Black holes and LIGO on Bainbridge Island

The Laser Interferometer Gravitational-wave Observatory—LIGO—is leading scientists to discoveries at an impressive clip. Just two years ago we wrote about UW Bothell physics professor Joey Shapiro Key’s talk to the Seattle Astronomical Society about the detection of gravitational waves from the merger of two stellar-mass black holes—a discovery that won the Nobel Prize. Last week at Bainbridge Island Open Mic Science Key talked about LIGO, its latest detections, and plans for even bigger science in the future.

Joey Shapiro Key

Interferometers are a simple idea. They have two perpendicular arms of equal length. Laser light is split into the two arms, hits mirrors at the far ends, and returns to the source. If something changes the length of an arm, the light waves interfere with each other. LIGO in Hanford and a twin observatory in Louisiana are huge observatories with arms four kilometers long, and they are making amazing measurements.

“When we detect the gravitational waves they are quite pristine, even from billions of light years away,” Key explained. “But it was a challenge because gravitational waves interact so weakly with matter—that’s why they’re so pristine when they reach us—they’re very hard to detect.”

How hard? Einstein, who thought up the notion of gravitational waves and did the math to explain how they would work, thought the effect was too small to ever detect. It took a century to develop the technology to do it. LIGO can detect unbelievably minute changes in the length of its arms when a wave passes through.

“This is the most sensitive measuring device in the world,” Key said of LIGO. “For those four-kilometer arms, the change in the length in the arms we measure is a thousand times smaller than the width of a proton in the center of an atom.”


Simulation by SXS

The big discovery by LIGO since Key’s previous talk came in August of 2017.

“We detected a gravitational-wave signal from two neutron stars colliding, followed immediately by a detection of a gamma-ray burst by NASA’s Fermi satellite, and this set off a worldwide search for the source of that gravitational wave signal,” Key said. More than half a dozen observatories were involved in the work, observing the event in many wavelengths across the electromagnetic spectrum and pinning down the galaxy in which the collision occurred.

“This is the first ever multi-messenger detection with gravitational waves where we’re doing observations using gravitational waves and light,” Key said. Being able to see light from the event taught us a lot.

“We really learned from this one in particular that most of the heavy elements in our universe, including what solar systems are made of, what planets are made of, and what we are made of, comes from neutron stars colliding and kilonova events,” Key noted.

Just as light has a wide range of wavelengths, so do gravitational waves. Key said LIGO can only detect a limited slice of those wavelengths. It would be not able to find gravitational waves from the collisions of supermassive black holes or from the early universe. That will take a different tool.

“The future of gravitational wave astronomy lies in experiments such as LISA, the Laser Interferometer Space Antenna, that will do laser interferometry in space,” Key said. LISA is a joint venture between NASA and the European Space Agency, but there will be a bit of a wait for it. LISA’s planned launch isn’t until 2034. In the meantime, LIGO has plenty to do, with planned upgrades that will make the detector even more sensitive.

“We really are in a brand new era of gravitational wave astronomy, and there’s a lot to be discovered,” Key said.

Searching for life with giant telescopes

The Kepler Space Telescope discovered more than 2,600 exoplanets—planets orbiting stars other than our Sun. Kepler used the transit method, watching for tiny dips in the amount of light coming from a star when a planet passed in front of it. After more than nine years in space, Kepler ran out of fuel last month and NASA officially ended the telescope’s science mission. The torch has been passed to a new generation of planet hunters, and experts in the field of exoplanets say we may be less than a decade away from answering one of humanity’s biggest questions: is there life somewhere besides Earth?

Harvard physics Prof. David Charbonneau
gave a lecture at the UW Oct. 16.
Photo: Greg Scheiderer.

“We are the special generation that for the first time in human history is going to have the technological ability—if we choose—to go and answer this great question,” said David Charbonneau, professor of astronomy at Harvard University and a member of the Kepler mission team. Charbonneau gave a lecture recently at the University of Washington, part of the Frontiers of Physics series. He suggests that when we look for an inhabited planet, we don’t confine ourselves to just finding people.

“There may be other humans out there, but I’m going to advocate that we need to create and cast the broadest net possible when we go and actually make the first search for life outside the solar system,” Charbonneau said. He noted that SETI has been listening for years with no contact so far, and other planets are too far away to visit any time soon. But we are on the verge of being able to analyze the chemical content of exoplanet atmospheres, and that can tell us if there’s life on the ground. A scientist on a distant planet looking at Earth could tell there is life here by the chemicals in our atmosphere.

“Life has radically changed the content of our atmosphere,” he said, by creating oxygen and other elements. “We’re going to try to detect life through the unintentional waste products that are produced as life goes about its business.”

News reports of discoveries often note if an exoplanet is “Earth-like,” but in reality we know little about conditions on these far-away worlds. We can accurately figure an exoplanet’s size, mass, and density, but know little else about them. Two new telescopes—one in space, one on the ground—may be able to give us the data we need to know about actual conditions on these planets.

Giant Magellan Telescope

The Giant Magellan Telescope (GMT) is being built in Chile by an international consortium, and is expected to begin science operations around 2023. The GMT will be the largest optical telescope ever constructed, with seven 8.5-meter mirrors. This huge telescope will be able to gather an enormous amount of light, enough to analyze the atmospheres of exoplanets.

James Webb Space Telescope

The James Webb Space Telescope (JWST) is a NASA project scheduled to launch in 2021. JWST will have a 6.5-meter primary mirror, and the observatory will be able to observe light in the infrared, and that’s important.

“Infrared is where all the molecules we want to study show their fingerprints,” Charbonneau said, listing oxygen, water, and methane among the molecules of interest.

He said the JWST “will revolutionize essentially all major branches of astrophysics.”

Charbonneau said we need both of the new telescopes to nail down whether an exoplanet is inhabited.

“Individually, a large ground-based telescope or the James Webb Space Telescope cannot tell us if there’s life on a planet,” he said. That’s because they’re sensitive to different molecules. The GMT could spot oxygen, which usually means life. It’s not certain, though, because oxygen could be created in other ways. The JWST could find methane, carbon monoxide, and carbon dioxide, which would put that oxygen in context, determining if it’s there because of biological activity.

“The idea is together they can get the data that will allow us to conclude that there really is life,” Charbonneau said.

TESS and MEarth

While we wait for these two observatories to be completed, astronomers are not sitting idly by. NASA’s Transiting Exoplanet Survey Satellite (TESS) is continuing the work of Kepler, using the transit method to search for more exoplanets.

“Our mission is to find hundreds of nearby small planets amenable to detailed characterization,” said Charbonneau, who is a co-investigator on the mission. TESS will survey the entire sky over a period of two years. It was launched in April, began science work in August, and found its first exoplanet in September. Charbonneau said that by December they should have the data to determine if this new exoplanet has an atmosphere.

Charbonneau is the primary investigator for the MEarth Project, which is searching for habitable exoplanets around nearby stars. MEarth consists of two automated observatories, one near Tucson, Arizona and the other in Chile. Each employs eight robotic 16-inch telescopes that constantly watch M-dwarf stars for transiting exoplanets. There are several good reasons to look at these “red dwarf” stars. They’re plentiful—there are about 240 of them within 30 light years of us, compared to just 20 G-stars like the Sun. Since they’re smaller stars and not as bright, they won’t wash out an orbiting planet’s atmosphere, making the observation technically easier.

The following time-lapse video shows the MEarth-North observatory in action.

The point of both TESS and MEarth is to create a good list of things for GMT and JWST to check out once they come on line.

“The search for atmospheric biomarkers such as oxygen will be humanity’s first attempt to really answer this great question about whether or not we are alone,” Charbonneau said.

You can watch the entire lecture here:

Treknology looks at Star Trek gizmos

Star Trek first hit the airwaves over a half century ago, and Dr. Ethan Siegel finds it amazing how many of the gizmos, gadgets, and technologies imagined by the various Trek television series have become reality. Siegel, theoretical astrophysicist and science writer, is author of the new book Treknology: The Science of Star Trek from Tricorders to Warp Drive (Voyageur Press, 2017). Treknology is scheduled for release on October 15 and is available for pre-order on Amazon now.

Siegel, a Trek fan since discovering The Next Generation (TNG) as a kid, figures he was just the guy to dig into Star Trek’s technology.

“That intersection of an interest in Star Trek and Sci-fi, of an interest in what it means for humanity, and a knowledge of physics, all of those have come together to make this book possible,” Siegel said.

Treknology devotes a separate chapter to 28 different technologies that were used in the various series.

“These technologies that were so futuristic that they were imagined centuries in the future, some of them don’t appear to be that far off,” Siegel noted. “Some of them are already here and in widespread use. Others that we thought just a few years ago were going to be far-future technologies look like they’re coming to fruition.”

We’ve got that Treknology already

Siegel noted that it was The Original Series (TOS) that came up with the automatic sliding door, now a staple in every airport and supermarket. Your tablet is also cooler than anything Trek came up with.

“What you’ve got in your smart phone is much more impressive that anything that were on those touch-screen pads that Star Trek envisioned,” Siegel said. “Here we are with something that’s smaller, that’s more compact.”

That goes for pretty much all of the computers, he noted.

“We’ve gone way beyond what Star Trek would have envisioned much more quickly than anything that came about in the original series,” Siegel said. At the time of TOS in real life we had room-sized computers that had less computing oomph than today’s pocket calculators. When TNG came around, they figured they had to jazz up the computing and came up with something new and fancy—digital storage.

“Your flash drive is more powerful than a Star Trek isolinear chip,” Siegel noted. “As far as computation goes—ships computer, pads, isolinear chips—we’ve blown away what Star Trek would have envisioned.”

Medical technology

Dr. Ethan Siegel, author of Treknology,
during a lecture in Portland last year.
Photo: Greg Scheiderer.

As an astronomy and physics guy, Siegel said he was especially interested in learning about the medical technologies and biological situations that Star Trek dreamed up. He noted that we may soon be able to use synthehol, a substance with the positive effects of booze without the negative impacts.

“Synthehol is on track pharmacologically to become real,” Siegel said.

We may also be close to helping sightless people see, ala Geordi La Forge—the TNG character played by LeVar Burton—who wore a special visor that allowed him to see the entire electromagnetic spectrum.

“If we can make an implant somewhere in your brain’s visual cortex, and we can wirelessly feed an external signal to that implant,” Siegel said, “this is a potential way to restore sight to the blind,” even if they have no eyes or optic nerves at all. NASA actually tinkered with sight-improving technology in the late 1990s, and called its project JORDY: Joint Optical Reflective DisplaY.

Not there yet

There are other Treknologies that aren’t so close yet. Warp drive is at the top of that list. He says it’s mathematically possible, but it will be tough to make it work in our universe.

“It depends on if you can either have negative gravitational mass or negative energy,” Siegel explained. “If you can, then great, we can build warp drive. If that’s a physical impossibility—and we haven’t discovered anything like that yet—then I don’t know how warp drive can be possible.”

“This is probably one of the most difficult technologies to achieve, but I still don’t want to rule it out and say it’s impossible,” he added. “I want to look at what it would take to make it possible.”

A few other technologies such as subspace communication and transporters would require “extensions” to our current physics to become reality, Siegel said, and we’re a ways from life-like androids and holodecks, too.

Siegel has written widely. His first book was Beyond the Galaxy: How Humanity Looked Beyond Our Milky Way and Discovered the Entire Universe (World Scientific Publishing Co., 2015). He writes the Starts With a Bang blog on Forbes, and produces a podcast of the same name. Siegel can be found under that handle on Twitter and Facebook. He expects to be touring conventions and bookstores around the country in support of Treknology. We look forward to the book’s release next month.

Krauss and the greatest story ever told (so far)

We’re living in the best of times and the worst of times according to best-selling author and award-winning theoretical physicist Lawrence Krauss. The best is represented by the Large Hadron Collider (LHC), which has helped reveal the Higgs particle that ties together the standard model of physics. The worst is reflected by the president’s proposed federal budget that could derail physical science research. Krauss spoke about his latest book, The Greatest Story Ever Told—So Far: Why Are We Here? (Atria Books, 2017) last week at Town Hall Seattle. It was an informative and humor-filled lecture.

Author and physicist Lawrence Krauss 

spoke April 12, 2017 at Town Hall Seattle. 

Photo: Greg Scheiderer.

“This is really humanity at its greatest,” said Krauss of the discoveries at the LHC, which represent the work of thousands of scientists from all over the world. Krause’s talk was a walk through the history of discovery in physics, going all the way back to Plato and along the way bumping into Galileo, Newton, Faraday, Maxwell, Einstein, Fermi, Feynman, and more before arriving at quantum mechanics, the standard model, and the Higgs field.

“The real world is so different than the illusion that we see,” Krauss said. “The world of our experience is an illusion, and it’s an amazing story how we, over centuries, have been able to cut through that illusion to see reality underneath.”

We’ll leave the full tour of advances in physics to your reading of the book and, for this article, focus on Krauss’s take on the problems and challenges facing science today. He feels that much of the current mistrust of science stems from a common misconception that tomorrow’s science will make today’s obsolete, and that therefore scientific facts are little more than a subjective fad. Krauss said that is completely wrong.

Truth is eternal

“What is true today—and by true in science we mean what has satisfied the test of experiment today—will always be true,” he said. “Newton’s laws may have been supplanted at the extremes of scale by general relativity or quantum mechanics, but to describe baseballs or cannonballs or even rocket ships, they’re as true today as they were then, and whatever new physics we discover in quantum gravity or whatever, it’s not going to change. At the scale of humans, it’s got to revert to Newton’s laws. A million years from now, whatever we learn in science, if I let a ball go it’s going to fall as described by Newton’s laws.”

Krauss also let us in on what he jokingly referred to as a well-kept secret.

“Scientists are human,” he said. “That means they have prejudices and biases and pigheadedness, and that’s fine. What’s really neat is that science forces them in the right direction, kicking and screaming. The individual scientists are full of nonsense, but the scientific process protects us from that nonsense.”

Searching for a better toaster

Science is almost inextricably tied to technology, and Krauss frets that this causes people to wonder what new discoveries are “good for.”

“People don’t ask that for Mozart concertos or Picasso paintings or Shakespeare plays,” Krauss noted, “but it’s all the same thing. It’s what makes humanity worth living for. The fundamental importance of science, to me, is not the technology, but the fact that it forces us to confront reality and change our picture of our place in the cosmos. That’s what good literature, good music, good art do. That’s what the process of learning and growing as a society is all about.”

End of story?

The “So Far” in the title of the book is a reference to the notion that the story of discovery will continue to get more amazing if we keep asking questions. But Krauss is worried that we may not be able to do so. He noted that the president’s proposed federal budget would cut the Department of Energy—the primary funder of research in the physical sciences—by 20 percent, and eliminate funding for the National Endowment for the Arts, the National Endowment for the Humanities, the Corporation for Public Broadcasting, and the Institute of Museums and Libraries. That would save around $1.82 billion, while Krauss notes that the same budget would provide $2 billion to start building a wall between the United States and Mexico.

“To protect us against these unimaginable horrors, we’re willing to cut these things in our society that are so central,” Krauss observed. “We are in the process of getting rid of what is important for making the nation worth defending.”

“Art, literature, music and science are part of the greatest story ever told, and when we give that up in the name of defense, what are we really killing?” he asked.

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More books by Lawrence Krauss:

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LIGO and the era of multimessenger astronomy

Multimessenger astronomy is a fairly new buzz word in the science. Dr. Joey Key, an assistant professor of physics at the University of Washington Bothell and a member of the LIGO Scientific Collaboration, talked about the concept at last month’s meeting of the Seattle Astronomical Society.

Dr. Joey Key of the UW Bothell gave a talk about LIGO and
the era of multimessenger astronomy at the Dec. 21 meeting
of the Seattle Astronomical Society. Key made the same
presentation to the Everett Astronomical Society Jan. 7.
Photo: Greg Scheiderer.

As you probably know LIGO—the Laser Interferometer Gravitational-wave Observatory—made the first detection of gravitational waves, as predicted by Einstein’s theory of general relativity, back in December 2015 and announced the findings last February. So now what?

“The next big goal for LIGO is to have a gravitational wave detection where we also get an electromagnetic signal from the same source,” Key explained. She noted that various wavelengths of light, from gamma ray to radio, require different types of tools to detect and reveal different things about objects observed. Key said gravitational-wave astronomers refer to such science as “electromagnetic astronomy.” The big hope, then, is to learn even more if there can be an electromagnetic observation as well as a gravitational wave observation of the same event.

“That’s what we would call a multimessgenger source,” Key said.

A difficult search

Einstein never thought gravitational waves could be detected because he figured they would be too small. It took a century of technological advances to prove him right—again. Finding a multimessenger source may be an even more elusive needle in the cosmic haystack.

Key explained that, right now, it’s hard for LIGO to detect with precision from whence a source signal originates. When they detect a source they send an alert to about 60 electromagnetic astronomy partners and give them a general direction in which to look. In addition to the challenge of pinpointing the source, they also don’t really know what to look for. Key said their models aren’t very good, not yet anyway. Light from a source may have already passed, but there could be x-rays, gamma rays, afterglow, or shock waves under certain conditions.

Fortunately, LIGO is getting better. The addition of more Earth-based observatories will help better locate sources and discover collisions of neutron stars or stellar-mass black holes. Project LISA, scheduled to launch in 2029, will look for supermassive black hole collisions and “extreme mass ratio in-spirals” which occur when a little star or black hole falls into a big black hole. Pulsar timing arrays could detect when supermassive black holes collide in galaxy mergers. There’s even study of the cosmic microwave background to try to detect gravitational waves from early universe.

“Just like electromagnetic astronomy, different sources are detected by these different kinds of experiments,” Key said. “We need all these different kinds of gravitational-wave experiments to be able to study the gravitational-wave sky.”

The LIGO Scientific Collaboration includes more than a thousand scientists from 15 countries and 90 institutions. Four of the institutions are in Washington: The University of Washington, UW Bothell, Whitman College, and Bellevue College.

Unknown discoveries ahead

Key said it is an interesting time to be involved in the field as LIGO is just into its second observing run.

“We’re really going to be able to map out and explore the population of black holes in our universe,” Key said.

“We don’t know what we’ll discover, and that is always the story of a new astronomy,” she added. ”We do not know very much about black holes in general, and so this is a new way to study the universe and study what is out there. It will be very exciting!”

LIGO could discover new kinds of sources like cosmic strings, study supernovae, and maybe even lead to the detection of dark matter and dark energy.

“We are lucky we live in the era of gravitational-wave astronomy, and we hope soon that it will be the era of multimessenger astronomy,” Key concluded.

Mapping the heavens with Priya Natarajan

Priyamvada Natarajan, a theoretical astrophysicist at Yale University, is excited to be working in physics and astronomy at a time she and others call the “golden age of cosmology.”
“The maturity of our theoretical understanding, the sophistication of our instruments and tools that allow us to get the data—spacecraft, detectors—and the advanced computing are all aligned at the moment,” Natarajan said this week during a talk at Town Hall Seattle.

Theoretical astrophysicist Priyamvada
Natarajan spoke Nov. 14, 2016 at Town
Hall Seattle.

Natarajan has done a lot of work on mapping dark matter and dark energy, on gravitational lensing, and on figuring out how supermassive black holes are formed. It’s the latter that has her excited for the launch of the James Webb Space Telescope. She’s been a leader in pushing the idea that supermassive black holes could be formed by the direct collapse of matter. The physics pencils out, and Webb will peer back and possibly find the most distant, and therefore the first, black holes, and perhaps validate her ideas.

“The fact that you can come up with an idea as a scientist, for me, that’s the privilege,” she said.

Natarajan is the author of Mapping the Heavens: The Radical Scientific Ideas That Reveal the Cosmos (Yale University Press, 2016). She said she wrote the book not only to help us understand new discoveries about black holes and dark matter, but also to demystify the process of science.

“I believe very strongly that the current rampant disbelief in science stems from the contingent nature, the provisionality of science.” Natarajan said. “It’s something that’s very hard for the public at large to understand.”
The plus side is that cosmology and astronomy have the potential to win converts.

“Unlike many other fields in science, the night sky belongs to all of us,” she said. “We have to just look up and it’s there; the glory and the awe of the night sky.”

We know a lot

Natarajan finds it interesting that we know so much about the universe, with pretty solid evidence for much of what has happened since the tiniest fraction of a second after the Big Bang.

“It still stuns me that with a cantaloupe-sized gelatinous thing in our skull we’ve been able to figure all of this out,” she laughed. Yet despite all we do know, she said there is still a lot of mystery about our peculiar universe.

“We happen to live in one in which the total energy content of the universe is dominated by two components that we don’t know what they are,” she said.

Chart: NASA

What we call them are dark matter, which makes up 24 percent of the universe, and dark energy, which makes up 71 percent. We and all the stuff we see are less than five percent. Though we don’t know what dark matter is, Natarajan said there is solid evidence that it is indeed out there.

“The idea came out of an empirical need to explain an observation,” she said. Oddly enough, one of her other research interests, black holes, were conceived in exactly the opposite fashion.

“Black holes were actually proposed as a mathematical entity,” she noted. “They were a mathematical solution to Einstein’s equations, and they eventually became real.”

A little history

Dark matter was first suggested by Fritz Zwicky in 1933. Vera Rubin and others looking at galaxies in the 1970s proposed it as the reason rapidly spinning galaxies don’t fly apart. Natarajan said more than 80 years of research has left little doubt.

“We have incontrovertible evidence from many independent lines of investigation for the existence of dark matter because of the effects it produces, although it has not been directly detected yet,” she said. “We don’t know the particle.”

There are two lines of evidence, according to Natarajan, that make dark matter far more than just an inference.

“We can exquisitely map it at the moment, even though we can’t see it, because of the gravitational influence that it exerts,” she said. “The other way in which we can detect dark matter is the impact that matter has on the propagation of light in our universe.”

This is where her work on gravitational lensing fits in. Large galaxy clusters, with as many as a thousand galaxies, can act as a sort of gravitational lens on steroids. Such clusters would be held together by enormous amounts of dark matter. The relativity “pothole” created by the cluster could be strong enough to split a beam of light.

“You end up seeing multiple images of an object where in reality there is only one object,” Natarajan said, noting that this has been observed many times now. Interestingly, she points out that the physics of both Newton and of Einstein would predict the effect.

“You can apply both of these arguments to clusters and you infer the same amount of dark matter,” she said. “In my opinion that is really, really strong evidence, compelling evidence, because they’re completely different world views and they still converge. There’s no escaping the concept of dark matter.”

Search for the holy grail

Natarajan said this sort of research may help us get to the holy grail of physics: a quantum theory of gravity.

“The motivation is to look for gaps, look for disagreements, and look for anomalies where an observation is actually inconsistent with our theoretical expectation,” she said.

A couple of great examples of this came out of the 1800s. The orbit of Uranus didn’t agree with Newton’s Laws, so they did the math and figured another planet could cause the observed discrepancies. That led to the discovery of Neptune. At the same time, there were anomalies in Mercury’s orbit, which led to the proposal that another planet, called Vulcan, was the cause. Vulcan was never found, but years later general relativity explained the precession of Mercury’s orbit perfectly.

“In one case the theory remained intact and an anomaly refined our understanding,” Natarajan said. “In the other case it pointed the way to the existence of a more fundamental covering theory that was yet to come.”

We can’t wait for the next breakthroughs in this golden age of cosmology.

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The end of the beginning of the universe

Miguel Morales has been spending a lot of time pondering what he calls “the end of the beginning of the universe”—the cosmic microwave background. Morales, professor of physics at the University of Washington, heads up the university’s Dark Universe Science Center, a group working to figure out gravity, dark matter, dark energy, galaxy formation and evolution, and other cosmological mysteries. Morales gave a talk earlier this month titled “The End of the Beginning.” It was the second of a four-part lecture series, The Big Bang and Beyond, sponsored by the UW alumni association in celebration of the 50th anniversary of the Department of Astronomy.

The now-famous rendering of the cosmic microwave background “looks
like Pollock. It’s kind of a mess!” jokes Prof. Miguel Morales. Yet it may
hold clues to how the universe formed and how we all got here.
Image: ESA and the Planck Collaboration.

Morales gave a “Cliff’s Notes” history of the formation of the universe, noting that the end of the beginning came about 380,000 years after the Big Bang, when the hydrogen and helium plasma formed by that event cooled sufficiently to change phase and release light.

“It froze from an opaque helium hydrogen plasma to a clear, neutral gas,” Morales explained.

The “glowing wall of gas” left behind is the cosmic microwave background. Recent measurements have confirmed temperature fluctuations in the CMB.

“These are real, hot and cold spots that we see on the sky,” Morales said. “This is the writing of creation on the wall.”

Ghostly evidence

Morales noted that this writing is extremely faint. He pointed out that the differences between the red an blue sections of the now-famous Planck map of the cosmic microwave background are just one part in 100,000.

Miguel Morales explains how oscillations in plasma created sound
waves that can be spotted within the cosmic microwave background.
Photo: Greg Scheiderer.

“This is really a testament to precision measurement,” he said. He noted that, given this level of accuracy, we can learn a lot about what was going on in the early universe from the evidence left behind.
For example, scientists have teased out sound waves from the cosmic microwave background. The waves were created when the plasma oscillated in what was essentially a tug-o-war between gravity trying to collapse the mass and photons resisting that force. How those sound waves propagate could hold clues to what was going on in the early universe.

Changing tactics

The early observations measured temperature, but Morales said the state of the art is to look at the polarization of the light, which could lead to a needle in the cosmic haystack.

“You might be able to see, in the polarization, the ghost of gravity waves from inflation,” he said. They actually thought they had something in observations from the BICEP2 telescope at the South Pole, but what they saw actually turned out to be spinning dust.

“The polarization that BICEP saw is contaminated by the galaxy,” Morales said. “We’re seeing stuff on the windshield here; it’s not all primordial.”

One of the greatest challenges in making these observations is fine-tuning the instruments to ignore the noise and not be faked out by the data.

“BICEP is a technical tour de force, the measurement is awesome. It’s just a little contaminated, and, to be honest, Planck is not sensitive enough to say how bad the contamination is,” Morales explained.

That, he said, is science.

“We’ll keep looking, scratching our heads, building yet more sensitive instruments as we learn to read the words about the universe written faintly on the sky.”

Spooky action explained

according to author and journalist George Musser, “We’re starting to see the hazy outlines of an answer,” to questions about the how particles in different locations appear to act on each other. He is quick to add that there are still scientists who don’t really believe that non-locality is a real thing.

Author George Musser explains separate particles magically acting
on each other during his talk Nov. 3 at Town Hall Seattle.
Photo: Greg Scheiderer.

Musser is the author of Spooky Action at a Distance: The Phenomenon That Reimagines Space and Time—and What It Means for Black Holes, the Big Bang, and Theories of Everything (Scientific American / Farrar, Straus and Giroux, 2015). He spoke about the book and the science earlier this month at Town Hall Seattle.

Musser noted that Einstein was clearly bothered by some aspects of quantum mechanics, particularly the notion that randomness governs the universe. This led to his famous observation that God does not place dice.

“It was arguably Einstein’s number one concern,” Musser noted. “His deeper worry, actually the worry that led him to the worry about randomness, was the worry about non-locality. What is non-locality? How can this magic sorcery kind of thing be happening in the real world?”

That’s the quality that got Musser interested in writing about the subject.

“It’s the closest thing that we have in contemporary science to real, honest-to-god, Harry Potter magic,” he said. He noted that it turns up in many different sciences, and isn’t just a “freak show” over in quantum mechanics.

Space is constructed

Muster detailed the experimental evidence that has established that entanglement is a real phenomenon. String theory, loop quantum gravity, and other attempts to explain what’s happening have, at their cores, a similar idea, according to Musser. That idea is that space isn’t just empty and out there; it’s made of something.

“Anyone working on quantum gravity thinks that at some level space is constructed,” Musser explained. “That gives you the opening to deal with non-locality. No longer is that an insoluble puzzle that has been hanging in the air since Einstein’s days.”

Muster suggested thinking about water to illustrate the idea. A single molecule of H2O does not have the properties of water. It’s only when you get a whole bunch of that molecules together that water can flow or have surface tension.

“Likewise, if space consists of atoms, each individual atom is not spacial. Each individual atom lacks the properties we associate with spacial things,” Musser said. “Those spacial properties are derived collectively from the interactions among atoms.”

Given that idea, it’s possible that space can also change its state, just like water can boil and evaporate or freeze, and perhaps that’s part of what is driving our perception of different locations and entanglement.

“It seems that these things are in a predetermined location, but maybe that quality of being in a predetermined location is actively being generated all the time, below our level of consciousness, below the level even of our theories,” Musser said. “There’s some deeper machinery in the natural world.”

It’s a complicated concept to work into a 500-word blog post or a 45-minute lecture. You can listen to an audio recording of Musser’s talk on the Town Hall Seattle website. He is an engaging speaker, and Spooky Action at a Distance promises to be a good read.

Dark matter may have killed the dinosaurs

Harvard particle physicist and author Lisa Randall has a new hypothesis about what killed the dinosaurs, and it’s a surprisingly simple one. The possible culprit: dark matter.

Physicist Lisa Randall spoke at Town Hall Seattle about her
hypothesis that dark matter may have triggered the events that
killed the dinosaurs. Photo: Greg Scheiderer.

Randall visited Town Hall Seattle last week to talk about her ideas, explained in her new book Dark Matter and the Dinosaurs: The Astounding Interconnectedness of the Universe (Ecco, 2015).

Randall noted that ordinary matter forms into disks like our galaxy and solar system because it interacts with light, radiates photons, cools, and collapses. Dark matter, on the other hand, doesn’t interact with light and so stays diffuse. It is believed that the Milky Way Galaxy sits inside an essentially spherical halo of dark matter.

Here’s where Randall throws in a what-if. The model for dark matter presumes it consists of only one type of particle. But that’s not necessarily so.

“Maybe there’s a new type of dark matter in addition to the dark matter that people talk about,” Randall said.

“Suppose you had dark matter which could radiate,” she speculated. “Maybe dark matter interacts with its own light, which I’m going to call dark light.”

If that’s the case, this particle also could form structure, Randall said.

“Most of the dark matter is going to stay intact in a spherical halo, but this small fraction, maybe five percent of dark matter that interacts with dark light, can also collapse into a disk,” she said. This thin disk of dark matter would be embedded in the plane of the galaxy.

Here’s how that could have been the death blow for the dinosaurs, and a big chunk of the rest of the life on Earth, about 66 million years ago. Randall noted that, as our solar system rotates around the galaxy, it doesn’t follow a simple, flat course.

“As it goes around it actually bobs up and down through the plane of the Milky Way,” every 30 million years or so, she said.

“When it goes through that mid-plane, if there is a dark-matter disk there will be an enhanced gravitational force,” Randall explained. “So our hypothesis is that every time it goes through the mid-plane it can trigger comets getting dislodged from the Oort Cloud, and one of those could have been the comet that actually did in the dinosaurs.”

Randall stresses that this is all highly speculative, but she’s looking for evidence in her current research. She’s hoping to get data to further test the notion from the Gaia satellite, which will make precise measurements of the motions of about one billion stars. That will help us get a better handle on dark matter and where it is.

In the meantime Randall marvels at the interconnectedness of the universe. Galaxies could not have formed without dark matter, yet it may also have set into motion events that wiped out much of the life on our planet, also paving the way for large mammals, like us, to flourish.

The history of the universe in ten minutes

As communicators of science our job is often to take huge amounts of complicated information and condense it into something understandable. Scientist, composer, and author Glenna Burmer recently took on a monumental task: explain the 13.8 billion year history of the universe in a ten-minute movie.

Glenna Burmer talked during a presentation at the Museum of
Flight about her process for creating her movie “The Big Bang.”
Photo: Greg Scheiderer.

“There are some challenges being an amateur filmmaker and trying to condense this much information into a movie,” Burmer understated. She did it, though, and you will be able to see her work as part of the Origins: Life and the Universe multimedia concert that will be held Nov. 7 at Benaroya Hall. Burmer is one of eight composers whose work will be featured at the event. She and UW professor Matt McQuinn spoke at the Museum of Flight last Saturday to explain the Big Bang and preview Burmer’s film.

Burmer is a scientist; a molecular pathologist and expert in immunohistochemistry.

“As a passion, I have always loved astronomy,” she said in explaining her involvement in the project. Though a scientist, Burmer comes from a family of artists and musicians.

“Consequently, I’ve always wanted to try to synthesize science, art, and music, and this concert gives me the first-time opportunity to really do that,” she explained.

Among the challenges in doing a film about the Big Bang is that there’s no existing footage of the event, so creating visuals relied in part on particle animation technology. Burmer admits to being thrown off a bit by tensor calculus, membrane theory, and string theory, but she got enough understanding to help animators create a sequence demonstrating a Big Bang based on ekpyrotic theory. The animation shows two 3-D universes.

“They approach each other, they leak gravity, and they bud off our universe,” Burmer explained.

UW astronomy professor Matt McQuinn explained the evidence
for the Big Bang during a talk Oct. 17 at the Museum of Flight.
Photo: Greg Scheiderer.

Her film also uses pieces of many of the computer simulations McQuinn, a theoretical astrophysicist and cosmologist, used in explaining the Big Bang. He started out with an account of the discovery of the cosmic microwave background, the signature of the Big Bang.

McQuinn noted that the best evidence for a hot Big Bang is that there is way more helium in the universe than could have been created by fusion in stars. The explanation is that, soon after the Big Bang, hydrogen fused much more easily in the hot, dense new universe. Astronomers have built models based on the measurements of the radiation in the cosmic microwave background and how much helium such conditions would produce.

“The predictions from the hot Big Bang model just fall perfectly on the measurements,” of what is actually out there, McQuinn said. “This, coupled with the fact that we have seen the cosmic microwave background, makes it almost indisputable that there was a hot Big Bang. No respected scientist questions this picture any more.”

McQuinn explained that galaxies eventually formed because of fluctuations in the density of mass and energy. An as-yet undetected particle called the inflaton may be the cause.

“This particle seeded these density fluctuations,” McQuinn said. “The predictions of this model are in striking agreement with what we see, so people think that this is the answer for the source of energy fluctuation.”

“From studying the cosmic microwave background radiation, we’ve come to these profound conclusions,” McQuinn concluded. “We’re able to explain the universe down to planetary scales.”

The “Origins” concert is part of the celebration of the 50th anniversary of the Department of Astronomy at the UW. The concert will feature the work of eight composers and accompanying celestial photography. It is a benefit for the scholarship program at the University of Washington Astrobiology Program in the Department of Astronomy. Tickets are $32, $22 for students, and are available online or by calling the Benaroya Hall ticket office at 206-215-4747.

Jim Peebles and the cosmic microwave background

Jim Peebles is a giant of science. He was studying physical cosmology long before it was considered a serious, quantitative branch of physics, and has done much to establish its respectability. Peebles also has contributed a great deal to the thinking about dark matter and dark energy.

Legendary physical cosmologist Jim
Peebles makes a point during a lecture
at the University of Washington May
19, 2015. Photo: Greg Scheiderer.

Peebles, the Albert Einstein Professor of Science emeritus at Princeton University, gave a lecture titled “Fifty Years of the Cosmic Microwave Background” recently at the University of Washington.

“The last 50 years have seen a truly transformative advance in our understanding of the world around us,” Peebles noted in opening the talk. He explained that the idea of the Big Bang had been bouncing around for a while, and in the early 1960s folks were setting out to prove it as fact. Peebles was a research associate with Bob Dickie at Princeton, and the two of them advanced the idea of the cosmic microwave background. Along with research associates Peter Roll and Dave Wilkinson, they built a microwave radiometer to detect the signature of a hot Big Bang.
Little did they know that the evidence had already been spotted and measured.

Several years earlier, Bell Telephone Laboratories in New Jersey had done an experiment in communication using microwave radiation.

“This was an important forerunner to the sight of our students wandering around campus staring at their cell phones,” Peebles quipped. The experiment also found a lot of background radiation despite the best engineering efforts to eliminate it. By 1963 Bob Wilson and Arno Penzias at Bell wanted to use the technology to do radio astronomy, but they needed to solve the problem of the system noise.

“The Bell people had this constant irritation,” Peebles said. “They were getting more radiation than they expected from their communications experiments.”

It must be the CMB

Peebles had already been doing lectures about the possibility of the cosmic microwave background. By 1964 the Bell folks and the Princeton people got together. Peebles and Dickie figured that the system noise plaguing Wilson and Penzias was actually the cosmic microwave background.

“We had the possibility of a great discovery,” Peebles recalled. “We already knew right away that this was something new. That was exciting because you have a new phenomenon, something new to measure, and something new to make theories about.”

Measuring to prove it

The measurement piece took a quarter century, and was accomplished with spectacular precision by two experiments just months apart in 1990: NASA’s Cosmic Background Explorer (COBE) satellite, headed by John Mather of the Goddard Space Flight Center and George Smoot of Berkeley, and a rocket-borne experiment launched by Herb Gush of the University of British Columbia, along with Mark Halpern and Ed Wishnow. Both projects, in development for about 15 years, made measurements that meshed perfectly with the theoretical predictions for the cosmic microwave background.

COBE all-sky map. Image: NASA.

“It’s a glorious piece of evidence, I would say an iconic piece, that shows tangibly that the universe had to have evolved from a different state, because this is a thermal spectrum,” Peebles marveled. “Our universe as it is now is transparent for this radiation. There is no way it could force the radiation to relax to this thermal equilibrium. The universe had to have evolved from a state in which it was dense and hot enough to have relaxed to equilibrium and then expanded away from it.”

Interestingly, this is a tale of “missed it by that much” when it comes to Nobel Prizes. Dickie, Peebles, and the Princeton team were well on their way to making the measurement when they learned that Wilson and Penzias had already stumbled across it. The latter two won the Nobel in 1978 for their work. Mather and Smoot won the Nobel in 2006 for their COBE measurements, but Gush may have beaten them to it had it not been for equipment troubles that delayed the launch of his experiment.

Inflation: A cold little swoosh

Max Tegmark says that when he was applying for graduate school in physics, you’d best not mention the idea of parallel universes if you wanted to be accepted. A quarter century later Tegmark, an MIT physicist, stood before the 225th meeting of the American Astronomical Society making a plenary address titled “Inflation and Parallel Universes: Science or Fiction?” that made the concepts seem downright plausible.

Tegmark’s 2014 book, Our Mathematical Universe: My Quest for the Ultimate Nature of Reality, has sparked a lot of conversation inside and outside the scientific community. AAS Vice President Jack Burns of the University of Colorado says that made Tegmark a great pick for a talk at the biannual confab of astronomers.

MIT physicist Max Tegmark speaks at the American 

Astronomical Society meeting Jan. 7 in Seattle.

“Max’s approach to cosmology and big-picture questions have really been largely non-traditional, and I find that exciting,” Burns said in introducing Tegmark at the Jan. 7 meeting in Seattle. “Max is a rebel within a highly orthodox infrastructure that we all have to work in.”

Tegmark said that we as a species have a history of thinking too small.

“If we ask what we humans have figured out so far during the 13.8 billion years of our cosmic evolution, I think it’s one long story of underestimation,” Tegmark said. “We’ve again and again and again underestimated the size of our cosmos, realizing that everything that we thought existed was just a small part of something much grander: a planet, a solar system, a galaxy, clusters of galaxies, our observable universe, and maybe, as we’ll explore in this talk, a hierarchy of parallel universes.”

Tegmark said he wasn’t there to prove that inflation or parallel universes exist, but to correct some misconceptions. Most particularly, he poked at the notion that the existence of parallel universes cannot be tested scientifically. He contends that inflation predicts many phenomena that can be observed and measured. We wouldn’t throw out general relativity just because we have yet to observe a black hole directly. Likewise he said we shouldn’t dismiss parallel universes because we have yet to visit one.

Tegmark noted that inflation is more than just a mainstream idea now.

“It’s really, in my opinion, the most audacious idea we have, the most audacious extrapolation of physics so far,” he said. He noted that human growth interestingly parallels an inflationary early universe. Our number of cells double daily after conception, but the growth rates slows down soon after. The same happened with inflation. He points out that many people often think incorrectly that inflation followed the Big Bang.

“Inflation creates the Big Bang,” Tegmark said. “I think it’s more logical to say that before our Big Bang there was a cold little swoosh. That’s the early stages of inflation.”

“Inflation does this great party trick,” he added. “You can start with a tiny finite volume, less than a proton, and within there you can make an infinite volume inside the finite volume.”

Beings within a pocket may not be aware of what is going on outside.
“It’s pretty crazy, but that’s what you can do with general relativity,” Tegmark said. “Moreover, if there are many places where inflation doesn’t end, there’s nothing preventing you from having multiple, disconnected pockets like this.”

So how does Tegmark answer his own question? Are inflation and parallel universes science or fiction?

“Inflation has emerged as the most mainstream explanation for what happened early on,” he contended. “Whether it actually occurred and produced parallel universes is, of course, not yet settled. It remains controversial. But the key point that I want you to take away from this is that this controversy is clearly a scientific controversy, not a philosophical one, because the way it’s being settled is with data, not by people beating each other over the head with bottles in a bar.”

“2015 should bring much more clarity to what is going on,” Tegmark concluded. “Our universe is going to be an exciting place this year.”

The talk was engaging and the book should be a good read.

Tessering around the universe with A Wrinkle in Time at OSF

It is a bonus when our interests in theater and astronomy intersect, and that is happening this season at the Oregon Shakespeare Festival in Ashland with its production of A Wrinkle in Time, based on the 1962 novel of the same title by Madeleine L’Engle. The OSF play is a world premiere adapted and directed by Tracy Young.

Alejandra Escalante as Meg Murry in the Oregon
Shakespeare Festival production of A Wrinkle in Time.

In A Wrinkle in Time math whiz Meg Murry (Alejandra Escalante), her über-genius little brother Charles Wallace Murry (Sara Bruner), and pal Calvin O’Keefe (Joe Wegner) zip around the universe in search of missing papa Murry (Dan Donohue). They accomplish their travel by bending time and space in a tesseract, or “tessering,” as explained by the helpful science fair project by Science Girl (Jada Rae Perry).

Kids traversing the universe make for some imaginative and wonderfully silly stage effects and costumes, and we think especially of the multi-tentacled Aunt Beast (Daniel T. Parker), for whose costume a good half-dozen vacuum cleaners must have given their lives, or at least their hoses.

The performances are top-notch. We single out Escalante and Bruner especially, as well as Judith-Marie Bergan, who was much fun as Mrs. Whatsit, something of an intergalactic tour guide for the adventurers. Bergan, we think, can play anything, from the comic to the manic (as we note my Sweetie, the official scorer’s, recent review of last year’s production of The Tenth Muse.)


For all of its goofiness, the play takes on some serious themes about the mysteries of the universe, the nature of time and space, the dangers and advantages of technology, and of the strength and importance of family ties and love. The science isn’t so heavy that you need to be a cosmologist or physicist or a math geek like Meg to get it, though a bit of sci-fi familiarity with the concept is helpful.

According to the program notes the book took criticism from all sides when it came out, some charging it with being too religious and others saying it is too secular. That feels like it hit the right spot! The book also has some Cold War undertones about how things would look under a totalitarian society.

We’ve not read the book but plan to pick it up when we return home from Ashland. The play runs at the Angus Bowmer Theatre through November 1. It’s great fun; check it out!

***

This review is republished from the West Seattle Weisenheimer.

Lee Smolin says time is real

Seattle is a city full of geeks, it seems, and a bunch of us piled into the dark basement of Town Hall Seattle on a beautiful spring evening Tuesday to hear three talks about quantum mechanics, neutrinos, and the nature of time.

Dr. Lee Smolin was the headliner of the evening. Smolin has kicked up quite a ruckus with his new book, Time Reborn: From the Crisis in Physics to the Future of the Universe. In it, Smolin takes issue with a core notion of modern physics.

“We experience the world in time, we think in time, we act in time; this is so central to our conception of being human,” Smolin said. “But the scientific world view teaches that time is an illusion.”

Smolin added that, in his view, that claim is based on several incorrect arguments.
“Einstein and others who took that point of view are wrong for scientific reasons, and I try to make the scientific case for bringing back time to the center of our thinking and the center of our conception of nature,” he said.

Smolin rejects the notion that a mathematical description of the universe outside of time is the true reality, and that is the “crisis” of the book’s subtitle.

“If the experience of time is not central to reality, then neither are any human hopes and aspirations and the qualities that we so admire like decisiveness and imagination,” he said.

Smolin acknowledged that his arguments live somewhere in between physics and philosophy.

“I think that it’s essential to have the benefit of the history of thought when you’re tackling the deepest and hardest questions that we face, and the nature of time is one of them,” he contended.
The notion that time is an illusion has had its uses over the years, Smolin suggested, but added that the main fallacy of the approach has been what he called “physics in a box”, a method for studying small parts of the universe and then trying to extrapolate universal truths from that study. But he noted that you can’t put the whole universe into a box, and that the observers and the measuring systems in the experiments are typically outside of the box. And he said that even the laws of physics must be evolving, or if they aren’t, then they aren’t science.

“If the laws are truly outside of time then they’re inexplicable to any method that is checkable by science, because science requires experimentation and we can only experiment on things that can be modified,” Smolin said. “So if the laws are outside of time we just have to become mystics.”

The nature of time is a challenging topic for an hour-long talk, and Smolin had to punt a few times, noting that several concepts were topics for another hour, and that much more in-depth discussion could be found in the book.

We’re intrigued enough to grab a copy. You can get yours here.

Two talks by University of Washington graduate students preceded Smolin’s presentation. The talks were part of the UW’s Engage: The Science Speaker Series.

Ironically, Alan Jamison’s talk was definitely physics in the box. He gave an engaging presentation, titled “Cooling Atoms With Blinding Hot Light,” about his lab work to look at the behavior of ytterbium atoms, an element he joked “sits in a dark corner of the periodic table.”

“The first step in cooling atoms,” Jamison said, “is to heat them up.” As they vibrate intensely in the heat, individual atoms break off. Then they cool them down by shining lights on them; ytterbium has a resonance with certain green and purple wavelengths, and they can eventually slow the motion of the atoms down enough to get photos of clusters of them and study their behavior.

More on Jamison’s work at the Ultracold Atoms Group at the UW.

Jared Kofron followed with a talk about “A Massive Problem: A Brief History of the Tiny Neutrino.”
Kofron noted that the neutrino is the smallest particle we know of. “It’s a very strange, mysterious particle that has taught us a lot about the universe.” His talk was an accessible history of the neutrino.
The particle was dreamed up in the 1930s as a way to explain why energy seemed to be vanishing with beta decay. This created something of a panic, and German physicist Wolfgang Pauli proposed the neutrino as “a desperate remedy to save physics.” The notion of a particle that was incredibly penetrating, basically massless, and never observable was not too popular among scientists at first. But it fixed everything.

“Experiments made sense when viewed in the context of the neutrino,” Kofron said. “If you added the possibility that this little guy was carrying off all of the missing energy, all of a sudden the books balanced. From an experimental point of view, this was a real coup, this was a beautiful addition to the theory.”

More about Kofron’s work at the Center for Experimental Nuclear Physics and Astrophysics at UW.

Other books by Lee Smolin:

Brian Greene talks multiverses at Town Hall Seattle

If there’s such a thing as a celebrity theoretical physicist, Brian Greene is it, and he packed the city’s premiere lecture hall at Town Hall Seattle Wednesday evening for a talk titled, “Is Ours the Only Universe?” The talk helped sell many copies of Greene’s latest book, The Hidden Reality: Parallel Universes and the Deep Laws of the Cosmos, and likely also led to a spike in aspirin sales as many of us, whose ideas of parallel universes are limited to evil Spock with a beard, tried to recover from getting our heads around quantum mechanics, general relativity, string theory, and the notion of exact copies of ourselves a cajillion light years away pondering the same concepts.

Greene noted that parallel universes are something of a logical progression of the Copernican revolution that started when Copernicus suggested that the Earth was not at the center of the universe.

“The ideas that we’re thinking about today suggest that even the universe is not the center of the universe,” Greene said. “The universe is not the center of a wider cosmic landscape that we call the multiverse.

“These are speculative ideas that we’re talking about here tonight,” he added. “We don’t know that this is true.”

Greene says a big part of the puzzle is that the Big Bang theory leaves out a key piece of information: Just what was the bang?

“The Big Bang theory doesn’t tell us what banged or how it banged or if it even banged,” he explained. “It only tells us that a split second after something occurred, the universe continued to expand and cool down allowing structures like stars and galaxies ultimately to coalesce. We’ve been trying to fill in what happened at the beginning; what the bang was.”

One theory posits that powerful repulsive gravity many have triggered many outbursts, so that the Big Bang was not a unique event.

“Our universe would be the aftermath of one of those big bangs, but other universes could be the outcomes of their big bangs,” Greene said. “This is known as the inflationary multiverse and it’s one of the ways in which our universe could possibly be one of many.”

Another fascinating theory is that there may be infinite numbers of universes with exact copies of us out there. It’s called the Quilted Multiverse.

Brian Greene spoke at Town Hall Seattle Feb. 2.

“In any finite region of space there can only be a finite amount of matter,” Greene explained. “In fact, by a little bit of quantum mechanics, there only are finitely many distinct configurations that that matter can assume.”

He used a deck of cards as an example. There are only so many cards, so if you keep shuffling long enough, the same arrangement of the deck is bound to repeat. Apply the same logic to the universe.

“If space goes on infinitely far, then the configurations of matter have to repeat too, because there are only finitely many different configurations that are possible,” Greene argued.

“If the configurations of particles of matter agree here and in some distant region, what would that mean? Well, we here are just a configuration of particles. We just are particles that make up you and me and everyone else in this room. So, if the particle configuration repeats out there, then we are out there. Copies of us are out there. In fact, if space goes on infinitely farther, infinitely many copies of us are out there in rooms like this having this conversation.”

It all depends on the assumption that space is infinite, and that quantum mechanics applies in the same way in the far reaches.

String theory started to gain momentum during the 1990s.

“The big puzzle for many, many years was that gravity as described by Einstein’s general relativity proves incompatible with the mathematics of quantum physics,” Greene said. “It’s as if you have one set of laws that work for stars and galaxies, another set of laws that do work well for molecules, atoms, and subatomic particles, but any time these two laws come together, the math just falls apart and becomes inconsistent.”

Many scientists assail the concept as unprovable. Greene says the math works.

“There’s no experimental evidence for string theory at all,” he said. “Zero. The reason we have some confidence that this is an interesting idea to pursue is because we believe in quantum mechanics; that is unassailable. We believe in the general theory of relativity; that is unassailable. We believe that the universe has to be governed by a consistent set of laws. Without string theory, quantum mechanics and general relativity are inconsistent. For us, that’s a very powerful reason for believing string theory may be going in the right direction, because it makes them compatible. That is no small feat.”

It was an interesting and thought-provoking evening with a celebrity theoretical physicist.