Mpemba asked a visiting physics professor, Dr. Osborne, the same question. This professor replied that he did not know, but he would test the experiment. Dr. Osborne had a lab tech perform Mpemba's test. The lab tech reported that he had duplicated Mpemba's result, "But we'll keep on repeating the experiment until we get the right result."
Adam AP Mach 1, Rob Miller TRI36L, Celestron 8" Edge HD Hyperion 17mm, Celestron 40mm Plossl, TMB 7mm & 9mm WO 66, Lunt LS60/B1200 PT, CG-5 Clone STF-8300m Pro Package, Honis-Modified Canon XS, Un-modded T1i, SSAG, TSOAG9, SX Lodestar
Lackawanna Astronomical Society
Quote:I've tried this experiment many years ago, except that I boiled the one sample first and let cool just enough so it didn't break the container when I poured it in. Sample sizes were 16oz. My findings, the cold water froze first, and both had about the same rate of cooling. My conclusion, the whole thing was just an old fable.
Quote:I should think that materials cool to equilibrium with the environment at an asymptotic rate
Dan Orion XT8g If your dob isn't broke, fix it anyway. Don't tell me what I want to hear, tell me the truth.
"Scientists aren't perfect, just peer reviewed.""Eye of Sauron Observatory", featuring "Sauron's Other Eye", 16" dob, conical Royce mirror.
Quote:I've heard of it from the standpoint of someone claiming that their hot water pipes had frozen in severe cold while the cold water pipes remained clear. There are a lot of hidden variables that could be in play, but some of the stories are are nevertheless interesting.
--------------------- --------------------- "Nothing exists but atoms and empty space. Everything else is opinion." Titus Lucretius Carus 99-55 B.C.
Quote:Just a side note on the hot water pipes freezing first. Unless the hot water has been running recently the water inside is very likely the same temp as the water in the cold pipe.
Greg - Celestron SkyScout 90mm refractor & planetarium
Quote:There is a Wikipedia entry on the Mpemba effect, which is inconclusive.Here is my guess (which is rather vague). (1) There are difficult to control circumstances which produce a large uncertainty in the outcomes of the freezing experiments, (2) People tend to keep experimenting after any failures, because a failure isn't interesting, until they observe the effect. (1) and (2) result in an unusually high number of positive reports.
"After the Laws of Physics, everything else is opinion" -Neil deGrasse Tyson
Elmira-Corning Astronomical Society
Quote:We have an experiment, which no-one seems to be able to reproduce reliably, there is no theory to explain it and we can't even agree on the starting conditions...If this was called the E-Cat effect, would this thread be different? Would the members posting be as consistent? or supportive? or..I wonder...Have a great Christmas everyone (yes.. I'm on the other side of the date-line so this may be premature...)
Quote:I've done this experiment, but it was worded completely different. Does a tray of ice cubes freeze faster if you use hot water, than if you use cold. LOTS of folks will tell you it does.
We did a semi-controlled experiment. Water just boiled in one tray, and tap water in the tray beside it. Sure enough, the hot tray froze faster. BUT, then we continued, we let both trays thaw, and measured how much water came out of each after the freeze / thaw cycle. About 2/3 of the amount of water came from the hot tray.
Final conclusion, hot tray lost a lot of water to evaporation during the process, ended up with more surface area per unit volume because of it, and heat transfer out of the water is a function of surface area per unit volume. We got ice cubes faster, but, they were smaller. Shape of the ice cube tray plays a big role in this experiment, hunt around and you can find trays that work both ways.
FYI, back when we did this, experiment was accelerated slightly by using a freezer set to -42 degrees C, conditions that were available 'on the front porch' at the time. We had an argument during the experiment about 'is it cold outside', and came up with a simple way to answer that question, formally. Take a normal drinking glass, fill it half full of tap water. Put the glass out on the porch, wait 15 minutes. Tip over the glass. If no water runs out of the glass, it's cold. If water runs out of the glass, it's not cold out. Simple definition, with a proof that can be re-created using no fancy equipment.
Quote:Quote:I've heard of it from the standpoint of someone claiming that their hot water pipes had frozen in severe cold while the cold water pipes remained clear. There are a lot of hidden variables that could be in play, but some of the stories are are nevertheless interesting.
That's actually common. My friend does plumbing and it's frequently the hot pipes that burst as opposed to the cold. When I brought up the effect, he brought up the pipe issue.
Orion XT12i with Swayze-refigured primary & Protostar secondary
Televue NP101 refractor
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Universal Astronomics Deluxe Mounts
Quote:Some friends came over last night. We discussed the effect. My friend pointed out that he fills his ice cube trays with cold water and his wife hot. He says her cubes are too small and very brittle. His cubes are much harder and last longer. They didn't notice which froze first.
Quote:Minerals such as lime which are dissolved in water have a greater tendency to precipitate and accumulate in water heaters than in cold water pipes. Perhaps bits of those precipitates which are subsequently carried through the hot water pipes act as seeds for the crystallization of water ice. No?
I once had an old electric water heater whose tank was so full of precipitated "rocks" that it had little residual capacity for water. One had to shower quickly before the hot water gave way to cold.