Everyone knows the hardest material on Earth is diamond, says George Pharr, director of the Joint Institute for Advanced Materials at the University of Tennessee. But when it comes to the softest stuff on the planet, "there's no one definition," he says.
Metallurgists and mineralogists might interpret "softness" to mean a material's tendency to deform under pressure and to stay in that deformed state. But that reading might come off a little wonky when you start looking at elastic materials, like rubber, which can deform and then regain their form.
As a result of this ambiguity, researchers employ an array of hardness (or softness) tests, depending on what sort of material they're looking at. For minerals, they might use the classic (and exceedingly simple) Mohs assay, which involves rubbing one material against another to see which one gets scratched. According to the Mohs scale, talc, also known as soapstone, is the softest mineral; it is composed of a stack of weakly connected sheets that tend to slip apart under pressure.
When it comes to metals, scientists try to measure hardness in absolute terms. They press a ball- or pyramid-shaped bit into the material in question at a predetermined pressure and over a set period of time. Researchers then measure the dent left behind. The hardness of a metal, Pharr says, depends on the fraction of its bonds that happen to be covalent; these are strong, stable arrangements in which atoms share a pair of electrons.
Pliable metals like gold have fewer of these bonds than tougher materials like molybdenum and tungsten. Highly reactive metals with low melting points, such as cesium and rubidium, end up at the very softest end of the spectrum. Pharr warns that any attempt to pick out the absolute softest material, however, "would be subject to debate."
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If they all agree on what hardness is, softness just be something less hard?
Yes, standards are good. I would have thought they would have had a definition long ago. I am surprised.
I'm sure they would find Obama brains pretty mushy soft.
Just to let you know...Obama is a graduate of Columbia University and Harvard Law School, where he was president of the Harvard Law Review. He was a community organizer in Chicago before earning his law degree. He worked as a civil rights attorney in Chicago and taught constitutional law at the University of Chicago Law School from 1992 to 2004...".
While I did not vote for him. He is a accomplished, prior to being President.
I am curious, what is your background sir?
His academic records have never been released. Scientifically speaking, with the lack of empirical information, we must conclude that Obama never did any of the things you so casually mention.
What is YOUR background? If you were one of his professors, then please, by all means, enlighten us.
I do profess often, lol.....snort.
No, I was not Obama’s college professor. My source information for my above comment came from Wikipedia. So there you go. ;)
Sure, it isn't about his actual schooling...but I would say that if the university of chicago felt his schooling was sufficient to teach at their school, it is at least equal to those Robot mentioned, if not those exact same qualifications.
There is probably even more to be found out there as this involved about 30 seconds of looking to find.
"Hardness" is indeed incredibly difficult to measure. Even the typical Mohs scale is really fairly inaccurate, and usually is just a number from 1 to 10. This does not allow for any more precision, as it's just built around scratching the material, and its very common for materials to scratch each other. Alternate methods only work on certain materials.
It's also compounded by how you define a material. Is a clump of dirt a really soft material, or should it be considered separate? It would seem easy to just say it's a clump of separate smaller pieces of dirt, but the problem is when you try to draw a line. You can easily work your way up through various sandstones and such and come all the way to diamond with there never being a sudden and clear line.
Just some food for thought:)
There are several well defined hardness tests such as Knoop, Vickers and Rockwell. They work well on metals, ceramics and plastics. The system and standards have been well developed over time and depend upon the depth and shape of penetration of an indentation device under a defined load.
However, I can appreciate the difficulity of trying to measure a soft material because these tests were designed for relatively “hard” materials. If I were to suggest something, it would be to test the shear modulus and/or Young´s modulus of the material.
Do the losers that troll here really not have another site they could waste their worthless pathetic lives on? The same morons who cry about a Popsci article about political SCIENCE being too political are the ones who find some way to bash Obama no matter what the article is about. As Robot said, his degrees and accomplishments are well known and well documented. His college records are not public record because NO ONE'S ARE! He is an extremely intelligent man who has done more than trolls like gizmowiz or stompinstu could ever dream of. And now, while Obama is busy running the country rescuing us from yet another recession caused by Republicans, you idiots have nothing better to do than cry and moan because you believed all the blatant lies the GOP told you. You look so silly to us :)