Physics in the Dark: Searching for Missing Matter
World Science Festival・73 minutes read
Einstein's confirmation of the general theory of relativity through Eclipse observations 100 years ago led to the proposal of dark matter by scientists, with various theories and experiments exploring its existence and impact on the universe. The presence of dark energy and dark matter, interconnected forces dominating the universe, continues to be a focus of scientific exploration, with ongoing experiments and advancements aiming to uncover more insights into these mysterious phenomena.
Insights
- Einstein's general theory of relativity was confirmed through Eclipse observations 100 years ago, marking a significant event in scientific history.
- Dark matter, proposed due to gravitational observations, is inferred from unseen structures analogous to flying into a city at night based on visible lights.
- The interconnectedness of dark energy and dark matter, with dark energy dominating the universe's energy and dark matter keeping galaxies together, presents a complex yet intertwined relationship crucial for understanding the cosmos.
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Recent questions
What is dark matter?
Unknown matter affecting galaxies' motions.
How do scientists study dark matter?
Through gravitational observations and indirect evidence.
What is the relationship between dark matter and dark energy?
Dark matter provides gravitational force, while dark energy accelerates expansion.
What are some proposed candidates for dark matter?
WIMPs, axions, and primordial black holes.
How do dark matter and dark energy impact the universe?
Dark matter shapes cosmic structures, while dark energy accelerates expansion.
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Summary
00:00
"Unseen Dark Matter: Einstein's Eclipse Confirmation"
- The event being celebrated is the confirmation of Einstein's general theory of relativity through Eclipse observations 100 years ago.
- A program on PBS is recommended for further information on the topic.
- Scientists propose the existence of unseen dark matter in the universe due to gravitational observations.
- Analogy of flying into a city at night is used to explain the inference of unseen structures based on visible lights.
- Historical background on the concept of dark matter dating back to the late 1800s is provided.
- Scientists like Lord Kelvin and Henri Poincaré contributed to the early understanding of dark matter.
- Fritz Zwicky and Vera Rubin's work on galaxy motion supported the existence of dark matter.
- Vera Rubin's observations of galaxy stars' motion indicated the presence of unseen dark matter.
- Mathematical analysis showed dark matter's significant mass compared to visible matter in the universe.
- Discussion with experts on dark matter theories and alternative explanations for unexplained motions in the universe.
17:03
"Dark Matter: From Ordinary to Exotic"
- Dark matter was once ordinary matter in the first minutes of the Big Bang, now a Dark Star participating in thermonuclear reactions to create helium, a prediction of The Big Bang Theory.
- The amount of baryonic stellar stuff is a small fraction, leading to the consideration of more exotic things like black holes formed early in the universe.
- Black holes are ideal dark candidates as they are invisible and can affect light transmission from stars, deflecting light as they pass by.
- Indirectly inferring the number of dark stars involves observing light deflection from stars in nearby galaxies, setting limits on the possibilities of dark stars.
- The possibility of tiny black holes, the size of asteroids, being a significant portion of dark matter is intriguing.
- Observations of the Andromeda galaxy suggest the presence of primordial black holes, potentially asteroid mass, supporting the hypothesis of dark matter being black holes.
- Supersymmetry theory predicts the existence of lightest particles as dark matter candidates, based on equal numbers of particle partners in the early universe.
- Neutrinos are considered as dark matter candidates due to their neutral and weakly interacting characteristics, but their abundance is too small to account for all dark matter.
- The introduction of supersymmetry in particle physics aims to explain the Higgs particle and the mass it holds, enhancing the standard model's coherence.
- Calculations based on dark matter particle interactions with regular matter in the early universe predict the amount of dark matter remaining today, aligning with the observed dark matter quantity.
32:26
Galaxy Annihilation: Dark Matter and Gamma Rays
- The annihilation process in galaxies involves searching for excess light in areas with dark matter.
- Gamma rays, highly energetic photons, are produced in nuclear explosions and can be observed in space.
- Dark matter annihilation could produce gamma rays in the Milky Way's center, indicating the presence of WIMP dark matter.
- Observations of dwarf galaxies, rich in dark matter, are being conducted to detect gamma rays.
- The Fermi satellite observed excess gamma rays in the Milky Way's center, possibly from dark matter annihilation.
- Simulations using dark matter predict early universe fluctuations and galaxy formation.
- The Sloan Digital Sky Survey maps galaxies, showing the impact of dark matter on galaxy shapes.
- The Dark Energy Survey's mass map reveals the distribution of mass in the universe six billion years ago.
- Different types of dark matter particles, like cold and warm dark matter, make distinct predictions for galaxy formation.
- The discovery of numerous dwarf galaxies implies the universe may not be mostly warm dark matter, but possibly a mix of dark matter types.
47:25
"Exploring Dark Sector Models Beyond WIMPs"
- Dark Sector models propose the existence of dark worlds and entities beyond the known standard model.
- Current dark matter candidates do not create dark worlds or beings.
- Dark Sector models are gaining attention due to their unique predictions, differing from traditional wimps.
- Experimental focus is shifting towards exploring various possibilities beyond wimps.
- Experiments targeting Dark Matter particles are being conducted deep underground using xenon or argon.
- Signals reported in literature regarding Dark Matter have not been widely accepted.
- Repetition of experiments by separate groups is crucial for confirming results.
- Lighter Dark Matter particles pose challenges in detection due to minimal impact on targets.
- Indirect evidence supports the existence of Dark Matter, but direct searches remain inconclusive.
- Alternative approaches are being explored as traditional candidates like supersymmetry face challenges.
01:02:15
Unveiling Dark Energy and Matter in Universe
- Dark energy in the universe causes objects to move away and accelerate, leading to a point where things move at the speed of light, creating a horizon where objects become invisible.
- The expansion rate of the universe, determined by the Hubble constant, is linked to the presence of dark energy and sets the universe's size and horizon location.
- Dark energy introduces entropy and temperature to the universe, following the laws of thermodynamics, with its origin traced back to quantum effects.
- Dark energy, a constant in scientific equations, was theorized by La Mettrie and later discovered, dominating the universe's energy and causing acceleration.
- Dark energy accounts for over 70% of the universe's energy, with ordinary matter making up only 5%, where most interesting phenomena occur.
- Dark energy and dark matter are interconnected, with dark matter acting as an additional gravitational force keeping galaxies together.
- The presence of dark energy affects the rotation curves of galaxies, with interactions between dark energy and matter creating the additional force.
- Simulations show that understanding gravity better could explain the gravitational effects attributed to dark matter without invoking its particle nature.
- The search for dark matter particles continues, with experiments and theories exploring various possibilities, including the existence of wimps and axions.
- Future advancements in technology, such as larger telescopes and accelerators, aim to provide more insights into dark matter, with China's involvement in scientific endeavors shaping the field's future.
01:18:11
"Unifying Theory and Observation in Science"
- Science progresses through hypotheses, experiments, and evidence evaluation, with the process taking time and effort to confirm or reject ideas.
- String theorists are exploring ways to connect their theoretical work, like supersymmetry and extra dimensions, with observable phenomena in cosmology, aiming to develop a more comprehensive understanding of the universe.
- Emphasizing the importance of combining theoretical frameworks with observational data, the speaker advocates for continued exploration of dark matter and other possibilities to refine our understanding of the universe, suggesting that progress lies in integrating theory and observation.
