Thursday, November 20, 2014

The Movie Interstellar: The Science Behind the Story

Lots of my students are asking questions about the new film Interstellar.  I have been hearing about the movie for some time; the studio even sent me a “teachers’ guide” that was not especially useful, but piqued my interest.  Most exciting for me was the news that the scientific advisor (and one of the producers of the film) was Prof. Kip Thorne of Caltech, who is arguably the world’s expert on black holes and wormholes -- and designed the science behind the “galactic subway system” in Carl Sagan’s novel and film Contact.

I wrote to Dr. Thorne and he told me that he had indeed been involved with Interstellar, and had, in fact written a book, entitled The Science of Interstellar, to explain the complicated science that was the basis for some of the more intriguing scenes and events in the film.   The book also tells the story of the film, which was always supposed to be strong on science, and, at one time, was set to be directed by Stephen Spielberg.  But that original deal fell apart and it took a while to bring Christopher Nolan, the film’s current director, into the project.

Dr. Thorne wasn’t the only scientist involved in the long period before the movie went from an idea to a completed production.  Yesterday, I was talking with Dr. Frank Drake, the father of the scientific search for extra-terrestrial intelligence, and he told me that he was on one of the early panels of scientists brought together (with Stephen Spielberg) to make sure the plot stayed close to real science and possible science.

With Christopher Nolan and his brother Jonathan (a writer of screenplays) involved, the film evolved from the script Dr.Thorne and producer Lynda Obst had first envisioned, to include much more about a future Earth facing ecological disaster.  Still, the original thought, to portray black holes and worm holes as accurately as modern science can make it, was high on everyone’s list of priorities.

A black hole is a place where the death and collapse of a huge star has produced such strong gravity, that space itself is “warped” -- and nothing, not even light can escape.  Near a black hole, time proceeds more slowly than in the rest of the universe, and this change in the flow of time becomes a major plot element in the movie.  Both the existence of black holes and their strange effect on time have been demonstrated by many experiments and are well established.

A wormhole is more speculative, but something Einstein himself thought a bit about.   It’s a place where a black hole or some other unusual feature of space and time becomes a tunnel (or short cut) from one place in space to another place very far away, or even to another time.  In a wormhole, the dangerous effects you would feel falling into a black hole are somehow kept at bay, so that a spaceship can go through it to elsewhere or elsewhen.

Both wormholes and black holes get major roles in Interstellar.  The astronauts in the movie first use a wormhole to get from our Milky Way Galaxy to another galaxy far far away.   Then, they wind up in the new galaxy in a location where there is a massive, spinning black hole, with planets around it.  I won’t give anything else away, except to say that the special effects showing the wormhole and the gargantuan black hole were composed from calculations made by Dr. Thorne and his team at Caltech, fed directly to the computers of the special effects team for the movie – and they are truly SPECTACULAR.

For more, I recommend reading Dr. Thorne’s book (pictured in this post) and going to see the movie – especially if you are a black hole fan.  Dr. Thorne also has a web page with some animations at:

Monday, November 10, 2014

Landing on a Comet: High Adventure in Space

This Wednesday, a European landing craft called "Philae" will attempt humanity's first landing on a fast-moving comet (a complex chunk of ice approaching from the depths of space.)

After a 10-year, 4-billion mile journey to Comet Churyumov-Gerasimenko (C-G for short), the Rosetta spacecraft (which is now orbiting the comet) will drop a probe about the size of a kitchen range from a height of 13 miles.  Taking some 7 hours to slowly land on its icy target, Philae will be moving at only 2 miles per hour at the end.  Still, the gravity of the two-mile wide comet is so low, it could bounce off and move away or simply fall over and roll.   To prevent this, the designers have equipped Philae with harpoons to grab the comet and with legs that have rotating screws in them to hold on to the ice for dear life.

Our robot representatives have only landed on six worlds so far: the Moon, Mars, Venus, Saturn's moon Titan, and two asteroids.  None of those landings were quite as difficult and strange as this one.  It takes radio signals from Rosetta about half an hour to get back to Earth even at the speed of light.  Thus the European Space Agency controllers can't help Philae if it gets into trouble.  Its own computer software will have to make the decisions that will lead to its survival or loss. 

For a complete picture of Comet C-G, see my August 6 post.  The photo accompanying today's post is a fantasy montage, showing the Philae lander safely on the comet's icy, boulder-strewn surface.  The full comet has a weird L-shaped structure, as if two oval comets had somehow stuck together at a weird angle. Because its shape is so complex, its gravity is not simple either, making landing even more challenging. But if Philae lands, its 10 instruments will give us our first-ever up-close look at one of the chunks of ancient ice that are building blocks left over from the early days of our solar system. 

Keep your fingers and toes crossed that the landing succeeds.  For a basic animation of what the spacecraft will do and what instruments it carries, please see:  

A fuller documentary about the Rosetta mission, see: 

Sunday, October 26, 2014

A Dark Spot on the Sun Seething with Energy

Many of you in North America who saw the partial eclipse of the Sun last Thursday may have noticed a nice dark spot under the eclipsed part of the Sun.  The full "active region" (that the visible spot is part of) is bigger in area than the giant planet Jupiter and has become the largest such feature on the Sun in 24 years.

With the kind permission of the photographers, I am posting here a beautiful close-up of the area, by Randall Shivak and Alan Friedman.  Look how wonderfully complex it is!

The darker regions on the Sun are called sunspots; they look darker because they are slightly cooler than the Sun's visible surface layer. The Sun is made entirely of seething hot gas, where the atoms are so hot, they easily lose their electrons.  This makes our Sun highly magnetic, and as it spins, its magnetic zones get all twisted up.  It's those twisted regions that appear to us as active regions.

Astronomers have already observed some "flares" -- sudden releases of extra energy -- from this region, but they haven't been sent in our direction in space.  The region is now facing the Earth as our Sun does its slow rotation.  So we may get some extra high -energy particles coming our way in days to come (or not -- weather from the Sun is as hard to predict as weather on Earth.)

For a nice movie of this region "crackling" with magnetic energy as the Sun rotates, see:

Wednesday, October 15, 2014

A Comet Passes by Mars; An Eclipse of the Sun


On Thursday afternoon, Oct. 23, there will be a partial eclipse of the Sun, visible from the U.S. Different amounts of the Sun's area will be covered by the Sun. (For example, 40% of the Sun will be covered from the San Francisco region.) I have put question-and-answer introductions to the eclipse at:

You can consult the national sheet for the degree the Sun will be eclipsed in your area. Here's wishing everyone clear skies. And please remember, do NOT look at the Sun without proper protection. Follow the instructions on the sheets or go to an astronomy place (observatory, college, planetarium) near you to join an eclipse viewing session.

This Sunday, Oct. 19th, a comet will pass closer to Mars, than any comet has passed to the Earth in recorded history. Comet Siding Spring (named after the observatory where it was discovered) will pass within only 87,000 miles of Mars. An armada of telescopes near Mars and Earth will try to get a good glimpse of it. From its orbit, this appears to be what you might call a "virgin" comet, making its first entry to the inner solar system. It is coming from the distant reservoir of ancient "icy chunks" that surround our solar system in a giant cloud.

A comet is just such an icy chunk that comes close enough to the Sun so that the Sun's energy and wind begin to evaporate the ice and loosen the dust frozen inside it for billions of years. These comets thus contain some of the original material from which our solar system was formed some 5 billion years ago. 

To learn more about NASA's plans for observing this Mars visitor, see:

For a while, NASA scientists worried that dust from the comet may damage some of the spacecraft around Mars, but recent calculations are showing that the path the comet is taking means that its dust is not likely to pose a serious threat.  But we'll see Sunday.  Perhaps there will be faint "shooting stars" (dust burning up in the thin atmosphere) on Mars.

Sunday, October 5, 2014

HBO is Showing "Einstein and Eddington" Now

In 2008, the BBC made a biopic (or dramatization) of events in Albert Einstein's and Arthur Eddington's life and work, and how they intersected. It was cosponsored by HBO and I just found out that HBO is currently showing this film (you can see it in the "On Demand" section of your cable TV offerings if you subscribe to HBO.) It may not last long, and it is not available on DVD yet in the U.S.

I recommend it with some enthusiasm (it's moving, and fun to watch), but also many reservations (the science and history are not always accurate, or -- to be charitable -- are twisted or changed in the interests of higher drama.)

I think everyone has heard of Einstein, but Arthur Eddington was an astronomer and physicist in England in the early part of the 20th century who contributed a lot to our understanding of how stars work. He was also a key member of the eclipse expedition in 1919 that tested if Einstein's crazy new theory of gravity, space, and time -- the general theory of relativity -- was correct. Measurements during that eclipse, and especially during a later eclipse made by a team from the Lick Observatory, established that Einstein was right and that the universe was more complex and beautiful in its inner workings than earlier scientists had imagined.

The film begins and ends around the eclipse expedition, but then goes back in time to set the scene. Many historical details are wrong or skipped over -- Elsa was divorced with two kids when she re-encountered Einstein in Berlin, the famous image of Einstein sticking out his tongue was later in his life, Eddington didn't have to tell Einstein about Mercury, etc. But such details don't matter to most viewers, and sometimes mixing things up a bit helps move the story along. And the flavor of the excitement around relativity is well characterized, with the two main actors doing a nice job in portraying the scientists and their personalities.

If you get HBO, or have a friend who does, and have a chance to see it, I recommend the film for everyone except historians of 20th century science, who will have a fit about those details. (The same production team also did a biopic about Stephen Hawking, called just "Hawking" and I gather you can find that film in segments on YouTube.)

Above you see the two scientists as portrayed in the movie, below you see the two of them from real life.
(For movie and TV fans, I can't resist adding: Gollum plays Einstein, Dr. Who plays Eddington.)

Sunday, September 28, 2014

A Baby Galaxy with a Grown-up Black Hole Inside

Using the Hubble and Gemini telescopes, astronomers have found a mystery --  a tiny galaxy that has a huge black hole in its center. That hungry black hole has eaten enough material to make 20 millions Suns!

The baby galaxy is really small -- its diameter is only 300 lightyears.  It's crowded in that little space; it contains about 140 million stars.  (Compare it with our Milky Way Galaxy, which stretches over 100,000 lightyears, and contains at least 200 billion stars.  Yet our central black hole has eaten only about 4 millions sun's worth of material.)  How could such a baby galaxy have such a big black hole?

Astronomers are no longer surprised to discover giant black holes at the centers of most galaxies.  Where a galaxy is most crowded (in its middle) is where a black hole (a star corpse with enormous gravity) has the most "food" to eat and can therefore grow.  But, in general, we have found that the larger a galaxy, the larger the monster black hole at its center.  So finding a baby galaxy sporting such a big black hole comes as a huge surprise.

A clue to this mystery comes from the name of the baby galaxy -- its awkward designation is "M60-UCD1."  UCD stands for ultra-compact dwarf (galaxy), which makes sense.   But M60 refers to the 60th entry in Charles Messier's catalog of fuzzy sky objects published in the 1780's.  That Messier catalog features some of the brightest and easiest to see galaxies and nebulae.   There is no way a tiny faint baby galaxy would have made his list!

It turns out that our baby galaxy is orbiting the much larger and brighter galaxy called M60.  In our picture, you see M60, a huge, blimp-shaped "grown-up" galaxy, which has its own super-massive black hole at the center.  You can see our baby galaxy in the inset of the photo. (You may need to click on the image to see it well.)

The fact that our baby galaxy is a "satellite" of the big galaxy may explain the mystery of its small size and big black hole.  The discoverers suggest that in the distant past, our baby was actually a big galaxy, with many more stars (explaining how it got its big black hole.)  But it had a "close encounter" with M60.  The gravity of the big galaxy stripped away its outer stars, leaving the "victim" of this encounter much smaller. 

If M60 took away and absorbed the outer layers of its neighbor, that would make M60 a cosmic cannibal.  That sounds awful, but in recent years astronomers have begun to realize that just about every big galaxy has grown to its present size by cannibalizing some of its smaller neighbors.  

It's a dog-eat-dog world out there among the galaxies, and the big bullies really get to throw their weight around.  Our little galaxy was once a more regular member of the galaxy club, but it lived in a rough neighborhood and got really beaten up by the local gravity bully.  Now it's a mere shadow of its former self.  

Sunday, September 21, 2014

Happy Fall Equinox on Monday and Other Sky Events

Monday morning (Sept. 22) is the "autumnal" or fall equinox for those of us in the Northern Hemisphere. On that day, the length of the day and the night are roughly the same ("equinox" means equal night). We are moving from the summer, when the days were longer, toward the winter when our nights are longer -- and our parts of the planet have fewer hours to heat up from sunlight.

The equinox is sometimes called the official start of fall and throughout history there have been festivals and beginnings celebrated at the time. It so happens that Foothill College, where I teach, starts its fall quarter on the equinox this year, so I will be welcoming several hundred new students to my classes with a happy equinox greeting (and many who don't know the term will be looking at me as if I were a crazy person!)

The fall quarter will bring many interesting events to fans of astronomy. Tonight, Sunday, the MAVEN spacecraft will be inserted into orbit around Mars, so it can begin to study how little Mars, with its lower gravity, lost its atmosphere over the millennia, and how its remaining air layers interact with the radiation and wind from the Sun.

October 8th, we will have a total eclipse of the Moon (these are much more common than total eclipses of the Sun.) Alas, for those of us in North America, this will be a middle of the night eclipse! The full Moon will go dark as the Earth's shadow falls on it, but most of us will be in bed, deeply asleep, when it happens. For example, in San Francisco, the eclipse happens from about 2:30 am to 5:30 am, so only dedicated night owls will be watching it. (If you miss it, don't worry, there will be two lunar eclipses visible in 2015.)

On October 19th, a newly discovered comet will come closer to the planet Mars than any known comet has come to Earth, and so our robot "representatives" around Mars will be keeping their cameras out for that pass.

On October 23rd, in the afternoon, much of North America will witness a partial eclipse of the Sun in the afternoon. Many astronomy organizations will be planning eclipse parties, with safe viewing options. I will do a full post about the eclipse when we get closer to the time.

And, down on Earth, October 25th, the opening day of the 2014 Bay Area Science Festival, I will be giving a free public talk on Mt. Tamalpais about the "Top Tourist Sights of the Solar System: Where Bill Gates' Great-Granddaughter will go for Her Honeymoon." See: