), you would see that everything works out. I mean you don't have to believe me, but you shouldn't doubt everything scientists say just because it seems unintuitive to you, either.

But in principle, what you have to do is to start from the constancy of the speed of light in any frame of reference. This is itself paradoxical in classical physics. What you will find though that if you then assume length contraction and time dilation, things work out. Essentially, you start with the constancy of light (and the equivalence of frames of reference) and *derive* all these weird effects from there.

In your example, well the first question: One light second of length in whose frame of reference? Let's say in your own (where you are the guy who is attached to the laser).

So what happens in your own frame of reference? Well, you shoot the laser, it travels the distance to the target and hits it after one second.

What about the frame of reference of an outside observer, relative to whom you travel with almost c in the direction of the laser beam? Well, he would see you with almost c. He then would see a laser beam emerging from you (well technically you can't see the light till it hits you, but bear with me), travelling at c. That means in his frame of reference, the 'tip' of the beam would move away from you, its source, only very slowly. Thus, in classical physics, if you were holding a one light second long target ahead of you, say attached to a stick, it would take much longer than one second to reach the target. So how can this be?

Well, what I just have said is that it should take longer than one second to hit the target. And it does, for the outside observer! And that's time dilation. What takes one second in the moving frame of reference takes longer in the stationary one. The duration laser fires<->target is being hit is one second for you, but from the observer's point of view it would take much longer.

So in your example, time dilation would offer a solution for the apparent paradox that in your frame of reference, the light travels away with c, but seen from the outside observer, the light still travels with c, but then increases distance from its source much slower.

Alternatively, length contraction is another solution. Yes, the light travels away from you much slower (in his point of view), but the distance to the target, i.e. the length of the stick, is much shorter because of length contraction.

In reality, it's a wild mix of time dilation, length contraction, and a change of simultaneity  (events that happen at the same time in one frame don't in another) that will make things come out exactly right. And again, the way you have to think is not that all these weird effects conspire to magically fix the problems coincidentally just in the right way, but rather, that when you assume equivalence and constancy of the speed of light and allow for time and space to be non-constant, then you can *derive* these effects (with the help of some further constraints).

Edit: typo, minor clarification

[Sean Mirrsen]

There's no arbitrary limit to the car's speed, either along the road or along the Earth. All that matters is its speed relative to air, which resists its motion. An orbital observer seeing the car move along with Earth will see it move faster, but it'll have no meaning.

In space, however, you're all in the same boat. Two cars moving 200 kps away from each other will each perceive the other's speed as 400 kps. At lightspeed, both cars will disintegrate and become energy waves, but their speed relative to each other will still be their speeds combined. It makes no sense for the general point at which what I call "space friction" will turn matter back into energy to differ based on your speed relative to the object. I mean, really, consider it. The fact that you're moving at .5c in one direction and the car is accelerating to 1c in another won't make the car disintegrate at .5c just because it's travelling at 1c for you.

ninja-edit: alright, simultaneity. But why take an illogical theory as a base? With the amount of holes you have to plug using time dilation and length contraction, even dissimultaneity, is it not easier to assume that speed of light is just constant, pronto? Use alternative theories to explain time dilation, for example I harbor a theory that matter as it is is simply energy weaved into a pattern. Chunks of energy moving at relativistic speeds, or spinning, as it were, make particles. Have an object move at a significant speed, and ambient energy of the universe will begin to affect the matter, just like air would affect an open mechanical clock, slowing it down. It's all very sketchy, since I lack the dedication to sit down and attempt to make sense of it, god forbid actually write it down, but it also seems consistent. Thinking up clauses and thinking up solutions to them is one of my favorite pastimes when I want to rest.

[Ampersand]

Antimatter does not have negative mass. It as opposite electric charges. Antimatter electrons have positive charges, antimatter protons have negative charges. The same holds true at the quark level.

I have no idea where people got the idea that it has negative mass.

You're thinking of Exotic Matter, which actually does have negative mass, but has yet to be discovered anywhere.

[Il Palazzo]

Use alternative theories to explain time dilation, for example I harbor a theory that matter as it is is simply energy weaved into a pattern. Chunks of energy moving at relativistic speeds, or spinning, as it were, make particles. Have an object move at a significant speed, and ambient energy of the universe will begin to affect the matter, just like air would affect an open mechanical clock, slowing it down. It's all very sketchy, since I lack the dedication to sit down and attempt to make sense of it, god forbid actually write it down, but it also seems consistent. Thinking up clauses and thinking up solutions to them is one of my favorite pastimes when I want to rest.

I don't care what maths or physics say about it, until there's definite experimental evidence of this, I refuse to believe it's right.

Besides, let's say, you're playing russian rulette, and after five turns without killing yourself or the other guy, you've got the revolver again. Somebody gives you a choice to quit or keep playing. Mathematics tells you that there is a bullet in the chamber, physics tell you that pulling the trigger will blow your brains out. But you'd still not believe it, because you need an experimental evidence?

You saying what you "feel" is right is no different than saying there are pink unicorns prancing on the Moon. All the estabilished physical theories are considered valid because they were mathematically and empirically tested to be internally consistent as well as agreeing with each other. You don't bother to sit down and proove yours, nor do you bother to sit and try to wrap your head around the e.g. non-Euclidean geometry(which would probably help you understand what dreiche was talking about), yet you don't accept other people's prooven theories. It's not only arrogant but just plain silly.