Category Archives: lectures

The expanding universe: discovery, controversies, and hope

We’ve known that there is a universe outside the Milky Way, and that it is expanding, for less than a century.

“Throughout the entire history of the universe, of knowing it’s expanding, there have been a tremendous number of controversies over it, and there’s still one that persists today,” said astrophysicist and author Ethan Siegel. Siegel, author of Beyond the Galaxy: How Humanity Looked Beyond Our Milky Way and Discovered the Entire Universe (World Scientific Publishing, 2015), spoke at last week’s meeting of the Rose City Astronomers in Portland, Oregon.

The controversy actually goes back to before the expansion was observed, to Albert Einstein. His equations describing general relativity suggested that gravity would collapse the universe onto itself, and as he believed the universe was static, he threw in a “cosmological constant” to push back against gravity. Einstein later called that his biggest blunder, though some wanted to let him off the hook for it when dark energy was proposed to do the exact same thing.

“I am here to tell you that this was Einstein’s reasoning and throwing this in there when he did was a super big blunder because the universe isn’t static,” Siegel said. Einstein should have trusted his theory, he said, and taken it to the next step.

The universe is expanding

By the 1920s Edwin Hubble observed a Cepheid variable star in the Andromeda “nebula” that indicated that it was far outside the Milky Way and a galaxy in its own right. Astronomers were also studying redshift as an indication for the speeds at which galaxies were receding from us. Siegel explained that through this, Hubble determined that the universe was expanding at a rate of 600km/sec/Mpc (kilometers per second per megaparsec.) This became the Hubble constant. But it wasn’t so constant.

Siegel noted that, knowing the size and expansion rate of the universe, you can figure its age by running the numbers in reverse and going back to the beginning, to the Big Bang. The resulting calculation determined that the universe was about two billion years old. Geologists at the time had already pegged the age of the Earth as at least four billion years.

“This was a problem for Hubble, because the universe isn’t allowed to be half the age of the Earth,” Siegel noted. “Either this expansion rate is wrong and this age for the universe is wrong, or the age of the Earth is wrong.”

It turns out that Hubble’s main mistake was in figuring that all variable stars are alike. Siegel said Walter Baade came along in the 1940s and discovered that they are not. Finding that most of the Cepheids Hubble had looked at were non-classical, they re-ran the numbers from Hubble’s data.

“As you accumulate more knowledge, as you accumulate a better understanding of what you’re actually loooking at, you can go back and get more useful science out of this data,” Siegel said. This second look doubled the distance to these stars and reduced the value for the Hubble constant to 270km/sec/Mpc. This in turn put the age of the universe at five billion years.

“That’s better,” Siegel noted. “The universe is older than Earth. That’s one problem solved.”

Narrowing it down

Siegel

Dr. Ethan Siegel, creator of the “Starts With a Bang” blog, gave a talk about the age and size of the universe to the Rose City Astronomers February 20. Photo: Greg Scheiderer.

As time went on astronomers developed the “distance ladder” for determining the vast distances in the universe. You first measured the distance to Cepheid variables within the Milky Way, then gauged the distances to other galaxies using Cepheids spotted there. Type 1a supernovae could be spotted really far out. As we learned more about the stars we got a little better at figuring distances.

Things got really interesting in the 1960s, according to Siegel. We discovered that we could determine the ages of stars by measuring their color and brightness. The Hertzsprung–Russell diagram told us that the oldest stars were between 14 billion and 16 billion years old, significantly older than the age of the universe determined by Baade. Astronomer Allan Sandage, who as a graduate student was an assistant to Hubble, came along and said you needed two things to make the universe that old: it had to be low enough in density to make a vast expansion, and the expansion rate had to be low.

Dueling Hubble constants

This, Siegel said, was where the controversy came in. Sandage said the expansion rate would have to be between 50-60km/sec/Mps. Rival astronomer Gérard de Vaucouleurs of France put it at around 100km/sec/Mpc. The race was on to make observations to see which group was right. Amazingly enough, each group’s observations matched up with what they thought the answer would be.

“This just goes to show that you cannot have the same people making the same measurements and trust them,” Siegel said. “This is why you need independent confirmation.”

It turns out Sandage and de Vaucouleurs were both wrong. There’s still no agreement on the right answer, but the disagreements are getting closer together. Sigel said the Hubble Space Telescope’s improvements in measuring the size of the universe return a value of 74±2km/sec/Mpc. The Planck mission’s observations of the cosmic microwave background radiation suggest 67±1km/sec/Mpc.

“There is a fight over the results like there always seems to be, because we are scientists and we cannot agree on anything,” Siegel said. “That is good, because questioning is what keeps us moving forward and what keeps us learning more.”

“The way we’re going to get there is with more and better data,” he added.

Better data

The better data will come from missions such as the European Space Agency’s Gaia, the James Webb Space Telescope, WFIRST, and the Large Synoptic Survey Telescope, which combined might improve our parallax measurements of cosmic distances by a factor of ten. We might also weed out faulty assumptions in the earlier work or get more accurate insights into the balance between matter and dark energy in the universe.

“If we can wait until the next decade, we might see that 74 number come down, we might also see the 67 number come up,” Siegel said. “The point is uncertainties are going to be reduced by more and better data.”

Siegel said that right now it’s pretty much agreed that the universe is about 13.8 billion years old and consists of about 30 percent matter and 70 percent dark energy. But the miniscule pluses or minuses can lead to huge fights.

“When that data comes in at last we will know exactly how fast our universe is expanding, how old it is, and what it all means for both our cosmic origins and our cosmic fate,” Siegel concluded. “That’s pretty good stuff.”


In the podcast linked below Siegel covers much of the topic matter of this article and his talk. His new book, Treknology: The Science of Star Trek from Tricorders to Warp Drive (Voyageur Press, 2017), is scheduled for release in October.

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Search for meaning continues

There is a great menu of interesting talks on this week’s calendar, including three with astronomy themes at a weekend event at Seattle University.

Search for Meaning FestivalSeattle University’s annual Search for Meaning Festival will be held on the university campus all day Saturday, February 25. The festival is a community event dedicated to topics surrounding the human quest for meaning and the characteristics of an ethical and well-lived life. It draws more than 50 authors and artists who will give interactive presentations. Three of these sessions are on astronomy-related topics.

At 9 a.m. Father George Coyne, SJ, former director of the Vatican Observatory and author of Wayfarers in the Cosmos: The Human Quest for Meaning (Crossroad 2002), will discuss the history of the evolution of life in the cosmos. Coyne’s thesis is that this history may lead us to a deeper understanding of what many secular physicists say themselves about the cosmos: that a loving creator stands behind it.

At 10:45 a.m. Margot Lee Shetterly, author of the book Hidden Figures: The American Dream and the Untold Story of the Black Women Mathematicians Who Helped Win the Space Race (William Morrow, 2016), on which the current hit film is based, will give one of the keynote addresses at the festival. Shetterly will talk about race, gender, science, the history of technology, and much else. Reservations for Shetterly’s talk are sold out.

At 12:45 p.m. Marie Benedict, author of The Other Einstein (Sourcebooks Landmark, 2016), will explore the life of Mileva Maric, who was Albert Einstein’s first wife and a physicist herself, and the manner in which personal tragedy inspired Mileva’s possible role in the creation of Einstein’s “miracle year” theories.

Check our post from December previewing the festival, and look at the trailer video below. Tickets to the festival are $12.50 and are available online.

Siegel at Rose City

Author and astrophysicist Ethan Siegel will be the guest speaker at the monthly meeting of the Rose City Astronomers in Portland at 7:30 p.m. Monday, February 20. Siegel will talk about his book Beyond the Galaxy: How Humanity Looked Beyond Our Milky Way and Discovered the Entire Universe (World Scientific Publishing, 2015). He’ll examine the history of the expanding universe and detail, up until the present day, how cutting-edge science looks to determine, once and for all, exactly how the universe has been expanding for the entire history of the cosmos. Siegel is an informative and engaging speaker; check our recap of his talk from last year about gravitational wave astronomy.

AoT Seattle and an app for simulating the universe

AoT FebruaryAstronomy on Tap Seattle’s monthly get-together is set for 7 p.m. Wednesday, February 22 at Peddler Brewing Company in Ballard. Two guest speakers are planned. Dan Dixon, creator of Universe Sandbox² will give an introduction to the app, an accessible space simulator that allows you to ask fantastical what-if questions and see accurate and realistic results in real-time. It merges real-time gravity, climate, collision, and physical interactions to reveal the beauty of our universe and the fragility of our planet. University of Washington professor in astronomy and astrobiology Rory Barnes will talk about “Habitability of Planets in Complicated Systems.” It’s free, except for the beer.

TAS public night

Tacoma Astronomical SocietyThe Tacoma Astronomical Society plans one of its public nights for 7:30 p.m. Saturday, February 25 at the Fort Steilacoom campus of Pierce College. The indoor presentation will be about the zodiac. If the skies are clear they’ll set up the telescopes and take a look at what’s up.

Futures file

You can scout out future astronomy events on our calendar. We’ve recently added several events scheduled at the Museum of Flight, including:

Up in the sky

There will be an annular solar eclipse on Sunday, February 26, but you’ll have to be in South America or Africa to see it. This Week’s Sky at a Glance from Sky & Telescope magazine and The Sky This Week from Astronomy offer more observing highlights for the week.

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Threading the needle with Cassini at Saturn

The hugely successful Cassini mission to Saturn will come to a fiery end in September, and you can hardly blame NASA for going a little Star Trek on us.

Ron Hobbs

Ron Hobbs. Photo: Greg Scheiderer.

“We’re going somewhere where no spacecraft has ever gone before, into this region between the glorious rings of Saturn and the cloud tops of the planet,” said Ron Hobbs, a NASA Solar System Ambassador, at this month’s meeting of the Seattle Astronomical Society. After 22 orbits through the eye of that needle—a 2,500-kilometer-wide gap—they’ll splat Cassini into the planet and burn it up.

“Now that we’ve discovered that there’s at least one moon, and maybe several, that could have the conditions for life, it’s very important to not leave a derelict spacecraft orbiting around Saturn,” Hobbs noted. “One of the important things at the end of the solstice mission will be to dispose of the spacecraft.”

The second extended mission of Cassini was named solstice because it is almost the beginning of summer in Saturn’s northern hemisphere.

Let’s do science

Before they crash Cassini, they figured there was some time to do some great science in that place where no spacecraft has ever gone. Most importantly, they will get a better picture of the internal structure of Saturn and examine its ionosphere, inner radiation belts, and auroral region.

“This would have been worth sending a spacecraft to Saturn for just that measurement,” Hobbs said, noting that it is essentially what Juno is doing at Jupiter. They’ll also check out the particles of Saturn’s D ring at close range, and be able to better gauge the mass of the ring system, which will help pin down its age.

“I can’t wait for the pictures,” Hobbs added. “The pictures that come out of this mission are just going to be spectacular.”

Shooting the gap

Hobbs said NASA has been using interactions between Cassini and Saturn’s moon Titan to nudge the spacecraft’s orbit to where they want it to be.

“Titan is really the only object in Saturn orbit that has enough mass to allow it to do gravitational assists and re-direct its orbit,” he said. “That allows [Cassini] to change its orbit and change the plane of its orbit.”

Cassini orbits

This graphic shows the closest approaches, or periapses, of Cassini’s final two orbital phases.The ring-grazing orbits are shown in gray; grand finale orbits are shown in blue. The orange line shows the spacecraft’s final plunge into Saturn. Credit: NASA / Jet Propulsion Laboratory – Caltech

In late November a brush with Titan dropped Cassini’s perichron—the point closest to Saturn in its orbit around the planet—down to just outside the F ring. In April, another Titan flyby will drop that perichron down to between the D ring and Saturn’s cloud tops.

“That’s when it’s going to get really exciting,” Hobbs said. Cassini will do 22 “grand finale” orbits through the eye of this needle, each lasting six days, collecting science data until one final encounter with Titan puts the spacecraft on a trajectory to splat into the planet on September 15.

It’s amazing how much planning and politics went into all of this. Hobbs said the actual trajectories of the orbits for this grand finale were determined a little over three years ago. Ever since then there’s been a spirited discussion between scientists, engineers, and mission leaders about what science to do to get as much data as possible out of the final mission. That determination was just completed last month.

“The spacecraft drivers are now writing the code for these orbits,” Hobbs said. That will tell Cassini where to go and where to point its instruments to make the observations as planned.

A good ride

Hobbs noted that Cassini was launched in October 1997, and so will end its mission just shy of twenty years in space.

“Without a doubt it has been one of the most successful and audacious missions NASA and the international community have operated,” he said. “This is going to be one of the highlights of space exploration in the last couple of decades.”

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Kelly Beatty’s history of Pluto

The history of Pluto goes way back before it became a tiny twinkle in Clyde Tombaugh’s blink comparator. Kelly Beatty, a senior editor at Sky & Telescope magazine, told the story of Pluto in his keynote address Saturday at the annual banquet of the Seattle Astronomical Society.

Scheiderer and Beatty

Kelly Beatty, right, with Seattle Astronomy’s Greg Scheiderer at the annual banquet of the Seattle Astronomical Society January 28, 2017. Astronomy guys love their astronomy ties. Photo: Greg Scheiderer.

In a way, according to Beatty, the hunt for Pluto dates back to the late 1700s. The Titius–Bode law (since repealed) of the distances to the planets from the Sun worked well, with one exception: according to the law, there should be a planet between Mars and Jupiter. Thus a group of astronomers calling themselves the “celestial police,” led by Franz Xaver von Zach, set out to find this elusive object. They did it; on New Year’s Day, 1801, Giuseppe Piazzi discovered Ceres. It wasn’t long before Juno, Vesta, and Pallas we found. At first all four were labeled planets, but now they’re known as the four largest asteroids—and possibly the first celestial objects to be demoted in status.

Dumb, fool luck

Lowell blink comparator

Blink comparator used by Clyde Tombaugh at Lowell Observatory to discover Pluto. Photo: © User:Pretzelpaws / Wikimedia Commons / CC-BY-SA-3.0.

Later, because of irregularities in the motion of Uranus, astronomers predicted another planet out beyond its orbit. But even after the discovery of Neptune in 1846, anomalies remained. Percival Lowell and William Pickering predicted there was yet another planet beyond Neptune. The hunt was on for Planet X, and Pluto was finally discovered by Clyde Tombaugh in 1930. We soon learned that Pluto was pretty small, which lent some irony to its discovery.

“Pluto didn’t have any effect on Uranus and Neptune at all,” Beatty said. “It turns out that the mathematics were incorrect, the positional accuracy of those early observations was bad. There was no basis to the prediction whatsoever, and by dumb, fool luck Clyde found the planet Pluto that he had been seeking within about six degrees of the predicted position. Freakingly by accident.”

We didn’t know a whole lot about Pluto for a long time. The best photos we could get were fuzzy Hubble Space Telescope shots. Astronomers found methane ice on Pluto in 1976, and its moon Charon was discovered in 1978. Pluto’s atmosphere was discovered in 1988 when it occulted a star.

Pluto on thin ice

“In 1998 the bottom fell out of the pro-Pluto movement,” Beatty said. The beginning of the end was the discovery of another distant object in what we now call the Kuiper Belt. Astronomers figured that there had to be more out there than just Pluto, and we now know of more than 1,800 of them. Many of these objects are locked in a 3:2 orbital resonance with Neptune, just like Pluto.

“Not only is Pluto not alone, it’s not even unique in its orbit,” Beatty said. “Things did not look good for Pluto and its planet status.”

The International Astronomical Union (IAU) started hearing chatter that Pluto should not be a planet, and in 1999 it passed a resolution declaring that it still was. Brian Marsden, who headed the minor planet center of IAU, really wanted to classify Pluto as an asteroid, according to Beatty.

Then, in 2005, Eris was discovered. At the time it appeared to be bigger than Pluto, though we now know it is slightly smaller. It was bureaucracy that finally knocked Pluto off the planet list. Different committees at the IAU name planets and asteroids, so to decide to which committee to refer the new discovery for naming, they had to decide what it was. This led to the new definition of planet, under which neither Eris nor Pluto fall. The IAU declared Pluto to be a dwarf planet in 2006.

Beatty is not fond of the IAU definition of planet: an object that orbits the Sun, has enough mass to be round, and has “cleared the neighborhood of its orbit.”

“It’s a really stupid definition,” Beatty said, mostly because it’s hard to know the mass of faraway objects, and so the definition is difficult to apply. Plus he finds it puzzling that a dwarf planet is not a planet.

“We have dwarf stars which are considered stars.” he pointed out. “We have dwarf galaxies that are considered galaxies. A chihuahua is still a dog.”

New Horizons

Pluto

New Horizons close-up of Pluto, one of the first and most iconic images from the mission. Photo: NASA.

Planet or not, the New Horizons flyby of Pluto in 2015 gave us a ton of new information about it and its moons. Beatty shared numerous photos of and findings about Pluto from the mission. It’s mostly made of rock, and might have liquid water below its surface. The surface features are mostly hard-frozen water ice, with a little frozen nitrogen, methane, and carbon dioxide mixed in.

Most fascinating is evidence of geology happening right now in the form of flowing nitrogen ice.

“Pluto’s surface, against all odds, out in the frozen corner of the solar system,” Beatty marveled, “has flowing glaciers on it.”

The last of the Pluto data from New Horizons arrived on Earth back in October, but the mission isn’t over. The probe is headed out for a look at the Kuiper Belt object 2014 MU69, at which it will arrive on January 1, 2019.

Beatty said this great new data about Pluto was worth the wait.

“We finally know what this planet/dwarf planet/interesting world looks like,” he said. “It was a 30-year effort from the time the Pluto missions were first conceived until we finally got out there. Some of the people involved, like Alan Stern, were there every year of the way, and boy, what a rich reward they have for their efforts.”

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Start saving: flying to space with Blue Origin

If there’s any anti-science sentiment around these parts it wasn’t evident last Friday at Peddler Brewing Company in Ballard, where some 500 space enthusiasts packed the brewer’s beer garden—yes, we were sitting outside, in Seattle, in January—to hear from employees of Kent-based Blue Origin about the company’s latest testing and the prospects for an affordable ride to space any time soon. The event was the latest installment of Astronomy on Tap Seattle, organized by graduate students in astronomy at the University of Washington.

Blue Origin Folks

L-R Nicholas Patrick, Dan Kuchan, and Sarah Knights of Blue Origin after their presentation at Peddler Brewing Company. Astronomy on Tap photo: Brett Morris and Nicole Sanchez.

“Our ultimate mission is to have millions of people living and working in space,” said Sarah Knights, outreach coordinator at Blue Origin. “The way that we’re focused on that is to lower the cost of human spaceflight, and one of the ways to do that is to make vehicles reusable, so that’s our primary focus right now.”

Blue Origin’s current test vehicle is the New Shepard, a capsule and vertical takeoff/vertical landing rocket. It’s powered by the BE-3, for Blue Engine 3, which is fueled by liquid oxygen and liquid hydrogen and can deliver 110,000 pounds at full thrust. As suggested, the rocket blasts off, and then lands softly back on Earth.

“As it’s coming back down we can throttle it back to about twenty percent of its full throttle, so that means that as the propulsion module is coming down we can have an equal thrust-to-weight ratio, find the landing pad, and very gently set it down,” Knights explained.

Blue Origin safety test

Dan Kuchan, Product Development Team lead engineer on the New Glenn program at Blue Origin, said the most recent test of New Shepard, conducted in October, was of the vehicle’s full-envelope crew escape system.

“That means that if the rocket at some point decides that we can’t go to space today, the crew capsule can jettison itself and get out of Dodge,” Kuchan explained. It was the first such in-flight escape test for a space vehicle since 1965, during the Apollo program. Kuchan showed this video of the flight test during the presentation.

“That was an awesome test and it capped off the fifth flight and landing for that booster,” Kuchan said. “The system worked flawlessly.”

Astronauts soon

So far New Shepard has only flown without a crew, but they hope to have astronauts on board soon. That’s where Nicholas Patrick comes in. Patrick, a former NASA astronaut who flew on space shuttle missions for construction of the International Space Station, is now Blue Origin’s human integration architect.

“I’m responsible for worrying constantly about every aspect of flying on our spacecraft,” Patrick said. That includes everything from meeting rules and regulations, testing to make everything right, and every imaginable human factor.

They chose a capsule rather than a winged vehicle like the space shuttle partly for safety. The smaller capsule can get away from the booster quickly, as demonstrated in the video above. Patrick said it’s also a better way to travel.

“For those who are paying to ride aboard a New Shepard in the coming years this is a more authentic rocket flight experience than most other ways you could get to space,” he said.

The New Shepard capsule has big windows, the largest ever flown in space, and all passengers will have one of their own; there are no middle seats on New Shepard. Suborbital flights will last about eleven minutes, and passengers will be weightless for several minutes.

“We want to give them the best imaginable experience,” Patrick said. He showed this video animation of what a New Shepard flight will be like.

“That’s a New Shepard flight that we hope will be available to anybody who can get in and out of the capsule, who can tolerate the three Gs on ascent, and a little higher on descent,” Patrick said. “So start saving.”

At what cost?

How much to save is a question that Patrick said hasn’t yet been answered.

“Obviously everybody’s goal is to get this price down a long way,” he said. “We’re not going to get millions of people living and working in space by charging a quarter of a million or a hundred thousand dollars just for a suborbital flight.”

The question of when people will fly on New Shepard also hasn’t been answered.

“We’re not driven by that kind of schedule,” Patrick said. “We’re driven by our flight test program and the success or challenges we face in each of those tests.”

“What I can tell you is that I expect we’ll be flying people in the next year or two,” he added.

Kuchan noted that, in a way, New Shepard astronauts will be human guinea pigs.

“New Shepard and everything we’re doing, sending tourists into space, is all a way for us to practice and master landing a reusable rocket, and using it in a commercially viable way, so that over the next 50, 100, 200 years we can move civilization deeper into space,” Kuchan said.

Next steps: a bigger rocket

Blue Origin’s motto is gradatim ferociter—step by step, ferociously. The next step for the company is on the drawing board now: the New Glenn, which will get payloads into Earth orbit. The New Glenn will dwarf the New Shepard. While the latter is powered by one BE-3 engine that delivers 110,000 pounds of thrust, the New Glenn will have seven BE-4 engines that deliver 550,000 pounds of thrust each. That’s a lot of oomph. Again, there’s no totally firm timeline, but Kuchan said they’ve been asked to deliver the rocket by the end of the decade, and added that they plan to do so. It’s another step on the way to having millions of people living and working in space.

“Every single decision that gets made at Blue Origin is weighed against that ultimate goal,” Knights said.

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Do not miss this! Tyler Nordgren and solar eclipses

Tyler Nordgren wants to make sure that what happened to him as a nine-year-old astronomy nut doesn’t happen to you this summer.

Tyler Nordgren

Tyler Nordgren reads an excerpt from his book Sun Moon Earth during a presentation January 14, 2017 at Town Hall Seattle. Photo: Greg Scheiderer.

Nordgren, a professor of physics at the University of Redlands and author of Sun Moon Earth: The History of Solar Eclipses From Omens of Doom to Einstein and Exoplanets (Basic Books, 2016), talked at Town Hall Seattle earlier this month about the book and his work to educate the public about the total solar eclipse that will cross the United States on August 21, 2017.

As a kid Nordgren was passionate about astronomy and already knew he wanted to be an astronaut. He was living in Portland, Oregon in 1979 when a total solar eclipse passed right over his house.

“Because of the news warning us about looking at the Sun, I was sure that if I accidentally looked at the Sun during the eclipse, there were these special rays that would come out and burn my eyes,” he recalled. “So I hid in the house with the curtains drawn and I watched it on TV.”

He could tell the eclipse was happening because the house got really dark, but that was his one and only take-away from the event.

“One of the things that has driven me to work on this and to help promote this eclipse that is coming up this year is I don’t want to see another nine-year-old child out there having the experience that I did!” Nordgren said.

Good things come to those who wait

“It took me twenty years to eventually, finally see (a total solar eclipse) for myself,” Nordgren noted. He described what it’s like, the things that happen approaching and during totality, but said that he had an unexpected reaction to that first totality.

“As an astronomer, I know the mechanics of the celestial alignment, yet in this moment of totality, I fully understand the difference between knowledge and feeling,” he said. “When I finally, after 20 years, got a chance to see this for myself as a professional astronomer south of Budapest in Hungary in 1999, I swear the hair stood up on the back of my neck. It still remains the most amazing thing I have ever seen in the sky.”

“I could understand why generations of human beings would cower in fear at this,” he added, “and wonder, ‘When is the life-giving Sun going to come back?’”

Eclipse science

Nordgren described some of the stories different cultures cooked up to explain eclipses, and also discussed some of the science done during eclipses, including the determination, from spectra, that the Sun was largely made of hydrogen and contained some iron. Helium was discovered on the Sun 25 years before it was found on Earth. Perhaps the most famous science made possible by an eclipse was the determination that mass can indeed bend light waves, as predicted by Einstein’s theory of general relativity and measured during a solar eclipse in 1919. The media coverage turned Einstein from an obscure physicist into an icon.

“This is what made Einstein Einstein in the popular culture,” Nordgren said.

Do not miss this!

This August’s total solar eclipse will be the first to cross the United States from coast to coast since 1918. Nordgren, also an artist, has designed travel posters for many of the spots along the path of totality, and shared them as he talked about the path the eclipse will take. You can see, and buy, them on his website.

He pointed out that virtually everyone in the country will be able to see some degree of partial solar eclipse, but he urged us all not to settle and stay home just because there might be traffic.

“Do not miss this!” Nordgren urged.

“The difference between being inside and outside that path of totality is literally the difference between night and day,” he noted. “Inside totality, the sky goes black, the Sun turns dark, the stars come out, the corona is visible. Outside totality, yeah, it kinda gets sorta dark. Yeah, use your glasses. Yeah, there’s a bite taken out of the Sun. But it will pale in comparison to what you experience—not just what you see, but what you feel inside that path of totality.”

Nordgren said a good solar eclipse may be just the thing that we need.

“In difficult times, when, heaven knows, there have been lots of things that do not unite us, here is going to be a moment in which we are all united under the shadow of the Moon, and we will all be seeing this together,” he said. “This will become the most photographed, the most Tweeted, the most Instagrammed, the most shared group moment in the history of the world.”

“That’s what we have to look forward to this summer,” he concluded.


Further reading: Also check out our review of Sun Moon Earth, posted in December, and our article about Nordgren’s keynote address at the Seattle Astronomical Society annual banquet in 2014.

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Grinspoon: Earth in human hands

David Grinspoon himself wonders how an astrobiologist wound up writing a book about the human impact on Earth. Grinspoon, author of Earth in Human Hands: Shaping Our Planet’s Future (Grand Central Publishing, 2016), answered the question during a Science in the City lecture recently at Pacific Science Center.

David Grinspoon

Astrobiologist and author David Grinspoon talked about his new book, Earth in Human Hands, January 10 at the Pacific Science Center. Photo: Greg Scheiderer.

“I am struck by the unique strangeness of the present moment,” Grinspoon said, noting that we are at the controls, if not actually in control, as we enter a new epoch in human history. Some find the proposed name of Anthropocene—the age of humanity—a touch self-centered or self-aggrandizing, but Grinspoon feels it is a fitting moniker.

“It represents a recognizable turning point in geological history brought about by one species: anthropos,” he said. “Our growing acknowledgement of this inflection point can be a turning point in our ability to respond to the changes we’ve set in motion.”

In fact, Grinspoon finds it promising that there’s some recognition that we the people are a major factor in what is happening.

“We need to learn all that we can about how planets work so we can make the transition from inadvertently messing with Earth to thoughtfully, artfully, and constructively engaging with its great systems,” he said.

A long history of planetary change

Grinspoon noted that it’s always fruitful to take a close look at the long-term history of Earth.

“We are not the first species to come along and radically change the planet and cause problems for the rest of the biosphere,” he said. In fact, the first one was not nearly so clever as we are. About 2.5 billion years ago the humble cyanobacteria caused a terrible calamity.

“They transformed the planet, the most radical chemical transformation that our planet has ever experienced,” Grinspoon explained. “They flooded the atmosphere with a poison gas that spelled certain doom for most of the other species that were living on the planet at that time.”

What they learned to do was photosynthesis, and the poison gas they spewed was oxygen. The oxygen also destroyed much of the warming methane in the atmosphere of the time, which led to a global glaciation that turned Earth into a giant snowball, a condition that lasted until volcanoes pumped out enough carbon dioxide to warm the planet up again.

“Cyanobacteria presumably never discussed that fact that they were starting to ruin the world,” Grinspoon quipped.

Four types of change

Grinspoon identifies four broad types of planetary change:

  • Random
  • Biological
  • Inadvertent
  • Intentional

The classic example of the random is an asteroid strike, something that just happens that there’s little control over. The cyanobacteria fall under the biological change. We’re in the midst of great inadvertent change right now, with automobiles, population growth and other factors driving a spike in carbon dioxide levels that began in the 1950s.

We’ve barely dipped our toes into the intentional. Grinspoon explained that our first stab at intentional change came with regard to fixing the hole in Earth’s ozone layer. The solution came from scientists studying Venus and trying to explain the planet’s lack of oxygen. They realized that chlorine destroys oxygen and ozone. Other scientists connected the dots and concluded that chlorofluorocarbons in refrigerants, propellants, and other products on Earth were eating away at our planet’s ozone layer.

Fixing the ozone

Interestingly, Grinspoon noted that this created an argument that may sound familiar. Some called the notion a hoax, there were attempts to discredit it, opposing “science” was created, and there was lengthy debate.

“The truth won out,” Grinspoon said. A global agreement was reached: the Montreal Protocol. Alternate chemicals were developed that didn’t deplete the ozone. Grinspoon said it’s working.

“It’s still going to be another fifty years or so because it takes time for the ozone layer to come back,” he said. “The natural chemical reactions that re-create ozone take fifty to one hundred years.”

“Assuming we stay on track, this is actually a success story, and it’s an existence proof that this kind of global change is possible,” Grinspoon added. “Not that it’s easy, and there are some ways in which fixing global warming will be inherently harder than this, but it shows that we are capable of a different approach.”

Thinking long term

While global warming is an important challenge, Grinspoon said it is a relatively short-term one, and that we need to think even further down the road. He said such random events as asteroid strikes don’t have to happen.

“We have a space program; the dinosaurs didn’t, and look what happened to them!” he quipped. We know how to identify possible threats and have a pretty good idea about what to do when they occur.

Further, Grinspoon said that we have an illusion that climate is always more-or-less fine, only because we’ve been lucky enough to live in a time of relative stability. We need to think about the next ice age, which he said will eventually occur.

“If we get over the near-term climate harm that we’re doing, we will have the knowledge that will allow us, when the need arises—we’re talking 10,000 or maybe even as much as 50,000 years in the future—we’ll have the ability to interrupt that cycle of ice ages and preserve the relatively benign climate, not just for ourselves but for other species as well,” Grinspoon said.

Who is out there?

All of this allowed Grinspoon to put on his astrobiologist hat and talk a little about the search for extra-terrestrial intelligence (SETI).

“When you do the math of SETI what you realize is that the question of is there anybody out there to talk to comes down to the question of longevity,” he said. “You can show this mathematically, that if civilizations last for a long time—that is, if this problem is soluble of how to create a stable technological civilization and use technology in the service of survival rather than self destruction—if that’s possible to do and if it happens on other planets, then there ought to be other civilizations out there that we could discover and maybe even communicate with.”

Thus the Anthropocene epoch represents something of a turning point. There are those who regard it as doom and gloom, as something we can’t beat, but Grinspoon doesn’t see it that way.

“The true Anthropocene is something that should be welcomed,” he said. “Though it is yet only in its infancy, it can be glimpsed. Don’t fear it; learn to shape it.”

“It is the awareness of ourselves as geological change agents that, once propagated and integrated, will provide us with the capacity to avoid doom and take our future into our own hands,” Grinspoon concluded.


Books by David Grinspoon:

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