Approximately 48 million miles from Earth, Mercury is the smallest planet in our solar system, and also the closest to the sun. These three facts combined explain why scientists have such a hard time observing Mercury’s surface—compared to most of the other planets in our cosmic neighborhood, we know almost nothing about it.
This Demo Science science demo will help your students understand how Mercury’s proximity to the sun makes it difficult for researchers to get a good look at the planet. (You’ll have to derive your own experiments to show how Mercury’s size and distance from Earth contribute to these complications.)
CAUTION: Do Not Look Directly Into the Sun Lamp
Here’s the skinny for this one: you’ll need a desk large enough for all your students to stand around—presumably, your classroom already has one of these; a desk lamp, perhaps two, so you can position one at each end of your desk so the kids don’t have to crowd each other too much; and enough identical pencils for each student to use one. The pencils should also have some sort of writing on them beyond the #2 thing—doesn’t matter what it says, as long as it’s words that can be read.
Have all the smelly little booger-eaters you’re teaching gather ‘round your desk, with the lamp or lamps in position. Make sure the bulbs are facing up and out—toward the kids’ faces, essentially. BEFORE you turn the lamp(s) on, be sure to warn your students not to look directly into the blazing bulbs. (Kevin, I’m not kidding! Stop it! You know what? Fine. Go blind if you want. Don’t say I didn’t warn you.)
Turn the lamp(s) on. Have your students hold their pencils at arm’s length, with the print facing them. Then, have them shuffle forward carefully, without looking into the light (Kevin!), until their grubby little mitts are about a foot to six inches from the bulb before them.
Now, ask them to read the print on the pencil. If they can!
What your students other than Kevin will notice is that the print on their pencils is essentially impossible to read, and even the color of the pencil itself will be hard to determine. This is because the light behind the pencils is so bright, and a pencil is too small to block out much of the lamplight.
This is the same effect seen by scientists trying to get a good gander at Mercury. Mercury, like the pencils, is very close to the sun (the lamp of our solar system) and very small in comparison to the sun/lamp. When astronomers try to observe Mercury through their telescopes, they’re more or less looking directly into the sun, which blows out their view of the planet.