Bill Nye should be a Mefite.
July 6, 2009 7:13 AM   Subscribe

What are some simple experiments that help explain complicated phenomena?

I was at a geology museum last year, and they had an exhibit where water slowly trickled down an embankment of sand. The path the water took was a seemingly random assortment of forks and zigzags. The accompanying placard read, "This is how Earth's rivers were formed over millions of years." The kid in me just went, "OHHHH!!"

When I was 7, my older brother challenged me to a bet of what would hit the ground first if dropped from the same height (a tie would mean I was wrong): a sandbag or a pen cap. I lost a dollar. Then two. Three. Then he offered to let me try. Four dollars. Five. I quit in frustration. Then came back when he left and kept trying for a half hour, and I thought I was going insane. When 3rd grade rolled around and we began learning about gravity in science class, I was well ahead of the curve, $5 poorer yet $5 wiser.

During Seder this year, my cousins were presented with the Monty Hall problem, and after at least 30 mins. of discussion, they still would not budge on the odds being 50/50. So I came up with this experiment. "I'm going to write down a number between 1 and 1 million. Try to guess it. Can we all agree that you have a 1 in a million chance of getting it right?" (Yes.) The guess was 23. "Alright, I'm going to eliminate numbers 1 through 22, 24 through 625,624, and numbers 625,626 through 1 million. Now would you like to stick with your original guess, 23, or switch your answer to 625,625?" Their eyes lit up. Well, at least three of them. My fourth cousin stubbornly stood by 23. I challenged her to try being the "host," and halfway through, it clicked, and she started damning herself.

What other interesting concepts or phenomena can be broken down in simple terms/experimentation?
posted by Christ, what an asshole to Grab Bag (11 answers total) 39 users marked this as a favorite

It wasn't too long ago when atoms were kind of dismissed as an OK theoretical concept but obviously not how reality worked.

In 1905 Einstein wrote a paper* where he beat on Brownian motion with some math and said, you know, if there really were these atoms and they were zipping around in here ramming a pollen grain, you'd see movement just like Brown saw.

*He wrote some other papers that year. ;)
posted by Kid Charlemagne at 8:54 AM on July 6, 2009 [1 favorite]

Float a needle on water. You're demonstrating surface tension.
posted by kldickson at 10:09 AM on July 6, 2009

Obtain three sheets of polarizer film, which look like gray plastic. Look through two of them at a light source and adjust the angle between them so together they become pitch black. Now, insert the third film between them, angled at 45 degrees with respect to the outer two: you can see through them again.
posted by fatllama at 10:16 AM on July 6, 2009

The Game of Life shows really well how complicated phenomena can be generated from very simple rules and starting conditions, which is a pretty important concept in evolutionary biology. Note: this has nothing to do with intelligent design/abiogenesis.
posted by Midnight Rambler at 10:21 AM on July 6, 2009

Build a baking soda and vinegar volcano. There are several different things demonstrated there.
posted by Cool Papa Bell at 10:25 AM on July 6, 2009

Molecular bonds require energy to break. Stick ice into room-temperature water, and two things happen:

1) The ice melts
2) The water gets colder

The kinetic energy (heat) in the water is absorbed by the ice, which causes the molecules in the ice to become excited. Eventually they become excited enough to break their molecular bonds, and the freed H2O molecules become liquid water.

But wait, you say. The ice was cold to begin with! The coldness in the ice is what made the water colder!

Well, sort of. But a temperature difference is not strictly necessary.

To prove this, take a cup full of room-temperature salt, add it to a glass of room-temperature water, and stir. Again, two things happen:

1) The salt dissolves
2) The water gets colder

In both cases, the kinetic energy of the water is being used to dissolve a solid, which causes the water to become colder. Also notice that the colder the water gets, the harder it is for the salt to dissolve.

Note as well that the process is spontaneous. This is because it results in an overall increase in entropy: the crystalline structure of the solid becomes a disordered solution. If this demonstration is for a child, allow them to hold the chilled glass, and explain how one day the whole universe will be just like that.
posted by dephlogisticated at 10:49 AM on July 6, 2009

Lavoisier sealed a guinea pig in a box to show that "respiration is thus combustion".
posted by mhum at 12:02 PM on July 6, 2009

Slightly anti-social, but if you want to understand driven oscillations, give a lamp-post a shove. Estimate the frequency it sways at from that shove, then push it lightly at that frequency. Pretty soon it's going alarmingly, with minimal effort from you. You can do it with most large rigid metal structures (metal fences are also good, trees in my experience are too damped).

Experience the conservation of angular momentum for yourself on any office chair you like, if you can swing your arms fast enough.
posted by Wrinkled Stumpskin at 12:27 PM on July 6, 2009

adhesion & cohesion

Fill a cup to the brim & keep filling it until you get a curved bit of extra water on top, that's Cohesion (water sticking to itself). Put in a bit of soap & it breaks the surface tension of the water and ends that effect.

You've just demonstrated why soap cleans better than water alone.

Get some Capillary Tubes and watch water flow up the tube for a demonstration of Adhesion (water sticking to other things).

You've just demonstrated part of how trees take water from the ground & release it in to the air.

Chladni Plates demonstrate various properties of water & acoustics.

Baking Soda & Vinegar: You can use Baking Soda & Vitamin C too (read: alka seltzar). Basically Baking Soda & any acid work here.

Electroplating is fun & easy to do.
posted by MesoFilter at 10:42 PM on July 6, 2009

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