Sunday, October 18, 2009

How Small is an Atom?


A textbook or encyclopedia will tell you that a typical atom is about 0.0000001 of a millimeter in diameter. Now, how are we supposed to picture that? That information may be helpful for calculating how big a carton you'll need for mailing a given number of atoms to someone, but then again, maybe not. It certainly doesn't help the typical person understand what all the fuss is about.

Here's a way you can visuallize the size of an atom, and the vast number of atoms that comprise the everyday objects in your world. For this experiment, I'd like you to get a pin. Find an ordinary sewing pin, now, before reading any further.

Got one? Good. Look at the head of the pin closely. If you have one, use a magnifying glass or even a microscope to look long and closely at the head of the pin. Just stare at it for a while.

Now close your eyes and imagine yourself shrinking down, almost vanishing, descending down onto on the head of the pin. You have shrunk down so small that the head of the pin is a vast desert on which you are standing, the edges of which you cannot see. You begin walking in one direction.

You continue walking on the head of the pin for many days before coming within sight of the edge. How far have you walked? 50 miles? 100 miles?

For the first time, you look down at the surface you have been walking on. It's fairly smooth, with an occasional ditch to stride over and variations up and down. You recognize this as the results of polishing when the pin was manufactured. You kneel down for a closer look at this shimmering surface and notice that it seems to be made up of small marbles packed closely together, and they are all vibrating slightly. Now you are seeing individual atoms. There are mostly iron, but also nickel, copper, and several other species, distinguishable by their differing sizes.

Open your eyes and look again at the head of the pin. You will now be able to visuallize how small atoms are and how impossibly many there are just on the head of that pin.

Now I'd like you to picture yourself on the beach. Next time you go to the beach, remember this and go through these steps. Stand on the beach and look up and down the shoreline. Picture in your mind how deep the sand might be. Deeper than a house is tall? How much sand?

Reach down and pick up a handful of sand. How many grains of sand do you see? Could you even begin to count the number of grains of sand you are holding in that one handful?

Allow most of the sand to fall through your fingers. Inevitably, a few grains remain clinging to your skin. Look closely at your hands, and try to pick out one single grain of sand.

While looking at that one grain of sand, say the following words: "There are possibly more atoms within that single grain of sand than there are grains of sand on this entire beach."

It is no wonder then that the existence of atoms was completely unknown for so long, and then, debated for so long. By about the start of the 20th century, the indirect evidence of atoms from observations made over the previous few hundred years had finally won over most people to the concept and existence of atoms. Now, we have technology that can directly image the atoms on the surface of a grain of sand or on the head of a pin.

Of course, Mankind has gone far beyond that and has probed the very inner workings of individual atoms and the parts they are made of. That will be the subject of a future post.

14 comments:

  1. Very good article. Thanks for taking to trouble to do all of this. :)

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  2. Brilliant. There are not enough articles on the internet that describe science simply and engage the readers imagination.
    Thankyou

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  3. great article. you really helped me visual just how small an atom is.

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  4. You say close your eyes 4 but how are you meant to read with your eyes closed?

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  5. I was taught to get an idea of size of water molecule.
    If every molecule in a standard glass of water was converted into a grain of sand, The sand would cover North America 10 feet deep?

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  6. Nicely explained. I will have my students close their eyes as I read this to them. Thanks!

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  7. very comprehensive...articles like these are hard to come by

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  8. Thank you so much.. This article made it very simple for to help my 10 year old understand how small an atom really is.

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  9. I am a 10 year old boy. it helped me a lot . I love learning about quantum mecheichs.

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  10. love it 10 years old

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  11. Thank you so much.. This article made it very simple for to help my 10 year old understand how small an atom really is.Very comprehensive...articles like these are hard to come by. I was taught to get an idea of size of water molecule.
    If every molecule in a standard glass of water was converted into a grain of sand, The sand would cover North America 10 feet deep?

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  12. Very good article. Thanks for taking to trouble to do all of this. ;P

    ReplyDelete