Thread: What is the difference between dark matter and dark energy?

Since Einstein's theory relates matter and energy as different states of the same thing, is it valid to think about dark matter and dark energy in the same way? Are they two states of the same dark "thing"? Are they interchangeable?

Originally Posted by belgi

Since Einstein's theory relates matter and energy as different states of the same thing, is it valid to think about dark matter and dark energy in the same way? Are they two states of the same dark "thing"? Are they interchangeable?

No, they are not interchangeable.
Dark energy is the name given to the unknown cause of the accelerating expansion of space between galaxies and clusters of galaxies (In local gravitationally bound regions, the effect of expansion is overwhelmed by gravity).
Dark Matter is the name given to the unknown cause of more mass in galaxies than has been observed.
By 'observed' - the estimates as to the amount of matter in a given galaxy by the visible light and probable amount of planets.

The only similarity is that both contain the word, "dark" since the cause is unknown at this time.