LIGO founder Rainer Weiss talks gravitational waves at UW

There has been a great deal of talk about gravitational waves since scientists with the Laser Interferometer Gravitational-Wave Observatory (LIGO) announced back in February that they had collected the first evidence of the phenomenon in September 2015. Dr. Rainer Weiss, professor emeritus of physics at MIT and one of the founders of LIGO, talked about the history, discovery, and future of LIGO Tuesday at the University of Washington. The event was part of the Frontiers of Physics lecture series of the University’s College of Arts and Sciences.

Was LIGO really the first?

Dr. Rainer Weiss, a co-founder of LIGO, gave a lecture this
week at the University of Washington about the detection
of gravitational waves. The logos represent the more
than 80 organizations involved in the LIGO
Scientific Collaboration. Photo: Greg Scheiderer.

Weiss said that it might not be totally accurate to say that LIGO was the first to spot gravitational waves. Joseph Weber at the University of Maryland claimed to have detected them way back in 1969, but no other scientists could duplicate his observation, and the claim was eventually discredited. Weiss said much credit should go to Russell Hulse and Joseph Taylor, Jr., of the University of Massachusetts. They used a radio telescope to study what is now called the Hulse–Taylor binary, and noticed that the orbits of these two neutron stars around each other have decayed since they were discovered in 1973. A graph of the decay matches up precisely with a plot of the loss of energy predicted due to gravitational waves.

“It’s a dead ringer,” Weiss said. “That was, as far as I’m concerned, the first real evidence that there were gravitational waves. It was a very important moment, because there had been endless discussions in the scientific community about whether the gravitational waves that Einstein had predicted were real or not.”

In a way the detection of gravitational waves is like the story of an “overnight sensation” who hits the big-time after decades toiling in obscurity. The first glimmerings of LIGO go back more than 40 years, and the basic design of the observatory was actually created well before Einstein dreamed up gravitational waves as part of the general theory of relativity.

The beginnings of LIGO

Back in 1967 MIT asked Weiss to teach a course about relativity. He didn’t tell them that he wasn’t really up on the math of relativity, and joked that it was all he could do to keep a day ahead of his students. Weber was doing his experiments at the time, and Weiss had his class do a thought experiment—what Einstein would call a Gendankenexperiment—about how to detect gravitational waves using light beams. Their solution was essentially a Michaelson Interferometer, a device developed in 1880s. (An animated view of a simple interferometer is below; also check our recent post about LIGO from an Astronomy on Tap Seattle event.) A few years later, after the Weber findings were dismissed, Weiss started to think about the detection of gravitational waves a little more seriously.

“I wanted to convert that Gedankenexperiment into a real apparatus,” he said.

An animation of how LIGO works. A laser beam is directed through a splitter into two
equal-length arms, and reflected back. If the length remains the same, the reflected beams
cancel each other out. But if a gravitational wave distorts the beams, they do not cancel and
light reaches a detector. Image credit: LIGO/T. Pyle.

This was easier said than done. As noted, many in the scientific community doubted that gravitational waves existed, and even Einstein had expressed doubt that they could ever be detected. This made getting funding for the work a challenge. The technical obstacles were greater still. The device had to detect preposterously small distortions in spacetime—along the order of a thousandth of the width of a proton—and it had to do so in an environment in which there is a tremendous amount of noise. The Earth itself is spinning and vibrating, ocean waves lap up on the shore, a train goes by. They had to figure out a way to get the interferometer mirrors to hold still. That problem was solved by suspending the mirrors from multiple pendula, which themselves hang from a noise-reducing feedback system. Even a little heat or a molecule of oxygen in the interferometer tube could distort the light beam.

“The way you get rid of it: you make a very good vacuum, and that costs a lot of money,” Weiss noted. They also added mirrors to the basic design that make the light path longer and keep more light in the system, both ways to amp up the sensitivity of the instrument.

It’s no wonder this “overnight” discovery was more than 40 years in the making, and didn’t happen until a century after Einstein first proposed gravitational waves. Weiss spent a lot of time recognizing the many scientists who contributed to LIGO over the years, and noted that today the LIGO Scientific Collaboration includes more than one thousand people from 83 different organizations.

More discovery to come

The future of gravitational wave astronomy is fascinating, according to Weiss. With the VIRGO interferometer in Italy and LIGO-India (INDIGO) joining the LIGO facilities at Hanford, Washington and Livingston, Louisiana, scientists will be able to triangulate to get a better idea about where detected gravitational waves originate. The eLISA mission of the European Space Agency would be a huge interferometer in space that could possibly spot gravitational waves with longer lengths, created by such events as the mergers of supermassive black holes. The LISA Pathfinder mission successfully tested some of the technology earlier this year, and the ESA just this week put out a call for concepts for the next phase of the project. Most interesting is the possibility to detect gravitational waves from almost the instant of the Big Bang, which could be spotted as density variations in the cosmic microwave background.

“I fully expect that if there are gravitational waves that come from inflation, in the next ten years they’ll be found,” Weiss predicted.

A full house at the UW enjoyed the engaging lecture by Weiss.

Astronaut Hadfield sheds light on the darkest dark

Being afraid of the dark might be considered an indicator against a career as an astronaut. But retired Canadian astronaut Chris Hadfield knew two things as a youngster.

“I always wanted to be an astronaut,” Hadfield said during a talk last month at Town Hall Seattle. And, as a child he was deathly afraid of what might be lurking in the shadows or under the bed in the dark at night. Hadfield has written a children’s book, The Darkest Dark (Little, Brown Books for Young Readers, 2016) aimed at helping youngsters overcome their fears. It was released on September 13, the day of his event in Seattle.

Hadfield’s interest in space was fueled by his reading list as a kid. He read Jules Verne and Edgar Rice Burroughs. He was a big fan of the original Star Trek series and wanted to be Buck Rogers.

“It was all fantasy,” he said. “It was all science fiction. It was reading all of the different books and wanting some day to maybe be a spaceman and to go on space adventures.”

“Opening one of those books was permission to have an imagination,” Hadfield added.

The impossible becomes real

That imagination took Hadfield on many a flight around the universe in his sturdy cardboard box spaceship. It was all kind of a lark until the summer of 1969, the year he turned 10, when he watched on television as Neil Armstrong and Buzz Aldrin walked on the Moon.

Astronaut Chris Hadfield spoke at Town Hall
Seattle last month about his new book,
The Darkest Dark, aimed at helping kids
overcome their fears. Hadfield was afraid
of the dark as a child. Photo: Greg Scheiderer.

“What I looked at was Buzz and Neil,” Hadfield recalled. “These weren’t Buck Rodgers, these weren’t James Tiberius Kirk, these weren’t actors, these weren’t fantasy. These were real people. Neil was just a guy. He and Buzz did something very brave, very dangerous, very difficult, but they did it. They succeeded.”

“On the morning of that day of July 20 it was impossible to walk on the Moon,” he noted, “and yet by bedtime Neil and Buzz had put those foot prints all around the Eagle lander.”
It was Hadfield’s a-ha moment: the impossible can really happen.

“Impossible things happen as the result of somebody having a crazy, comic-book kind of inspiration and then working extremely hard and changing who they were,” Hadfield said. Even though Canada didn’t even have a space program at the time, he devoted most of what he did in life to preparing for his dream, so some day he could “put on a (spacesuit) and go to a place where nobody had ever been before.”

Preparation beats the demons

Preparation and practice chased away Hadfield’s demons and he made it to the astronaut corps, a member of NASA’s fourteenth astronaut class, in the summer of 1992. He flew space shuttle missions in 1995 and 2001. The first thing he did after reaching orbit on that first mission was to float over and look out the window.

“It’s the darkest dark you can imagine,” Hadfield explained. “The world is separate and the rest of it goes on forever.”

“Every window on the space ship has nose prints on it because astronauts are always there just trying to see and understand the rest of the universe,” he added. “It is a magnificent, humbling experience to have the world and the universe pouring by your window and to be living in a place where magic suddenly became real.”

In 2012 and 2013 Hadfield was a member of two International Space Station missions, commander of one. He became the first Canadian to walk in space.

“It is the most incredible experience of my life to be holding on to a spaceship with one hand, to be the very first person from my country—wearing a flag that means a lot to me—to be trusted to go do this on behalf of the millions of folks who might have wanted to be up there,” Hadfield said. “To have the whole world reassuringly spinning next to me, but to look the other way, to look out into the eternity of space, to truly, absolutely see the darkest dark there is.”

Hadfield read from The Darkest Dark and took audience questions at the end of his presentation. And, as you might expect from the guy who played David Bowie tunes from space, there was a song, as Hadfield played, in its world premiere, a video and song related to the book.



More books by Chris Hadfield

(Purchasing items through the Seattle Astronomy store supports
our efforts to bring you coverage of astronomy events.)

Mapping the 2017 total solar eclipse with Michael Zeiler

If you’ve been thinking about where to go to see the total solar eclipse that will cross the United States on August 21, 2017, you have more than likely come across the work of Michael Zeiler. Zeiler is the proprietor of the website Great American Eclipse.com. He has been an astronomy nut and eclipse chaser for many years, but just started making solar eclipse maps a few years ago.
Zeiler saw his first total solar eclipse from Baja, California in 1991 and was smitten.

Michael Zeiler is the proprietor of the websites
GreatAmericanEclipse.com and Eclipse-Maps.com.
Photo: Eclipse-Maps.com

“It just was an amazing experience to see the eclipse hanging high in the sky with the blackest black you could see where the Moon is, and the shimmering corona, the most beautiful object in the sky that you never see in your life except for the few precious moments of totality,” Zeiler said.

“I was hooked from that point on,” he added.

Zeiler has used Fred Espenak’s eclipse maps ever since. In fact, back in 1991 he’d just purchased Espenak’s book Fifty Year Canon of Solar Eclipses, and noted the date of the 2017 eclipse 26 years in advance!

Making eclipse maps

Zeiler practically fell into the business of making eclipse maps back in 2009. He booked passage on a ship for a total solar eclipse in the Pacific Ocean in July of that year. The cruise advertised that it would sail to the point of greatest eclipse. He found that Espenak’s map didn’t have a key piece of information that he needed to know if that was true.

“For a land-based eclipse, it’s straightforward, because you see the road network, you see the cities and the roads and the other geographic features so that you can place yourself on the map,” Zeiler said. “But for an eclipse at sea, there’s no real geographic reference around you, so if you have a GPS receiver, what you really need is lines of latitude and longitude drawn on the map.”

Zeiler, who works for the geographic information system software company Esri, decided to create it himself.

“I had the interest and the skill set so I made my own maps for this cruise,” he said. “I made a large map, laminated it, brought it on board the ship, taped it on one of the walls, and over a thousand eclipse chasers were on that cruise. That map was a smash hit.”

People encouraged him to make more, so he launched the website Eclipse-Maps.com late in 2009. The site became pretty popular. On May 20, 2012, the date of an annular solar eclipse visible from the American southwest, the site had a quarter million unique visitors and one million page views.

“I was stunned by that,” Zeiler said. “I didn’t expect that kind of response.”

It was at that moment that it struck him that the 2017 total solar eclipse was going to be huge. He snagged the URL GreatAmericanEclipse.com the very next day, launched the site, and has been working on it ever since.

“We constantly get emails or phone calls from people who are just jazzed about the eclipse and excited and wanting to learn more,” Zeiler said. “It’s a real thrill to participate in that.”

Vintage eclipse maps

Zeiler is a collector of vintage solar eclipse maps, and has images of some of them on the Eclipse-Maps website. His favorite era for eclipse mapping is the early 18th century, when the maps were not only gorgeous but amazingly accurate.

Casper, Wyoming eclipse map courtesy
GreatAmericanEclipse.com

“One of my key goals in making eclipse maps is to bring the artistry back into eclipse cartography, so I intentionally try and make the maps expressive, communicative, and just beautiful things to look at,” he said.

The man who has mapped the entirety of the 2017 total solar eclipse is headed to Casper, Wyoming as the starting point for his eclipse chase next summer. Zeiler said he considers three factors in making that decision: weather, mobility, and duration of the eclipse. He said the climate in Casper is good, and there are highways running east and west of town that pretty much hug the eclipse center line.

“All experienced eclipse chasers that I know are headed west for the weather, and we’re sacrificing ten or twenty seconds of maximum eclipse to get the great weather odds,” he said. The Astronomical League has chosen Casper for its annual conference in August for the same reasons. Catch our previous article and podcast about eclipse viewing in Casper.

Get eclipse stuff

GreatAmericanEclipse.com includes tons of information, maps, and a history of solar eclipses, plus a great selection of eclipse swag. You can buy your eclipse glasses there. Zeiler has also written a 44-page book, See the Great American Eclipse of August 21, 2017, that aims to answer all the questions people might have about the eclipse. The book includes two pairs of eclipse glasses.

Zeiler does it all with excitement about sharing the eclipse with people.
“This will be the most fantastic astronomy event in decades for this country,” he said. “It’s going to create a new generation of people that appreciate the beauty and the majesty and the science of our universe, and many people will become newly formed eclipse chasers.”



Resources

• Great American Eclipse website
• Eclipse Maps website
• Fred Espenak’s eclipse website
• Jay Anderson’s eclipse weather website

Learning about LIGO at Astronomy on Tap

The most recent gathering of Astronomy on Tap Seattle brought to town two scientists working in one of the most groundbreaking areas of astronomy: detection of gravitational waves.

Nature was kind to us

Jeff Kissel, a control systems engineer at the LIGO Hanford Observatory, talked about how exciting it was when they switched on advanced LIGO back in September 2015.

“Boom! Right out of the gate we saw this whopper of an event,” Kissel said, detecting gravitational waves from the merger of a pair of stellar-mass black holes. “Nature was very kind to us.”
What they spotted at Hanford and at LIGO in Livingston, Louisiana was a match.

“Inside our data, which is almost always noise, we saw this very characteristic wave form that was predicted by general relativity,” Kissel recalled. They found gravitational waves from a couple of other black-hole mergers in the following months.

“This is the beginning of gravitational wave astronomy,” Kissel said.

Gravitational waves oscillate through spacetime in a way
demonstrated by this animation. Credit: ESA–C.Carreau

Kissel pointed out that LIGO only detects a small part of the gravitational wave spectrum. As with light, gravitational waves can come in a wide range of wavelengths with periods ranging from milliseconds to billions of years. Longer-length waves might come from the mergers of galactic nuclei, or even from quantum fluctuations from the early universe.

“There’s a whole zoo of things to find out there,” Kissel said. He anticipates more ground-based observatories as well as some space LIGOs that could have detector arms millions of kilometers long.

How LIGO works

LIGO sounds awfully complicated, but, broken down, the idea is pretty simple. Jenne Driggers
is a Caltech postdoctoral scholar stationed at the LIGO Hanford Observatory, where her gig is improving the sensitivity of the interferometers. Driggers explained that, essentially, they shoot a laser beam into a splitter that sends beams down two equal arms four kilometers long. The beams reflect from mirrors and return to be put back together.

A simplified look at how LIGO works. A laser beam is split and sent down two equal
arms four kilometers long, then reflected back by mirrors. When they return to be
recombined, they will usually cancel each other out and no light will get to the detector.
But if a gravitational wave distorts the system, the light will be spotted by the detector.Credit: T. Pyle, Caltech/MIT/LIGO Lab

“When they recombine they can be exactly out of phase, and then there’s no laser light (at the detector),” Driggers said. “They cancel each other out totally. Or the lengths will change and these two electromagnetic waves can add up, and so we do get some light.”

When that happens it means that a gravitational wave has distorted the LIGO arms ever so slightly. They measure the light received at the detector to learn more about the wave.

In practice it’s a lot more complicated. It all happens in a total vacuum to avoid any distortion from air. The mirrors are suspended from a system of four pendulums, which helps to eliminate vibration. The mirrors are highly reflective pieces that each weigh around 100 pounds and cost half a million dollars. The laser is about the best there is.

“The laser wavelength itself is our ruler that we’re using to measure the distance between those two mirrors,” Driggers said, “and we need to be able to measure that distance to 10^-19 meters.”

“This is one of the highest-power, frequency stable, power-stable lasers on the planet,” she added.
Driggers invited people to tour LIGO Hanford. Public tours are held twice each month, and groups of 15 or more can arrange for a private tour.

Up next: LSST

Astronomy on Tap Seattle is presented and organized by astronomy graduates students at the University of Washington. Their next event is planned for Friday, October 28 at Peddler Brewing Company in Ballard and will feature UW scientists Dr. John Parejko and Dr. David Reiss, who are working on the Large Synoptic Survey Telescope project. The events are free. Enjoy beer and astronomy!

Astronomy tourism in Wisconsin

Mention Wisconsin to someone and their first thought might have something to do with cheese, bratwurst, or the Green Bay Packers. I’d suggest adding stargazing to the list after learning of some great resources during a recent trip to Milwaukee. I paid a visit to the Milwaukee Public Museum, where the The Daniel M. Soref National Geographic Dome Theater & Planetarium has just been upgraded to a Digistar 6 computer projection system.

Cool planetarium shows

I saw the museum’s planetarium show titled, “Did An Asteroid Really Kill the Dinosaurs?” It was a visually stunning show that left one feeling that T-Rex and the killer asteroid were actually in the room.

“We produced that, we wrote it, and put it up on the dome, and that’s because we had a big dinosaur exhibit,” explained Bob Bonadurer, director of the theater and planetarium, who added that they create many of their own original programs. He noted that the answer to the question in the show’s title is yes—for now.

“There’s lot of debate about volcanic eruptions possibly contributing to the death of the dinosaurs,” Bonadurer said. “Science always changes with new evidence, and we point that out at the end of the show.”

“Did An Asteroid Really Kill the Dinosaurs?” has since closed, but the planetarium is running two other astronomy-related shows along with its staple “Wisconsin Stargazing,” which looks at what’s up in the sky each month.

Bonadurer said its not all that common to find a planetarium that also has 2D and 3D movies.

“A lot of planetariums stand alone,” he noted. “Our planetarium is part of the big dome theater.”
The recent upgrade has brought even brighter, sharper resolution to the screen.

“With the astronomy software we’ll be able to take the audience on much more engaging trips throughout the cosmos,” Bonadurer said.

Stargazing in Wisconsin

Milwaukee and Wisconsin have active amateur astronomy communities. There are a half dozen astronomy clubs in the greater Milwaukee area, and the Astronomical League lists 14 affiliated clubs in the state.

“Those astronomy clubs are great to work with,” Bonadurer said. “They help us out with events such as eclipses, and, for example, the Mercury transit back in May.”

As with any big city, Milwaukee has problems with light pollution, but Bonadurer said there’s plenty of good stargazing to the north of town. Newport State Park, about 90 miles north-northeast of Green Bay, is a candidate for International Dark-Sky Park status with the International Dark-Sky Association.

“Like any metro area, we tell our planetarium audiences yes, take the drive, 40-50 miles, get away from the street lights,” Bonadurer said. “It’s a tall order, but do it because it’s worth it.”

“Planetarium skies are nice, but they obviously don’t hold a candle to the real sky,” he added. “We want people to get out there under the real sky.”

Total solar eclipse

Next August 21, when a total solar eclipse crosses the United States, Milwaukee will see the Sun obscured by just 85 percent. The Milwaukee Public Museum will offer programs to help people safely view the partial eclipse in town, and is also sponsoring a five-day eclipse road trip to get people into the totality.

Bob Bonadurer. Photo: Twitter.

“We’ve got our hotel rooms booked as a lot of planetariums or astronomers do,” Bonadurer said. “We’re usually on the leading edge of all this in getting the public excited.”

Bonadurer, who has seen four total eclipses of the Sun, will lead the tour, which will be able to take about 110 people to the eclipse.

“This will, I hope, reignite a little passion about eclipses in America, because it’s been a long time,” he said. “It’s the first one to sweep across America in 99 years, because for the one in ’79, only a small portion of America got to see it.”

Yerkes Observatory

Astronomy buffs visiting Wisconsin will also want to check out the historic Yerkes Observatory about 50 miles southwest of Milwaukee in Williams Bay, Wisconsin. The observatory, often called the birthplace of modern astrophysics, was founded by George Ellery Hale and has been the research home of Edwin Hubble and a veritable who’s who of astronomers. Check out our article about a visit to Yerkes during the 2012 Astronomical League Conference.

Bonadurer offers this advice to stargazers in Wisconsin and everywhere:

“Keep looking up, see that eclipse,” he suggests. “Get away from the street lights and enjoy this incredible universe.”

Swimming Stars Plaza

"Swimming Stars Plaza" is an art installation by Lezlie Jane in West Seattle's Whale Tail Playground.

Swimming Stars Plaza by Lezlie Jane
Photo: Greg Scheiderer

"Swimming Stars" depicts the constellation Cetus, often called the sea monster or the whale; thus Whale Tail Playground (which is actually at the north end of Alki Playground near the intersection of SW Lander Street and Marine Avenue SW) is a fitting spot. Glass stars in the concrete mark the shape of the constellation, and other marine critters linger about as mosaics or imprints as well, and there's a big octopus on the scene. Click the photo above to get a bigger version!

Cetus is the vehicle in a great story of mythology, sent by Poseidon in revenge for an insult when Cassiopeia, wife of King Cepheus of Ethiopia, claimed to be more beautiful than the Nereids. An oracle told Cepheus that he could stop the sea monster from ravaging his coast by offering up his daughter Andromeda as a sacrifice. Fortunately for her, the hero Perseus happened by and saved Andromeda in the nick of time!

The constellation Cetus is visible in the sky from the site of the "Swimming Stars" installation just four months out of the year, starting in October when you can see it in the south at around 10 p.m. Show up about an hour earlier each month through January to spot it.