Aphrodite’s Commute (or, the Transit of Venus)

3 06 2012

As we wind up our year in the UCSC Science Communication Program, it’s a time of transition. Not only for the ten of us, as we wrap up our final stories, multimedia projects, and internships, but also for the solar system. This week marks a rare celestial event, which happens just twice every hundred or so years: the transit of Venus.

Photo of the 2004 transit of Venus (photo by Mswggpai, Wikimedia Commons)

Earth’s fiery twin will cast a tiny black dot as it crosses in front of the Sun on June 5th or 6th, depending on where in the world you’re viewing it. Here in North America, it takes place June 5th, starting at 3:06pm in California. The last transit occurred in 2004, and this year’s will be the last your lifetime, as the next doesn’t occur for another 105 years. See the end of this post for tips on watching it.

The transit of Venus isn’t merely an astronomical curiosity – it played a crucial role in measuring the size of the solar system. A Brit named Jeremiah Horrocks first calculated and observed the transit in 1639, along with his friend William Crabtree. Horrocks turned his room into a giant pinhole camera, by putting a piece of cardboard with a hole cut in it in his window and projecting the black dot of Venus onto a white sheet. By measuring the size of the dot of Venus, Horrocks calculated the distance between the Earth and Sun to be about 60 million miles (97 million km). His number was only two-thirds the actual distance, 93 million miles (150 million km), but it was closer than any previous estimate.

Fellow Englishman Edmund Halley later described how to obtain a more precise estimate of the size of the solar system, which involved timing when Venus slid past the Sun’s borders. Yet Halley wouldn’t live to see the next Venus transits in 1761 and 1769. Transits occur in a pattern of 8 years apart, then 121.5 years, then 8 years, then 105.5 years. The whole pattern repeats every 243 years. The 1769 transit marked a major milestone in international scientific collaboration, because Halley’s calculations required observations from scientists around the world. One observer was the explorer Captain Cook, who voyaged to Tahiti to observe the transit as part of a secret mission to explore Australia.

Unfortunately, they had a tough time timing the exact entry and exit of Venus on the face of the Sun, due to something called the “black drop effect.” At the time when the black disk of Venus was just passing the Sun’s inner edges, a black teardrop shape appeared, connecting Venus to the Sun’s border. The effect is thought be caused by optical disturbances in the Earth’s atmosphere or the viewing apparatus.

Nevertheless, observations since then honed the estimate of the solar system’s size, which modern methods such as radio telemetry and radar have confirmed.

So why not turn your eyes skyward as Venus waltzes through the glare of our Sun next week. Here are some tips for viewing the transit:

• Here’s a map of places where the transit will be visible

• You can find out your local transit time here, **keeping in mind that daylight savings time adds an hour to the times shown.

• Not surprisingly, it’s not a good idea to stare directly at the Sun. Use proper eye protection.

• The best way to see the transit is with a telescope or binoculars with a solar filter. Failing that, you can use eclipse glasses or #14 welding glasses, or even a pinhole camera. You won’t be able to see subtle effects like the black drop with these methods, though.

• For a fun and engaging history of the transit, listen to the Big Picture Science radio show and podcast “Mass Transits”.

This will be my last post for this blog. Like Venus, our SciCom program has come full circle. It’s been a pleasure learning the craft of science writing here among the Central Coast redwoods. To all reading this, best wishes on your own transits!

Starry Starry Night: A visit to Lick Observatory

24 04 2012

by Tanya Lewis

San Jose is a bustling city of just under a million inhabitants. Yet only 25 miles to its east, on the tranquil summit of Mount Hamilton, astronomers cast their view skyward at the Lick Observatory. I visited the observatory, which is operated by the University of California, last week.

Lick Observatory Visitor Center (Photo: Tanya Lewis)

Lick actually encompasses nine different research telescopes. The observatory was funded at the bequest of James Lick, a wealthy piano maker and land baron, in the 1880s. Lick himself was quite a character. The richest man in California at the time, he originally planned to use his money to build a giant pyramid in San Francisco in his own honor, but luckily for science, George Davidson of the California Academy of Sciences persuaded him to build an observatory instead.

The road to the observatory follows a torturous, winding route, which at times was enough to make me carsick even as the driver. After an hour of careful wending, I arrived at the summit just before sunset. One of the support astronomers met me there, and showed me around the 36-inch (1 meter) James Lick Telescope. It was the world’s largest refracting telescope when it was built in 1888, and resembles the stereotypical long-objective of an amateur telescope, though much larger. On a slightly eerie note, James Lick is buried beneath the telescope.

The 36" James Lick Refracting Telescope. (Photo: Tanya Lewis)

But not much science goes on at the Refractor these days. The night I visited, astronomers were observing at the largest telescope at Lick, the 120-inch (3 meter) Shane telescope. Unlike the 36-inch, the Shane is a reflecting telescope, like the Keck Telescopes in Hawaii. I got to go inside the dome of the Shane and watch as the telescope and shutter rotated into position. They made a sound like the Titanic scraping against un-oiled hinges.

Next I visited the observing room, where the telescope operator and astronomer(s) were. (Actually, most of the observing these days takes place remotely, at UC campuses, but that night, an astronomy graduate student was being trained on-site.) Amazingly, only one, fairly dinky-looking computer is needed to control the telescope itself. The operator collaborates with the astronomer to aim the telescope at the parts of the sky that are of interest.

The 120" Shane Reflecting Telescope (Photo: Tanya Lewis)

That night, the science agenda involved looking at distant galaxy centers, or quasars, and taking light spectra – a breakdown of light by its component wavelengths. The spectra provide information about the ionized gas in the space between galaxies, known as the intergalactic medium, which yields clues about the physics of the early universe.

Although I couldn’t stay for the whole night of observing, I set off home safe in the knowledge that, in the still Mount Hamilton night, someone was probing our galactic origins.

Crabs Galore: From Fisherman to Pulsars

14 11 2011

By Tanya Lewis

One minute I’m milling around the dock of the Santa Cruz harbor, the next minute I’m hurtling out to sea on a 23-foot motorboat named “Aquaholic,” a chilly Pacific gale plastering hair across my face as I shout out questions about crab fishing and scribbling down the answers in a notepad that threatens to be tossed into the drink any second, shortly followed by myself. The driver cuts the engine and all of a sudden we’re bobbing on a glorified cork six miles out to sea. Using all my willpower to keep from tossing my cookies, I watch as a father and his son lower a wiry one-way deathtrap, laden with half a raw chicken, over a hundred feet down to the murky depths below.

A baited crab pot (Photo by Tanya Lewis)

Let’s back up: for our news writing class we’ve been assigned to write an advance on the Dungeness crab fishing season. We’ve been told to interview a crab fisherman, so I call up my classmate Helen and we head down to the harbor to find one. The commercial crab season doesn’t start until Tuesday, so the only guys actually fishing are the recreational fisherman, or “Sporties.” We get to the harbor around 3pm on a Saturday. We figure we’ll find a couple of fisherman, they’ll give us some great quotes about the joys of hauling crab, and we’ll call it a day. Easy as seafood pie!

A crab boat loaded and ready to go (Photo by Meghan Rosen)

Well, the only guy we can find is a man loading up his motorboat with his two sons. Sheepishly, we ask if he’s a crab fisherman, and he replies, “Yes I am. Wanna come out?” The answer’s out of our mouths before we have time to process whether this is a good idea. “Sure!” The rest is history. All-in-all it was…rather educational.

In case you’re not up-to-snuff on your crab knowledge, here’s a little background on the Dungeness crab:

Its Latin name is Cancer magister (literally, “Master of Cancer”). The name “Dungeness” comes from the port of Dungeness, Washington. The crabs are generally light reddish-brown on the back and white to light orange underneath, with a tinge of purple on the legs. Their pincers (chelipeds) are white-tipped and not just for show. (The fisherman we talked to said he uses tongs to handle the cranky critters.) See the photo below right.

Dungeness crab. (Photo from National Archives and Records Administration)

It’s the most abundant crab in California, which is probably why it’s so popular to fish (then again, rats are also pretty abundant and we don’t eat them). The Dungeness lives in eelgrass beds and on the ocean bottom, as far north as Alaska and as far south as Baja California (but aren’t often seen south of Santa Barbara). The males grow to be about 9 inches across, whereas the females rarely get larger than about 6.25 inches.

As a crab grows, its hard shell must be cast off in a process known as “molting.” The shell slits open at the junction of the carapace (front segment) and abdomen (i.e. tail flap) and the crab literally backs out of it, like wriggling out of a sweater. Underneath, a new shell has started growing, but is uncalcified and still soft. The “soft” crab grows rapidly until the new shell hardens. During molting, the crab can actually re-grow missing legs, though it takes a few molts for them to reach normal size again. They molt about once a year.

That’s about all I have to say about these crabs. But there is another kind of crab I want to talk about: the Crab Pulsar!

Recently, a bunch of astrophysicists detected some uber-high energy gamma rays from the Crab pulsar, and the theoretical models have no explanation for it.

A pulsar, by the way, is a highly magnetized rotating neutron star that beams out electromagnetic radiation. A neutron star is formed by the gravitational collapse of a very massive star during a supernova. So basically you have a magnetic ball of neutrons twice the size of the sun spinning around and whipping out pulses of radiation. Pretty insane in itself, if you ask me, but this is old hat to astrophysicists. What isn’t is the high energy of the radiation: gamma-ray pulses with energies greater than 100 billion-electron-volts.

The pulses were detected by the VERITAS (nice acronym, eh?) telescope array at the Whipple Observatory in Arizona. An international group of scientists published a paper about it in the October 7 issue of Science. Nepomuk Otte, a postdoc at UC Santa Cruz, was a corresponding author, and it was his cockamamie idea to look for pulsar emissions in this energy range. Otte’s response?

“To me it’s a real triumph of the experimental approach, not going along with the flow and making assumptions, but just observing to see what there is. And lo and behold, we see something different than what everybody expected.” (as quoted in a UC Santa Cruz press release)

The Crab pulsar was formed by a magnificent supernova in the year 1054, which left behind the Crab Nebula with the pulsar in its center.

The Crab Nebula. (Photo from NASA)

It’s one of the most-studied objects in the sky, spinning about 30 times per second and casting a beam of radiation from its magnetic field. The beam moves around like the beacon of a lighthouse, and Earth detects is as rapid pulses of radiation.

Scientists agree on the broad cause of pulsar emissions: electromagnetic forces created by the collapsed star’s rotating magnetic field accelerate charges particles to close to the speed of light, which emit a wide spectrum of radiation. But the devil’s in the details, which are still pretty mysterious.

After studying the Crab for years, scientists predicted that emissions above 10 Giga eV would die off exponentially. So they were flabbergasted when they found emissions above 100 Giga eV. (The prefix Giga = 10^9, or 1 billion)

~Warning! The next paragraph will make you 20 IQ points smarter. Read on at your own risk~

The conventional wisdom of how the emission works is curvature radiation: a dense electron-positron plasma is created near the polar cap of the pulsar, and the charged particles move relativistically with Lorentz factors   102103 along dipolar magnetic field lines, emitting radiation at frequencies that depend on the radius of curvature of the field lines. Phew!

But the results from VERITAS showed something else was going on. It turns out curvature radiation can only explain lower-energy emissions, not the high-energy stuff they observed.

“We really don’t know what causes the very high-energy emission,” said Otte.

(It takes a good scientist to admit they can’t explain something. But it takes a great scientist to come up with a new explanation.)

The scientists think one explanation could be (are you ready for it?): inverse Compton scattering. I won’t go into depth (or I’d be in over my head, to belabor the metaphor), but it involves energy transfer from charged particles to photons. Otte said they still don’t know the details though. They also don’t know if one mechanism explains the radiation at all energy levels, or whether different mechanisms operate at different higher and lower energies.

The next step is to characterize the gamma-ray emission in much greater detail.

So now you know all about crabs and astrophysics. What more is there to life?

Got raw milk?

20 10 2011

By Tanya Lewis

You drink it. You put it on your cereal. You dunk cookies in it.


Life's first beverage. (Photo by Tanya Lewis)

This magical substance is the first beverage most of us consume, when our wimpy newborn bodies can’t handle much else. But it’s not just a beverage, it’s a hyper-nutritious, calcium-packed nectar, produced by the mammary glands of female mammals to nourish their young.

Yeah, okay, so what’s the story with milk? Well, when I first arrived in Santa Cruz a little over a month ago, milk seemed to be the talk of the town. After all, it turns out, California is the leading producer of milk in the nation. It produced 38 billion pounds of milk in 2006. In fact, California dairy farms produce over 21% of the nation’s total milk supply.

Apparently, all the fuss had to do with recent crackdowns on producers of raw milk (or rather, owners of the milk producers, who were, in fact, farm animals).

Raw milk is milk that has not been pasteurized or homogenized. What exactly is pasteurization? You always see it on milk cartons, but how often do you stop to wonder what it actually involves?

Pasteurization, named after the Frenchman Louis Pasteur, is essentially heating up a liquid or food to kill pathogenic bacteria that can be threatening to your health. Sounds like a good idea, right? Well, the FDA thought so, and it’s become pretty much standard practice in the retail dairy business. But not everyone’s happy about it… more on this later.

Here in California, milk production is regulated by the California Department of Food and Agriculture (CDFA). On their website, they have a chart showing California’s bacteriological standards for milk:




Grade “A” Raw Milk for Pasteurization Bacterial (Standard Plate Count) Limits Not to exceed 100,000 per ml Not to exceed 50,000 per ml
Somatic Cell Count Not to exceed 750,000 per ml Not to exceed 600,000 per ml
Coliform No Standard Not to exceed 750 per ml
Laboratory Pasteurized Count No Standard Not to exceed 750 per ml
Grade “A” Pasteurized Milk Standard Plate Count Maximum 20,000 per ml Maximum 15,000 per ml
Coliform Maximum 10 per ml Maximum 10 per ml

Clearly, California is more anal than the federal government, at least when it comes to bacterial standards.

Back in 2008, the CDFA passed a bill called “AB 1735” which established new standards for coliform bacteria in raw milk sold in California. As of January 2008, the state’s two raw milk bottlers were required to have a final product with no more than 10 coliform bacteria per milliliter (same as pasteurized milk).

What’s a cauliflower coliform anyway? Colforms are a group of bacteria typically found in the environment: in soil, surface water, vegetation and the intestines of warm-blooded animals.  Well, I guess cauliflower could be found in that last one, too. Anyway, coliforms are used as a gauge of sanitary conditions in things like…(surprise) dairy production. They also produce the characteristic “off” taste in sour milk. While most don’t actually cause disease, a small fraction can make you sick, especially if you’re a young child, old person, or have a weakened immune system.

Kiyoshi Shiga (Tanakadate Aikitu Memorial Science Museum)

For example, a strain of E.coli O157:H7 has been implicated in some pretty sordid cases of foodborne illness. They produce a toxin called “Shiga toxin”, named after the Japanese physician and bacteriologist Kiyoshi Shiga, who first described the bacterial origin of dysentery due to Shigella dysenteriae.

(I can think of better things to have named after you than a toxin, but at least he got his own Wikipedia page.)

Shiga toxins work by inhibiting protein synthesis in cells by cleaving off a nucleobase from the RNA of a ribosome. The dysfunctional ribosome stops being able to produce protein. Clearly this not optimal. Shiga toxin-producing E.coli were behind for the recent outbreak in deadly sprouts from Germany.

Another kind of sprouts, of the nonlethal Trader Joe's variety (photo by Tanya Lewis)

But back to milk…

How do coliform get into milk? The most common way is milking cows with wet, grimy udders or using unclean milking equipment. Their presence, while not inherently harmful (unless they’re the toxic variety), has been used as an indicator of sanitation for years. In dairy farms, coliform count is a measure of the fecal bacteria in milk (eww, right?), but coliforms can also signal environmental contamination of drinking water supply systems.

The good news (some would argue) is that pasteurization of dairy products easily kills coliform. Contamination can occur after pasteurization too, though, which is why it’s important to refrigerate milk. For raw milk, California law mandates it be cooled to 50 deg. F after milking begins and maintained at 45 deg. F within two hours after milking.

According to the CDFA, the new standards for coliform count in raw milk can be achieved without pasteurization, “with utilization of sound cleaning and sanitation practices.” They say that on average, about 25% of milk samples from dairy farm inspections fall within the allowable range for colliform bacteria. ** Agreeing with national data collected by USDA’s National Animal Health Monitoring System, and published in the Journal of Dairy Science in 2004 (J. Dairy Sci. 87:2822).

The CDFA lists a few suggestions for minimizing coliform count in raw milk. Here are two of my favorites:

  • Properly managing manure, bedding, housing and pastures to prevent cows from arriving overly dirty at the milking parlor.
  • Use of an appropriate commercially available pre-milking teat sanitizer to further reduce the amount of bacteria contacting milking equipment

    Penny Ice Creamery Pasteurizer, Santa Cruz (photo by Tanya Lewis)

The raw milk bill specifies maximum bacterial counts for a whole range of dairy products, including ice cream, sherbet, and eggnog! I did a bit of “field research” at the Penny Ice Creamery  here in Santa Cruz, and found out their ice cream is a) delicious and b) pasteurized in-shop (see photo).

Well, not everyone’s on board with the raw milk restrictions. Many people consider it their right to drink and distribute raw milk. This isn’t prohibition, after all. Recently, Santa Cruzans (or whatever the right collective noun is) staged a Milk-In at the Downtown Farmers Market. People are serious about their milk, so don’t even try to move their cheese.

On that note, I leave you with some cow pictures:

“Pauline was the pet of President William Howard Taft and is seen here grazing on the south lawn of the White House. She supplied the Taft family with fresh milk daily.” (DC Public Library Commons)

A Canadian Holstein (image from http://www.dairycowdaily.com)

Gladys the Swiss Dairy Cow, as a schoolbus (image from James Lebinski, Wikimedia Commons) More versions of Gladys at wikipedia.org/wiki/Gladys_the_Swiss_Dairy_Cow.