Time travel?

We're all traveling through time, sort of. It's not that great though because we all travel through time at the same rate, at one second per second. The trick then is to travel at more than one second per second, or less, or even travel at negative one second per second. Fortunately, help is at hand because time travel is in fact possible, according to the laws of General Relativity anyway. Unfortunately, it doesn't involve a simple and cheap flux capacitor dissipating 1.21 GW. You need gravity, because you have to severely distort spacetime. In essence, there are two ways of making a time machine and both of them involve a singularity. A singularity is the sort of thing you get in the center of a black hole. It is a point, line or sheet of infinite density. When very massive stars die they sometimes collapse into a singularity, which is almost always obscured by the event horizon of a black hole. However there is no law that says they have to be hidden from view. But I digress.
When some matter collapses into a singularity it forms, for a very brief instant, a wormhole to another region of spacetime, in this universe or, more controversially, another universe entirely. The wormhole immediately pinches off though, but there is a way around that. What you need is some exotic matter, which is predicted to be left over from the big bang. No such matter has ever been found but in time with space exploration perhaps we might find some. What we need is cosmic string. Cosmic string possesses a peculiar property called negative pressure, which we can use to keep the wormhole open. Once we have created a wormhole, and located the other end, we must then move one mouth of the wormhole around at very high speed (I think you can see how difficult this is going to be) so that time slows down for it. Moving clocks run slow, so time slows down for moving wormhole mouths. We need to move it around fast enough for long enough to create and appreciable time difference between the two mouths. Then all we have to do is bring the two mouths together. If you travel from the mouth that moved to the mouth that remained stationary you will effectively travel into the future, whereas if you travel in the other direction, you will travel backwards in time. You can never travel backwards in time earlier than the creation of the wormhole though.
The second way to make a time machine is to take some neutron stars, ten will do, and spin them up really really fast. So fast that at the surface the instantaneous velocity is about half the speed of light. Then you need to align them all so they're pole to pole and they will collapse into a spindle singularity. At this point you may travel through time using the spinning singularity. It works because a rotating mass drags spacetime around with it, in theory. The earth does this too but you don't notice the effect because the earth is rotating very very slowly, and it is extremely light. But it's real, according to Einstein, and data is now available to confirm or refute it. The data is still being analysed, but it's assumed that it will be right. Anyway, in the region around a very quickly spinning, very heavy singularity, the effect is so strong that time and space start to interchange, so you can travel in a closed orbit around the equator of the singularity to travel forwards in time, or in the reverse direction to travel backwards in time. Again, you can only travel back to the moment is was created, but hey, it's time travel, and there's nothing that says you can't do it.

Greatness

What is greatness? Is it a quality with which one is born, or must it be earned? Is it merely the possession of great power, as in a great ruler, or is it something more? Is it mastery of your chosen path, or is it nothing to do with knowledge and power?

I think greatness is a quality of all who are truly good, who truly seek to serve and sacrifice themselves for others. Evil can never have greatness; it is a quality belonging only to those who are good and who act upon it. Evil can of course be great - some evils are worse than others, and more powerful than others, but that is largeness, not greatness. To be truly great one must serve.

At lest, that is how I see it.

Helium

Helium. On the face of it, rather a boring element. Doesn't really react chemically with anything. Most people's only contact with helium is in the form of helium balloons. Actually, though, helium is a very valuable resource. You might think that because it's very light, and all elements apart from hydrogen are the result of nuclear reactions, that it is common. And you'd be right - it makes up about 10-20% of all mass in the universe. The rest is hydrogen - all the other elements combined are insignificant. Down here on earth things are different, though. Here we have gravity to worry about. When helium reaches the upper atmosphere, some of it escapes into space. The reason for this is that at any given temperature, a volume of gas will contain some particles that are traveling faster and some that are traveling slower. The average of all these velocities gives the temperature. In the upper atmosphere some helium particles travel so fast that they escape the earth's gravity well. Escape velocity: Ve = sqrt(2Gm/r) where G is the universal gravitational constant, m is the mass of the body and r is the distance from the center of mass. Escape velocity from the earth's surface is about 11.2 km/s, which is of course VERY fast, faster than anything. It's about three hundred times the speed of sound. In the uppermost reaches of the atmosphere, at an altitude of 10,000 km the escape velocity is only 8.9 km/s. Now, of course, heavier gases will have lower RMS velocities because RMS kinetic energy is the same for all gases at a given temperature. Radon, one of the heaviest gases, is about fifty times heavier than helium. Kinetic energy: Ek = 1/2mv^2 where m is the mass of the body and v is its velocity. So radon's RMS velocity is just 13% that of helium. Heavy gases are not buoyant enough to reach the upper atmosphere though. Helium and hydrogen are and a lot of both of these gases is lost each year. Luckily we have plenty of hydrogen, locked away in water and other compounds. But helium doesn't form any compounds, because its electrons are very tightly bound, so it just migrates to the upper atmosphere and escapes. Jupiter doesn't have this problem so severely - it has such a powerful gravitational field that not even hydrogen can escape in any great amount. The same is true of Saturn and the other gas planets.
So our helium is escaping, slowly. So what. Well, there are a few natural processes that produce more helium, chief among which is radioactive decay. When Uranium decays eventually to lead it releases a few atoms of 4He on the way there, and these get trapped underground in oil wells and natural gas, which is where we get most of our helium from. Some 3He is formed by interactions in the upper atmosphere as well - when cosmic radiation starts frying nitrogen that's up there. These are the only sources of helium on earth, so we would be wise not to be so cavalier about the way we use it - balloons for instance.
So what is helium good for? Well, if you want to go SCUBA diving really far down, you're going to have to deal with the problem of the bends, eventually. At depth, the air you're breathing has to be higher pressure, to match the pressure of the water, and at high pressure the solubility of nitrogen in your blood increases dramatically. When you return to the surface too quickly the nitrogen becomes less soluble, and can't be breathed out fast enough, so it forms bubbles in your blood, same way a carbonated drink forms bubbles when it's opened. Helium has such a high RMS velocity that it doesn't dissolve in your blood very much at all, so if you breathe oxygen mixed with helium, you can go down to much greater depths and pressures without worrying too much about decompression.
Helium is also very useful for low temperature physics. Helium has no nett dipole moment, so helium atoms don't attract one another very well at all. It's also very light which means that it's fast, and quantum mechanical juggling due to uncertainty is very big. All this means that helium has to be at a very low temperature before it will liquefy. Helium doesn't freeze at all. Ever. So you can use it as a refrigerant gas for making things very cold because it's still a gas at 5K. It also behaves very strangely at these temperatures. It becomes a superfluid at around 2K - it's a sharp changeover, much like a change from liquid to solid. This means that it stops behaving like a regular fluid and starts behaving like a quantum mechanical fluid. This means, for one thing, that it can only have integer values of turbulence and rotation. Practically, this means that you can spin a bucket of liquid helium and the fluid will stay still until you spin the bucket fast enough for the first rotational quantum value. So it has stepwise rotation. It also flows with zero friction though fine tubes because it cannot become turbulent. It can only allow eddies of a certain size and angular momentum, and below this size no eddies can form, so no energy can be dissipated. An experiment has been conducted where a hollow torus was filled with fine powder and then liquid helium. The helium was set flowing around the ring, and it never stops. Water molecules would bash into the fine powder and stop flowing very quickly, but helium can't become turbulent at that scale so it just keeps on flowing.
It's interesting stuff, helium. Think about that next time you let a balloon float up into the sky.

Here we go again

My last few attempts to create a blog were beset by difficulties, chief among which was the fact that I didn't have the determination to continue. So lets see how it turns out this time around.

I think it's probably fitting to start with an update on where things are in relation to me.

Currently I'm a student at Monash University in Clayton, and have been for the last two and a half years, roughly, which means right about now is the Monash exam period. Oh joy. I have about nine days to study for my exams, then I'm traveling to Adelaide to see my girlfriend of two months, before returning here to Melbourne with her. Then it's crunch time. After that there's a rather different kind of crunch time when I have my 21st birthday party. Sooo many things stressing me. And so much time to be stressed in. Basically the whole of June can be written off as a total loss. But at least I'll have Karina with me.