Relativity

Why' after change of balance on scales , balance happens again? How space/time works here?

1)Nasa uses gravitation force of planets to propel space craft & also to change direction of space craft. Gravity is just space curvature then it can only change the direction of space craft but to accelerate it. I think, we must require force because kinetic energy is get added into it. 2)This addition of kinetic energy is only done by work done in the direction of motion. 3)Can work done is possible with out any force in the direction of motion? 4) In this situation energy of space craft increases then who looses the energy. Co-ordinate system looses the energy which is in direct contact with space craft or anything other looses the energy.

I was a little unsure whether to post this in the relativity or quantum section, so mods please move it if it fits better in quantum. Also, I'm not pushing the argument below out as "obviously true" - I'm just throwing out the idea for feedback and commentary. I've read about people trying to find magnetic monopoles. But given that the magnetic and electric fields are related to one another relativistically, there will always be a magnetic field (in some inertial frame) if there is an electric field in any inertial frame. Imagine that in my lab frame I set up a uniformly charged rod (long compared to the lab). In my lab frame the charge configuration is stationary…

Physicists: I'm struggling with some issues stemming from jointly considering General Relativity and Einstein's Equivalency Principle. Consider, first, two objects occupying two distinct frames of reference: An apple hanging from a tree on the Earth’s surface, and a geostationary satellite far (but directly) above the apple. Both objects have a clock affixed to them. There is no relative motion between the two: Measure the distance between them at any time, and the distance measurement would not vary. Yet, if the clock aboard the geosynchronous satellite and a clock affixed to the apple try to measure the duration of any arbitrary event in the vicinity of the apple, they …

3 years ago, I read one article which says that black hole can explode http://www.dailygalaxy.com/my_weblog/2013/09/the-milky-ways-supermassive-black-hole-exploded-2-million-years-ago-lighting-up-a-cloud-200000-lys-a.html Can it possible? Is this world come in to existence due to super & super massive black hole explosion.

I have a basic question that I've never actually seen answered in discussions of LIGO and gravitational waves: if these waves are warping space itself (actually spacetime), then all matter occuping that space will be warped to exactly the same degree that space is warped, making such warps in principle undetectable. So if an interferometer like LIGO, with two perpendicular arms, is set up to measure such waves, what is it actually measuring? Any distortion of the arms in the direction of the waves will not be detected because that arm(s) will be distorted to exactly the same degree that space itself is distorted. Help?

My view is that you should provide details of this experiment.

I read on quora that the bullets will hit the ground at the same time. Can anyone elaborate why this is so?

So there was no time and no space and then the Big Bang, the Universe springing from a singularity. Now inside our Universe we have black holes and in black holes there is a singularity . Universes inside universes an infinite amount of Universes , now each and everyone of these Universes is the only Universe in existence which sprung from a singularity.

Hello Friends, Please forgive me for asking such a crazy doubt. Relativity explains gravity as curvature of space-time and all objects under the influence of a mass follows a straight path in 4D space time which can be visualised as curved in 3D perception . Now my doubt is, of gravitation was not a force and just a curvature in space-time , why does a small mass ( at rest with respect to another larger one ) get attracted to each other. Since the mass was at rest, it doesn't have to follow any path in modified space-time , right ?

So, I have heard laws of space doesn't work inside the black hole so, 1) Can one move faster then light in black hole? 2) If it can't then what happens to the gravitational pull of black hole? 3) Follow up for last question if you can't break the speed limit of light in black hole then gravity also can't leave black hole as it also moves at speed of light. That means black hole should not have pull out side of event horizon that means matter should not be able to pulled in to black hole. 4) If it can then how is the physics different there? 5) Also if it can move faster then speed of light then it should be able to break past the escape velocity of black hole. so,…

OK, so I was thinking about black holes for some reason last night and got a question. Say, here on Earth the escape velocity at the surface level s around 11.2 km/s and any object crushing on Earth from outer space, even if initial relative velocity was 0, should end up hitting the surface at least at 11.2 km/s, if there were no air or the object is sufficiently massive so it's not slowed down by atmosphere as much. But if the object has a relative velocity to begin with, it can impact at a higher velocity. Now, by the very definition of the Event Horizon of the black hole, the escape velocity at that region equals to c and, therefore, if you start at 0 velocity…

if gravity expression is due to a warpage of space, what is doing the warping? In space is a sea of virtual particles, I conjecture that the geometric orbits of these annialations are affected by proximate energy/matter, thus extending the annialation process resulting in the observable effect of gravitation. This local change of annialation process expands out in a phononic-like manner at c with the inverse square law with tensor expression into the surrounding sea of VPs, thus inferring then stiff, yet deformable flux being the observable result of what we call space.

One of my books on EM theory brings the theory forth by starting with Coulomb's Law and special relativity and then proceeds to show how those things together require the existence of a magnetic field and so forth. Coulomb's Law and Newton's formula for gravity are both inverse square laws, so it seems an entirely parallel development could be done starting with Newton's formula and special relativity. And yet in sense EM and gravity are very different, with one being a "real" force field in GR terms and the other being an aspect of spacetime geometry. How valid is this, and how far can it be taken? Is it off track from the start because Newton's theory isn't re…

So let us all assume that a mirror is going away from us at speed c/2 and we are stationary. Now a ray of light leaves from me reaches to mirror and reflects back. So from our prospective light will be moving at c/2 w.r.t mirror hence when it its reflected it must be the same c/2, but mirror is already moving at c/2 that will only mean light must be stationary and we will never see our reflection. And if we start increasing the velocity of mirror that will mean light will start moving forward but slowly. I know it doesn't take relativity in consideration but since i was stationary observer I don't think I need to. So please point me out where I'm wrong and where can i get…

Imagine we had two line currents (ignoring the rest of the circuit, return paths and the voltage source) of same direction and rotating in a common x axis with equal angular velocities. Assume that the distance between them is much larger than the wire lengths. If we were sitting on a wire and rotating with it, in the S’ frame they would appear stationary to each other so there is no time delay and they would be exerting the full magnetic force on each other. But in the S frame, they would look rotating and their EM fields arrive at each other with a phase delay, which means each one should be “seeing” the other as slightly backwards in time (and angular position).…

A recent thread touched on the subject, but not in a satisfactory manner and the thread got locked. I think that the twin paradox goes right to the heart of SR, so should have it's own thread. I hope this one won't get hijacked with irrelevant stuff. As someone who has struggled to reconcile the case of travelling twins and it's apparent paradox with the interchangeability of inertial frames in Special Relativity, I want to share my progress with others who might want a clearer picture. I just found two pages on the net that give a brilliantly clear explanation for the outline of the paradox, and the explanation for some of it, and I recommend them to …

Hi. I decided last night to work through the derivation of the Lorentz transform. I've "learned about it" in the past, but I thought it would do me good to pay full and rigorous attention to the math each step of the way. So I started off, and before long had the the transform that relates the coordinates of an event (x, ct) for observer S and (x', ct') for observer M when S sees M moving at constant velocity v. So far so good. I had it written in matrix form, so I inverted it and confirmed that the transform and its inverse gave me the identity. Score one for the home team. Then I looked at the situation where S observes an object moving with constant velocity …

I would like to understand the history of the cosmological constant. In the following article it is state: https://en.wikipedia.org/wiki/Static_universe "Albert Einstein added a positive cosmological constant to his equations of general relativity to counteract the attractive effects of gravity on ordinary matter, which would otherwise cause a spatially finite universe to either collapse or expand forever". However, it is also stated: https://en.wikipedia.org/wiki/Cosmological_constant "Einstein later reputedly referred to his failure to accept the validation of his equations—when they had predicted the expansion of the universe in theory, before it …

I am prompted by something mordred said: space is volume. I have no problem with this but I was wondering, when we see the co-ordinates xyzt, does this mean that time is a part of space or just that it is treated in conjunction with space but time is actually a property of the fields within space, bearing in mind the prior assumption that space is just volume? Hope this makes sense. I didn't know where to put this as it's a general question rather than necessarily to do with Relativity specifically; quantum physics may have a position on it.

Why is the math used to describe relativistic mass different from the math used to describe rest mass? As far as I know, the stress tensors look differently in those two cases? Is it the case that gravity behaves differently for relativistic mass and rest mass? I suspect that it cannot be the case but why are the stress tensors different? I find it absolutely stunning that there might be a discrepancy between how gravity behaves for relativistic and rest mass but that's just not possible right ?

There is a square moving at a constant speed across an inertial frame of reference. Relative to an observer at rest in the inertial frame of reference the square is moving diagonally. The moving square is length contracted in its direction of motion. (A diagonally moving square is diamond in its direction of motion. Contracted, it becomes a rhombus.) And so, from the perspective of the observer, the height of the diagonally moving and length contracted square is the same when it is at rest or when it is in diagonal motion. There is also a rectangle moving at a constant speed across this same inertial frame of reference. Re…

Yes - At any given aria nothing can go faster than a speed of light. However, Based on relativity - objects can go faster than a speed of light. Hence, even if an object is not moving at a speed of light, there is a possibility that with regards to other object, it could go faster than a speed of light. Explanation: Let assume that A represents an object which is not moving in space. B will represent an object which moves away from A at 0.6 the speed of light. C will represent an object which moves away from B at 0.6 the speed of light (at the same vector as AB). Therefore, the relative speed between A and C is 1.2 the speed of light. Do you agree with t…

What happens when relativistic momentum becomes infinite? or what happens when the speed of an object approaches c? One last question, Why is it not possible to travel at and more than speed of light? Feel free to use formulas to support your answers!

Try to explain why nothing can go faster than speed of light without using the term relativistic mass. Can it be done?