HISTORY AND MYSTERY
As I looked over the files this week, I discovered that the file that’s near and dear to my heart was bulging. So we’re off for a rocket ride through space this week. But some of our stories also involve time travel (after a fashion). So enjoy some space news with me.
There’s a small cottage industry that attempts to solve ancient mysteries by examining what was going on in the sky at the time. Astronomers have used things like visible constellations, conjunctions, phases of the moon and eclipses to date things like Julius Caesar’s first arrival in Britain, the possible time of the birth of Jesus and the exact dates of first contacts with native peoples. New research now sheds light on Homer’s arrival back in Greece after the Odyssey.
WELCOME HOME
There are many debates that surround Homer’s Odyssey but one that just may be subject to scientific analysis is that there was a total solar eclipse at the time of his return to Greece.
Total eclipses are very rare. They are so rare that if what Homer describes is truly an eclipse, it could help historians date the fall of Troy, which may have occurred around the time of the events described in the Iliad and the Odyssey. But after arguing about the point for hundreds of years, historians, astronomers and classicists finally agreed that there was no corroborating evidence and tabled the discussion. Now Argentinean researchers believe they have found some overlooked passages that, taken together, may shed new light on the timing of an epic journey.
The astronomers combed through the Odyssey to find specific astronomical references that could be precisely identified as occurring on specific days throughout Odysseus’s journey. Then, they aligned each of those dates with the date of Odysseus’s return, the same day he murders the suitors who had taken advantage of his long absence to court his wife.
They identified four celestial events. The day of the slaughter is, as Homer writes more than once, also a new moon (something that’s also a prerequisite for a total eclipse). Six days before the slaughter, Venus is visible and high in the sky. Twenty-nine days before, two constellations — the Pleiades and Boötes — are simultaneously visible at sunset. And 33 days before, Homer may be suggesting that Mercury is high at dawn and near the western end of its trajectory. (Homer actually writes that Hermes — known to the Romans as Mercury — traveled far west only to deliver a message and fly all the way back east again; the researchers interpret this as a reference to the planet.)
Astronomically, these four phenomena recur at different intervals of time, so together they never recur in exactly the same pattern. The astronomers looked to see if there was any date within 100 years of the fall of Troy that would fit the pattern of the astronomical timeline. There was only one: April 16, 1178 BCE, the same day that astronomers had calculated the occurrence of a total solar eclipse.
The Argentinean astronomers acknowledge that their findings rely on a large assumption: Although the association of planets with gods was a Babylonian invention that dates back to around 2000 BCE, there’s no evidence that those ideas had reached Greece by the time Homer was writing, several hundred years later. Ultimately, whether they’re right or wrong, the researchers are interested in reopening the debate.
"Poor men, what terror is this that overwhelms you so? Night shrouds your heads, your faces, down to your knees — cries of mourning are bursting into fire — cheeks rivering tears — the walls and the handsome crossbeams dripping dank with blood! Ghosts, look, thronging the entrance, thronging the court, go trooping down to the realm of death and darkness! The sun is blotted out of the sky — look there — a lethal mist spreads all across the earth!" — Homer (translation by Robert Fagles)
And now that you’ve had your classical literature fix for the month (year?) let’s fast-forward almost 3000 years and have a look through the eyes of history.
GALILEO’S EYES
Exactly four centuries ago, the Italian astronomer Galileo Galilei turned his ‘spyglass’ on the sky for the first time and turned the world upside down. He used his new invention to look at the moon, gaze at the Milky Way and discover the four large moons of Jupiter, which started humanity down that long road which eventually dethroned the planet Earth as the center of everything.
In synch with the International Year of Astronomy (IYA), which marks the 400th anniversary of Galileo’s discoveries, a group of astronomers and curators from the Arcetri Observatory and the Institute and Museum of the History of Science, both in Florence, Italy, are recreating the kind of telescope and conditions that led to Galileo’s world-changing observations.
Astronomers will be using the recreated ‘spyglass’ to catalogue all the objects recorded in Galileo’s ‘Sidereus Nuncius’, which is translated as the Starry Messenger. Sidereus Nuncius was published in 1610 and includes most of his early observations. Interestingly enough, since it was written not for other scientists but for the non-scientist, it’s remarkably easy to read. (Perhaps more so than Homer’s Odyssey!)
The astronomers have already observed the Moon and Saturn and are now recording images of Jupiter’s moons and the phases of Venus. Both of these observations provided Galileo with crucial evidence that most objects in the solar system orbit the Sun and not the Earth.
To recreate Galileo’s first telescope, the team first examined the lens of a telescope given to Galileo’s patron, the Grand Duke of Tuscany, Cosimo II, in 1610. They measured the shape and refractive index of the lens, and used X-ray fluorescence to determine the condition of the glass. Unfortunately, the team has not been able to build a replica of the telescope actually used by Galileo to make the observations reported in Sidereus Nuncius as only one lens of that instrument survives.
The project, however, is more ambitious than just recreating one of Galileo’s telescopes. The ultimate aim is to catch what Galileo himself might have seen. It is known that Galileo died blind and the researchers are keen to open Galileo’s tomb to retrieve DNA and diagnose his optical affliction in order to create conditions that resemble looking through Galileo’s very own eyes. Most historians think that Galileo didn’t have an eye disease however; they think that he gradually lost his eyesight because he had used his remarkable new invention to look directly at the Sun. Galileo sacrificed his corneas to tell us about sunspots.
Galileo began a whole new era of observing the sky, but life on Earth is possible because you can only observe certain things from Earth. Our atmosphere is opaque to virtually all electromagnetic radiation and trust me, this is a very good thing. About the only waves that get through our air are visible light, heat, some ultraviolet and some radio waves. We don’t have to worry about the Sun frying us with x-rays or gamma rays or microwaves because all these deadly radiations are blocked by our air. Although it keeps us alive, that lovely nitrogen/oxygen blanket does a lousy job of letting astronomers study the stars (although Galileo certainly didn’t think so!)
The only way to study these other wavelengths is to either put your detector in orbit or to boost it up beyond most of Earth’s air with a rocket or a balloon. Astronomers have recently done that and discovered something very strange.
LOUDER THAN A WHISPER
In July 2006, NASA’s Columbia Scientific Balloon Facility in Palestine, Texas
launched a balloon-borne instrument named ARCADE, which stands for the Absolute Radiometer for Cosmology, Astrophysics, and Diffuse Emission. ARCADE’s mission was to search the sky for heat from the first generation of stars and the balloon flew to an altitude of 120,000 feet, where the atmosphere thins into the vacuum of space. Instead they detected cosmic radio noise that booms six times louder than expected.
"The universe really threw us a curve," one of the researchers says. "Instead of the faint signal we hoped to find, here was this booming noise six times louder than anyone had predicted." Detailed analysis ruled out an origin from primordial stars or from known radio sources, including gas in the outermost halo of our own galaxy. The source of this cosmic radio background remains a mystery.
Many objects in the universe emit radio waves. In 1931, American physicist Karl Jansky first detected radio static from our own Milky Way galaxy. Similar emissions from other galaxies create a background hiss of radio noise.
The real problem is that there don’t appear to be enough radio galaxies to account for the signal ARCADE detected. To account for the noise the astronomers detected, you’d have to pack the radio galaxies into the universe like sardines. There wouldn’t be any space left between one galaxy and the next.
The sought-for signal from the earliest stars remains hidden behind the newly detected cosmic radio background. This noise complicates efforts to detect the very first stars, which are thought to have formed about 13 billion years ago — not long, in cosmic terms, after the Big Bang. Nevertheless, this cosmic static may provide important clues to the development of galaxies when the universe was less than half its present age. Unlocking its origins should provide new insight into the development of radio sources in the early universe.
"This is what makes science so exciting," says Michael Seiffert, a team member at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. "You start out on a path to measure something — in this case, the heat from the very first stars — but run into something else entirely, something unexplained."
ARCADE is the first instrument to measure the radio sky with enough precision to detect this mysterious signal. To enhance the sensitivity of ARCADE’s radio receivers, they were immersed in more than 500 gallons of ultra-cold liquid helium. The instrument’s operating temperature was just 2.7 degrees above absolute zero.
A mysterious screen of extra-loud radio noise permeates the cosmos, preventing astronomers from observing heat from the first stars. The balloon-borne ARCADE instrument discovered this cosmic static (white band, top) on its July 2006 flight. The noise is six times louder than expected. Astronomers have no idea why. (Credit: NASA/ARCADE/Roen Kelly)
Don’t you just love the last sentence in the picture caption? “Astronomers have no idea why.” And that, gentle readers, is what has motivated every scientist on the face of the planet since long before Galileo. As someone once said, the real leaps in science don’t occur in huge labs with megabudgets. The real leaps in science occur when someone says “Hmmmm . . . that’s funny . . . “. Or in this case, “What was that you said? I can’t hear you!!”
Cruise on over to the Deep Website at www.thedeepradioshow.com to learn more about space and many other topics. Enjoy!
