[@lexfridman] Janna Levin: Black Holes, Wormholes, Aliens, Paradoxes & Extra Dimensions | Lex Fridman Podcast #468

Link: https://youtu.be/A6m4iJIw_84

Short Summary

Jenna Levin, a theoretical physicist specializing in black holes and related areas, discusses the nature of black holes, emphasizing that they are not dense objects but rather event horizons or regions of spacetime. She further explains the process of black hole formation, the behavior of spacetime around them, and the ongoing scientific quest to understand mysteries like the information paradox and the potential for wormholes, ultimately connecting these concepts to broader themes of science, humanity, and the search for a unified theory.

Key Quotes

Okay, here are 3 valuable quotes extracted from the provided transcript:

1. "Black holes are more general and more fundamental than just the death state of a star." This quote is a valuable insight because it challenges the common misconception that black holes are only a result of stellar death. It highlights the theoretical possibility of black holes forming in other ways, potentially from the early universe itself.

2. "The black hole is the event horizon. The event horizon is really just a point in spaceime or or a region in spaceime...It's more of a place than it is a thing." This is valuable because it offers a profound and counter-intuitive understanding of what a black hole actually is - not a dense object, but a boundary in spacetime.

3. "I'll give up locality meaning that I will allow things to be connected non-locally by a wormhole. So that is the weirdest thing you're willing to allow for which is arbitrary distance connection of particles through a wormhole. But quantum mechanics must be preserved. I'll entertain pretty weird things but I think that's the one that sounds promising." This represents a strong opinion in favor of quantum mechanics.

Detailed Summary

Okay, here's a detailed summary of the YouTube video transcript, broken down into bullet points:

I. Introduction & Overview

• The video is a conversation between Lex Fridman and theoretical physicist and cosmologist Janna Levin.
• Levin specializes in black holes, cosmology of extra dimensions, topology of the universe, and gravitational waves.
• Levin is an author of several books, including "How the Universe Got Its Spots," "A Madman Dreams of Turing Machines," "Black Hole Blues," and "Black Hole Survival Guide."
• Lex expresses admiration for Levin's message about physicists being human beings as well as scientists.

II. Black Holes: Formation, Properties, and Event Horizons

• Black Hole Formation & Misconceptions:
  • Black holes aren't just the death state of a massive star; they're more fundamental.
  • Initial idea of black holes started as a thought experiment (Schwarzschild solution).
  • Schwarzschild imagined crushing all the mass of a star to a point.
• Event Horizon:
  • Marks the separation in events where anything inside cannot affect events outside.
  • It's a one-way aspect of black holes; you can send things in, but nothing comes out.
  • The Event Horizon is not a physical thing. It is a location in spacetime.
  • Levin emphasizes that black holes are "no thing" and "nothing."
• Stellar Collapse:
  • Massive stars burn thermonuclear fuel until they run out.
  • Stars collapse under their own weight, creating a supernova explosion.
  • If the core is heavy enough (more than twice the mass of the sun), it will become a black hole.
  • As the star collapses, the event horizon forms. The star then collapses further into it.
  • The star leaves the event horizon behind.
• Singularity:
  • The closer one gets to the singularity, the more quantum mechanics comes into play.
  • The singularity is a location in time for someone inside of the blackhole.
• Oppenheimer's Contribution:
  • Oppenheimer wrote a paper in 1939 predicting the end state of gravitational collapse is a black hole.
  • This paper was published the same day the Nazis advanced on Poland.
• John Wheeler and "Black Hole" Terminology:
  • Wheeler coined the term "black hole" in 1967.
  • Wheeler initially disagreed with Oppenheimer but later conceded that Oppenheimer was correct.

III. Falling into a Black Hole: The Astronaut's Perspective

• Space-time Rotation:
  • As an astronaut approaches a black hole, their spacetime rotates relative to an observer's spacetime.
  • Part of their space rotates into your time, and part of their time rotates into your space.
• Time Dilation:
  • From the observer's perspective, time slows down for the astronaut, eventually appearing to stop at the event horizon.
  • The astronaut's perspective, not much time elapses as they cross the event horizon.
  • The astronaut crosses the event horizon without incident, and space and time are swapped in their future.
• Supermassive Black Holes:
  • "The bigger it is, the less noticeable it is that you've crossed the event horizon"
  • Black holes can be bright inside.
• The View From Inside:
  • Inside a black hole one might see a bright white flash of light and the evolution of an entire galaxy.

IV. Types of Black Holes & Formation

• Stellar vs. Supermassive:
  • Stellar black holes: Formed from collapsing stars. Hundreds of millions or billions of them in the Milky Way.
  • Supermassive black holes: Billions to hundreds of billions times the mass of the Sun.
• Supermassive Black Hole Formation:
  • Suspected they formed very early by collapsing out of primordial stuff.
  • One in the center of every galaxy.
  • Chicken-or-the-egg debate of Black Holes or Galaxies came first.
• Primordial Black Holes
  • Big early stars were formed from hydrogen and helium.

V. Space Time Visualization

• You can draw spacetime on a flat sheet of paper, but you need to remember that spacetime is not actually flat.
• Einstein says that "matter and energy curve space and time".

VI. Einstein & Space Time

• If Einstein was not limited by how little information he had, he may not have thought of the idea that space time was curved.
• Newton understood that something wasn't right when the apple fell from the tree even though Earth wasn't touching it. Newton did not understand action at a distance.
• The happiest thought of Einstein's life was that falling is the purest experience of gravity.
• Earth is in a free fall around the sun. International Space Station uses this principal to fall and stay in orbit.

VII. Mysteries of Black Holes

• Fundamentals: Black holes might have been around from the Big Bang. And the are flawless making them fundamental.
• Black holes have a very short list of properties: Charge, Mass and Spin.

VIII. Information Paradox

• Hawking was thinking about black holes and wanted to add a little smidge of quantum mechanics.
• Can never exactly know a particles position simultaneously with its motion.
• Vacuum: Because of Heisenberg, Can't say there are zero particles in a vacuum.
• Black holes steal on of these virtual particles and forces the other to live.
• Black holes emit thermal radiation:
  • Hawking said this would be featureless and not have any information in it.
• The particle it absorbs has to do with the switching of space and time that we talked about.
• The particle it absorbs has negative energy. Its mass goes down and the black hole gets lighter.
• The black hole eventually evaporates.
• Quantum mechanics was built to preserve information, the sacred principles.

IX. Information Paradox: Possible Resolutions

• Information Loss: radical resolution that information is truly lost
• Fuzzballs: Black holes aren't singularities surrounded by empty space. no true horizon to cross. in some sense, there is no interior to the black hole.
• Soft Hair: Subtle quantum hair, low energy quantum excitations, and store information.
• ER=EPR: Einstein Rosen Bridge = Einstein Podolsky Rosen. Suggests that entanglement connects spacetime geometry.
• Firewalls: A highly energetic region, A firewall that incinerates anything attempting to cross it. Levin thinks that we have been brushing too much under the rug.
• Levin is willing to give up Locality to follow quantum mechanics: arbitrary distance connection of particles through a wormhole
• This is why start to hear if the event horizon only exists when it's sown out of these quantum threads, does that mean that gravity is fundamentally quantum mechanics. That gravity is just emerging from this quantum description and that it's not fundamental.

X. Theory of Everything

• These hint that Gravity will emerge at a macroscopic level out of quantum phenomena.
• A lot of mathematics of anything that emerges from a complex system is very difficult to the transition.

XI. What are extra Dimensions?

• We know that there are three spatial dimensions, but we don't know why there are only three.
• There could be extra spatial dimensions, a little origami of tightly rolled-up dimensions.
• Strings and brains can wrap up in the extra dimensions causing construction.
• People are looking for if you can have some kind of natural selection of dimensions situation.
• If we are living on a three-dimensional membrane that moves through these higher dimensions. Then is there life on the other brains?

XII. Aliens and Space Travel

• Why haven't we seen aliens? I don't think there is any great filter. I can't imagine them not avoiding their own destruction.
• The predator and prey dynamic is really effective at creating at accelerating evolution and development. Seems like us being able to destroy ourselves is a really powerful way to give us a chance.
• But just life is so damn good that it seems like if things have a life force, it just seems to create life.
• What is the hardest thing on the chain of leaps that got to humans? Multicellularity.
• What if the membranes are Hairy in other ways.
• Levin says that even the great distances will probably not keep civilizations from getting together.
• There are topologically handles and holes in these connected spaces.
• Quantum energies may be key to traveling in these holes.
• These travels will allow us to reverse engineer with matter and energy.
• Blackholes are closely tied with travel and energy.
• Can be used to travel faster than the speed of light and discover new propulsions.
• Dark matter and dark energy is localized in space.

XIII. Dark Matter and Dark Energy

• Dark matter is clumps, halo around galaxy, does not interact.
• Dark matter could be localized in space
• People have said Dark Matter, and Dark Energy is just what physicists made up. To label the fact that they don't understand a large fraction of the universe. This is a misunderstanding as there is a precision to confronting the truth of the amount we don't know.
• Neutronies also act as dark matter.
• The Higgs field could have also explained dark energy. There is something we don't understand about the energy levels of Dark Matter.

XIV. Flat Earth and LIGO

• Flatearthers split into two groups, some became round earthers others though everything was a Sigh out.
• This a fascinating study of conspiracy theories because it is a cleanly wrong thing.
• Some of these people have romance with reason and logic.
• LIGO (Laser Interferometer Gravitational-Wave Observatory):
  • Gravitational waves are a wave created in the shape of space and follows black holes that are undulating.
  • It rings the shape of spacetime.
  • You can listen and hear these waves.
  • The mass of the final black hole will be less than the sum of the two starter black holes.
  • The wave amount is from the black holes emitted in E=MC^2 energy.
  • They can travel for two billion years to get to us as they were. *LIGO is building a giant musical instrument to record the shape of the ringing drum.
• The gravitational wave is like squeezing and stretching.
• LIGO measures less than 110,000th the variation in a proton over 4 km.
• It can be thought of more like sound than a picture. The black holes are mallets on a drum.
• Ry Weiss told Janna Levin a month before it was successful, said If it doesn't detect black holes, it's a failure.

XV. Alan Turing

• Connected to Girdle with what is decidable
• Created a universal machine
• His work was then used to create an enigma code
• Concluded we are kind of machine that can be copied.
• He used to chant one of the little, "dip the apple in the brew, let the sleeping death seep through"
• Then killed himself after chemical castration.
• "Macintosh with the bite out of it is a reference to Turing."
• Levin ties the minds together and finds that their lives had so much that was impossible to understand.

XVI. Jenna Levin's Views

• Levin's work is an experiment of life.
• Chief Science Officer of Pioneer Works.
• Feels it's important to understand how you are to others.
• Doesn't use label's outreach or education feels it to be culture
• We are constantly colliding with each other
• Fashion has influenced in the way she sees the world
• She likes to see abstract human themes and beautiful language used

XVII. Definitive Answers

• "You build something in the sand and then you erase it"