Saturday, September 22, 2007

Inflated Darkness

Louise: How did you get here?
Johnny: Well, basically, there was this little dot, right? And the dot went bang and the bang expanded. Energy formed into matter, matter cooled, matter lived, the amoeba to fish, to fish to fowl, to fowl to frog, to frog to mammal, the mammal to monkey, to monkey to man, amo amas amat, quid pro quo, memento mori, ad infinitum, sprinkle on a little bit of grated cheese and leave under the grill till Doomsday. ~From the movie Naked

Dark matter continues to spawn endless ideas about what it might be. It's not like dark energy, which is still a debatable entity. There has been indirect observational evidence of the effects of dark matter on distant galaxies; the Hubble Space Telescope has been used to attempt to map it's distribution. So we've got something that seems to exist, but we don't know what is, and we can't see it because, well, it's dark. But that certainly doesn't stop scientists from coming up with new theories about what it might be.

Lately, thinking seems to have sprung up liking dark matter and inflation. "Inflation" is an event that was theorized by Alan Guth to try to explain some puzzling contradictions in the Big Bang theory. According to Dr. Guth, soon after the Big Bang (we're talking very, very small time units here), the baby Universe underwent a sudden expansion, which he called inflation. His theory has become fundamental to the Big Bang theory, so there are always researchers attempting to gain a greater understanding of what the event might have been like and what the overall consequences of it might have been and might be continuing to be.

One group is thinking that inflation may have spawned or been spawned by an immense number of primordial black holes (PBH's, not to be confused with Scott Adams' PHB). The time immediately after the Big Bang is point when matter and energy were compressed enormously, which is an ideal way to get black holes. The PHB's, excuse me, PBH's then, could have been a contributory cause to inflation. Conversely, the inflation event itself could have caused the PBH's to form. Either way, the question becomes, "What happened to the PBH's?"

One answer is that they may have evaporated, due to something called Hawking Radiation. Basically, as the black hole sits there, it gives off a small amount of radiation, which eventually leads to the black hole evaporating away. Given the amount of time since the Big Bang, it would seem that most, if not all, of the PBH's could have simply fizzed into nothingness.

However, if there are any, they would be small but exceedingly massive, which would make them a nice candidate for being dark matter.

But, why have one theory when you can have two? Another scientist has decided that inflation was caused by a heretofore unknown particle called the inflaton. The inflaton, conveniently enough, has "weird properties we don't see in everyday particles." Even more conveniently, inflatons don't interact with normal matter, which is why we haven't found any of them lying around behind the sofa. Best of all, they do interact with each other, producing high energy radiation which might be detectable, if we find some radiation for which we have no other explanation. In the meantime, all these inflatons floating around unattached, undetectable, and noninteracting make a nice candidate for -- you guessed it-- dark matter.


Miniature black holes have been raised as a possible source for the Universe's missing mass before, so a theory that demonstrates a possible source for large numbers of them has some credibility. On the other hand, invoking mysterious particles that are completely different from anything else and conveniently explain some things by their presence is pretty shaky stuff. It's another Phlogiston theory on a cosmological scale.

Far be it for me to criticize real scientists working out new theories. Even the inflaton theory took someone a lot of time and effort to think up. But, dark matter is strange enough without invoking a particle we can't detect directly. It's especially shaky in that it seems to ignore the fact that dark matter is (evidently) exerting gravitational effects on very visible matter, which I would call "interacting."

On the other hand, dark matter has to be pretty weird stuff to begin with, so who knows? Maybe inflatons are a candidate. Personally, though, I'd be more inclined to accept PBH's.

Or maybe even PHB's.

Friday, September 14, 2007

Fifty Years in Space

All right. Let's get on with it!— T. Keith Glennan, first NASA administrator, regarding the space program, 7 October 1958

How time flies when you're having fun.

The ESA's Venus Express has been slinging itself around Venus for over 500 days. Cassini was launched 10 years ago in October and has been sending back goodies from Saturn for over three years. The Mars Rovers are into the 44th month of their 90 day mission.

But, these guys, amazing that they are, are pikers.

The Voyager probes are thirty years old this month and still going strong. which isn't bad for a mission that was supposed to last 5 years. Currently, they're the long-distance record holders for objects launched by human beings.

For pure longevity, Pioneer 10 takes the prize, still barely functioning. For a long time, Pioneer 10 and 11 were the distance champs, but the faster Voyager vehicles passed them a few years ago. The Pioneers have also posed a puzzle to scientists because they don't seem to be where they should be. All sorts of ideas have been proposed for why this is, including something wrong with the theory of gravity (why won't these guys leave Einstein alone?), but it seems that opinion is moving toward more mundane causes, such as dust, heat from the nuclear power sources, and collisions with alien vessels. Okay, I made the last one up, but it makes more sense than saying that theories of gravity need "tinkering".

Planetary exploration began to take center stage when the Pioneers sent back their grainy pictures of Jupiter and Saturn. I say "grainy", but those shots were amazing stuff when they came back. They represented a leap in our technological abilities. When the Voyagers arrived at the outer planets, we were again stunned by the information sent back, and a new generation of planetary astronomers began to yearn for more. Thus came Gallileo and Cassini.

The wonder of it all is that the more we learn the more we want to know.

But, if you want a truly epochal event, you have to look at October 4, 1957, the day the Soviet Union launched Sputnik.

It's hard to believe that it's been fifty years since the American public was shocked out of its post-war complacency to find a basketball-sized hunk of electronics circling the Earth. Our own attempts at building ballistic missiles had been feeble by comparison with the various military services each doing their own thing. In an attempt to save face, the Navy rushed a launch of it's Vanguard rocket, tipped with a little orbiter. The entire world was able to watch on television as the missile rose a few feet only to come crashing down and explode in a massive fireball.

President Dwight D. Eisenhower was not amused. While the military struggled to get something launched (the Army eventually launched Explorer on a Jupiter-C, a modified Redstone missle), Ike decided that the only way we were going to succeed in space was to have a central agency calling the shots; thus was NASA born. He also noticed that what space program we did have was completely dependent on a bunch of German rocket scientists that came to the U.S. after WWII. Obviously, we needed to do something to get our educational system so we could produce our own technically competent people.

And produce them we did. What they produced changed not only spaceflight but the world in which we live.

Take computers as a simple example. It is now popular to bad-mouth the computers that the Apollo astronauts had to guide them to the Moon and back. What people choose to forget is that these machines were beyond state of the art when it came to miniaturization and computing ability. When you use your MP3 player or pull out you slim little laptop and connect wirelessly to the Internet, you utilizing the fruits of that "primitive" computer.

Without the space program, I wonder if technology ever would have advanced to the stage it's reached today.

All that technology has been great (for the most part), but the real reward has been the knowledge gained. We've learned more about how our own planet works by discovering phenomena on other worlds. And we have the continuing opportunity to search for life somewhere other than Earth.

Perhaps the most amazing thing is that, instead of competing with other countries to do this, many nations have come together to work cooperatively. Unfortunately, this hasn't extended to returning to the moon, where, once again, it's every country for itself. Hopefully, at some point, the successes in planetary exploration and even the clunky old ISS will convince the holdouts that cooperation is a good thing.

The upside is limitless.

Tuesday, September 04, 2007

Another Hole in Dark Energy?

Great scientific discoveries have been made by men seeking to verify quite erroneous theories about the nature of things. ~Aldous Huxley

Dark energy is beginning to bug people.

I've written quite a bit about dark energy because it's one of those hot topics these days. A lot of theories depend on its existence . A lot of theories, though, depended on the Newtonian view of gravity, which works very well on local scales but doesn't work too well at very large scales. It took an Einstein to explain the real nature of gravity, and his views continue to be upheld by observational evidence. But Einstein even had what he considered to be a wayward turn, which was the introduction of the cosmological constant. The constant was put into his Field Equation to keep the universe in a static state. When Edwin Hubble determined that the universe was indeed not static but expanding, Einstein happily removed the constant, calling it his "greatest mistake."

As time has gone on, scientists have come to the uncomfortable realization that we don't understand everything we should about the universe's makeup. In particular, some of it seems to be invisible. Dark matter, the original candidate for the missing stuff, has been inferred from numerous observations, although the observations have not yielded consistent results about the behavior of the mysterious stuff.

After a while, it seemed that dark matter, which we didn't understand fully, didn't account for enough of the gravitational effects observed, including what appeared to be an acceleration of the expansion of the universe (which ought to be slowing down according to conventional Big Bang theory). Enter dark energy, something we understand even less than we understand dark matter, which we barely understand at all.

Dark energy is not sitting well with a lot of cosmologists, I think. The most recent attack on dark energy comes from a group of scientists who have created the "Swiss Cheese" model of the universe. That name is going to need some work, I think.

Anyway, this model says that the universe is not as homogeneous as we think it is. The standard model these days, backed up by limited observational evidence, says the the universe is relatively uniform in scales up to 100 million light years or so. However, new data indicates that space is "hokey" (to quote the article) on scales of 500 million light years. In other worlds, there be empty spaces in our universe.

It turns out that this wreaks hob with the standard model of the universe.

It hasn't helped the dark energy folks that, almost perfectly timed with the other announcement, comes word that a bored scientist found a billion-light-year void in the universe. You may have seen this story with such lurid headlines as "VAST HOLE IN UNIVERSE FOUND!!", a headline the late, lamented Weekly World News would have been proud to publish. The void is not, of course, a "hole", but an area where there is an absence of matter and energy. I mentioned a bored scientist because the discovery was made because a team making observations at the Very Large Array in New Mexico decided on morning to take a break from what they were doing to point the array of radio telescopes at an anomalous area in the WMAP mapping of cosmic background radiation.

What they found was nothing, but nothing on a grand scale.

Dark energy is annoying, I think, because it's sort of a deus ex machina, even more so than dark matter. Just as the cosmological constant bothered Einstein because it was artificial, dark energy comes across as an artificial construct to explain something where the standard model breaks down. It's not that there isn't mysterious energy in the universe. For example, quantum theory predicts the existence of vacuum energy, a churning turmoil of particles that wink in and out of existence. This has been mentioned as a possible source of dark energy, but no where near the predicted values for observable dark energy have been found.

Dark energy is also seductive just because it's a repulsive force, in other words, anti-gravity. Somewhere in the back of many minds is the idea, I'm sure, that this mysterious force, once identified, could somehow be harnessed to give us those mysterious propulsion sytems that power the Enterprise around the galaxy. Just add a little dilithium, and we're good to go.

Einstein never liked the cosmological constant. Despite countless attempts over the years to knock elements of General and Special Relativity down, the theories keep ringing true, with its testable predictions being upheld by observational evidence. Yet here are scientists trying to put the constant back to make dark energy fit standard model.

Maybe old Albert was right. If he was, scientists need to look elsewhere to fix their models.