Hello everyone, welcome to the Minescape Podcast. I'm your host Sean Carroll.

As many of you doubtless know, in the 1990s, especially near the end of the decade, the

very last years of the 20th century, cosmologists began to put together a picture of the inventory

of what our universe is made of. It's a weird answer that science is giving us whereby

only 5% of the stuff in the universe by energy is ordinary matter, by which we mean all

of the atoms, all the particles we've ever detected in particle accelerators or any

other experiment, that kind of stuff, which includes all the galaxies that you see, all

the light that you see from stars and planets and so forth, it all adds up to only 5% of

the stuff in the universe. Another 25% is something called dark matter, which we think

is some kind of particle that we just don't see, and the other 70% is something called

dark energy, which might be the energy of empty space itself. Now I know to a lot of people

who are not professional astronomers or cosmologists, this dark stuff, this 95% of the

universe, seems like some kind of fudge factor, just a recognition that astronomers don't

understand what the universe is doing. But in fact, these are testable hypotheses, and

over the last couple decades, astronomers have been increasing the precision with which

we can test and talk about dark matter in particular to enormous accuracy. So in fact,

the life of a real astronomer is not spent thinking about is there dark matter or isn't

there, but we can actually map out where the dark matter seems to be, how it's acting,

how it's interacting with other kinds of particles, both dark matter and ordinary matter,

how dark matter can influence the formation of stars and galaxies and even more. So today's

podcast guest is Lena Naseeb. She is currently, I think currently, a postdoc here at Caltech,

my home institution, and the fall she's going to start a job at MIT as a new faculty member

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