What is dark matter and dark energy?
Dark matter and dark energy are two unknown things. Dark matter is a substance in the universe that keeps things together by using its mass to bend spacetime, hence creating gravity to keep things like galaxies together. Dark energy, however, is the exact opposite of dark matter. It is an unknown substance which pushes things away from each other. These forces have been in existence since the beginning of our universe and they engage in a cosmic dance that determines the fate of our universe.
The story of dark matter
Dark matter was the first of the two to be discovered. One day in the 1970s, at the Kitt Peak National Observatory located 56 mi (90 km) southwest of Tucson, Arizona, an astronomer named Vera Rubin was making some observations on Andromeda to check astronomers assumptions about the orbital speeds of stars, she found something out that was very strange: the outer edges of the galaxy were spinning extremely fast. In fact, they were spinning so fast that they should've flown out into space. However, they weren't. Hence, Rubin analyzed the observation, repeated the same process with other galaxies, and published her findings. The final result was that there was some invisible mass in the galaxies that kept the outer edges from not flying out into space.
Rubin's observations of the Andromeda Galaxy became the first observational evidence of dark matter.
The term "dark matter", however, was coined before Rubin's observations. An astronomer in the 1930s by the name of Fritz Zwicky coined the term as an explanation for some "unseen mass" in his observations. However, his idea of dark energy was shunned by the astronomical community until Rubin, whose astronomical observations were solid evidence of the existence of dark matter. When they thought they did it all, the universe held another surprise for them: dark energy.
The story of dark energy
Dark energy finds its roots in Einstein's theory of general relativity. In his early years, Einstein agreed with the common worldview at that time that the universe was a static stage. However, when he was developing his theory of general relativity, which I cover in my article "Einstein's 5 Theories", he ran into a problem: how could the universe be a static stage when gravity was pulling everything together? To fix this, he made something called the Cosmological Constant. The idea of the Cosmological Constant is that the empty space between celestial objects exerts a force that pushes celestial objects apart, and hence, gravity is neutralized, keeping the universe static. However, Edwin Hubble discovered that the universe was dynamic, expanding, and not static, so Einstein's Cosmological Constant went extinct, and it was called by Einstein himself as his "biggest blunder". However, it wouldn't be completely extinct. In 1988, two teams that were both investigating supernovas came to a very surprising conclusion at the time: the universe was expanding faster than ever. After confirming that the results were accurate, they reported their results to the public. All of a sudden, Einstein's cosmological constant, which he ironically made for his static universe, became important for explaining the fact that the dynamic universe's expansion was getting faster and faster. In the same year it was discovered, dark energy got its name changed from the cosmological constant to dark energy by a guy named Michael Turner.
Bibliography
If you are interested in learning more and/or want to know where I got my info, check out these links!
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