As fascinating as it is mysterious,
dark matter plays a huge role in the operation of our universe. Even within our
own galaxy, we can detect hints of its behavior and can see its effects, even
if we can’t see the matter itself.
One of the most important
signifiers of the presence of dark matter in the Milky Way is rotation curve. This
concept has a rich history beginning in the early 1930s with a number of
crucial discoveries. Jan Hendrik Oort made one of the first realizations on the
nature of mass distribution in our galaxies, and theorized that the outermost
objects in our galaxy should orbit much slower than those closest to the
center. In theory, he should have been correct, but he was missing a key
component to the universe’s composition. Fritz Zwicky continued these studies
of mass and discovered something fascinating. “To his surprise, the mass of the
cluster based on the speed of its galaxies was about ten times more than the
mass of the cluster based on its total light output.” He named this missing
mass “dark matter,” and became one of the first to coin the phrase.
Rotation curve works as such: In
our Solar System, the velocity of the planets’ orbits in our Solar System
decreases the farther they are from the Sun, as described by Kepler’s third law.
However, this does not apply on the grand scale of our galaxy. The farthest
stars are orbiting at roughly the same speed as nearer stars are. This can only
be explained by an unknown, and very large, amount of mass that overcompensates
for the length of the radius of the orbit; namely, dark matter.
Trusting in dark matter is a
question of faith. While we can feel its effects, we will never truly know it
exists until we see it for ourselves.
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Naming it "dark matter" gives us a little leeway into how we classify what it is. Calling it "dark" let's us cheat a little bit just by saying "we don't know what it is, but it's there" if we can witness its effects, it must exist, but calling it "dark" let's us mean it could be anything so technically we're not wrong when we say dark matter exists. Maybe it's a bit more concrete to know what exactly the matter is like, but it's still correct to say "something we don't know exists, exists".
ReplyDeleteMitch Joa
Dark matter and energy are one of the mysteries of the universe. The effects of these phenomena are apparent it their gravitational effects on the universe but they cannot be seen. I wonder what observations Oort made to consider that there might be something unseen in the universe.
ReplyDeleteMany unanswerable questions in science have been solved, and like the discovery of the higgs boson, I am sure we will find dark matter. The fact that dark matter fits into our models of the universe is also encouraging, but one would think that a capacity for incredible space travel would be necessary for interaction with the substance. It's not as though we can use a particle accelerator to create the material.
ReplyDeleteWe have to remember that we know absolutely nothing about dark matter, and that it is only an explanation for the gravitational effects that we observe. It is also a possibility that our understanding of gravity thus far has been incorrect. Dark matter is only a sort of arbitrary placeholder in that respect. Only after we actually discover the composition (or, existence) of dark matter will we know for sure that our understanding of a galaxy's gravity is correct. Until then, dark matter is only a name for something that scientists do not even know exists or not.
ReplyDeleteInteresting and succinct description of the discovery and meaning of dark matter. It's fascinating that Kepler's law does not apply on the grander scale of the whole galaxy as opposed to our Solar System. The "missing mass" that we can't quite figure out explains this. It is amazing that Zwicky figured out that there was mass that is unaccounted for in the galaxy.
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