Difference Between Special & General Relativity

Jaami M.
Messages
28
Reaction score
1
Nugatory said:
This idea is one of the essential concepts behind Special Relativity, so if you're comfortable with it you're well-positioned to start learning SR.
So what is the difference between the two? Special Realitivity and General Relativity.
 
Physics news on Phys.org
Here goes (had to try it) ;)

Special: speed of light, E=mc2
General: gravity
 
  • Like
Likes Jaami M.
m4r35n357 said:
Here goes ;)

Special: speed of light, E=mc2
General: gravity
Thank you
 
Jaami M. said:
what is the difference between the two? Special Realitivity and General Relativity.

SR only deals with situations in which gravity is not present or can be neglected; in such situations, spacetime is flat, or can be approximated as being flat.

GR deals with situations in which gravity is present and cannot be neglected, and spacetime is curved.
 
  • Like
Likes vanhees71
PeterDonis said:
SR only deals with situations in which gravity is not present or can be neglected; in such situations, spacetime is flat, or can be approximated as being flat.

GR deals with situations in which gravity is present and cannot be neglected, and spacetime is curved.

And, if OP is wondering about why the names are what they are...

The case in which gravity is not present or can be neglected is a special case (curvature is zero) of the more general theory that works for all values (zero or non-zero) of the curvature.
 
  • Like
Likes vanhees71
Although not directly related to the question, OP may also be interested in the relative difficulty of the math behind the two theories.

High school algebra can get you to a decent understanding of SR: derivation of Lorentz transforms from Einstein's postulates; calculation of spacetime intervals and proper time along the worldlines of objects moving at constant relative velocities; able to explain the elementary "paradoxes" such as pole-barn, bug-rivet; the various approaches to the twin paradox.

GR requires multi-variable calculus, differential geometry, tensor calculus, solving some of the most challenging non-linear partial differential equations you'll ever encounter. There's close to a decade of high school and college math between SR and GR.
 
  • Like
Likes elusiveshame
OK, so this has bugged me for a while about the equivalence principle and the black hole information paradox. If black holes "evaporate" via Hawking radiation, then they cannot exist forever. So, from my external perspective, watching the person fall in, they slow down, freeze, and redshift to "nothing," but never cross the event horizon. Does the equivalence principle say my perspective is valid? If it does, is it possible that that person really never crossed the event horizon? The...
ASSUMPTIONS 1. Two identical clocks A and B in the same inertial frame are stationary relative to each other a fixed distance L apart. Time passes at the same rate for both. 2. Both clocks are able to send/receive light signals and to write/read the send/receive times into signals. 3. The speed of light is anisotropic. METHOD 1. At time t[A1] and time t[B1], clock A sends a light signal to clock B. The clock B time is unknown to A. 2. Clock B receives the signal from A at time t[B2] and...
From $$0 = \delta(g^{\alpha\mu}g_{\mu\nu}) = g^{\alpha\mu} \delta g_{\mu\nu} + g_{\mu\nu} \delta g^{\alpha\mu}$$ we have $$g^{\alpha\mu} \delta g_{\mu\nu} = -g_{\mu\nu} \delta g^{\alpha\mu} \,\, . $$ Multiply both sides by ##g_{\alpha\beta}## to get $$\delta g_{\beta\nu} = -g_{\alpha\beta} g_{\mu\nu} \delta g^{\alpha\mu} \qquad(*)$$ (This is Dirac's eq. (26.9) in "GTR".) On the other hand, the variation ##\delta g^{\alpha\mu} = \bar{g}^{\alpha\mu} - g^{\alpha\mu}## should be a tensor...
Back
Top