Relativity

I was thinking about how the expansion of the universe streches light waves so the most distant gallaxies appear red (the longer end of the visible light wavelengths). if a gamma wave (or any short wave) was sent away from a distant gallaxy would it be streched to the point that it turns into visible light? and so are we actually seeing a shorter wavelengh waves when we see these red distant gallaxies ... and to continue the radio waves that we recive from further back in our universes time. I was also thinking that without the streching of space would these waves even have a wave effect? perhaps the stretching of space makes the wave effect and without it stretching …

The Einstein page on facebook has been opened,It's a wonderful platform for people who are interested in theoretical physics and relativity to communicate each other. And this page has much content about relativity in many style such as: video,essay,etc. This page has opened not a long time, it needs many relativity enthusiast to construct. Then, I put the link below: http://www.facebook.com/pages/Einstein/160562550668165 Welcome visit My goal is simplest ,to collect all the relativity enthusiast together to share resource and investigate relativity.

That depends on what one means by "mass", in special relativity. The current fashion, apparently inspired by elementary particle physics, is to equate "mass" ([math]m[/math]) with "rest mass" ([math]m_0[/math]), wich indeed is invariant, essentially by definition. But there is also the very useful concept of "relativistic mass", [math]m = \gamma m_0 [/math]. [math] E=mc^2[/math] is correct (admitting that the zero-rest-mass case must be handled separately) and easily remembered if one interprets [math]m[/math] as relativistic mass. If one works only with rest mass one is stuck with [math]E^2 = m_0^2c^4 +p^2c^2[/math]. This latter equation applies to the zero…

Suppose both twins A and B leave Earth in opposite directions and each travel for one year (rocket time) with gamma = 0.5 (relative to Earth), then return at the same speed. My understanding of relativity is that they'll both return to find the earth aged 4 years while they've each aged 2. They remain the same age. But I can't figure this out in terms of what they'd each observe. Twin A would see Earth time appear to run slow as she retreated from it, and then appear to run fast as she approached. Would she not also see the same thing happening to Twin B? Twin B would appear to age slowly (slower than Earth) on the outbound trip, and then appear to age fast (…

I have a different way of looking at Einstein than most, that makes faster than light travel possible, without bending any rules. At least, I think I do. Special Relativity says that space-time dilates at near light speed velocities, and that the time slows down for the traveler. As the old story goes, 100 years pass on earth, while only a few years pass for the traveler on the near light speed ship. This is not merely a matter of perception on the part of the either the traveler or the earthbound observer. This is the reality of the space that both parties inhabit. Relativity says that time doesn't just seem to slow down for the traveler, time actually does move slower.…

This is in response to a recent thread on closing speed, which in my opinion was not totally resolved, primarily due to an inadequate definition of 'closing speed' and the improper application of the concept. The original example is shown in fig. 1, with A and B moving at .7c toward M which is at rest relative to E. The question is : What is the closing speed of A and B relative to E? Typically closing speed is the rate of decreasing distance between two objects moving toward each other, but not necessarily in opposite directions. That would be a special 1-dimensional case and since this example is 2-dimensional, we consider all angles. We define 'closing speed' a…

if object A is moving at X and object B is moving in the opposite direction also at X than either object is moving away from the other at 2x right? but why does this break down when the statement of "x=C" is added to the situation? also how does dilation effect the trajectory of an object? if object x and y are moving at point Z and X is moving at C and is 5000 kilometers away from point z. object y is 400 kilometers away from point z and is moving at 5000 KMS object Y's trajectory is on a right angle to x's. how will time dilation effect when one gets there relative to the other and at what speed are the objects moving relative to one another? ps. sorry …

In the Einstein equation, of GR, Gab comes from Ricciab Ricciab comes from Riemannabcd Thus, in contracting Riemann (rank 4) to Ricci (rank 2), the former is 'dumbed down' significantly, to mate up with the Stress-Energy tensor Tab (also rank 2), in the Einstein equation. But, what about all the information that is 'lost', in 'dumbing down' Riemann to Ricci? Does that mean, that the Einstein equation, even with a 'full' specification, of all the mass-energy distributions, does not fully determine all 256 components of Riemann? To wit, mass manipulates the spacetime fabric in a 'clumsy' way, leaving many 'loose ends' indeterminate?* * What about elect…

Magnetic force could be the future for cars, trains and other transportation. There are several ways to make this happen, but to manage this we must look into interesting magnetic behavior. for example; the meissner effect, flux trapping effect and magnetic levitation and suspension. in this experiment we use; Y-Ba-Cu-O , high tempered super conductor. when it gets in contact with liquid nitrogen it gets magnetic "power" and it repels away from a magnet ( meissner effect), but when you press the magnet on top on the object for some seconds and then release, you will see that the magnet will float stably on top of the object (flux trapping effect). Now here is my question;…

This should be a relatively simple question (pun intended): is there a single formula combining the time dilation from both gravity and velocity? Or is there a series of equations to combine them? (And what is it/are they?)

If you are looking at Earth from outer space, you could see Earth spin right? While on Earth we can't feel the spin or the Earth move because time has slowed down for those on Earth. Is the acceleration significant enough for this difference? Also, if time slows down when you move fast, then how are you moving fast if time has slowed down? I remember reading in a book that when driving in a car, time inside the car would be slowed down in respect to the outside, so does it apply to the car itself as well, because if it does, then how does the car move faster and not slower?

If, in EM, the Faraday tensor [math]F^{\mu \nu} \equiv \partial^{\mu} A^{\nu} - \partial^{\nu} A^{\mu}[/math] (Wiki); and if, in GR, the Riemann curvature tensor is [math]R(u,v) \equiv \nabla_u \nabla_v - \nabla_v \nabla_u[/math] (Wiki); then, could one 'visually identify' the EM 4-vector [math]A^{\mu}[/math] as the 'covariant derivative' of 'something else', as [math]A^{\mu} \equiv \partial^{\mu} T[/math], and then view the Faraday tensor, [math]F^{\mu \nu} \equiv \left( \partial^{\mu} \partial^{\nu} - \partial^{\nu} \partial^{\mu} \right) T[/math], as a kind of 'curvature' tensor ?

Hi all, I'm about to start learning general rel. I learn best when I have someone to bounce ideas off of, or help explain things to. Someone who is struggling would be great as I find that gives me a lot more motivation to get ahead of the material (although if you're already in a class it may take me a month or so to catch up). Is anyone else currently learning, about to learn, or interested in learning GR? I don't mind helping someone catch up a little bit if they lack some of the pre-req knowledge that I have. Reviewing some topics would help me too.Although, I don't think I'd have enough time to help if you aren't fairly comfortable with vector calculus, speci…

Would the exchange of information at a speed faster than c be equivalent to sending information into the past?

In the Minkowski diagram article in wikipedia, under the paragraph Time dilation, here below the following graph: Quoted from wiki: and the beginning of the explanation: Emphasis mine. My question is the following: Can A observe B? I think not, because light travels at C, which is a diagonal not represented on this graph. IMHO what A is observing is the point B2 in the following graph: Point B is simultanate but it is not observable.

Ronald Mallett, PhD is a renowned physicists known for his proponents on the idea of time travel. Mallett uses his background in physics and mathematics to support his idea to build a time machine, using Einstein's Theory of Relativity as a basis. Do you think this is even possible? Right now, Mallett is testing and measuring the speeds of neutrons in light beams in attempts to create a valid and working time machine within the next ten years... Ron Mallett

There have been some questions surrounding special relativity, particularly "time dilation" that might benefit from a global and somewhat abstract perspective on spacetime. This is a bit long, and I thought might therefore be appropriate in a new thread. Yes, keeping various reference frames straight can be confusing, and generates tons of confusion plus the odd "paradox". But there is a way around that mess, and you can thank Minkowski for it. After Einstein built on the work of Lorentz and Poincare to produce special relativity, Minkowski re-cast special relativity in terms of the geometry of a 4-dimensional space with a metric of signature +,-,-,- (or equiv…

How does mass and energy warp space and time?

If mass is energy moving at twice the speed of light, Wouldn't each and every atom constantly radiate and/or exist in it's own time dialation wave and/or bubble?

Hi, im wondering what the connection is in the dimensions between Einsteins special and general relativity theories.. Why did he use the dimensions he did.. Is it that the 4th dimension of special relativity accounted for the warping in general relativity..?

Someone is trying to tell me that when I use c in E=mc^2 that I am using time because c is light going 186,000 miles per second. However, I said its just a value equivalent to 186,000^2, and there isn't even a such speed as 300,000,000miles/s, so could someone clear this up? Does time have to pass in order for the relationship of E=mc^2 to be true? Do you need to travel at the speed of light or whatever using time in that would be?

The topic description pretty well spells it out. Light travels at 186282 miles per second, a velocity at which time and space fully dilate, and where an infinite amount of energy would be required to for matter to travel at the same speed. OK, fine. So why light speed, in particular? And please don't answer "because if it traveled any faster it would go back in time", or "because that is as fast as it could go in normal space". I want to know why the two are dependent upon each other. A better way of putting it might be "What physical rule in our universe makes it impossible for light speed to be some lesser velocity, and if it was would that necessarily change the …

According to J.A.Wheeler's A Journey into Gravitation & Spacetime, spacetime, inside matter, is 'contractile', seemingly seeking to 'curl up into a ball'. Must that not imply, that something, presumably the matter itself, is 'pushing back', and seeking to 'straighten out', both itself, and spacetime ??

Imagine two masses, initially contacting, and suddenly jettisoned apart. As they travel apart, and then fall back together, they sweep out a certain 'area', in the spacetime x,t plane, forming a shape something like an ellipse. Is there a simple relation, between the area of that 'ellipse' swept out, in spacetime, and the initial total system energy? I started working through the equations, from Newton's laws in the reduced mass frame, and, whilst possible, nothing seems simple. Ultimately, at finite total energy (zero), the system starts at escape speed, so sweeping out an infinte spacetime area. So, plotting 'area swept out', vs. starting system energy, one begins …

If Earth is spinning really fast, the earth is moving through space really fast, the sun is moving through the galaxy really fast and the milky way is moving really fast too, at as far as I know about 1,000,000 M/PH, does this mean that time for us is traveling much faster than it normally would? that being in a space were your true speed is 0 KM/PH, so if you left the galaxy and calculated how to use propulsion systems in the opposite directions of were your traveling to slow yourself down eventually you would be about 1 million km/ph slower than you usually are, hence time would travel a lot slower than usual, so you realize we are actually traveling through time pretty…