Relativity

We are told that spacetime bends and warps in the presence of mass. If we remove this mass does the spacetime straighten out again? If so what causes this.

I m a noob, I wanted to figure out the time dilation for an observer on earth who passed 50,000 years, and the Traveler at light speed(99.9%) passed ONE DAY. I mean we pass 50,000 years on earth and the Traveler spends One day.Problem is I tried many online calculator, but each one is giving me different result with the same inputs.I m confused.I want to know the result. I also want to consider the LENGTH CONTRACTION/DISTANCE DILATION while calculating this.I m not very good at maths. Can somebody figure this out for me. Please make sure ur calculation is right, bcoz each online Time Dilation calculator gives different answer,which is frustrating!!. Considering the a…

in long distances (megaparsec level) does the accelerating expansion of the universe affect on light and it's trajectory?

I really want to understand how Lorentz Transformations come about! I have analyzed the derivation of Lorentz Transformations (LT) in [3] The special and general theory of relativity; Albert Einstein; The first part; About the special theory of relativity; 2006; swedish [7] Modern Physics; Second edition; Randy Harris; Chapter 2; Special Relativity; 2008 I believe that the derivation in these two books is not self-consistent. Why? I explain below and would like help with this. Both in [3] and [7] one uses three special cases to derive LT. You start from two linear equations (I use my own notations to more easily refer to different parts of the derivation): L…

I really want to understand how Lorentz Transformations work! I refer to the picture Fig. 4-01: There we have an inertial reference system, S, that I depict with the axes x, y, x. In the future, we will only process the points on the x-axis, so in the next pictures I will draw only the x-axis. We regard this reference system as stationary, ie the distance between the reference system origin and the point where the event occurs is the same all the time. Then I would like help with defining what the coordinates x, t mean for S.

What does it mean that a source of energy will curve spacetime ? How is the energy measured? Is it relative to a particular frame of reference? Does that mean that 2 different frames of reference will measure the spacetime curvature of an identical region differently? Does "region" have to be understood in spacetime terms?

I want to know about the equations of a motion that has a specific acceleration in all three dimensions simultaneously. which requires vectors that simultaneously are accelerating in all directions.

What notes should I read before taking a book" a short course in general relativity" by Nightingale. Thanks

If you were the body and accelerating yourself, do you know how this would feel or what you would measure? For example, if you're on a rocket accelerating away from Earth at ever-increasing speeds. I think that understanding that would help understand the issue. (Hint: a simple rocket model implies constant proper acceleration, and is probably an easier answer. If instead you suppose constant acceleration relative to Earth you'd measure different things. You could also imagine accelerating in short rocket burns and then describe what you measure in between; what differences do you notice between subsequent burns?) Another question that might help understa…

In my travels I have heard it said that "relativistic mass" is an outdated concept. It always had me wondering about its validity but I was never really sure how to conduct an argument against what I saw as wrong. Why did I see it as wrong? Probably two reasons that I know of...[1] As a body gains speed, the harder it gets to get it to continue to accelerate, illustrated by the fact that the energy would need to be infinite to push it beyond "c"...the second being that light/photons have zero rest mass, but yet is able to exert a force due to its momentum. Am I wrong? or do the points I made mean that relativistic mass is certainly a concept still useful and va…

Does this mean that there is a common moment of Now (the present) i.e time is ticking everywhere where space is.

I'm an armchair scientist. I have many interesting ideas on science. I wrote a book on one, well not really a book as much as a pamphlet, but it does contain interesting ideas. Would you like a copy?

In the derivation of LT in [7], three special cases are used to determine the constants A, B, C, D. SC1: SC1: LEx': x' = Ax + Bt LEt': t' = Cx + Dt SC1: x' = 0, x = vt → B = -Av SC2: SC2: LEx': x' = Ax + Bt LEt': t' = Cx + Dt SC2: x' = -vt', x = 0 → B = -Dv But I have not seen a figure describing SC3. Can anyone help me with such a figure? SC3: LEx': x' = Ax + Bt LEt': t' = Cx + Dt SC3: x' = ct', x = ct Thank you!

Just curious - as a non-science major - the Nicholas Roeg film has a scene in which Marilyn Monroe explains special relativity to Einstein. But I have a feeling the explanation is wrong - please see script below - wouldn't, on this basis, each observer conclude that the other observer had the same time reference - the only issue being the amount of time light takes to reach each one, which can be accounted for by each? I've had to attach it as the script extract is too long otherwise. Thanks for your views! Script: Insignificance.docx

Bend space doesn’t exist, if it does “like a tunnel” why objects passing thru it don’t follow the same curvature of the tunnel but instead curvature of the law of gravity

Suppose we convert the Earth (or a similar sphere) into a series of tunnels connecting the surface with the centre (billions of straight tunnels) and build a cavity in the central region to accommodate billions of infalling identical samples of ,say lead ... What would happen at the centre as all these sample met and filled the cavity at the same time? (having been released all at the same time) Can this be modelled as a scenario (a computer or theoretical simulation)? Would the lead rebound to the surface repeatedly until it eventually settled in the cavity? Would a black hole form? Would any mass be lost out of a "plug" in…

Those events scream they have nothing to do with spacetime, so why are you refusing to let them go? I say let them be their own thing, they don't work with time or gravity anyways. I know what you are going to say: Your answer is built on a man-made excuse/mistake to include QM in spacetime. Yes, it has math going for it, but it isn't sharing what the reality is. Spacetime is under no obligation to include the scale of QM. QM existed before the big bang: https://phys.org/news/2019-05-stabilizing-no-boundary-universe-quantum.html

Each cause spacial curvature to different degrees, and apparently the curvatures do not add together. The hammer and the feather follow the moons curved space at the same rate of acceleration. It seems that the only effect individual curvature has is in how much energy must be used on the hammer or feather to change it's direction?

Can it be said that space interacts with Mass/energy?

I mean simultaneity is a time period, not a time.

With length contraction is there a change in density? If there is would that in part/maybe in whole account for the increase in mass. Then it leads to other questions like if we slow something down that is moving really fast like a particle does it get bigger?, or maybe change identities completely, because it changes energy levels,and can we expect a particle to be contracted and more dense on the side of the direction it is moving. Do photons increase in volume when passing through water? If it doesn't, any thoughts on why?

Hello, I learned that a stationary observer is stationary relative to the expansion of the universe. This observer doesn't travel through space, but it travels at light speed through time. Why do physicists not use this reference frame to talk about absolute speed through space. If physicists talk about a stationary object (no motion through space, only moving with the expansion of the universe), they imply that there is absolute speed through space possible. (instead of relative motion). (ps: to moderation: I didn't ask this question before in another thread).

Time is relative. (Einstein) Yet scientists say that the universe is 13.8 billion years old. But dependent on different clocks of different observers with a different speed or in a different gravitational field, the duration of time can differ. Isn't that a contradiction?

Các thí nghiệm của Michelson-Morley và Sagnac đã chứng minh rằng có gió Aether. Thí nghiệm của Michelson-Morley không mang lại kết quả như mong đợi. Đó là bởi vì chúng ta hiểu nhầm Aether. Tôi giới thiệu cho bạn một suy nghĩ mới và sau đó có thể hiểu mọi thứ dễ dàng và đúng đắn với thực tế .. qua đó các thí nghiệm của Fizeau có thể được giải thích nhưng không phải là một công thức vô cảm như Fresnel.

Einstein's fundamental metric quadratic yields 16 equations. He discarded 4 as they are duplicates and he ends up using 10 after discarding 2 more. What were the 2 of the 12 equations he discarded and why did he discard them?