Transit of Venus, 2012

Today, starting at 6:04 pm, you will have a chance to witness an event that will not happen again for more than a century. Venus will pass directly between us and the Sun, an event called a “transit.” If you can safely view the Sun (more on that in a minute), you will see a tiny black dot slowly move across its face. It will continue to transit well after the Sun has set. Alaska and Hawaii are the only U.S. states that will witness the entire event.

Time lapse photographs of the June 8, 2004 transit taken from a solar observatory in the Canary Islands. The black spots are Venus as it transited the Sun. Courtesy, the National Solar Observatory. 

Even though Venus is in an orbit closer to the Sun than the Earth’s, its orbit is tilted ever so slightly so that it’s usually never directly between us and the Sun. But every century or so, our orbital planes line up and we have a chance to witness two transits, eight years apart. Then we have to wait another century or so to see it again. The last Venus transit happened in 2004, and could be seen in progress at sunrise. I was lucky enough to see it. If you missed it, you have another chance today.

You might think that this event is interesting but otherwise useless. Until this century, though, countries spent enormous amounts of money and risked ships and lives to see and precisely record the transit. Why? Because it enabled us to measure the distance of the Earth to the Sun, what astronomers call the Astronomical Unit (A.U.). This distance, 93 million miles (150 million kilometers), is the ruler we use to measure all other distances in the solar system. Without it, we couldn’t send astronauts to the Moon or rovers to Mars.

Johannes Kepler first predicted that a transit would occur in 1631, but it wasn’t until the second 1639 event (eight years later) that Jeremiah Horrocks and William Crabtree actually witnessed one. Edmund Halley, of Halley’s Comet fame, suggested that by placing observers at different points on the Earth and carefully timing the event, one could triangulate and calculate the distance to Venus and the Sun. In response, all of the major European powers sent observers to the far corners of the Earth to record the 1761 and 1769 events and later, the 1874 and 1882 events. The travels and trials of these scientists as they went off to Siberia, Newfoundland, Madagascar, and other exotic locations are the stuff of adventure novels. You may recognize at least two names in the annals of this history – Captain James Cook observed the 1769 transit from Tahiti, and Charles Mason and Jeremiah Dixon (who later surveyed PA’s southern border, the Mason-Dixon Line) went to Cape Town, South Africa for the 1761 transit. At least one play, appropriately titled “The Transit of Venus” by Maureen Hunter, loosely documents the decade-long adventure of Guillaume Le Gentil, who lost his wife and home and was declared dead before returning from his expedition!

 Jeremiah Horrocks making the first observation of a transit of Venus in 1639. By Eyre Crowe. Courtesy Wikipedia.

How can you see this marvelous event? The safest way is to watch a broadcast from a solar telescope. There is an excellent educational website, http://www.transitofvenus.org/, that has loads of interesting information about the event and will broadcast live pictures. IF it’s clear, a 50-50 prospect around here in June, there are a few safe ways to view the event and I will again point you to that website for the best and safest ways. You must remember though, accidents while attempting to view the Sun with telescopes or binoculars often result in permanent damage or blindness. You cannot blink fast enough to protect your eyes. Sunglasses will not protect you. Black film (negatives) will not protect you. Even welding glass may not protect you because some wavelengths you cannot see may penetrate and still cause damage. Your retina has no pain sensors, so you wouldn’t know it was burning it until it was too late.

So be safe and enjoy the show! The next feature won’t start until December, 2117.


Originally published in the Bloomsburg Press Enterprise on June 5, 2012.

Helium

It was a spring evening in early May when hundreds of people descended on a landing field in Lakehurst, New Jersey for their first glimpse of a trans-Atlantic airship. There had been storms earlier in the day, but by 7 p.m., the storms had passed and the weather was deemed suitable for the landing of the Hindenburg, a German zeppelin – a sausage-shaped balloon filled with lighter-than-air hydrogen gas. The airship approached and circled before hovering about 400 feet over the landing site. Ropes were dropped to moor the zeppelin and pull it closer for passengers to disembark. Shortly after the ropes were dropped, a fire started near the rear of the airship. The outer skin of the zeppelin was breached and the hydrogen began to escape and mix with oxygen in the air, making an explosive mixture. The zeppelin quickly exploded in flames. Thirty-six passengers and crew were killed, and newsreel footage of this disaster has become iconic.

The Zeppelin LZ 129 Hindenburg explosion, May 6, 1937 in Lakehurst, NJ. Public domain image, courtesy Wikipedia.

Hydrogen is highly explosive, so why did the German’s use it instead of non-explosive helium in their zeppelins? Because at that time, the U.S. was the world’s main source of helium and tensions with the Nazi government led to an embargo of that critical resource. The U.S. is still the world’s leading source of helium, but you may have seen news reports about a possible shortage in the near future with rapidly increasing prices. Where do we get this gas and why is it so important?

Modern blimps use helium instead of hydrogen for safety reasons. Courtesy, D. Jensen and Wikipedia.

Helium, element #2 on the Periodic Table, is the second most abundant material in the universe, just after hydrogen. But it is rare on the Earth because it is so light, and once it escapes into the atmosphere, it quickly leaves the Earth forever. It is therefore a non-renewable resource, like oil. Almost all of the Earth’s helium supply was slowly produced by the radioactive decay of uranium and thorium, both present in small amounts in crustal rocks. Because it is a gas, it tends to be trapped where natural gas is also trapped, so most of our helium is taken from natural gas wells in the Midwest (Oklahoma, Texas, Kansas) where it makes up a few percent of all the gas coming from the wells. Back in the 1920’s, the U.S. built plants, pipeline, and underground storage facilities near Amarillo, Texas to extract and store the helium, thus establishing the National Helium Reserve (NHR).

Helium has many unique properties that make it valuable. It stays liquid even near temperatures of absolute zero and, for this reason, is used for deep cooling of superconducting magnets like those used in MRI machines, super-colliders, and high-speed bullet trains. It is used in the manufacturing of computer chips and optical fibers. One of its biggest uses is in arc welding and high-tech plasma coating applications where its main job is to keep more chemically reactive air away from the surfaces being welded or coated. In sum, helium is a critical resource for many of our highest tech industries and scientific research.

MRI machines are the largest single user of helium in the world today. Courtesy, KasugaHuang and Wikipedia.

By 1995, the U.S. had huge reserves of helium stored in the NRH, but it was more than a billion dollars in debt. So Congress passed a law in 1996 directing the liquidation and sale of the reserve to private industry by 2014 to recoup the costs. This law was controversial at the time, but has become more so because it was discovered that the formula used to sell the helium was well below market price and encouraged waste. By 2014, the NRH will be out of money, and whatever helium remains in the storage reservoir will not be accessible. This sudden disruption in the supply of a critical resource will likely lead to price spikes; in anticipation, prices have already jumped significantly. The U.S. Senate is now considering a bill (S.2374) to maintain the reserve for an additional 15 years to ease the transition to private suppliers. Other countries have started to look for their own supplies.

Out of curiosity, I checked to see if helium was present in the Marcellus shale gas being produced locally. I could find nothing definitive, but if helium prices do spike, you can expect to see it becoming a bigger issue.

Originally published in the Bloomsburg Press Enterprise on May 22, 2012.