Relativity

This may require a split, but I have two questions that came up when reading this thread: Are gravitational waves affected by gravitational lensing, I found some random (not very sciency) websites talking about how gravitational waves will affect light (by changing the amounts of gravitational lensing). However I was wondering, will these waves also change 'apparent' direction (light goes in a straight path but it is space-time that is curved, which we see as 'apparent' curved paths, right?)? @Markus Hanke Could you attempt to explain how wave-tails emerge from non-linear interactions (at 1.5 post newtonian?). I looked up some articles about it, but realise thi…

Two assumptions followed by a question 1) Red shift of distant galaxies is determined by measuring the shift in absorption lines in a spectrum of light, however, it is not just the lines that shift but the entire spectrum. 2) Higher frequency light has more energy than lower frequency light. Q. If light is emitted with more energy than when it is received where does that energy go?

u do know space is a ball f it wasent it would be pretty wierd in logical thinking

`evr time we trye to solve faster then light speed traveling why not simply try to travel from world to another world like in one weeek not actualy traveling faster then light speed

Does GR have anything to say about particle physics? When two particles collide is it just a case of going through the debris and looking for new objects or are there simple collisions where it is possible to predict when the initial conditions are known? I am reading through Einstein's Popular Exposition and have come across this quote "The only statements having regard to these points which can claim a physical existence are in reality the statements about their encounters. In our mathematical treatment, such an encounter is expressed in the fact that the two lines which represent the motions of the points in question have a parti…

Why we calculate total mass of a subject?

Apparently spacetime was established first (At T+10^-43 seconds if I have that right) and em radiation came next. I am wondering have any simulations or discussions been done as to the evolution of spacetime (ie gravity?) during this epoch ,as it it probably referred to. Apologies if this question makes little sense but I have just come on upon this topic and would not know how to go about researching it or if there would be any point in doing so.

I have just come across this terminology and wonder how it works (also eager to "blood" my use of the term ) So,if we have a massive body far removed from other such bodies,I understand that it will curve the surrounding spacetime(or create a gravitational field) So my question is "Does this gravitational mass dissipate as a result of having caused this effect"? And ,perhaps relatedly does the Gravitational field created by this massive body expand at the speed of c from the massive body in a similar way to how an em wave does (as an expanding sphere)? If it does ,does it carry away the mass of the body so that it dissipates eventually?

In this article of Wikipedia, about spacetime interval, from which I post some extract here below, it is said (in bold the part concerning my question): "After Einstein derived special relativity formally from the (at first sight counter-intuitive) assumption that the speed of light is the same to all observers, Hermann Minkowski built on mathematical approaches (...) (...)In the Minkowski space, one needs four real numbers (three space coordinates and one time coordinate) (...)The distance between two different events is called the spacetime interval. A path through the four-dimensional spacetime, usually called Minkowski space, is called a world line. Since it spe…

"The Lorentz transformations, up to a nonnegative free parameter, can be derived without first postulating the universal lightspeed. " https://en.m.wikipedia.org/wiki/Special_relativity_(alternative_formulations) When I read through this link it is not clear to me how this is shown. Clearly c is the central feature of the Lorentz Transformations ; so is the above quote saying that the invariance of c is not postulated (but that a light speed is) ? If those Lorentz Transformations are derived w/o "first postulating a universal light speed" what does c actually stand for?

Is there a record of who it was who introduced the idea of using separate measurements of time as applied in different frames of reference? I mean ,was this idea worked with before the idea that space and time could be connected mathematically into one concept? (I was trying to work this out from scratch and I was trying to imagine using a non moving clock such as a caesium clock as a time keeper that would apply to both reference frames until I realized that this clock would also be viewed according to reference frames.) Who might have been the first person to have realized that you might have to consider "time" separately for eac…

I have a question related to this subject and statement; Would it be fair to assume that if you are in position xyz and have never experienced a force against you making your momentum 0, could this mean you are actually stationary?

The twin paradox doesn't require an inertial twin. Suppose two twins left Earth at the same time and returned at the same time, each traveling a different but constant speed relative to Earth. Whom does your intuition say traveled a longer distance, the twin who ages more, or less? Don't read the following puzzle if you want to think about it first. Spoiler Two twins leave Earth at the same time and return at the same time, each traveling at a respective constant speed relative to Earth. Each measures the distance she traveled, and the time it takes. They find that one aged twice as much as the other, and they traveled the same distance. What were …

https://www.scienceforums.net/topic/102140-invariance-of-the-speed-of-light/?do=findComment&comment=973768 "the invariance of the EM wave pops out of the Maxwell equations and is axiomatic to the most successful theories of physics" That was imatfaal's post in the above thread some two years ago. Is it correct ? I have been under the impression that Relativity starts with the invariance of c as an axiom based on experimental evidence.. I am not aware that it can be derived from anything I thought what popped out of the Maxwell equations was that this value for the speed of the em wave and the invariant maximum speed,…

I've just discovered the paper Measuring Propagation Speed of Coulomb Fields (PDF) which appears to show that the Coulomb field (& also gravitational fields) travel with infinite speed. The authors also dismiss a critique of their research here (PDF). The theory is way over my head, so I am wondering what the views are of the better educated on S.F as to the merit of the authors' conclusions.

I don't know how it sounds, what is the direction of time? Is it towards the center of the universe, the big bang or opposite? Thanks.

Hi everyone, According to special relativity, time slows down or speeds up according to how fast you are moving relative to something else. As I understand it, the light traveling from something that tells time reaches you slowly when you are traveling near the speed of light and that is why time slows down. I do not understand why the light from time reaching you more slowly means that time has slowed down? The time it takes for a second to pass is called a second, any slower time or faster time is not a second. A second passing slowly means that a second will pass slower than the time we call a second, which would mean that time is not a second because it is …

How?

Has anybody ever figured out how to represent the 4th dimension (in terms of x, y z and t, time,) in a graph? If so, what shape would that graph assume? Certainly not a typical three way graph with a fourth axis just splayed boringly and lazily across it. No, there is a much more innovative way of doing so and I believe I am the only one to have figured it out. But in case I am wrong, it would be one of only two people in history who could have also figured it out: Einstein and Swansont, that excellent intellect. Now, Einstein is deceased, so only swansont remains. I therefore put the question to him.

If you could get into a really fast centrifuge with a device that measures the speed of light, would you see different values for c? If so, would the measurements be both higher and lower than c or just one or the other?

This sounds like coming from ancient Greek philosophy.What are the arguments that support this statement? And I wonder, are there arguments against this? I mean, scientific arguments. Not philosophical ones. For sure arguments can not come out from physics because if so, it would be a counter-argument.

The concept is apparently flawed and the notion of a force acting at a distance seems to have been distrusted well before General Relativity was formulated but it seems conceivable to me* that without the stupendous advances in technology since then that GR might still be a niche subject since Newtonian gravity did the job so well in the main. So what is it about Newtonian gravity that works so well ? Is it a bit like the difference between Special Relativity and Euclidean geometry: is Newtonian Gravity something of a "special case" of General Relativity? As an afterthought and to acknowledge the weakness of my mathematical skills it is not possib…

Is there a physical explanation for this relationship that exists apart from the geometrical explanations? I think Einstein was at first unhappy with this geometrical representation but (I think) he came to accept it. I have heard that c is only coincidentally the same speed as light and ,apparently the nature of spacetime itself is more fundamentally important ,and presumably this nature requires c . I have also heard c described as a "conversion factor" between space and time. So how does c convert space into time? Or is this just a conversion factor in the sense of a mathematical conversion.? Does any spatial…

If I have this right it says that ,whatever the inertial frame any physical experiment gives the same result. What might be the simplest such experiment that one could devise to show this to be the case ? By simplest I mean perhaps involving the smallest amount of energy and ideally involving just a system being measured in one of two possible states. If such an experiment exists I would like to set up a scenario where two observers are in motion wrt each other (so we have a v and a -v) and take measurements of an experiment like the one I have wondered about above . The site of the experiment should be moving at v/2…

Is light speed independent of observer?. Space is full of photons moving in all directions at C speed relative to space time in all space time locations, so, moving observer is only changing space time location.