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Scientists Set New Coldest Temperature Record
one_who_uses_unix writes "Scientists recently successfully cooled a gas to the coldest temperature ever recorded ABC News reports. This is good news for proponents of basic research (read non-applied) which has seen shrinking budgets over the past few decades, and for overclockers hoping to squeeze 1 more cycle out of their CPUs."
You might look at it in a similar vein to reaching the speed of light. As your mass increases exponentially the closer you get to the speed of light, you'd have used up all the energy in the universe to accelerate long before you "get there".
You are not alone. This is not normal. None of this is normal.
The chances are that they'll never hit absolute zero
:)
You're more right than you know. According to current quantum mechanics (which has been tested inside and out), the Heizenberg uncertainty principle states that the more you know about the velocity of a partical, the less you can know about its position, etc. In other words, the uncertainties must multiply together to be greater than plank's constant divided by 2PI. As temperature approaches absolute zero, the uncertainty in momentum (which is a functional of thermal energy at that point, which is proportional to temperature) decreases. This causes the uncertainty in posiition to drastically increase.
Anyways at absolute zero this would mean the uncertainty in position would become infinite, in other words the position of the particle would be completely undefined. This is not possible so thus Absolute Zero is unattainable, even in theory.
Disclaimer: I'm still working on my degree, and I was in a hurry writing this. Please correct me if you can
So if you want to know about ultracold gasses, have a look at these links:
* Doppler cooling, or: how to use a laser not to hup stuff but to cool it: Nobel prize 1997
* the Bose-Einstein condensate: a weird state of matter that is formed by bosonic atoms at really ultralow temperature: Nobel prize 2001
* not that cool but still quite cool: suprafluid helium flowing against gravity: Nobel prize 1996
Is absolute zero really an unreachable limit
Yes, and there have been experiments that have demonstrated this is a way.
Quantum mecanics says that everything (including energy) comes in unit size packets. The unit size is called a Planck unit. You can only add energy to a particle or subtract energy from a particle a full Planck at a time. Now here's the catch - if you look at how much energy a particle has it always has a "point five" on the end. A particle can have 1.5 Plancks of energy, 8.5 Plancks of energy, or a billion and a half Plancks of energy. As you try to take energy out eventually you get down to 0.5 Planks of energy and you are stuck. You can only take out a full Planck at a time.
I'll explain one of the experiments they did that demonstrates this. Imagine you lie on the ground to the left of a flat table and randomly toss ping-pong balls up at it. The ping-pong balls have random energy. Any ping-pong ball you throw too slowly will fall back down without reaching the table top, it will fall back down and stay on the left. Any ping-pong ball you throw fast will reach the table top and bounce along and eventually fall off the right side. If you throw it real high it will make big bounces along the table-top and it will come down the right side falling really fast. Throw it slower and it will make little bounces. If you throw ping-pong ball *just barely* fast enough to reach the edge of the table top it will roll across the table top with zero up/down bounce and it will come off the right edge with zero falling speed. (It may be moving to the right very fast, but we are just looking at the up/down speed)
Scientist did something like this, but instead of big fat ping-pong balls they used neutrons. They "tossed" them randomly up at the edge of a flat plate and the neutrons bounced along and fell off the right edge. They then studied the neutrons falling off the right and looked at their minimum speed:
The researchers report seeing a minimum (quantum) energy of 1.4 picoelectron volts (1.4 x 10-12 eV), which corresponds to a vertical velocity of 1.7 cm/sec.
NONE of the neutrons came off the right edge with zero up/down speed. They were ALL bounced along and came off going atleast 1.7 cm per second.
In scientific terms gravity is really really weak. Almost infinitly weaker than the other forces. Since gravity is so weak and a single neutron is so tiny they "magnify" the size of a single a Planck. One Planck unit of gravitational energy for a single neutron on Earth is about 3.4 cm per second. That means you can only change the up/down speed of a neutron by 3.4 cm/sec at a time. If a neutron is going up at 5.1 cm/sec gravity will pull down and the speed will JUMP by 3.4 cm/sec. It will skip from an up speed of 5.1 to an up speed of 1.7 (5.1 - 3.4 = 1.7) Then gravity keeps pulling down and you get another 3.4 jump in speed. It will skil from UP 1.7 cm/sec to going DOWN 1.7 cm/sec. (1.7 - 3.4 = negative 1.7)
The neutron is always going up or down by at least 1.7 cm per second. It "teleports" right past zero without ever being zero.
We never notice this in the "real world" because even the tinyest spec of dust is made of many millions of neutrons, half of them going up at hundreds of miles per hour and half going down at hundreds of miles per hour. They constantly bounce off of each other reversing direction a million times per second.
That's why you can never hit absolute zero, quantum mechanics says the energy always ends up least one-half of a step off of zero.
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