29 Apr 2007
Turn the month of May into a planet watching extravaganza! OK, maybe I'm a little too excited about this, but for those readers who for the first time in their lives are taking an interest in the skies and enjoy watching them change before their eyes, the merry month of May is like Planetary Movements 101.
Only half of the planets are seriously contending for your attention, but they make the most of their other-worldly personalities.
Mercury and Venus and Saturn will be vying for your interest in the western skies after sunset. Jupiter will strut down the cosmic catwalk later on in the southeastern skies.
Alas, mighty Jupiter doesn't rise until about 11 P.M. at the beginning of the month. But as we catch up with it in our orbit it will rise earlier and earlier. By the end of the month, the great king will rise around 9 P.M. You cannot mistake it; it is by far the brightest object in the southeast at those hours.
Even though he shines very brightly, being down so low to the warm horizon ruins attempts to see the fine details of the Giant of the solar system. Summer will be a better time to see Jupiter; it will be rising earlier and soaring higher at more reasonable hours.
This is a great month to see Saturn especially if you have a telescope to help discern those beautiful rings. The Ringed One is high up in the southern skies at the beginning of May, but seems to slowly creep up on Venus in the west as the month wears on. Our orbit will soon take us to the other side of the sun as Saturn, and the Belted Beauty will bow out of the Planet Play, behind our star, but only for a while.
If you've been one of the followers of Venus you will have already noticed that the brilliant jewel of the western skies keeps rising ever so slowly above the horizon. It has been running around the sun, trying to lap us in its orbit. It soon will, and as it does it gets brighter and brighter as it comes nearer and nearer to us. Being covered in clouds that reflect about 60% of the sun's light makes it one really dazzlingly bright planet.
As it gets nearer, it is also easier to see details through a telescope. At the beginning of the month, see how she is like a miniature gibbous moon. As she closes in she will look more and more like a first quarter moon, with half of the planet clothed in darkness. Please mark May 19 on your calendar! It is on that evening that the crescent moon and Venus nearly kiss. It will be awe-inspiring, a great evening to write a poem.
These phases of Venus were first seen by Galileo and proved - to him anyways - that Venus was orbiting the sun and not us, an idea which centuries ago was a revolutionary paradigm shift. It took decades after his discovery for that new idea to be generally accepted.
Venus will peak during the month, almost seeming to hover there in position. In June it will begin to slowly sink towards the horizon as it passes between the sun and us.
Mercury is at the moment rounding the sun on the far side. And, true to form, the mercurial little one will leap up into the western skies around mid-month, seemingly out of nowhere.
By the end of the month it will have already reached its peak in the heavens after sunset, just about a handspan above the horizon, only to quickly disappear during June.
You'll notice that both Jupiter and Saturn hardly move at all through the skies during their May appearance. They are part of the very distant outer planet group, all very slow moving, in no hurry to get anywhere. They will be in basically the same area of the sky the next time we swing around.
Venus and Mercury are inferior planets - no offense - and thus are always hugging the sun. Because of the laws of planetary motion this close couple are always in a hurry. One can actually observe their movement through the stars week by week, they travel that fast.
Why don't you? Take time this month and go out and do a little planet watching.
Until next time, clear skies!
15 Apr 2007
Sad but true: The many disciplines of science don't often get together to see a big picture. Science is like an inn with many rooms, but the guests very rarely get to know each other well. Astronomy is in one room, geology is next door. Biology is somewhere downstairs. It would be nice if they came together more often, over dinner maybe, to discuss their ideas and better formulate a big sweeping picture of the cosmos.
I was reminded of that predicament in a recent visit to the big island of Hawaii with my astronomy club. The island itself is a wonderful reminder that none of the disciplines of science is an island unto itself. They are all interrelated - from physics and astronomy to biology and anthropology - and would benefit in that awareness.
How can an island do that? It starts with Hawaii's creation.
Our planet, unlike any we know, has an outer layer of ultrathin movable solid plates crawling over a thicker layer of semi-solid molten rock. Where the plates meet or spread apart or move by each other we have volcanic activity and earthquakes.
But what about Hawaii? It is right in the middle of the Pacific Plate, nowhere near a boundary.
The big island of Hawaii rests on a "hot spot" on the plate, a point where magma below is extra hot. So much so that it burns a hole through the plate, oozes out, and breaks above the surface of the waters to form the islands.
We can see the history of the island chain as we go from Kauai in the northwest to the Big Island in the southeast. That hotspot is staying in the same place as the plate moves above. Thus Kauai, now away from the hot spot, is the older, more worn down, of the islands. Hawaii is the youngest. In fact, Hawaii is still growing, spewing lava into new real estate near the Kilauea volcano.
But that's the not the whole island story. The physics of weathering on this planet form and shape the island into a paradise. The waves constantly pound the coastline breaking up the lava and coral reefs into beaches. The amazing water cycle on planet Earth provides a constant rain there that helps to slowly break down the volcanoes, shaping beautiful valleys in the process.
But there is more than the physical sciences at work here. Life plays a role in the shaping of paradise. Plant roots break up the hard rock which, together with dead plant material, make a profoundly viable soil, so fertile you'd think anything could grow on it.
All this makes it easy for insects and other animals to eventually carve out ecological niches for themselves. Wonderfully coordinated ecosystems fill the island.
Finally, after years of preparation, the island is primed and ready for discovery by ancient peoples sailing from other islands hundreds and hundreds of miles away. They arrive, now ready to call this island, and the others in the chain, their home. The whole process is not unlike the whole history of our own planet - in miniature.
Modern discoverers attracted to the Big Island now build the best observatories in the world on the top of its highest mountain, Mauna Kea, where the skies above are impeccably clear and free of human light pollution, a contamination that ruins the skies elsewhere. And it is here that some of the most amazing discoveries about our universe are made today, discoveries that help us to understand better the workings of the cosmos and our place in it, including the rich history of the Hawaiian Islands.
But aren't these coordinated processes taking place all over the planet, processes which mold and fine-tune this planet to near perfection? Sure they are. The Big Island just focuses it all into an intense beam of discovery and appreciation.
If you have an interest in any of the sciences and you have the opportunity to go to the island of Hawaii, do. From the active volcanoes in the south through the rainforest jungles and falls in the east to the arid snow-capped observatory-studded summit of Mauna Kea, the Big Island helps us to understand and appreciate the Big Picture of it all.
01 Apr 2007
You are undoubtedly aware that in this next week there are the celebrations of Passover and Easter. You may have noticed that they are not on the same dates as they were last year. Christmas, New Year’s, Independence Day - all the other big guys fall on the same dates year after year, but not these two.
You may also wonder why this phenomenon is being discussed in a column that deals primarily with the starry skies.
Well, these two days - high holidays for hundreds of millions of people throughout the world - set their dates on the movement of heavenly bodies, the sun and moon to be precise.
Passover is a celebration that goes back millennia, back to the days of Moses. The people of Israel were then slaves to the Egyptians, and God deemed it was the right time for Moses to get His people out of Dodge and into the Promised Land. Pharoah repeatedly balked at this divine decree and thus got himself in a heap of trouble, putting himself and his people on the receiving end of the now famous Ten Plagues.
The last plague had the Angel of Death taking the firstborn males of the Egyptians but â€œpassing overâ€ the houses of the Israelites, those that were marked with the blood of the lamb. The Jews were later to mark this memorable event, the beginning of the exodus, on their date of 15 Nisan. Now pay close attention, it can get a little complicated here.
Nisan is the 7th month of the Jewish calendar, a calendar that starts on 1 Tishri, better known as Rosh Hashana. That special New Year’s Day is defined as the first new moon after the autumn equinox. With me so far?
Now travel along with me 6 months down the road to the month of Nisan. That would be about 6 new moons later. At this point, add a couple weeks to get to 15 Nisan. That's Passover, which, being two weeks after a new moon, happens to be around a Full Moon.
Now just as Passover has its date determined by the sun and moon, so does Easter.
Easter, as we know, is the day Christians celebrate Jesus' resurrection from the dead. This is the highest of high holidays for them. Those who know the events of Jesus’ death know that he was in Jerusalem for the Passover when he was arrested and executed.
It is no coincidence that Passover and Easter fall so close to each other so often, with this year’s Easter just days after Passover.
The quick and dirty way to estimate which date Easter will fall on goes something like this: It's the first Sunday after the first Full Moon after the spring equinox. You math people will figure out quickly that the spring equinox is 6 months after the autumn equinox, and the first full moon after that is very often - surprise! - Passover.
And this year that first Sunday after the first full moon falls on April 8.
But it's not so easy as this every year. The Christian church uses a loose formula for setting equinoxes and full moons. It is not as exacting a science as astronomy.
For example, in 1962, astronomical and church renderings didn’t exactly agree. Then, the precise moment of the Full Moon took place a mere 6 hours after the exact moment of the spring equinox, both on 21 March. So Easter should have taken place the next Sunday, right?
Wrong. The Church’s less exact formula had the Full Moon on the 20th, followed by their 21 March equinox. So, according to the rules, the next Full Moon after "equinox" wasn’t for another month, and Easter wasn’t celebrated until 22 April! Something similar happens next year, too.
Is the occasional discrepancy a big deal in the Big Scheme of Things? Of course not. Easter will be celebrated and there will be much rejoicing regardless of the exact date.
But again, can you see how the uncomplicated and seemingly innocuous events happening in the cold cosmos above, the simple movements of the sun and moon, can affect millions of humans on this beautiful rock we call Home? I love this place!