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Bradbury Science Museum

Favorite Science Questions

You asked, we answered.

How can we fix the ozone layer?

You asked a very interesting question about ozone and how can we fix the ozone layer.

It is true that lightning creates ozone. Any spark in air will do it. Ozone can also be created by certain forms of radiation. Ozone is a molecule of oxygen that consists of three atoms instead of the usual two. It has peculiar chemical properties, it is highly reactive, and at ground level it can be toxic to people and contribute to health hazards like smog.

Unfortunately, the ozone created by lightning is all in Earth's troposphere, below about 50,000 feet, the part of our atmosphere where weather happens and life flourishes. Fortunately, although thunderstorms are constantly happening all across Earth's surface, they don't create enough ozone to be much of a problem.

The ozone layer that protects organisms on the surface from ultraviolet radiation is in the stratosphere, above 50,000 feet. Here there is good and bad news, too. Ozone is created when oxygen absorbs the energy of ultraviolet light. So UV light makes ozone, and ozone absorbs even more UV light. Nature itself can take care of us, if we don't mess it up too much. That is the bad news. Some chemicals we have added to the atmosphere over many years react with ozone and break up the molecules. We have stopped using many of the nastiest ozone depleters but they break down very slowly and continue to destroy ozone. Eventually, we hope, these chemicals will wear out, and the stratosphere will be back to the way it once was, more or less. Human activity still continues, and we have to make intelligent decisions about risks.

While I was researching my answer, I found two interesting websites:

Human battery exhibit

The exhibit you describe has four large metal plates, one each copper and aluminum on each side of a meter. The copper plate on the left is connected through the meter to the aluminum plate on the right and the other two plates are connected in the reverse direction. The meter measures micro amperes, or millionths of an amp of current, so it is very sensitive.

Placing one's hands on plates connected across the meter causes the needle to deflect. This is because we, the human, are acting as the electrolyte in a battery. The two metals have different affections for their electrons, and the one that is greedier steals electrons from the one more generous through our bodies. This causes an imbalance between the two plates which is corrected by the current through the meter.

A typical visitor gets a modest reading on the meter. Sometimes a person is able to easily pin the meter at one end of its range. There might be a number of reasons for this. Larger hands and greater pressure produce more current. Moister hands work better than dry hands. I don't know if this is a real affect, but I have an impression that it is common for women to get higher readings than men. I can't imagine an explanation for this, and I am pretty good at making stuff up. I doubt it is because the average man has a greater wingspan than the average woman, but I really don't know. There is also probably a day-to-day variation with an individual depending on personal chemistry, hydration, sweaty palms, etc. I have never studied that, either.

How many babies were born in Post Office Box 1663?

This question sent us asking Alan, the Lab Historian, for help:

I received the following reply this afternoon from our historian. I am astounded! The 80 in the first year would mostly have been conceived off 'the hill.' The Manhattan Project arrived here in March. Many of the rest would have been the result of local efforts.

Quoth Alan:

"I haven’t been able to find an exact number, but you might find this quote from Jon Hunner’s, Inventing Los Alamos, helpful:

'Eighty babies were born the first year, and ten newborns arrived every month thereafter' (p. 39)

That’s essentially a shade under 300 babies born in Box 1663 during the war."

Stripes in video of atmospheric atomic bomb tests

We have been asked several times what are the vertical stripes in videos of atmospheric atomic bomb tests.

I wondered about this for a long time when I first came to the museum. The streamers you see in film of atmospheric nuclear weapons tests were smoke trails made by sounding rockets fired just before the detonation. They were used to make a sort of graph paper in the air for recording the propagation of shock waves and wind currents from the explosion.

A current project under way at Los Alamos uses something like confetti, numerous high definition video cameras, and super computers to try to build a three dimensional model of the turbulence downstream from a wind turbine tower. They are using the multiple points-of-view and the computers to track each individual speck of paper. I think the paper is dispersed upwind of the tower using a sounding rocket and a conventional firework explosive. Some technologies are just too much fun to leave on the shelf.


We are asked regularly about our puzzles. A visitor wanted more information about the SOMA Cube.

The puzzle you describe is called the Soma Cube. It was invented by Piet Hein, a very interesting mathematician. This Wikipedia entry scratches the surface.

We see many very reasonably priced versions of the cube on Ebay.

Once you have one, be sure you don't limit its use to making cubes, here is a link that leads to many Soma Cube puzzles.

It has been said that a person who works intensively with the pieces for two weeks won't need the blocks any more to solve puzzles. That we would like to see!

Impressions of Oppenheimer

How do Americans think about J. Robert Oppenheimer today? How do people in Los Alamos think about him?

My personal impression is that most Americans who know about him hold him in awe. I think most see him as a brilliant scientist. Fewer are aware that he served the country as an amazing administrator who came to Los Alamos on E. O. Lawrence's recommendation without a big reputation or even much experience managing. I think people who now think the atomic bombs should not have been used might feel ambivalent about Oppenheimer, but many of them still respect his scientific abilities. People also see him as a tragic victim of McCarthyism, if they know that story.

In Los Alamos he is revered. Some older people here remember him, and he enjoyed the respect and personal affection of many people at the laboratory in his day and in his later years. There are strong feelings about the security hearings, and most people here see the outcome as terribly unjust and even cruel. I don't think anyone here believes Robert Oppenheimer was ever a security threat.

If he didn't oppose it, Oppenheimer was not enthusiastic about the hydrogen bomb. He probably dragged his feet. Edward Teller was a proponent, impatient with Oppenheimer's views, a founder of Lawrence Livermore National Lab, and testified against Oppenheimer. Although he was a pretty colorful character, Teller is not fondly remembered here.  As is true with so many aspects of our history, this is a very complicated topic. To what extent Oppenheimer's communist connections played a role, vs. power struggles within the physics community and even in Congress and the military, as well as other factors that were involved, historians will never untangle the security hearings.

As to why the museum is named for Oppenheimer's successor, I will suggest two reasons.

Oppenheimer's name is all around Los Alamos. An award, a lecture series, a street, and several buildings all pay tribute to him. (Wouldn't you expect the Oppenheimer Science Museum to be found in the Oppenheimer Center?)

Norris Bradbury is credited with keeping Los Alamos Scientific (later National) Laboratory alive at a time when it is very possible the US government might have closed it. Many scientists, including Oppie, left shortly after the war to return to their university roles. Bradbury was director for 25 years, an extraordinary tenure, and was director when the original version of this museum opened. Bradbury as a person is also very fondly remembered by those who knew him. 

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. . .


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

Cross PuzzleYou 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.

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.

Nano Jump-To-The-Moon

Our nano jump to the moon was based on these calculations:

The Moon is about 250,000 miles away (A quarter of a million miles.) A mile has 5280 feet in it. A foot is made of twelve inches. At this point, if we multiply all these numbers together, we will discover that the distance to the moon is (approximately) 15,840,000,000 inches from Earth. One billionth of that would be 15.84 inches or about 15 13/16 inches on a yardstick.

To make this “high” jump, I used PVC pipe, probably 3/4” but it doesn’t really matter, I cut two lengths 15 3/4” long, my cross bar is a piece of 1/16” fiberglass rod about a foot long, and the bases are crossed pieces of 2 X 2 lumber a couple of inches long. I got the rod from McMaster-Carr, my very favorite materials catalog (Google it), but any similar material will work, I wanted to make sure that there was no possibility it would trip or catch a child, and that it wouldn’t break easily or hurt them if someone fell on it. (and I had some lying around.)

I am particularly proud of having thought of marking off 3/4” ticks across the bar, putting it in my drill on low speed, and using a red Sharpie to make the stripes!

I hope this helps you, it has been a popular part of our program.

Online Card Trick Spoiler

Regarding a cute online card trick: http://www.quizyourprofile.com/guessyournumber.swf

This is wonderful! Thank you Mary Ellen for showing it to me. I DO know how it works but it is so well executed that I am almost reluctant to explain it. If you want it to stay mysterious, leave this entry now!

The trick is that they have added great red herrings, where you pick the color or the crystal ball or the door while you say your number a couple of times in you mind. This has nothing to do with the trick. The trick is like the classic twenty-one cards in three rows of seven trick. We start here with twenty-five numbers, and the program asks us which of five colors it is. This narrows us down to only five numbers. Then it distracts us while we choose a color which has nothing to do with the trick. Next it asks us which house our number is in, with six numbers in each of five houses.

Remember the first question? Well each house has exactly one number from each of the original color groups (Plus five extras added for smoke-screen.) They are all colored alike in the houses, further concealing the process. Giving this information tells the program which of the first five numbers we chose, and for all intents and purposes the trick has been executed. The rest is just distraction. Any door you open at the end will have your number.

What I find fascinating is that the computer can take advantage of my mind thinking of the numbers as physical entities as if they were printed on cards. For example, I can see my brain thinking, as I pick a door, that only one door can have “18” behind it.  The number on the screen, however, is an imaginary electronic construct with no physical reality, in fact it doesn’t even exist until the door opens, so my wonder that the number actually is “18” is my own darned fault. Schrodinger would be proud!

One other thing is that unlike a carbon and water based magician, who might struggle to remember in the first stage which five numbers are red, which are purple, etc. this is the easiest thing to accomplish for a computer program. One could construct a set of cards that would do the manipulations mechanically, but it would be nowhere near as invisible as the computer program.

Durable Hand Generators

We build hand generators from DC gear motors which we find on surplus electronics websites.  Look for DC gear motors and order a small selection of different ones to test. These are surplus and always change, so if you find one that you really like, buy a bunch. While you are at the electronics store you may want to pick up a pair of large alligator clips and about 18 inches of lamp cord (Two strand wire) per generator.

We get our crank handles from Reid Supply, 3.5” aluminum cranks, the part number is something like CH-35AL (pretty obvious how they coded that!) These don’t have holes in them so they fit any motor shaft size.

We drill a blind hole (not all the way through) in the handle and fasten it to the motor shaft with epoxy. If we can, we open the motor case and solder the heavier cord directly to the connectors. If we can’t, we will solder the wires together, either way we provide some form of strain relief. we have glued the motors into PVC pipe with the cord knotted and passing through an end cap. Sometimes we have to grind off a metal flange to make a motor more hand-friendly. The alligator clips are soldered to the ends of the wire. We try to keep the wires and the colors of the clips polarized the same way so that saying, “Let’s try connecting all the red clips together” almost has a predictable result. (It depends which way the student turns the crank.)

These generators last a long time, we don’t ever strip the gears in them, and the cost of parts is less than $20. The epoxy joint is typically the failure point and very easily repaired.

We use our generators mostly to turn other generators. Students love it. We have been tempted to make some winches, with pulleys instead of cranks to see if we can lift stuff, and if we can turn the generator with falling weight. Two pulleys on the shaft; a big one and a small one? We have seen a similar device used to split water with electrolysis to make little hydrogen-oxygen explosions. Cool!

How Do Eyes Work?

Eyes are very complicated. They have a lot of different parts, and all of the parts are important. You might have to explain this to a grown-up so they can understand how eyes work.

Let's start with light. Light bounces off things and some of it goes through the pupils in our eyes. Those are the little black circles. 

Then it passes through a lens which bends it and focuses the light on our retina, which is a thin tissue at the back of the eye. Focusing means that light from one part of what we are looking at goes to one place on the retina.

Just like the rest of your body, the retina is made up of tiny cells.

These are too little to see without a microscope. The cells in your retina are special because they make chemicals called dyes. When light hits the dyes, the dyes get bleached out, the chemicals break down. You can see this effect with colored construction paper if you put a piece in a sunny window  and cover part of it with something light doesn't go through. After several days or a week, you will see the sunny part has faded. Your eye cells work MUCH faster. Your cells keep track of the dyes, and as they replace the worn out ones, they send a message to your brain about the light that has hit them.

Your brain puts together all the information it gets from all the cells in your retina to figure out what you are seeing. It is a truly amazing process.

Carbon Dioxide Sequestration Concern

When CO2 is stored underground, it includes oxygen atoms. What is the impact of taking all that oxygen out of the atmosphere?

I am not expert in this field, but I have two thoughts on the matter. First, there is much more oxygen in the atmosphere than carbon dioxide. The amount of CO2 that needs to be removed from the environment, while it may be an enormous amount of substance, actually represents a small fraction of a percent of the atmosphere. Meanwhile, the atmosphere is about 20% oxygen, so that sequestering that CO2 will have much less effect on the proportion of oxygen than it will on the amount of carbon dioxide.

Second, the oxygen in that CO2 is already bonded in the molecules, so it is not oxygen we can breathe anyway. We can't and we wouldn't ever want to eliminate all the CO2 in the atmosphere. That would bring on other disasters such as the stopping of photosynthesis. The object of carbon sequestration is to try to balance CO2 levels against our consumption of fossil fuels. If there is a threat from the loss of oxygen in the atmosphere, (I don't think there is.) the culprit is the combustion of fuel for our energy.

Atomic Theory History Question

Did the Greeks discover atoms?

Democritus lived about two hundred years before Aristotle and Plato, and is often credited with originating the concept of the atom. He was a philosopher, and his idea was to try to explain why different materials had different properties, such as why are liquids flexible and solids less flexible. We know now that the atoms, for example in ice, water, and steam are all made of the same kinds of atoms. Many Greeks of the time thought that the highest form of research was thinking about things, because the mind and ideas are superior to the world and the senses, or something like that. The word "atom" means invisible, and in that sense, the Greeks were sort of correct. I would argue they really had no idea what atoms really are.

John Dalton, in the early 1800's, more than 2,000 years after Aristotle, formulated the first modern version of atomic theory, and by then he had enough scientific data to actually do a pretty good job of describing an atom as we now understand it. Still, there was no direct evidence to prove the existence of atoms, and Dalton's atomic model was primitive by modern standards.

It wasn't until 1905 that Albert Einstein published a paper that actually proved the atomic theory, and even since then, the model of the atom has been corrected and improved many times. Murray Gell-Mann, a physicist who lives in Santa Fe, won the Nobel Prize in Physics for his research into the inner structure of protons and neutrons.