What JD said.

Where does the "mass" come from, emp? What experimental data is there to prove that this happens at all? (Honest question; it's not a field I keep up on too closely. There may be some--aside from particle accelerator experiments, which I'll get to presently. But clocks running at different times only demonstrates one part of the theory--and that's assuming even that data is correct.)

I reiterate: how do we *know* matter cannot travel faster than light? Einstein wasn't god; he wasn't working under divine revelation. At the very least, let somebody set up the experiment I described and see what *does* happen. Maybe it confirms old Al, maybe it doesn't. After all, Newton was "right" for hundreds of years... until someone came along and demonstrated otherwise.

As for photons only ever traveling the speed of light: (1) in a way, this statement is redundant, since photons are light and vice versa (okay, that's oversimplifying--they're electromagnetic radiation quanta... or waves... or both...), so of course they only ever travel the speed of light: that's like saying that cars only ever travel the speed of cars; which brings us to (2) check out recent experiments that seem (I cannot strongly enough emphasize "seem" here, regardless of how I feel about Einstein's predictions) to show that lasers can be accelerated beyond the "speed of light," that is to say they seemed to move faster than 186K mps.

The ion's "weight" increases? I assume you mean mass? How do they measure this? You can't take it out and put it on a scale. Do they measure based on the energy released when the thing hits a target? Pardon my naivete, but I would expect a proton moving at near lightspeed to have a bit more energy than one at rest. The question is how great the difference is: does it have more energy than it ought to have based on the speed it was traveling? (Again, honest question. I would guess that it must, if no one else has ever come forward and brought up the points I did--but that still doesn't prove that an object can't be accelerated beyond lightspeed, only that there are problems in doing so.) Where does this extra "mass" come from? If it is really "mass," would it be retained if the particle was decelerated to a rest state? If not, where does it go? (Energy can neither be created nor destroyed etc.) And if it does "go away," why? (I could throw in about twenty other questions that would logically arise from this one situation, but I'll keep it to a few at a time.)

To go all the way back to your original question, however... it wouldn't matter if you were using antimatter or not. Either it is possible, regardless of the fuel (theoretically, at least--some fuels would be so inefficient that you'd reach the point where you'd need more fuel to move the fuel load than would make the attempt worth it), to exceed the speed of light, or else it is not possible, again regardless of the fuel. Antimatter would also be no better a "power source" for opening wormholes, warping space, etc. for the same reasons--assuming that any of these things can be done. It has no properties that separate it from other matter beyond its efficiency level with regard to the amount of energy released in its consumption.

I would still like to see an explanation of the basic question underlying my suggestion, though: what is so special about the speed of light that it is a "privileged" speed? It would be less of a question if the theory stated simply that it represented an absolute speed for anything existing in the universe--although it would still be question-begging without an explanation as to why this should be. However, as you pointed out, the theory also states that "objects traveling faster than the speed of light can not travel slower." This implies the recognition that, at least theoretically, such "objects" (which, presumably, cannot be made up of "matter" as we understand it) could exist (okay, everybody: don't start talking tachyons at me unless you're ready to back it up with evidence...). What, then, makes 186Kmps so special that only one type of thing in the entire universe can travel at this exact speed, and everything else has to be going either faster or slower than that, but nothing can possibly do both?

Good catch! That would be a 3,600 times error...

I hope we do find a road to WARP - it would be interesting to see "what's really out there."

You're asking an awful lot in that post. What you need is a full treatment of Relativity (and the EM theory behind it): you need to read a book about it. Then you will understand "what is so special about the speed of light." And you will understand the enormity of the experimental evidence that supports it.

One snippet though: with a particle accelerator, you can accelerate massive objects to extremely high fractions of the speed of light and measure the energy required to do so. Its then easy to check this information against Relativity's predictions.

As others have pointed out, it has been done, with individual atoms.

Rather than just the relativistic mass issue, which has been covered, what cemented it for me that time dilation is a real phenomenon is that, due to the nature of what they use these particle accelerators for, they've built a whole bunch of really fast-moving unstable particles.

Slam a couple of particles into a surface, so that some unstable ions go flying out the far side. Place the detectors a known distance away. You know the velocity the unstable ions were going, because you know the time between the collision and the detection. You know that the time elapsed was ten times the half-life of the ion. You know that, according to Einstein, said particle should only think one half-life has elapsed.

Guess what, 50% of the time the particle makes it to the detector without decaying.

No i mean "weight" thats why i put the " " around it. I was talking about the increase of relative mass in the ion as its increased from a rest state.

And can i just state, traveling faster then the speed of light is IMPOSSIBLE using acceleration. Warping space, worm holes what ever you want could do it but using a fuel to do it wont! once you go faster then the speed of light entropy will work backwards and then that will slow you down below the speed of light. So unless you find a fuel source that uses reverse entropy below the speed of light your not going any faster then it.

Also for the increasing mass can i just say that as far as i know, when an atom accelerates its mass moves out of 4 dimensions and into 3. As the speed increases it makes more of a foot print in our present, theirs an X^2 gradient to compete with but i think it is actualy X^4 gradient to break with acceleration. Im not sure about the exact details of it but i do know that every meter per hour you accelerate gives an exponential growth of energy needed and and exponential growth in the amount of fuel required to accelerate something that fast. All this energy is stored in the ion and if it can't emmit this energy via entropy it is stuck with it until it is released (ie: hitting a wall)

Okay first your making assumptions and one that i personaly find rather insulting. Im a christian and saying someone isn't working under devine right is an insult to anyone who is a good person, Simple fact and please leave references of religion out of this. if you have to mention it, mention it on the BABBling forum which tolerates it aslong as it isn't a heated debate.

Einstein was a genious and as i've stated traveling faster then the speed of light is impossible for anything that uses our laws of entropy if things used reverse entropy and time was running backwards it would work. But you still wouldn't be able to pass between the two. FTL travel is mean't to be strapping an afterburner on the back of your ship and jumping there it isn't possible.

oh i forgot to say, Newton was never actualy wrong and will remain right until we see otherwise for his theorys are all correct in clasical physics. he was just talking about the physics that where real when he was round. hope this helps in your statements next time.

You're also assuming that antimatter is required.

Aside from that, you can't warp empty space-time... there's nothing there to act upon.

Of course, you can effect the stuff IN space-time, but technically that's not "warping".

Regards,
Ian Tresman
Derby, UK

Put me in the probably not possible group...

Saddly, I am also dubious that even purposeful interstellar travel is possible...

Having said that, I can not totally rule out interstellar travel.

First, since a wormhole of meaningful size, to tranport a human cargo, is not possible, maybe we can find a workaround. Solar power still seems to be the way to go. Possibly, some day in the future will make stable, tiny wormholes. Drop one half of the thing into the sun, the other half into a reaction chamber, you have a rocket powersupply with nearly infinite power and reaction mass, just need some way to contain all the energy you release(Also assumes you can keep it open with access to only one side). With this type of system, you no longer need to cary your reaction mass, so near C speeds are possible. Just need to make sure wormholes (even tiny ones) are possible.

Second, since we are making wormholes, why not artifical blackholes? In the next 20-30 years, we might be making tiny sub-plank width black holes in the next generation of particle accelerators. If we can build one of these devices in a space ship, and make a type of black hole laser, it seems warping space via frame dragging might just be possible. If artifical black holes are possible, this might be an option sooner than anyone expects.

One final thing abaut causality. Time travel does not have to make sense to our limited minds. It only has to be consistent in the quantum realm. So your ability to kill your grandfather while continuing to exist may be confusing, it may even seem illogical, but as long as the quantum realm is satisfied, it is possible, just dont expect anyone to recognise you when you get home. Prior to the discovery of blackholes cosmologists rationalized all sorts of reasons that black holes couldn't exist, because they defy logic, and seemed irrational. I suspect the same is true for time travel.

Hey, Jerry - this guy's onto something! Don't know what, but I know it's rocket science!

Yes quantum physics is an odd subject. one of its implications is that one day i wake up and forget to open my door i could still walk to the bathroom undisturbed. Theirs a one in well its hard to put a number on but it would take walking into a wall for nearly eternity before you would suddenly walk through it. Altering this property or aligning all the atoms so they could would allow this to be simple practice.

Also on the worm hole side of things a large one would be highly highly highly improbabable. But creating a small one is simple in string theory. Teleportation technology is on the way and already teleported an atom. Once this is done the information could be sent between a worm hole and recreated at the other side. simple

Hey dont get me wrong, Im all for teleportation, Just you go first ok?

Well Geordi once said something along the lines of transporters being the safest means of transportation.

I decided to do a google search on the technology behind star trek transporters, and came up with this interesting website that also goes into detail on many other technologies they use.

http://www.ex-astris-scientia.org/treknology2.htm

But when you consider all of the transporter accidents that happen in star trek, it really makes you wonder how safe the technology really is.

__________________
Obedience brings victory
Victory is life
That is the order of things

A single electron is accelerated using magnetic fields (I'm simplifying). It is not much different than the CRT tube, only you keep on accelerating...for miles! The electron can be bent into a ring using megnetism, just as the CRT uses magnets to scan the target accross the screen.
Now, by bending it into a circle, it can come back through the kicker again and again and again, and you can keep pumping more and more energy into it.
It is apparent when getting it to work right that each kick adds less and less to the speed. It's getting harder to push! That is, "heavier". Now there might be more than one possible hypothesis for this effect, given the mechanism's specific workings.
But, here is the clincher: The magnets used to bend the electron's path also have a harder time pulling on it. You have to tune the strength of the field as if the particle being aimed is heavier.

That is just one example, one that was run into as a real engineering problem early on. The tech's quickly learned to trust what the theory geeks were telling them! It just doesn't work if you don't plan for this effect.

Special Relativity has been tested so many times in so many ways, it is found to be one of the most successful theories ever.

See above. All objects accellerated to near the speed of light behave exactly as predicted. Unless you are trying to say that a large object behaves differently than a small one, even when the large one is made up of many instances of the small one and nothing else; stop wondering. It has been done, many times. The results back up the math, perfectly.



You'll have to post a more specific citation. In the mean time, I offer the usual reasons for such stories: (1) the guy is a quack; (2) the news report messed it up rather badly.


See the ring example above. That's two ways to notice the effect without stopping the thing to weigh it.


Ah, an excellent suggetion. Let's look into that.

How hard the thing hit the target is a function of the kenetic energy, which is mass times velocity squared. But... I know how much energy I pushed it with, so stopping it will release the same amount. It doesn't tell you how much of that energy was in the form of the velocity and how much was in the form of its mass. If you also noted the velocity, perhaps from the time it takes it to go around the ring (something you need to know to sync the kicks), you can indeed figure out that the velocity is lower than expected given that much of a push, while the total energy is the same so it didn't leak out anywhere.

In and of itself, I'd call that a strong clue but not enough to consider it prooved. Combine that with the sideways magnet data, and you have something worth publishing: the experiment is consistent with the mass increasing.


You ask if the difference is significant enough to measure. Well, when it gets close to the speed of light, very much so. The velocity difference between 0.9c and 0.999c is very small; about 1%. But the mass goes up by (excersize for the reader: crank though the function for "gamma" and post what you get). Enough to notice? Repeat with 0.999999c.


OK, there is no extra mass.

That is an explaination which makes it easy to calculate the behavior of the ring discussed above, but is confusing and misleading and falls short of acting like mass ought to. So, physicists don't call it that anymore. Mass is rest mass.

Instead, the formula for accelleration needs to be updated. F=ma is missing a term which is near zero for our normal experience so it was never noticed before the electronic age.

Refine the conclusions from the ring experiment, or at least the way of understanding it. Instead of saying "First, adjust the value of m by a factor r, then use F=ma as we've been doing for hundreds of years", say "F=r ma" where r is exactly the same thing.

Small difference, you say; but it clears things up because velocity (and hense r) is a vector quantity; it must be figured relative to the direction of the applied F. And you don't have to ask where the mass "comes from". Asking why F=r m a is no worse than asking why F=ma, and does not introduce a new mystery.



A full treatment explaining what is special about the speed of light needs a book to explain. I suggest you find one and buy it. Then ask more questions!

Given that things are indeed as Special Relativity would comput it, substitute the function for r (which involves the velocity v) into F=r m a and solve for F with v something greater than c. Try it.

Now the function works for 0.9 c, 0.999999c, and everything else. There are no signs that it fails for something even closer to c, but I admit extrapolation is where theories fail.

I said "get a book" but I'm answering this section too just to address the "greater than c can't slow down" thing. That is confusing you, and you should not worry about it. If you get into the math above, you'll see that nothing can go faster than c. But... play some games with the math. Mass is a "real" number. What if you work the function with m as an "imaginary" number? What would be the behavior of such things, if they existed? A game, and an example of thinking outside of the box, as is good during a creative process. But such tacyons as they are called are not matter as we know it.

Good luck in your studies!
--John

Another good point John Dlugosz =D> =D> =D>

I have a simple explination, the guy aimed a laser through a glass box he'd attatched a vacuum pump to and never noticed.

The only time i know of photons traveling faster then light is when it was transported instantly across a room using early teleporter technology that they are developing.

As for the tachyon by quantem laws it can and must exist IIRC. In the quantem world objects can pass through solid matter with relative ease (gamma rays through matter for one example of objects traveling through matter) also quantem physics dictates that if you spend near eternity walking into a wall sooner or later depending on your "luck" you will pass through the wall.

I also have to say to thurther back up the existance of tachyons is that nano bots have come under scruitiny because at their size there is problems of them running backwards which i thought fair enough bad design. Till i read the news item and found out that at their size it is a fact that entropy can run backwards for short periods of time. Were talking about objects the size of blood cells. scientists at CERN, i think it is, are trying to detect them using particle collidors and in theory should be detected before a collision. But may also not be due to entropy for nano bots running backwards then a tachyon could still travel forward in time because their entropy would work in reverse (rock + heat = jump instead of rock + fall = heat) but with time working backwards faster then the speed of light it would be correct again. (rock + fall = heat)

I understand that and it makes my brain go :x #-o 8-[

There's no place for it in the Standard Model. If it doesn't interact in any way whatsoever with our stuff, it might as well be in another universe. How can we say that "exists"?


Gamma rays are stopped by a sheet of paper.

X-rays, of the kind used by medical doctors, is probably what you meant. They can pass through water but are stopped by lead.

I don't see what that has to do with anything having an imaginary mass.

Machines built on this scale, such as the ribosome which reads a program on DNA and constructs a protein as encoded, will run backward as well as forward. No friction, you see; and the machine just floats around with raw materials just randomly bumping into it. The output assembly is the same way.

The normal way of getting reactions to run in the right direction is to pick up the outputs rather than leaving them laying around where they might fall back in; and keep an ample supply of inputs so each input location is immediatly primed again as it is used.

That is, you make sure that there is an unballance and entropy will cause them to move in the direction to restore the ballance. Entropy doesn't go backwards. You arrange for one side or the other to be "uphill" as desired. If it is in equilibrium, then it randomly moves one way or the other dancing around that center spot.

Some reactions do run in one direction--once the parts are put together, they stick tightly, so the same mechanism that gentely puts it together can't pull them apart even if it went through the motions. Well, unless you raise the temperature...


A citation, please? That sounds like a headline from a tabloid or something from a SF movie. My Bogo-meter is reading rather high for that statement.


Time or entropy doesn't run backwards. If you add energy to a rock it could rise against the potential, but that's because you took it out of equilibrium and applied energy. Energy you had to get from somewhere.

If there were any such thing as a tachyon, it could not be detected. It doesn't respond to any of the 4 forces, nor does it participate in any reaction. So how can you detect it?

Only if the paper is taped to a big piece of lead. You might be thinking of alpha particles.

Because quantem physics demands it as far as im aware. the quantem world isn't our reality if you think it is then your completly wrong. Simple fact photons behave as both a particle and wave when they can't be both just as long as they are not being observed by a conciousness.

Erm excuse me... WHAT?!? Alpha particles are stopped by paper, beta particles are stopped by tin foil.
Gamma rays are stopped by 15 inches of lead IIRC or 37.5cm of lead. may be a bit off not good at metric imperial conversions.

X-Rays are stopped by denser objects. Gamma rays are ultra high energy photons or quanta, when these hit an electron it jumps energy level and emits it again dropping back down. As this process goes on the photon loses energy and at the other end of the object (say lead) has either being completly abosorbed by the material or is slowed down enough that no harmful photons are emitted.


Entropy does run backwards! im sorry but its been done in a laboratory and the whole of nano robotics wouldn't be in panic over this. If they cant fix the problem a nano bot would run backwards as in do damage to the body not heal it.

My citation for the search for tachyons was a television program. An american research company under the department of nuclear energy or something like that im not into keeping up with all the american government branches is in search of tachyons using particle collidors and want to discover them before the particle collidor at CERN are completed.


Erm yes it does. If you travel faster then the speed of light then time does run backwards its stated by special relativity IIRC and also 1000's of sci-fi writers who ignore that if time runs backwards so does entropy. Tachyons are thought to be negative mass particles and there thore will have inverted entropy. If they existed slower then the speed of light when they hit an object the energy would come out of the object not the tachyon, so it has to exist faster then the speed of light so when it hits an object it gives off energy because entropy is running in reverse twice. (once because of backwards time and the other because of its negative mass giving it negative entropy.)

Rock + heat = jump, never happens as heat is vibration of particles, if they all moved in one direction they would jump.
My book "in search of schrodinger's cat" says that exact quote as its where i took it from. I will even find page reference exact quote and the works to state that on the sub atomic level entropy breaks down. Most of the time it runs forward but because of the size of the nanobots they can be effected by a reverse in entropy while a human being is too large for the effects to quantify in our bodys it would almost litrally be a second of infinity till it would happen it is so improbable but not impossible.

Oh and you can search for reverse entropy yourself in nano bots its on www.iop.org it was one or two years ago IIRC i can't be sure though so happy hunting for it cause thats where i read it.

IOP has always done me right to keep me informed on the news in physics when i read it regularly

I had a look at the abstract of the article Experimental Demonstration of Violations of the Second Law of Thermodynamics for Small Systems and Short Time Scales (G Wang et al, Phys. Rev. Lett., 89, 050601 (2002)), which says at the end: "Our results show entropy consumption can occur over colloidal length and time scales."
(Which means that thermodynamics can run "backwards" over small length and time scales.)

The IOP article says:
"Evans and colleagues say that their discovery could be important in the design of nanomachines. They also point out that as thermodynamic systems become smaller, the probability that they will run ‘in reverse’ increases, and this could improve our understanding of how many small biological systems – such as ‘protein motors’ – work."

In what world do you think we live in?
Are we not made of atoms and molecules?

__________________
papageno


"Why waste time learning, when ignorance is instantaneous?" - Hobbes (Calvin and Hobbes)

"It's all about context!" - Vince Noir (The Mighty Boosh)

"I've never heard of such a brutal and shocking injustice that I cared so little about!" - Zapp Brannigan (Futurama)

"...because the logic of the lines traced from reality is as poor of aesthetic value as it is strict in consistency. " - Paolo Bozzi (Naive Physics - free translation)

I mean that our world you drop a plate and it smashes instead of a smashed plate suddenly reassembles and jumps into your hand.

I was just saying that our world of the planets and the stars is different to the world of atoms. We use classical physics to investigate our universe and it works correctly (apart from the dark matter problem) where as the quantem world is one of chances all of which are lived out. Every possibility happens aslong as an observer isn't watching but if there is then it makes a decision... very odd but very cool.

Sorry for the misunderstanding

This interpretation of the theory is not the most accepted by physicists.

For macroscopic length-scales a quantum system becomes a classical system (Ehrenfest's theorem), without the need of a consciousness.
And the point were quantum becomes classical is not clearcut nor depends on a conscious observer (superconductors are quantum systems at macroscopic length-scales and they stay so even if I look at them).

Nowadays the trend among physicists is to blame decoherence.
A macroscopic system is made of a large number of particles, all interacting with each other and with the environment. All these interactions "degrade" the coherence of the system on macroscopic scales very quickly, thus turning the system into something more classical.

__________________
papageno


"Why waste time learning, when ignorance is instantaneous?" - Hobbes (Calvin and Hobbes)

"It's all about context!" - Vince Noir (The Mighty Boosh)

"I've never heard of such a brutal and shocking injustice that I cared so little about!" - Zapp Brannigan (Futurama)

"...because the logic of the lines traced from reality is as poor of aesthetic value as it is strict in consistency. " - Paolo Bozzi (Naive Physics - free translation)

All: thanks for the many inputs. I'm glad I inspired some discussion. I'm afraid I'll have to wait until later to respond to specific posts.

One immediate one, though: I don't see why anyone should be offended when I said that "Einstein wasn't God." This in no way demeans God (or Gods, or no God at all, depending on your preference--and I won't give mine, nor ask anyone else's, since this *isn't* a religion forum). I'll amend the second part of that sentence to: I do not see any evidence, nor has anyone I am aware of suggested, that Einstein was working under divine revelation. He was "just" a scientist--a brilliant one at that--as far as I know, or am concerned. By this, I only meant to say that it is possible that Einstein was "wrong" (i.e. that he wasn't omniscient)--or, to be more parallel to the Newton example, that his model is incomplete.

By the way, I *have* read "books" "explaining" relativity. Most of them give me the impression that the writer did not really fully *understand* what he/she was talking about, but was only reiterating what someone else had said before... which was not all that helpful. (Question: can anyone refer me to a good, *complete* explanation of relativity? Perhaps that would help me out.) I'm not arguing with the math--in point of fact, I can't assess all of it: my brain melted down somewhere in college algebra, although I can still make use of most of the formulae. But Newton's math was correct, too... up to a point, as several people have pointed out. What I was saying/suggesting is that perhaps we need to reexamine the conclusions stemming from the math, and if necessary amend them.

As for the parallel string on quantum physics: I have a real problem with the idea that things behave one way when observed and (possibly) another way when they aren't. (Yes, I know there is experimental data that seems to show this... or at least imply it: after all, once you conduct the experiment, the thing has been observed.) Saying that things behave differently when observed is nothing more than the old "if a tree falls in the forest" question again. Is there anyone out there who doubts that it makes a sound? You can say that the behavior of a particle is not perfectly predictable, that you can't *know* exactly how it is behaving at the present moment, until you observe it--but that's not the same thing; that's just Heisenberg's Uncertainty Principle. (Perhaps I should put "just" in scare quotes, since this principle was, if I understand correctly, the launching point for quantum mechanics....) And I find myself equally unable to accept the idea that I might someday be able to walk through a solid object if I just try it often enough. Science depends on repeatable observations for its conclusions; how often do we have to have one solid object hit another before we accept that it will never pass through it? (I'm talking comparatively large bodies, not single particles, here: since most of subatomic "space" is "empty"--i.e. there are no physical bodies that will block the passage of something the size of one of the building blocks of what little "solid matter" there is in that space--it comes as no surprise to me that sometimes a particle will not intersect anything that can block it. In fact, it would be most enlightening to determine exactly how massive something can be before it can pass through anything: consider the posts on alpha, beta and gamma radiation. If a helium nucleus can pass through some matter some of the time, what about a lithium nucleus? beryllium? etc.)

In fact, my instinct (no, I have no proof) is that this "observer phenomenon" is, or could be, a problem with regard to relativity as well. How well do General/Special Relativity and quantum mechanics mix? Do any of the answers have any bearings on any of my previous questions?

That is incorrect (or so imprecisely worded as to be incorrect).

Accelerating an object gives it more kinetic energy. The total energy of an object is related to the mass quite simply by the classic E = mc^2, so increasing the energy increases the mass. And it is the energy tensor that is the source term in the Einstein equations of General Relativity. An object with more energy generates a stronger bending of space. So the relativistic mass increase does indeed make the object "have more gravity".

Addendum: Einstein's equivalence principle wouldn't hold if the gravitational mass-energy did not increase to match its inertial mass-energy. (You'd have \gamma m_0 on one side of the equations of motion and just m_0 on the other.)

How would you word it / explain it correctly?

That is, howcome I don't collapse into a black hole because in your reference frame I'm moving so fast as to be so massive?

I understand that I look flattened from your point of view, using the common space-time diagrams. But how can an object transform into a totally different kind of object depending on a point of view?

If a small object passes a larger one, the formula for the force of gravity between them would give different results if the small one gained mass or if the large one gained mass. How does that work itself out, if "gaining mass" is taken at face value?

Well, I tried above, but let me elaborate. And while I've never heard of physicists in GR dropping the term mass, I'll admit one needs to be careful when using it pedagogically.

Energy and mass are exactly the same thing: E = m. (I've dropped the c^2 factor since that only arises from our choice of units; if we chose to measure time in meters or distance in seconds, c = 1 with no units.) So let's always remind ourselves of this by referring only to mass-energy in what immediately follows.

The total mass-energy of an object comes from several sources; it is the sum of the object's kinetic mass-energy, all of its interaction (potential) mass-energies, and its rest mass-energy. The rest mass-energy is intrinsic to an object and will be constant in time and the same in all reference frames. The other terms can change. For an object moving non-relativistically, the rest mass-energy term is dominant.

The amount of inertia an object has and the magnitude of its gravitational effects are both functions of the total mass-energy, not just the rest mass-energy. That's just the way the equations are written, and they work. (You were basically asserting that the intertia is determined by the mass-energy but the gravitational effect is given by just the rest mass-energy. This violates the principle of equivalence which underlies GR.)

The object doesn't transform into a different kind of object; it is the same kind of object with a different mass. We are used to thinking of the mass of the object as intrinsic because in our everyday world the mass is essentially equal to the rest mass (which is intrinsic). But the total mass of an object is not intrinsic to the object.

No, the formula for the force between them would be the same in either frame.

Let's take the small object as having rest mass m, the large object as having rest mass M, and their relative velocity as described by the relativistic factor \gamma. (I'll also use the Newtonian gravity formulas here; strictly speaking we should use GR to describe gravity for relativistic motions, but Newtonian gravity is still generally an excellent, and more than adequate, first approximation.)

Then in the (instantaneous) rest frame of the large object, its mass is M and the small object's mass is \gamma m. The gravitational force is thus G M (\gamma m)/r^2. In the rest frame of the small object, it has mass m and large object's mass is \gamma M. The gravitational force is thus G (\gamma M) m /r^2, exactly the same. (Exercise for the reader: Suppose we're in a third reference frame moving at velocities giving relativistic factors \gamma_1 and \gamma_2 for m and M, respectively. Use the velocity addition formulas to show that \gamma1 * \gamma 2 = \gamma, as it must for the force to be the same.)

This answer to this question is a bit more subtle, and I want to calculate something to be certain of my answer before I respond. I will get back to you.

John, I will add that most of your explanations in this thread have been correct and lucid. I wouldn't give this detailed a response to someone who I thought was an idiot.

Everything was created by the "gods" so in turn is part of those "gods". I used " " as in turn we could have created ourselves. Sounds odd i know but its one explination of how the universe formed as quantem physics needs an observer for things to happen.
If our creation is ahead of light from the BB then its possible for us to observe it and this would force the decisions to be made. I think the delayed-choice double-slit experiment proved it but i can't be 100% sure on that i just found it said while i was surfing through the web. So in a sense we would have created the universe by just sitting back and been lazy... everything can be solved by relaxing and drinking a brewskie

Physician, heal thyself.

I've finally unpacked my GR books and am working on answering John Dlugosz's questions above. The problem is much trickier than I thought. I'll get back to you, because this has become quite intriguing to me. :-s

(Edited on 9/27 to remove the following disclaimer, which proved unnecessary, see post below: "and it may yet turn out that, to first order, I was wrong.")

I don't think anyone quite answered your question, but here's a starting point that I think might help: Maxwell developed equations that described the effects that electric and magnetic fields have on each other, which in turn described the behavior of electromagnetic waves (e.g. radio waves) in a vacuum. Out of those equations came a factor c derived from the permeability (a magnetic constant) and permittivity (an electrostatic constant) of a vacuum (c=1/(permeability*permittivity)^^.5), which was equal to the speed of propagation of the electromagnetic wave. It turned out that the speed (c = 299792458 meter/second) was the same as what was experimentally determined to be the speed of light. So, there was this big "aha" moment where physicists realized that light must be an electromagnetic wave (years, of course, before QM suggested that was only half the story, but that's another topic ). So, the theory goes, if the permittivity and permeability of the vacuum are the same in all reference frames, then the speed of light must be the same in all reference frames.

However, this also implies that any disturbance that can propagate through a vacuum would possess the same property. So can there be another disturbance that propagates through a vacuum at a speed other than c? Conventional physics says no, but as far as I can tell, all arguments that explain why not are circular. And now that I think about it, despite the brief Maxwellian detour, we are really just back to your original question. Which makes this post just as circular!

Well, that's part of it, and thank you for a straight, informative answer. But what I was getting at--and hoping someone else would pick up on--was even more fundamental.

Ignore the math. I don't care if it works. I don't even care if it's right--which, by the way, is something completely different. Don't worry about "proofs" of the theory. What motivated my question is this: *why* is the speed of light priveleged? All the Lorenz transformations in the world can only show *that* it is, not *why* it is. Why, for that matter, is it the speed it is? Why not, say, 187,000 mps, instead of 186,000? (No, that's not quite like asking "Why is water wet?"--though that deserves a complex, well-reasoned and well-grounded answer as well... and one that I can come at least slightly closer to giving. At least there *is* an answer.) And why can't anything else ever reach that speed? I know, I know: energy requirement increases to infinity... but *why does it?*

That's the real motivation behind the question. I think that, if we actually understood the whys behind the whats, we'd be a lot closer to answering a lot of other questions. (So often true....)

Does that help? Anybody help me on this?