Relativity

Let's say hypothetically two people on Earth are born on the same day at the same time down to the second, and one of them becomes an astronaut. He leaves Earth and launches into space. He lives in orbit on the ISS for one revolution of the Earth around the Sun, while his counterpart remains on the surface of the Earth. Upon returning to the Earth, the astronaut is now older than his surface-dwelling counterpart, even though they were born on the same day at the same time and have experienced the same number of revolutions of the Earth around the Sun. In fact, it is not just the astronaut who is older. If we assume that when he launched into space the Universe was 13.8 bi…

Most images about general relativity and curvature of space time are show as the image below, where space-time is portrait as a "fabric". We see a grid that bends where earth is placed. I wonder though, if this fabric should be portrait in 3D as well. In the image below earth is "sitting" over this fabric, but isn't this fabric all around earth? If this is so, then space-time is being bent not only below earth, but all around it (view last image to see what I mean).

Some years ago my brother and I bought identical cars. My brother has not used his, but has kept it in his garage ever since and, if anything, it now looks better than new. I have been rather busier and my car has nearly 150,000 miles on its clock. The saleman for both out cars was called Albert and he promised that the more and faster I drove, the younger my car would look, relative to the one of my brother. So why, oh why does mine look like a train wreck that has already happened ?

The linked paper is an entry into 2022 Gravity Research Foundation's essay contest. I'm looking for criticisms and feedback. Basically, I show that we can predict gravitational effects on light by applying Snell's Law to the graded time dilation field surrounding a massive object; the implication being that all gravitational effects are purely the result of time dilation. https://drive.google.com/file/d/1KsfgRHJvIYfm45NcJCKg6fGalDxp3QMJ/view

Responding today to the thread in Speculations, it struck me I don't know how to treat the stored energy in a static EM field, according to E² = (mc²)² + p²c². Since, unlike the situation with EM radiation, there is no motion involved, I presume the second term does not apply. But does a static field gain rest mass, as its stored energy increases? Seems weird if true. I've a feeling I'm missing something here. Can anyone help?

Just found this. https://thedebrief.org/darpa-funded-researchers-accidentally-create-the-worlds-first-warp-bubble DARPA FUNDED RESEARCHERS ACCIDENTALLY CREATE THE WORLD’S FIRST WARP BUBBLE: Warp drive pioneer and former NASA warp drive specialist Dr. Harold G “Sonny” White has reported the successful manifestation of an actual, real-world “Warp Bubble.” And, according to White, this first of its kind breakthrough by his Limitless Space Institute (LSI) team sets a new starting point for those trying to manufacture a full-sized, warp-capable spacecraft. “To be clear, our finding is not a warp bubble analog, it is a real, albeit humble and tiny, warp bub…

From what I understand about relativity, it seems as though the notion of superposition is unavoidable. Whether it be for particles and worldlines or just particles, my question is quite simple. If two different observers, travelling at different speeds relative to one another, are correct that two particles, at rest relative to one another, have different distances between each other, then how can this not be a superposition?

If the question in the title is yes, then is velocity and speed just the shape that the "strings" make? And if the answer is yes to the second question as well, then what does it physically mean to "be an observer travelling at relativistic speeds"? Finally, how does length contraction come into all of this if these strings are static and unchanging? Please help me

if we see the observable universe. And watch the universe expanding ever faster. Seeing the universe 40 billion light years away. Surely the images are 40 billion light years out of date. As the images we see are how the universe was 40 billion years ago. And say it had stopped getting bigger 20 billion years ago. Surely we will have wait 20 billion years. To see the light reach our telescope. And image 40 billion light years away. Is 40 billion years out of date. Or is it could someone please explain in lamens terms. If I'm wrong. Many thanks Eddie. If they were watching us from 40 billion light years away. Surely they would see. Us as we were 40 billion years ago. I wou…

Einstein uses a lightning strike to establish the idea of simultaneity but fails to consider the distance of the two observers from the lightning strike. My contention is that in order to understand simultaneity and discuss it and refer to the order of events and the appearance of time slowing and quickening and distances foreshortening and such, one needs to float the existence of two nows. One where everything is happening in the entire universe right now at the same time, and one in reference to an observer in a location, moving at the speed of the frame of reference he or she inhabits. It is true that NO other observer is in the same time as you are, becaus…

I was thinking about this as an example for another thread but thought it would only add confusion. Say you have a train with proper length 100 m, traveling so fast that it contracts to 1 m according to the tracks' reference frame. Suppose that in the train's frame, lightning strikes the front and back of the train simultaneously. How far apart are the lightning strikes on the track? Can anyone answer this with just a few seconds thought? I can't, I have to figure out the details and calculations, but if I ask a different question... Spoiler Suppose the train goes through a tunnel and exactly fits inside it, in the train's f…

The year is 2050. Bob goes close to light speed in his ship. He sees a 100 meter train contract to 1 meter. He gets back from his trip in the year 2100. Aliens from another dimension are looking at our block universe from 2050 to 2100. Will they see a 100 meter train or a 1 meter train or something else? This is meant to support the argument that length contraction is an illusion and not actually happening.

Hello all. I would appreciate any help anyone is willing to give me. I think I'm posting this to the right discussion board. I apologize if not. This may be a bit of a silly question but here goes... I was driving in a van with my family when I was young. We're going about 60 miles an hour down the interstate. While we were driving, a fly was flying back and forth through the van. Now, I know the fly was not going 60 miles an hour while flying from the rear of the car to the front of the car. I never understood why the fly was not stuck to the back window. What scientific principals or theories might be involved that could explain how the little fly co…

My understanding is that Doppler redshifted light received at a relatively stationary destination from a receding light source is still deemed to be travelling at the same speed of c as light arriving from a relatively stationary source. Has this been experimentally verified and if so how?

https://www.vice.com/en/article/78kqjq/the-smallest-radio-receiver-ever-is-made-from-imperfections-in-diamonds I was wondering if this kind of an object might be small enough to be accelerated to relativistic speeds and whether (in that unlikely event) it might be possible to monitor any distortion in the signal due the receiver moving wrt to the source at high speeds.

In the latest issue of American Scientist there is an article by Tony Rothman questioning E=mc^2. Are the assertions made in the article valid? Are there comments by other physicists available?

Einstein describes how an accelerating sealed chamber is indistinguishable from a gravitational field to an observer in the chamber. I have learned and read a little about this in the past 5 years or so and also that Einstein described this as his happiest idea. It seems to be possibly the kernel of General Relativity and yet I wonder whether his appreciation was any different or more profound than the appreciation of weightlessness and artificial gravity that became common knowledge as soon as astronauts went into space in the 60s. True ,Einstein realized this without seeing astronauts floating around the spacecraft but what I want to ask is wh…

What type of mathematica is this on the picture. When I start to study relativity, it appears and I don't understand it.

Hi there, I have been reading a book about time (with an equal name, by Paul Davies). In it he explains time dilation and parts of relativity. I have two questions regarding what I have read so far, one for another thread. My current question is regarding the perceived difference in distance when two observers are in relative motion to each other. A star 5 light years away from the earths point of view, might be only 3 light years away for someone traveling at 80% the speed of light towards this star, if I understand the physics right. This alone I can understand, however I cannot seem to then comprehend how this would work for motion between other observers. Even …

Hi everyone and everybody, Following the generalized and repeated question about synchrotron radiation wavelength there scienceforums When the deflection is big, at a star, at some bending magnets... the beam divergence combined with the angular speed defines the pulse duration, with a known formula. But a horizontally ultrarelativistic particle that falls in a lab experiences an extremely small deflection, so the beam divergence obviously doesn't limit the pulse duration. Instead, the distance over which the particle may emit the observable part of the pulse limits the pulse duration. It should have been clear enough after I related many times the d…

Hi everybody! I wanted to surround a particle beam with a sleeve mirror and coat the inner face of the sleeve mirror with a transparent material to make light as fast as the particle and produce a shorter and stronger light pulse, or a weaker pulse. This dielectric can be thin on a support. But it must be very thin. Take full-energy Pb ions, 57ppb below c at the LHC, divergence +-10mm over 30m. A N=1+0.5 coating in a D=3mm must be 0.34nm thin, just 2-3 atomic layers, and accurate to shorten the pulse. So the first difficulty is to avoid unwanted adsorbed layers. This implies noble materials cleaned under vacuum. Here some reflection coefficients at 2.1eV fo…

Hello dear friends! Whether a charged particle radiates when falling in a gravity field has been debated http://www.scienceforums.net/topic/80770-do-electrons-radiate-from-electostatic-acceleration/page-4#entry861035 https://www.scribd.com/doc/100745033/Dewitt-1964 Whatever the prediction by plain Relativity is, a disagreeing observation would be a precious hint towards a more general theory, possibly a unification of gravitation and electromagnetism. Here I propose elements for an experiment to check it. "Elements", because the figures I have right now aren't a complete solution - but this can only improve The radiation, if any, is badly small. A chunk of lead attrac…

So I have been reading a book about relativity by Paul Davies ("About Time"). In this book he mentions that in order to fully understand the physical (or chemical) properties of heavy atoms such as gold and uranium, one has to take into account that electrons move at relativistic speeds around the nucleus. Additionally he mentions synchroton radiation (which might be not entirely related to my question). My question is that I was under the impression electrons do not actually move around the nucleus at all, but just 'are' at specific locations around a nucleus, based on the probability cloud of electrons in that specific shell. This does not really fit (for me) with what …

Is it physically possible for suns to be a exit point for black holes. Theoretically it makes perfect sense

I was reading on another topic that was closed because it apparently was "answered" I strongly disagree. Just because physics or science (at this point) considers asking if something can exist outside of time as asking how much does yellow weigh. There are multiple theories of other dimensions or universes. What exists outside of those bubbles. I am not a scientist but it has always baffled me how we can be constrained by this prison we call time. We exist a year ago, just as much as we exist in this moment. We may also already exist in the future. My question, without writing me off is, can anyone confirm the logic in what I mean even if it is illogical?