Atlas Faust, MD
Dark Matter and Dark Energy
These are two words you often hear thrown around and more often that not I come across people who don’t know precisely what they are or even that they are two quite different things. So here we go.
When you take a look at a galaxy you see a certain characteristic known as gravitational lensing where light is warped in a certain way by mass. From this you can deduce an estimate of the mass of the galaxy. However when we compare this to the mass we estimated based on the concentration, size and distribution of visible mass within the galaxy we find the two numbers to be at odds and not only this but the greatest curving of space time is found in the spaces between objects where nothing can be seen. The difference in masses is believed to be caused by the elusive dark matter, so called because it warps spacetime like regular matter but is completely invisible (hence the dark). All in all dark matter constitutes 23% of the mass-energy density of the universe and a worrying 83% of the total amount of matter. The universe is made chiefly of stuff you cannot see.
Dark energy is also the answer to a problem, behaving somewhat like the x value in an algebraic equation we’re forced to solve. The problem lays in the fact that the universe is continuing to expand at an ever increasing rate and we have no idea why. When you think about it it really doesn’t make any sense, you would expect the universe’s expansion to slow down or at least stay constant but unfortunately this isn’t the case. Thus we call this mysterious energy that is causing the increasing the rate at which the universe expands “dark energy”.
We really know so very little.