Sunday, December 30, 2007

Trading Bad for Worse

Science is a first-rate piece of furniture for a man's upper chamber, if he has common sense on the ground floor. ~Oliver Wendell Holmes, Sr.

Another day, another whacko theory.

As we are all aware, the prevailing thinking among cosmologists these days is that the universe is mostly made up of stuff that we can't see. One type of stuff is dark matter, for which there is some observational evidence. We don't know what it is exactly, but at least we can see what appear to be its effects.

The other stuff, which makes up most of the rest of the universe is dark energy, which we haven't found, can't define, and have no idea how to detect. Aside from that, it appears to be a sure thing.

Given this state of affairs, it's not surprising that some scientists are looking for alternative theories. I've discussed some alternative views, the "Swiss Cheese" theory (not a great name) and the "local collapse" theory. I've also mentioned the problem raised by some observational evidence that, while indicating the possible existence of dark energy in the ancient universe, doesn't show it behaving properly. It seems that dark energy should have been an attractive force in the early universe. The data, however, indicates that it was repulsive.

Frankly, the whole concept is getting pretty repulsive, if you ask me.

At any rate, another scientist who dislikes dark energy has come up with yet another way to avoid it altogether, by --and you're not going to believe this one -- postulating that time itself is slowing down.

I'm not sure that this is an improvement over dark energy.

The simple fact is that cosmologists have painted themselves into a corner with dark energy and don't know how to get out of it. The truth is that everything cosmologists are hypothesizing depends on know how big the universe is and how much stuff is in it. Figuring out astronomical distances has always been a problem, involving huge assumptions which have been subject to acrimonious debate among cosmologists, physicists, and astronomers. If you can't get a reasonable estimate of how far away something like a quasar is, then you can't accurately assess its speed, size, or red-shift.

If you don't know the answer to those questions, you don't know how fast everything is expanding.

When it comes to the mass of the universe, all of the assumptions are based on statistical extrapolations of sky surveys. The problem is that the statistics are only as good as our ability to determine how much stuff is in a particular volume of space. It now appears we have been fooled, in at least one instance, by stuff that's in the way. It seems that we've just found an entire cluster of galaxies where we didn't think one existed.

That's a lot of missing mass.

So as it stands, we're still not very sure how far away everything is and we're not sure how much of it we've actually accounted for. But, cosmologists and their brethren are still cranking out theories based on the best estimates we've got.

The trouble with that is that we darn well know that our assumptions are shaky. Astronomers are constantly campaigning for tools to help them get better observational data to determine distances and identify celestial objects that are hidden by gas and dust. It's reasonably clear from the problems being encountered by the dark energy crowd that we don't have a good enough handle on these fundamental facts yet.

I understand the need to theorize based on existing data. If nothing else, that sort of work tells us whether the data is sufficient and consistent enough. The answer to that question is, "Not yet." The obvious conclusion is that more data is needed, not more theories that make even less sense.

As Robert Machol once said, "If the assumptions are wrong, the conclusions are likely to be very good."

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