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Your Daily Equation | Live Q&A with Brian Greene

World Science Festival・141 minutes read

The concept of black holes evolving over time and information paradoxes are explored in a live discussion on quantum mechanics and unified theories, alongside revelations about the monogamy of entanglement theory. The significance of fundamental makeup of space and time, parallel universes, and theoretical physics discoveries, including Hawking's radiation and supersymmetric particles, are highlighted in the discussion.

Insights

  • Stephen Hawking's discovery of black hole radiation led to the idea of black hole evaporation, challenging previous beliefs about their permanence.
  • The twin paradox in relativity highlights how time dilation can lead to significant age differences between travelers, emphasizing the impact of relative motion on time.
  • Quantum entanglement theory suggests that entangled particles across a black hole's horizon could create a firewall, potentially erasing the inside of a black hole.
  • The potential existence of parallel universes and the debate surrounding NASA's claim of evidence for a reverse-time parallel universe highlight the speculative nature of such theories.
  • The fusion of quantum mechanics and general relativity is essential to understanding phenomena like black holes and the Big Bang, emphasizing the need for unified theories in physics.

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Recent questions

  • What is the monogamy of entanglement theory?

    The monogamy of entanglement theory suggests that entanglement across a black hole's horizon could lead to a firewall, potentially erasing the inside of a black hole. This theory questions the distribution of entanglement between particles and the implications it has on the structure and information within a black hole.

  • How does quantum entanglement affect data transport?

    Quantum entanglement cannot be used to transport data faster than the speed of light due to the need for a slower-than-light process to compare results. This limitation arises from the fundamental principles of quantum mechanics, where entangled particles exhibit instantaneous correlations but cannot be exploited for faster-than-light communication.

  • What is the significance of the twin paradox in relativity?

    The twin paradox in relativity states that a twin traveling in a rocket ship will age slower than the twin on Earth due to time dilation effects. This paradox highlights the asymmetry in aging experienced by individuals in different reference frames due to the effects of special relativity, where relative motion influences the passage of time.

  • How are gravitons theorized to mediate gravity?

    Gravitons are theorized to mediate gravity by acting as messenger particles that transmit gravitational forces between masses. This theoretical particle plays a crucial role in the quantum description of gravity, where interactions between masses are mediated by the exchange of gravitons, similar to other force-carrying particles in quantum field theory.

  • What is the concept of the Planck mass?

    The Planck mass is 10^19 GeV, which is 10 billion billion times the mass per proton, creating an unexplored mass range between ten thousand and ten billion billion times the mass per proton. This fundamental mass scale arises from the Planck units and represents the energy scale at which quantum gravitational effects become significant, providing insights into the physics at extremely high energies.

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Summary

00:00

"Exploring Quantum Mechanics, Relativity, Unified Theories"

  • The live discussion Q&A on quantum mechanics, relativity, and unified theories starts at 3 p.m. on Fridays.
  • Stephen Hawking's discovery that black holes radiate thermal radiation led to the idea that black holes can evaporate over time.
  • The information paradox of black holes questions whether information that falls into a black hole can come back out.
  • Initially, Stephen Hawking believed information was lost in black holes, but later changed his stance.
  • The monogamy of entanglement theory suggests that entanglement across a black hole's horizon could lead to a firewall, potentially erasing the inside of a black hole.
  • The language of wavelengths and frequencies is used for electrons and quarks in quantum mechanics, similar to photons.
  • Quantum entanglement cannot be used to transport data faster than the speed of light due to the need for a slower-than-light process to compare results.
  • Gravitons are theorized to mediate gravity by acting as messenger particles that transmit gravitational forces between masses.
  • The concept of adding up all natural numbers to get -1/12 involves regulating divergent sums using the Riemann zeta function.
  • The twin paradox in relativity states that a twin traveling in a rocket ship will age slower than the twin on Earth due to time dilation effects.

17:01

Twin paradox, parallel universes, and supersymmetry explained.

  • Earth and its twin experience relative motions, leading to an asymmetry in their ages upon rejoining.
  • Only one twin undergoes acceleration during the journey, causing a break in symmetry.
  • Detailed explanation of the twin paradox can be found on worldscienceu.com in a special relativity course.
  • Visual and mathematical explanations of the twin paradox are provided in the course.
  • The next major discovery in theoretical physics may involve understanding the fundamental makeup of space and time.
  • Parallel universes are a real possibility, with various theories suggesting their existence.
  • NASA's claim of evidence for a parallel universe with time elapsing in reverse is overblown and lacks substantial support.
  • The slowing of time due to gravity is explained as objects moving towards regions where time elapses more slowly.
  • The mass of supersymmetric particles is unknown, making it challenging to determine the size of a collider needed to prove their existence.
  • The Large Hadron Collider in Geneva can probe up to 10 TeV, but the masses of supersymmetric particles remain uncertain.

34:03

Unveiling Mysteries: From Planck Mass to Quantum Probabilities

  • The Planck mass is 10^19 GeV, which is 10 billion billion times the mass per proton, creating an unexplored mass range between ten thousand and ten billion billion times the mass per proton.
  • China may construct a machine to explore this mass range to detect or rule out supersymmetric particles, but the required size of the machine remains uncertain.
  • The Ricci tensor differs from the Riemann curvature tensor by providing information about the curvature of cross-sectional slices of space determined by the remaining indices on the tensor.
  • The universe's matter-antimatter asymmetry raises questions about why there is more matter than antimatter, with theories suggesting either a dynamic generation of asymmetry or a sequestering of matter from antimatter.
  • Bertrand Russell's perspective suggests that the universe lacks grand design or overarching purpose, with the laws of physics acting on matter without an intelligent design.
  • Hawking radiation, proposed by Stephen Hawking in 1974, describes particles erupting from the edge of a black hole due to quantum fluctuations, resulting in radiation emitted as the black hole decreases in size.
  • Earth's elliptical orbit and rotational motion cause slight accelerations, but these changes are minimal compared to the intrinsic pull of Earth's gravity, which we constantly feel.
  • The Big Bang could potentially be a phase transition, akin to real-world phase transitions like ice melting into water, where a change in the value of a field triggers an inflationary expansion.
  • A photon fired directly into a black hole does not exceed the speed of light beyond the event horizon, as the speed of light remains constant in local measurements according to the general theory of relativity.
  • Quantum mechanics only predicts probabilities of future events, not definite outcomes, suggesting an openness in the future rather than a predetermined exact future from the beginning of spacetime.

52:41

Quantum mechanics and the expanding universe

  • Quantum mathematics are determined by Schrodinger's equation, which has a deterministic aspect similar to Newtonian physics.
  • In quantum mechanics, outcomes are determined by probabilities, not certainties, unlike in Newtonian physics.
  • Probabilities for particle movements or interactions were set at the Big Bang, but they don't dictate actual behaviors.
  • Your future is probabilistic, with various possible futures determined by quantum mechanics.
  • The universe's expansion isn't into pre-existing space; it creates new space as it expands.
  • Leonard Susskind and Juan Maldacena proposed EPR equals ER theory, linking quantum entanglement and wormholes.
  • Galaxies moving apart signifies the universe's expansion, not a static space with an explosion.
  • Galaxies don't expand due to gravity overpowering space's repulsive force.
  • In the future, if dark energy strengthens, galaxies could expand as repulsive gravity overcomes attractive forces.
  • Reversing velocities doesn't reverse time; it allows physical processes to unfold in an unusual order.

01:11:47

Debating free will, God, and physics.

  • The Hamiltonian operator in quantum mechanics is represented by an operator involving differential equations acting on a wave function.
  • The concept of free will is discussed in relation to personal choices, such as being a vegan or vegetarian, with the speaker expressing skepticism about the existence of true free will.
  • The speaker questions the idea of free will, using the example of asking his wife to marry him, attributing choices to particle motions in the brain rather than personal agency.
  • The existence of God is debated, with the speaker acknowledging the diversity of beliefs and questioning the validity of all religions.
  • The speaker affirms his love for his wife but denies having true freedom in that love, attributing emotions and reactions to particle motions beyond personal control.
  • Freeman Dyson's theory that gravitons may not exist and the challenges of unifying quantum mechanics and general relativity are discussed.
  • The speaker addresses the concept of gauge symmetry, admitting difficulty in explaining it in simple terms due to its complexity.
  • The expansion of the universe and the challenges of measuring gravitons are explored, with considerations of observable versus unobservable changes.
  • The speaker reflects on the necessity of blending quantum mechanics and general relativity in understanding phenomena like black holes and the Big Bang.
  • The speaker expresses fatigue after a lengthy discussion and hints at the limitations of his mental capacity to address complex topics.

01:29:37

"Gauge symmetry, inflation, dimensions in physics"

  • Gauge symmetry in equations of particle physics respects Li groups like su 3 + su 2 cross u 1.
  • Gauge symmetry involves transforming fields in a Lagrangian by a Li group, leaving it invariant or changing it by a total derivative.
  • Cosmic inflation flattens the universe by diluting spatial curvature through rapid expansion.
  • Inflation dilutes curvature, making the universe appear flat due to its enormous growth.
  • In the pre-inflationary Big Bang, curvature needed fine-tuning, but inflation dilutes it naturally.
  • Penrose diagrams are valuable mathematical tools for analyzing space-time structure globally.
  • Energy balance theory suggests positive energy balanced by negative gravitational potential energy yields zero total energy.
  • Curved space-time can be intrinsically understood without needing higher-dimensional embedding.
  • Accessing other dimensions may be possible through high-energy collisions at the Large Hadron Collider.
  • Evidence of accessing other dimensions could be seen in collisions where total energy decreases due to particles leaving our dimensions.

01:46:57

"Physics of Space, Time, and Consciousness"

  • Dr. Tyson explains that if Earth became a black hole, the moon would still orbit it due to the curvature of space-time depending on mass density.
  • Birkhoff's theorem states that the gravitational field outside a spherical body is solely dependent on its mass.
  • Humans possess a higher level of language sophistication compared to other animals, supported by studies analyzing information content in utterances.
  • Evolution by natural selection has uniquely advanced human communication and thinking abilities.
  • The inability to predict the exact time of radioactive decay for a single atom is due to the probabilistic nature of the Schrodinger equation.
  • Consciousness is primarily associated with brain function, with no evidence supporting a universal consciousness outside of physiological systems.
  • The progression from real to imaginary numbers led to the exploration of other number systems like the octonians, but their physical relevance remains uncertain.
  • Different topologies and differential structures in physics have been explored, but their significant impact on understanding the universe is yet to be demonstrated.
  • The speed of a particle through space-time is always equal to the speed of light, affecting the rate at which individuals age based on their motion through space and time.
  • Photons, moving at the speed of light, experience no passage of time, while individuals moving through space divert some motion through space-time into their spatial movement, affecting their aging process.

02:04:32

"Space-time, Dimensions, and Relativity: A Summary"

  • Motion through space-time is described as moving at the speed of light, with a shift to motion through space resulting in a slowdown in motion through time.
  • Captain Frantic's analogy of moving east to slow northward motion is likened to diverting motion through space-time into motion through space, leading to a slowdown in time.
  • The concept of motion through space-time is crucial, emphasizing the relationship between motion through space and time.
  • Describing higher dimensions mathematically involves adding new coordinates like X, Y, Z, W, and T to represent additional spatial dimensions and time.
  • Visualizing higher-dimensional shapes is challenging, with equations providing a means to analyze them despite the difficulty in picturing them.
  • Astronomers have not found stars older than the universe's age of 13.8 billion years, challenging the notion of such existence.
  • The acceptance of 10 or 11 dimensions in string theory is not universally embraced, with the choice of dimensions guided by mathematical equations rather than experimental proof.
  • The rate at which one ages at rest is likened to a maximum speed through time, slowing down when in motion relative to another observer.
  • Length contraction is linked to the relativity of simultaneity in special relativity, where discrepancies in events' timing lead to time dilation and subsequently, length contraction.
  • The logical coherence of special relativity's components, starting with the relativity of simultaneity, leads to a comprehensive understanding of phenomena like time dilation and length contraction.

02:20:50

Physics: Time, Space, Black Holes, Tachyons, Passion

  • To measure the length of a train, one can calculate it by timing the duration it takes for the train to pass by and multiplying that by its speed.
  • Time dilation in clocks leads to length contraction, resulting in a smaller measured length due to slower time.
  • The block universe concept, where past, present, and future coexist, is compatible with quantum mechanics, as both involve probabilistic outcomes.
  • The no-hair theorem states that black holes with the same mass, charge, and angular momentum are identical, lacking distinguishing qualities.
  • Combining all physics equations with general relativity leads to breakdowns and nonsensical results, motivating the development of theories like string theory.
  • While probabilities in quantum mechanics are predetermined by Schrodinger's equation, actual outcomes are not predetermined.
  • Tachyons, hypothetical particles traveling faster than light, challenge causality but are not widely believed to be real.
  • Open questions in physics include defining the nature of space and time, potentially built from finer ingredients like atoms of space or time.
  • Sacrifices in pursuing physics, such as long hours of study, are viewed as choices rather than regrets, driven by a passion for fundamental questions.
  • Solid-state physics, while not disliked, is less appealing than questions on the universe's origin or philosophical physics inquiries for some physicists.

02:37:22

Unraveling mysteries of physics and time

  • Large dimensions can be invisible to us due to light being unable to traverse their expanse.
  • The concept of time being a human construct is debated, with theories incorporating time being successful.
  • Atoms of time may exist in configurations where the notion of time is absent, leading to realms without time.
  • The observation of strings depends on string theory being correct and the size of the strings, with conventional strings being incredibly small.
  • Artificial intelligence developments may impact physics, potentially aiding in solving unsolved questions.
  • The speed of light is constant in a vacuum but can change in different mediums like water.
  • Quantum computing has theoretical and practical implications for advancing understanding in physics.
  • Ed Witten is highly regarded for his exceptional intelligence and insights in mathematics and physics.
  • The Big Bounce theory, proposing cyclical cosmology, is gaining traction with researchers like Paul Steinhardt.
  • Q&A sessions with colleagues are common in seminars and discussions, focusing on various topics in physics.

02:55:03

"Black Hole Singularity Challenges Mass Concept"

  • Mass inside a black hole gets crushed due to gravity, leading to a singularity where mass exists in zero volume, creating an infinity in density.
  • In the quantum description, the singularity may get fuzzed out, challenging the concept of mass in zero volume.
  • Genius is not limited to scientists like Albert Einstein; wisdom and insight can exist in various minds, enriching the world with diverse perspectives and experiences.
  • The richness of human experience contributes to the wealth of insights in the world, emphasizing the importance of respecting and valuing the diversity of perspectives and insights shared by individuals.
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