- Alexandra Martins
- BBC News World
What is the lowest temperature you can imagine? The lowest recorded level on Earth is -89.2℃ in Antarctica. In some places on the moon it can go as low as -200 degrees Celsius.
But an international team of scientists has achieved an even lower temperature, the lowest ever measured in the universe.
Researchers from Rice University in the United States and Kyoto University in Japan obtained temperature in the laboratory 3 billion times cooler than interstellar space.
Scientists used lasers to cool atoms to a temperature of just one billionth of a degree above −273.15 ℃, which is absolute zero on the Kelvin scale. This is the temperature at which all motion of the atoms comes to a complete stop.
The experiment is not only a great achievement at the laboratory level. also “It opens the doors to the development of new materials with unimaginable propertiesFrancisco José Torcal Milla, a professor in the Department of Applied Physics at the University of Zaragoza, told BBC Mundo.
At temperatures close to absolute zero, helium becomes, for example, a “super liquid”, a state characterized by the complete absence of viscosity. This means that it can pass through walls and any type of material, porous or not, and climb up the walls of the containers it contains.”
One of the authors of the experiment and study it describes is Mexican atomic physicist Eduardo Ibarra García Padilla, who after earning his Ph.D. at Rice University is now a postdoctoral researcher at UC Davis.
Ibarra told BBC Mundo that there are phases of matter that can only be reached at low temperatures.
Reaching these temperatures and those phases will allow us to better understand problems in physics such as “superconductivity in copper oxides, which will have important technological applications.”
How was the experiment conducted?
Researchers in the United States and Japan lowered the temperature to extreme levels with atoms of ytterbium, a rare earth chemical element in the periodic table with the symbol Yb.
To achieve this, useLaser cooling and evaporative cooling technologiesIbarra explained.
Evaporative cooling It’s like you have a very hot soup. What one does is blow into the soup; By doing this, one removes the hottest particles and in this way cools the soup,” said the Mexican physicist.
“The experiments do the same thing: one plays with the light trap where the atoms are trapped and the other removes the hotter atoms and thus cools the system.”
What are these light traps?
Torcal-Milla, who wrote a Article – Commodity Revealing the experience, he told BBC Mundo the procedure is shrouded in the highest technology.
“It begins with sublimation (conversion directly from a solid to a gas without going through the liquid state) of ytterbium atoms. This procedure is typically performed by shining a high-powered laser onto a block of solid ytterbium, causing it to vaporize a small amount of the same.”
“Once the dilute gas is obtained, it is kept in a chamber where an extreme vacuum is created and The atoms are trapped by optical traps, which are like a kind of ring made of light“.
“Then they are hit by lasers from different directions. When the laser photons interact with the gas atoms, which are moving, they slow down their speed, lowering their average speed and, as a result, their temperature.”
Where was the experiment conducted?
The laboratory in which the standard temperature was reached is located at Kyoto University. The group led by Yoshiro Takahashi and Shintaro Tai was working there.
“We provide the theoretical and numerical part of the study, allowing us to extract the temperatures at which the experiments were conducted,” Ibarra said.
One of the best known sites for low temperature tests is Cold Atom Laboratory, CAL, on the International Space Station.
CAL has the advantage of zero gravity, although Ibarra noted that zero gravity was not necessary for studies conducted on this occasion.
Torcal Milla believes that it would be interesting to conduct these experiments aboard the International Space Station, “because despite the fact that the gravitational interaction to which individual atoms are subjected to due to the Earth is minimal, it becomes more important as the rest of the parts of the interactions are.””.
How does the behavior of matter change?
“In nature there are two types of particles, bosons (such as photons in a laser) and fermions (such as electrons in a solid), which exhibit different behaviors at very low temperatures,” Ibarra explained.
The scientists used an isotope of ytterbium called 173Yb, which is a fermion.
At low temperatures as in the experiment, the substance behaves in an unusual way.
Torcal-Milla explained that in the case of bosons, they all drop to a lower energy state called the indistinguishable fundamental state, called the Bose-Einstein condenser.
On the other hand, if fermions (the fundamental particles that make up matter) then become what is known as a Fermi gas or liquid, able to go up walls or even pass through them.
The best known examples of strange behavior at low temperatures Superconductivity and Superfluidity. Superconductivity occurs when a material is able to conduct electricity without resistance.
On the other hand, superfluidity consists of the total loss of viscosity of the material. This state can be achieved by Fermi fluid at very low temperatures, very close to absolute zero.
At these temperatures, almost everything freezes, except for some isotopes of helium, which become superfluid. In this case, the liquid is able to climb up the walls of the container containing it.
What future applications could this type of experience have?
Ibarra told BBC Mundo that when we reach lower temperatures, different strange phases of matter will appear. They can have very different magnetic or transmission properties than other materials.
In the case of future superconductivity of copper oxides, for example, the possible application according to the Mexican expert is a suggestion Using superconductors to lift trains.
“An example would be ferromagnetic trains. But I think it will probably be useful for other applications because it means being able to have an electric current without losses.”
For Torcal-Milla, “Every experience that advances knowledge is important, no matter how small a progression. If we could tell our grandparents that with a small device in my pocket, I could access whatever information I needed, speak as well, and even see anyone in my pocket. Opposites, we will be treated as madmen or charlatans.”
“Some of the discoveries will have to wait to be applied and perhaps that is the case, but There is no doubt that it will reveal to us new physics that we cannot even expectThe Spanish expert added to BBC Mundo.
“Who knows whether studying these systems can reveal new physics that will lead us to the final theory that unites all fundamental forces, or reveal the properties of matter at microscopic levels, which are still unknown.”
Now you can receive notifications from BBC World. Download and activate the new version of our app so you don’t miss our best content.
Subtly charming zombie buff. Amateur analyst. Proud tvaholic. Beer fanatic. Web expert. Evil troublemaker. Passionate internet maven. Gamer. Food evangelist.