Berkeley Lab’s Oct. 26 Science at the Theater event, “Dark Secrets: What Science Tells Us About the Hidden Universe,” was a smash hit: more than 600 people packed the Berkeley Repertory Theatre and over a hundred people had to be turned away.
Berkeley Lab Public Affairs Head Jeff Miller kicked off the event and introduced host John Fowler, health and science editor for KTVU Channel 2, and Berkeley Lab astrophysicists and cosmologists Saul Perlmutter, David Schlegel, and Alexie Leauthaud.
Perlmutter spoke about how dark energy was discovered, by using particularly bright exploding stars called Type Ia supernovae as “standard candles” to measure how fast the Universe has expanded. The trick is to compare how far away a supernova is (and thus how far back in time it is) with the expansion of the Universe since then. Instead of slowing down as they expected, they found expansion is accelerating, propelled by unknown dark energy.
Schlegel described baryon acoustic oscillations, which give cosmologists a “standard ruler” to measure expansion in addition to standard candles. Dense accumulations of galaxies repeat every 450 million light-years. These “baryon oscillations” were formed by sound waves in the liquid-like plasma of the early universe and left their mark in the temperature variations of the cosmic microwave background, so the ruler can be used from the earliest times.
Leauthaud devoted her talk to measuring the amount of dark matter in the universe, using the phenomenon predicted by Einstein that mass curves space-time. Because massive clumps of invisible dark matter distort the images of distant galaxies behind them, scientists can calculate how much dark matter exists where, and use these measurements to learn how the large-scale structure of all the matter in the Universe has evolved.
The talks were followed by a lively question-and-answer session that didn’t stop until the theater had to close. The evening proved a testament to the fascination that the mysteries of cosmology and the fate of the Universe exert on human beings even in the midst of earthly concerns about jobs, money, and other worries.
For more on how scientists are trying to discover the true nature of dark energy, check out the three-part series, ” The Evolving Search for Dark Energy.” Part one talks about supernovae, part two talks about baryon acoustic oscillation, and part three describes gravitational lensing.
Before the show started, Berkeley Lab Communications Group Head Doug Isbell, who represents the International Year of Astronomy, set up telescopes on the sidewalk (including an inexpensive but high-quality model designed by the International Year staff) outside the theater to view the Moon and Jupiter. The telescopes proved so popular the overflow crowd kept him busy through most of the program.