Posted by Carlos on June 25, 1998 at 11:56:27:
In Reply to: three more posted by Walker on June 24, 1998 at 17:09:53:
Walker said:
It makes the claim: "Hot Water Freezes Faster than Cold!". Then goes into a detailed explanation of why this might be so. Perhaps under some peculiar circumstance this can happen but I have done this experiment at home. Take two ice trays and fill them with the same amount of water; one with hot water from the tap and one with cold. Put them both in the freezer. Try to put them in similar position with relation to the hottest and coldest spots in the freezer. This may be hard to determine so repeat the experiment switching the positions of the hot tray and the cold tray. In my experience, the cold water tray froze much faster than the hot water tray no matter their placement within the freezer.
So, faith isn't enough for you! :) I guess the correct statement would be: Under certain circumstances hot water can freeze faster than cold.
Another example I didn't like from this site...
Question: Does my bathtub drain differently depending on whether I live in the northern or
southern hemisphere?
Answer: No. There is a real effect, but it is far too small to be relevant when you pull the plug
in your bathtub.
No. it is not far too small. Again, I tried this experiment at home. Fill a bathtub with water. Stir it up. Let it drain. The vortex will spin the direction you stirred the water. Fill the bathtub again. Stir it up. This time let it sit for an hour. This will give the water time to lose the momentum you gave it by stirring and acquire the momentum of the spinning earth. Now let it drain. It always spins in the
direction of the earth regardless of which way you initially stirred it. This would be counterclockwise in the Northern Hemisphere and Clockwise in the southern.
The author of this article then goes into a useless mathematical discussion using the Rossby number, the Reynolds number, coriolis acceleration and so on. He says it cannot be demonstrated in the tub because of noise like vibrations and thermal currents in the tub.
This is nonsense. It is much simpler to describe this effect using conservation of angular momentum. It is easy to see that the net momentum of the water in your tub becomes apparent when forced through a small drain at the bottom.
I swear some of these theoretical physicists must never do practical experiments to back up their mathematical conclusions.
Interesting. As someone who just recently installed a new bathtub, I would argue that no tub is perfectly level (ok maybe just mine isn't), so that may have an effect on the observation.
Your last statement reminds me of a story Richard Feynman tells in his book Surely You're Joking, Mr, Feynman!. He was a visiting professor at a university in Brazil, and noticed that the physics students could give perfect textbook answers to all his questions, but were completely unable to translate those theories to real life situations. He then proceeded to ream out the whole Brazilian education process at an awards assembly. Great reading.