Centuries ago the stars were believed to reside just beyond the planets of our solar system.It never fails to astound me how big the Universe is—how far away even the nearest stars are, let alone other galaxies scattered from here to near infinity….

How do we know how far away celestial objects are? This shouldn't be taken for granted, as it's not as straightforward as sounding the depth of the ocean floor with sonar, or determining the range to an object by bouncing radio waves off it and timing the reflection.

In fact, we have "pinged” the nearest celestial objects with radar to determine their distances very accurately. Examples are the Moon and Venus, where round-trip lightspeed travel is measured in seconds or minutes.

Before radar, the scale of the Solar System had to be determined geometrically, by observing events like Venus or Mercury transiting the face of the Sun from different locations on Earth and triangulating. Even this technique requires telescopes, which we've had only four hundred years. Before that, figuring out distances to just about everything except the Moon was mostly guesswork. In fact, it wasn't too many centuries ago that the entire Universe was believed to be not much larger than the Solar System—the Sun and it's nine…excuse me…eight planets—as we know it today.

Once the distance from Earth to the Sun was figured out, that length (the "Astronomical Unit”) in effect became a basic measuring rod for working out distances to everything else, by one means or another.

As Earth orbits the Sun, the direction from which we see stars shifts minutely, and we can observe a small change in a star's position compared to the more distant "background” stars. You can see the same effect by holding a finger in front of your face and looking at it alternately with one eye, then the other.

The geometry of this observation is a simple triangle, whose base is the distance between your eyeballs and whose legs are the lines from each eyeball to your finger. By knowing the length of the base, and observing the change in viewing angle against the background, the length of the legs (distance from your eyeballs) can be calculated.

In the case of Earth and a nearby star, the "eyeballs” are the Earth at two ends of its orbit around the Sun (six months apart) and the "finger” is the star.

But this measuring of distance by "trigonometric parallax," as it's called, only works for the nearest stars, as the minute shift in the star's apparent position diminishes with distance.

As astronomers learned more about the distance to nearby stars, they determined how to relate their temperature and mass to their actual brightness, and it became possible to estimate the distance of many stars by measuring their apparent brightness, with an understanding of how the brightness of light weakens with distance.

To measure the depths of space between us and galaxies far, far away, in which individual stars are indistinguishable from the overall galactic glow, we can turn to certain types of supernovae: individual stars that temporarily shine brightly enough to be observed and measured. Like the flare of a match struck in the dark night, the brilliance of the flash reveals how far away the striker stands.

We have built up our knowledge of the Universe's vastness over the past couple centuries, working out the problem from the near to the far. Even as science and technology have made the world on which we live smaller, it has done exactly the opposite to the Universe….

Searching for tadpoles in Arroyo Viejo Creek at the Oakland Zoo.

It Day #2 of Nature Play, a new Oakland Zoo ZooCamp program that I have been assigned to teach. I know all about “Nature Deficit Disorder” and “No Child Left Inside”. I have read “Last Child in the Woods” and even blogged about the issues, but now I find myself out in nature with 12 curious and excited children, and I have no idea what will happen.

Nature Play was created in response to childrens’ desire to experience true nature – to look up at trees, observe tadpoles and connect with wildlife in their own backyard. The idea behind Nature Play is to offer the campers supervised and loosely facilitated exploration outdoors that is self directed.

Parents were so game to give these simple pleasures to their children, this program sold out.

Now, here we are. Our afternoon agenda is creek time and fort building. It is a beautiful afternoon at Arroyo Viejo Creek, a small tributary that runs through the zoo grounds. Though there are tigers, lions and elephants close by, this is where the campers are most excited to be. I have given minimal direction: look, listen, smell and feel, and record something in your nature journal. They have nets, jars, binoculars and wildlife guides, and one hour.

Immediately the group swarms to their favorite spot that they discovered yesterday. It is near one of the outdoor classrooms and features a giant, ground-leaning willow tree to crawl under, two logs that rest across the creek to climb over and water loaded with tadpoles and water gliders. I watch and listen myself.

“There are 1000 water striders here! They are riding on top of each other.” “No, that is a shadow”. “I am crossing the log by scootching” “I will help you”. “I found a secret trail!” “I am putting this leaf in my journal”. “I can write with a rock.” “I heard a frog!” I am a frog!” “The sun makes me silly and happy.” “I see tadpoles!” “Let’s call this place Willow Cove.” “I don’t want to go home.”

A few things amazed me about this hour. One, they were never bored. They went on and on with their play and exploration in this small area with gusto the entire time. They were imaginative, inventive and stimulated. Two, they learned. They learned that frogs are quiet when they are noisy. They learned that they could balance better holding their arms out. They did not need my fascinating animal facts to gain knowledge. Three, they truly and intuitively cared about the habitat. They picked up a couple of pieces of garbage, told each other not to handle amphibians and put rocks back where they found them without being told. Four, and most interestingly, they got along fantastically. Earlier in the day there were a few squabbles over this or that, but out here, they helped each other, supported each other and shared the nets like pros. They seemed to be at peace.

A little later at Fort Building, the group divided into two as they followed two natural leaders and their fort visions. As we debriefed about the two forts, they came to the conclusion (themselves) that tomorrow they should build one fort with all the materials, then sit in it and tell stories about animals.

I saw it all with my own eyes. This nature stuff works. Now this explorer is going to sleep. I am exhausted!

(left) A cell imaged with an optical microscope. (right) The same cell imaged by allowing the cell to absorb UCNPs and then irradiating it with infrared light. Each nanocrystal is one thousand times smaller than the width of a human hair. Image courtesy of PNAS."Like a silent black mist, nanoparticles began to come into the room underneath the west door…Inside the room, the particles appeared to spin and swirl aimlessly, but I knew they would self-organize in a few moments."

Thus proceeds Michael Crichton's 2002 thriller, Prey, as the protagonists face off against a malicious swarm of flesh-hungry nano-robots that are the offspring of a most unholy marriage of biological, computer science, and engineering research efforts.

Real science capabilities lag somewhat behind, but researchers succeeded recently in demonstrating an exciting new class of nanoparticle with potential applications in biological imaging. The new crystals, more formally known as lanthanide-doped upconverting nanoparticles (UCNPs), were fabricated and studied under the direction of principle investigators Bruce Cohen and James Schuck at Lawrence Berkeley National Laboratory's Molecular Foundry, and results were published on June 18^th in a paper by Shiwei Wu and others in the Proceedings of the National Academy of Sciences (PNAS).

Happily, while Crichton's nanoparticles coordinated an attack on a your vital organs, these particles behave more like benign light bulbs. After allowing a living cell to absorb the UCNPs, researchers shine infrared laser light on the cell, and the nanocrystals within light up like a Christmas tree in red or green arrays of dots. These, in turn, can easily be spotted using an optical microscope and used to map out particle distributions within a cell, yielding information impossible to obtain by other methods.

The method, known as single-molecule imaging, has been demonstrated using other nanoparticle types, but UCNPs are unique because of their uncommon brightness and stability, and because they are powered by infrared light. This is both good for the studied cells, because infrared light is less damaging than visible or X-ray frequencies, and good for the people measuring them, because it can probe more deeply into tissue than other types of light. In fact, one prospect for future research is the imaging of entire animals.

Reflecting on the research effort's long-term goals, Cohen commented that cross-disciplinary sharing of ideas is crucial. "In general, we'd like to bring nanoscience to the larger scientific community, especially biology, where few researchers have had much exposure to it," he said. "Our goal is to make interesting and useful new materials that will let them do all sorts of experiments that would otherwise be impossible."

Are you using Twitter or other social media as a way to promote progressive causes like energy efficiency? What do you think about mandatory home energy audits or line drying clothes versus machine drying? Source image: Tina KellerSomebody close to me recently turned 50. Okay, it was me who just turned 50. My how things have changed since 1959! My first experience with computers was as a freshman lining up to hand over my punch cards to the computer operator to be fed into a computer that filled a room. Up until recently I got my news of the world through newspapers and television. For most of my life I stayed in touch with distant family and friends through letters and phone calls. When my brother was in Vietnam during the war we had to call him through short wave radio to tell him that his Corvette got smashed. (He didn't care. He was relieved that we were all okay.)

Now I get my information mostly off the Internet and through Twitter, the social media service that is in the news because of its use by the opposition parties in Iran. Twitter is like snail mail cubed. You send messages from your computer or smart phone that immediately show up on the computers or phones of all your "followers." You get followers generally by following others. It's kind of an unwritten rule that if someone is following you should return the favor. So far I am following about 30 people or groups and have 11 followers. But I just started.

I am following Energy Circle, a new Internet resource that is using social media to report news about home energy efficiency on Twitter. A recent "tweet" connected me to an article by Peggy in Toronto who thinks that mandatory home inspections should be replaced with mandatory energy audits upon the time of sale of a home. Advanced Energy's Research Director Melissa Malkin-Weber, tweeted "Energy saving smugness nixes scratchiness of air dried sheets. But don't ask my kids about how those stiff cloth diapers felt."

I agree with Peggie and Melissa. But what do you think about mandatory home energy audits or line drying clothes versus machine drying? Are you using social media as a way to promote progressive causes like energy efficiency? You can respond below, and your response needn't be limited, like "tweets" are, to 140 characters. Or sign up for a Twitter account and join the conversation at KQED Science!

Artist's depiction of a megalodon chasing two blue whales (image credit: Karen Carr, the Virginia Museum of Natural History)
Often I am drawn back to one place at the California Academy of Sciences, staring down at the dancing forms in the Lagoon's shallow water. Rays and sharks glide easily just above the tropical sand. Eventually, I see the lagoon’s shyer inhabitant, the guitarfish, whose body markings and shape resemble an upside down guitar. Sharks, ray, and guitarfish all belong to the subclass Elasmobranchii within the cartilaginous fish class Chondrichthyes. The Elasmobranchii also includes the infamous megalodon, thought to be the largest carnivorous fish ever to have existed. The megalodon was famed to reach lengths between 45 and 90 feet, dwarfing even today's most fearsome Great Whites.

What I find most interesting about this subclass is the body make-up these creatures share. They do not have a bony skeleton like humans; their skeleton is made up of cartilage—a dense connective tissue that is tough yet elastic. Their grace, speed, and great success as predators come from the fluidity of their movement.

This also makes it difficult for Ichthyologists to agree on taxonomy within this class as fossilized remains of cartilaginous fish are often poor. The oldest fossil on record of a megalodon, 18 million years old, is the only bone in the skeleton: a tooth. From the tooth, several researchers have tried to reconstruct the jaw and piece together what the body would look like. The tooth also suggests what this massive prehistoric shark preyed upon: There are bite marks on whales, dolphins, porpoises and sea turtles.

As the sharks, rays, and guitarfish pass by in the lagoon, I imagine the shadow of their giant cousin, the megalodon.

In a truly awful decision reminiscent of Gore vs. Bush, the Supreme Court has decided that there should be no federal mandate for genetic testing after someone has been convicted. Even though DNA evidence can free innocent people who were wrongfully accused. How absurd is this?

It is especially hard to understand when there is ample evidence that there are plenty of innocents in prison. And when a DNA test can prove so conclusive in showing their innocence.

A case I use in a high school activity (and which will be highlighted in the new Technology Benefiting Humanity exhibition at The Tech) involves Marvin Anderson. He is an African American who was convicted of rape by an all white jury in the South.

Court TV produced a great documentary that details all of the mistakes that sent Marvin to prison. And how the Virginia state government, much like our current Supreme Court, fought the simple DNA test that eventually proved his innocence.

Marvin was a suspect because he had a white girlfriend and the rapist had said that he had a white girlfriend during the attack. In a photo line up, Marvin’s was the only picture in color. Then, in the real line up, Marvin was the only man who had been shown in the photo line up.

Marvin’s lawyer represented the man who had really committed the crime. The trial lasted one day and as I said, Marvin was sent to jail by an all white jury. And while Marvin languished in prison, the real rapist confessed but the judge threw out the confession.

This is when the Innocence Project took up the case. The Innocence Project uses genetic testing to free innocent men and women. After hearing the details of Marvin’s case, they decided to help him clear his name. And it was not easy!

First off, they had to find the evidence from the case. This is often hard to do because evidence gets thrown away after a certain amount of time.

But, by a miraculous fluke, the Virginia government found the evidence from the rape kit… it had been saved in a lab notebook. So all that needed to be done was to see if the DNA from the crime scene matched Marvin's. If it didn’t, then Marvin most likely was innocent.

But the Virginia government would not allow the evidence to be tested. Apparently, just like the Supreme Court, procedure mattered more than innocence to the bureaucrats involved.

How many people like Marvin Anderson are waiting for the justice system to do the right thing?
Finally, in 2001, after Marvin had been in jail for 15 years and spent four years on parole, Virginia passed an Innocence Project backed statute that allowed DNA evidence to be tested in some cases. Marvin’s was the first evidence tested under the new statute. He was found to be innocent and the police were able to use the evidence to catch the real rapist.

If the Virginia government had not done the right thing, the real rapist would be free to continue committing crimes. And everyone would still see Marvin as a rapist.

There are undoubtedly Marvins rotting in jail in the three states that don’t allow for genetic testing after a conviction (Alaska, Oklahoma, and Massachusetts). And other Marvins are probably in those other states that only allow genetic testing in certain situations.

The Supreme Court could have given all of these innocent people the chance that Marvin finally got after 19 years. But five justices decided against doing that.

Now I suppose there is probably some legalese reason why the Supreme Court ruled that innocent people should stay locked up. But I am not lawyer enough to understand it. And neither are the Marvins still out there, waiting for justice.

This story marks the first time I've had to use a pseudynm to protect the identity of a horse.

"Disney's" owner's desire for privacy only underscores the stakes here. Performance horses at his level can be worth $60,000 and more. Training, too, is an enormous investment. "Gretchen," as we call her in the piece, has spent years training Disney in English dressage (which, incidentally, makes for some very entertaining YouTube viewing if you have some time to kill). And so when she noticed that her horse's gait had started to suffer, she jumped to find a treatment.

Speed is key here, it was explained to me, because the smaller the injury, the better a horse's chance for recovery. Emphasizing that point is one of the main reasons Gretchen agreed to take part in this program. She says too many owners treat their horses' injuries with ever-greater doses of painkillers, delaying real treatment until it's too late. Gretchen estimated that, including all the preliminary visits and tests, Disney's treatment may reach $7,000.

Davis vets couldn't provide statistics on whether this treatment - injecting a horse's mesenchymal stem cells, drawn from the marrow of the animal's sternum, into the same animal's torn tendon - succeeds in producing new tendon tissue. (Part of the problem is that it's hard to distinguish tendon tissue from scar tissue, seen through an ultrasound.) But if it works, they believe humans may one day have another option for treating our torn ligaments, too.

Listen to the Stem Cells and Horses radio report online, and watch our Web Extra Slideshow.

Mars as seen through Chabot Space & Science Center’s 20-inch telescope near the 2003 close encounter. Credit: Conrad Jung/Chabot Space & Science CenterIf you take away no other message from this blog, just remember this: the planet Mars is NOT passing close to Earth this August and will NOT appear as large as the Full Moon. There; disclaimer delivered.

As August approaches, the ghost of Mars returns to haunt us, in the form of emails and phone calls from people asking if it's true that Mars is about to get closer to Earth than it has been in a gazillion years—so close that it will look as big as the Full Moon.

I say "ghost" because it simply isn't true, here in 2009. I say "haunt" because, six years ago, it was true—at least, partly.

The time: August 27, 2003. The scene: Earth and Mars. The event: Mars is coming into opposition—the time when Earth passes directly between Mars and the Sun, and consequently Mars is closest to us and at the opposite point in the sky from the Sun—hence "opposition." A routine encounter, one that happens about every 2.2 years. But what's different with this Mars opposition is the distance between Earth and Mars at closest approach: the two planets are closer together than they have been in a very long time: a bit less than 35 million miles.

This was a very big deal, you may recall. We remember it very well at Chabot: On one of the evenings that weekend, we had 2000 people who came up to see Mars through our telescopes…. A close opposition is the best time to see a planet, and this was closer than average for Mars by maybe 10 million miles. (It was at another very close opposition of Mars when Percival Lowell made his famous "Martian canals" observations and Martian civilization hypothesis, back in 1894.)

At the time of the 2003 opposition, there were a lot of reports—emails, websites, blogs—flying around describing the event, in some cases with exaggeration. One exaggeration is the amount of time since the previous closest encounter with Earth. Different accounts suggested a thousand years, ten thousand years, even one hundred thousand years. Technically this may have been true, if one were calculating down to the inch. Practically speaking, however, the opposition in 1924 was almost as close, by a difference of only 12,000 miles (one and a half Earth diameters).

The other (gross) exaggeration was a statement made that at opposition Mars would appear as large as the Full Moon. That would be spectacular! However, at some point a piece of information was lost from the original message: the part about needing to look at Mars through a telescope to achieve the advertised view.

The final piece of information missing from that message—which gave birth to the annual Mars Hoax –was the year, 2003, omitted along the way and making every August 27th a day to view the splendor of Mars in all its glory. But, alas, the ghost of Mars.

For the record, the next extra-close opposition of Mars will occur on August 15th, 2050, when it will be only 200,000 miles farther than the 2003 near-miss….

Hydrogen is not exactly a fuel. That is, we don't burn it to make energy. It's used more as a medium for storing and transporting energy.

The science of hydrogen fuel cell systems is based on a simple concept. When you combine hydrogen with oxygen, energy is released. You get electricity. What makes it such a clean technology is that the byproducts of that chemical reaction are just heat and water.  So when a fuel cell takes hydrogen from a fuel tank and combines it with oxygen in the air, it produces electricity and emits only a wisp of heated water vapor from the tailpipe.

Hydrogen is combustible (remember the Hindenburg?), and needs to be handled carefully. However, there are easy ways to demonstrate electrolysis, which breaks water apart into oxygen and hydrogen, and the opposite process of joining those chemicals. In fact, you could make a type of fuel cell in your kitchen, with a popsicle stick, battery clips, Scotch tape and a few other household products. You do need one item that can't be found in your kitchen: platinum wire or platinum-coated nickel wire.

Hydrogen is the most abundant element in the universe. And hydrogen fuel cell conversion is a squeaky clean technology. But the production of hydrogen for use in fuel cells — that can produce a lot of carbon dioxide. In fact, most hydrogen is currently made by stripping, or re-forming, natural gas. That's one of the ongoing criticisms of fuel-cell technology, that it generates greenhouse gas emissions just to get the hydrogen in the first place.

Fuel cells also can store energy generated by solar-powered electrolysis, as well as similar energy generated by wind and hydropower. That's the kind of hydrogen generation that advocates hope to eventually use in fuel cells. But being able to store energy also makes it extremely attractive to harnessing wind, solar and hydropower.

For example, California could generate a lot of wind energy at night, but since electricity has to be used right away, that nighttime, offpeak energy is less valuable. But if it could be stored in a fuel cell through the electrolysis process, that would make it much more lucrative.

Listen to the Where's my Hydrogen Highway? radio report online, and watch our Web Extra Slideshow.

Which is worse for you, a can of tuna or a broken CFL bulb? Sorry, Charlie… image by Dave LifsonA paper expected to be published in the August issue of the lighting industry journal, LD+A, may quiet some of the controversy over the dangers of mercury in compact fluorescent lights (CFL). I’ve argued in this blog that the cut in mercury emissions from power plants due to the electricity saved when traditional incandescent bulbs are replaced with CFLs, greatly outweighs the amount of mercury that could escape from broken CFLs, plus what is emitted during the making and transportation of CFLs. But the paper, by Robert Clear, Francis Rubinstein, and Jack Howells, who do research at Lawrence Berkeley National Laboratory (LBNL), goes a step farther by showing that even a person who breaks a lamp is more at risk from mercury in the environment than from the mercury in the lamp itself.

The researchers point out that there is a distinction between the kind of mercury that you are exposed to from broken CFLs—elemental mercury—and the mercury emitted from power plant smokestacks after it finds it’s way into waterways and oceans, where it becomes methyl mercury. Methyl mercury accumulates all up the food chain, so that large fish like tuna can contain a lot of it. Methyl mercury crosses the blood-brain barrier and passes through a pregnant woman’s placenta to her fetus. Methyl mercury is responsible for developmental problems, while elemental mercury, which is inhaled, appears to be more of a hazard for adults and children, and only then in the case of severe or prolonged exposures. In most mild cases, when the elemental mercury exposure ends, the bad effects diminish and go away. This is unfortunately not true for the developmental problems caused by methyl mercury.

The startling conclusion of the paper is that in a worse case scenario—you break a CFL in a closed, unventilated room; you vacuum the carpet, throwing mercury into the air; you set the vacuum in a corner; and then sit in the room breathing for eight hours—the amount of mercury exposure is about equivalent to the exposure you’d get from eating a can of Albacore tuna.

Eating a can of tuna has positive health effects as well as the negative health effects from the mercury. There are no positive health effects from a broken CFL, and you can reduce your exposure. The researchers suggest that in the case of a broken CFL, you should immediately open a nearby window. You can limit contamination by gathering up the large pieces of the broken bulb into a bag and set the bag outside. The room should then be left to air out for an hour or so. If the lamp broke on a carpet you can vacuum, but it should be done quickly while the room is being ventilated, the vacuum cleaner should be removed to an outside area, and again the room should be left vacated for an hour or so. Once the vacuum cleaner has cooled, you can empty the contents of the vacuum cleaner bag into the bag with the broken bulb. Take the bag to your nearest recycling center.