3/15/16 Show feat. Justin Ripley on anti-gravity and cosmology + organ donors & AI’s AlphaGo win


Image: Casimir plates, which attract each other just because of standing waves that exist in vacuum between them. Just one of many crazy effects predicted with math!

This week on These Vibes, we hosted Justin Ripley, a second-year graduate student in the Princeton Department of Physics, for an interview about his work in theoretical cosmology. The discussion dug into the deep philosophical side of physics, probing ideas like how time began and what clumps of dark matter might look like.

Justin is a cosmologist, which means he studies events that occur on the grandest scales of our universe. He’s driven by a search for fundamental laws: what did the universe look like when it was the size of a basketball? What can those processes tell us about the rules underlying our present-day reality? When you look at space around us through this lens, the stars and planets become fossils–and cosmology is excavating these remains of the Big Bang for deep clues about the nature of physics.

One notion Justin brought up is the idea of anti-gravity. Unlike the attractive force that keeps us on Earth and our solar system in alignment, this repulsive force can happen when you consider negative energy states, an idea which is hard to visualize in practice but which can be expressed in mathematical models. It’s examining these equations that Justin hopes can lead to new developments in cosmology. If the models line up with experimental evidence (like Stevie’s cosmic microwave background, or LIGO’s recently-discovered gravity waves), then we can push the laws of physics into new territory.

After many questions from listeners, we moved on to dark matter and the ways in which it might clump together. Like we discussed last week, dark matter has to exist, because we can indirectly measure its mass–but it’s invisible and doesn’t interact with anything (except gravitationally). Scientists like Lisa Randall at Harvard point out that dark matter could form planets and galaxies of its own, clumping together (check out the N-body simulation below!) just like the matter that makes us and our Earth. Experiments like Gaia are examining the motion of astral bodies, trying to detect changes in their paths that might indicate clumps of dark matter nearby.

After Justin’s interview, Stevie came on the mic to talk about this exciting new study that might allow universal organ transplants. Just as some peoples’ blood types aren’t compatible with others, organ donations tend to be limited by the need to find a perfect match. That’s why family members might be the first to give up a kidney for their relative: because their genes match so well, there’s a better chance the donated organ won’t be rejected by the recipient’s immune system. This new technique, called desensitization, could allow even an incompatible organ to remain successfully in its new body after the transplant. Even though the technique is new and (presently) expensive, it’s worked in many patients and has the potential to revolutionize the way we organize transplants.

To end the show, Justin and Brian talked about Google’s AlphaGo computer and its 4-1 win against Go grandmaster Lee Sedol over the past week. This is a historic win for artificial intelligence, since Go is known to require a lot of intuition: it’s a game that humans are good at and computers have a hard time learning. DeepMind’s team overcame this obstacle with neural networking (as discussed in this past interview), which allowed the computer to learn the game and tune its strategies over time.

The playlist can be found here on WPRB.com.



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