ChemCam Question

What would happen if the ChemCam laser shot at a piece of glass?

ChemCam is a device on the Mars Science Laboratory rover, Curiosity. It consists of a powerful laser which is trained through a telescope on a mineral target, A tiny spot on the target is heated to a plasma, and flashes with wavelengths of light that give away its composition. The ChemCam telescope collects some of this light, relaying it to a fiber-optics cable to a series of spectrometers in the body of the rover. The spectrometers analyze the light and report their findings back to scientists on Earth.

We were asked this question by a student in one of our programs, and we asked our friend Roger Wiens, who is one of the co-principal investigators for ChemCam. Roger told us:

"These students have good heads on their shoulders! The laser would not spark on a piece of smooth glass. But if you roughen up the surface with sandpaper the glass would lose its transparency and you would get a spark."

We are reminded of the time we tried to roast a marshmallow in our solar furnace. The marshmallow is so white that it reflects the heat quite well. Then we tried rolling it in cocoa powder. . .

Trinitite

We are asked from time to time where one can get Trinitite, the glassy mineral caused by the test of the "Gadget" atomic device at Trinity Site on the White Sands Missile Range. For several years after the test, the material was poached from the site by the truckload. It was never officially distributed, and there is no guarantee that any glass called Trinitite is authentic without very exacting analysis well beyond this writer's understanding.
That said, we have been told that there is enough out there in circulation that it is unlikely that anyone would go to the trouble to try to make counterfeit Trinitite. As to where to buy it, we will leave that up to the resourcefulness of our readers.

Comparing Hardness of Rocks

We were asked how students can compare the hardness of different rocks, especially scoria and volcanic tuff.

To compare two different materials’ hardnesses, one approach is to try to scratch one with the other. We suspect, although we haven’t tried, that you will find the scoria scratches the tuff and not vice versa. This method is used by gemologists, who know that a rock that can be scratched by a common steel nail will be too soft to take a high polish. Steel is just about the perfect hardness to make this determination. Agate is harder than steel and polishes to a high luster, limestone is softer and remains dull no matter how long it is polished. A diamond should be able to scratch almost anything, and talc shouldn't scratch anything.

Ultimate Source Of Nuclear Energy

We have been asked during our energy program how nuclear energy fits into the mix when all of our other forms of energy derive ultimately from the sun.

The tie-in is actually pretty interesting. Most of the energy we use comes directly or indirectly from the sun, which is “burning” hydrogen created during the Big bang. Stars fuse hydrogen atoms into heavier elements only up to iron. The planets, and all the elements heavier than iron (further down the periodic table) are composed of stuff created in supernovae, dying exploding stars, that preceded the sun. Only a supernova is energetic enough to create the exotic and unstable elements up to uranium. So nuclear reactors, which run primarily on uranium, ultimately derive their energy also from stars, although not our sun.

Cross Puzzle with 4 pieces

You asked if the puzzle in TechLab with four pieces actually reassembles into one large square.

 Two small squares are easy.

The hint posted alongside this puzzle is that the square has twice the area of the cross. The only way this can be, using the same four pieces, is if the square has a hole in it with the same area as the cross. We will be the first to admit this is a sneaky solution.

In this case, the hole is actually the same shape as the cross. The drawing shows the cross pattern with one piece rotated into position as a corner of the square pattern.

Thorium Nuclear Power questions

We were pleased to get this question because we had just read an article about it. One of the challenges with thorium for reactor fuel is that it has been historically very expensive, monetarily and environmentally, to process. There is a project at LANL that has taken on thorium chemistry. It is called Th-ING, Thorium Is Now Green. This team has developed a much cleaner and much cheaper way to process thorium that avoids exotic chemistry, high temperatures, etc. It sounds very promising. There is a technical article about Th-ING at: http://www.lanl.gov/science/NSS/issue2_2011/story6full.shtml .

By the way, another development happening here is a program experimenting with sandwiches of materials with atom-thick layers of, for example, copper and niobium, that results in a sheet with not only extraordinary strength, but an ability to repair itself, or heal, from radiation damage. These materials may one day serve to shield or replace materials used in nuclear reactors today that become brittle with continued exposure to radiation.

"Work" and the scale of atoms

The word “work,” in physics has a special meaning, and is, as you said, defined as force multiplied by distance. Yes, if the object we are working on doesn’t move, we are not doing any work. This goes against the normal every day usage of the concept work. I sat all day today working at my computer, but I did very little physical “work.” There are a number of words that can get us tangled up like this. There is a wonderful glossary of misused science terms at http://www.lhup.edu/~dsimanek/scenario/physlang.htm

About things the size of atoms. An atom is less than one ten-billionth of a meter across. (Squeeze a meter stick into a millimeter on a second meter stick, and then squeeze the second meter stick into another millimeter, and the smallest meter stick can measure ten or twenty atoms across one of its millimeters!) If an atom were the size of a big football stadium, a proton or a neutron would be about the size of a tennis ball an entire nucleus may be the size of a soccer ball. At that scale an electron would still be nearly invisible, maybe actually invisible, but in any case still incredibly tiny. As I understand it, the strings people talk about in “string theory” are about as much smaller than an electron as the electron is smaller than the atom. Atoms are too small to see with light, so it is small wonder (ahem) that we have no direct evidence of strings.

Technology advances, though, and each step along the way, every lesson we learn, every question we ask opens up a world of new mysteries. The string theorists hope that the Large Hadron (Protons and neutrons are hadrons.) Collider in Switzerland and France will lead them to data confirming or at least supporting the theory. It is good to know there will still be questions and more bigger machines to build after the LHC is running. :-)