Relativity

In the einstein equation [math]R_{uv}-0,5 R g_{uv}+ \Lambda g_{uv} = \frac{8\pi G}{c^4}T_{uv}[/tex][/math] i understand that units of [math]g_{uv}=L^2[/math] and then [math]R=\Lambda=\frac{1}{L^2}[/math] ¿[math]R_{uv}[/math] is dimensional less?? [math]G=\frac{L^3}{T^2 M}[/math] and [math]\frac{G}{c^4}=\frac{T^2}{M}[/math] then ¿¿¿[math]T_{uv}=\frac{M}{T^2}[/math]?????

In the wiki entry on time, it says http://en.wikipedia.org/wiki/Time#Physical_definition Can anyone better help explain what physicists mean by time in general relativity?

ok people, let me tell you this; Tesla and Einstein, in my opinion, have been the two most successful physicist of the 20th century. The problem is that Tesla didn't get what he deserved, while Einstein's name lived out to be the most popular name of the 20th Century (and if I've been informed accurately Tesla is not mentioned much in US school textbooks nor Australian or UK textbooks and most of the students wouldn't have idea of who the hell Nikola Tesla is - and probably many who are reading this thread would've asked themselves the same question). Well, I'm using Einstein just for a comparison in this thread, the main character here is Nikola Tesla. Let's just…

hello i understand that in a flat space the metric is [math]\eta_{uv}dx^udx^v[/math]...i know that this means that the light follows straight geodesic in this space time... but ¿what would means that metric is [math]f(t)\eta_{uv}dx^udx^v[/math] where f(t)=infinite in t=0 and f(t)=0 in t=infinite.....obvious i understand the matematics, but physically ¿what means?.....for example..¿what means that in bing bang in t=0 f(t)= infinite????

Can one measure one's speed based on how much energy it takes to accelerate? For instance, in Newtonian Physics, increasing speed by a certain amount (say, 1 m/s) took a certain amount of energy for a certain amount of mass. In relativity, it takes more energy the higher speed you are at. One might be able to use a measurement of this increase in necessary energy to calculate a seeming "absolute speed". For example, x J per 1 m/s compared to x + y J for 1 m/s at a higher speed. With this in mind, one could calculate one's speed by measuring the amount of energy needed to increase speed by a certain amount. Plugging this energy into an equation that creates …

I was kicking something around with a few guys a couple of weeks back, and something came up. I wonder if anybody here could confirm or or counter what I was told? In The Foundation of the General Theory of Relativity on page 185 of Doc 30, 3.6 Mbytes, Einstein says "the energy of the gravitational field shall act gravitatively in the same way as any other kind of energy". The people I was talking to said that this energy is not included in the Einstein Field Equations. They seemed to know what they were talking about, but I thought surely not? I'd appreciate any information you can offer.

this has prob been answered someplace in this forum but didn't search it. But in E=mc^2 why do you need to have the speed of light in the equation? How come its not just the exchange energy is matter an vice versa? Thanks

How much spacetime is there inside the event horizon of a non-spinning uncharged black hole of mass M? I know that a black hole has a Schwarzschild radius of [math]r = \frac{2GM}{c^2}[/math] and a sphere a volume of [math]V = \frac{4}{3} \pi r^3[/math], for a black hole volume of [math]\frac{32}{3} \frac{\pi G^3 M^3}{c^6}[/math]. However, I think the above volume would be in our metric rather than accounting for the distortions of spacetime. If you account for spacetime distortion when measuring the volume, what would you get?

Also what is the twin paradox?

Hello, I’m sorry, I can’t English well. But, I have a question! From the mass and energy equivalence E=mc^2 I had some read the book( Gravitation and Spacetime, Hans C. Ohanian and Remo Ruffini ) In there, gravitational potential energy is gravity source also. However, from the mass and energy equivalence Gravitational potential energy is [math]U = - \frac{{GMm}}{r} = + m_{gp}c^2 [/math] or [math]U = - \frac{{GMm}}{r} = - m_{gp}c^2 [/math] ([math]m_{gp} = \frac{{GMm}} {{rc^2 }}[/math]) Which one is true? In the chapter 2.7( Gravitation and Spacetime, Hans C. Ohanian and Remo Ruffini ) At the solar system, difference of acti…

Someone emailed me the following statement that does not make sense to me. "The Einstein theory is an example of a non-linear theory in which the stress energy tensor vanishes in a mass zero zone." Is there any evidence of nonlinearity? How can the tress energy tensor vanish near a mass when the field does not vanish?

I am told that as one falls into a black hole, the gravitational pull eventually becomes so strong that it literally pulls one apart. The difference in force between one's feet and one's head is so powerful that it has just this effect. But then I wonder whatever happens to the electromagnetic force holding the atoms and particles together within one's body. Under normal circumstances (i.e. in the absence of black holes), if a body feels a pull at one end and nothing at the other (or at least a weaker pull), the latter end just gets pulled along (in virtue of the electromagnetic bonds holding it together) by the former end. Why wouldn't the same happen in the case of …

According to Einstein's assumption, light always travels at 'c'. But, according to him, only the relative velocity changes. Isn't this a wrong assumption? Because, everything has to gradually lose energy. Won't photons dissipate an infinitely small amount of energy as they move, making them lose some energy? Second part of the question: Will gravity affect the movement of photons? Because, if they have zero mass, only then there's no gravitational effect. This is due to considering their 'rest' mass as zero. Shouldn't it just be negligibly small?

Relative velocity is how we are seeing things right? So how does one go about calculating relative velocities? I need a rebrush on my kinematics!

Do black holes suck in light due to their immense gravity? I thought light has no mass and subsequently it does not get affected by such curvatures of space-time? Also, from the Newtonian point of view, it has no weight. So how do we determine that light will get sucked in and why? Basically, for light to bend, there has to be a refraction right? So, it has to travel through a new medium. So how is it possible? I've heard of this. Is it true?

I've been having some thoughts lately and just want to put them out here. 1) We can only see as far as light has traveled since the big bang. 2)If there are other universes - than something has to be able to travel faster than the speed of light in order for them to form - Could this be what binds matter together? 3)If something is traveling faster than light - How would we be able to see it - In the subatomic world -things need to be observed 4)Black holes are dark because light can not escape it - In order for than to happen - things have to be traveling faster than the speed of light 5) Could this be the creation of "Dark Matter" Those are my …

ansatz is [math]g_{mn}dy^mdy^n+W^2(y)g_{uv}(x)dx^udx^v[/math] if [math]R_{uv}=\tilde{R}_{uv}-\frac{g_{uv}}{(p+1)W^{p-1}}\nabla^2W^{p+1}[/math] eq1 why eq 1 is??? [math]\frac{1}{p+1}(\tilde{R}W^{-2}-R)=pW^{-2}\nabla W \nabla W+W^{-1}\nabla^2W[/math] i tried to multiplicate eq1 by [math]W^{-2}g^{uv}[/math] but i don't go to the result

in a D space time of coordinates [math]x^u,y^m[/math], with u=...p+1, m=...D-p-1, and A=.....D if [math]R_{MN}=8 \pi G_D (T_{MN}-\frac{G_{MN}T^P_P}{D-2})[/math] (eq1) I don't understand why [math]R^u_u=\frac{8\pi G}{D-2}((D-p-3)T^u_u-(p+1)T^m_m)[/math] eq 2 [math]R^m_m=\frac{8\pi G}{D-2}((p-1)T^m_m-(D-p-1)T^u_u[/math] eq 3 i tried to multiplicate eq1 by [math]g^{MN}[/math] and then [math]R=8\pi G_D(T-\frac{T}{D-2})[/math] but, i don't go to the eqs 2 and 3

Can anyone tell me the direction of the resiltant velocity vector for the composition of velocities equations of SR? Thanks

in a paper (hep-th/9905012)says that de (0,0) einstein tensor is [math]G_{00}=3(\frac{\dot{a^2}}{a^2}-\frac{n^2}{b^2}[\frac{a''}{a}+\frac{a'^2}{a^2}-\frac{a'b'}{ab}])[/math] (eq1) and [math]T_{00}=\frac{\rho\delta(y) n(t,y)^2 }{b(t,y)}[/math] where [math]a=a_0+(\frac{|y|}{2}-\frac{y^2}{2})[a']_0-\frac{y^2[a']_{1/2}}{2}[/math] (eq2) and [math]a''=[a']_0 (\delta(y)-\delta(y-1/2) ) + ([a']_0 +[a']_{1/2} ) (\delta(y-1/2) - 1 ) ) [/math] with [math] [a']_0 [/math] is the jump of a detivate of a in y=0.... other relation are: [math] \frac{[a']_0}{a_0b_0}=-\frac{k^2 \rho}{3} [/math] (Eq 2.5) [math]b=b_0+2|y|(b_{1/2}-b_0)[/m…

Can someone explain me the difference between general and special relativity?

This is isn't homework, just something I decided to have a crack at, alongside my current course, and forgot about it. Just need confirmation on the last step. I wanted to find the connection coefficients of a hypersphere, so the line element is... [math]dl^2=R^2[d\psi^2+sin^2\psi(d\theta^2 + sin^2\theta d\phi^2)][/math] so... [math]dl^2=R^2d\psi^2+R^2sin^2\psi d\theta^2+R^2sin^2\psi sin^2\theta d\phi^2[/math] Where... [math]x^1=\psi[/math] [math]x^2=\theta[/math] [math]x^3=\phi[/math] So the metric is... [math]g_{ij} = \left[ \begin{array}{ccc} R^2 & 0 & 0 \\ 0 & R^2sin^2 (x^1) & 0 \\ 0 & 0 & R^2sin…

Mass increases as you approach the speed of light. I have thought about the physical consuences of this and wondered how does what work? (not why does that work?) I mean does atoms just appear out of nowhere in even distributions or what?

I read two post on this site that make me realize that I am the only one who gets it, about a certain topic, which I wrote a paper on in the 90's. I never published, but I did have it reviewed by a single physicist, who said the math was correct, but he didn't like my conclusions. However, If my conclusions are correct - they are in my opinion very logical - which I have personally taken for granted all these years, they have the potential to affect cosmological observations, which never occurred to me before, and they have the potential to influence theory on electro-magnetism. I guess that means I am sort of obligated to publish, doesn't it? Morally? Ethics.... …

If you go at light speed time stops for you... What does that mean? Does it mean if we go faster than light, it's back in time or forward to future?