OK, I admit it. I love junk science. Put on Nova - I’m there. Worse - Discovery Channel, History Channel, National Geographic (if I had it), Archaeology, Paleontology, Geology, Meteorology, as long as they’re not talking bible codes, zoocryptology, or ESP, I’m watching.
One technique they often use with fossils, especially with skulls, is to take CAT-scans of them. And I often wonder why. Why can’t they just pour ballistics gel or something like that into the skull and get a mold of the interior? Won’t that show them the dimensions just as well? What does CAT-scanning show them that a mold wouldn’t, besides money flying out the window and fancy computer graphics?
How would they get the gel out? Without destroying the skull?
Taking a mold gives you a look at only the outside. If you pour gel or plaster into the skull or whaever, you will need to break the skull. Fossils can be rare and you would not want to casually destory one.
CAT scans give a look into the interior that is non-invasive. Leaving the fossil intact for later study, with newer and better techniques.
Well, that’s why I suggested gel. I assumed (perhaps incorrectly) that a gel mold could be removed without destroying the skull, because it’s flexible. I take it that it can’t?
If you had half a skull, maybe, but the only way you’d be able to remove it otherwise would be pulling it through the maxilla. If it was flexible enough to fit through an opening that small, it wouldn’t keep much of its shape.
Up to a point, I think you can pull a positive model out of a negative mold, if the material is resilient enough - otherwise, we’d never be able to cast intricate objects with curliques more than once. However, just how much material can be pulled out through, say a nasal opening, without tearing, crumbling, or fracturing would be a real limitation of the material itself.
I’ve done alginate casting (the stuff dentists use to cast your teeth), and it’s pretty darn flexible. So is latex. But there’s flexible, and then there’s ductile and reformable (able to be pulled thin and then return to its original shape).
I’m sure I’ve seen demonstrations of castings being done like that - pouring a small amount of some fast-setting flexible compound in through a hole, rolling the hollow object around so as to coat the inside, then pulling it out when it’s set. I suppose it will not work very well for objects which might have very irregular or snaggy insides.
modern CT or CAT (computed axial tomography) scanning allows you to produce a non-descructive 3-dimensional model of the object under study. The greatest breakthroughs in CT has had to do with post-processing of the acquired data. Traditionally displayed slice by slice (which personally I think resembles the steaks you buy at the grocer) CT can now render 3d images of the object that you can rotate along the 3 axis.
Another major advantage of this technology is that unlike “flat” X-Rays, CT recognizes the differences in density between tissues or materials and assigns them a special value referred to as a Houndsfield Unit. computers can therefore be used to selectively display and filter out material based on their density. For medical use for example (assuming the study was properly acquired) you can have the system display the blood vessels, or muscles WITHOUT the bone. Or the skeleton without the soft tissue. If you have a fossil or artifact there’s embedded in rock or some other contaminent from which it would be difficult to extract without destroying the object (such as the Antikythera mechanism), CT can let you see inside the object without having to break it apart or damage, and separate the material you want to study from the contaminents, as long as they have different densities. You could then take the 3d rendered image of the skull you mentioned and send it to a 3-dimensional prototyper and have it produce a very accurate plastic model of the skull. Powerstuff stuff indeed!
OK, thank you all very much! This is what I wanted to know, because it seemed to me on the surface of it to be a waste of money just to use a sexier technology. Now it appears that there is true scientific justification for it, and that’s good enough for me!
