Arizona Road Trip

I am currently on vacation in Arizona. It's really interesting here. For one, there are cool plants here that aren't where I live - like palm trees, and cacti taller than houses. For another, the weather is really nice; sunny  most of the time, and not too cold.

To get to the place we're staying, my family drove for two days, from Colorado through New Mexico to Arizona. Here are some of the photos I took along the way (just click to view):

Polarized Light

What exactly is polarized light? You may have heard of it before, or read the name. It sounds cool, so what is it? That is what I will explain in this post.

Light is like a wave, or bumpy curve, in many respects. This wave is a sine wave (see my Sine and Cosine post). The wave can oscillate (wobble) in an up-down motion, or a left-right motion; sometimes it does a mixture of both, and wobbles in a circular pattern.

Look at the wall, or the floor. There are quadrillions of light waves bouncing off them. Some of the light waves oscillate in an up-down motion, others oscillate in a left-right motion, and others oscillate in a diagonal motion. The different types of waves are all jumbled together. Is it possible to have a bunch of light waves that all wobble the same way? Yes! Light like that even has a name: polarized light.

You can buy filters that will polarize light; the filters are called polarizers, or polarized filters. Some sunglasses are made with polarized lenses; those are called polarized sunglasses.

There are many uses for polarizers and polarized light. I will discuss some of these uses in later posts.

Sine and Cosine

Trigonometry is the study of the relationship between the angles and sides of triangles. The two most essential parts of trig are the functions sine and cosine. Both take an angle, and return a number. The way they work is really quite simple.

A diagram showing sine (abbreviated sin) and cosine (cos)

To find the sine of the angle θ, draw a circle with radius 1 on a graph, and put the circle's center at the origin of a graph. Find a point on the edge of the circle. The point makes an angle with the center of the circle; make sure that the angle is θ. Sine of θ is the point's y-coordinate. Cosine is the point's x-coordinate. (See the picture to the right.)

Sine and cosine are very useful for calculating heights and distances. For example, let's say somebody needs to know the height of a sky scraper, but isn't able to measure it physically with a tape. If he walks a certain distance away from it, and looks at the angle it subtends in the sky, he can use trigonometry to figure out its height.

But that's not all. If you graph the sine function, you get a cool wavy line the shape of a ripple in water. That curve is called a "sine wave". The same curve is also the building block for the shapes of sound waves. Who said math had to be boring? Not I.

The Geminids

The Geminid meteor shower is coming up! At 2:00 AM, on December 14 (that's Thursday night, or Friday morning), you can see anywhere from 100 to 150 meteors per hour - depending on the sky and weather conditions. That's more than 1 meteor per minute!

This particular meteor shower comes from a 5.1 km wide asteroid called 3200 Phaethon. Flecks of debris fall off this asteroid in a trail around the sun. These bits are called meteoroids.

Every year, in December, Earth passes through this stream of meteoroids; when one of them enters Earth's atmosphere, it burns up and we see a meteor. If the meteor is brighter than Venus, it's called a fireball. Fireballs are much less common than meteors.

This year, viewing conditions will be especially good; the peak occurs only 1 day past new moon. If you live in an area with lots of light pollution, you will definitely want to drive into the country. If you think the weather will be bad, go out a day or two before or after the peak. Keep warm, and good luck!

Night Turns to Noon

You might want to check out my Blue Moon post before you read this one.

It was late at night. The full moon lay high in the starry sky. Suddenly, everything started getting brighter and brighter, until the moon was as bright as the sun, and everything looked the way it does in the middle of the day - except for the glaring light pollution and the burning stars. Astounded, I pulled out a camera and snapped the photo above, and some others you can see in my Blue Moon post. About an hour later, everything went back to normal.

Does that sound like a true story? Well, it isn't; that night was just like any other. To take the photos, I used a trick that I will explain in this post.

When a digital camera takes a photo, this is what happens: a shutter on the front opens up, and a lens focuses light onto a tiny charge-coupled device (CCD) inside the camera. When the light hits the CCD, a small electric charge becomes present. As more and more light hits that part of the CCD, the charge gets stronger and stronger. Different parts of the CCD have different charges, depending on how much light they get.

After a certain amount of time, called the exposure time, the shutter closes, and the camera converts all those charges on the CCD into an image. The bright parts of the image correspond with stronger charges on the CCD, and vice versa.

Now let's go back to the photo I took in the moonlight. Since it was dark outside, the charge on the CCD would have been very weak, resulting in a dark image. But what if there were a way to make the charge stronger? Then I would have a much brighter image; if things worked well, the image might look as if it were taken during the day.

The trick is simple: change the exposure time. If you set the exposure time higher, then the shutter will stay open longer; the charge on the CCD will be much stronger, and you will have a much brighter image. That's what I did, and the results (not to mention the bragging rights) are certainly worth the time.

Hopefully this post explained some things about cameras and tricks. If you can remember what I said, and can put it into practice, you're well on you're way to becoming an expert photographer. Finally, here's a tip: if you're trying to take a "daylight" photo, don't let any houselights get in the picture. They'll get brighter too, just like everything else.

The video above shows a series of photos taken with different exposure times.
The first photo has the shortest exposure time, and the last one has the longest.