Friday, May 22, 2009

Gravitational Waves or the Hidden Whisperings of the Universe

Information is a seriously contemplated topic in the realm of theoretical physics. It's absolutely everywhere. When I look out my window here at my desk, light hits my eyes telling me there is a sparrow perched on the bush outside (I know I am incredibly lucky to have a desk with a window). All the leaves, the trunks of the trees, the blue sky, the grassy field beyond, the inidividual blades of grass, information about all these things are simultaneously being transmitted to me via electromagnetic radiation - light. It would seem light is the loudest kind of information we have. There is light everywhere in our lives. The next loudest would be sound. So long as we are surrounded by enough matter, we will hear sound. My computer is humming away, the air-conditioner is churning and every now and then, I hear a truck drive by. This is further information. Sound travels through the medium of matter. Massive objects have the ability to propagate sound. Light travels through the medium of the electromagnetic field. The electromagnetic field spans all space and tells charged particles how to behave. Changes in the electric field occur through this radiation. If a particle moves, a little signal is sent through the electromagnetic field as a light wave. Thus I see the leaves waving in the wind.

There are other more difficult kinds of information to notice. Radio waves and infrared signals are both electromagnetic radiation - just a different wavelength than light. There's many more classifications among those. Over the last century, we've gotten pretty goo at detecting them. We've even found this Cosmic Microwave Background radiation that seems to be telling us that the universe was once expanding in this incredibly hot fireball that grew at an amazing rate. There is, however, a kind of signal that is very hard to hear. It's almost the secret code that permeates the universe. We've actually not heard it before, but we have very good reason to believe it exists.

A lot of people have heard of Einstein. You might have heard of energy being mass times the speed of light squared? Well, that's a simplification of what he said in Special Relativity. The really important thing he said in Special Relativity is that information cannot travel faster than the speed of light (approx. 300,000 km/s). This is one of those fundamental laws of physics that every first year student wants to show is wrong and yet we never find a situation that upon careful examination does not comply with. The problem is, Einstein saw something that apparently did not comply with it..

As I said before, information is carried by light. It takes light about eight minutes to get from the Sun to the Earth. That means, if the Sun were to suddenly cease to exist, we would still have light for about eight minutes. This doesn't sound like a problem with the speed of information barrier. What is a problem is when you examine gravity. Over a hundred years ago, the prevailing theory of gravity is the same one we still teach in highschool physics today - Newton's law of gravity. It goes something like, the force of gravity between two objects is proportional to the masses multiplied together divided by the square of the distance in between. Look at what I just said carefully and you'll notice that I never mention time in that statement. What that suggests is that if the sun magically ceased to exist, we would instantaneously go flying off into space. We would still see the Sun, but we would know we were doomed because we wouldn't be orbiting it anymore.

Enter Einstein's General Theory of Relativity. The theory says that gravity is curvature. If you imagine a sphere with two people starting on the equator, imagine them walking north. Initially they are walking on parallel lines but the curvature of the sphere brings those two paths, always walking north, together. If you imagine north as the direction of time, you could then imagine how curvature brings two objects together. The obvious question is, what is being curved? My less obvious answer is space and time itself. Gravity is the curvature of space and time determining the direction objects move. Further, objects and their movements determine the shape of space and time. The next question is why does this fix our little problem with information? The answer to that is when an object changes in some way, that change is registered in the curvature of space-time and a ripple that propagates out from the object at the speed of light. Now, if the Sun were to disappear, we'd be in the dark figuratively speaking until we were in the dark litterally. It would take about eight minutes before we'd start feeling the lack of gravity from the Sun.

Einstein came up with this theory in the early twentieth century and we still haven't detected gravitational waves. We have good reason to believe this theory, however. If this theory is true, then gravity should divert light, which it does. In fact, gravitational lensing hasbeen used to get more information using our best telescopes. Effectively, large galaxies in between us and what we want to see bend the light from what we're looking at and refocus it like a lense does. Further, GPS systems make use of a correction term determined from General Relativity. Without the term, we could not have GPS guided airplanes. So we definitely think this theory has merit - we just haven't detected gravitational waves yet...

...but we're close. You see, gravitational waves are what's called a weakly interacting signal. That's physics jargon for gravity being weak compared to other forces. While we all know the feel of being stuck to the ground, the only reason that force is so immense is that there is so much matter to the Earth. We don't feel the electric pull so much because the Earth is mostly neutral. However, if you have ever been near where a lightning blot hits, I'm sure you recognize the emmense power of electricity. All this means that gravitational waves are very hard to hear. It takes very massive objects moving very quickly to create gravitational waves of the sort to produce a signal we could measure effectively. Then it takes some very careful equipment.

An interferometer is a device that fires a laser down one path and down another at a right angle. The beams bounce off a mirror back down the same paths. The beams are recombined and small differences in the length of the paths can be measured by the interaction. Well, a gravitational wave sends a little ripple in space and time itself. This can stretch one arm of an interferometer while shrinking the other. Remember, however, I said gravity is weakly interacting. I can't just do this expiriment on a table top. To detect gravitational waves, we're working on a project called LIGO or Laser Interferometric Gravitational-Wave Observatory. There are two locations for this project, one in Livingston, LA and the other in Hanford, WA. Just google LIGO to see some pictures. These are interferometers that fire lasers down four kilometer long vacuum chambers and are looking to detect a change in distance a thousandth the size of a proton. Now, I'm on the theoretical side of things so I can't accurately give you all the details on what they're doing but needless to say this is one of the most sophisticated scientific observing expiriments ever created.

What we expect to hear is the really amazing part. Perhaps the most likely source of gravitational waves to be detected by LIGO will come from orbiting binary black holes around thirty times the mass of the Sun. Black holes are objects so massive that the gravity doesn't even let light escape. We have only seen hints of black holes - places in the centers of galaxies where there doesn't appear to be anything except that other stars are orbiting those locations and pulsars which seem incredibly consistant with the idea that a black hole is powering them. This would be the first direct evidence of a black hole - and it could imply two of them. Think about it. These massive objects that can change the way galaxies behave orbiting togetehr and emitting powerful gravitational waves that due to the weak interaction, we have to go to extremes to see. It is as if some of the most fantastic information to be gathered about some of the most massive objects in the universe is hidden in a code that requires extreme effort to find. That is why this is titled, Gravitational Waves or the Hidden Whispering of the Universe.

Saturday, May 16, 2009

I'm really scared.

So I'm really scared. We're basically getting rid of everything we have and taking a one-way ticket to another land across the ocean. When we go, we won't have a return ticket in hand. I mean, it's exciting, don't get me wrong. We're going to be living in Germany for the next two to three years. That's absolutely awesome. It's also the scariest thing I have done.

I spent about five months in Egypt while I was in college. It was a study abroad program. That was different. Back then, I had very few responsibilities. I certainly didn't have to think of such grown up things as saving for retirement one day and ensuring my wife was going to be happy. I guess I can't ensure any of that.

I am so used to having control over what happens to me. I am so used to using my judgement to make sure everything is going to be ok. Today I live in Winston-Salem, NC. I have never in my life been happier than living here. I am scared out of my mind of what will happen when we move. We even need to leave our cat behind. I am going to miss her.

I am going to miss all the friends I have here. I am going to miss knowing Dave at City Beverage telling me what this beer is and where it came from. Dave makes really cool animations. Disney would prove themselves idiots if they don't pick him up soon. I'm going to miss my friends at the Med-school who've made their lives more permanent there. I'm going to miss the friends who are coming over tonight.

Six years and a PhD and all the memories I could ever ask for. Thursday I am going to a friends to brew beer with him. I told him I wanted to do the full process one more time (I use extracts, he uses whole grains) before I left town. Really I just want some more time with just him before I leave. Six years may not seem like much, but it's a long time. It's time enough to meet the love of your life, get married and find the best friends you've ever had. It's time enough to learn you can really contribute to something. It's time enough to learn you find friends in all sorts of places.

When I was seventeen, my family had to move from Houston, TX to New Orleans, LA. I thought I'd never feel like I was home ever again. There's that feeling that you have, that sense of comfort and belonging that is so hard to find otherwise. I lived in New Orleans and Birmingham, AL and Greencastle, IN and never felt at home. I was fine during most of those times because I had let go of the idea of home. I came here in the same mind-set. At first, this was just another place. Over time, it felt like home. I finaly felt like I belong. I finaly had that feeling that I hadn't had since I was a child.

I know, I absolutely know I have to move on. It's time. I defend at the end of June. It's time for me to move on. I just hope I find half as much where I am going as I have found here.

Wednesday, May 13, 2009

It may be a small world...

...but the universe is quite big, getting bigger and even accelerating. It took me a long time to learn to accept this concept. A friend reminded me a while ago of my own troubles with it. He asked me, "if the universe is expanding, what's it expanding into." I don't put a question mark on it because I don't think he really intended it as a question so much as a statement. I believe that because when I replied, "I'm not entirely sure it's expanding into anything", he got angry with me. It is, however, a valid question so long as it ends in a question mark. For a long time during my college education I spent evenings asking myself the question but then not having the question mark at the end myself.

Before going on, I would point out because only recently I learned, a priori means before gathering evidence (at least that's what it means to physicists).

Scientifically, I don't know that the question neccesarily has meaning. I also don't know that the question doesn't. Let's say, for argument, the entirety of existance at this given slice of time occupies a finite volume. Scratch that. I can't use the word occupies. Let me start over. Let's say, for argument, the entirety of existance at this given slice in time has finite dimension. That's better. I'm asuming less that way. (This is how physicists think by the way. We're always tyring to get rid of unneccesary assumptions.) Now I am talking about all of existance. If there were something outside of it, that wouldn't make sense because I am talking about all of existance. A priori, there is no reason for me to think that all of existance must be infinite. I have no experience measuring the entirety of existance and so I can make no natural assumption about that. Let's then just say it isn't infinite for the sake of argument.

Is there then a problem with that finite dimension changing as we move forward in time? This is generally where the question arises. If it's getting smaller, then where did the missing parts go? If it's getting bigger, then where did it get the new parts? This is, however, a very human view of time being used in this way of thinking. To our normal lives, time is different than space. I can measure the length of something spacially with a measuring tape. I cannot so measure the length of something in time. This yields a very common-sense (and very practical) view of time as something intrinsically different than space.

I am not going to tell you this view of time is wrong. However, I will also not tell you this view of time is correct. I have no experience divining the nature of time versus space and, a priori, I can't decide whether they are the same or different. Let us then say for the sake of argument that time is not different than space but rather our different methods of measuring space and time are artifacts of some other part of physics. If time and space are intrinsically the same, this changes how one interprets the idea of the universe getting larger or smaller in time.

Imagine in your mind a cone pointing downward. Imagine then that I take a series of slices of that cone perpindicular to your view. In other words, each slice is a very clean circle. As I move up the cone, the circles are getting larger. Let's say that cone is the universe. All existance is this cone. More importantly though, rather than a three dimensional cone, it's a four-dimensional cone. In four dimensions, a cone is defined as three-dimensional spheres getting linearly larger as you move along the fourth dimension. What I have described is a universe which is getting bigger without having to rely on it expanding into anything. If time is no longer special, then the universe can grow in time the same way the radius of a cone grows as you move along a given dimension. It is not growing into anything, but rather the universe is of a certain shape, and our choice of time is artificial.

A priori I don't know whether time is different than space or not. A priori I don't know if space is finite or infinite. However, there seems to be a combination of these possibilities that allows for an expanding universe in which the universe does not have to expand into anything. This is my understanding of what some people who study this particular phenomenon are saying. I hope you find my description helps you understand what these people are saying.

Friday, May 8, 2009

Why beer isn't compared to women.

You know how men compare women to cars and talk about where they got with a woman in terms of baseball. I was asked once why men never compare women to beer. Well, I thought about it and this is what would happen if men compared women to beer...

1. I like my women like I like my beer, stout and full bodied...

2. I like my women like I like my beer, pale and bitter...

3. I like my beer, strong and yielding good head...

4. ...with pretzels?

5. ...from a bar?

6. ...served cold?

7. I like to try a new beer as often as I can...

8. ...the more, the better...

9. If I have too much, it makes me sick...

10. I like my beer, frequently and of different styles.

I'll be the first to admit, we men can be awefully dense sometimes. However, every now and then we get something right. So this is why we never compare women to beer.