At the Alumni Day

‘It’s Complicated’. No this isn’t about the movie where Meryl Streep made a feeble attempt to be a porn star. It’s what I heard from a bunch of Harvard PhD physicists who had listened to John Kovac talk about the BICEP2 experiment a day earlier. I had figured as a humble chemist that if anyone would understand why polarized light from the Cosmic Background Radiation would occur in pinwheels they would. But all the ones I talked to admitted that they didn’t.

The experiment is huge for physics and several articles explain why this is so [ Science vol. 343 pp. 1296 – 1297m vol. 344 pp. 19 – 20 ’14, Nature vol. 507 pp. 281 – 283 ’14 ]. BICEP2 provided strong evidence for gravitational waves, cosmic inflation, and the existence of a quantum theory of gravity (assuming it holds up and something called SPIDER confirms it next year). The nice thing about the experiment is that it found something predicted by theory years ago. This is the way Science is supposed to operate. Contrast this with the climate models which have been totally unable to predict the more than decade of unchanged mean global temperature that we are currently experiencing.

Well we know gravity can affect light — this was the spectacular experimental conformation of General Relativity by Eddington nearly a century ago. But how quantum fluctuations in the gravitational field lead to gravitational waves, and how these waves lead to the polarization of the background electromagnetic radiation occurring in pinwheels is a mystery to me and a bunch of physicists had more high powered than I’ll ever be. If someone can explain this, please write a comment. The articles cited above are very good to explain context and significance, but they don’t even try to explain why the data looks the way it does.

The opening talk was about terrorism, and what had been learned about it by studying worldwide governmental responses to a variety of terrorist organizations (Baader Meinhof, Shining Path, Red Brigades). The speaker thought our response to 9/11 was irrational — refusing to fly when driving is clearly more dangerous etc. etc. It was the typical arrogance of the intelligent, who cannot comprehend why everyone does not think the way they do.

I thought it was remarkable that a sociologist would essentially deprecate the way people think about risk. I’m sure that many in the room were against any form of nuclear power, despite its safety compared to everything else and absent carbon footprint.

Addendum 7 April — The comment by Handles and link he provided is quite helpful, although I still don’t understand it as well as I’d like. Here’s the link https://medium.com/p/25c5d719187b

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Comments

  • Handles  On April 7, 2014 at 1:37 am

    As I understand it, during inflation (before the big bang) the universe was dominated by the energy inherent to space itself. Quantum fluctuations in the energy are stretched out across the universe by inflation. Then, the big bang happens and all the energy is dumped into matter and radiation. The fluctuations in energy become fluctuations in density. Areas of different density expanding makes gravitational waves.

    Light and gravitational waves both travel at the speed of light. However, light is slowed when it passes through a medium, but gravity is only affected by the curvature of spacetime. The light is slowed ever so slightly by passing through the rarified matter of space, and the gravity waves overtake the light waves. I think of the light waves as kind of bobbing up and down on the gravity waves, which polarizes them in a very specific way.

    I am a chemist, but I get my astrophysics from Ethan Siegel. Mistakes are mine not his:

    View story at Medium.com

  • luysii  On April 7, 2014 at 7:17 am

    Thanks, the link is helpful

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