Kip Thorne lectures on the Big Bang, black holes, colliding stars
Over a thousand people packed into Jadwin Hall on Thursday, April 12, filling five auditoriums, to attend the 43rd Donald R. Hamilton Lecture delivered by Kip Thorne, Professor Emeritus at the California Institute of Technology.
Thorne, who won the 2017 Nobel Prize in Physics along with Barry Barish of Caltech and Rainer Weiss of MIT, spoke of his momentous discovery of gravitational waves, detected by the Laser Interferometry Gravitational wave observatory from a black hole merger 1.3 billion light years away.
Thorne opened by narrating the events which led to this historic finding in 2015.
“When multi-cell life was just forming on Earth 1.3 billion years ago, but in a galaxy far, far away, two black holes crashed together, creating a giant burst of gravitational waves, that traveled out … into the great reaches of intergalactic space,” he said.
These gravitational waves reached the outer edges of the Milky Way 50,000 years ago, during the age of the Neanderthals.
“On 14 September 2015, they reached the Earth. Touching down first on the Antarctic Peninsula, they traveled up through the Earth, unscathed by all the matter of the Earth, and emerged in Livingston, La., at one of two LIGO detectors,” Thorne continued.
Gravitational waves such as the ones detected in 2015 are actually incredibly difficult to pick up, mostly because of their minute effect on space time. When cosmic monstrosities like black hole collisions and neutron star collisions occur, the gravitational interactions with the environment around them are so violent that they bend space time.
These ripples in space time travel enormous distances to be detected by LIGO, so much so that the ripples in space that we observe are minuscule compared to the ripples surrounding the collision.
LIGO uses an intricate system called an interferometer, or a laser beam splitter reflected by 40-kilogram mirrors to find these tiny undulations in reality.
“Begin with the thickness of a human hair, divide by 100 and you get the wavelength of the light that is used to measure the (gravitational waves).
Divide by 10,000 and you get the diameter of an atom,” said Thorne. “Divide by 100,000 and you get the diameter of a nucleus of the atom. Divide by another factor of 1,000 and you get the factor of the mirror motion.”
Earlier that day, Thorne and Weiss paid homage to the late Robert Dicke, a former physics professor whose work on gravity was an integral precursor to Thorne’s and Weiss’s work on gravitational waves.