Hey guys, today I found a great thought experiment to prove that time can't exist without mass and motion. It can be found by proving photon's rest mass = 0. I don't know the actual derivation. So, I have made my own derivation (this is the one I made to prove photon's m = 0 to my friend). Let's start: E=mc^2 (Rest energy equation) E/c^2=m=0 (To prove) We know that c^2 is a constant so if we want to prove m=0, we will have to prove E=0. Let's take another formula: E=hv So, we can prove it by this equation. As we are taking the photon to be at rest, there is no frequency at rest. It will have no frequency. So, we will get E=h*0=0. Putting it in the previous equation, we get m=0. That's how I proved it. But today I thought that in this way everything at rest will vanish from the universe. Okay let's take this experiment. Suppose we stop every matter in the universe. Then everything will vanish according to the above proof. So, anybody outside the universe will never be able to sense that there's a thing like time. And this state of stopping everything can be achieved by stopping time. Everything will come to rest and will vanish from the universe. Hence, we can derive that mass and motion can only exist when time exists or conversely time only exists when mass and motion exist. If time exists and mass and motion don't exist, then we can never feel time. We get that feeling when anything comes into motion. So, both are true. Thouhts please.
You can't do this, since the photon is never at rest. It always moves at precisely the speed of light.
But nevertheless Lakshya a good try! Keep asking questions and finding of new ways of thinking about things and you will soon advance in your understanding. Perhaps, who knows, one day you might discover that Theory of Everything! (Lakshya is only 13 years old!) Garth
Indeed. Welcome to the forums Lakshya (although I note you've been around a while, I've not noticed any of your posts, especially in cosmology). I hope you enjoy it here; there are many knowledgable people who will help you learn. [As an aside, you may wish to take your address out of your profile.]
I know what you mean. It is the usual thing, for privacy sake. Anonymity is the usual fashion. But if someone does not intend to get into heated arguments I see no particular reason for anonymity. As I recall from seeing photographs, Chandigarh is one of the most beautiful cities in the world architecturally, so for someone to live on "Chandigarh Road" is kind of nice. It has a certain style. Also the Punjab is a famous region---which has been the home of successful merchants and great fighters. I would at least hope that this young person would keep the "in the Punjab" part of his public profile location. ============ Come to think of it, can you beat "Police Colony Lane" for a distinguished historical patina? To me it has a kind of British Empire sound to it. Damned if I wouldn't keep the whole thing as it is, if it was my address!
I agree that there is no need to be anonymous (I imagine many people could find out who I am if they really want to). However, I was more thinking that, due to Lakshya's age, it would be a lot safer for him not to publish his address in his profile. I would not advise any young person to divulge such information over the internet.
Now, you all guys are making me angry. You are conversing about my address. This is not a place to discuss addresses. I know that you all are appreciating me but I posted it here just to find anomalies in it. I want to correct them. So, I request you all to find anomalies in it or some instances where it doesn't apply or find some mistakes in it.
Calma, Lakshya! Shouldn't this thread be in the "relativity" forum? This doesn't make any sense. I think you meant to say: "What do you guys think of the following attempt to prove that the rest mass of a photon is zero?" Unfortunately, the first equation only applies to a body at rest wrt some inertial observer, not to a photon, which can never be at rest wrt any inertial observer. See Taylor & Wheeler, Spacetime Physics, first edition (which covers k-calculus) for clear explanations of special relativity. I realize that you say you are 13; what matters more is what math you already know. But in any case, this textbook requires only minimal background. Enjoy!
This is athought experiment so we can say a photon to be at rest as in a thought experiment we can do anything. The observer in this thought experiment is outside the universe which you can consider to be God.
Using God as a scapegoat is poor science. These theories appear to be contrived in such a way as to stop experiments like this one from taking place, but its just how it is :) If in a thought experiment you are able to do anything there is no point in conducting them as they have no bearing on reality. They might be interesting but ultimately irrelevant.
FunkyDwarf I don't think Lakshya was using God as a scapegoat, just using an "outside the universe" point of view, such as might be ascribed to God, to conduct his thought experiment. As a thirteen year old Lakshya's basic premise that "time can't exist without mass and motion" is a pretty mature one and not unlike Einstein's foundational concepts. He should be encouraged to think creatively, here at PF we can also help him to think critically with the discipline of the insight and knowledge of the subject. Lakshya let us take your initial suggestion: When you say "taking the photon to be at rest" you are treating the observer as if she were 'travelling on a light beam', this is called a "null-like" point-of-view. It was also Einstein's own thought experiment at the age of sixteen. (so you have beaten him to it by three years! ) You can read about it here. In fact objects with rest-mass cannot travel at the speed of light so it is only a thought experiment. What you have shown is that if a photon were stationary then it would have no energy and therefore it would not exist. You might want to go on to show that if photons have no rest mass then they have to travel at c. When you say "But today I thought that in this way everything at rest will vanish from the universe." you are extending the [itex]E = h\nu[/itex] equation to atomic particles as well as photons. This is a quantum mechanical treatment of particles and is called the de Broglie hypothesis. And indeed one way of looking at it would be that if there were no frequency, no time, then nothing could exist. Keep it up, I shall be waiting to read about that Theory of Everything! Garth
You know that I am taking the out of universe point of view as like God. So, if we are God then we can stop a photon and analyze it, although, I am an atheist. Thanks for your kind support and telling them the main idea I am using here.
The analogy is not inconsistent with Einstein's view. To a photon, the universe has no spatial dimensions. So, by it's own 'watch', a photon is stationary [a d/t thing].
For photon the universe is a single point. By it's own view no thing like space-time exists. In its world, only the photon that is himself exists. So there's no matter on discussing on rest of photon by it's own perspective.
Hi Lahshya! I have shown how your line of 'gedanken' or 'thought experiment' was similar to Einstein's as a sixteen year old, there was some 'mileage' in that line of reasoning, but it is limited. I suggest you reflect on Einstein's conclusion that it was a 'paradox'; light is a wave and waves need time to oscillate. However, in Einstein's Aarau vision he realised that if he travelled on a light ray travelling out and away from the village clock and 'looked back' the clock would appear to be stopped for the light ray carrying that information to him would be the one he was riding on! If time was stopped how could a oscillating wave exist? It cannot, you cannot have a photon at rest, it would cease to exist. You cannot stop a photon and keep it 'at rest', and you cannot catch up by travelling a light speed, as in Einstein's 'gedanken'. These conclusions are all consequences of the Special Theory of Relativity that Einstein developed by thinking on this paradox. Now we have to be serious and start again from first principles. It is because the other posters here are using those principles that they have said your argument in post #1 does not make sense, you are actually using the wrong equation for the energy of a moving particle/photon, it should be: [tex]E^2 = m^2 c^4 + p^2 c^2[/tex], where p is the relativistic momentum [tex]p = \frac{mv}{\sqrt{1 - v^2/c^2}}[/tex]. If the 'rest' mass m=0, as for a photon, this simplifies to E=pc which is the photon's energy. A photon therefore has momentum, p, but not rest mass,m, the equation for relativistic momentum here becomes singular as v = c and so a photon's momentum is simply defined as [tex]p = \frac{E}{c} = \frac{h\nu}{c}[/tex]. On the other hand, consider a particle with mass that is travelling at a velocity v, let an observer travel with that particle so the particle's velocity is zero in her frame of reference. Consequently in that frame p=0, so the rest energy simplifies to E=mc^{2}. I could go on to reproduce many of the excellent text books on the subject, but it is up to you to read them for yourself and learn. You can start with Ned Wright's tutorial on the internet here. Note when you said, you are adopting the standard space-time perspective of relativity in which the four dimensions of space and time are presented together as a continuum. In this perspective there is no 'passing of time', for time is already included in the space-time diagram, the continuum is seen to be static from a 'beyond space' and 'beyond time' perspective. It may be a relativist's perspective but it is not our normal human temporal experience perspective. So long as we are consistent as to which perspective we are using there is no paradox; paradoxes happen only when we confuse perspectives. I hope this helps, Garth
time can't exist without... fascinating! astrophysicist zeldovich reckowned something like this. he was a great believer in the construction of mathematical parody in order to divide up complex problem senarios into simple regimes. particularly see in stars and relativity book.
found an answer to explain to u what Iwant to say Look, suppose we are trying to know the mass of photon at rest. We don't know it's rest mass. So we put it in a thought experiment at rest and then examine the situation. And in my explanation, when we put it at rest, then we receive it's mass=0 and it can't be at rest what you gus are saying.
Right, a massless particle can't be at rest, so it cannot have and does not have a "rest mass", but it can and does have energy and momentum.