The Mpemba effect

[terry5732]

[quote="scott"]I find this fascinating. If we don't even understand how water freezes, how can we say we understand gravity?


[quote]Can hot water freeze faster than cold water?

Hot water cannot freeze, it must be cold.

[ovyyus]

Jim, I don't think Byer's theories qualify as experimental evidence. It is interesting though.

[jim_mich]

Bill,

You asked for "An example of an oservation or experiment which runs counter to current scientific understanding." And you suggested that might be "the basis upon which to build a hypothesis that our understanding of the effects of gravity is incomplete." One example of an observetion is the non-linear distribute of 'currently accepted' planet densities. Byer also gives examples of nuclear sheilding of his Prime Background Radiation. He has many pages of well writen coeherent arguments showing statistical reasons supporting his concept spanning all the way from gravity on a cosmic scale down to the atomic level.

What I suggested was that past experiments be looked at from the perspective of Byers theories to see if they corollate.

During a solar eclipse pendulums swing faster. From http://home.netcom.com/~sbyers11/grav11d.htm ...

This is a review,... and quote,... and graph of the Saxl and Allen gravity research work demonstrating and measuring the earth's surface gravity perturbations that occur during a solar eclipse. This section is to present the view that the gravity perturbations are caused by planetary gravitational shielding as described with this radiation and shadowing model of gravity. The radiation and shadowing model clearly predicts an increase in gravity within the umbra and penumbra of the eclipse shadow.

The Saxl and Allen work, Phy. Rev. D, 3:4: pg. 823-825 indicates a 5% increase in local surface gravity during the eclipse and states that this measured value is One Hundred Thousand Times (1X10^5) greater than the expected change in gravity computed according to the older theories. The paper also states: "Results of this order of magnitude have been consistently observed in Harvard over a period of 17 years."
It should be noted that older classical theories of gravity do not predict any gravitational step perturbation whatsoever in conjunction with any type of eclipse. With a radiation and shadowing model of gravity the cause of the step increase, as seen in this Saxl and Allen work, is readily evident from the shadowing and planetary geometry.

Abstract from the Saxl and Allen paper:

"1970 Solar Eclipse as "Seen" by a Torsion Pendulum"
"During the solar eclipse of 7 March 1970, readings were taken and recorded electronically of the times required for the torsion pendulum to rotate through a given fixed part of its path, involving both clockwise and counterclockwise motions, on its first swing from rest. Significant variations in these times were observed during the course of the eclipse as well as in the hours just preceding and just following the eclipse itself. Between the onset of the eclipse and its midpoint there is a steady increase in the observed times. After the midpoint the times decrease suddenly and level off promptly to values considerably greater those observed before the eclipse. Furthermore, before the eclipse there is a periodic variation in these times. This strange periodicity was essentially repeated two weeks later at the same hours, though the actual values were somewhat greater than the earlier ones. These increases in actual values exceed by a factor of 10^5 those that can be explained by the attraction of the moon due to its change in position relative to the Sun and Earth. All this leads to the conclusion that classical gravitational theory needs to be modified to interpret these experimental facts".

This shows that if we look for experimental evidence that our current understanding of the effects of gravity is incomplete, the evidence is available!


When Byers talks of 'this model' he means his theory. One last quote from http://home.netcom.com/~sbyers11/grav11E.htm ...

The source or cause of the prime radiation is not considered in this model. In characterizing the features of the prime radiation, it is important to note that it cannot be referred to as ElectroMagnetic radiant energy, even though it may be viewed as "potential",.... potential-energy. In a free space area of isotropic flow the Prime radiation is only radiation. In a shadowed space with unbalanced flow the Prime radiation becomes potential energy, as used in the terms gravitational potential or voltage potential. When the unbalanced flow is applied as a force in falling and combating the retarding inertial force during acceleration, it manifests as kinetic energy of the object. The unbalanced flow can only occur for the gravitational force system when an object (planet) is in the vicinity to sink or shadow the flow from the planet's direction. This passive system of unbalancing is the only method presently known by our science. When an object such as a boulder is raised to a height, it is said that the energy expended to raise the boulder is stored as potential energy of position within the boulder. In this model of radiation and shadowing the energy and force arises from the unbalanced flow of radiation through the boulder. The force and energy expenditure by the radiant flow is essentially the same whether the boulder is falling or not. Thus this model predicts that an infinite source of energy is available from Prime radiation at an essentially infinite rate.

Note: The red emphasis is mine.

[ovyyus]

Yes, thank you Jim. Byer's does make some interesting observations and he certainly seems to draw some fascinating theoretical conclusions from them.

The Saxl and Allen eclipse torsion pendulum experiments are also interesting and I remember reading their paper ages ago. I wonder if their experiments have been repeated by others who have arrived at similar inexplicable results?

[coylo]

I think the Mpemba effect may be down to entropy.
The warmer glass has more energy therefore it's (energy flow/loss is) able to spread/invade a larger surface area of the surrounding environment, than the colder glass, thus it cools down faster.

Systems with more energy tend to lose/waste energy a lot easier than those with less....seems to usually be the case.

Just my two cents.....I'm still learning!

[Fletcher]

I think you are right Coylo. It cools down faster because of the greater differential between the warm water temperature, the atmosphere (which is a heat sink itself) & the cooling agent working at a certain capacity.

Imo there would be very few examples where the warmer water froze earlier than a colder water, all else being equal.

Cooling down faster is not the same a freezing earlier.

[coylo]

Systems with more energy tend to lose/waste energy a lot easier than those with less....seems to usually be the case.

Oh, and it does so at a faster rate.

Thanks Fletch....I think I may be right as well!

[Oxygon]

I read most of the thread posts and I thought... imo... with regard to the "Mpemba Effect"

Wouldn't the hotter water cool faster becuase of the heat energy being sucked up and off by evaporated water molecules...?

kind of like a mousture based "evaporation heat sink?"

-- Coylo beat me to it...

[Fletcher]

Sounds like a good one for "Myth Busters".

[jim_mich]

I always heard that this effect was caused because warmer ice cube trays would melt down through the ice layer on the coils in the ice compartment of the pre frost free era refrigerators and thus come in direct contact with the metal coils rather than sitting on top of an ice/frost layer that insulated and limited rapid heat flow out of the water into the coils.

[racer270]

..............my 2 cents......

i can take 6 gallons of racing fuel , on a hot summer day..@..say 100*fa.

put it in a sub-zero freezer .....over night......

and it terns it into just over 5 gallons of racing fuel.....@.....0*fa.

the fuel gets denser as the temp...... drops ......

so cold water is also denser , then hot water........

ie: .....20% more by volume to to freeze .........from 100* to 0*

....I can put 25gl. of gas .......in a 22gl. TANK........LOL

there is more free space between the "hot" water molecules. and thus les of it.... in the same volume.........

so the heat can be extracted , faster from hot water ......than it can from cold water.... but you getting :, "thin ice cubs".......

ps. start shooting.......it down.........:)

[Vic Hays]

My understanding is that warm water freezes quicker than cooler water because less oxygen is dissolved in it.

Hot water pipes freeze first.

[terry5732]

Water EXPANDS before freezing

[DrWhat]

Ok, what about if I just made a hot cup of coffee. It's just been poured into my mug.

The doorbell rings. When I come back after talking to the neighbour for five or more minutes, and I add the cool milk, will the cofee now be colder than if I had added the milk before talking to the neighbour, all things being equal?

I don't know the answer, but I've been worried about this for years!!! :-)

If you discover the answer, have yourself a cuppa!

[LustInBlack]

A really bad tasting coffee..


I'll ask you this, does coffee taste good anyway?!