Muon

Muons in the Cathedral The first ten seconds give you some context, so pay attention.
Some science dudes think they have found a secret chamber in the big pyramid. They claim they used a muon detector. Muons? I haven't heard anything about muons in a long time. I just barely recognize the word as a name for some kind of sub-atomic particle.

There is something wrong with Muons. On one hand they weigh (mass) 207 times as much as an electron, but when they decay all you get is an electron and two virtually massless neutrinos. What happens to all the extra mass? Does it get turned into energy? We aren't talking about very much mass here. . . pause while we figure out just how much a muon masses.

First we find that the muon mass is:

105.6583745(24) MeV/c²

MeV/c is a no unit of mass I've ever hear of, but following the link takes us to a conversion formula that translates it into atomic mass units (u). 

1 u = 931.4941 MeV/c²

So we're dealing with something like one-ninth (105 / 931) of one atomic mass unit. If all that gets turned into energy, how much is it?

Well, Wikipedia's Elevtronvolt page translates electronvolts to joules, so we don't have to do the energy to mass to energy conversion. We go straight from one form of energy to another:

1 Electron Volt = 1.6021766208(98)×10⁻¹⁹ Joules

Call it 1.6 x 10^19. So:

1 Me (million electron volts) = 1.6×10⁻¹³ Joules

And the mass of a muon is worth

 106 x 1.6×10⁻¹³ = 170×10⁻¹³ Joules

1 Joule is equal to 1 Watt-Second.

A square kilometer contains one million square meters. 10,000 muons impact every square meter every second. In one second, ten billion muons will impact our square kilometer of land. In a day we'll have 86.4 trillion muons, which is 86.4 x 10^12. So in one day all those muons will generate one-twentieth of a Joule, or about one Watt for 5 milliseconds. Might be enough to make an LED flash. Guess we don't need to worry.

When I started searching for information about muons, I found a couple of people who claimed to have built muon detectors for cheap, but they didn't actually tell you how they are made. The muon detectors used in the video above, and in the pyramids don't just detect the muons, they also tell you what direction they are coming from. You could do that with home made detectors, if you could find out how to make them. They would just need to be very small and you would need a bunch of them.

Science Versus Space Exploration

There was a story in the paper today about how a local company moved a giant freaking magnet from Long Island, New York, to Chicago and all the contortions they had to go through to make the move. My first question was why the heck didn't they build the darn thing in Chicago in the first place and save everyone involved a lot of grief. Well, they probably had good reasons for that, and since a local company got the contract for moving it I suppose I shouldn't complain too loudly. But then I start thinking about how much money we are pouring into all these crazy high energy physics experiments, all designed to try and figure out how the universe works, and we are just sitting here on our little ball of rock. We should be out there exploring the galaxy, especially since I have figured out how to do it for not much more than annual GDP of lower Elbonia. (See list at end of this post.)
    The big trick is that if you could build a space craft that could accelerate continuously at one gravity you could be anywhere in the galaxy in a couple of years. One year of accelerating at one gee would bring you pert near the speed of light, and while your velocity measured relative to Earth might not increase much after that, you and and everyone else aboard the ship would start to experience extreme time dilation, i.e. time would slow down for you, so you would need to keep a sharp eye on your clock in order to determine when to start slowing down so you don't miss your destination. One minute at the speed of light with a time dilation factor of 10 will take you 600 billion feet, or a little more than one AU (astronomical unit, the distance from the Earth to the Sun, about 93 million miles or eight light minutes).*
    So how do you build a spaceship that can accelerate continuously at one gee? The trick is you need a very high exhaust velocity, and for that nothing beats a linear accelerator, the big old monsters physicists are using to explore subatomic particles. Feed it a steady diet of iron particles for magnetic reaction mass and power it with a nuclear power plant from a submarine and off you go.

*Rough calculations:

• Light travels 186,000 miles per second. Let us round that up to 200,000 miles per second to make things easy on ourselves.
• Multiple by 60 seconds per minute and we get 12 million miles per minute.
• Multiple by 10 for our arbitrary time dilation factor and we get 120 million miles, which is a little more than the distance from the Earth to the Sun.

How to get started in space exploration, in five easy lessons:

• Rocket to the Moon 
• Rocket to the Moon, Part II 
• Space Habitat
• Moon Base Power 
• Moon Base Launcher

"Dark Lightning"?

I'd never hear of this before:

Unknown to [Benjamin] Franklin but now clear to a growing roster of lightning researchers and astronomers is that along with bright thunderbolts, thunderstorms unleash sprays of X-rays and even intense bursts of gamma rays, a form of radiation normally associated with such cosmic spectacles as collapsing stars. The radiation in these invisible blasts can carry a million times as much energy as the radiation in visible lightning, but that energy dissipates quickly in all directions rather than remaining in a stiletto-like lightning bolt. ... Unlike with regular lightning, though, people struck by dark lightning, most likely while flying in an airplane, would not get hurt. But according to [lightning researcher Joseph] Dwyer’s calculations, they might receive in an instant the maximum safe lifetime dose of ionizing radiation — the kind that wreaks the most havoc on the human body.

By "not get hurt", I imagine the reporter means that a person struck by dark lightning would not be crispy crittered. Yet getting a lifetime's dose (or more) of ionizing radiation does not seem like a good thing. Maybe better than the alternative.

Stolen entire from E.B. Misfit, except I added the picture.

Fallout

I like this. It is a coherent, graphic representation of a over 50 years of atom bomb testing. The following note is found at the end of the video. I'm including it here because I knew I read something about a book, but I couldn't remember where I read it. I probably spent the better part of an hour looking for it before I realized it might be in the film itself.

The film was made based mostly on the data of
"Nuclear Explosions 1945-1998" by Nils-Olov Bergvist and Ragnhild Ferm
copublished by the Swedish Defence Research Establishment (FOI)
and the Stockholm International Peace Research Institute (PIORI)
in 2000. 

Isao Hashimoto 2003

The video shows the tests conducted by six countries:

• United States of America
• Soviet Union
• Great Britain
• France
• India
• Pakistan

The USA did over half of all tests. I was surprised by the number the French did.

North Korea is not included because the video stops at 1998, and North Korea's tests happened later. South Africa had a atom bomb program, but they gave it up. Israel might have an atom bomb program, but nobody who knows is telling. Same with Iran.

I remember learning about radioactive fallout from nuclear weapons when I was in elementary school. This was back in the days when people were actually building bomb shelters. I didn't think too much about it at the time. Atom bombs were very bad, but the adults seemed to have things all figured out, and besides, there wasn't anything I could do about it, so I soon stopped thinking about it. As time went by I heard less and less about it. Oh, every so often you would hear someone ranting about radiation poisoning the environment for the next zillion years. In general we seem to have a more rational view of the situation now. I had a hard time finding any information about radiation from old atom bomb tests. I finally found this bit on the World Nuclear Association website. I have no idea who they are, but their explanation seems to be coherent enough.

Routine sources of radiation 

    Radiation can arise from human activities or from natural sources. Most radiation exposure is from natural sources. These include: radioactivity in rocks and soil of the Earth's crust; radon, a radioactive gas given out by many volcanic rocks and uranium ore; and cosmic radiation. The human environment has always been radioactive and accounts for up to 85% of the annual human radiation dose.
    Radiation arising from human activities typically accounts for up to 15% of the public's exposure every year. This radiation is no different from natural radiation except that it can be controlled. X-rays and other medical procedures account for most exposure from this quarter. Less than 1% of exposure is due to the fallout from past testing of nuclear weapons or the generation of electricity in nuclear, as well as coal and geothermal, power plants.

Thrust

I've been thinking about how to build a starship, and I'm thinking a linear accelerator sending iron particles out the back might be a viable method for obtaining a decent amount of thrust over a long period of time. I don't know how long it would need to be. SLAC (Stanford Linear Accelerator Center) is about two miles long and they get things going pretty quick. Of course, they are only accelerating sub-atomic particles, stuff with no appreciable mass. I suppose it depends on how strong your magnets are and how much electric power you can generate to power them. One advantage we would have is we are already operating in a darn near perfect vacuum, so we aren't going to need a sealed tube to keep the air out, or vacuum pumps to remove it. Matter of fact I think all we really need is a spiral of wire. At the front end the loops of the spiral would be very close together. As we move down the accelerator toward the aft end, the loops would get farther apart corresponding to the increasing velocity of our reaction mass. At the end, our wire would be pretty near straight, making one loop around the path of our stream of iron every couple of feet or so. We would launch a particle of iron down the center of this spiral and pump a jolt of electricity to the spiral itself. The power would flow down our accelerator at the same velocity as the iron. At the beginning, the particle's velocity would be low, but the current would be following the wire around and around the iron's path. The magnetic field produced by the current in the wire would propel the iron particle along it's path. As the loops in the spiral spread out, so would the velocity of the particle increase.

We would need some kind of framework to hold the wire in position, and absorb the reaction from the magnetic field pushing on the iron. Being as our accelerator might be fairly long (one mile? ten miles?) it would also need to be rigid enough to hold its shape. This could lead to it being fairly massive. Since we are going to be running this thing for several years, we are going to be sending a sizable amount of reaction mass out the back. Perhaps thousands or even millions of tons of iron. As we consume our reaction mass, our rate of acceleration will increase. In the later part of our journey we would not need as much thrust as in the beginning. Perhaps what we could do is build a bundle of these linear accelerators, perhaps a dozen, perhaps a hundred, perhaps more. We take off with all of them running. After the first fraction of our journey, we shut off one accelerator and start taking it apart. As we take it apart, we grind it up and use it as reaction mass for the remaining engines/accelerators. This way we maintain a relatively constant mass to thrust ratio, and if our thrust is high enough, a relatively comfortable environment for our crew.

Cosmic Pollution

    We are getting pretty good at sending probes to other planets. Voyager, Cassiopia, and now Curiosity, have shown we can build complex devices, launch them into space, have them survive for long periods of time and  function reliably.

   Sending a probe to another star is another matter.  The main problem is having a rocket engine that can provide thrust for a long period of time. Today's rocket engines burn out in a matter of minutes, or even seconds. They are designed to generate large amounts of thrust for short periods of time, which is necessary to get out of Earth's gravity well. But once you are in orbit, that is no longer a requirement.
    In order to to provide thrust for a long period of time, you need to meter out the mass you are expelling as a propellant, and in order to get any appreciable acceleration out of such a small amount of mass you need a very high exhaust velocity. Rockets are very impressive: they make a great big roar and shoot out huge flames and clouds of smoke, but their exhaust velocity, in cosmic terms, is pitiful. What we need is something that can accelerate matter to very high velocities. What we need is a particle accelerator. I mean they accelerate particles to pert near the speed of light. You really couldn't ask for anything faster. Of course they are big, cumbersome, heavy and have some kind of unknowable power requirements, but if we are operating in space and on a scale of years, I think we could manage.
    One of the draw backs of particle accelerators is that they only accelerate sub-atomic particles, in particular protons and/or electrons, because the magnets they use only act on charged particles. So you would have to be making a continuous supply of charged particles to feed them. And if you making protons (from hydrogen, say) where do all the electrons go? Wouldn't they leak out, and be drawn to the protons so they could recombine to make hydrogen? And what would that to your carefully created thrust? Hmmm.
    Then I had another thought. There are basically two kinds of cosmic rays: various sub-atomic particles, and very high velocity iron particles. Wait a minute! Iron is magnetic. Couldn't we feed our particle accelerator iron particles? Iron is heavy. We could generate a boat load of thrust from hardly any mass, providing we can get it going fast enough, and in a vacuum with enough electromagnets, we should be able to do that. Granted our linear accelerator might need to be really long. The ones here on Earth are sometimes miles in length, and they are only accelerating tiny bits of stuff. Building one to use for propulsion might need to be, I dunno, ten miles long?
    We have all the science we need to do this. We know how to build nuclear reactors that generate electricity, we know how to build linear accelerators, we know how to make little particles of iron, we know how to build really big things (like bridges and damns) and we know how to put stuff in orbit. All we need is the determination.
    As a bonus, I've figured out we aren't alone. All those cosmic rays I was talking about earlier? The ultra-high velocity iron particles? They are the exhaust from alien intersteller space craft!

HESS II

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Satellite view of the HESS II installation.
Namibia is in the news for the 2nd day in a row, at least on the Graham Hancock website. Yesterday there were rumors of a vast underground reservoir of water. All it takes is one look at the place to know that would be wonderful if it pans out. I don't think I've ever seen any place quite so desolate looking, except places known to be deserts, like the Sahara or the American Southwest. Not too long ago there was a story about "fairy circles" in Namibia, which are probably due to a fungus of some sort. Today's news is about HESS II, another crazy astronomy project, similar to the one in the Chilean desert in South America in that they both chose a location because of it's high elevation and low moisture content. Crazy, man.

HESS is being used to detect high energy particles, i.e. cosmic rays. It does this indirectly by detecting the blue light (Cherenkov light) generated when a cosmic ray impacts a molecule high up in the atmosphere. The HESS website has a better explanation.

Micrograph for the Day

Cosmic ray tracks in an Apollo space helment, amplified 10-millionfold by chemical etching.

I don't remember when I first saw this picture, but I told Jack about it at lunch today. I looked for it when I got home and was surprised how quickly I found it.

From the Wikipedia article on Ultra-high energy cosmic rays:

. . . in other words, a subatomic particle with macroscopic kinetic energy equal to that of a baseball (142 g or 5 ounces) traveling at 96 km/h (60 mph).
It was most probably a proton with a speed very close to the speed of light.

At some point I had the idea that cosmic rays were iron particles, and that might occasionally be the case, but they are more likely to be protons.

So I'm wondering if the astronaut noticed when this particle hit his helmet. Maybe it wasn't an ultra-high energy cosmic ray, maybe it was just regular cosmic ray, and he just thought someone was throwing spitballs at him. Jimmy! Stop that!

Update January 2017 replaced missing picture.

Space Habitat

Baring a breakthrough in physics, sending human beings anywhere in space beyond the moon is going to take a very long time. Even a trip to mars will take a year just to get there. Given this situation I think it would be a good idea if we got started with building a space habitat where we could learn how to live in space, not just survive. All the ideas I have seen about building a ship to go to Mars all look like they come from cheapskates. The bare minimum of equipment, the bare minimum of shielding, just enough that the crew, if they are lucky, will survive. It looks like a recipe for disaster. We should take a page from the Victorians and building something that could survive most anything the universe can dish out. Building a habitat at Lagrange point L4 (never mind L5, everyone else has already talked L5 to death) would give us a chance to see what it is really like to operate in space.

Lagrange Point Habitat

I am thinking we would want a sphere about one mile in diameter. Spin it at a rate of one revolution per minute and you would have one gravity of acceleration at the largest radius. I like the idea of making the surface of the sphere out of foot thick steel, but this may not be the right choice. The skin of the sphere will have several functions:

• Keep air and water vapor inside
• Keep dangerous radiation outside
• Absorb and/or deflect meteors and other debris
• Hold itself together, i.e. have some structural integrity

To do all this may require several layers of various materials and in fact may be a hundred feet thick and honeycombed with access passages. One thing to remember is that we probably are not going to want much on the outside of the skin near the equator. The skin at the equator will be traveling at about 200 miles per hour. Anything that is attached there that loses its grip is going to leave very quickly.

A large diameter cylinder would be fitted to the inside of the sphere and concentric with axis of spin. It would take up one third to one half of its' length. This would give us a large surface of even gravity on which which to house our people. A cylinder a third of a mile long and one mile in diameter would give us about one square mile of "land": 640 acres. We should be able to do something with this, perhaps farm, or even raise cows. The area between the cylinder and the skin of the sphere could be used for water tanks. In case of a breech of the hull, large valves could be opened into these tanks and quickly drain any surface water into the tanks before it all evaporated into space. Water in these tanks could also be transferred around the diameter of the sphere to compensate for any imbalance.

The large diameter offers several advantages:

• Low gravity gradient. There would little difference in the apparent force of "gravity" as you changed elevation. For instance there would a negligible difference between your head and your feet, and the difference would still be small for an elevation change of 100 feet.
• Slow spin rate. I would hope that an angular velocity of one revolution per minute would minimize any problems with vertigo either for permanent residents or visitors. As far as I know there is no way to tell. Research and testing will be necessary.
• High linear velocity. The high linear speed of 200 MPH means that any motion in the vessel, like walking, will have a minimal effect on your perceived weight. Running, either with or against the rotation, will no doubt have a noticeable effect, though it should be something most people should be able to deal with.
• Wide open spaces. Having a "ceiling" a thousand feet in the air would give people a feeling of wide open spaces like they have on the Earth's surface. It might help prevent attacks of agoraphobia in people returning to Earth, and attacks of claustrophobia in people arriving at the habitat.
• Large volume of air. This means that we can survive small leaks until they are found and a small amount of anything unpleasant or noxious would be diluted to the point where it is harmless.

A smaller diameter cylinder would also be fitted into the sphere, also concentric with axis of spin. This cylinder would be much smaller in diameter, perhaps a couple of hundred feet. This cylinder would be used for docking of cargo and passenger vehicles. This ends of the cylinder would be doors. Since the entire cylinder would be exposed to vacuum, the surface of this cylinder would need to have many of the same attribute as the surface of the sphere. The doors at the end of the cylinder would span perhaps a quarter of the diameter of the cylinder. Vessel docking would be accomplished by:

• contact with a long probe which would stabilise the vessel's position and relative velocity.
• with the aid of the probe the vessel would be maneuvered into position directly outside the sphere and in-line with its' axis of rotation
• a cage-like frame would close about the vessel and be secured
• the cage would be drawn into the sphere
• the cage, and the contained vessel, would be spun up to match the sphere's rotation
• the cage would be moved sideways, relative to the axis to a docking berth

We could have two kinds of berths. One would just hold the cage, and could provide an airlock for crew and passengers. The other could be enclosed so that it could be pressurized. A vessel a mile in diameter can expect to have a fair amount of traffic coming and going. Having this central cylinder devoted to docking would allow incoming vessels to enter at one end, be docked along the walls, and exit through the other end. A continuous stream of traffic could beaccommodated this way.

In most cases docking could be carried out in vacuum, but there will be cases where bringing the vessel into a pressurized chamber would make things easier. Emergency would be one case, and external repairs would be another. It is easier to build and seal a small door rather than a large door. If vessels where constructed as long cylinders, then they could enter a pressurized chamber through a relatively small door. So pressurized docking chambers would be cylinders perhaps three times the diameter of a vessel and slightly longer.

We would probably not need to accommodate winged vessels like the space shuttle. We would be a long ways from anyplace where wings would be useful. The expense of boosting them this far out would be very hard to justify. However, if this structure is going to be a mile in diameter, just how big are the ships going to be? Right now I find it difficult to imagine anything larger than about 30 feet, but I have seen numerous engineering projects that had to be revised to accommodate the bigger, larger and more powerful.

At one point I was thinking that sand would be the perfect material to use for shielding the outer skin of the sphere. Easy to transfer, simply pour from one container to another. Good for absorbing impacts from micrometeorites and cosmic rays. And it could be used as a raw material. Apply enough heat and you get oxygen and silicon. Oxygen is always handy for air breathing mammals. Problem is any small holes in the "underside" of the containing vessel would let the sand drain out and be lost. There are ways to compensate, like putting a chamber below the sand to catch any that leaks out, and allow maintenance to plug whatever holes show up in the floor of the sand chamber.