Try Some Science: September 2012

The phrase, "Science is Magic" is one that needs to show itself to the door. This Target ad puts it right out there in an effort to get you to buy Graphic Tees and Converse One Star Tennies! Despite this, I personally love the fact that target is selling stuff with science. I much prefer that to them selling things with teen celebrities. The Van De Graff generator in the ad is a nice addition, especially since I have had friends get married under the largest VDG in the world at the Museum of Science in Boston. The problem is that despite science being MAGICAL, it is not MAGIC. It is not illusion, science is testable and provable. It is true that often science will be surprising, make you think, change your worldview, and so much more. When it does this, it feels like watching magic. Those are the best parts of science,
and today's post will touch on one of those topics.

It's All Smoke and Mirrors:

We have all seen some variation of the magic trick where the assistant drops into a covered box from the top but is really going behind a mirror. When the sheet is removed, POOF, no person, because the mirror is showing you a different part of the stage. Though we don't see the assistant, they are still there. Something, in this case the mirror, is covering them up and obscuring them from view. I found directions to make your own magic mirror box online, or this magic kit (right) probably even comes with its own mirror box. I bring this up, because as we look around this fall we are seeing the magical side of nature, the changing color of leaves. But wait! See those colorful leaves changing outside? That is your mirror of science. The orange is always there, but the green fades away!

Leaves are the energy factories of the tree. Sunlight hits the leaves and starts a chain reaction that ends with the production of glucose. We know this process as photosynthesis:

"Photosynthesis" By: TMBG

The biochemical process is relatively complex, but the important note is that visible light enters the leaf and promotes an electron to a higher energy. This is not the easiest process, light hits things all of the time and does not always move electrons. Humans have designed materials that are capable of this process, solar cells. The most efficient human-made solar cells have about 40% efficiency. It is hard to compare that to plants, because solar cells do not make corn, but some people have tried to quantify the process and found that solar cells can be more than 10 times as efficient as plants. That said, solar cells don't come the size of a seed and grow themselves into a power plant (no pun intended) either!

In order for the plant to use light to promote an electron, a specialized molecule has developed called chlorophyll. There are many variations on chlorophyll, but they all have a porphyrin center that cradles a magnesium ion.

Depending on what other groups are around the porphyrin, the chlorophyll absorbs light of varying wavelengths. The wavelength of light determines its color, and anything not absorbed is reflected. Chlorophyll does not absorb well in the 500-600 nanometer (nm) range. As a result, plants are green! Because of its complexity, the second the tree starts to limit the nutrient supply to the leaves, chlorophyll is one of the first molecules to degrade. What is left behind are carotenoids and flavenoids, which make up the yellow, oranges and reds of the fall foliage. Carotenoids are what give pumpkins, squash, and tomatoes their color as well.

These molecules are always there, they just don't get to show off until the chlorophyll degrades. It is MAGICAL! Eventually, they too degrade, which is why leaves turn brown before too long. Want to see this at home? Here is a way to separate all of the molecules with items you can find around the house as well as a few leaves from the yard (Leaf Chromatography). If you want to jump to the result before you try, here is a video from YouTube:

If you are looking outside the next several weeks, you will see that chlorophyll degrade. Now you see it, in a month you don't! That's way better than magic any day.