What are Einstein’s gravitational waves?
WASHINGTON — Astronomers on Thursday announced that their new billion- dollar U. S. observatory has detected a gravitational wave, a phenomenon Albert Einstein predicted a century ago in his theory of general relativity. Here’s what that breakthrough means.
What is a gravitational wave?
Gravitational waves are extremely faint ripples in the fabric of space and time that come from some of the most violent events in the universe. In this case, it is from the merger of two black holes 1.3 billion light-years away. The way to think of this is to imagine a mesh net and visualize pulling on its ends. Those kinks are sort of like what a gravitational wave does.
What is space-time?
Space-time is the mind-bending, four-dimensional way astronomers see the universe. It melds the one- way march of time with the more familiar three dimensions of space.
General relativity says that gravity is caused by heavy objects bending space-time. And when massive but compact objects like black holes or neutron stars collide, their immense gravity causes space-time to stretch or compress.
How is this ‘hearing’
the cosmos?
Scientists mostly use the word “hear” when describing gravitational waves, and the data does, in fact, arrive in audio form. The researchers can don headphones and listen to the detectors’ output if they want. On Thursday, to prove they found a gravitational wave, the researchers played a recording of what they called a chirp.
How can they be certain?
Astronomers sat on the discovery for nearly five months, since Sept. 14, checking back and forth to make sure it was right. They considered all
Steven Senne / AP
MIT astrophysics professor Nergis Mavalvala (right) celebrates with Rebecca Weiss, wife of MIT physics professor Rai Weiss, following Thursday’s update by MIT scientists.
sorts of Earth-bound interference or noise, examined the possibilities and eventually dismissed them.
The astronomers are so cautious that they routinely have other scientists deliberately inject false data to test their abilities. In those tests, the observatory team was able to show that the injected data wasn’t real. In the case of the discovery announced Thursday, they are extra certain they are not seeing injected or hacked data because the system that allows false information to be inserted was down at the time.
ATLANTA — Georgia lawmakers on Thursday approved a bill explicitly stating that religious officials can refuse to perform gay marriages, their first significant action on a variety of proposals creating legal exemptions for same- sex marriage opponents.
Supporters of the “Pastor Protection Act” acknowledge that religious leaders already have that protection under the U.S. Constitution, but argue it will reassure them following the U.S. Supreme Court’s recent ruling effectively legalizing gay marriage.
The court’s decision has prompted at least eight bills that would create exemptions for opponents of the marriages in Georgia, one of more than 20 states where lawmakers have introduced such proposals, the ACLU has said.
The Georgia bill shielding religious officials moved quickly through the House with backing from the chamber’s top Republican, House Speaker David Ralston, and little resistance from gay- rights advocates and business leaders who have opposed broader bills. Ralston was criticized by some Republican lawmakers and Evangelical groups, however, when he questioned the need for other measures, including versions of the federal “Religious Freedom Restoration Act.”
Thursday’s debate put that split on display. Conservative House members said the pastor bill didn’t go far enough but all voted in favor. Several read aloud from the Bible before the House vote. Rep. Kevin Cooke, R-Carrollton, specifically called for action on a broader “Religious Freedom Restoration” bill; he didn’t cast a vote on the pastor bill.