Relativity

Orbit equation and orbital precession General Relativity explains gravity as Space-Time curvature and orbits of space objects as Space-Time geodesics. This concept is extremely hard to understand and geodesics hard to compute. However, if we can express Space-Time geodesics in analytical form, that is, as orbit equation like Newtonian orbit equation for planets, relativistic gravity will be much simpler and most people can understand. From gravitational and inertial accelerations, I have derived the orbit equation for relativistic gravity, see equation (57), of which I will explain the derivation below. I will refer this equation as the relativistic orbit equati…

The gravitational effect between two objects of mass seems apparent. Even uncomplicated until you start to think about it in detail, but gravity is said to warp Space which I assume can be attributed to mass. The assumption being that the effect is an attribute of mass. Generally there is no clear explanation of what Space is. It's this, it's that, know one really knows, yet it expands and warps. When a photon is affected by gravity we can say that it's velocity gives it just enough mass to be gravitationally effected. If Space is expanding it could be said that it has velocity. My understanding of term accuracy becomes convoluted at times, but Space is sai…

I hear that a body is supposed to travel through space-time at the space-time "speed" of c.** Hope I have heard and reported that correctly. If that is so ,it seems to me it may be a mistake to imagine that body as "voyaging" through space-time in a manner akin to Voyager as it travels out through the the solar system and on into intergalactic space. Would I be right to view this space-time traveling as simply describing the way 2 frames of reference calculate the way the other travels/moves wrt its own frame of reference? Does this idea of a body traveling through spacetime at c suggest (wrongly) that that body is somehow traveling through some kind …

During this grueling time of self quarantining I've been trying to practice a little mental gymnastics everyday and I think I've come up with a small paradox. Well for me anyway. Let's say we have two stars 10 light years apart, star A and B, you have a space ship with 'magical technology" that allows you travel 5 light years in an instant. So you get in your space ship at Star A instantly you are 5 LYs from both stars, I'll call that point C, looking back at star A you see light that is 5 years in star A's past but the light from star B is 5 years in star A's future. The reverse would also be true. Star B's light you see is 5 years in star B's past but still in 5 y…

In the ongoing Gravity and Space thread,Swansont wrote "Photons have no mass, and even if they did, the effect would not be due to velocity, since all photons travel at c. They have energy and momentum, owing to their frequency (or wavelength). The effects on our observations is real, but spacetime is a coordinate system. Like latitude and longitude on a globe, the coordinate system is not flat, it is curved, because that's the proper coordinate system to use to describe the very real effects. When you look at them on a flat map (with a projection that lacks distortion), the lines are not straight. But latitude and longitude are not physical objects."…

Hopefully an extremely simple scenario. Let's have an observer A with another relatively stationary observer B at 100 light seconds distance A emits a pulse of light in the direction of B and that pulse is reflected and captured again by A at a distance of 1000 metres to his or her right (just in his or her vicinity, really) So we have 2 events ; the emission and the recapture of the signal. Am I right to say that the spatial measurement component of the spacetime interval between the 2 events is the 1000 metres and the time component ( ie the ct component) is the 200 light.seconds taken by the signal to make the round trip and retur…

How space-time curvature works ? If space-time exists everywhere including the mass itself, in this case a mass can't curve space-time because all space-time to be curved is inside it.Also if space time exists inside mass then existence or non-existence of mass are the same. If space-time doesn't exists inside mass or mass displace space-time, then when a mass move it will leave a broken space-time.

Usually when I have these long trains of thought, I've gone off the rails early and rest is nonsense. Hopefully this all makes sense, but I at least hope someone can put me back on the rails so I can try again. The precursor to all this was thinking about the twin paradox. I get it - sort of. I believe the math works out, and I believe that there isn't really a paradox. But I feel like I'm watching shadows - I get the general idea, but I can't see the finer details. I don't like the explanation that one twin was in a single inertial frame and the other went through multiple frames. Why would that be a given? Why can't it be the other twin that stayed in …

I always thought that a system was in acceleration because it was expending energy and that its acceleration could be maintained only so long as the energy lasted. The longer the acceleration was maintained the more the system dissipated and eventually it would vanish. On the other hand a system that was in motion wrt another system could maintain that state for ever.

Apparently Feynman had his own method https://books.google.ie/books?id=G0paDwAAQBAJ&pg=PA87&lpg=PA87&dq="Einstein+himself,+of+course,+arrived+at+the+same+Lagrangian**+but+without+the+help+of+a+developed+field+theory,+and+I+must+admit+that+I+have+no+idea+of+how+he+ever+guessed+at+the+final+result.+We+have+had+troubles+enough+in+arriving+at+the+theory+--+but+I+feel+as+though+he+had+done+it+while+swimming+underwater,+blindfolded,+and+with+his+hands+tied+behind+his+back!&source=bl&ots=IGoZy4MI0z&sig=ACfU3U1pAweHTDVX73wpqtGr5ucyNNda5w&hl=en&sa=X&ved=2ahUKEwicjrzO0JXsAhUnSBUIHTTsDJsQ6AEwCHoECAkQAg#v=onepage&q=blindfolded&f…

If we put an observer,E on Earth and another observer ,M on Mars and present both with 2 events , S(1) and S(2) on the Sun , and visible to both is it possible to show that E and M both measure the spacetime interval between S(1) and S(2) exactly the same? So ,if the expression is s^2 = (ct)^2 -r^2 and both E and M measure the same quantity from their respective frames of reference what would be the actual measurements needed to be performed by E and M,? I imagine that both would time the difference in signal capture between S(1) and S(2) and would also somehow measure the physical(spatial) distance between the sites of S(1) and S(2) W…

Light has a constant speed in vacuum of space, and a different constant speed in water, etc. So a light coming from a car standing still is same speed as light from a car that is moving, because also in the atmosphere lightspeed is a constant . But, if an observer is standing still to a lightsource or in motion to a lightsource, speed of light is not the same, while a constant in the atmosphere? Or not?

Let me first stress that I do not have a physical science background. This does not prevent me, however, from being at least competent at logical thinking. I was impressed w/ how willing the people here w/ advanced understanding were to explain things to lay-people. Hence, my question. As I understand it, Einstein explains the puzzle of why things of different mass fall to the ground at the same speed (Galileo's experiment) being because they are following the same space-time curvature created by the planet (let's use Earth, in this example). In that case, would not, "gravity," only be our perception of that curvature, not an actual force? Alternately, if it i…

I offer this thought, in all humility - if Special Relativity theory can generate the above 6 long, complicated pages of debate among highly intelligent people, without their being able to reach any agreement about what it actually means, as appears to be the case - could this be because the theory isn't right? (mod: reference is https://www.scienceforums.net/topic/105185-time-dilation-dependence-on-direction/ )

I think of this question for a long time too, no one give meaningfully answer to this..... I understand in case of light shoot out and than reflect back the time dilation calculation is correct for all direction But consider different path, In view light speed is constant:- A object moving towards us, its time should run faster than us A object moving away us, its time should run slower than us Its a simple calculation but no one can tell what's happening

Suppose one is an observer in Einstein's famous sealed portacabin in empty space and the living space is accelerating at a regular rate in the direction away from the "floor". (The room is a cube of 1x1x1 unit measurement) Now ,under the equivalence principle the scenario is very ,very similar to that of an observer whose room is not under acceleration but rather subject to the gravitational influence of a massive body positioned in the opposite direction to the earlier acceleration. So ,as I see things the acceleration obtaining in the first scenario should be causing a curvature of spacetime in more or less exactly (ie minus tidal effects) the same way as oc…

Some day in the far, far future mankind will travel the stars; this is inevitable, it is in our genes. Believing this I have been contemplating how we get to where we want to go. I do not believe we can carry enough fuel to propel us, nor do I believe we could find the fuel we need along the way. Having said that the only choice we have is to use another source of energy that we have not considered before. That source of energy gravity. Gravity has an almost limitless power; it holds planets in orbit around our sun and solar systems together. I believe we need to find a way to use the pulling force of gravity to pull us in the direction we want to go. We lock on…

Time.pdf

Suppose we want the measure the speed of light for light emanating from the Sun. How do we do that directly? Suppose we have an observer who has accelerated to the mid point between the Earth and the Sun (at c/2 ,as an example) How does that observer directly measure the speed of the light it detects at that moment? If the observer chooses 2 points separated by 1 metre and records the time of detection at each point this should allow him or her to evaluate the speed ,but if the light is first detected at the first point then is not the photon absorbed by that detector and retransmitted to the second detector? So if the observer evaluates t…

I have some questions, and it involves some speculation, but it is somewhat grounded within the currently accepted theory of relativity so I hope what I am proposing is not too speculative. Velocity is defined as displacement divided by time elapsed, and we can calculate the average velocity for an entire trip or the instantaneous velocity at a moment in time. The picture below illustrates this with the scalar portion: Now let's do a thought experiment. Imagine that we are here on Earth, and John takes off in a space ship to head to a destination 10 light years away. In John's reference frame he records that it takes 11.11... years to complete the trip implying…

Hello everyone, I'm a normal guy with an interest in science but no real knowledge of physics (think Bob Lazar) and I'm looking for people who are smarter than I am to answer questions I have about the universe and make me feel all warm inside. First off I would like to say I'm not a flat earther by any stretch, but one of the most common critiques of flat earth theory is that photos from high altitude clearly show a curvature of the Earth. According to general relativity however, wouldn't the Earth from far enough away appear curved even if it were flat, due to gravitational lensing?

Hello everybody. Here is my entry for dumbest question of the day, and I assume replies will include most of the Greek alphabet and squiggly lines that I won't understand but here goes anyway... Q: Do particles experience gravitational time dilation? If I've got this right, gravitational time dilation occurs when two synchronised "clocks" are seperated and exposed to different levels of gravitational force resulting with thier times being no longer synchronised. And if I've also got this right, particles etc can occupy two places at once - as in the double slit experiment where a single photon passes through both slits at once. So... if there is …

I am trying to figure out ballistic trajectories over cosmological distances. All the literature seems to speak only of light, and shows worldlines only of comoving objects, not objects with motion relative to the comoving frame. So suppose some early galaxy exists 1.7 billion years after the big bang, 12 billion years ago. Some star emits light and neutrinos at that event. The light gets here today, so the galaxy at the time was something on the order of 4.7 GLY away (proper distance measured along line of constant cosmic time) from here (the place where our solar system will eventually be). Due to expansion, the star is increasing its proper distance from us at …

Hello, i just want to ask a quick question: could cause and effect be broken, if time stopped? Question is, even if it did... could anything happen due to time stopped? And by that i don't mean classical event in time, by that i mean anything physical, or quantum. Perhaps some interaction of sorts, i don't know... Because for example: some theories say, that time is emergent. Thanks for answer.

A ten meter ship travels as close to light speed as to have all the universe compressed to 1 m length, in the direction of the movement. As the ship remains stopped for the pilot, its length remains ten meters for him. If the universe is 1 m in length, where is the ship flying?