NKVD
Cossack
he's not alone believing it. 3 doctorates in physics found the same conclusions...
Science questions not worth a thread I: I'm a moron!
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he's not alone believing it. 3 doctorates in physics found the same conclusions...
Since my total lack of French language skills prevent me from getting the details in that article I searched for the original paper:
http://arxiv.org/abs/1001.0785
And here is a rebuttal:
http://arxiv.org/abs/1002.2668
Here the main argument is, that although the math works more or less out, Verlinde has confused cause and effect. Work done by gravity changes the entropy, which is not very surprising, as thermodynamics require this. But that does not mean, that gravity is caused by entropy gradients as these gradients are only there because of gravity.
http://arxiv.org/abs/1001.0785
And here is a rebuttal:
http://arxiv.org/abs/1002.2668
Here the main argument is, that although the math works more or less out, Verlinde has confused cause and effect. Work done by gravity changes the entropy, which is not very surprising, as thermodynamics require this. But that does not mean, that gravity is caused by entropy gradients as these gradients are only there because of gravity.
I've seen a colloquium by Erik Verlinde at my university, and he didn't look like a nutjob to me.
The math works out (even in special relativity, I believe), and it can provide a simple explanation for gravity. Much simpler than, say, string theory. Of course much work is needed to falsify this theory of to find evidence for it. It'll be interesting to see if the theory can make predictions other theories can't make.
No, he claims that gravity is just an emergent phenomena. It's not confusion, it's the entire point of his article.
The math works out (even in special relativity, I believe), and it can provide a simple explanation for gravity. Much simpler than, say, string theory. Of course much work is needed to falsify this theory of to find evidence for it. It'll be interesting to see if the theory can make predictions other theories can't make.
Hey, he is a string theorist, that's already pretty nutty
No, he doesn't seem to be a crackpot. He has some unconventional ideas, but we wouldn't get anywhere if we threw all unconventional ideas away. He only gets into crackpot territory if he fails to see the obvious and not so obvious flaws pointed out by others.
If you want to argue, address the points of the Gao paper I tried to summarize, instead of just repeating Verlinde's claims. I think they're strong points, but then I don't care much about theoretical talk, unless they can link their calculations to real physics.
Edit:
Now that I have thought a bit more about it: His calculations make use of the temperature. But how does this work in cases, where you cannot properly define a temperature? We do see gravity in those cases, so how does he explain gravity by thermodynamics for a system where the assumptions of thermodynamics don't hold?
I can't answer the deeper questions about the theory, I'll leave that to mister Verlinde (and Gao and others). I don't know if his theories are true (I'm a bit sceptical about them, but their conclusions are sufficiently interesting to warrant research into the subject), what I do know is that he's not some random nut job like Lord Olleus was suggesting.
PlutonianEmpire
King of the Plutonian Empire
Will we see Betelgeuse go supernova within our lifetimes?
Olleus
Deity
Probably not. I mean, its expected to go supernova very soon, but that means a couple of millennia.
ParadigmShifter
Random Nonsense Generator
It's also 640 light years away from us, so unless it has already gone supernova we won't know in our lifetimes 
OKAY, I've taken a couple of measurements.
2 days in the bottom of the freezer: -20 C*
2 days in the basket in the top of the freezer: -14 C
The thermometer I used is very similar to this one, and the freezer is this one, the compressor is at the bottom of the unit.
*The dial on my thermometer only goes down to -20C, but the needle was reading colder than that. My best guess is that the temp was, at warmest, -25C, and more probably -30C. In any case, and despite this being a cheap thermometer, the fact remains that it's quite clearly a bit colder at the bottom than the top.
NKVD
Cossack
wow...i'm impressed you took the time...in the same idea what is responsible for the warm water to freeze faster than cold water...or is it just a false idea?
ParadigmShifter
Random Nonsense Generator
Isn't warm air lighter than cold air so it rises?
I'm pretty sure the warm water freezing quicker/cold water boiling faster thing is total bollocks as well.
I'm pretty sure the warm water freezing quicker/cold water boiling faster thing is total bollocks as well.
Yeah, I've heard the warm water freezing fast thing before, as well as 'cold water boils faster than warm water'. Both are completely false.
However!!....
I *think* that freezing hot water will yield clearer ice cubes than freezing cold water. But I might be confusing it with filtered or distilled water.
EDIT:
@PS: Yes, colder air is denser so the warmer air, even though it's -14C, will come to rest in a layer above the cooler air.
However!!....
I *think* that freezing hot water will yield clearer ice cubes than freezing cold water. But I might be confusing it with filtered or distilled water.
EDIT:
@PS: Yes, colder air is denser so the warmer air, even though it's -14C, will come to rest in a layer above the cooler air.
ParadigmShifter
Random Nonsense Generator
Freezing boiled water results in clear icecubes, I think tiny air bubbles can form in water (or maybe air is dissolved? not much of a physicist/chemist) and boiling gets rid of theses, so the ice is clear.
Samez
Emperor
Boiling the water might also result in a lower calcium carbonate content (as it will settle on the cooking pot). Reducing the solved gas in the water might also improve the color of the ice cubes.
For "easier" freezing you would have to increase the amounts of impurities (gas bubbles can also be impurities) so they can work as crystallization seeds. If there are very little / no impurities the supercooling of the liquid will be increased IE the temperature you can go sub zero (°C) without the water becoming ice. If you have supercooled water in a bottle and add some pressure (or any type of shock-wave), all the water will crystallize immediately.
For "easier" freezing you would have to increase the amounts of impurities (gas bubbles can also be impurities) so they can work as crystallization seeds. If there are very little / no impurities the supercooling of the liquid will be increased IE the temperature you can go sub zero (°C) without the water becoming ice. If you have supercooled water in a bottle and add some pressure (or any type of shock-wave), all the water will crystallize immediately.
I heard another reason warm water freezes faster is that a lot of it evaporates and thus there is less that needs to freeze.
Why does the meniscus in my measuring cup point up, rather than down?
Samez
Emperor
It's a matter of surface tension and wettability.
...still doesn't answer my question, though - unless I'm missing something. According to those models, there's no reason why the meniscus should be higher than the rest of the surface of the water rather than lower. in other words, a negative Theta instead of a positive Theta. My initial guess is that Gravity (weak, though it is) is the deciding factor. If that's the case, then I would expect there to be corroborating evidence from low-G space experiments.
Perhaps I'll hunt around for this some day. Not tonight, though
madviking
north american scum
Is this for water?
I know that glycerin has an upward meniscus.
I know that glycerin has an upward meniscus.
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