Scientists who have reached the lowest temperature ever recorded in the universe

What is the lowest temperature you can imagine? The lowest number recorded on Earth was -89.2℃, in Antarctica. In some places on the Moon, this measurement reaches -200 ℃.

But an international team of scientists arrived at a much lower rate and reached the lowest temperature ever measured in the universe.

Researchers at Rice University, in the United States, and Kyoto University, in Japan, obtained a temperature 3 billion times colder in the laboratory than has been measured in interstellar space.

The group reached a temperature that was within a billionth of a degree of reaching absolute zero on the Kelvin scale, or -273.15℃.

Scientists used lasers to cool atoms of a chemical element known as ytterbium.

The experiment is not just a great achievement made on the lab bench. It also “opens the door to the development of new materials with unimaginable properties”, says Francisco José Torcal-Milla, professor in the Department of Applied Physics at the University of Zaragoza in Spain.

At temperatures close to absolute zero, helium, for example, “becomes superfluid, a state characterized by the total absence of viscosity. This means that this element can pass through walls or any type of material, porous or not, and climb up the sides of the containers that contain it”, explained the researcher.

One of the authors of the experiment and the study that describes it is the Mexican atomic physicist Eduardo Ibarra García Padilla who, after completing his doctorate at Rice University, is now a postdoctoral researcher at the University of California at Davis, also in the USA.

Ibarra says that there are states of matter that are only accessible at lower temperatures.

And reaching these temperatures and states 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 carried out?

Researchers from the United States and Japan have reduced the temperature of ytterbium atoms to extreme levels. This is one of the chemical elements found in the periodic table.

To do this, they used “evaporative and laser cooling techniques,” explained Ibarra.

“Evaporative cooling is like when you have a very hot soup. What you do is blow the soup. With that, you remove the hottest particles”, he compares.

“The experiments did something similar: in the first, we used a light trap where the atoms are trapped; in the second, we removed the hottest atoms to cool the system.”

But what are these light traps?

Torcal-Milla says the procedure is performed with the latest technology.

“It all starts with the sublimation (direct conversion from a solid to a gaseous state, without passing through the liquid) of the ytterbium atoms. This procedure is usually carried out by a high power laser on a solid block of this element, making a small amount of the gas to evaporate.”

“Once the diluted gas is obtained, it is kept in a chamber where an extreme vacuum has been created and the atoms are trapped by optical traps, which are like a kind of ‘lasso’ made of light.”

“Then these gaseous molecules are hit by laser beams that come from various directions. When the laser photons interact with the moving gas atoms, there is a deceleration, which decreases the average speed and, consequently, their temperature.”

Where the experiment was carried out

The laboratory where the record temperature was reached is located at Kyoto University. The work was led by scientists Yoshiro Takahashi and Shintaro Taie.

“We provide the theoretical and numerical part of the study, which allows us to measure the temperatures at which the experiments were carried out”, says Ibarra.

One of the best-known locations for low-temperature testing is the Cold Atom Laboratory (CAL), located on the International Space Station.

CAL has the advantage of working in zero gravity, although Ibarra points out that this was not necessary for the studies carried out this time around.

Torcal-Milla, on the other hand, believes that it would be interesting to carry out these experiments aboard the International Space Station, because, “although the gravitational interaction suffered by individual atoms in relation to the Earth is small, it becomes more important the smaller the interactions with the rest are.” of the planet”.

How does the behavior of matter change?

Ibarra explained that in nature, “there are two types of particles — bosons (like photons in a laser) and fermions (like electrons in a solid) — that behave differently at very low temperatures.”

In the latest experiment, the scientists used an isotope of ytterbium called 173Yb, which is a fermion.

At temperatures as low as those reached, matter behaves in an extraordinary way.

Torcal-Milla explains that in the case of bosons, they all fall to a minimum energy state in which they become indistinguishable. The phenomenon is known as Bose-Einstein condensate.

On the other hand, fermions (fundamental particles that make up matter) become what is known as a Fermi gas or liquid, capable of climbing walls or even crossing them.

The best-known examples of strange behavior at low temperatures are superconductivity and superfluidity.

Superconductivity occurs when a substance is able to transmit electricity without resistance.

Superfluidity is the total loss of viscosity of a substance. This state of matter can be achieved by a Fermi liquid at very low temperatures, close to absolute zero.

At these extreme temperatures, almost everything freezes except a few helium isotopes, which become superfluid. In this state, they can climb the walls of the container that contains it.

What future implications might this type of experiment have?

Ibarra reckons that, as we reach lower temperatures, different exotic phases of matter will appear.

And they can have completely different magnetic or transport properties than what has been observed with other materials so far.

In the case of a future superconductivity of copper oxides, for example, it would be possible to use this attribute for the levitation and movement of trains.

For Torcal-Milla, “every experiment that advances knowledge is important, no matter how small the discovery.”

“If we could tell our grandparents that, with a small device in our pocket, we can access any information and also speak and even instantly see a person on the other side of the world, we would be treated like crazy or charlatans,” he argues.

“Some discoveries may take time to gain practical application, but there is no doubt that they will reveal new things to us, which we cannot even predict yet,” he adds.

“Who knows if the study of these systems could indicate a new physics capable of guiding us to the definitive theory that unifies all fundamental forces, or of revealing the microscopic properties of matter, which are still unknown”, he concludes.

This text was originally published here.