From the moment Einstein hypothesized in his general theory of relativity that

gravitational waves exist, scientists have spent 100 years trying to prove it.

Now, students can finally follow the steps taken to prove a scientific breakthrough that

opened an entire new field of astronomical research.

Nergis Mavalvala, professor at MIT and member of Laser Interferometer Gravitational-
Wave Observatory, helped improve the project’s laser interferometers. On May 4,

Mavalvala will discuss the detection of these waves at the William D. Watson Memorial

Lecture.

The University will be the next academic institute where the quantum astrophysicist will

thoroughly explain the complex science behind LIGO’s findings.

“It’s really very rare that a scientific discovery makes it to the stages of major

newspapers worldwide,” Mavalvala said. “So what I plan to do is kind of unpack what’s

behind these new headlines.”

Mavalvala will focus on two main aspects: building an instrument that is capable of

measuring changes in distances that are 1,000 times smaller than a proton and

observing its signal.

The signal indicates a collision of two black holes in another galaxy more than a billion

light years away.

Stuart Shapiro, professor in physics at the University, theorized about black holes and

gravitational waves for decades. He said the discovery excited him because he has

spent a large portion of his career trying to validate Einstein’s theory.

“(LIGO) detected a gravitational wave source, and when it was analyzed, it was a

perfect, generic binary black hole merger — the kind you can only theorize about,”

Shapiro said. “This is the most important test ever in the theory of general relativity.”

Although this signal was detected in Sept. 14, 2015, several tests were needed to be

conducted before confirming its validity five months later.

“We had to confirm that the instrument was working correctly, and that it wasn’t just

some artifact from the instrument — something else that made the mirrors move,”

Mavalvala said.

The LIGO team also had to verify that a fake signal wasn’t already inserted into the

data, which was a common procedure used to check their searching techniques.

Once LIGO was confident that their findings implied the gravitational wave’s existence,

they began to examine the black holes more closely. From the signal, they were able to

determine the actual source parameters of the black holes.

With a team of 1,000 people, this data was collected and transposed into a research

paper over the course of three months. According to Mavalvala, many versions of this

paper — about 27 versions to be more specific — were written before the final product

was published.

Although these processes became time­consuming, Mavalvala had a gut instinct that

she was dealing with genuine findings within the first day or two of obtaining the signal.

“One of the remarkable things about what LIGO measured is that the signal really looks

just as Einstein’s field equations would have predicted,” Mavalvala said.

LIGO had two detectors, located in Louisiana and in Washington, that both detected the

signal. Louisiana was the first to detect the signal, and Washington saw it seven

seconds later.

“So that time separation was important — the fact that the signal looked the same in the

tube detector,” Mavalvala said. “If it was some local artifact, like something bumping the

mirror, then it should be different in the two detectors.”

Once LIGO confirmed their observations on Feb. 11, Shapiro and his group of

University post­doctorates and undergraduates — known as the Illinois Relativity Group

— were able to simulate the cosmic scenario on their computers within a day or two.

“We get a plot of what is known as the ‘gravitational wave form signal’ that LIGO

detected,” Shapiro said. “One of these curves is the signal that LIGO detected; the other

curve is the signal we get in our computer simulation … We have two signals

overlapped. That means we nailed it — we know what happened.”

Abid Khan, senior in LAS and Engineering and member of the Illinois Relativity Group,

is ecstatic with the newest quantifiable evidence for black holes, but he is also curious

to hear about LIGO’s process.

“That was always something interesting to me,” Khan said. “How they were able to get

that precise to detect something that is (smaller than) an atom.”

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