DARK ENERGY

When Einstein completed his Theory of General Relativity, he added an extra parameter, Λ, which he called the cosmological constant. Einstein assumed that the universe was static, not expanding or contracting, so added this constant to fix his theory and offset gravity’s inward pull on matter. As we now know, Einstein was mistaken; the universe is actually expanding, not contracting. At the time, he regarded this addition to his theory as a huge blunder. The cosmological constant is often referred to as a “fudge factor” that allowed Einstein to essentially warp his theory to reflect what he believed at the time. This constant is actually useful as a way of expressing the effects of dark energy, however. Einstein used it to offset the contraction of the universe due to gravity in his theories of relativity, so we can think of the cosmological constant as a quantitative way of expressing the effects of dark energy. This idea, that dark energy is a constant throughout the cosmos, that the volume of space has intrinsic negative energy density causing its expansion, is the most simple (and perhaps most elegant) explanation of why the universe is expanding.

 

So what gives empty space its negative energy density, then? If this theory states that vacuum energy = dark energy, what’s vacuum energy? The current theory is that pairs of particles with opposite charges actually blink into existence and almost immediately cancel each other out, or annihilate. This is thought to happen so fast that it can’t even be observed. The result from this annihilation is a release of energy that can force space to expand. In theory, this agrees perfectly with all of the information in my first two moves. The effects of vacuum energy have been observed and verified through multiple methods, and these annihilating particles alone simply shouldn’t contribute enough energy to constitute all of the dark energy that’s expanding our universe. In fact, these values should differ by a magnitude of about 10100 -- that’s 1 followed by 100 zeros. This discrepancy is referred to as the Vacuum Catastrophe.

This massive discrepancy can be explained in a number of ways. One possibility is that this theory is entirely wrong and vacuum energy doesn’t contribute to the expansion of the universe at all. It’s also possible that it contributes to a small fraction of the dark energy’s force. Another possibility is simply that the calculations of force due to annihilating particles were incorrect or that dark energy itself hasn’t been correctly measured.