Relativity

According to Einstein's theory of special relativity, when traveling at speeds close to the speed of light, you experience a significant shortening of distances in the direction of your motion. This phenomenon is known as length contraction. This means that any distance in the universe is reachable as long as we can travel close enough to the speed of light, because as v approaches c, γ\gamma becomes very large, and thus L becomes very small. For an observer who is stationary relative to your motion (an "outsider"), your clock seems to run slower; this is called time dilation. But from your own perspective inside the spaceship, time proceeds normally, and it is …

Hey guys, I am back. I once heard a paradox where a finite universe loops on itself when you go near the speed of light due to length contraction. Unfortunately, I forgot the solution. All I know was it was on PBS space time. I heard from this video from kurzgesagt, that one possible model of the universe was a doughnut. Basically, you go in one direction, and it takes long to loop around, but in another direction, you get back quicker. My thought is what if you went at such a percentage of the speed of light, that the short loop of the doughnut loops around. Now, what would the other person see that goes around the long loop of the doughnut going at the same speed. One o…

I was doing some reading due to a recent thread on Dark Matter, and came across a 'problem' that Dark Matter may provide an answer to. As I had never heard of this problem, I thought I should investigate, and I'm only just beginning. Hopefully some of you guys have some insights. Apparently super massive Black Holes of the galactic center type have a merging problem. As they approach each other, an effect termed 'dynamic gravitational drag', stops their orbits from further decay, and establishes a stable orbit at about 3 Light Years ( one parsec ). Apparently this is dictated by the math, which I haven't seen yet, and probably won't understand when I do. Thi…

A worldline cannot be associated with two different reference frames, so if Lemaître coordinates define a reference frame, Painlevé coordinates do not. The Painlevé coordinate system does not appear to constitute a relativistic reference frame. Indeed, in the (dt,dr) coordinate system of Schwarzschild, the coordinate system associated with Gullstrand–Painlevé (dT, dr + √(Rs/r)dT) does not form a reference frame because the light cone tilts. In relativity, the light cone must not tilt. To maintain isotropy in another reference frame, the simultaneity line must be redefined by a boost. Painlevé metric is ds² = dT² - (dr +√(Rs/r)dT)²

Tell me, what do you think about this idea of a gravity engine? If you take a particle accelerator and give it the shape of a spiral so that the particles move along a spiral trajectory, then such a spiral should pull space into the center of itself at near-light speed. If the total mass of the particles is large enough, then it must draw in space with sufficient power to ensure movement at a speed close to the speed of light. I understand that it will take a huge amount of energy, but the idea itself is not fantastic and is quite viable. And if you close this spiral into a bagel, then a fixed area of space will move along a closed trajectory. And in this way, you can cre…

Having only lately caught up with the ideas surrounding the Alcubierre warp drive concept, I am still struggling to understand how such a system would cope in regions of seriously non-flat spacetime - say, performing an otherwise lethally close "flyby" (excuse the grammatical hand-waving here) of a neutron star or stellar-mass BH. Reading between the lines from some online articles, none of which directly address this subject, the thought comes to mind such a spacecraft and its occupants would be unaffected by such an encounter while in warp mode, no matter how intense the gravitational tides might be. Nonetheless, the suspicion is that this may not be correct, though all…

Dear Science-Forums Community, I hope this message finds you well. I am writing to seek your expertise and feedback on a new table/framework that I have developed. This table/framework aims to I would greatly appreciate it if you could spare some time to review this new table/framework and provide your valuable insights. Your feedback will be instrumental in refining and improving its effectiveness. If you are interested in assisting or have any questions, please let me know. I am eager to contribute to the community's knowledge and look forward to your response. Astrogeomanity Table Theory Astrogeomanity combines elements of cosmology, pa…

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Scales depend on mass, just like gravity. The greater the mass, the more the scale moves, deforming its initial position; The lower the mass, the less it moves and the less it deforms with respect to its initial position. Just like gravity, the greater the mass, the more space will curve, and the smaller the mass, the less it will curve. I think this would be an example of the little interest that humans of the past had in observing natural phenomena. Maybe someone is wondering, did an apple have to fall on Newton's head for someone to occur to him that something causes bodies to be attracted to the ground, or downward. Yes, the scale states that that somet…

If two space craft were approaching each other at 99.999% of the speed of light, what would the speed of each appear to be to the other since the speeds would not add up like two trains traveling at 100 mph toward each other.

We all know the twin paradox with the travelling twin returning younger than the stay at home twin. The acceleration in order to return is considered important for the outcome. Now, let's add a new acceleration, let's consider the travelling twin revolving around an axis, in order to feel as on Earth surface (same g force). If we have 1 clock on the Earth twin location (#1) and 2 on the ship, one on the axis of rotation (#2) and the other (#3) where the traveling twin is staying, which clock is recording the least time between departure and arrival and why? In order to see if only the (added) acceleration is important, let's add another, bigger, "wheel" on the s…

In another thread, where twin paradox was discussed, Markus Hanke said: I asked: The first answer, from Mordred, was: True, but he didn't understand my question. The second answer, from Markus, was: Again, not what I asked, so I'll try again here. The traveling twin, after the turnaround, accelerates toward Earth/Sun and he immediately see the light from the Sun blueshifting. As long as he accelerates, the light is blueshifted again and again, due to the increase in speed towards the source of the light (the Sun). So, as long as his accelerometer indicates an acceleration towards the Sun, the light of the Sun is blueshifted again …

Full disclaimer :I have be thinking about those twins... When the accelerated twin speeds off his internal system must evolve (as does the watch in the cabin) When they are actually under acceleration is there (in their own frame of reference) any change in the perceived passage of time ? None because the perceiver is accelerating at the same rate as the watch? What about the "view" from the the unaccelerated frame of reference of the other twin? It cannot see but can it deduce that em signals (within the cabin)are being red shifted in one direction and blueshifted in the other? Would that have the effect…

Hi could this be a more simple way to calculate time in light clock time dilation experiment? On the lower picture the side of triangle 1/2xvxdelta t’ is actually 0.5 sec time - for spweed v=0 to c I will repeat this - the time tv =0.5 sec for any speed from 0 to 3x10e8 . for side L of left triangle at the bottom picture file is equal to delta t this time is easy to calculate delta t=2L/c to calculate delta t’ (Delta t’)^2=(0.5 sec)^2 + (delta t)^2 is this more simple way to calculate time dilation for light clock experiment ? And is there time dilation at all?

Imagine a pair of fictional events the first being the murder of Caesar by one of his enemies using a sword and the second fictional event the murder of JFK by someone using the same sword some 2000 years later. The spacetime interval between the two events is calculated by choosing the earth as a reference frame ,measuring the distance between Rome and Dallas ,choosing the units of time and applying the s^2=(ct)^2-r^2 formula. Suppose instead we were to follow the sword across the centuries and make a note of the time and places in which it was recorded as having been prior to it being used again in the fictional killing of JFK. Could we calculate spa…

Suppose we have two frames of reference that only differ in that they are separated by a fixed distance And suppose each frame makes measurements of an object that is moving relatively to both at any speed between 0 and c. Is the concept of spacetime necessary for each frame to make that measurement and so that they agree in every case? I am asking this because it has been said (was it by Minkowski?) that our previous till then understanding of space and time must be replaced with a new amalgam of the two (spacetime) and I am wondering if this is because all frames of reference are relatively in motion in practice or whether the reason is deeper tha…

One of the main arguments against the trampoline analogy for spacetime curvature is that the heavy object distorting the fabric of the trampoline/spacetime fabric itself relies on gravity to act ... Suppose we just have two bodies ,one of which is a source of mass/energy and they are connected by a geometric line that is marked off in equal lengths of spacetime distance. There is a tension between the two objects (and so along the geometric line?) for the "simple" reason * *that the two objects have in principle a common source at the beginning of the universe ,whatever that looked like. Going back to the two objects,as time progresses the massive/ener…

Hi all. I've been trying to calculate how much energy would be released from dropping things onto the surface of a neutron star from certain heights. I'm using... [math]\Delta E = GMm (\frac{1}{r_2} - \frac{1}{r_1})[/math] To calculate the potential energy that could be released. Where G is the gravitational constant, M is the mass of the neutron star, m is the mass of the falling object, r2 is the radius of the neutron star plus the height and r1 is the radius of the neutron star. Phew! Would this be the correct formulation to use here? I don't know if I would need to take relativistic effects into account here (and I wouldn't know where to start with…

I figure they would because their orbits should have an effect on the electromagnetic field detectable at a distance?

Is it possible trap light in a stable circular orbit around a tiny Schwarzschild black hole such that the energy of the light is greater than that of the black hole?

I know that there is Einstein's equation that relates energy and matter. However, I was curious about what would occur if there was a universe where light didn't exist. Assuming that's even possible, would there be any relationship between matter and energy or would they be completely separated? Would they fail to exist in such a place? Thank you for indulging my curiosity.

According to Loop qunatum gravity (Unproved theory) the spacetime is made of quantum gravitational grains, some "Knots" contain the volume of the space ( in discrete values), they are bined by the "links". A group of Knots or rather a set of lines which touch each other form a graph. Without entering into specifics; the theory enunciates that space-time is made of these grains, they create the gravitational quantum field. So, If time is relatred to space and space-time is created by grains, on microscopic grains scale time doesn't exist. Because space and time are created by the "dance" of these elemenatry components. But leaving out the loop quantum theor…

You Physicists claim gravitational waves (exist), 1. so what kind of wavelength (& range) do you expect? 2. & what (kind of) medium (properties) are you talking about?

Time travel is not logically possible if we assume Einstein's theory of relativity is more or less the true explanation of the universe. Einstein's theory of relativity implies a block universe, which is to say that the future already exists, and the past still exists. Ultimately, the universe is a 4d structure that doesn't change. And as far as we know, this entire structure doesn't age in another temporal dimension, and it doesn't exist inside of another spacial dimension either - it simply just exists. Now for an example of the illogical idea of time travel. Imagine that it is the 3rd of January at 11:00pm. You are alone in your house. A week late…

As a gravitational wave passes though a constellation of precise clocks, would it be possible, at least in theory, to detect its passage by measuring time difference between clocks? If so, is it harder to make such measurements than to measure spatial distortions?