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.

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