Wednesday, February 10, 2016

Expected Tomorrow: Annoucement of Direct Detection of Gravitational Waves - What Does It Mean?

The LIGO Collaboration has called a press conference for tomorrow at 7:15 am PST, and everyone expects it is to announce the first ever direct detection of gravitational waves.

Otherwise, as Peter Woit says, there is going to be a lot of disappointment.

Assuming it is that announcement, what does it mean?

I think it means that detecting gravitational waves via Advanced LIGO is relatively easy. Advanced LIGO -- the last phase of the project that started early in the '00s -- only started up in September of 2015, and even then it was being phased in over a couple of months, I was told.

So they've really only had a month or two of quality observing time. So direct detection of gravitational waves seems relatively easy -- i.e. the machine is working as it was designed to do.

It does not mean that we now know gravitational waves exist. We've known that for a few decades, since the work of Joseph Taylor Jr and Joel Weisberg based on the pulsar discovery of Richard Hulse and Joseph Taylor, Jr.

But directly detecting them is crucial, because it opens up the universe -- we can now see it with new eyes.

And new eyes have always brought vast new insights into the physical nature of the universe, whether it was Newton's experiments with prisms that resolved white light into its constituent wavelengths, or Hertz's findings with electromagnetic waves, or Curie's discoveries about radioactivity. As I wrote in my September Physics World article:
Whatever its cosmic source, the first direct detection of a gravitational wave will be big news. It will confirm a prediction from general relativity, but more importantly it will also give astronomers, astrophysicists and gravity theorists entirely new information about the objects they study. Indeed, astrophysicists hope that gravitational-wave observatories will someday operate as routinely as optical telescopes do today. If that happens, gravitational waves could fundamentally alter our picture of the universe, just as radio-wave and X-ray astronomy altered it from the placid, silent galaxies Edwin Hubble observed at visible wavelengths to the raucous universe we know today, full of quasars and pulsars, black holes and neutron stars. At some point, it may even be possible to observe cosmic events such as supernovae with light-based telescopes, neutrino detectors and gravitational-wave observatories – a new type of science dubbed “multimessenger astronomy”.
We'll see. I don't expect the announcement to be disappointing.

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