18 Mar 2007
It doesn't take a great imagination to see that spring marks a sort of beginning or rebirth for so many people throughout the world, both ancient and modern. We proclaim it in our holidays, such as Easter and St Patrick's Day. It's also announced in nature in both the animal and plant world, as life seems to spring simultaneously from every corner of our land.
And, of course, our weather changes from the bleakness and wet of winter into a new kind of day, a more joyous climate, one that drives the celebration.
Not to take away from the poetry and romance of this beautiful season - on the contrary, we should all celebrate it - but much of what we enjoy about the season and find ourselves immersed in has a physical basis, one perfectly hardwired into the framework of our solar system.
The celestial cause of all this revelry is our planet's tilt with respect to the sun. Regular readers here will know that that is a truly wonderful thing about our home planet. For part of the year we are tilted toward the sun (summer), and part of the year away from it (winter). Between the two extremes we stand at upright attention to our star as we pass through the spring and autumnal equinoxes.
If we had no tilt, there would be no seasons; no bleak winter, no scorching summer, no windy, dry autumns, and of course no blooming spring. We would have essentially the same sort of weather all year long. The word "boring" immediately comes to mind. More importantly, though, the comfortable living places on this planet would be in narrow bands between a blazing equator and the permanently frozen northern and southern latitudes.
If we were tilted over much more, the seasons would be more extreme with summer always very, very hot, and the winters always frozen. Huge variations in temperature are not conducive to happy civilizations.
The way it is tilted now assures that there is the greatest amount of favorable weather spread out over most of the planet. Thus, our present tilt favors the greatest and most comfortable spread of civilization.
It is this Tuesday, at 5:09 PM to be precise, that we are at spring equinox - the planet is lit equally from pole to shining pole. For us in North America it is our passage from the "tilted away" days of winter to the "tilted towards" days of summer.
Of course this transition means more energy from the sun, which leads to warmer temperatures and more energy for the growth of plants, the bottom of the food chain.
We don't notice much of a change here in southern California with our minimal variation in weather, but in colder and wetter places - like back east - the first day of spring is a sign of hope: It will get better soon.
Now, of course, the weather doesn't change overnight - the birds don't start tweeting and bees don't start buzzing on the magical First Day of Spring. The climate always experiences a little delay. Just as our daytime temperature doesn't jump as soon the sun peeps its head above the horizon, the Earth takes a little while to warm as we approach summer. But it does happen.
You can probably see why many civilizations used to begin their new year in March. Remnants of those old days are still there in our calendar. With March as the first month, you can see that September was the seventh month (sept- meaning seven), with October (oct- = eighth), November (nov- = ninth) and December (dec- = tenth) following. January and February were the closing months of the year as the sun began to rise higher in the skies to announce that spring and a new year were coming.
With the coming of spring, with the hope of new life and rebirth, we can see how our lives as humans are once again influenced by some heavenly source.
Have a great spring!
04 Mar 2007
Several weeks ago something new was spotted in the early morning skies in the constellation Scorpius, something which hundreds of years ago would have caused quite the uproar to say the least.
The new object, starlike in appearance, goes by the name V1280 Scorpii. By the time you read this it may have dimmed enough to require a telescope in order to be seen. But the point is: A new thing could be seen by the naked eye! The eternally unchanging skies changed for us, if only just for a couple weeks.
V1280 Scorpii is a nova, not to be confused with its more explosive sister, the supernova. But you can see in both names the root "nova," Latin for "new."
I'll explain what a nova is below, but it's interesting to note that just centuries ago actually seeing a new star appear in the sky was a paradigm shift of the first magnitude.
Back then the starry heavens were filled with the fixed stars, the never-changing canopy of lights arching over us from one horizon to another. For some they represented the sacrosanct realm of God where nothing varies. For many who lived during the time of Galileo or the famous astronomers Tycho Brahe and Johannes Kepler something new appearing in that hallowed sky was highly suspicious and went against the prevailing worldview.
But Tycho Brahe saw a new star, a "stella nova," in 1572 and using some simple math showed that it was not some atmospheric phenomenon, but something way, way, far away, where things were assumed to be fixed and unchanging.
He and Kepler and Galileo were part of a golden age of astronomy, when we started using events like novae and supernovae to see the glorious heavens as an extension of our physical universe and not some quintessential otherworldly firmament. The universe hasn't been the same since.
So what is a nova? Well, most of us are aware that a supernova is the explosive death of a big star. But a regular plain old "nova," sans the super - what's that?
Most stars end their lives with a whimper, with no explosive end. Our own star will give up the ghost that way. In ways beyond what I can discuss here, a star like the sun dies by shedding its outer layers, leaving behind only a white-hot core, christened a white dwarf.
Now that's pretty much the whole story if the star is all alone. But many of the stars up there are binaries, that is, they have buddy stars. That can make for quite a different scenario.
If the next door neighbor to a white dwarf grows up and out into what is called a red giant it is quite possible that the white dwarf may actually find itself stealing away some of its bloated friend's gas.
In stealing away the hydrogen from the other star, it now can form a new layer of hydrogen on its own surface. An old dead star is suddenly rejuvenated, if only temporarily.
Now understand that hydrogen is the fuel of stars, a stellar staple so to speak. The old dense, hot, white dwarf, previously depleted of fuel, now sees an opportunity to come alive again. The white dwarf's intense gravity crushes the hydrogen on its surface and heats it to about 40 million degrees Fahrenheit. This is enough to cause a fusion reaction (think nuclear weapons) and the surface erupts in a flash of energy.
The whole complicated process can last from weeks to months, and if the star is close enough to earth we can see a "new star," a nova, in the night sky.
If the white dwarf survives, this whole process may happen again, and again, and again, providing Earthlings with successive novae in following decades or centuries.
The nova may be a mere physical phenomenon, but it still inspires awe and wonder in the heavens, something the cold sciences will never take from us.