Absolute zero has been considered the lowest temperature possible since the 1800s when Lord Kelvin developed his temperature scale.
Now physicists working with a quantum gas believe they have developed a technique that allows the gas to reach a temperature lower than absolute zero.
Zero degrees Kelvin (negative 459.67 degrees F) occurs when atoms lose nearly all of their kinetic energy. Their state of immobility is called absolute zero. As the temperature is increased, the atoms move with more kinetic energy.
Physicist Ulrich Schneider from the Ludwig Maximilian University in Munich, Germany, and some of his colleagues reached sub-absolute-zero temperatures working in the laboratory with a quantum gas made up of potassium atoms, according to nature.com.
They reached negative Kelvin temperatures by arranging individual atoms in a lattice arrangement using magnets and lasers. In this arrangement, the atoms repel each other at temperatures above absolute zero. This keeps the arrangement stable.
This diagram of the different states of an atom was created by AccuWeather Graphic Artist Al Blasko.
Next, they adjusted the magnetic field to cause the atoms to attract each other. If the temperature was still positive, the atoms would become unstable. To account for this, the physicists also adjusted the trapping laser field to be more energetically favorable for the atoms to remain still.
The result of the experiment is a transition of the gas from just above absolute zero to a few billionths of a Kelvin below absolute zero.
Sub-zero quantum gas mimics dark energy found in the universe and Schneider suggests his experiment with absolute zero may be of interest to cosmologists.
Following a dip in temperature during the middle of the week, summerlike warmth will rebound across much of the Northeast by this weekend.
Daily episodes of severe thunderstorms and flooding downpours will impact the Plains this week, possibly lingering into the weekend.
The central and southern Plains will continue to be pummeled by strong storms for the next several days, but the most potent severe weather threat is likely to be during the Mother's Day weekend.
Wind, seas and surf will build in advance of what is likely to become the first tropical system of 2015 along the southeastern Atlantic coast of the United States late this week.
Summer will lack any long-lasting heat waves across northwestern Europe, while parts of southern and eastern Europe will feel the heat.
A storm will bring a wide range of weather to the West into this weekend as it drops across California and turns eastward toward the Rockies and High Plains.
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Green Bay, WI (1998)
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Lingle, WI (2000)
4.5" diameter hail - there was also a tornado in the area.