The Mystery of Dark Matter physics 40S

Introduction to Dark Matter

• Video by Perimeter Institute for Theoretical Physics

• Presented by Damian Pope, featuring leading researchers

• Focus on the complexities of the universe and dark matter

Vera Rubin's Observations (1967)

• Studied stars in Andromeda Galaxy, finding unexpected stellar speeds

• Stars maintain constant speeds regardless of distance from the center

• Led to a rethinking of the universe's composition

Measuring Mass in Astronomy

Orbital Method

• Example: Calculating the Sun's mass using Jupiter's orbit

• Jupiter's speed: 13 km/s, radius: 780 million km

• Newton's Second Law relates mass to gravitational force and acceleration

• The Sun's mass is approximately 1,000 times that of Jupiter and 300,000 times that of Earth

Mass of Galaxies

• Similar methods apply to galaxies, typically containing around 100 billion stars

• Use orbital speeds and radii of stars to estimate galaxy masses

Doppler Effect

• The shift in frequency of sound or light due to the movement of the source

• Used to measure star speeds by analyzing light frequency shifts

• Brightness method utilized for estimating galaxy mass

Case Study: Triangulum Galaxy

• Calculated mass of Triangulum using orbital and brightness methods

• Orbital method: mass = 46 billion Suns

• Brightness method: mass = 7 billion Suns

• Significant discrepancy indicates the presence of unseen mass

Dark Matter

• Most of the mass in galaxies is unseen and does not emit light

• Dark matter explains higher-than-expected stellar speeds

• Gravitational lensing reveals dark matter through light distortion

Evidence for Dark Matter

1. Orbital speeds of stars in galaxies

2. Gravitational lensing of light from distant galaxies

3. Continuity in observed phenomena correlating with dark matter's influence

Composition of Dark Matter

• Possibilities include:

  • Undetectable planets: Unlikely due to insufficient mass

  • Brown dwarf stars: May play a role but likely not the majority

  • Black holes: Considered possible but may not account for most dark matter

• Majority of dark matter is theorized to consist of new particles, such as WIMPs (Weakly Interacting Massive Particles)

Current Research and Experiments

• Ongoing worldwide experiments to detect dark matter particles

• SNOLAB in Ontario is one of many locations designed to filter cosmic noise

• Various detection techniques being developed, including super-heated liquids

Conclusion

• The search for dark matter continues, promising new insights into the universe

• Vera Rubin's legacy highlights the pursuit of knowledge in understanding the cosmos

• "The sky will not be the limit"—the mystery of dark matter remains to be solved.