Atoms vs apples: How quantum effects challenge gravity’s rules

 

International Conference on Nuclear Physics

 


One of the pillars of our understanding of gravity is the assumption that all particles, regardless of their mass, move in a gravitational field along the same trajectories at the same rate. The first experiments to test this principle were carried out by Galileo Galilei at the end of the 16th century, when he dropped balls made of different materials and weights from the top of the Leaning Tower of Pisa in Italy, confirming they all reached the Earth’s surface at the same time.

“It is a result of numerous experiments that the trajectory of a freely falling body is independent of its internal structure and composition,” said Vyacheslav Emelyanov, professor of theoretical physics at the Karlsruhe Institute of Technology in Germany, in an email. “Accordingly, all bodies fall down to the Earth with the same acceleration. This result is known as the universality of free fall.”





The universality principle became an integral part of Newton’s theory of gravity, formulated back in the 17th century, and was included in Einstein’s general theory of relativity developed later on. Einstein’s theory is crucial in situations where gravitating bodies move at velocities close to the speed of light or when gravitational fields are exceptionally strong, such as those generated by black holes and neutron stars.

However, though Newton and Einstein’s theories have helped describe gravity on the scale of planets, stars, galaxies, and even the Universe as a whole, they are classical theories that do not take into account quantum effects, which are crucial to understanding the physics of atoms and elementary particles.
Do particles “fall” the same way?

In a recent study published in Annalen der Physik, Emelyanov sought to understand whether the principle of universality for free-falling objects remains valid even on these microscopic scales. To do this, he theoretically analyzed the trajectories of the elementary particles falling in a gravitational field, combining classical and quantum theories.


“We take into account that microscopic bodies are best described by quantum theory, while gravity is still due to spacetime curvature [as predicted by general relativity],” he explained.

According to quantum mechanics, in many aspects, particles can be best described not as point-like objects, but as waves spread through space, making the notion of a particle’s trajectory somewhat meaningless, particularly if it is free falling in a gravitational field.

Emelyanov found that waves with different masses did not “fall” the same way that classical particles are expected. Instead, they move with different acceleration under gravity, violating the principle of free fall universality.

“An atom falls down to the Earth faster than an apple,” he said. “Furthermore, different atoms fall with a different accelerations that depend on their composition. Our work thus gives a novel experimental channel for testing both quantum physics and gravity.”

Measuring the calculated correction to the acceleration of a macroscopic object when it moves in a gravitational field is challenging task. The quantum correction is typically so minuscule that it becomes practically impossible to detect, especially considering the large magnitude of the acceleration itself.

For example, for one gram of iron, the correction is more than 75 orders of magnitude less than the acceleration. However, when it comes to atoms, the situation changes since their significantly smaller masses make the correction comparatively more significant. In this context, measuring the correction becomes a potentially solvable experimental problem — with the right experimental set-up.


Future evidence

“The most promising technology for testing our result is atom interferometry, as it is designed to employ microscopic bodies,” said Emelyanov. “Here, one uses the wave nature of atoms to perform high precision measurements of the universality of free fall. It is, however, hard to say at the moment when exactly this technique will be advanced enough to test our finding with sufficient accuracy, either on the ground or in space.”

In addition to testing the principle of universality of free fall, Emelyanov’s result may future experimental studies, which are of paramount importance to our understanding of the quantum properties of fundamental interactions.

“There are plenty of theoretical arguments favoring the idea that gravity must also have quantum nature. It is therefore of interest to take quantum aspects of gravity into account by a self-consistent description of matter plus gravity,” said Emelyanov.

“It needs in particular to be described how gravity is sourced by quantum matter. This should open the way to the experimental understanding of quantum gravity in the lab,” he concluded.


#Atoms#ElementaryParticles#AtomicStructure#Chemistry#Matter
#PeriodicTable#AtomicPhysics#Nucleus#Electrons#Protons#Neutrons#ValenceElectrons

Comments

Post a Comment

Popular posts from this blog

Shape-shifting experiment challenges interpretation of how cadmium nuclei move

Image
Atomic nuclei take a range of shapes, from spherical (like a basketball) to deformed (like an American football). Spherical nuclei are often described by the motion of a small fraction of the protons and neutrons, while deformed nuclei tend to rotate as a collective whole. A third kind of motion has been proposed since the 1950s. In this motion, known as nuclear vibration, atomic nuclei fluctuate about an average shape. Scientists recently investigated cadmium-106 using a technique called Coulomb excitation to probe its nuclear shape . They found clear experimental evidence that the vibrational description fails for this isotope's nucleus. This finding is counter to the expected results. Research published in Physics Letters B builds on a long quest to understand the transition between spherical and deformed nuclei . This transition often includes vibrational motion as an intermediate step. The new result suggests that nuclear physicists may need to revise the long-standing para...
Read more

HOMESPACE NEWS Mysterious Physics Revealed: “One of the Most Violent Events You Can Imagine in the Universe”

Image
Recent simulations of two black holes colliding at close to the speed of light have shed light on the enigmatic physics behind what has been called by one astrophysicist as “one of the most violent events you can imagine in the universe.” The findings, published in Physical Review Letters, is the first detailed look at the aftermath of such a cataclysmic clash, and shows how a remnant black hole would form and send gravitational waves through the cosmos. Black hole mergers are one of the few events in the universe energetic enough to produce detectable gravitational waves, which carry energy produced by massive cosmic collisions. Like ripples in a pond, these waves flow through the universe distorting space and time. But unlike waves traveling through water, they are extremely tiny, and propagate through “spacetime,” the mind-bending concept that combines the three dimensions of space with the idea of time. This simulation shows two black holes colliding near the speed of light, revea...
Read more

Nuclear power: The safer and cheaper alternative to fossil fuels

Image
As countries across the globe struggle to balance their desire for a reliable energy supply with their contribution to climate change, nuclear power presents a solution. The global reliance on fossil fuels is a function of our energy needs, and although there have been numerous initiatives implemented in order to reduce demand, such as levying large taxes on air transport, appropriate sources of supply still need to be defined. Fossil fuels such as coal, oil and gas have the benefit of being capable of servicing our energy needs. However, they are a chief contributor to climate change, and as countries attempt to meet the Paris Agreement of keeping global temperature below 2o above pre-industrial levels, non-carbon energy sources are essential. Positives and negatives So, what are the pros and cons of nuclear power as a safer, cheaper alternative to fossil fuels? Well, where renewable sources such as wind or solar are clean, they are also intermittent, require an uneven geographical ...
Read more