Table of Contents
Why did Einstein adjust his theory with a cosmological constant?
Einstein included the cosmological constant as a term in his field equations for general relativity because he was dissatisfied that otherwise his equations did not allow, apparently, for a static universe: gravity would cause a universe that was initially at dynamic equilibrium to contract.
Why is the speed of light in a vacuum constant?
The special principle of relativity: physical laws should have the same form in all inertial systems (systems at constant speed). The speed of light (in vacuum) is constant for every observer, independent of the movement of the light’s sources.
Is speed of light always constant?
Constant Speed No matter how you measure it, the speed of light is always the same. Surprisingly, the answer has nothing to do with the actual speed of light, which is 300,000 kilometers per second (186,000 miles per second) through the “vacuum” of empty space.
Why did Einstein assume that the speed of light was constant?
The popular explanation among physicists is that Einstein assumed that the speed of light was constant because Maxwell’s equations seem to state unequivocally that the speed of light had to be constant.
Is the speed of light in a vacuum constant?
It is a fact and it is constant. Einstein did not just assume that the speed of light in a vacuum is constant. Einstein derived as a fact (not an assumption) that the speed of light in a vacuum is constant.
Does light have a gravitational field?
It is well defined, being hf where h is Planck’s constant and f is the frequency of the light in your reference frame. Light does serve as the source of a gravitational field. Semi-classically, then, you can think of it as having a gravitational mass and thus falling in a gravitational field.
How many special speeds are there in relativity?
And there is only one special speed which they all measure to be the same—the speed of light. In fact, you can show that the theory doesn’t work if you try to add a second special speed. A short way of putting it is that in relativity there is only one constant to work with, the speed of light.