davis@hplabs.UUCP (Jim Davis) (08/16/83)
It seemed to be time to throw a few more "facts" into the confusion over the freezing of water. First, arguments that state that hot water freezes first because it loses heat faster through evaporation are false. All this does is cause the hot water to become cold water, which then acts like cold water and cools slowly. However, under some circumstances hot water does freeze faster than cold. When hot water is put into the freezer convection currents are set up which cause the hot water to cool rapidly. This occurs because of the greater thermal gradient. These convection currents do not die out as the water cools. Hence, the water continues to cool rapidly. This phenomenon depends upon the shape of the container. Some ice cube trays fit the bill. There is a better reason to freeze hot water. The solubility of many gasses in water decreases with increasing temperature. If ice cubes are made from cold water they will not be clear, while those made from hot water are. -- Jim Davis (James W Davis) ...!ucbvax!hplabs!davis davis.HP-Labs@UDel-Relay ----------------------------------------------------------------
jj@rabbit.UUCP (08/17/83)
Well, what I was told by an old Englishman who was a physicist and a tea lover was that the LACK of dissolved gasses made the tea taste flat. I note that someone on the net commented about minerals and distilled water. Again, since distilled water has no minerals, it can't be a mineral taste. Since it has no dissolved gases, it CAN taste flat because of that. Try pouring it back and forth between two glasses about 20 times, maximizing the in-glass splashing. Makes a big difference.
kfl@5941ux.UUCP (08/17/83)
For the record, there was an article in Scientific American several years ago (I think in 1977 or 1978), that explained why very hot coffee cooled to room temperature faster than moderately hot coffee (I forget the 2 temperatures, but the idea is that the hotter one reached room temp. first). A very reasonable thermodynamic study was presented in the article and the conclusion was that the impurities in the water (i.e. the coffee) produced different crystal structures when cooling in different manners, and the different crystals had different specific heats. The same arguement could probably apply to impure tap water in the freezer. P.S. The first and last time I read this article was in 1977 or 1978, so I may have messed up some of the facts. Check the article for yourself, if you care. Ken Lee 5941ux!kfl
rh@mit-eddie.UUCP (Randy Haskins) (08/22/83)
Let's talk instead of which is the best way for toilet paper to come off of the roll. This was cleared up in Ann Landers some time ago, but I think we need to clear it up on the net also. -- Randwulf (Randy Haskins); Path= genrad!mit-eddie!rh or... rh@mit-ee (via mit-mc)
davis@hplabs.UUCP (Jim Davis) (11/16/83)
The original article: > All living people (or at least ~99% of them) have a single common female > ancestor on their purely maternal line. In other words, tracing back to > one's mother's mother's mother's ... mother will bring everyone back to > a single individual woman. She is estimated to have lived between > 50,000 and 500,000 years ago. Piet Beertema writes: > Fine! But please explain: how comes the oldest fossil > hominid skull is about 2,000,000 years old! Must have been > only males then living at that time.... I (Jim Davis) write: Piet's comment is simply ridiculous. Simply because all people are (if they are) descendants of a single individual 50,000 years ago does not imply that this individual did not have parents. I am sure that Piet will not dispute that there are no surviving members of Neanderthal Man or Homo Erectus; they are all dead now. Does the fact that they are dead imply that they never lived (the conclusion of applying Piet's logic to this problem). Michael Ward writes: > This seems to imply one of the following: > - There were no hominids before ~50K years ago. > - All hominids except one family were somehow wiped out in that time. > - Our common ancestral tribe went a-raiding and delivered their > excess women throughout the world. > - Our common ancestral tribe slaughtered all other hominids in the > world. > Since the first three options seem unlikely for one reason or another, > and the one that is left is very disconcerting to me, I would appreciate > it if someone would think up a more pleasant explanation of this. I (Jim Davis) write: It might be appropriate to discuss a similar example occuring during our own time period. There is a human cell culture called HeLa (named after its now desceased contributor). At one time there were many other human cell cultures from different donors. Recent work (I'm sorry not to give the researcher's name, but I'm forgetful) has shown that most of the currently existing cell cultures are now HeLa cultures. This does not mean that there never were any other cell cultures, nor does it mean that there were no cells cultures before HeLa (though I am not sure that there were). All that this means is that over time the HeLa strain "took over" or "crowded out" the other strains. If the slaughter that Michael Ward refers to took place over hundreds of generations, and was not necessarily caused by any form of direct conforntation, is it still as disconcerting? After all, Neanderthal Man or Homo Erectus were certainly killed off via this same "slaughter" (quoted because there was no necessity for any direct conflict). I do not find it far fetched that humanity may have shared a common female ancestor as recently as 50,000 years ago. I do find the conclusions that others draw to be quite strange. Please be sure that flames or counter replies make it to net.misc, I do not subscribe regularly to any of the other groups containing this discussion. -- Jim Davis (James W Davis) ...!ucbvax!hplabs!davis davis.HP-Labs@Rand-Relay ----------------------------------------------------------------