Happy Spring

The start of the spring season is far less romantic than the first bloom, the larking robin, or the shortening of sleeves and pant legs, exposing skin and luring your fancy.

Instead, the vernal equinox (Latin for spring equal night) happened for only a minute or two, just 7 minutes past midnight today. That marked the moment the sun was directly over the equator, working its way back to the northern hemisphere. Sexy!

You Will Never See the Dark Side of the Moon

Well, technically nobody will ever see the dark side of the moon, because no such thing exists. All sides of the moon receive sunlight, but there's still a side you will never see first-hand...unless you're an astronaut on a lunar mission.

It's the farside, not the dark side. The concepts are similar; the names are different.

From Earth, we only ever see one hemisphere of the moon. The farside is always out of our sight, facing off into space. The moon rotates just like the earth, but it rotates for once for every revolution around Earth: 28.5 days. That is roughly equal to a month, or the amount of time it takes to complete a revolution, a synchronous rotation. Therefore, we only see one side.


The farside is riddled with craters, since it intercepts many earth-bound meteors. This image was taken by Apollo 16.

Oh well, I guess one side is better than no sides.



A grammar note: Earth is only capitalized when referring to the celestial body without the use of a definite article, namely the.

The Number of Galaxies in Nothing

Great if you have 6 minutes. Always one of my favorites, the image was my desktop background for a while. I understood where it had come from, but not what it meant until this video.

Finding North

North. It's the "never" in the mneumonic device "never eat spider webs," which translates as North East South West, or the compass directions in a clockwise motion. But where is it?

North is north--yes, that's easy. It's where Canada is when you're stateside or the North Pole is when you're anywhere else. It's where birds migrate during the spring and summer and where chill winds from in the bleaker months.

During the day, you can find it by the sun's position. It rises in the east and sets in the west... Moss grows on the south side of trees, contrary to popular belief, so the clear side of the trunk must point north. And it's where the closest magnetic pole is located, so compass needles, or statically charged paperclips, will point there.

But let's suppose you're trapped in a harrowing novel. You're at sea. Darkness surrounds you, save what twinkles and glows in the sky. How do you orient yourself then? Where is north according to the sky?

Well, the North Star, Polaris, may be positioned in accordance with its eponymous namesake. And it is, of course. It's the brightest star in the sky some say, but this isn't the case, even though it is quite bright. And how do you know it's a star and not a planet?

Well, first off, planets do not twinkle. Pockets of air moving across our field of vision cause stars to twinkle (sorry, they're not really pulsating visibly). The air pockets are larger than the stars as they appear in our field of vision. The planets, however, appear larger than the air pockets, so their reflected light is not refracted by air molecules. Second, there are only five of them visible to the naked eye: Mercury, Venus, Mars, Jupiter, and Saturn. So given the vastness of our sky, you have a small chance of mistaking one for Polaris.


Polaris is very easy to find, even if it weren't so bright. Take the most recognizable constellation: The Big Dipper (Ursa Major). If you imagine it as the ladel it represents, then take the lip of the concave and imagine the two stars that make it up point off into space. If you take the distance between these two stars and multiply it by 5 or 6, you'll hit Polaris.

More easily, though, is that Polaris is the end star of the handle on The Little Dipper (Ursa Minor).

Too many stars to concentrate on just one? Try using the moon...as long as it's not full. Whatever phase the moon is in--quarter, half, waxing, waning--if you draw a line from the tip of one bright point to the tip of the other, then it should point north.

The Northern Lights

I had seen the Northern Lights (Aurora Borealis) only once before college. I remember laying in the driveway on a blanket next to a field of corn. They were distant, but frantic in their billowing curtain display of ivory shades.

Then I went to the Upper Peninsula and saw them with a frequency I may never again have the opportunity to experience. Reds, greens, whites, and even tints of purple appeared almost monthly above the cresting valley ridge on the other side of the canal.



But what causes these sporadic displays of electrical art? Well, it took me a long time to understand...so here goes:

The earth is surrounded by a magnetic field, originating from deep within its core. The field is strongest at its magnetic poles and weakest around the equator. The sun has a much larger magnetic field, which extends through the orbit of the earth. This field combined with fusion particles and radiation constitute solar wind.

Solar wind acts upon the earth's magnetic field in much the same way normal wind would act upon a pile of sand: the windward side is stretched and extended into the leeward side to create a tail like a melting comet.

The pressure exerted on the earth's magnetic field excites existing particles in the earth's atmosphere and actual creates a voltage gradient between the magnetic poles and the solar-blown "tail" of the earth's magnetic field.

This all takes place in the magnetosphere and as the voltage pushes the charged particles towards the poles, they amass and are pulled closer into the ionosphere. There, they react with ionosphere gases and the resulting reaction discharges visible electrical energy...light.

The stronger the solar wind, usually indicated by solar flares, or spastic jumps of solar activity beyond the sun's regular corona, the more brilliant the auroras.

Winter

"No matter what you learn today, nine of you will go back to saying winter is caused by the earth being farther away from the sun," my high school science teacher told us. We were a class of ten.

While the elliptical orbit of the earth around the sun does cause it to be farther in some time periods, it does not fully account for those winter months.

The axis of the earth, the point around which it rotates, is tilted relative to the sun at about 23 degrees. A line drawn through the axis would point to the same position in space even as the earth moves around the sun.

So, as the earth revolves, different hemispheres are leaning either toward or away from the sun.

As a result, the sun's rays strike the earth at different angles. In summer, the angle is more direct, a sort of concentration of heat radiation. In winter, the angle is more obtuse, spreading the summer concentration over a larger area.

Suppose each yellow line represents 20 degrees Fahrenheit of the sun's heat energy. In summer, the small area receives 4 lines, about 80 degrees. In winter, a larger area receives the same energy that would have amounted to 80 degrees in the summer, but, being spread out, each locale is about 20 degrees. But remember, this is a very simplified explanation.

Parallax

One of the earliest arguments against the multi-dimensionality of outer space was parallax. It could've been the ruin of the Copernican Revolution.


To observe parallax on a small scale hold your hands out in front of your face with the left elbow bent at a right angle and the right elbow straight, but try to keep both hands at eye-level. Make certain there is a gap between your hands. Now, move your head to the left and watch the gap close and your right hand disappear. Voila, parallax! (Click pic.)

Parallax is the apparent shift in background (right hand) as the point of observation (head) relative to the observed object (left hand) moves.

Copernicus resurrected the heliocentric (sun-centered) model of our solar system, which was set to replace the geocentric (earth-centered) model. This, however, was difficult to prove given the unnoticeable parallax phenomenon. If the earth were moving, then how come the other planets' positions did not change relative to the stars? It should be mentioned that the stars were considered to be lined up on a single plane of their own, beyond the farthest known planet, Saturn.

Parallax wasn't proven until 300 years after Copernicus's model.

Another popular argument against the movement of planet Earth was the tower argument. Simply put, when a stone is dropped from the top of a tower, why doesn't it land many feet away from the base of the tower? After all, if the earth is moving, the ground beneath the falling rock would shift accordingly, causing it's impact to be a hypotenuse away from the tower's base...