Kip Thorne lec­tures on the Big Bang, black holes, col­lid­ing stars

Tehran Times - - SCI / MED -

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.

Grav­i­ta­tional waves

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.

In­tri­cate sys­tem

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.

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