Scientists sent a satellite into space to test Einstein’s weak equivalence principle with extreme precision.
Why it matters
The weak equivalence principle is integral to general relativity, so these test results provide even more support for a core theory of our universe.
In 1916, Albert Einstein dared to declare that Isaac Newton was wrong about gravity. No, he said, it’s not some mysterious force emanating from the earth.
Instead, Einstein envisioned that space and time are twisted into an interdimensional lattice, and the strings of that lattice are like unwound paper clips. bendable; malleable. Just because we exist within this kind of immaterial web, he believed, do our simple human bodies experience it facade a force that keeps us grounded. We call that gravity.
(If that’s got your brain hurt, don’t worry, here’s an article that breaks down this concept.)
And while the mathematician genius dubbed this puzzling notion his general theory of relativity, a title that stuck, his colleagues called it “utterly impractical and absurd,” a title that didn’t. Against all odds, Einstein’s amazing idea has yet to falter. Its premises remain true both in the smallest and in the incredibly large. Experts have tried time and time again to poke holes in them, but general relativity always prevails.
And on Wednesday, thanks to an ambitious satellite experiment, scientists announced that general relativity has once again been proven to be the fundamental truth of our universe. The team performed what they called the “most precise test” of one of the key aspects of general relativity, called the weak equivalence principle, using a mission called the microscope.
“I’ve been working on this topic for more than 20 years and I realize how lucky I was to be project manager of the scientific instrument and co-researcher on this mission,” said Manuel Rodrigues, scientist at the French aerospace laboratory ONERA and author of a new study , published in the journal Physical Review Letters.
“This is very rare to leave such a remarkable result in the history of physics.”
What is the principle of weak equivalence?
The principle of weak equivalence is strange.
It pretty much states that all objects in a gravitational field must fall the same way if no other force is acting on them – I’m talking external perturbations like wind, a person kicking the object, another object bumping into it , understand idea.
And yes, when I say all objects, I mean all objects. A feather; a piano; a basketball; you and me; Anything you can really imagine must fall in exactly the same way, according to this principle.
The microscope project sent a satellite into Earth orbit containing two objects: an alloy of platinum and an alloy of titanium. “The selection was based on technological considerations,” Rodrigues said, such as whether the materials would be easy and viable to make in a lab.
But most important to understanding the principle of weak equivalence, or WEP, these alloys were launched into Earth orbit because things exist up there in our planet’s gravitational field with no other forces acting on them. Perfect for the test criteria. Once the satellite was in space, researchers began years of testing to see if the platinum bit and titanium bit fell off in the same way as they orbited the earth.
They did – to an extremely precise extent.
“The most exciting part during the project was the development of an instrument and a mission that nobody had done before with such a level of accuracy – a new world to explore,” said Rodrigues. “As pioneers of this new world, we expected at any moment to face phenomena not seen before because we were the first to enter.”
If you’re interested in the technical details, the results of the experiment showed that the gravitational acceleration of one alloy differed from the other by no more than a 10^15 part. A difference beyond that size, the researchers say, would mean that the WEP is violated by our current understanding of Einstein’s theory.
Looking ahead, the team is working on a follow-up mission called Microscope 2, which Rodrigues says will test the weak equivalence principle 100 times better.
However, this is likely as good as it has been for at least a decade or so, the researchers say.
Great, what does this mean for me?
In a way, the soundness of general relativity is an issue. Because while it’s an essential blueprint for understanding our universe, it’s not that only Draft.
We also have constructs like the Standard Model of particle physics, which explains how things like atoms and bosons work, and quantum mechanics, which explains things like electromagnetism and the uncertainty of existence.
But here’s the caveat.
Both concepts seem as unbreakable as, but incompatible with, general relativity. So… something must be wrong. And that something prevents us from creating a unified history of the physical universe. The Standard Model, for example, is notoriously incapable of explaining gravity, and general relativity doesn’t really account for quantum phenomena. It’s like a huge struggle to be the ultimate theory.
“Some theories expect a coupling between gravity and some electromagnetic parameters,” Rodrigues gave as an example. “This coupling does not exist in Einstein’s theory, therefore WEP exists.”
We are at a crossroads.
But the good side is that the vast majority of scientists believe all of these theories to be correct unfinished. So if we can somehow find a way Finished they—for example, finding a new coupling, as Rodrigues says, or identifying a new particle to add to the Standard Model—that could lead us to the missing pieces of the puzzle of our universe.
“It was supposed to be a revolution in physics,” Rodrigues said of breaking the WEP. “It will mean that we will find a new force, or maybe a new particle like the graviton – it’s the grail of physicists.”