Science Never Sucks | Milk Bottle and Egg


Tami O'Connorby: Tami O’Connor

One of my all time favorite air pressure activities is an oldie and a goodie!  It involves getting an egg into a classic, hard-to-find milk bottle, like the ones Milk Bottle and Egg Demodelivered to grandma’s door.  Unfortunately, some students (and some teachers) still think an egg can actually be sucked into a bottle.  As you probably know because the air pressure is greater outside of the bottle than inside, the better explanation is that the egg is literally pushed into the milk bottle.

Here is the explanation… The milk bottle and egg demo begins by placing two or three burning matches or a burning strip of paper into the empty bottle.  Then a shelled, moistened hard-boiled egg is placed on the mouth of the bottle.  The egg is clearly larger than the opening in the bottle.  The air inside the bottle begins to heat up and subsequently expands.  It is easy to notice the egg dancing around a bit as the air inside the bottle escapes around it.

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Chladni Plates


Martin Sagendorfby:  Martin Sagendorf

An Odd Name: They’re named for the German physicist Ernest Chladni who popularized them in the mid-1700s.  His name is pronounced: kläd’nêz.

Chladni Plates are: Thin plates (sprinkled with fine particles) vibrated perpendicular to their plane.

How? – Then and Now: Long ago Chladni used a cello bow to excite the edge of a thin metal or wooden plate.  Today, we can use an oscillator, amplifier, and an electro-mechanical oscillator.  We have a great advantage, we can easily vary the frequency of excitation thereby providing a whole vista of experimentation.

A 17 in. x 14 in. Chladni Plate in guitar shape at 200 Hz

Chladni Plate Read the rest of this entry »


Making Optics Demos Easier


Martin Sagendorfby:  Martin Sagendorf

We’ve all likely encountered the time-consuming effort required to set up an optics demo; all the necessary components are on hand, but they don’t easily work together.  The difficulty is obvious: the various components are either ‘loose’ or mounted at differing heights.  Thus: wasted and frustrating time ‘shimming’ with books and pads to match the heights of the components.

The solution is simple: choose a height (above bench top) and mount every optical component at the same (optical centerline) height.  But, how does one choose a height?  Simple: first, determine the optical component with the highest centerline then second, build supports for all the other components – matching this centerline height.

I began with a 100 Watt clear light bulb mounted upon a wooden base – the center of the filament was 4-3/4” above the bench top.  I then ensured that everything else I had, or planned to incorporate in demos, could be centered at this height.

Optics Demo

The supports shown in the following illustrations are of ¾” pine – either screwed or glued together.  Where required, various combinations of rubber feet and jackscrews provide support and positioning capability.  When applicable, stacks of steel washers are incorporated to add stability. Read the rest of this entry »


Meteorites


Ted Beyerby:  Ted Beyer

Ever since I was a kid, I have been fascinated with space. I would look up at the stars, and I just knew that other people were up there somewhere, looking back at our little point of light, and thinking the same kind of thoughts. When I was 7 years old, Neil and Buzz landed on the moon, and I was sure that somehow, when I grew up, I would get there, too. (incidentally, that’s me in the red on the right in the picture–and on the left? Well, that’s Buzz Aldrin!)Ted Beyer and Buzz Aldrin

Dreams can be dashed by reality and time, but the desire can still live on. I became a collector of all things space…and NASA…and then I found that collecting meteorites was not only possible, but also fascinating. Here are objects that spent millions of years wandering through space, only to endure a fiery entry through our atmosphere to end up, astonishingly, in my hands.

The more I researched these space travelers, the more I became fascinated with their vast variety and appearance. When most people think of meteorites, they tend to think of the Nickel – Iron type (or at least I did). Heavy metal, often pockmarked, objects, dull black or grey. Wasn’t I surprised to discover that the Irons make up only about 6% of FOUND meteorites, by number, and 11.3% by weight. In collections, they make up 27.7%. The Chondrites (one form of the stony meteorites) make up 75% by weight and 85% by number found!

Meteorite FragmentIn spite of this, my small collection still only has one stony. My one and only stony (so far); pictured to the right, is a slice of the Ghubra meteorite, which was found in Oman in 1954.  See the white spot on the bottom left side of the specimen?  I am assured by experts that the spot, called a chondrule, is older than the planet Earth by as much as 500 million years! Read the rest of this entry »