Gravity is one of the four fundamental forces of nature, along with electromagnetism, strong nuclear force, and weak nuclear force. Therefore, our existence wouldn’t be possible without any of them. Gravity is not only preventing us from flowing chaotically through the atmosphere along with cars, laptops, phones and almost all the other stuff we use daily, but it also made possible the existence of planets, stars, and galaxies themselves.
All of the cosmic objects were born because of gravity, which gathered together what once was only space debris or hydrogen gas. You could say that all objects in the Universe attract themselves, but in most cases, the attraction is too low to be observed. For instance, you can put two ping pong balls in a basin of water, and after several minutes you’ll see them closer to each other. But what is the best way to measure gravity?
The key is looking at differences in atoms in superposition states
Everybody knows about the age-old method of measuring gravity, but the new method doesn’t involve anything falling. Instead, a team of scientists led by physicist Victoria Xu says that a better idea is to look at differences in atoms that are in superposition states (at multiple places at once until they are observed).
Scientists measured the wave particle duality of each cesium atom’s wave from a small chamber as they were affected by gravity. It all started when they used flashing lights to split some of the atoms into superposition states. Once the atoms were taken apart, lasers were used to keep them in certain positions. The researchers observed differences in duality between atoms in a pair, with each one being at some distances from Earth. Thus they were able to quantify the effects of gravity on the atoms.
The leader of the research, Victoria Xu, stated:
Laser light (purple) shines into our ultra-high vacuum chamber to laser-cool atoms to less than half a millionth of a degree above absolute zero. A pair of mirrors mounted inside the vacuum chamber enhance flashes of light which kick, suspend, and interfere the atoms.
Co-author of the study, Holger Müller, explains to us the importance of the experiment:
Let’s say you don’t want to measure the gravity of the entire Earth, but you want to measure the gravity of a small thing, such as a marble
We just need to put the marble close to our atoms [and hold it there]. In a traditional free-fall setup, the atoms would spend a very short time close to our marble — milliseconds — and we would get much less signal.
The new findings have been published in the journal Science.