You cannot see the wind, but you can feel it pushing you around.  You cannot see the flu, but you can sneeze and feel tired.  You can't see the things that make up your hair, but there it is, growing out of your head.  Earth is filled with invisible things that change our lives every day.  How do we know what they do and when they do it?  How do we even know that some of them are there?


To begin, Earth is made out of invisible things.  Atoms are the building blocks of everything you see around you.  They are so small you cannot even see them with a microscope.  So how do we know they are there?  It starts with a question.  What if we took one of your hairs and cut it in half, and then cut that half in half, and that half in half, and so on and so on.  Where would it end?  We would have to come to something so small that it couldn't be cut anymore, right?  With this idea, we can begin some experiments.  First, we can watch how gases act.  If a gas is something that is spread out as far as it can go, then we can watch how all of its small parts push up against other things.  We can also shave something down so that it's so thin, it is only as thick as an atom.  By shooting very small things at the thin sheet and watching how the small things bounce off, we can guess the shape of an atom.  Think of bouncing balls off an invisible elephant and you will get an idea.  If you throw enough balls, you will start to get a shape.  I do not think you should try this though.  There is nothing worse than a mad, invisible elephant.

That ought to be enough balls!
Photo by Julie Kertzse


People used to believe that colds were caused by bad spirits.  Walk past a graveyard or go outside on a windy day and you could come back with a cold!  We now know that this is not true.  Microorganisms are living things made of only one cell that cannot be seen with the naked eye.  We will use another experiment to show they are there.  This experiment is easy.  Leave a piece of fruit out for two or three weeks.  See how it starts to turn brown and grow white with mold?  This is proof that smaller living things are eating it.  Don't believe me?  Try rubbing another piece of fruit on something dirty, like the floor or a toilet seat.  (Do I need to tell you not to eat the fruit?  I did not think so.)  Does the fruit turn brown more quickly this time?  Does it grow other colored things on it?  You may have picked up a different microorganism.  To be honest, microorganisms are big enough that we could have cheated and peeked through a microscope . . . but where's the fun in that?

No thank you!


You may not know it, but Earth is always protected by a very big shield.  Of course, we cannot see it.  Magnetism is the energy from the tiny parts that move inside of something that pulls things into each other or pushes them away from each other.  There are some rocks, called lodestones, that will pull iron to it like . . . well, like magnets. After many tests with metals and stones, we found out that the Earth is one big magnet, always pulling one side of a magnetic metal to the north.  This is what makes compasses work.  After some tests with the sun's light, we figured out that we should be cooked by the light coming from the sun.  Lucky for us, the magnetism around the Earth bounces away most of the light that can hurt us.  There is one place on Earth that you can see this at work.  The northern lights look like white, green, or purple silk waving through the arctic night sky.  This is where we can see the parts of light that can hurt us crash into each other like waves in the sea.

And I thought magnets only made my compass point north.


Seeing is not always believing.  Just because we cannot see something with our eyes, does not mean it is not there.  It is easy to know some things are there, like the wind and things that make you sick.  But there are other things like atoms, microorganisms, and magnetism that are not so easy to find.  It takes thousands of years for scientists to think, test, and stumble upon the answers to things we cannot see.  So.  Keep your eyes peeled, your ears open, your skin feeling, and your brain working.  And always carry that wonderful word that will always be the best tool for any scientist: Why?


References:

How Do We Know?  "How do we know that atoms exist?"  How Do We Know.org, 2010.  <http://howdoweknow.org/index/atoms_exist.hdwk>

DSWA.  "Do Microorganisms Really Exist?"  DSWA, 2012.  <http://www.dswa.com/pdfs/gwm/Activity10.pdf>

How Magnets Work.  "History of Magnets"  How Magnets Work, 2006.  <http://www.howmagnetswork.com/history.html>