Saturday, February 23, 2008

The Big Bangs

I have had my results for a long time: but I do not yet know how I am to arrive at them. ~Karl Friedrich Gauss

Wired recently interviewed Neil Turok about his theories concerning the start of the universe. I suspect the interview is poorly edited, since the questions and answers are somewhat disjointed, but the point that comes across is that Mr. Turok thinks that the creation of our universe is just one creation event among many that have and will occur. His mechanism of choice for creation events is the collision of branes.

Frankly, this isn't really news. I don't know if Mr. Turok was the first to suggest it, but the theory has been around for a long time; I even discussed it a couple of years ago. "Branes" or m-branes or p-branes, whichever you prefer are an offshoot of string theory, the tangled theory of everything that doesn't actually predict much of anything.

The reason that string theory maintains its hold, I think, is that the conventional Big Bang theorists have their own dirty little secret: The singularity. Everyone agrees that the universe is expanding (at what rate is open to question). Since it's now expanding, it's logical to assume that, if you could run the cosmic clock backwards, you could arrive at some sort of starting conditions that would, basically, be the moment of creation. The problem is that you can run that clock back to some ridiculously small amount of time immediately after the initial event (the Big Bang itself), but you can't get back to the initial condition because at this point the laws of physics break down. They break down because the collapsing of the universe into its starting point arrives at a singularity, which, mathematically speaking, is a point where all the equations blow up.

Physicists do not like singularities.

It is because of this dislike that string theory has found as many adherents as it has, because it has various ways around the singularity. One of these is brane theory. Basically, a universe is a brane (or membrane, if you prefer) flopping around in one of those eleven dimensions that string theory demands. Branes allow theorists to play funny with a lot of things, like assuming that gravity is weak in our brane because it comes across as "leakage" from a neighboring brane where gravity is strong as all get out.

It also allows for a creation event to be caused by the branes. Imagine, for a moment, a brane to be a sort of sheet flapping in the breeze. Now imagine two of these sheets with their broad sides parallel to one another flapping in the breeze. If they're close enough together, they will occasionally touch. Now if we accept the notion that there are many universes or branes undulating about in some extra dimension that our three-dimensional senses can't detect, it is possible, even likely, that they might occasionally touch in this manner. The touches are the points where Big Bang events occur. The new universe (brane) simply begins expanding "between" the two that touched and beings in the initial universes are none the wiser that some monumental event has occurred.

Now, people who are not disposed to like string theory, like Alan Guth, don't care for this theory. Also, the Catholic Church isn't crazy about it either, because it takes away the unique creation event that can be associated with God reaching out and saying, "Let there be light!" Why the Church should be upset is beyond me, because if God starts the universe, He has to be somewhere at the time. Why not be in a another brane?

Personally, I'm more interested in what the scientists think than the Catholic Church when it comes to the realm of physical knowledge and theory.

Mr. Turok even offers a means of testing his theory, in a negative sort of way. If Guth's Inflation theory is correct, he says, we should detect gravity waves from the event. Very cute, because, of course, we haven't detected any gravity waves. However, lots of events should create gravity waves, like the formation of a black hole or collisions between black holes, among other things, and we haven't detected any gravity waves from them either. The problem is that gravity waves would have a very long periodicity and would be very weak. They're bloody hard to detect, and in fact no one has yet.

However, no one has detected evidence of all those extra dimensions that string theory needs yet either, and I don't see Mr. Turok pointing out how that would seem to disprove the theory that forms the basis for the existence of branes.

There's also the pernicious question of where all this started. There must have been a first brane at some point, one would think. No, says Mr. Turok, because time runs forward, then backward, then kind of mills around and then runs forward again. If you though Stephen Hawking's concept of imaginary time was sort of out there, this one should set your head to spinning. Even Mr. Turok isn't exactly betting the farm on it, saying he's more interested in our creation event (and its singularity) and let future physicists try to deal with others.

I found especially disturbing was his response to the question that, irrespective of what he finds, it isn't going to "have much everyday importance." Mr. Turok agrees with this: "
No, but one of the extraordinary things about the field is that whatever culture people come from, they all love this stuff." I beg to differ. Should Mr. Turok or some other physicists determine beyond a shadow of a doubt how we came to be, it would have a huge impact on how people view their own lives. Furthermore, understanding the mechanism of creation would have a huge potential to lead to new methods of generating energy, which in turn could change the very economic structure of our world.

And that's just one potential consequence of finding out what happened at the singularity. Mr. Turok is downplaying what would conceivably be the most incredible discovery in the history of mankind. Why? Probably because all he has right now is a shaky theoretical construct based on a shaky theoretical foundation (string theory).

Something incredible happened 15 billion years ago. Even if it was one event in an infinite series of creations that have happened and will happen, We can look back to within an infinitesimal fraction of a second of the event, but there we are denied access. Gaining that access, should we ever do so, will change mankind forever.

That ain't small potatoes, Neil.

Saturday, February 09, 2008

The Dark Stuff Conundrum Goes On

For every fact there is an infinity of hypotheses. ~Robert M. Pirsig

Another day, another rationalization for why we can't find dark energy.
If it seems that I talk a lot about dark energy and dark matter, it's because I do. As soon as scientists stop issuing their theories du jour about the stuff, I'll stop. Today's stab in the dark is brought to us by Dr. HongSheng Zhao of the University of St. Andrews. If you recall, a big chunk of our universe appears to be missing, around 96% of it according to the article (it used to be 75%, but we've apparently lost even more lately). Physicists, cosmologists, and assorted other scientists have decided that this means there is something out there we can't see, taste, smell, or otherwise detect. They started out calling this "dark matter".

Along the way, the theorists decided that dark matter didn't account for everything that was missing, so they decided there was something called "dark energy" out there, too. It is even more mysterious than dark matter. Dark matter has been indirectly detected by examining the motion of stars around distant galaxies. Dark energy, on the other hand, hasn't been detected at all. In fact, it's only inferred effects have been found to not be working exactly as they ought.

Well, says Dr. Zhao, your problem is that dark energy and dark matter are actually the same thing. Now, the perceptive reader might well say, "Well, duh. Einstein demonstrated energy-mass equivalence a century ago, as in E=mc2. Nothing to see here, move along." Well, that does not appear to be what Dr. Zhao means. He means that, in fact, they are manifestations of the same thing, like, say, water and ice. He calls it "dark fluid." Furthermore, says the doctor, dark energy has already shown itself by masquerading as dark matter. Because, after all, they are equivalent.

Yes, that sounds like a rather circular argument to me, too.

The problem is that we need are this dark whatever-it-is because of what is perceived as the expansion rate of the universe, a rate determined by examining the distances to distant objects and the speed at which they appear to be receding. Unfortunately, the apparent speed is dependent on the apparent distance, which is dependent on a lot of assumptions about how we can tell how far away something is.

And those assumptions have changed enormously over time.

So scientists are searching for something that could conceivably not be nearly as abundant as they currently think it is, should the reigning "standard candle" (the type I-A supernova) turn out not to be such a standard after all.

And then there's this. According to what passes for the standard model of the universe these days, all galaxies are surrounded by dark matter. As noted above, this has been determined by studying the motions of stars in galaxies and finding out that stars well out from the galactic nucleus are going faster than they should. In fact, the only thing that would keep such fast-moving stars in the galaxy would be some unseen amount of mass in a halo around the galaxy.

Unfortunately, there's a galaxy with the prosaic name NGC 4736. This stars in this galaxy behave exactly as one would expect if there were no such thing as a halo of dark matter. So what, you say? What's one exceptional galaxy in a universe full of them? That's the problem. The universe is full of galaxies; we've looked at an incomprehensibly small number of them. Yet we've managed to find one that violates the idea that galaxies must be surrounded by dark matter.

The standard model (this week) considers dark matter as an essential construct in galactic formation. It is not good to find a perfectly normal galaxy out there that doesn't have any. Of course, many scientists aren't buying in to this announcement, primarily because they have too much invested in the dark matter-energy model (it's still a little early for the fluid part to be included).

What remains to be seen, of course, is whether any other galaxies will be found that appear to have no dark matter. If some are found, the naysayers will have to start coming up with theories to explain where the dark stuff went. It may even lend credence to the dark fluid interpretation.

They'll be able to say it floated away.