All the evidence we have for dark matter | A century's worth of science history
Dr. Becky・2 minutes read
Lord Kelvin proposed dark matter in 1884 due to mass discrepancies in stars, leading to further discoveries like galaxies beyond the Milky Way. Various studies and experiments, such as the Bullet Cluster discovery in 2004, continue to provide evidence for dark matter, revealing its significance in understanding the universe's mass balance.
Insights
- Lord Kelvin's 1884 proposal of dark matter stemmed from discrepancies in star mass calculations, with Kwang Clare later coining the term "dark matter," sparking a shift towards studying individual galaxies' mass-to-light ratios.
- Vera Rubin and Ford's 1970 research on Andromeda's rotation curve, alongside Freeman's optical and radio curve analysis, solidified the concept of dark matter with a flat mass-to-light ratio, setting the stage for further discoveries like gravitational lensing and the Bullet Cluster, highlighting dark matter's elusive nature and ongoing research endeavors.
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Recent questions
What is dark matter?
Unknown substance in the universe, not visible directly.
Who discovered the concept of dark matter?
Lord Kelvin and Fritz Zwicky made significant contributions.
How did astronomers study dark matter in galaxies?
By analyzing rotation curves and mass-to-light ratios.
What alternative theory to dark matter was proposed?
Modified Newtonian Dynamics (MOND) by Milgram in 1983.
How was the presence of dark matter confirmed?
Direct proof from the Bullet Cluster collision in 2004.
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Summary
00:00
Unveiling Dark Matter: A Historical Journey
- Dr. Becky's audiobook is sponsored by Audible, with a free 30-day trial available.
- Lord Kelvin in 1884 first proposed the concept of dark matter due to discrepancies in mass calculations of stars in the Milky Way.
- French astronomer Kwang Clare referred to this missing matter as "Messier obstacle II," later leading to the term "dark matter."
- Astronomers in the 1920s discovered galaxies beyond the Milky Way, prompting a shift in focus to studying individual galaxies and their mass-to-light ratios.
- Fritz Zwicky in 1933 found a mass-to-light ratio of 400 times more mass than visible in the Coma Cluster, suggesting the presence of dark matter.
- Babcock's 1939 thesis on the rotation curve of the Andromeda galaxy revealed an unexpected increase in rotation speed with radius, indicating more mass on the outskirts.
- Post-World War II, galaxy and cluster surveys thrived due to repurposed military technology, aiding in the study of dark matter.
- In 1970, Vera Rubin and Ford's research on Andromeda's rotation curve showed a flat mass-to-light ratio, a key discovery in dark matter research.
- Freeman's 1970 contribution combined optical and radio rotation curves, suggesting that the mass of dark matter in galaxies is at least equal to visible mass.
- Discoveries like the first quasar in 1963 and the Cosmic Microwave Background in 1974 further contributed to understanding the universe's mass balance and the significance of dark matter.
15:09
Unraveling the Mystery of Dark Matter
- In 1974, two papers by Striker, Peebles, and others, and by Snow, Kazakh, addressed the issues of flat rotation curves in galaxies like Andromeda and the missing matter in clusters, proposing a mass-to-light ratio of 10 to explain the discrepancies.
- The discovery of twin quasars in 1979 by Walsh, Carswell, and Wayman, led to the theory of gravitational lensing, where a galaxy's gravity could bend light, creating multiple images of the same object.
- Faber and Gallagher's 1979 review article consolidated the evidence for missing matter in galaxies and clusters, gaining wider acceptance for the concept of dark matter outside the astronomy field.
- In 1983, Milgram proposed Modified Newtonian Dynamics (MOND) as an alternative to dark matter, suggesting a reevaluation of gravity laws to explain observed phenomena.
- Chakraborty's 1985 discovery of the Einstein cross, four identical quasars, supported the gravitational lensing theory, leading to further research on lens galaxies in clusters.
- The 1990s saw increased evidence for dark matter, with the Cosmic Microwave Background revealing variations indicating the presence of unseen matter, prompting the search for dark stars like black holes and neutron stars.
- The MACHO and EROS collaborations in 1993 detected gravitational lensing events, suggesting the presence of dark matter, with estimates ranging from 8% to 50% of the missing matter in the Milky Way.
- The 2004 discovery of the Bullet Cluster provided the first direct proof of dark matter, showing that the majority of mass in the collision of galaxy clusters was dark matter, distinct from normal baryonic matter.
- Ongoing research into dark matter focuses on detecting its particles through collisions with normal matter or creating them in particle accelerators, as the nature of dark matter remains one of the biggest unsolved problems in physics.
