2005 Scientific Highlights 113
Nomad37 writes "The Sydney Morning Herald has a great wrap-up of the great moments in 2005 for science. The story covers everything from evolution to space exploration, the role of genetics in brain disorder to nuclear fusion. The story provides a neat overview for those of us who haven't been checking Slashdot regularly enough!"
MOD PARENT DOWN. (Score:3, Informative)
Re:Why check? (Score:4, Informative)
Yes, since Zonk posted the same story yesterday. That referenced the BBC, this the SMH. A moment's searching brings you to the original story at the American Association for the Advancement of Science's Science magazine. [sciencemag.org]
Re: Funny...explain this... (Score:3, Informative)
Yeah, I thought he was trolling too. Then I looked at some of his (the GP) previous posts. Not so much.
To the GP, I am not disrespecting your faith, however
Most simplisticly, the reason your ferromagnet remains attached to the fridge instead of falling is because the potential electromotive force generated by the dipoles in the magnet and the fridge is greater than the potential gravitional force between the magnet and the earth. Note the word potential in both clauses. Until the magnet actually moves, no work has been done and thus no energy has been expended. It does not "cost" anything for the magnet to remain attached. If the magnet were weak enough that potential gravity could overrule it, then there would be a cost (for as long as the magnet continued to change inertially), to both the earth's inertia/angular momentum and the related magnetic domains.
I know it must seem magical, but its really just a simple case of the magnet being in the lowest possible rest-state (energy-wise) for that configuration.
You'll notice that it's not called the "Theory of Thermodynamics".
Re: Funny...explain this... (Score:3, Informative)
Sorta, depending on you how you look at friction. Any time the layperson's concept of "friction" is involved, it usually just means gravity (after all, in a zero-g environment, will two objects directly touching each other stay that way if a force is applied perpendicularly to one of them?)
In this case though, that's not really the type of "friction" in play. Like gravity, electromagnetism follows the inverse square law. And, in your example of a magnet suspended vertically from a horizontal surface, the field effect will rapidly fall off as the magnet's distance from the ferrite increases. In fact, because there is no potential force, other than that created by the magnet, which would balance gravitational potential, any increase in distance between the magnet and the ferrite will cause a drop in magnetomotive effect ("potential electromotive force") as well as true current-potential electromotive force. Thus the only "energy hill" is momentary and equal to that of the magnetomotive effect itself. Like balancing two identically weighted people on a a teeter-totter, as soon as you apply the slighest momentary force to one side, they are on an unstoppable (w/out addl force elsewhere) downward journey.
Not so with a horizontal ferromagnet on a vertical surface. Assuming right angles to the center of gravity, the magnet's distance from the ferrite never increases when gravitional potential becomes true force. The inverse square law has no effect. Now, the gravitional potential must continously meet or beat the non-varying (or very slightly varying) electromotive potential. Because some of the gravitional potential is now actual force (i.e. work is being done), it cannot continously stay "over the hill" as would be required, although if the magnet is weak enough and the two are toe-to-toe, gravity may very well continually "win" but with only enough force to induce minor inertial change and the rest being "consumed" by balancing the non-varying magnetomotive (i.e. the magnet slowly slides down the fridge). Obviously, such a precarious balancing act requires very little change on either side's potential to start a runaway resulting in the magnet either stopping or falling off into inverse-square-law world. This is the facination people have with so-called "permanent magnets"; that it is so easily possible to directly observe and manipulate the equilibrium point between two potentials.
The main cause of magnetism seeming so mysterious to many is that our instinctual inertial and gravitional perception is not what it seems at first glance. We think, instinctively, that we "feel" gravity, but what we're really feeling is a combination of fluid orientation and inertial potential. In other words, rather than perceiving the actual force performing work, we're perceiving potential energy offset by 1g perpendicular to our orientation. When someone "feels" the pull of a magnet, what they're really feeling is the potential for their hand to experience inertial change. If they allow their hand to move, they will mostly cease to notice the real force (they would notice the acceleration, but it's minor in the case of household magnets). Because one must always balance potential in order to prevent it from asserting the lowest possible energy state (i.e. expending itself), people mistakingly perceive this as work-energy when in reality they could balance it equally well with some external non-moving brace which prevented joint movement.
I guess it comes down to this: Effort as "not-work" means there is no real force involved, as you can't actually use it to do a damn thing.