# What is Einstein’s special theory of relativity?

The theory of special relativity explains how space and time are linked for objects that are moving at a consistent speed in a straight line

• Black
4 weeks ago

There’s an easy way to remember whether you’re talking about the Special Theory of Relativity or the General Theory. Special Relativity (SR) is all about “speed”, i.e. the speed of light, and why that speed is special in the universe. General Relativity (GR) is all about “gravity”, and how that works. SR is speed relativity, while GR is gravity relativity.

Yes, technically GR also includes SR as a subset of it, and SR can be derived from GR. But really when you want to calculate the effects of things near the speed of light, using just the SR equations is far easier than trying to use the GR equations. Also SR is fully compatible with that other great theory of physics, Quantum Mechanics. When you combine SR and QM together, you get a new encompassing theory called Quantum Field Theory. But you can’t combine GR with QM or QFT to come up with an all-encompassing theory known as Quantum Gravity, their equations just don’t work together, they lead to infinities.

• ?
4 weeks ago

e=mc2 . simple isnt it we use this on a bullet or or a rocket . seems you where asleep at school or you should know what it means .

• Andrew Smith
4 weeks ago

It is that given the speed of light is constant for all inertial observers the explanation must be that both length and time alter for different inertial observers.  The remainder of the theory are the consequences of this one seemingly trivial statement.

• ?
4 weeks ago

The basic idea behind special relativity is that PROPERLY formulated laws of physics look exactly the same to all inertial observers (uniform motion).

Properly formulated laws of physics are classical physics that have been mapped from a formulation where space and time are treated independently, to a formulation that puts space and time on the same footing. For instance, the magnitude of classical momentum depends on the velocity of in an inertial reference frame. If we map the classical momentum (a 3-vector) to momentum in spacetime (4-vector) by adding a time component of momentum to the three space components, we then have a reference frame independent magnitude.

It is important to recognize that relativity doesn’t exist because the speed of light is constant, but that the speed of light is part of a reference frame independent description of physics that exists because of the concept of relativity.

It’s also important to realize that you CAN deal with acceleration in special relativity if you know what you are doing. There is an acceleration 4-vector in special relativity. However, you can no longer expect the laws of physics to look the same in both inertial and accelerated frames. You have to go to the wonders of general relativity for that.

• Nemo S
4 weeks ago

Straight lines are a mathematical perception gravity bends everything into a circle …

N.S

• ?
4 weeks ago

It’s soooo special

we’re not allowed to tell you.

• Anonymous
4 weeks ago

Sure, the time is not the same for anyone….

• ?
4 weeks ago

In Newton’s mechanics, time was universal. Every one had a same time scale. 1 second used to be1 second when person is stationary or moving with a constant velocity.

Since Michelson Morley experiment showed that velocity of light can not be added to any velocity. Because of that that remains the same for all. When Maxwell set of equations were modified according to old rule the form Maxwell equation did not retain the same form. Therefore, Lorentz said the coordinate transformation along with time transformation follow different rules. These are Lorentz transformation. Einstein used them to show mass is not a universal constant and it has in built energy=mc^2 called rest energy. This changed whole physics. At low velocities far below velocity of light all mechanics studied till now is called as the classical mechanics. When the velocities of reference frame is comparable to velocity of light then we need to use relativistic mechanics. Conditions set for the coordinate frame is that it should move with a constant velocity (inertial frame). All equations of science retain the same form. This can be confused more then it is called philosophy.

Einstein said that c is the same in all inertial reference frames. This is his relativity theory.