# What is the difference? special&general

• phy_freak
In summary, Special relativity deals with the relationship between matter and motion in a flat spacetime, while general relativity extends this to include the effects of gravity and curved spacetime. Special relativity does not deal with accelerated reference frames or gravity, while general relativity does. However, special relativity can still be used to describe accelerated reference frames in the absence of gravity, and Minkowski spacetime, a solution of general relativity, is completely unaffected by matter.

#### phy_freak

what's the difference between special relativity and general relativity?

This is question with a big but easily researched answer. You should first try your luck on the internet. Then come here for more pointed questions about these subjects.

bapowell is certainly correct, but I'm a softie so I'll give a quick answer:

Special relativity does NOT deal with a) accelerated reference frames or b) gravity. General relativity deals with both (at the same time, actually. The two situations are equivalent).

Correction: you can deal with accelerated reference frames (in the absence of gravity) in SR, with the help of some calculus. In these situations, spacetime is still "flat."

For gravitation, you need the curved spacetime of GR.

GR describes a relationship between the geometry of spacetime and its content of matter. The geometry determines how things move. ("Matter tells spacetime how to curve, spacetime tells matter how to move"). In particular, it determines which curves in spacetime we can think of as describing non-accelerating motion. The equation that describes the relationship is called Einstein's equation.

SR describes a spacetime called Minkowski spacetime, which is completely unaffected by the matter it contains. It's still different from the Newtonian/Galilean spacetime, which has all the properties that we intuitively associate with space and time. There's a natural way to associate a coordinate system with each inertial observer in both of those spacetimes. The main difference is that in Minkowski spacetime, there's a finite speed c that's the same in all of those coordinate systems, while in Galilei spacetime, the only invariant speed is infinite. This has a number of weird consequences, including time dilation, length contraction and relativity of simultaneity.

Minkowski spacetime is one of the solutions of GR. It's actually a solution that describes a universe that's completely empty, with no matter at all. SR is a theory of matter (that doesn't affect the properties of spacetime) and motion in that particular spacetime.

jtbell said:
Correction: you can deal with accelerated reference frames (in the absence of gravity) in SR, with the help of some calculus. In these situations, spacetime is still "flat."

For gravitation, you need the curved spacetime of GR.

I stand corrected!

## What is the difference between special and general?

The main difference between special and general is that special refers to something unique or specific, while general refers to something broad or common.

## How are special and general used in science?

In science, special is often used to describe specific phenomena or conditions that are unique or unusual. General, on the other hand, is used to describe common principles or theories that apply to a wide range of phenomena.

## Can something be both special and general?

Yes, something can be both special and general in different contexts. For example, a scientific theory may be considered both special and general depending on the specific application or situation.

## What is an example of something that is special in science?

An example of something that is special in science could be a rare species of plant or animal that has unique characteristics or behaviors.

## What is an example of something that is general in science?

An example of something that is general in science could be a law of physics that applies to a wide range of phenomena, such as the law of gravity.