Relativity

How can the speed of light be constant when one of its factors - time -( per second) is not ?

Ok so there, I'm trying to figure out how its possible for frame of reference B, to think that time is going slow for frame of reference A. But also, at the same time, Reference A can logically say time has slowed for reference B. I can understand the first graph. B says "I'm stationary" So A moving past my 2 clocks (Which are synced) will take less time because his clock is moving slower. So in "B"s mind, it only took A 45 minutes to travel what "B" see's as an hour's distance. That makes sense to me. But the bottom graph, with A stationary with the 2 B clocks moving past. "A" will see 1 hour pass between the B1 passing, and the B2 passing, but in "…

I am a physics graduate, so I know a little. But I have forgotton most of it in the past 20 years. I had the following thought experiment that I thought I'd share with you. If you have a glass tube of hydrogen at 1 atmospheres pressure 1 meter in diameter 1000 light years long but with open ends then in the middle for quite a long time the hydrogen would remain stationary, because the escape pressure of the hydrogen would not reach the middle of the tube for many years. Now increase the pressure of the hydrogen so that its density is high enough to have a noticible gravitational effect. Would this gravitational pull pull the hydrogen from one side to the other? N…

i read an article on bbc where they said scientists froze a photon for about 10-20 microseconds. Doesn't this contradict einstein's theory that photon has no mas because if you are able to stop a photon, then it should have some type of rest mass and if it has rest mass, then it can't possibly achieve the "speed of light". Please correct me if i am wrong. And also, if light can be slowed down to a speed of bullet, then how can you call light a constant and how can we rely on light to tell us distances in space since it can slowed down drastically.Sorry if it's a bit long. Article: http://news.bbc.co.uk/2/hi/science/nature/3308109.stm http://www.livescie…

please explain it. all i kno is that energy and matter[mass] are manifestations of the same thing and C = speed of light but what does it have to do with anything?

Like many people I assume, special relativity, in particular time dilation and the lightbox example, are two hangups on my common sense. I'm under the impression that the lightbox example does not truly 'explain' why time travels slower in the lightbox moving relative to me (and the lightbox stationary relative to me) It's more of a tool that help you understand that time dilation actually exists, not a tool to help you understand WHY, just a 'description' per se. Would that be accurate? Secondly, the "Twin Example" of time dilation, something I don't particularly understand, and boggles my head quite a bit to be honest, is that we all know what rela…

Why does time slow down as you approach C [speed of light]? i kinda get the time slowing at a place of gravity [due to the curvature of spacetime right?] my knowledge might sound naive. EDIT: SORRY!!! didnt kno there was already a post on this!

So far it seems no one on this website really know or understands if Einstein's theories on time dilation are actually true. Ninety years later we are still debating and arguing these concepts today. After reading Einstein and his theories from the early 1900's....I have three really important questions I'd like answered to see who really knows what. 1) Can gravity affect the speed of light? If no, why? Have experiments ACTUALLY been done to prove this? If you shine a light beam down to the gorund and measure it's velocity will it be the same as when the same beam is shone upwards away from gravity? Remeber, gravity can bend light....so why can it not acceler…

Suppose that you had a photon with a wavelength equivalent to the Schwarzchild radius of a mass of equivalent energy. Then [math]\lambda = \frac{2Gm}{c^2} = \frac{2GE}{c^4} = \frac{2Gfh}{c^4} = \frac{1}{\lambda}\frac{2Gh}{c^3} = \sqrt{\frac{2Gh}{c^3}} = 5.72891594 X 10^{-35} meters[/math] [math]f = \frac{c}{\lambda} = \sqrt{\frac{c^5}{2Gh}} = 5.23297009 X 10^{42} Hertz[/math] [math]E = fh = \sqrt{\frac{hc^5}{2G}} = 3.46740157 X 10^9 Joules[/math] Damn! But for the [math]\sqrt{2}[/math], those are Plank units! That can't be a coincidence! This originally from the Schwarzchild radius thread, but I decided to move it to a new thread because it seems important.…

Please forgive my choosing such a provocative title for this thread. I specifically shortened the question I am trying to answer to this phrase because I believed that it would be the most thought-provoking. The question I am really trying to ask is (and I realize that all answers to this question will be speculation, I'm not looking for the 'right' answer, just people's opinions on the answer, backed as much as possible by expertise in theoretical and applied physics): if Einstein had never been able to come up with the general theory of relativity, and no subsequent scientist had been able to, and there were still to this day no satisfactory theories to explain so…

My question is, can Time Dilation affect things like automobiles? even if only moving at speeds of say, 65mph? (even if its only effected by a few seconds difference?) thanks

When defining General Relativity, Einstein explicitly included the possibility, in principle, of travel in the time dimension. His words were “So there is nothing for it but to regard all imaginable systems of co-ordinates, on principle, as equally suitable for the description of nature”. Now, I know that nowadays, the scientific interpretation of “time travel” is restricted to different periods of time passing in different frames of reference. But is there an intrinsic reason for interpreting time travel in that way? If not, it would seem purely arbitrary.

so like my dad was trying to teach me relativity like a month ago and i like heard and rember wut he was saying... but my mind just cant put it all together to make a picture..... so yesterday like i love scienve btw so i think about it alot so yesterday i was getting dressed.. and like im in boarding school right now so like there is showers.. and like little stalls for each one... and i got out and was getting dressed and i was looking at myself in the mirror and someone walked in. and i was like they will see me so i put my towel around me.. but then like ok like the shower is like this... like you have AAAAAAAAAAAAAAAAAA I B …

Just a quicky... something that`s always bugged me with Time dilation idea, is that it`s always said that it`s due to Acceleration. so I`m wondering if you are traveling VERY fast but at a constant velocity, does the time dilation effect Stop? in other words using the Twin in a spaceship and one on Earth example, does the guy in the ship have to be Constantly going Faster for 10 years or can he cruise for 9 years of it at a very fast speed? OR... is all the "work" done as he`s accelerating to that speed so he may as well stop and head back at that point as the effect will be the same? If I`m doing 90% light speed and staying at that speed (not acce…

Hi all. The following was initially posted as a response in this thread, but I believe that it may be more appropriate in this forum since it deals with some of the mathematical underpinnings of relativity. So I would like to discuss this topic here instead of in the other thread. Thanks! I am a 'layman', once trained to some degree in math (I have a B.S. in Math/Computer Science from CMU), but having long since forgotten most of it. I have been reading a bit recently about 'intrinsic geometry', and am especially interested in it because it is required by general relativity. And I have some problems with the concept of 'intrinsic geometry' that I hope someone can…

Is universe really vaccum or any portion of it?

I was bored and decided to do some calculations with the schwarzschild radius. I made up a black hole with a arbitrary and ridiculous solar mass of 100 trillion and i ended up with the weirdest numbers from a size of 15 to 185,000 up to 1.9x10 to the power of 39 parsecs, lol. Can anyone simplify the schwarzschild radius for my feeble brain or do the calculations for me, i'm now at the point of just wanting to know the answer. Thanks

Why the speed of light is constant i.e. c = 3*10^8 m/s can it be slower or higher than this.

Could someone plz help me answer this, albert einstein said that if you went faster than the speed of light you would go forword in time because the faster you go the slower you age, so if you were in the space shuttle moving at about 12000 mph (nowhere near the speed of light) would you still age a little slower at all?

why should covariant derivative of metric tensor have to be 0? thanks,

According to special relativity it would appear that a space twin’s time and ageing could pass slower than his earth brother while they both shared the same present (now). How could this be?

Hello! I've got a question for you guys. A friend of mine told me this: If someone is travelling in a transparent train and drops a coin (standing on his feet, whatever this has to do with anything), for him, the coin would go straight down, but for someone standing outside the train as it goes by, the coin wouldn't fall only straight down, but also in the trains moving direction making the coins movement look diagonal. I think this is wrong as the coin still relates to the guy dropping it, and therefore it will look like the coin is going down in a straight line or else it would land some feet in front of the dude inside the train, which makes no sense at all. We…

Questions concerning Relativity 1- As the present moves on becoming the past does anything remain of it other than memory. 2- Is the future anything other than anticipations? 3- A space traveler, moving relative to earth at speed approaching the speed of light, would have his time pass slower than that on earth. Would not that put the space traveler in the earth past, and the earth in his future? How could they ever meet? Would not the traveler return to earth in its past? 4- The theory of relativity is premised on the speed of light being a constant. A factor in the speed of light is time – miles per second-. If the duration of a second is slower for the space tr…

Hi my name is Chris and I’m a noob! Well I’m a noob here but I’m a Forum Moderator (CJ) on the Forum at Richard Dawkins Net. We often get fundy nut jobs visiting our site and we have a particularly irritating version currently bugging the other members. So I have come here to ask for some help. The question I would like answered is where on the web should I direct this person to that would show him that c has not changed since the big bang? This person is fairly obviously trying the old “light has changed speed since the universe formed” argument to expound a theory that God did it! It’s quite a common tactic of these people to ask ridiculous questions and th…

So simultaneity breaks down as we move to relativistic speeds. For example, if we have frame S' moving relative to S with velocity v (positive x-direction), two events separated by SPACE that are simultaneous in frame S' will not be simultaneous in S. Using Lorentz transformations, we can find that if we put an observer in S at x = 0 and t = 0, then time is S' will be different for that observer everywhere except for at x' = 0, where t' = t = 0. Everywhere with x' < 0 will be "ahead" in time of the point in S (0,0), and every point with x' > 0 would be "behind". If a ship with proper length in S' suddenly disappears in that frame (a single event), in S it would be …