Monday, March 2, 2015

Does the Universe have an edge?

I don't think anyone really knows. There are lots of ideas, though. If there has only been one Big Bang (which in itself seems unlikely to me), then the Universe has an average radius, approximately the age of the universe times the speed of light, ignoring the possibility of stuff that travels faster than the speed of light. Intergalactic space is thought to have an average density of something like 1 hydrogen atom per cubic meter [citation needed] although recent news from the big telescopes suggests that there are stars and planets also outside of galaxies. 1 atom/m^3 is pretty empty.  If the universe is alone, I suspect there is no way we will ever see its edge, as it is receding from us at or faster than the speed of light.

There are cosmologists who believe in all seriousness that our universe is expanding like a bubble in a foam of universes, in which case it is possible, I suspect, that we will some day detect the boundary, where it impinges on another universe. Does the edge slow down? Is there a shock wave? Please forgive me for being so Newtonian about this, but I can't imagine a foam of universes where all of them can expand indefinitely at or above the speed of light. Not, at least if they all share the same dimensions*. Then the question begs to be asked, does the foam have a boundary? What would be beyond that?

"It's turtles all the way down."

*What if our three familiar dimensions are actually dimensions #38576027184365756392,  #38576027184365756393, and #38576027184365756394, and other universes are also three dimensional but occupy other dimensions than our particular three of length, width, and height? (I am ignoring the 9, 11, 17 or whatever dimensions are required by string theory.)

How many moons are there in space?

Space is a really big place. There are billions of galaxies and each one has billions of stars. Recent discoveries suggest that planetary systems are the rule and not the exception around stars. So the number of moons in space is uncountable.

I suspect you meant to ask how many moons there are in our solar system. When I was young, a long time ago, books about the solar system gave precise numbers for the moons of each planet. Then came the Pioneer and Voyager spacecraft and vastly better telescopes. The answer is no one knows. It seems every time we a get closer look at the distant planets, like Saturn, Uranus, or Neptune, we discover they have more moons than we previously thought. Even Pluto is now known to have at least two moons.

This Friday (March 6, 2015) the dwarf planet Ceres, the largest body in the Asteroid Belt, will get a new moon, or at least a satellite. NASA’s Dawn spacecraft will slip into orbit around this body for a visit.

Why is there so little information about the Navajo Code Talkers here?

Jourdan, I am so proud of you! Thank you for asking why we don't feature the Navajo Code Talkers at our museum. You are the first person to ask this in my ten years as the question answerer, and it is a good question. 

You are correct that we feature mostly Manhattan Project related information in our history exhibits, and that is actually the short answer. You might like to know that we occasionally get criticized for not talking more about the Holocaust in our museum. I am fascinated that while we seem to brag about "ending the war," very few people if any suggest we could talk more about the aspects that actually won the war, the Navajo Code Talkers being a major contribution along with, for example, shipbuilding and the secret developments of radar and code breaking.

WWII, particularly in the Pacific, was a truly horrible affair. I cannot imagine the feelings of the Marines who bore the brunt of one amphibious assault after another against entrenched and fanatical fighters. They were extremely lucky to have the Code Talkers with them, and the ability to communicate securely because the Navajo People, Your People, had protected and maintained their ability to speak in their own tongue, often in the face of harsh government opposition.

I will place a copy of this text in our answer book. It is not much, and nowhere near what they deserve, but the Navajo Code Talkers earned at least this little honor.

Monday, January 26, 2015

Why did Fat Man have dark paint markings?

You asked a terrific question about the black paint on Fat Man's protruding parts. Fat Man was delivered to Tinian Island in parts and assembled on the island. The implosion design had been tested in New Mexico, but had never been exposed to the kind of humidity it experienced in the Pacific. After assembly, but before loading it onto the bomber Bock's Car,  all of Fat man's seams were sprayed with a sealer. I think it was asphaltum or something similar. Many of the protruding parts were bolted on, so their seams were included in the treatment.

Was Flouride a by-product of the Manhattan Project?

 I love this question which I found this morning in our question box. So much in fact that I just had to share it with a Lab chemist I know. (Because I had no idea.) I have copied his response in full here. I recommend both of the links. Thank you for providing me with this opportunity to learn!

"I’m guessing that they are referring to the de-conversion of uranium hexafluoride to form uranium metal.  A byproduct of the de-conversion process would be fluorine – typically as a fluoride.

Here is a NRC web page providing some information on uranium de-conversion:

Also web page for the company that is building a facility in southern New Mexico for uranium de-conversion:

For example the above facility apparently plans to produce the SiF4 (silicon hexafluoride) as the byproduct instead of a fluoride salt.  As mentioned SiF4 is typically used to make high purity silicon for electronic applications.

With regard to Manhattan Project I’m not sure where the de-conversion process took place and what form, e.g. fluoride salt, they produced at the time."

Are the Little Boy and Fat Man models at the BSM full scale?

Our replicas are full scale. Actually around 2005 ago we replaced our original models with two even better replicas that are more accurate in representing the appearances of the two weapons.  The two new versions, constructed of steel and fiber glass are actually ballasted with concrete to represent the actual weights of the original weapons. Not that we ever heft them.

Thursday, May 1, 2014

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. has basic information about the ozone layer, and has an up-to-date ozone weather map.