Wrong. You and I are currently in a gravitational field and not experiencing a huge acceleration.
Cite?
It will undergo a mass increase as perceived by an outside observer. Do you have any experimental results that suggest otherwise.
It’s not a fatal flaw, it’s just irrelevant.
Have the chest fall from one side of the Earth to the other, taking about 43 minutes, catching him just as he pops out of the hole. Have the free-fall portion of the person in the rocket be 43 minutes as well. Then the acceleration is in the opposite direction, for both people.
When the person in the rocket has to switch deceleration on the return leg, drop the person through the hole again, catching him on the other side. Both of them will experience the exact same time of free-fall, and exactly the same accelerations, in direction, magnitude, and duration.
It doesn’t matter, of course, the person in the rocket still ages less.
Thanks, ZenBeam. I’ll have to think about this a bit more, obviously. That’s why I like this kind of thread; I learn a lot.
After a freefall of 60 seconds from 17Km above the surface (of Earth), I would experience a huge acceleration. It was you yourself who pointed that out. On the rocket however, after a freefall of 60 seconds, I experience no such acceleration. Please don’t try to misrepresent me.
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It will undergo a mass increase as perceived by an outside observer. Do you have any experimental results that suggest otherwise.
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This is a total red herring. The only way an outside observer can detect the mass of (the chest in the) rocket is to interact with it by either slowing it down, speeding it up, or deflecting it off its course. To do any of those things he has to apply a force from his own FR, then the mass is indeed measured WRT that FR. All experiments which purport to show mass increase have been under those conditions. In this example the rocket is not receiving a force from any other FR, so to speak of a mass increase WRT an outside observer is meaningless and misleading. Do you have any experimental results which show an increase in mass when there is no interaction between FRs?
Can anybody please tell me why Hans Zweig’s disproof of the EQ which I posted previously is wrong?
To get an idea of the growing number of SRT dissenters, just browse the web.
You’d experience a huge deceleration because you encountered an outside object (the Earth). Since the claim was that there’d be no way to distinguish the two chests, based on experiments going on on the inside, a collision with a large outside object doesn’t count.
It’s your claim - you’re the one who should provide the evidence to support it.
The only way an outside observer can detect the mass of (the chest in the) rocket is to interact with it by either slowing it down, speeding it up, or deflecting it off its course. To do any of those things he has to apply a force from his own FR, then the mass is indeed measured WRT that FR. All experiments which purport to show mass increase have been under those conditions. In this example the rocket is not receiving a force from any other FR, so to speak of a mass increase WRT an outside observer is meaningless and misleading. Do you have any experimental results which show an increase in mass when there is no interaction between FRs?
Please answer the above, and comment on Hans Zweig’s disproof.
[QUOTE= Han Zweig]
To distinguish the force of gravity from such other forces consider an idealized experiment in which a train is moving along an embankment on a planet on which the force of gravity is negligible. In one case we let an engine accelerate the train. In a second case we imagine a large body ahead of the train which attracts the train due to its gravitational pull. We can also imagine this second case as a train falling, or racing, to earth.
If the train were in uniform motion then it would be valid to compare a walk forward on the train with a laser firing a pulse of light, or a gun shooting a bullet from the rear of the train in the direction of the train’s motion. The velocity of the walker, the bullet or the photon remains constant relative to the velocity of the train. But if the train is accelerating because of the engine pulling it this is no longer true. In that case the walker, at each step, is in touch with the instantaneous velocity of the train, so that his walk can remain essentially constant with respect to the instantaneous velocity of the accelerating train. But the bullet or the laser beam do not remain in contact with the train so their velocity will decrease relative to that of the accelerating train as time passes.
On the other hand, if the train were falling towards earth, or pulled forward by a large gravitational mass, the acceleration would be due to gravity and the bullet fired from the gun (and possibly the laser light) would also be subject to the continuing force of gravity so the velocity relative to that of the train would be constant as is the case for the walker. This differentiates the case of gravitational acceleration from the force producing acceleration that acts only on the train.
What is clear is that we have a distinction between a specific force operating on a specific body and a general force, the force of gravity, operating in an undifferentiated way on all bodies, objects, possibly even photons. Since the effects are different in the two cases we cannot claim that the force of gravity is the same as any other force that produces acceleration. The validity of General Relativity, like that of Special Relativity, can therefore be questioned.
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Zweig has misunderstood the thought experiment - he is not comparing two objects in free fall, one near a gravitational source, and one not; he is comparing an object being accelerated by a motor, and one object in free fall.
I think this will be my last post on the subject; I’ve done my best to explain relativity to you, and it’s stopped being entertaining and illuminating for me to continue the effort. I thank you for the interesting thought experiments - it was fun to analyze them and find out what was wrong with them, but I do have other things to do. If you want to declare victory, feel free.
I’ll repeat this one more time. It’s not a question of mass increase. That’s one way to look at the results. For a while it was standard in high school physics, but it’s now considered better not to use it as it’s only useful for part of physics.
What’s experimentally verified is that kinetic energy does not follow the classical formula .5mass(velocity relative to the observing frame)^2, but instead follows the relativity derived formula massc^2(1 - 1/sqrt(1 - (velocity relative to the observing frame)^2/c^2)
One reason relativistic mass has fallen out of favour as a concept is that it confuses more than it explains. And it has never been claimed to have internal effects in a reference frame. Since special relativity is about the relation between frames of reference it makes absolutely no sense to demand proof of its effects within a single reference frame.
He makes essentially the same mistake as you do – forgetting that the EQ is only valid locally. In a gravitational field, every massive object undergoes uniform acceleration. This is not generally the case in vessels propelled by an engine; especially, a passenger on a train is only accelerated by the train if he is in contact with it, and so is a bullet fired by him. The bullet does not experience the acceleration imparted by the train’s engine, and thus, its situation is not equivalent to that of an observer in a gravitational field; only if the bullet itself were accelerated locally, by say a tiny rocket tied to it with a string, would the equivalence principle apply.
Yes, he certainly is comparing an object being accelerated by a motor with an object in free fall. This is exactly what Einstein did. Re-read his original thought experiment in chapter XX.
[Quote HMHW]
He makes essentially the same mistake as you do – forgetting that the EQ is only valid locally. In a gravitational field, every massive object undergoes uniform acceleration. This is not generally the case in vessels propelled by an engine; especially, a passenger on a train is only accelerated by the train if he is in contact with it, and so is a bullet fired by him. The bullet does not experience the acceleration imparted by the train’s engine, and thus, its situation is not equivalent to that of an observer in a gravitational field; only if the bullet itself were accelerated locally, by say a tiny rocket tied to it with a string, would the equivalence principle apply.
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Same answer as to Andy L. Re-read chapter XX. Einstein had the man in the chest propelled by an engine (the hypothetical being pulling on the rope), and a man in a chest on Earth (if that is local enough for Einstein it is local enough for me and should be local enough for you). Re-read your own posting above, you have agreed with Hans Zweig that there is a difference, and stated correctly the reason why that is so. The bullet does not experience the acceleration imparted by the train’s engine, whereas the bullet does experience the acceleration imparted by gravity. This shows that there is a detectable difference between acceleration and gravity.
The man on the chest on Earth is not free-falling. This may be very controversialo to you, but di you know when your free-falling at or about the Earth’s surface you’re usually falling. The fact that the man in the chest on the Earth isn’t falling is what those few of us who care about such little details call a ‘dead giveaway’.
AndyL is correct the problem with Zweig’s ‘proof’ is entirely that he’s comapring the difference between a free-falling observer and an observer in an accelerated frame, whereas the equivalance principle is best stated as the local equivalnce between an inertial observer and a free-falling observer. I know Einstein choose to state it as the local equivalance between an accelerated observer and an observer being held still in a static gravitational field, which is fine as well. Notice though that there is not the same equivalnce between an acclerated and a free-falling observer.
I looked up Zweig’s proof a while ago, when you first mentioned it and tbh my first reaction was to laugh out loud, it’s such an elementary mistake.
What hope do these people have in their quest to disprove general relativity when they don’t even understand by far the easiest part of the theory to understand? I.e. the equivalnce principle.
You should go over those sentences again. First, you correctly state that the bullet does not experience the acceleration by the train engine; then you claim this implies a difference between acceleration and gravity. But of course, that can’t follow, since as you said, the bullet doesn’t experience any acceleration. If the bullet were accelerated uniformly and locally, then there would not be a difference in its behavior in this situation, and in the situation of it being fired in a gravitational field. In other words, the case in which there is no acceleration is distinct from the case of being in a gravitational field; which is a direct consequence of the principle of equivalence.
You really need to understand what ‘locally’ means in this context. If the accelerated observer has some means of detecting acceleration some ways away from him, he can always (or in most cases, at least) tell whether he is being accelerated by a motor, or is in a gravitational field. For one, gravitational fields are typically not uniform, which leads to tidal effects. If the observer’s experience goes beyond the local, he can, in principle at least, detect these. The bullet is such a going beyond the local (as it’s some distance away), though here it’s not tidal effects that give the sham away, but the fact that the acceleration is not imparted uniformly to every object. This isn’t in conflict with the equivalence principle, as it’s only valid locally.
Yes, I correctly state that the bullet does not experience the acceleration of the train engine. I also correctly state that the bullet does experience the acceleration caused by gravity. I have highlighted in red your sentence to clarify the point. The whole point is that the bullet IS NOT accelerated at all when the train is being accelerated by the engine, and there is a difference in its behaviour in a gravitational field and an accelerated field. Your last sentence makes no sense whatsoever in this context “the case in which there is no acceleration is distinct from the case of being in a gravitational field”. There is acceleration, so remove the word “no” and we are in agreement.
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These are my own pants. The man on the chest on Earth is not free-falling. This may be very controversialo to you, but di you know when your free-falling at or about the Earth’s surface you’re usually falling. The fact that the man in the chest on the Earth isn’t falling is what those few of us who care about such little details call a ‘dead giveaway’.
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Please concentrate on the relevant point, which in this case is the bullet.
The bullet is fired from a gun which could be solidly attached to the train and aligned so the bullet is projected in the same direction as the train ie forward. Now there is no need to assume a vertical gravity to hold the gun (walker) to the floor of the carriage. The gravity/ acceleration is orientated horizontally for clarity .
Scenario 1. There is an engine accelerating the train. The following sentence is then true :-
The bullet fired from the gun does not remain in contact with the train so it is not accelerated by the engine and its velocity will decrease relative to that of the accelerating train as time passes.
Scenario 2. The train is in a gravitational field (which is of the same orientation as the acceleration remember). The following sentence is then true :-
The bullet fired from the gun does not remain in contact with the train but like the train is still subject to the force of gravity, so the velocity of the bullet relative to that of the train is constant as time passes.
My goodness, how difficult is this to understand???
And yes of course I understand that the forces in question are directed ‘horizontally’ along the train.
Scenario 1 is an accelerated reference frame, agreed?
Scenario 2 is a free-falling reference frame, agreed?
The equivalnce principle does not state these two are equivalent.
The correct ‘equivalnce principle analog’ for scenario 1 is that the train is held stationary in the gravaitional field (i.e. at a constant distance from the mass that is pulling it) by some other force (e.g. in Einstein’s example the force holding the chest stationary is the reaction force between the chest and the Earth). The bullet isn’t subject to the force holding the train in place so it will be accelerated towards the source of gravity until it hits the train. I.e. there is a local equivalnce between an accelerated frame and a frame that is being held stationary in a gravitational field.
The correct ‘equivalnce priniciple analog’ for scenario 2 is the train and the bullet are both moving with the inertial motion so do not contact each other. I.e. there is a local equivalnce between a free falling frame and an inertial frame.
So if you make the correct comparisions (as opposed to the incorrect one made by Zweig and yourself), Hans Zweig’s sceanrio is just an illustration of the equivalnce principle in action. Which jsut goes to show how farcical Zweig’s ‘proof’ is.
Andy L 1…tomh 0
HMHW 1…tomh 0
The penny has dropped. I do give in gracefully when I am proved wrong. I have contacted Hans Zweig to inform him of his error, and await his reply. I will read “A Question of Time” again more critically, and look for other errors. Perhaps you could do the same.
There is still a lot wrong with SRT, so don’t expect a complete capitulation.
Well, I certainly didn’t expect that when I opened this thread! I think this is the first time I’ve seen somebody acknowledge an error after such a lengthy discussion; usually, both parties are too dug in at this point for something like that. Well done!
Unfortunately Hans has expended a huge amount of time and emotion in his work, and is very reluctant (at this time) to admit his error. I have pointed out to him what took me a while to grasp, that one man is experiencing 1G and one man is experiencing zero G. Bear in mind that this only invalidates this particular thought experiment, not others, and I will coninue to question SRT.
A typo at the end of my last posting. SRT should of course be just RT.
A few emails have bounced between myself and Hans, and I have re-read his work. I agreed with HMHW on the basis that the starting points were different - one man experienced 1G, while the other experienced zero G, so naturally the results would be different. But isn’t this the whole crux of the matter? What I forgot was that both trains were being pulled forward, one by gravity and one by an accelerating engine.
We are trying to decide if the effects of gravity and the effects of mechanical acceleration are different or the same. Hans deliberately chose his thought experiment to be different to Enstein’s. Hans has gravity pulling one train, and acceleration pulling another train. If gravity and acceleration are the same, then the effects should be the same. The result is that WRT a suitably placed IFR both trains are accelerating at (for example)1G, and if the observer in that IFR could not see the large gravitational mass pulling one, and the mechanical accelerator pulling the other, he would have no way of deciding which was which.
If one train is being accelerated by an engine pulling it, and one train is being accelerated by gravity pulling it (a large gravitational mass in front of the train), and the man on the train can detect a difference, that is all that is required to disprove the equavalence principle. As stated previously, one man is experiencing 1G while the other is experiencing zero G. That by itself is a detectable difference.
"If the train is accelerating because the engine is pulling it, the walker at each step is in touch with the instantaneous velocity of the train, so that his walk can remain essentially constant with respect to the instantaneous velocity of the accelerating train. But a bullet or a laser beam (fired forward) do not remain in contact with the train so their velocity will decrease relative to that of the accelerating train as time passes.
On the other hand, if the train were falling towards earth, or pulled forward by a large gravitational mass, the acceleration would be due to gravity and the bullet fired from the gun (and possibly the laser light) would also be subject to the continuing force of gravity so the velocity relative to that of the train would be constant as is the case for the walker. This differentiates the case of gravitational acceleration from the force producing acceleration that acts only on the train."
Please peruse this carefully - I have.
I don’t like fighting on two fronts, so we will thrash this out before moving on to discussing my web page, which I am altering slightly.