Relativity

Scenario: man in spaceship leaves earth at near light-speed and returns a year later. 1. Would he need to travel constantly away from earth or could he just orbit for the relative time difference to occur? 2. What would would we hear/see from earth if we were in radio/video contact with him? Thank you for any replies.

I have a question about Newton's equation for gravity. What would happen if you threw a ball with an initial velocity very close to the speed of light towards a black hole. We would assume that you would be very far from the black hole. Would the ball accelerate pass the speed of light before it reaches the event horizon? I did some calculation and found that the ball will indeed surpass the speed of light far before reaching the event horizon. Does this mean that F=GMm/r^2 is wrong because it breaks special relativity? I did found a solution on my own but I'm not even sure if it's right. I put the calculations and my solution to the problem on a word document, so if anyo…

40yrs ago my physics teacher was insistant that you couldn't travel faster than light and drew a car on the blackboard doing a right turn, a right, a right turn then crashing into itself saying you cant be in two places at the same time and whilst i agree with that and i know others wouldn't the fact remains you wouldnt be crashing into yourself you'd be crashing into the light from yourself two totally seperate things, was that a poor analogy or have i got it wrong? also is it right to say that if i syncronised 3 clocks seperated 2 by a light year and kept the third with me that no matter where i went all 3 would tell exactly the same time? obviously if i stood by o…

is it possible that anything that proves time travel is in fact proving something else? the events from the past no longer exist the information from those events do but the events thenselves dont, the events/information to create the events of the future exist now but future events dont. is there any room in phyisics to interact with something hat does not exist? if you slow down events close to yourself whilst things around you carry on at a faster pace and then you return to your wider suroundings where more events have occured you havent travelled in time, you didnt go anywhere, the people around you didnt lose sight or contact with you, you simply did less than …

Is there any relationship between time travel and parallel universe according to current understandings or theories? Thanks.

As its not only time, its always spacetime according to Einstein. So, if we want to travel time, we always have to travel actually space time, which means only staying on earth we can not travel time (not regular time, past or distant future in short time). We literally have to move to different location in space (with light speed), Then how its possible with light speed going to a different location in space we will find another earth (whatever the time is)?? Or is it possible to travel time/spacetime only in distant or different location in space??? Thanks in advance.

Hello everyone, Excuse me for my thorough lack of understanding of this topic but I was reading some of Einstein's notes on relativity & the shape of the universe and this made me thinking. I have always "understood" the idea that gravity warps space time through the trampoline analogy. The problem in my thinking is that if gravity curves space time, shouldn't the entire universe be a ball/spherical? As it contains matter everywhere, which would warp it inwards to itself (or maybe it becomes a doughnut shape?). I know that from experiments we have verified the cosmological constant (?) to be 1 or as close to 1 as we can verify experimentally, thus meaning that th…

My interest in asking the above question was raised after reading the following article from "Quanta Mag" OK as the heading asks, will we ever have a viable alternative to GR? https://www.wired.com/story/troubled-times-for-alternatives-to-einsteins-theory-of-gravity/ [05/06/2018] TROUBLED TIMES FOR ALTERNATIVES TO EINSTEIN’S THEORY OF GRAVITY: Miguel Zumalacárregui knows what it feels like when theories die. In September 2017, he was at the Institute for Theoretical Physics in Saclay, near Paris, to speak at a meeting about dark energy and modified gravity. The official news had not yet broken about an epochal astronomical measurement—the detection, b…

Hi all, Apologies if this is not the right level of question - I have no education in cosmology whatsoever, but I have now been to several events at which the light clock experiment (and therefore time dilation) is explained. I understand it all, in principle, but can not get my head around exactly why that means that time is actually going slower for the faster moving clock/people. I've now read stuff online and watched Youtube videos and I know I'm missing some key part of understanding. What I understand is that clock A (on earth) bounces a beam of light back and forth between two stationary (relative to the earth and our observer) mirrors. Each one is a tick…

Special Relativity is formulated from an assumption: 2. Second Postulate (Invariance of c) There exists an absolute constant \(0<c<\infty\) with the following property. If A, B are two events which have coordinates \((x_{1},x_{2},x_{3},t)\) and \((y_{1},y_{2},y_{3},s)\) in one inertial frame \(F\), and have coordinates \((x'_{1},x'_{2},x'_{3},t')\) and \((y'_{1},y'_{2},y'_{3},s')\) in another inertial frame \(F'\), then \( \sqrt { (x_{1}-y_{1})^{2}+(x_{2}-y_{2})^{2}+(x_{3}-y_{3})^{2} )}=c(s-t) \) if and only if \( \sqrt {(x'_{1}-y'_{1})^{2}+(x'_{2}-y'_{2})^{2}+(x'_{3}-y'_{3})^{2})}=c(s'-t') \). It appears this postulate makes no limitations on …

How do we know that the speed of light is a universal constant? I struggle to see how the speed of light would be measured any significant distance from earth, so could it be possible that the speed of light might be different in different galaxies or in the vicinity of high gravity objects like black holes?

Especially in this context.... Mass ,energy etc are said to "curve the geometry of spacetime" Now I think I understand that this may be another way of saying that ,viewed from a different frame of reference that "straight lines" (geodesics) appear to follow a curved trajectory. If I am right there, what does this say about the meaning of the word "geometry" ? Is "geometry" a formalized setting out of all the different kinds of relationships between points on a manifold? Would that be an acceptable definition? I also think I have learned that all "geometry" is Euclidean at a sufficiently local level but when the observer tries to encompas…

I have always considered gravity to be a force. Then the end all of all conversation came along. Okay,I kind of gave it that name because it seems to me that when I see it used it is generally ment to stump, or end a disputed opinion. “The statement” : “Gravity is not a force. It is a space/time curvature.” The first time I met “the statement” I was like; “What?” ... So, it served it’s purpose. I tried to imbrace it. Think in new ways. I never seemed to quite get it. For this reason, or that reason. Depending on the opinion, and how rhetorically gifted the person whom I was in conversation with was... But then, the other day while reading anothe…

Does anyone else have any thought in Einstein’s theory of relativity being a possibility of a mere joke to have others think? I can already think of a scientific experiment to disprove how you can fabricate his idea of The speed of light in a vacuum is the same for all observers, regardless of their relative motion or of the motion of the light source. if one was to use a tank filled with different types of liquids for the viscosity to find a substance equal to the particles in space, a prism for direction and a flashlight. My thought is to warp the idea by the angles alone. Take for example the objects in space. Would the light travel through them? Or would it…

Hi I'm writing in the hope that someone can help me to understand my confusion on a question. It's about the upper limit of entropy S or information I, which can be contained in a limited region of space that has a finite amount of energy. I looked at the formula and thought that if my energy is constant (say it is a one solar mass) and the radius, for example, starts approaching the zero, entropy it will be quite small. At some point, when the radius becomes equal to the Schwarzschild Radius, the object will become a black hole which it has a certain entropy. But In General Theory of Relativity mass will continue to shrink into a smaller and smaller region, which means s…

I was watching a video about uncertainty. The man said, "Wide in time, narrow in frequency." Then, the inverse of the statement... So if a moving clock is observed as ticking slower, as the observer where would I fit in that thought? I'm thinking the inverse since the clock I am observing is moving, I keep thinking of the seconds widening as the clock moves faster. Then I keep thinking maybe I've got it backwards? I seem to be trying to apply the explanation in the video to relativity, but I keep getting confused when I start trying to figure out what my position as the observer would be. Here is the video maybe what I am trying rationalize makes sense? Ma…

First, English is not my first language so, sorry if I use any wrong grammars or words. I am not sure that my question belong here or not because it is my little wonder. I am not 'Physics' people. I am only interest in some basic knowledges from theory. I have read books about our universe like 'A Brief History Of Time' by Hawking and a few others of its kind. ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- They say 'Space and time are relativity' 'Nothing can travel faster than ligh…

Hey guys, this may sound stupid but I am quite new to theoretical physics and I want to learn more. So, my question is, do objects move faster when you move towards them, for example at the speed of light? If you, for instance, move towards Andromeda at the speed of light, which is around 2.5 million light years away from us, for 100 years(just theoretically), Andromeda will be 2 499 900 light years away from us. That means the light from Andromeda will reach you faster than at the Earth. Does not that mean that while moving it should be rotating faster from your perspective, for example?

I am writing about relativity both special and general relativity. I am curious about time travel idea. Do you have any idea to share about all facts and cons of time travel. commercial url removed per rule 2.7

Herman Minkowski was one of Einsteins professors at the university where he graduated from. After Einstein developed his special theory of relativity, Herman Minkowski proposed a new idea to him in order to describe spacetime, since the time dilation equation received a lot of attention in his paper On the Electrodynamics of Moving Bodies. He proposed a rather simple idea about how to create a framework of a coordinate plane which could obey the rules of relativity, and it would have to replace a normal coordinate plane in which time dilation wouldn't show up. He started out by saying that all distances in the coordinate plane should be calculated by multiplying t…

I will explain the doubt with the following example. I go to the cinema and the film tells the experiences of some scientists. In one scene, it shows a laboratory capable of operating in a vacuum, where there is no gravity or other fields. There are only the fields that scientists can create when they do an experiment. The shape of the laboratory resembles a large tube with a rectangular section. The work rooms are on one of the walls of the tube. The inside of the big tube is hollow. The media available in the laboratory does not detect surrounding objects. Within the scope of those media, the laboratory is alone in an empty space. Inside, near one en…

does anyone know of a model for how much energy it would take (theoretically) to bend space-time and anything else on the subject? - Sci-Man

How to define gravitational slowing of clock in center of mass?

I have been reading about this and frankly it seems to me that experimentation and even crude developments are being made in this field. So is there evidence that entangled particles at a distance are entangled instantly, which would be faster then light travel? Because this would mean communication between the farthest satellite Voyager I think would take the same time as a thought before expression. No one doing these experiments will or can be truly forthcoming because of company rules. Thanks

No I know it can't normally but what if it did and we could decide on the radius of the new body? If the radius was small enough would it cease to have much effect on the movement of the planets (would they lie outside its region of gravitational influence? ) Is there a limit to how small a radius the "new body" could have? Does its radius depend directly on the mass of the bodies that have been incorporated into it in the first place? Does its radius remain the same provided there are no more additions of massive bodies?