Even though his topic of gravitational waves dates back to Einstein’s Theory of Relativity, with hosts of scientists making slow strides in proving and detecting the cosmic phenomenon during the past 100 years, CU Denver Professor Emeritus Clyde Zaidins found himself rewriting his Nobel at Noon lecture at the last minute.
Zaidins cannot blame his hurried re-do on procrastination or boredom, not when his subject matter already rivaled Galileo and his telescope on its importance to his field. Rather, a new finding announced just days before the Physics Department chair’s scheduled talk blew his power-point apart, much like the first-ever observed binary neutron-star merger that fueled the news.
“The first detection was exciting,” Zaidins told his audience of nearly 30 people in the Jerry Wartgow Welcome Center, referring to the capturing of gravitational waves on Earth for the first time ever about two years ago. “But this (the neutron-star event) was really, really exciting,” he told the group gathered to hear about the ground-breaking work of 2017 Nobel Prize winners in Physics Rainer Weiss, Barry C. Barish and Kip S. Thorne.
The talk was part of the Tuesday lunch-and-learn series held in the Student Commons Building and sponsored by the Office of Research Services.
Discovery of cosmic proportions
Heralded for opening a giant window to the universe, the first detection of gravitational waves occurred in 2015, when two U.S. observatories observed the waves of a black-hole collision that happened some 1.3 billion years ago. “Energy released in that instant was 1,400 times the total energy our sun will release in its 10-billion-year lifetime,” Zaidins said. “This number just blew me away.”
Zaidins recognized many contributing scientists in the discovery of gravitational waves, back to Albert Einstein, who theorized in 1916 that when any mass moves in space, gravitational waves traveling at the speed of light should result.
These waves would distort the fabric of space as they propagate out in a rippling motion, much like the ripples when a stone is thrown in a pool of water, Einstein determined. Yet the waves’ signals would be so weak, the scholar doubted they would ever be detected on Earth.
Thanks largely to the work of the Nobel-prize trio, considered the masterminds behind the Laser Interferometer Gravitational-wave Observatory (LIGO) where the signals were finally received, that day did come.
Nobel at Noon schedule
Nov. 14 – Literature, Cynthia Wong
Nov. 28 – Chemistry, Scott Reed
Dec. 12 – Economics, Laura Argys
Dec. 19 – Physiology/Medicine, Chris Phiel
All presentations are at noon in the Jerry Wartgow Welcome Center in the Student Commons Building, 1201 Larimer St.
The presentations are free and open to the public.
A massive detector
The twin LIGO facilities are separated by 1,865 miles, with one in Livingston, La., and the other in Hanford, Wash. The observatories are L-shaped, with each of the four vacuum-tube arms spanning 2.5 miles. They work in unison to measure a motion 10,000 times smaller than an atomic nucleus, the smallest measurement ever attempted.
“This was a huge undertaking, very expensive to build, and everyone gives the NSF (National Science Foundation) a lot of credit for taking a chance on this,” Zaidins said. “It was one of the biggest projects it has ever funded.”
The project, which furthers physics in many other ways, paid off big, when scientists observed on Sept. 14, 2015, the final 0.2 seconds of two black holes (one 35 times the mass of the sun, the other 30 times the sun’s mass) merging together, a violent cosmic phenomenon until then never recorded.
“The fact that we’ve seen four more events since then means we are really in business,” Zaidins said, referring to three more black-hole collisions, and the latest observance of two neutron (or dead) stars colliding.
‘Really, really exciting’
When the properties of the LIGO detectors were determined, it was clear that the signal they would capture from merging black holes was about 10 times as large as the signal they would detect from merging neutron stars, Zaidins said. “As a result, they figured this was what they were going to see: waves from black holes.”
But after a similar observatory (Virgo) was added in Italy, the neutron-star event was detected, a merger determined to be 130 million light-years away. Because black holes cannot emit light, and neutron stars can, the discovery opens the doors to more possibilities and has resulted in an explosion of scientific study around the world.
“One cool thing about this was we have had satellites up that are looking for gamma rays for 40-some years now,” Zaidins said. “They were originally sent up in the early 1970s to try to detect nuclear tests. They started seeing gamma-ray bursts, and they weren’t really sure what these bursts were due to. But by August of this year, they were suggesting that one reason might be the merging of binary neutron stars.”
And then it happened. “Just 1.7 seconds after the gravitational waves were detected by LIGO, a gamma-ray burst was detected by satellite,” Zaidins said. Visual identification was made fewer than 11 hours later, as scientists were able to use the entire electromagnetic spectrum, from radio and infrared to ultraviolet and gamma rays, he said. “That’s one reason it is so exciting. You can actually see it,” Zaidins said.
Only the beginning
More observatories are planned in Japan, Australia and India. “This is a new astronomical window into the universe,” Zaidins said, adding that scientists are looking forward to using this diagnostic tool in many areas. “And the greatest, most exciting possibility of all is unanticipated phenomena, something we don’t expect.”
Photo at top: About 30 people attended the Nobel at Noon discussion about the Nobel Prize winner in Physics. The lunch-and-learn series continues through Dec. 19.