Alex Filippenko — Astrophysicist and professor of astronomy at UC Berkeley, member of the two teams whose supernova observations discovered the accelerating universe and dark energy (2011 Nobel Prize in Physics). One of the world's most admired science educators.
The gist
Lex Fridman talks with astrophysicist Alex Filippenko about the biggest questions in cosmology. They cover whether the universe will expand forever, what dark energy and dark matter might really be, and the existential threats facing humanity from asteroids, comets, supernovae, and solar flares. Filippenko argues that machines, not flesh-and-blood humans, are our likely interstellar descendants, and explains why he believes intelligent life is extremely rare. The conversation also dives into how supernovae forge the elements of life, the human drama and unfairness of the Nobel Prize, and Filippenko's memories of mentor Richard Feynman, closing on the meaning of life and the idea that we are the universe coming to know itself.
Big reveals
- Filippenko admits he sometimes wakes up at night worried that dark energy and dark matter are modern 'epicycles' - band-aids that could be completely wrong.
- He argues human-caused (anthropogenic) extinction threats are greater than celestial ones like the sun burning out.
- He believes self-replicating machines/AI, not humans, will be our evolutionary descendants who actually colonize the stars.
- As a self-described pessimist, he sides with the view that we may be the only intelligent civilization in our own Milky Way galaxy.
- Finding advanced or fossilized alien life would be 'bad news' because it would mean the great filter lies ahead of us, not behind.
- He respectfully disagrees with Stephen Hawking, arguing broadcasting our presence to aliens is irrelevant to our safety.
- He confronts the dizzying idea that the observable universe (45.7 billion light-year radius) is older than light could traverse, and likely spatially infinite.
- Filippenko candidly discusses that he could make a good case for being among the three Nobel laureates, and that it weighs on him.
Things worth remembering
- A civilization-changing asteroid is about 1 km across; a true mass-extinction asteroid is 10 km or larger.
- Deflecting an incoming asteroid early can require only slowing it or speeding it up by four minutes, letting Earth move out of the way.
- The most efficient food source for humans living on Mars may be insects, due to their high protein.
- Roughly 50-100% of all stars are estimated to have planets, with about one in five having a roughly Earth-like planet.
- A rocket at Earth's escape speed would take about a quarter-million years - 10,000 human generations - to reach Sirius, 8.7 light-years away.
- To travel at near light speed in zero time would require an infinite amount of energy, per E=mc-squared and relativity.
- Because space itself expands, light can appear to traverse more distance than its travel time suggests, yet never locally exceeds light speed.
- The Higgs discovery required five-sigma confidence (about one chance in 2 million of being a fluke) - 'extraordinary claims require extraordinary evidence.'
- A white dwarf can pack about half the sun's mass into a volume the size of Earth, and explodes near the Chandrasekhar limit of ~1.4 solar masses.
- The elements in our DNA, bones, and blood - carbon, oxygen, calcium, iron, phosphorus - were all forged in stars and ejected by supernovae.