Just after midnight on September 23rd, 1846, Johann Gottfried Galle stood at the telescope in the Berlin Observatory, calling out coordinates one by one to his assistant, Heinrich Louis d’Arrest. Despite the lateness of the hour, and the apparent tediousness of the task, there was an uncharacteristic tension in Galle’s voice, a certain expectancy. D’arrest, in the dim candlelight, dutifully checked off each entry on a map of the heavens. “Right ascension: 21 hours, 53 minutes, 16 seconds,” called out Galle. “Declination: negative 13 degrees, 24 minutes, 15 seconds. Magnitude 7.8.” There was a pregnant pause. “Sir,” came the reply, “that star is not on the chart.” The tiny speck of light would turn out to be the last undiscovered planet in the solar system.
Today (July 12, 2011) Neptune will finally celebrate its first anniversary, as it returns to the exact point in its orbit where Galle and D’arrest spotted it all those years ago. Continue reading
Calving of the Petermann Ice Island in August 2010. Credit: Jesse Allen and Robert Simmon, NASA Earth Observatory earthobservatory.nasa.gov
Where were you when the Petermann Ice Island calved?
Ok, so maybe the date of August 5, 2010 doesn’t exactly stick in anyone’s memory, but it totally should. That’s the day when an enormous chunk of the Petermann Glacier, on the north-west coast of Greenland, crashed into the sea, creating the biggest piece of floating ice the Arctic had seen in 60 years. Today, the battered remains of this frozen giant are still floating south, and are now within a few hundred kilometres of Newfoundland.
Short of watching The Lost World: Jurassic Park for the umpteenth time, there’s no way to see pachycephalosaurs really butting heads like they used to, 72 million years ago. But scientists from the University of Calgary have now come closer than ever before, and they’ve shown that the head-butting practices of these ancient creatures are unparalleled even to the present day.Continue reading
Earthquake damage near Abruzzo, Italy, 2009. RaBoe via Wikimedia Commons
As you’ll know from my mission statement, the purpose of this blog is to help science tell its own story, in other words, to improve communication between scientists and non-scientists. While I believe this to be a noble goal, others may disagree. Sure, knowing about science might get you a better score down at your local pub trivia game, but you can drive a car perfectly well without understanding the subtle details of thermodynamics that make it go. Science, the argument goes, is interesting to a select few but not essential for the vast majority. If the general public doesn’t “get” science, so what?
The Three Mile Island reactor in Pennsylvania experienced a partial, contained meltdown in 1979, with no casualties. Not all nuclear accidents are created equal.
Like everyone else, I’ve been closely watching the events in Japan over the last week. The tragedies arising from the earthquake and the resulting tsunami are powerful enough to defy easy attempts at explanation. Still, that hasn’t stopped us from trying, and a tension has emerged between those who see in the disaster hubris on the one hand, tenacity on the other.
Events like this, says the first camp, are reminders that we humans, like the rest of the life on this planet, are at the mercy of forces greater than ourselves. We can put men on the moon, but we can’t save ourselves from nature’s fury. By contrast, the second camp, while acknowledging the terrible reality of the disaster, is encouraged by the fact that human ingenuity has, if not averted it, at least drastically reduced its scale. The Sendai earthquake was a thousand times more powerful than that which hit Haiti just over a year ago. However, due to strict building codes, sophisticated warning systems, and prudent emergency planning, the death toll, while still significant, is over a hundred times lower. We cannot conquer nature, but at our best we can strongly curtail its destructive power.Continue reading
A few weeks ago, this video (made by Samantha Stewart of Yellowknife) garnered over a million views on YouTube, and was picked up by both CBC and CNN. It shows the seemingly magical instant transformation of boiling water into snow, which can only happen at temperatures below -30 C.
Needless to say, I couldn’t wait to try this out for myself. My opportunity came sooner than I expected; here’s me replicating the experiment from the balcony of my apartment on a typical frigid day in Ottawa.Continue reading
Just when you thought slime molds couldn’t get any more bizzare, some researchers at Rice University have caught them farming.
If you are already familiar with slime molds, you can skip over the next couple of paragraphs. If not, get ready to have your mind blown.
Life, you see, is quite fond of befuddling our attempts to understand it. While you may have a pretty good idea of what I’m talking about if I say “plant” or “animal” or “fungus” or even “protozoan,” slime molds don’t fit neatly into any of these categories. In fact, the things commonly lumped together under the title of “slime mould” exhibit a plethora of shapes and behaviours, ranging from things that look more or less like mushrooms (but aren’t) to things that look more or less like dog vomit (see illustration). Modern DNA analysis shows that different species of slime mould aren’t even that closely related to each other, let alone anything else.Continue reading
Imagine the sun as a basketball on a table. Imagine the earth as an apple with a pencil stuck through it. The earth is spinning like a top on the point of the pencil (its axis) while at the same time slowly circling the sun.* Thing is, the top isn’t straight up and down. It’s tilted, at an angle of 23.5 degree from the vertical, and it stays tilted at that same angle as it orbits the sun. Sometimes the bottom half is closer and gets baked a little more (summer in Australia) and sometime the top half is closer (summer in Canada.)
Now imagine you’re an ant on the surface of the apple, and imagine we could temporarily turn the sun’s light off. What you’ll see are the walls of the room. In space, there are no walls, but there are stars, which are far enough away that they can be considered stationary relative to the earth. However, as the Earth spins, the stars will appear to rotate around the point that lines up with the Earth’s axis, which you can now visualize as a laser beam shooting out of the top of the pencil. It so happens that there’s a star there; Polaris, the North Star. From the point of view of the ant, all the stars are rotating around Polaris, which stays in the same place.
The apparent rotation is slow, but fast enough to notice if you stay up all night looking at the stars. If you measure how much time it takes for a star to “move” from any apparent location all the way around the circle and get back to where it started, you’ll find that it’s about 23 hours, 56 minutes, and 4 seconds. This period of time is called sidereal day, from a Latin word meaning “star.”
At time 1, both the sun and a distant star appear to be directly overhead. At time 2 (one sidereal day later) the distant star is again directly overhead, but the sun is not. At time 3 (one solar day after time 1) the sun is again directly overhead, but the distant star is not.
Now let’s turn the sun back on. The 24 hour day we’re used to is called a solar day, and it’s the time it takes the sun to accomplish the same feat as the stars, that is, to appear to get back to where it appears to have started. The reason why it’s longer than the sidereal day is because the sun is much closer than the stars, so each day we’re in a slightly different position relative to it. This nifty diagram from Wikipedia gives a good illustration:
Incidentally, this whole optical illusion of the nearby sun appearing to be in a different position relative to the far-away stars is called parallax. It’s the same illusion you use when you pretend to squish the heads of distant people with your fingers.
Anyway, the very slight mismatch between the sidereal day and a solar day means that the sun isn’t quite in sync with its celestial backdrop. Over the course of the year, it appears to move in a slow circle in relation to the stars. Astronomers call this circle an ecliptic. Several thousand years ago, the Babylonians divided up the ecliptic into twelve pieces, each named after the closest constellation. Whichever of these twelve pieces the sun was “in” when you were born is your star sign. Note that you can’t actually see your constellation during the month you were born; since it’s “behind” the sun, it’s only out during the day, when we can’t see the stars.
Now for the precession part.
To go back to the top analogy; as the top slows down, it starts to wobble; the axis doesn’t always point in the same direction, like this gyroscope. This is called precession.
An animation of a gyroscope showing precession. Credit: Wikipedia
The wobble of the earth is caused by gravity. This is a bit complicated, but basically the earth’s spin means it isn’t perfectly spherical; it bulges at the equator. The gravity of the sun and moon pull on this bulge, causing the axis to precess in a slow circle, completing one revolution every 26,000 years.
This has all kinds of implications. For one, it changes the North Star. Polaris isn’t exactly lined up with the axis, it’s just the star that happens to be the closest right now. In the year 3000, Gamma Cephei will be closer, and 1200 years after that, the closest will be Iota Cephei. It’s equally true of the past as well; for the ancient Egyptians, the best North Star was Vega, and 12,000 years from now, it will be the closest again.
Precession also means that the ecliptic (which you will remember is the path that the sun appears to trace across the sky) has also moved since the ancient Babylonians invented the zodiac. However, because Western or “tropical” astrologers have been using the solar calendar instead of the sidereal one, they haven’t changed the dates to keep up. Thus, when I was born on October 21, 19 something-or-other, I was declared a Libra, even though the sun was actually “in” Virgo at the time. (Incidentally, “sidereal” astrologers in India and Japan do pay attention to precession and have adjusted their horoscopes accordingly)
Of course, “in” is a relative term; because of the non-uniform shapes of the constellations, the sun spends much more time in some than others, so it’s a bit arbitrary to decide that it moves from one to another 12 times a year. Alternate systems have been proposed throughout history, but the idea that we should add Ophiuchus as a 13th seems to originate with a guy called Stephen Schmidt, who wrote a book called Astrology 14 in 1970 (he also advocated adding Cetus, the whale). The idea proved quite popular among sidereal astrologers, particularly in Japan. The thing is, there is no international body governing astrologers in the same way that the International Astronomical Union does for astronomers. Even if there was, I have a funny feeling that all kinds of variations on the same general theme will be popping up as long as people continue to put their faith (and money) in astrologers.
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