Albert Einstein dared to assert that Isaac Newton was mistaken about gravity in 1916. No, he insisted, it is not an enigmatic power coming from Earth. Instead, according to Einstein, time and space are twisted into an interdimensional grid, whose laces resemble unwinding paper clips. Moldable; able to bend. He argued that the illusion of a force tying us to the ground is only experienced by our simple human bodies since we are a part of this intangible network. That is what gravity is. And while the brilliant mathematician termed this puzzling idea his theory of general relativity, a name that remained, his contemporaries referred to it as "completely stupid and preposterous," a name that did not. Einstein's mind-numbing concept has yet to fail, despite all odds. On both the tiniest and the most unbelievable scales, its premises hold true. Experts have often tried to undermine them, but general relativity has always been shown to be correct.
And on Wednesday, researchers revealed that general relativity has once again been demonstrated to be a universal fact by means of an ambitious satellite experiment. With a mission called Microscope, the team performed what it claims to be the "most accurate test" of one of the fundamental ideas of general relativity, known as the weak-equivalence principle.
The author of a recent research, Manuel Rodrigues, a scientist at the French aerospace lab ONERA, said, "I have been working on this subject for more than 20 years, and I appreciate the luck I had to be the project manager of the science instrument and the co-investigator of this mission. It is extremely uncommon to leave such a stunning result in the annals of physics.
What's the weak-equivalence principle?
It's strange how the weak-equivalence principle works. When no other force is operating on an object, it basically states that all objects in a gravitational field must fall in the same direction. By external interference, I mean things like wind, someone kicking the object, another object bumping against it, etc. Yes, I do mean all items when I say that. According to this rule, whatever you can think of must fall in the same way, including a feather, a piano, a basketball, you, and I.
A satellite carrying a platinum alloy and a titanium alloy was sent into Earth's orbit as part of the Microscope experiment. According to Rodrigues, "the selection was based on technology factors," such whether the materials were simple and practical to create in a lab. The fact that these alloys were sent into Earth's orbit is crucial for comprehending the WEP because it proves that objects in space exist solely in the gravitational field of our planet. Excellent for the testing requirements. Once the satellite was in orbit, the scientists started testing for years to see if the titanium and platinum pieces fell in the same pattern as they orbited the Earth. They did, and to a very fine degree.
The development of an instrument and a mission that no one had ever done before with such accuracy—a new world to explore—was the project's most exciting component, according to Rodrigues. "Because we were the first to enter this new realm, we expected at every moment to meet phenomena that were not observed before. If you're interested in the details, the experiment's findings revealed that the difference in fall acceleration between the two alloys was less than one part in 1015. The researchers claim that a difference greater than this amount would indicate that the WEP is broken by how Einstein's theory is currently understood. Future plans include a mission named Microscope 2 that, according to Rodrigues, will test the weak-equivalence principle 100 times more effectively. But according to the researchers, this is probably as good as it will go for at least a decade or two.
The solidity of general relativity theory poses a challenge in some ways. That's because, although being a necessary blueprint for comprehending our cosmos, there are other blueprints as well. The standard model of particle physics, which describes how things like atoms and bosons function, and quantum mechanics, which explains phenomena like electromagnetic and the uncertainty of existence, are other concepts we have. But note this caution. These two ideas are incompatible with general relativity despite the fact that they both appear to be equally unbreakable. Thus, there must be a problem. And it's that something that keeps us from telling one cohesive tale of the physical universe. For instance, the standard model is infamous for its inability to describe gravity, whereas general relativity hardly takes quantum processes into account. It resembles a fierce struggle to have the best theory.
Rodrigues gave the example that "some theories foresee a link between gravitation and some electromagnetic properties." We are at a fork in the path, "This coupling does not exist in Einstein's theory, that is why the WEP occurs." The good news is that most scientists believe that none of these hypotheses are complete. As a result, if we can somehow complete them—discover a new coupling, for example, as Rodrigues suggests, or find a new particle to include in the standard model—that could point us in the direction of the missing pieces of our universe's puzzle. The cracking of the WEP, according to Rodrigues, "should represent a revolution in physics." It will imply that we discover a new force or perhaps a new particle, such as the graviton, which is the holy grail of physics.