Monday, September 9, 2013

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.

Some of my favorite questions are those I can answer, "I don't know."

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.

SOMA Cube

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.

Thursday, March 21, 2013

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. . .

Monday, May 14, 2012

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.