Whats the difference between dark matter and dark energy?
I’ve been reading many clever answers here about dark matter and dark energy that called my attention to this question. 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? The short answer to your question is that we don’t know if dark matter and dark energy are manifestations of the same dark “thing”. We know they both must exist to explain certain phenomena, but we still know very little about their make up so we cannot assume they are linked. For now, we think of them as separate, and we believe the cosmos to be composed of roughly 0.03% heavy elements (anything other than hydrogen and helium), 0.3% neutrinos, 0.5% stars, 4% free hydrogen and helium, 25% dark matter, and 70% dark energy. Here is how we define them separately: Dark matter must exist to account for the gravity that holds galaxies together.
