Relativity

Hi, can you guys tell me what is the mechanism of space (universe) expansion? Does it interact with time? Or it is because of Gravitational Force? or electromagnetic energy?

When one of your twin siblings has travelled to space and when he returns, he will be younger than the twin sibling. Why is it so ? Can anyone explain me on this ?

My understanding of red shift is that objects moving away from an observer take on a red shade because the photon's frequency is reduced and wavelength is increased (stretched) as it travels from the moving object towards our eye (the distance between the two grows as the photon travels at us)...And being in front, one would see a blue shift as the photon's frequency is increased (compression)...cuz the distance between the 2 objects is getting smaller as it approaches us...so expanding space would be seen with a red shift, and compressing space is seen as blue We also see redshift in objects with massive gravity as well...in comparison to the above, gravity would also t…

It seems that all, somewhat massive objects, create gravity (curve space-time). But is this the same act of creating gravitational waves or radiation? It seems that gravitational waves exist when objects interact in each other's fields. But does this account for more gravitational force (curvature) or just ripples within it that effect time and length distortions? The question that i could not answer while reading was..."Does gravity exist beyond this radiation of waves or not?" There is gravity created by GR and then there are sometimes radiations of gravity which actually "shed a bit" of the gravitational force it had....and they "travel" out through the field...…

In Minkowski space, it seems that the axis for the dimension of time is represented by the light cone. And it also seems that this dimension is always "aligned" with one of the space dimensions. The observer in the "hypersurface of the present" seems to exist in a 2 dimensional space frame (x,y) that rotates or transforms at perpendicular angles to the observer's motion, which becomes the space frame (z) and the dimension of time. I am basically describing a graphic at wikidpedia found here: http://en.wikipedia.org/wiki/Minkowski_space Then I was reading through the Schwarzschild metric info and noticed these 2 terms in the equation. θ is the colatitude (angle fro…

Hey Guys, so i was reading Hawking&Ellis a bit and still encounter always problems with the Penrose-Diagrams. Looking at the Penrose-Diagram for the rotating Kerr-Black hole (just one illustrating picture at the end) i come up the following question: There are two regions III (with the singularites inside) which are seperated from each other. Given i am in the region II (between the chauchy-surfaces, where only the r coordinate is well defined) how would you describe the trajectories of observers who want to go to either one of the two singularities? In other words how would you control your trajectory to do that (i.e., what measurements you would make to ensure tha…

That's the question. If anyone will answer it - I may post my 'uneducated' guess at it.

I just hit a wall of confusion and was interested in some input... In "Relativity" as a whole, we have general relativity and special relativity...and it seems that special relativity describes the particles as energy and begins the QM equations which sprout all over the place..and GR only concerns itself with geometrical values and not particles... With special relativity being particle physics and general relativity not being unified with particle physics, does that mean special and general relativity dont unify? I am confused. Whoa...im so wrong its not even funny.. This may be the dumbest question ever asked on a physics forum...man...my brian came unwound with…

Is what this guy is saying true? I've searched the internet for an answer. So far haven't found anything on this. Thanks! http://www.speed-light.info/speed_of_light_variable.htm

I posted this in relativity because it includes a discussion, or at a least mention of E=mc2. I was studying single slit experiments a couple years ago, during my double slit phase, of my uncertainty era. I noticed something interesting and always wondered if anyone had noticed before...ive looked for info on the subject and found nothing that speaks to this directly. When you make the single slit the same width as the incoming length of the wavelength. For example, slit width=1 and wavelength=1...The resulting interference pattern creates a propagation that matches the slope of a graph of any squared number. A 45 degree angle. 45 up from V=0 and 45 down for v=0...…

It's my understanding that when something is going near the speed of light in reference to an observer, time dilation occurs and time goes slower for that fast-moving object. However, when that object goes back to "rest", it has genuinely aged compared to the observer. It's not like time goes slow for a while, and then speeds back to "normal," so that the age of the observer once again matches the object. The time dilation is permanent. Why wouldn't the same thing happen with length contraction? Since the two are so related, you'd think if one is permanent, the other would be also. And from everything I've read so far, length contraction is not permanent. An object will b…

Is it meaningful to ask whether general relativity is holonomic or nonholonomic, and if so, which is it? If not, then does the question become meaningful if, rather than the full dynamics of the spacetime itself, we consider only the dynamics of test particles in a fixed globally hyperbolic spacetime? For the full problem, my immediate conceptual obstacle is that it's not obvious what the phase space is. In ordinary mechanics, we think of the phase space as a graph-paper grid superimposed on a fixed, Galilean space. The definitions of holonomic and nonholonomic systems that I've seen seem to assume that time has some special role and is absolute. This isn't the ca…

I'm going through Kerr metric, and following the 'Relativist's toolkit' derivation of the surface gravity, I've come to a part that I don't understand. Firstly, the metric is given by [latex]\mathrm{d}s^2=\left(\frac{\Sigma}{\rho^2}\sin^2\theta\omega^2-\frac{\rho^2\Delta}{\Sigma}\right)\mathrm{d}t^2-2\frac{\Sigma}{\rho^2}\sin^2\theta\omega \mathrm{d}\phi \mathrm{d}t+\frac{\Sigma}{\rho^2}\sin^2\theta \mathrm{d}\phi^2+\frac{\rho^2}{\Delta}\mathrm{d}r^2+\rho^2 \mathrm{d}\theta^2[/latex] With [latex]\rho^2=r^2+a^2\cos^2\theta,\quad \Delta=r^2-2Mr+a^2[/latex], [latex]\Sigma=(r^2+a^2)^2-a^2\Delta\sin^2\theta,\quad \omega=\frac{2Mar}{\Sigma}[/latex] The …

Since you seem to understand the cone very well, a simple question in the hope to find (maybe) someone who understands me: You wrote What about the inside part of the cone? can we directly observe the inside part of the cone? To see inside would require a signal travelling slower than light.

time is a means to measure matter in motion

My spaceship is receding from a distant planet where there is a clock. I am looking back at this clock through my trusty telescope. As my speed relative to the planet approaches c, does the clock appear to stop (or just slow down) ? Thank you. PS I believe Einstein pondered this problem when in a tramcar moving away from the clock tower in Berne.

So lets say you have two objects... They are traveling away from each other at, say 90% the speed of light. Wouldn't that mean that they, from the frame of veiw of each object, traveling away from each other at 180% of the speed of light? This breaks the rule that says that you can't travel faster than the speed of light. So how does this work? Thanks in Advance

What is the lowest speed you can travel to go 200 years into the future within a 10 year time frame by going in a circle around the earth?

My question is, does time have a speed? could events be going along faster in different places in the universe? can it be speed up or slowed down?

A stressed field may be simply defined using various classes of magnitudes. The classes of magnitudes are associated with scalars, vectors, tensors, and outer products (also tensors of higher rank). A general metric (angular metric) may be obtained from a class defined field. This will reduce to the Kerr-Newman metric. .The Stress Field.htm

Can a supernova explosion (or implosion?) on its own create gravity waves? Or do you need to have (say) two stars 'merging' into each other for this effect to happen? In other words, is displacement necessary for the generation of gravity waves? Many thanks.

When the phrases time dilation and length contraction are used, what do these really mean? For example, say in the travelling twin paradox, there is a perceived time dilation that both twins observe happening to the other, as the travelling twin sets off (and a perceived time contraction as the twin returns). I understand these meanings - perceived because it is a consequence of the twins moving away from each other, each twin observing the same perceived time dilation as the other. But I have also seen time dilation being used as an actual time dilation - i.e. in the sense of 'rate of time' slowing down - and that I do not understand? If the travelling tw…

In a recent thread (now rightfully deposited in "Trash"), a member was disputing the idea that mainstream science can measure particles rest mass. Contrary to those crank claims, the measurement can and IS done, there are multiple methods (you can google "rest mass measurement"). I will present a method that, though quite routine, doesn't show up in the search (not clear why). In a cyclotron, a particle of charge [math]q[/math] and rest mass [math]m_0[/math] will describe a circular trajectory of radius [math]R=\frac{\gamma m_0 v}{qB}[/math] when subjected to a transverse Lorentz force due to a magnetic induction [math]B[/math]. [math]v[/math] is the measured speed of th…

I've just met a problem when I differentiated the mass-velocity equation. In m2(c2-v2)=m02c2 because the right one is a constant after differentiation , i got d [ m2(c2-v2) ] = 0 which means c2 d (m2) = d(m2v2) i don't think it makes sense, hope someone can help me point out the wrong step，thanks a lot！

There are a lot of well known thought experiments to explain the effects of time dilation in special relativity. One person remains on Earth, the other person travels in a rocket shit at near C. After 5 of the light years, the rocket ship returns to Earth and the other person has aged 105 +/- years. If both of those people were physicists, which one would have the accurate data? More applicably, let's say a physicist on Earth and a physicists on the ISS both observe the same astronomical event and we're going to use one result as the new "standard" for a system of measurement. The physicist on the ISS is experiencing time more slowly and because of the accuracy of time …