Tuesday, April 15, 2014

What Would the Lunar Eclipse Have Looked Like from the Moon?

We who live in North or South America (and had clear skies,) experienced a total eclipse of the Moon Tuesday morning, April 15.  But what would the eclipse have looked like to someone on the Moon?

First, since the Moon always keeps one side toward the Earth and one side away from the Earth, we have to pick a side. For this purpose, the interesting side of the Moon is the one that was facing the Earth and the Sun. It was sunny and bright on that side of the Moon before the eclipse began. Then, an observer on the Moon would have seen the Earth move in front of the Sun, and darkness descend. It would have gotten colder too without the warmth of the Sun.

Since the nearby Earth looks bigger from the Moon that the Sun does, the Earth more than covered the Sun. Still, the Earth's atmosphere bends some of the sunlight behind it toward the Moon. So someone on the Moon would have seen a faint ring of light around the dark Earth. (If you had a telescope on the Moon, you might also have seen the lights of big cities and large fires on the night side of our planet.)

How do we know that this "Moon perspective" about the eclipse is right? A Japanese spacecraft called Kaguya captured just this kind of image during a lunar eclipse in February 2009, as it was orbiting the Moon. In the picture above (courtesy of the Japanese Space Agency), you see several views of the Earth from the Moon during the eclipse. The ring of light is not complete, because some part of Earth was below the Moon's horizon as seen by Kaguya. At the end of the eclipse, you can see the first light of the Sun coming out from behind the Earth, making a kind of diamond ring effect. How wonderful that our robot spacecraft can give us views in the solar system that earlier scientists could only imagine!

Sunday, April 6, 2014

Apr. 14-15, 2014 Total Eclipse of the Moon Visible Throughout North America

I've put the information about this eclipse in question-and-answer format:

1. What Is Happening?

               Late on Monday evening and early Tuesday morning, Apr. 14-15, a total eclipse of the Moon will be visible from throughout the U.S.  In a lunar eclipse, the full Moon and the Sun are exactly opposite each other in our skies, and the Earth gets between them. This means that the Earth’s shadow falls on the Moon, darkening it.  (See the diagram above.) This will be a nicely democratic event; the eclipsed Moon will be high in the sky and easily visible (provided it’s not cloudy.)

2. When Will the Eclipse Happen?

Partial eclipse starts
10:58 pm
11:58 pm
12:58 am
1:58 am
Total eclipse starts
12:07 am
1:07 am
2:07 am
3:07 am
Total eclipse ends
1:25 am
2:25 am
3:25 am
4:25 am
Partial eclipse ends
2:33 am
3:33 am
4:33 am
5:33 am

As the shadow of the Earth slowly moves across the Moon, we first see only part of the Moon darkening (partial eclipse).  When the Earth’s shadow completely covers the Moon, we see a total eclipse, weather permitting.  

The best times to watch probably start a half hour before total eclipse starts, by which time a substantial part of the Moon is eclipsed.  The whole total phase lasts 78 minutes this time, and it looks pretty much the same the whole time, so only the most dedicate eclipse buffs will stay up for the whole thing.

3. What is Visible During a Lunar Eclipse

               As the shadow of the Earth covers the Moon, note that our natural satellite doesn’t become completely dark.  Light bent through the Earth’s atmosphere still reaches the shadowed Moon, and gives it a dull brown or reddish glow.  The exact color of the glow and its darkness depend on the “sooty-ness” of our atmosphere – how recently volcanoes have gone off and how much cloud cover, storm activity, and human pollution there is around the globe.

               Also, as the Moon becomes dark, other things in the night sky become easier to see.  As you look toward the southwest, you can see Mars to the right of the Moon, the bright star Spica just below and near it, and Saturn off to the left. Here is a nice diagram from Astronomy magazine (click to make it bigger). 

(Note that this is drawn for 3 am Central Time, which is 1 am Pacific Time.)

4. Is it Safe to Watch, and How do I Watch?

               Since the Moon is safe to look at and eclipses make the Moon darker, there’s no danger in watching the eclipse with your eyes or a telescope.  (The more dangerous eclipse is the solar one, where it is the Sun that gets covered.) Lunar eclipses don’t require you to have fancy equipment or to go to a dark location.  Bring binoculars, if you have them, to see the Moon larger, but just your eyes are fine.  Take someone along with whom you like to spend time in the dark!

5. What Can I Tell My Kids (or Kid Brother or Sister)?

               Suggest that they take a careful look at the shadow of the Earth as it moves across the bright face of the Moon.  What shape is it?  The round shape of the Earth's shadow suggested to the ancient Greeks, more than 2000 years ago, that the Earth’s shape must be round too.  Eclipse after eclipse, they saw that the Earth cast a round shadow, and deduced that we lived on a round planet (long before we had pictures from space.) 

Also, if kids have to miss this eclipse, you can console them by letting them know that there will be another total lunar eclipse on Oct. 8th, 2014 (and two more in 2015.)

Monday, March 31, 2014

Talk on the Work of and Crisis at Lick Observatory Now on YouTube

As you may have heard, the Lick Observatory (on whose Council I am now proud to serve) is being threatened by budget cuts at the University of California. Recently, Dr. Alex Filippenko (who was named the best professor at Berkeley a record nine times, and is a wonderful speaker) gave a very exciting talk on: "Exploding Stars, New Planets, Black Holes, and the Crisis at Lick Observatory". The video is now available on YouTube at

Lick Observatory, the first mountain-top telescope facility in the world, was founded in 1888, but continues to be a vibrant research facility and an important site for student and public education. Dr. Filippenko, who chairs the Lick Observatory Council, discusses some of the most exciting research being pursued at Lick, but also explains the funding crisis, what is being done by local citizens, and how you can help.

Today's image is a snapshot I took at Lick, showing Dr. Filippenko (left) with noted venture capitalist Jim Katzman, standing in front of the Katzman Automated Imaging Telescope. It was with the use of this telescope that astronomers discovered a number of special exploding stars in other galaxies that could be used as distance markers for the universe. That work led to the discovery of the accelerating expansion of the cosmos and won the two groups involved the 2011 Nobel Prize in Physics. We can't let them shut this facility down, folks!

Thursday, March 27, 2014

Two Major Discoveries about Our Solar System

Two major finds were announced yesterday: the first rings found around an asteroid, and the most distant object -- a dwarf planet -- ever seen in our solar system. Let me fill you in on the details.

The unexpected rings were found around the asteroid Chariklo, a 150-mile wide chunk that orbits between Saturn and Uranus. A group of South American astronomers observed Chariklo moving in front of a star, and glimpsed two thin rings around it. The rings are roughly 4 and 2 miles wide and are separated by a gap of some 5 1/2 miles. In the past, when we have found distinct thin rings like this, they have been kept thin by the presence of small "shepherding moons." The analogy is the shepherds keep a flock of sheep in a thin line, and these moons keep the particles of the rings from drifting away from their formation. So we expect that one or more such moons will eventually be found around Chariklo.

How did an asteroid get itself a set of rings -- which we have previously seen only around giant planets? Our best guess is that Chariklo was involved in some sort of cosmic accident and the rings are left-over debris from that event.

By the way, Harry Potter fans and mythology buffs will appreciate the name of the asteroid. In classical mythology, Chariklo was the wife of Chiron, the best known of the Centaurs -- creatures that were half human and half horse. In the same way, the Centaurs in our solar system are also half-breeds -- they have some characteristics of asteroids and some of comets.

The second discovery was of a dwarf planet orbiting so far away from the Earth and the Sun that it is the most distant world we have seen in our solar system. The small, frozen world, estimated to be about 250 miles wide, is called 2012 VP113, a boring provisional name that includes the date of its first sighting and letters and numbers that give a code for what its order is in the discovery of small objects that year. But because the letter code happens to be VP, the discoverers have nicknamed it Biden (but that will not be its final official name.)

I can't resist noting, in case you were not aware of this, that each vice president of the U.S. already has a direct connection to the world of astronomy, since the vice-president's residence is on the grounds of the U.S. Naval Observatory. Many vice-presidents brings guests to the observatory and even have parties there.

Little "Biden" (the world) is really, really out there, beyond what we think are the borders of the Kuiper Belt -- the zone of Pluto, other dwarf planets, and small icy chunks that make a belt outside the orbit of Neptune. The conventional wisdom has been that this belt should end at 50 times the distance between the Earth and the Sun (which we call 50 astronomical units), or about 4 1/2 billion miles from the Sun.

Biden, on the other hand, makes a looping orbit further out, and never gets closer to the Sun than 80 astronomical units or 7 1/2 billion miles. And most of the time is is even further out. (Another object found earlier, now called Sedna, is also out there.) The presence of such "far-out" members of our solar system, while not impossible, is surprising enough that astronomers are now set to pondering what got them out there.

Our image shows an artist's conception (no one has a photo of it) of what Chariklo and its two rings might look like out there, provided by the European Southern Observatory.

Sunday, March 23, 2014

A Guide to Science Fiction with Good Astronomy

Many people who love astronomy tend to look down on science fiction, criticizing it for not sticking to the real world. But many of these critics are really talking about science fiction movies and TV shows, and not about written science fiction stories. Like a number of astronomers (including the late Carl Sagan), I was influenced to become an astronomer by the science fiction stories I read.

As a way of saying thank you for all the wonderful reading I did (and still do), I now keep a web page that lists science fiction stories that include GOOD (sticking with the facts) astronomy. I've recently updated that guide, with more topics, more stories, and (for the first time) stories that you can read free on the web!

Some of the recommended stories are just a few pages, others are full novels or series. But if you enjoy reading about what's out there, and how humans might one day interact with the universe, I encourage you to check out the guide at the educational website of the Astronomical Society of the Pacific:

The photo accompanying this blog post was taken in 1989, during the Voyager spacecraft encounter with the planet Neptune. I was invited to the Jet Propulsion Laboratory to cover the event for the magazine I edited at the time, and posed between two of my favorite science fiction writers, Gregory Benford (left) and Fred Pohl (right).

Wednesday, March 19, 2014

Explaining the New Discovery about the Big Bang

As you may have heard, a large team of scientists (from many universities and labs) has used a telescope at the South Pole to make ground-breaking measurements of the very first instants oftime after the Big Bang. There's been a lot of media interest in the discovery, and this morning I was part of a team of scientists (including string theorist Brian Greene) who tried to explain the measurements and the ideas behind them on KQED's Forum program with Michael Krasny. You can hear the full hour at:http://www.kqed.org/a/forum/R201403190900

In the photo, you can see the Dark Sector Lab, a research facility just 3/4 of a mile from the Earth's South Pole. It was the antenna at left (BICEP2) that detected and measured microwaves that are the "afterglow" of the big bang.

For decades, physicists have explained some of the most intriguing large-scale properties of the universe by suggesting that, a tiny fraction of time after the big bang, the cosmos underwent a period of tremendous "inflation" (like blowing up a balloon with the breath of a million people, instead of just with your own lung-power.) That sudden increase in the size of the universe can help us to understand many things about cosmic conditions today, some 14 billion years after the big bang.

But did this "inflation" really happen? That's what the experiment at the South Pole set out to discover. If it did, it would have left very subtle imprints on the "cosmic background radiation" (the afterglow of the big bang) which today comes to us in the form of cool microwaves. (Cool here meaning less energetic waves than the light from the screen on which you are reading this post.)

The imprint of inflation was so delicate that it took several years of observations and even more years of massaging the data to tease it out of the microwave maps we make. One of the leaders of the team said during the show that the effect was 1 part in 30 million. But if it's confirmed by other experiments, this will stand as a milestone in our study of the universe. It's a remarkable wedding between the small scale world of atoms and waves (gravity waves making tiny ripples in the fabric of space-time) and the large-scale world of the entire universe.

It's one more piece of evidence that we now live at a time of "precision cosmology" -- being able to measure the properties of the entire cosmos with laboratory accuracy.

Saturday, March 15, 2014

Happy Belated Einstein's Birthday (Get Ready for Spring)

Yesterday was Albert Einstein's birthday and this coming Thursday will be the Spring Equinox, when the length of the day and the length of the night are roughly equal, and we move from winter to spring in the Earth's northern hemisphere. This is always a good time of year to think fresh thoughts, something Einstein was especially good at.

At Foothill College, where I have the privilege of teaching, this is the week we begin registering students and community members for our spring quarter, which starts in April. This spring, I get to teach my evening Physics 12 class, nicknamed "Everything You've Wanted to Know about Einstein and his Work (without Math) but Were Afraid to Ask..."

If you, or someone you know, might be interested and are close enough to Los Altos, California to come to an evening class, I invite you to check it out.

Although Einstein died in 1955, his work continues to capture the imagination of both scientists and the public. In the last few years, astronomers have found new confirmation of some of Einstein’s most bizarre ideas -- including time itself slowing down under the right circumstances and gravity acting like the distorting mirrors of an amusement park. Huge black holes have been found, some of them having “eaten” enough material to make billions of Suns.

In the Physics 12 course, we explain all these ideas and discoveries in everyday language -- using analogies, visuals, and humor instead of math. Physics 12 will be offered on Tuesday and Thursday evenings from 6 to 8:30 pm, April 8 to June 24, 2014. Pre-registration is advised, but, if there is room, you can come hear the first lecture (room 5015) and then register if you like the approach. The class is held on the main campus of Foothill College in Los Altos Hills, just off Freeway 280. (For adults who don't need a grade, arrangements can be made, after you register, to take the course without the exams.)

For registration information for the Spring Quarter see:

Physics 12 emphasizes key ideas that form the basis of our modern concepts of space, time, matter, and energy:
* The theory of how atoms work
* Energy, heat, and the arrow of time
* The special theory of relativity: what happens when you travel close to the speed of light
* The general theory of relativity: gravity, space-time warps, and black holes
* Quantum mechanics: the bizarre rules that govern the world inside the atom

In addition to examining the physics and physicists involved with these areas, the course also takes a brief look at the effects that such physics ideas have had on the humanities -- including poetry, fiction, music, and the public view of scientists. The quarter concludes the course with a non-technical introduction to the work of Stephen Hawking, whose innovative ideas combine these areas and take some of Einstein's ideas to the outermost limits of cosmic possibility.

For a course syllabus in pdf format, see:www.foothill.edu/physics/Physics.12.Web.pdf