Posts Tagged ‘physics’

Celestia

Posted: 1 December 2007 in Uncategorized
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When I was around 12 or 13, I first got a hold of my stepfather’s physics text book. It was magic. The rules that governed the physical world were right there in the form of equations on a page. I was totally captivated. Newton’s laws of motion, gravity, angular momentum, and the theory of relativity. When I first learned about relativistic time dilation, it was life-changing. I resolved to become an astrophysicist. A lot of changes happened in my life that turned that dream into my current one. But, like all first loves, it never went away.

When I got my first computer, I had hopes of writing a program that would plot the positions of the stars as they were in space (3-D) versus how they appeared in the Earth’s sky (2-D). I achieved a little bit of success getting the vectors worked out from the distance, right ascension, declination and so on. I had no easy way of visualizing it though. Doing 3-D plots in BASIC back in 1990 wasn’t the easiest thing in the world. So that project died.

Then like a ghost, Celestia came to me last night. Wrapped up in her open source glory, I dared not even dream that she could perform what I had so long abandoned all hope of. But she did my friend, she did. (My wife won’t like this imagery :))

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The Grand Unified Theory (GUT) has been sought after for years. Einstein died pursuing it. Many great minds have tried to tackle it and complicated theories and first steps abound. There are four forces in our universe: the electromagnetic force, the strong nuclear force, the weak nuclear force, and gravity. The Standard Model unifies the first three. The problem has been unifying these with gravity. String theory was proposed to account for gravity but so far it has been completely untestable. This, of course, invalidates it as a scientific theory. It has remained compelling to many physicists, though, in hopes of one day being able to test it. The goal of a GUT (or a theory of everything) is to reduce all of these forces to a standard set of equations.

At the moment, we have two theories which account for everything and no way to bring them together. The Standard Model and Einstein’s General relativitiy. Enter Garrett Lisi. He got his PhD from UC San Diego in 1999 and has since been unaffiliated with an academic department. He surfs and snowboards and basically goes around not knowing where he is going to stay next month or how he will pay for it.

E8 root system for Garrett Lisi’s theory of everythingE8 (right) is the key. It is a complicated mathematical construct that I don’t really understand from my glance at the wikipedia entry. As is typical in higher math, you have to understand 20 other things first and I’ve never even heard of Lie algebras. However, the layman’s breakdown is that it is an 8-dimensional pattern that encapsulates the symmetries of a 57-dimensional object which itself has 248 dimensions [source]. Make sense? Anyhow, apparently this thing was only well understood this year, despite being discovered over a hundred years ago.

So Garrett Lisi recognized that each of the 248 points in E8 correspond to the various elementary particles and forces in our universe. This left 20 points that had to be filled in with theoretical particles. So now all Garrett has to do is develop a set of experiments to test his theory. The Large Hadron Collider will go online next year and if string theory is correct, probably end the world. However, if Garrett is correct, we’ll all be alive in 2009.

Crayon Physics

Posted: 14 November 2007 in Uncategorized
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I stumbled on this the other day. The game is called Crayon Physics and it’s pretty much what it sounds like. You can make a crayon drawing of simple shapes like squares and circles and curves. The objects you create begin obeying the laws of physics (gravity and Newton’s laws of motion mainly). So a square drawn in the air falls to the ground. A circle drawn on a slope begins to roll. The first version is pretty simple. On each level you have to move the ball to the star. You can drop things on the ball to get it to roll, you can set up obstacles, build bridges, etc. It’s ingenious.

The next version will hopefully roll out soon. No telling though since it’s a guy working in his spare time. But looks to be excruciatingly cool.  Watch me play one level while trying to record it on my cell phone.

Venutian Rover Bomb

Posted: 12 November 2007 in Uncategorized
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There is a cool article today in New Scientist that describes an old cooling method with a bleeding edge application: a rover to Venus. Venus is a picture of the greenhouse effect gone wild. Average temperatures are about +260 degrees Celsius (500 degrees Fahrenheit). This is hot enough to melt lead and destroys most modern electronics. Previous rover attempts to Venus by the US and Russia lasted less than 2 hours. So if we are to put a rover on Venus for the kind of time we have spent on Mars, we’ll need to find a way to cool the onboard electronics long enough that they can operate well.

Enter two NASA boffins, Geofferey Landis and Kenneth Mellott. By applying a refrigeration technique invented by a clergyman nearly two centuries ago, they have found a way to keep a rover cool for about fifty Earth days (a Venutian day is 243 Earth days, about 19 days longer than its year!). The Stirling cooler (invented by Reverend Robert Stirling) works by compressing a gas with a piston. As it compresses, it gets hotter. The temperature is dissipated with a radiator (which would be placed on the back of the probe). As the gas expands, it gets cooler (causing the refrigeration effect). In order for this to work, the radiator must be hotter than the outside air.

Interestingly, the Stirling cooler is energy efficient and is being incorporated into some of the newer energy efficient refrigerator models. To power the cooler on the rover, they propose using a plutonium battery. This type of device is known as a radioisotope thermoelectric generator. As the radioactive material decays, it release heat, and this heat is converted into electricity. These batteries are common on satellites and in unmanned situations where a long duration power source is necessary and solar cells are not viable (the massive cloud cover on Venus prevents solar cells from being very effective, plus the atmosphere is very caustic and I think it would probably damage them).

Well, if there is somehow intelligent life on Venus, let’s hope they don’t confuse this rover for the first case of interplanetary terrorism.

There has been work done over the past year or so by the Department of Mysteries at St. Andrews College. They also are working on levitation, which I talked about before. They created an invisibility cloak that worked in the microwave region. A group in the US has just produced an invisibility cloak that works in the visible spectrum. The technology works by converting light that hits the surface into plasmons which then move around the object like water around a rock in a stream.

There are a few disappointing caveats here. First, the technology only works in two dimensions at the moment. Controlling plasmons in three dimensions would be considerably more complicated and is unlikely to be done, according to John Pendry of Imperial College. Second, it’s not clear that the plasmons won’t reflect light themselves, which means an invisible object would have a glare on it similar to glass.

There are potential applications for computer chips, though, so we’ll see. As cool as invisibility cloaks are, there really is no good use for them. If you can think of one that isn’t just as evil in the wrong hands, leave me a comment. The only thing I can come up with involves the military or peeping Toms.

Beam me up!

Posted: 24 August 2007 in Uncategorized
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I love reading an innocuously titled science piece and then coming across an absolute gem like this:

“Australian and French scientists have made another breakthrough in the technology that will drive next generation computers and teleportation.”

Teleportation?

Quantum teleportation as it turns out.  Which is much different from the conventional teleportation featured in The Fly or the transporter from Star Trek.  Quantum teleportation deals with transmitting the state information of a qubit from one location to another, which I don’t even pretend to understand.  So was this just sensationalism on the part of the University of Queensland?  Or do I just get my hopes up when I see sci-fi brought to life?

 University of Queensland Press Release

No seriously. Well, progress sort of. Theoretical progress, at any rate, and still hinging on one monster of a caveat: that spacetime is curved appropriately.

A group of researchers led by Amos Ori at the Technion in Israel has developed a theoretical model that overcomes a major hurdle in the current time travel theory. First of all, time travel requires the existence of closed timelike curves (CTC, aka closed timelike loops). In relativity theory, every particle has a worldline that describes its position in space and time throughout its existence. If the particle is in orbit around a mass of very high density that is greatly curving spacetime, it is possible that the worldline of this particle curves back on itself not only in space, but in time. The major hurdle in current theory is that for a time machine to exist, it would have to have negative density (another interesting topic, but I’ll have to save it for some other time). So according to Ori’s new theory, all that is needed is for gravity to have already begun curving spacetime appropriately and then for us to create “a vacuum space that contains a region field with standard positive density material.”

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