Relativity

i was home schooled until i was 16 and did not really get a chance to learn any of this stuff, keep that in mind if you feel this subject is childs play. before we start, lets do a warm up. imagine a 10 ft long pole being spun in circles with a motor at a constant speed. the part of the pole that is closest to the center of the circle is traveling less distance then the part that is further away from the center. speed is calculated by the time it takes for an object to travel a distance. so does this mean that the part of the pole which is further away from the center is traveling faster then the part that is closest to the center? there for, the part th…

When I come across the term "space" and the term "spacetime" am I right that they refer to different things ? Can they ever mean the same thing ? (I would not be surprised that ,if the user of the term did not understand the subject then that confusion would be expected) Would there be a generally accepted distinction between the two terms or would it depend on the context in which they are used? My inclination would be that "spacetime" would refer to the "spacetime" model that Einstein theorized and which has so far held up to scrutiny. "Space" on the other hand I would associate with a layman's appreciate of what apparently exists between "thing…

Can any object approach another at greater than light speed? For instance the two protons racing towards each other in the Large Hadron ColIider. is the gap between them closing faster than c? Alan

If space and time are linked for gravity, wouldn't that imply that the direction of a gravitational force emanating from a distant massive body is towards the past in time as well as towards some distant point in space? Sorry, I meant to post this in the Relativity forum

Hi all, I was trying to understand the time dilation in special and general relativity and after much time of "overthinking" I am pretty much stuck now. My problem is, that what seems to me to be the same premises apparently imply opposite things. In special relativity, for two inertial reference frames moving relative to each other with velocity v, we have the following formula for time dilation: T' = γ ⋅ T0 where T' is the time measured in the moving reference frame T= is the proper time measured in the resting system γ = 1/√1 - (v2/c2) ≥ 1 v is the relative velocity of the intertial reference frames c is the speed of light We see that: T' ≥ T0 We further know t…

Just for the sensory payback. Imagine you are in a spacecraft and have departed from Earth . (this is a bit like Star Trek) You are sitting in an onboard cinema with a big screen that is bathed in light being sent in your direction from the now receding Earth. With your popcorn in your hands you look at the screen (no film is playing -it is just reflecting back to you the light that is continuously arriving at the spacecraft. So the spacecraft keeps accelerating and , as you look at the screen the light changes progressively from blue tint to red tint. As you approach very close to the speed of light ,the reflected light becomes entirely r…

Two diamond shaped bodies are moving towards one another. The lower right side of one is aligned with the upper left side of the other. In a relativistic world, in the inertial frame of reference of the upper diamond at rest, the lower moving diamond is length contracted in the direction of its motion. And, in the inertial frame of reference of the lower diamond at rest, the upper moving diamond is length contracted in the direction of its motion. In the inertial frame of reference of the upper diamond at rest, the leading edge of the upper diamond and the upper edge of the lower diamond collide first. And, in the inertial frame of reference of the lo…

Suppose I am an observer and ,as such am situated at the [x,t]=[0,0] event point on a Minkowski chart. Now there is an event that occurs in my FoR at ,let's call it [X,T] (I have not worked out how to write mathematical equations here yet) I would like to reset the Frame of Reference to be from the point of view of (a new observer situated at) this new event which does not share an origin with the first observer's.How does this new FoR view the first observer's worldlines ?. Is that quite simple to do ? (the different observers are not necessarily stationary wrt one another) I have a second related question. Are there any alternative methods of gr…

As I understand it, the person near a black hole will appear to experience time slower than someone who isn't also near a massive object, from their perspective. As I understand it, the presence of more gravity will slow time as one approaches the presence of gravity. Does this slow down even the quantum processes? It seems that it must. Chemical reactions, electrical reactions, radiation....wouldnt all those processes also be slowed with the time? I know the person experiences time and it runs the same speed for them, even as they enter gravitational fields which slow the passage of time more and more. And here is where I get more confused. If space-time are someh…

If we are an observer at the origin of a possible set of events ,what are the actual empirical methods of taking measurements to give a numerical value to an event that occurs subsequently? I am situated at ,say Jodrell Bank at the point in spacetime [0,0,0,0,] and there is an event that we can say is located at [x,y,z,ct]. How do I empirically and repeatably* make those 4 measurements? I have no problem (I hope) with the "ct" measurement but how ,in practice would I make the spacial measurements? Can I bounce a beam of light off them if the system is set up to do that? Are there any other ways to do it? *obviously not repeatably for the same even…

I believe this is a projection of the tiling of a hyperboloid onto an x,y plane. Although this is far beyond my level of understanding , I have a question as to whether it is possible to use these Poincaré disk models in the plane to build a 3-dimensional model by perhaps rotating the disk /planearound one of its axes? If this is possible can this be seen as a projection of 4-D spacetime onto a solid,3-D "globe of the world* type" ball ? Can this be seen as a possible representation of the universe in a purely special relativistic way (without accounting for mass or energy) - kind of like a blank page? This is a link ,although I imagine it is obvious wha…

So hey guys, i am planning on sitting down and understanding all the equations that are of or relating to the theory of relativity. I know of some, but do you guys have an order that is best to study them in, especially if I am partially confident that i understand the theory of relativity, but i just want to know the math behind it. Thank You,

Let's consider rotating rod in gravitational field of heavy body. Axis of rotation is perpendicular to the rod. Does the rotation of the rod create more detectable gravity waves when the rotation axis is a tangent of curvature of space of the heavy body than when the rotation axis is perpendicular to the tangent of curvature of space of the heavy body?

I am not sure if this is the proper place to ask this, but I am sure someone will direct me to the right place if this is not. I was wondering what the mass and radius a spherical shell would need to be to significantly slow time inside the shell as opposed to outside the shell. Could such a shell be constructed to time travel into the future at any significant rate.

I have an app that says that a rocket that is ten meters in length that is moving at 200000 k/s when viewed from Earth will be roughly 7.5 meters in length. My understanding is that it's mass would increase because of it's velocity. Is this correct? It is also measured smaller, so it would seem logical to assume that any densities associated to the ship would also increase. Is this correct?

In Spacetime there are 4 dimensions which form a hyperbolic space. In everyday 3D geometry the gridlines form "cells" which take the form of common or garden cubes with 6 faces. What does the corresponding arrangement look like in 4D hyperbolic space? Are there any descriptions I can find -or even drawings? Can I refer to these objects as "cells" ? How many "faces" are they to correspond to the 6 in 3D space? Is that number 8?

Hypothetically, if you were on a ship that was travelling at just below c (for example 299792457,9 m/s) and you fired a gun at another person on that ship from where you were sitting in the direction that the ship was moving, what would happen?

Very brief electromagnetic history. / By Israel Socratus / ===… Part one. Oersted demonstrated connection between electricity and magnetism. Ampere gave mathematical explanation to this effect. Faraday discovered the reverse effect: relationship between magnetic and electric fields. ( how to use magnetism to induce electricity) Maxwell (using mechanical model: balls, springs, hooks . . . etc.) found mathematical equations to describe Faraday’s idea. Oliver Heaviside reformulated twelve (12) Maxwell’s equations to the modern four (4) equations. Hertz discovered Maxwell’s electro- magnetic waves and . . . he wrote that . . . EM waves cannot be…

This may be a dumb question... I really don't know... The expansion of the universe, from the big bang, has obviously left most if not all matter moving at a very high speed. My question is what kind of effect on our perception of time, while moving at such a speed, could this have? Could this factor change what we can observe about the past of the universe? Maybe the concept that everything else, or space itself, expands at around the same speed cancels it out or something? I'm not sure if that's even true. However, if the vacuum of space is in fact standing still compared to the speed at which we move through space, then could it not be possible that things happen…

So I know that Newton looked at gravity as a force and thus came up with a big set of calculations that accurately predict the effect of gravity on objects. However Einstein stated gravity as simply a geometric effect in the fourth dimension or space time. And his calclulation give a slightly more accurate representation of gravity. What I want to know is on what scale is Einstein's equation's "more accurate", I have heard that in fact we can use Newtonian formulas and they do not make that much of a difference and are usable enough for basic things, but in what situation would one need to resort to Einstein's formulas? How more accurate are they? GRACIAS, T…

I have understood why and how geodesics are related to gravity. So is gravity still a force? Also since the geodesics taken in the fourth dimension cause us to see planets taking orbits doe to gravity, what causes the elliptical shape of orbits? So far with all the reasoning i seem to only think that the orbits should be circular. Any enlightenment is awesome.

If the mass of a BH is at the singularity what difference does it make if the Schwarzschild radii touch when they merge?

so im studying up on the The theory of relativity. While reading about general relativity, I came across the principle of equivalency. I do not understand why there is no difference between the effects in an accelerating box and a box at "rest" in a gravitational field. I also do not understand how Einstein reasoned this theory. Any help is appreciated!

Would a supernova that makes a neutron star create a spherical gravity wave?

! Moderator Note Split from http://www.scienceforums.net/topic/93995-shapiro-or-shapiro-like-delay-of-gw-signals-split/ because asking these questions is OT for that thread. Speculation is OT for this thread As you have been told ad nauseam, Shapiro delay is a GR effect, so it's already included when you do a GR solution. It's not there in E&M, so it has to be accounted for separately. We're discussing this purported Shapiro delay effect. Don't raise other topics of discussion here. It's hijacking. Then don't post. There are three things you can do in this thread: defend the proposal, ask questions to clarify the proposal, or post accepted physi…