Dark matter is one of the greatest mysteries in modern physics. It is a form of matter that cannot be seen directly, but its existence is inferred from its gravitational effects on visible matter and background radiation in the universe.
Most scientists believe that dark matter is composed of non-baryonic matter, meaning it is not made up of the same fundamental particles that make up normal, "baryonic" matter like protons and neutrons. The leading candidate for dark matter is a hypothetical particle called a WIMP (Weakly Interacting Massive Particle), which is believed to have 10 to 100 times the mass of a proton, but interacts only very weakly with normal matter.
Despite making up about 85% of the total matter in the universe, dark matter remains elusive. Scientists have gathered various clues and observations over the past century that provide convincing evidence for its existence, but its true nature is still unknown.
Evidence for Dark Matter
One of the earliest pieces of evidence for dark matter came in the 1930s, when Swiss astrophysicist Fritz Zwicky studied the Coma Cluster of galaxies. By applying the theorem of classical mechanics, he estimated the total mass of the cluster based on the motions of its galaxies, and found that there was far more mass present than could be accounted for by the visible galaxies alone. This "missing mass" was the first hint of the dark matter problem.
More modern evidence for dark matter comes from observations of gravitational lensing - the bending of light by the gravitational field of massive objects. Astronomers have observed distorted "Einstein rings" and other lensing effects around galaxies and galaxy clusters, indicating the presence of large amounts of unseen mass.
Measurements of the cosmic microwave background radiation, a relic of the Big Bang, have also provided crucial evidence. Slight irregularities in the distribution of this radiation reveal the underlying structure of dark matter in the early universe, which has guided the formation of galaxies and galaxy clusters we see today.
The Search for Dark Matter
Despite this overwhelming indirect evidence, dark matter remains one of the biggest unsolved problems in physics. Physicists have proposed many hypotheses about its nature, from WIMPs to even more exotic particles like tachyons. But so far, all attempts to directly detect dark matter particles have come up empty.
The hunt for dark matter continues, with experiments like the Large Underground Xenon (LUX) detector and the IceCube Neutrino Observatory searching for potential dark matter interactions. Upcoming space missions like the European Space Agency's Euclid telescope are also expected to shed new light on the mysterious substance that makes up the majority of our universe.
In the meantime, dark matter provides an exciting opportunity for physics education. Its mysterious nature and the ongoing scientific quest to uncover its secrets can captivate students and illustrate the dynamic, evolving nature of scientific knowledge. By exploring dark matter, students can gain a deeper appreciation for the power of indirect evidence, the role of competing theories, and the collaborative nature of modern physics research.
Fun facts
If dark matter particles were the size of grains of sand, there would be enough of them passing through your body every second to fill a swimming pool
Astronomers estimate that if all the dark matter in the observable universe was compressed into a single object, it would be only about 1 meter in diameter
The total mass of dark matter in the Milky Way galaxy is estimated to be 6 times greater than the mass of all the stars, planets, gas, and dust in the galaxy combined
Works Cited
Feldman, A. (2024). Dark Matter Could Be Gently Wobbling space-time around Us — and Scientists May Finally Know How to Detect It. [online] LiveScience. Available at: https://www.livescience.com/space/cosmology/dark-matter-could-be-gently-wobbling-space-time-around-us-and-scientists-may-finally-know-how-to-detect-it.
Ravisetti, M. (2023). We Still don’t Know What Dark Matter is, but here’s What it’s Not. [online] Space.com. Available at: https://www.space.com/dark-matter-detector-tights-limits-inelastic-collisions.
Tillman, N. (2017). What Is Dark Matter? [online] Space.com. Available at: https://www.space.com/20930-dark-matter.html.
Woithe, J. and Kersting, M. (2020). Bent It like Dark Matter! [online] CERN. Available at: https://cds.cern.ch/record/2753018/files/2010.14826.pdf.
Hozzászólások