When we look out into the universe, we can see all kinds of matter like atoms stars, planets, galaxies, and us. But what we can’t see is the vast majority of the matter and energy that make up the universe. Two mysterious substances, dark matter, and dark energy, both of which are invisible, make up as much as 95% of the universe. In this article, we’ll explore what we know about dark matter and dark energy and how scientists are trying to understand these mysterious forces.
What is Dark Matter?
Dark matter is a hypothetical substance that scientists believe makes up about 27% of the universe. It is called “dark” because it does not emit, absorb, or reflect any electromagnetic radiation, making it invisible to telescopes. However, scientists have been able to infer the existence of dark matter by observing its gravitational effects on visible matter.
One of the ways scientists infer the existence of dark matter is through the study of galaxy rotation curves. A galaxy’s rotation curve is a graph that shows how the speed of stars in a galaxy changes with distance from the center of the galaxy. Scientists have found that stars on the outer edges of a galaxy rotate at the same speed as stars closer to the center, which is unexpected if the only visible matter in the galaxy is causing the gravitational pull. The only explanation for this is that there is a large amount of invisible matter, or dark matter, in the galaxy that is causing the gravitational pull.
Another way scientists infer the existence of dark matter is through the study of galaxy clusters. A galaxy cluster is a group of galaxies that are held together by gravity. Scientists have found that the visible matter in a galaxy cluster is not enough to account for the gravitational pull keeping the cluster together. Again, the only explanation for this is that there is a large amount of invisible matter, or dark matter, in the cluster.
What is Dark Energy?
Dark energy is a hypothetical substance that scientists believe makes up about 68% of the universe. Because it does not emit, absorb, or reflect any electromagnetic radiation, scientists call it “dark” and it makes it invisible to telescopes. However, scientists have been able to infer the existence of dark energy by observing its effects on the expansion of the universe.
One of the ways scientists infer the existence of dark energy is through the study of Type Ia supernovae. A Type Ia supernova is a type of supernova that occurs when a WHITE DRAWF STAR in a binary system accretes matter from its companion star until it reaches a critical mass and explodes. Scientists have found that Type Ia supernovae that are farther away appear dimmer than expected. The only explanation for this is that dark energy causes the acceleration of the expansion of the universe.
Another way scientists infer the existence of dark energy is through the study of cosmic microwave background radiation. The cosmic microwave background radiation is the afterglow of the Big Bang, and it provides a snapshot of the universe when it was just 380,000 years old. Scientists have found that the universe is not only expanding, but it is also accelerating in its expansion. Again, the only explanation for this is that there is a large amount of dark energy in the universe.
Conclusion
Dark matter and dark energy are two mysterious substances that make up the majority of the universe, yet we know very little about them. Scientists continue to study these invisible forces through the observation of their effects on visible matter and the expansion of the universe. The study of dark matter and dark energy is ongoing and will likely lead to many new discoveries and a better understanding of the universe.