Friday, March 14, 2014

This Day in Science History - March 15 - Josef Loschmidt

March 15th is Josef Loschmidt's birthday. Loschmidt was an Austrian chemist who is best known for his close estimation of the size of air molecules. His value was nearly twice the actual size, but the correct order of magnitude. He also is known for the Loschmidt constant which sets the number of particles in a given volume of an idea gas as a constant. This value of 2.687 x 1025 particles per cubic meter at STP is occasionally confused with Avogadro's number in textbooks.

What Is the Difference Between Smoke and Steam?

Can you tell by looking at this plume from this factory whether it is releasing smoke or steam? Both smoke and steam can appear as clouds of vapor. Here's a closer look at what steam and smoke are and the difference between them.


Steam is pure water vapor, produced by boiling water. Sometimes water is boiled with other liquids, so there are other vapors with the water. Ordinarily, steam is completely colorless. As steam cools and condenses it becomes visible as water vapor and can produce a white cloud. This cloud is just like a natural cloud in the sky. It is odorless and tasteless. Because the humidity is very high, the cloud may leave water droplets on solids that touch it.


Smoke consists of gases and soot. The gases typically include water vapor, but smoke differs from steam in that there are other gases, such carbon dioxide and sulfur oxides, plus there are small particles. The type of particles depend on the source of the smoke, but usually you can smell or taste either the soot or some of the gases from smoke. Smoke may be white, but more commonly it is colored by its particles.

How to Tell Smoke and Steam Apart

Color and odor are two ways to distinguish smoke and steam. Another way to tell smoke and steam apart is by how quickly they dissipate. Water vapor dissipates rapidly, particularly if the relative humidity is low. Smoke hangs in the air, since the ash or other small particles are suspended.

3D Frozen Bubble

I had some time to kill while waiting for the aurora borealis in Fairbanks, Alaska, so I got some bubble solution and went out into the subzero weather to blow bubbles. Here's a Lytro lightfield photo of a frozen bubble. If you look closely, you can see the front of the ice crystal growth.

If you want to make frozen bubbles with pretty crystal patterns, my recommendation is to find a cold, still day, blow bubbles, recapture the bubbles on the bubble wand, and set them down on a level surface to watch them freeze. You want the temperature to be below freezing, but not so cold that the bubbles freeze almost instantly

Why Ping Pong Balls Are Flammable

If you play ping pong or table tennis, you used to have to carry around several balls, since they would occasionally ignite or explode upon contact with the paddle. It's unlikely a modern ping pong ball would ignite during a game, but they remain extremely flammable. If you touch a flame to a ball, it burns from the point of contact evenly around to the other side, leaving only a delicate mesh, the strip of adhesive used to join the halves of the ball, and a fairly vile stench. Except for the smell, it's actually kind of cool! Some people think the balls are filled with flammable gas, while others think it has something to do with the plastic used to make the balls... Find out who is right

DIY Magnetic Silly Putty

Putty, specifically Silly Puttybut if you have putty, you only need one more ingredient to make DIY magnetic Silly Putty.
, is a cool toy that was originally marketed as an Easter novelty (which is how it came to be sold in eggs). The newest version of the toy is magnetic putty, which is a viscoelastic polymer, just like regular and glowing putty, plus it's magnetic. You can't make Silly Putty yourself unless you have some silicone oil and boric acid to produce polydimethylsiloxane

DIY Magnetic Silly Putty

You will need:
  • putty
  • magnetic iron oxide powder
  • strong magnet (recommend neodymium rare earth magnet)
  • paper face mask so you don't breathe in the iron oxide dust
  • disposable gloves because it's a messy project
You can find iron oxide powder online or at some craft stores, where it may be sold as a black pigment. This is basically ground magnetic hematite. There are other forms of iron oxide, too, which are not magnetic, so be sure to get the right kind! Test it with a magnet if you aren't sure you have what you need. If you are truly desperate, use rust, which is the everyday form of this chemical.

Do the Northern Lights or Aurora Make a Sound?

One interesting science mystery involves the aurora borealis or Northern Lights. Some people report hearing a sound when the auroral display is visible in the sky. Scientists have not detected a sound emanating from the aurora, at least within the range of human hearing, and any sound coming directly from the aurora would be delayed, yet the reports are too frequent and credible to be discounted. Right now, the thinking is the best way to determine the mechanism for the sound is to collect more reports of experiences. So, if you have heard the aurora, take a moment to share your story.