Sunday, October 27, 2013

Where Are All the Aliens?

Saturday, at the request of Jill Tarter (for many years, the leader of the major program to search for radio signals from alien civilizations), I spoke to a group at the California Academy of Sciences about what we call the Fermi Paradox. Perhaps you will agree with me that it's one of the most interesting dilemmas in astronomy.

In the 1950's, physicist Enrico Fermi posed a question to some lunch-time companions, which we can sum up in modern terms this way: There are more than 200 billion stars in our Galaxy and Kepler mission results show that many of them have planets.  The Sun and its family are relatively young compared to the Galaxy (5 billion years old versus 13 billion years old).  So there must have been many stars and planets that developed long before ours did.

If so, life (and intelligent life) should have evolved on some of these worlds long before it did on Earth.  There must therefore be many civilizations out there whose technology is far in advance of ours.  In that case, Fermi and others have asked, where are they?  Why have we not found any signals, artifacts, or visitors from these extra-terrestrial civilizations?

The answer most scientists would give is that the stars are far away, travel among them is slow or expensive, and we have just begun to search for complex signals the aliens might be putting out.  Therefore it's much too soon to ask Fermi's question.

But scientists and science fiction author have delighted in finding other answers as well. Maybe the aliens (like your crotchety uncle) don't like to travel or write letters. Maybe they are so happy playing with their equivalent to Facebook, they don't need to find neighbors among the stars. Maybe they communicate in ways we have yet to dream of.

Or maybe they are here, but are too smart to let us see them watching us (sometimes this is called the "zoo hypothesis.")  Another answer is that while planets are common, perhaps the evolution of technology is very rare, making communication rare too.  What if alien species are more like the dolphins, swimming in a planetary ocean and reciting complex poems to one another?  But they don't mine metals or build telescopes and radio transmitters.

A really depressing proposal is that once aliens develop intelligence and technology, they also develop the ability to destroy their planetary environment through pollution or nuclear war.  A clever science fiction story that develops this further, "The Fermi Paradox is our Business Model" by Charlie Jane Anders, can be found free on the web at:

Many articles and books have been devoted to the Fermi Paradox.  Scientists enjoy such speculations, but eventually we come back to the notion that in science, the ultimate way to judge what is true is doing an experiment or making an observation.  Those scientists who continue the patient, long-term search for signals or other evidence of extraterrestrial intelligence do so in part because the discovery of another intelligent species in the universe might be the best answer we can give to Fermi's question.

Wednesday, October 23, 2013

Triple Asteroid Seen More Clearly

I remember the excitement in 1993, when a photo from the Galileo spacecraft, going through the asteroid belt on its way to Jupiter, unexpectedly showed that the asteroid Ida had a tiny moon orbiting it. Twenty years later, we now know more than 160 moons orbiting different asteroids. (Asteroids are chunks of rock orbiting the Sun -- pieces of cosmic garbage left over from the messy period when the planets first formed.)

At least five asteroids are now known to have two moons each, making them triple systems. Perhaps the most famous of these is the asteroid Sylvia, named after Rhea Silvia, the mother of Romulus and Remus, founders of the city of Rome in ancient mythology. Sylvia is one of the larger objects in the main asteroid belt, which lies between Mars and Jupiter.

Recently, a team of professional and amateur astronomers, led by Franck Marchis of the SETI Institute (where I have the pleasure of serving on the Board of Trustees) has made the most accurate measurement so far of Sylvia and its two moons (which got named Romulus and Remus). Our painting shows you what the system may look like if you could get up close and personal with it.

This past January, European observers could see the triple asteroid pass in front of a faint star, hiding its light as each object moved in formation. From this, the astronomers could make estimates and models of the size and shape of each member of the triple system, even though it orbits some 325 million miles from the Sun.

For more details, you can see the announcement at:

The very first moon discovered around an asteroid was soon named Dactyl, a term that can mean finger, or a small finger-like creature in Greek mythology, or a small unit of poetic verse.  To keep up with all the moons of asteroids, you can check the website:

Ida and Dactyl (NASA)

Sunday, October 13, 2013

A Matter of "Gravity"

The new space-disaster movie "Gravity" is very much in the spotlight these days. Astronomer Neil deGrasse Tyson, whose articulate and good-humored commentary is justly earning him the title of America's public astronomer (a title Carl Sagan used to hold,) recently found some problems with the science in the film and it caused a stir. But two other astronomer-writers have done an even more detailed analysis of what is right and what is wrong with the film.

Before I send you to the web pages where the analysis can be found, let me urge you to see and enjoy the movie first. Those of you with some science background, see if you can spot what is so well done and what is not quite right with the science. Everyone else, please go and enjoy the 3-D spectacle. Then you can come back and read about the issues with the science.

Phil Plait, the "Bad Astronomy" webmaster, gives his articulate analysis at:

Jeffrey Kluger discusses the film's pluses and minuses for Time Magazine at:

Neil Tyson's tweets and a response from astronomer Kevin Grazier, the science advisor for the film (and a number of TV shows) can be found summarized at:

As for me, I am always happy when film blockbusters get kids and the public thinking about things beyond the Earth. Some of my favorite films that have good science ideas to recommend them include "2001," "Contact (where Jodi Foster's character was based in part on one of my favorite astronomers, Jill Tarter), and the older (and more philosophical) "Five Millions Years to Earth." 

And I heard it from astronomer Fred Hoyle that the old British horror movie "Dead of Night" was one of the contributing inspirations to the steady-state theory of the universe that he and Hermann Bondi came up with (together with Thomas Gold.)  Hoyle and Bondi saw the film (which has no real beginning or ending -- watch it to see what I mean) and asked themselves, "Could the universe be like this?"

Wednesday, October 9, 2013

The Nobel Prize and the Higgs Boson

As you may have read or heard, the Nobel Prize in physics was just announced, and it went to two of the physicists who came up with the idea of the Higgs boson (and the Higgs field). I wrote a post explaining this subject when the experiments were announced last year. Since we have many new readers on this page, I thought it might be useful to review what this Higgs business is about:

Scientists working with the atom smasher called the Large Hadron Collider in Europe announced in July of 2012 the 99% likelihood of the discovery of the Higgs boson. It was big news in the realm of the fundamental particles, forces, and energies that govern the universe (although it has few immediate practical applications.)

Physicist Leon Lederman, some years ago, was writing a popular book about the ideas behind the Higgs boson and he wanted to call it the "goddamn" particle (because it was so complex and abstract). The decencies of publishing required that he and his publisher change the name to the "God Particle" -- which became the name of his book and the name that stuck to the Higgs boson, somewhat to the regret of scientists.

The important idea behind the particle is the Higgs field, which is a kind of low-level universal energy that gives particles their property of MASS. Mass, in turn, is what then allows particles to attract each other, clump together, and make stars, planets, and Facebook readers. The Higgs boson is evidence that the Higgs Field is real. (The term boson by the way is not a reference to a 1950's TV clown, but to Satyendra Nath Bose, an Indian-born mathematical physicist, after whom a whole class of particles is named.)

The Higgs boson shows itself only under very energetic conditions -- it existed when the universe was extremely young and hot, soon after the Big Bang. This is why it takes very energetic collisions in a large atom smashers to produce the particle today and why it took so long for us to gather evidence of its existence. If the Higgs boson can be observed in our atom smashers, it's pretty good proof that there is a Higgs field in the universe. That, in turn, is one more powerful supporting "pier" for the "standard model" of particles and forces that underlies our understanding of the natural world.

Professor Peter Higgs -- after whom the field and particle are named -- is 84 years old and so there was a lot of (appropriate) pressure in physics to make sure he receives the Nobel Prize now. (The Nobel committee cannot, by the rules of the prize, give it to anyone posthumously.)

For further non-technical introductions to Higgs bosons, I recommend:

A cartoon animation: Higgs Boson Explained:

An analogy for Higgs Field using everyday materials with science writer Ian Sample:

Saturday, October 5, 2013

Galaxy Cluster Abell 1689 Breaks Two World Records

A huge cluster of galaxies so far away that light from it takes 2.2 billion years to reach us has revealed itself to be a record-breaker. It has the largest number of star clusters ever seen in one place and it is farthest place in the universe where we have seen star clusters.

To appreciate this story, you have to distinguish between the two kinds of clusters we're discussing. Stars are often born in groups called "star clusters" and the largest and most impressive of these are called "globular clusters" (because their stars are organized into a big globe-shaped collection of 100,000 stars or more.) Our Milky Way Galaxy has about 150 of these globular clusters and they are among the oldest and most crowded places in our home galaxy.

Galaxies -- the great islands of billions of stars -- also turn out to be organized into clusters. Each cluster might contain hundreds or even thousands of galaxies. (And each galaxy contains billions of stars -- it makes you dizzy if you think too hard about it!)

The late George Abell (an astronomer at UCLA and the author of a famous textbook from which astronomers in my generation first learned astronomy) made a catalog of these galaxy clusters, and the one we are discussing is entry 1689 in his catalog.

A new study of the central region of Abell 1689, made with the Hubble Space Telescope, reveals 10,000 globular clusters of stars in a small region of the galaxy cluster. The astronomers who carried out the work estimate the throughout the entire galaxy cluster, there may be as many 160,000 of these giant old star clusters -- a record unequaled anywhere else we have looked so far.

At a distance of 2.2 billion lightyears, Abell 1689 is also the farthest location in the universe where we have seen a globular cluster.

In the attached picture, you can see part of the cluster of galaxies on the left and then a close-up where the globular clusters look like little yellow dots among the bigger galaxies.

For a scan through the galaxy cluster, you can check out this YouTube video:
(On this scan, you can also see faint rounded arcs of light -- those are direct proof of one of Einstein's ideas -- that the huge gravity of the galaxy cluster acts like a "gravitational lens" and bends the light of other galaxies behind it into arc like shapes.

We have seen other rich clusters bend light from objects behind them, but the effect is especially clear on this beautifully detailed image.