White Light

When we look at the light coming from a light or the Sun, we see it as white, for the most part. But it’s more.

There are three main colors of light – red, blue and green. These three main colors combine to make all of the different colors we see. The colors are how our eyes interpret different wavelengths of light. Short wavelengths are seen as blue, medium wavelengths are green, and short wavelengths are red. The wavelengths in between are the colors inbetween - orange, yellow, and blue. When all of the colors are mixed in equal parts, we see white.

When you shine white light through a prism, you separate the wavelengths of light. Each wavelength bends at a different angle, spreading them apart. And that’s why we see a spectrum. Rainbows are formed the same way, only the light is bent by droplets of water, not a prism. Sometimes, if conditions are right, the light gets bent again and forms a secondary rainbow. In the secondary rainbow, the colors are inside out. Normally red is on the outside and violet on the inside, but on a secondary rainbow it's the violet on the outside and the red on the inside. See for yourself. The secondary rainbow is faint; you may need to click on the picture to enlarge it to see both rainbows.

(photo from Wikipedia Commons, by Eric Rolph)

Wikipedia article on color

Why does poo stink?

Thanks to Brad for this question! Poo stinks for a few reasons. Any undigested food is starting to rot, and that’s smelly. But most of the smell comes from the gases produced by bacteria. If you took the water out, most of what was left would be bacteria. Theses bacteria produce many different gases, including methane and sulfide compounds, all of which are stinky!

More than you ever wanted to know about poo

Bryozoa

You need to watch the video on this one first

What in the heck IS that thing?!? It’s a type of animal called a bryozoa. They’re colonial, which means they’re made of many tiny organisms that live together. Pretty freaky, huh?

Wikipedia article

Blue whales

Okay, sure, you know blue whales are big, but do you know how big they REALLY are?

They’re bigger than any dinosaur that ever lived. The largest blue whales are estimated at 200 tons, while the largest known dinosaur was 99 tons.

A blue whale’s lungs can hold 1300 gallons of air.

Its tongue weighs 3 tons.

Its skull is about 20 feet long.

Its heart is the size of a Volkswagen Beetle.

A baby blue whale is born the size of an adult hippo and drinks 100 GALLONS of milk a day. My four month old daughter drinks approx. 24-28 OUNCES a day.

Blue whales need 1.3 million calories a day. You probably need about 2000.

Cheetahs; one big happy family

Cheetahs are one of the most recognizable animals in Africa. They are currently listed as “Threatened” which their numbers are low. What a lot of people don’t know is that they almost died out long ago. Sometime around the last ice age their numbers dropped very low. The survivors interbred, which means that all cheetahs are descended from this small group of individuals. As a result, they are all very closely related. This was confirmed when scientists performed an experiment. They took skin grafts from several unrelated cheetahs and grafted them onto different cheetahs. In humans, any sort of transplant like this requires drugs to suppress the immune system – otherwise, your body will reject the new skin because it’s too different from you. But in the cheetahs, there was no problem at all. They are so genetically similar that their bodies accepted the skin as part of themselves!

Unfortunately, this causes problems for the cheetahs. If one of them is susceptible to a disease, then it means ALL of them are. One virus could wipe out the entire population. And that’s why scientists and conservationists are trying to help save this beautiful animal.

Wikipedia article on cheetahs, including a picture of the rare King Cheetah.

Why do people tan?

People have three pigments in their skin. This is what gives you your
color. There’s a yellow pigment, pink, and a brown pigment called
‘melanin’. Today we’ll be talking about melanin. If you have
dark skin, you have a lot of melanin, and if you’re light skinned, you
don’t. And, you guessed it, medium skinned people have a medium amount
of melanin.

When the UV radiation from the Sun hits your skin, it causes damage. So
your body reacts to prevent further damage. It produces more melanin.
Melanin absorbs the Sun’s radiation so it can’t enter your skin
cells and damage them. This increase in melanin is what causes a tan.

People with dark skin have more protection from the Sun. Their
ancestors came from places with a lot of bright sunlight, like the
tropics. But you need some sunlight to enter your skin. That’s how
your body makes Vitamin D. People with dark skin who live in bright
sunny places are fine. But if they live in colder, darker places, then
they need to make certain they get Vitamin D in their diet.

People with light skin absorb a lot of sunlight very quickly. Their
ancestors lived in places that were cold and darker than the tropics. We
often use the term “Caucasian” to describe these people. The Caucaus
Mountains are in Russia, which is cold and darker. So the people that
live there have light skin. When you spend most of the year covered up
in heavy, warm clothes, with only your face and hands exposed to
sunlight, you need light skin to absorb enough sunlight to produce
Vitamin D.

People who live in the areas in between the extreme north and the
tropics are in the middle. The temperature and the amount of sunlight
are both sort of medium. So people who have lived in these areas for
very long periods of time (I’m talking thousands of years) have medium
skin.

Why do leaves turn colors in the Fall?

Plants have tiny little organelles in their cells called chloroplasts. Chloroplasts are where photosynthesis happens, so they contain an important pigment called chlorophyll. Chlorophyll is green. (See yesterday’s post for an explanation). But chloroplasts can only use some of the light from the Sun.

To use other colors (other wavelengths) of light, plants have other pigments that capture other colors. They also reflect different colors than chlorophyll, so they appear to be different colors. Carotenoids, for example, appear yellow to orange. These pigments are in the leaves all year long, but there isn’t very much of them. There’s a LOT more chlorophyll, so it covers up the other pigments and we see the plants as being green.

In the fall, when the leaves start to die, they lose their chlorophyll. The other pigments are now visible, with all of the splendid colors of autumn.

An article giving another explanation