Recent CERN experiment reveals gravity's grip

27.09.2023 posted by Admin

Recent CERN experiment challenges sci-fi notions

Antimatter has recently lost some of its mysterious allure. In the realm of physics, there's a known counterpart to every fundamental particle - an antiparticle. These antiparticles share the same mass as their ordinary counterparts but possess opposite qualities, such as charge and spin. When these pairs collide, they annihilate each other, releasing energy in the process.

In the world of science fiction, antiparticles often fuel futuristic concepts like warp drives. Some physicists have even speculated that antiparticles might defy gravity or perhaps travel backward in time.

However, a new experiment conducted at CERN, the European Center for Nuclear Research, is shedding light on the reality of antiparticles. It turns out that in a gravitational field, antiparticles behave just like regular matter, falling under the influence of gravity. As Joel Fajans from the University of California, Berkeley, put it, "There's no free lunch, and we're not going to be able to levitate using antimatter."

Dr. Fajans was part of an international team called ALPHA, based at CERN, led by Jeffrey Hangst from Aarhus University in Denmark. Their experiment involved creating around 100 anti-atoms of hydrogen and suspending them in a magnetic field. When the magnetic field was gradually reduced, these anti-hydrogen atoms descended at the same rate as regular atoms, obeying the laws of gravity. Their findings were published in the journal Nature.

This outcome didn't come as a surprise to most physicists. According to Einstein's theory of general relativity, all forms of matter and energy should react to gravity in the same way.

Nevertheless, conducting the experiment was essential to confirm these expectations. As Jonathan Wurtele, a physicist at the University of California, Berkeley, noted, "The opposite result would have had big implications."

Back in 1928, physicist Paul Dirac made a groundbreaking discovery. While describing the electron using a quantum mechanical equation, he found two solutions. One described the negatively charged electron, which is fundamental to chemistry and electricity. The other solution portrayed a positively charged particle.

At first, Dirac believed this particle to be the proton, but J. Robert Oppenheimer proposed that it was a brand-new particle: the positron, which is identical to an electron but carries a positive charge and spin. This discovery led to the detection of positrons by Carl Anderson, earning him a Nobel Prize in Physics.

From there, the concept of antimatter was born. Antiparticles correspond to the particles that make up ordinary matter. In theory, entire antiworlds could exist, inhabited by antibeings. The jest suggests that if you met your antiself, they would extend their left hand for a handshake, but accepting it would lead to mutual annihilation.

For scientists, the allure of antimatter lies in the opportunity to test profound hypotheses about the nature of the universe. They expect antimatter to behave identically to ordinary matter. Over the last two decades, scientists from the ALPHA group at CERN have been collecting antimatter. They've slowed down high-energy antiprotons from the Large Hadron Collider and mixed them with anti-electrons (positrons) produced from radioactive sodium decay. This process creates a few anti-hydrogen atoms, with an antiproton nucleus orbited by a positron.

In 2002, Dr. Hangst's team demonstrated that these anti-hydrogen atoms emit and absorb light at the same frequencies as regular hydrogen, confirming Einstein's predictions. Several indirect experiments have also suggested that antimatter responds to gravity just like ordinary matter, but these weren't definitive due to the feeble nature of gravity compared to electromagnetic forces.

In the recent experiment, anti-hydrogen atoms were contained within a magnetic field in a metal container. Since these atoms have their own slight magnetic properties, they bounced off the container walls. By tuning the magnetic fields, the researchers could counteract gravity and suspend the anti-hydrogen atoms. When the magnetic fields were slowly reduced, the atoms eventually escaped and annihilated on the chamber walls, indicating that gravity affected them similarly to regular matter.

This experiment reinforced the expectation that antimatter responds to gravity normally, a crucial step in advancing the field of antimatter science. However, it also leaves a significant unanswered question: according to the principles of relativity and quantum mechanics, the Big Bang should have created equal amounts of matter and antimatter, leading to their mutual annihilation. Yet our universe is predominantly composed of matter, with very little antimatter found except in specific circumstances like cosmic ray showers and particle-collider collisions. The mystery of why the universe contains matter and not antimatter continues to perplex scientists, and experiments like the one conducted by the LHCb team at the Large Hadron Collider are ongoing in search of answers. However, the ALPHA experiment's results do not provide any immediate insights into this cosmic imbalance, leaving the question of our existence unanswered.
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