Einstein's theory of relativity passed another huge test

Einstein’s theory of relativity passed another huge test

What happens

Scientists have sent a satellite into space to test Einstein’s principle of weak equivalence with extreme precision.

Why does it matter

The principle of weak equivalence is an integral part of general relativity, so these test results provide even more support for an underlying theory of our universe.

In 1916, Albert Einstein dared to declare that Isaac Newton was wrong about gravity. No, he said, it is not some mysterious force emanating from the Earth.

Instead, Einstein imagined that space and time are twisted into an interdimensional web, and the laces of this web are like unwound paper clips. Flexible; modelable. It is only because we exist within this kind of intangible mesh, he believed, that our simple human bodies experience facade of a force that holds us to the ground. We call this gravity.

(If that hurt your brain, don’t worry, here’s an article dedicated to breaking down the concept.)

And while the mathematical genius referred to this perplexing notion as his theory of general relativity, a title that stuck, his colleagues called it “totally impractical and absurd,” a title that it did not. Against all odds, Einstein’s heady idea still doesn’t budge. Its premises hold true on both the smallest and the incomprehensibly large scale. Experts have tried to poke holes in them again and again and again, but general relativity always prevails.

And on Wednesday, thanks to an ambitious satellite experiment, scientists announced that, once again, general relativity has been proven to be a fundamental truth of our universe. The team performed what it calls the “most precise test” of one of the key aspects of general relativity, called the principle of weak equivalence, with a mission called Microscope.

“I’ve been working on this topic for more than 20 years and I realize how lucky I was to be the project manager of the science instrument and the co-investigator of this mission,” said Manuel Rodrigues, a scientist at the lab French Aerospace. ONERA and author of a new study, published in the journal Physical Review Letters.

“It is very rare to leave such a remarkable result in the history of physics.”

A description of how Einstein’s relativity imagines the universe.

Zooey Liao/CNET

What is the principle of weak equivalence?

The principle of weak equivalence is a strange one.

It pretty much says that all objects in a gravitational field must fall the same way when no other force is acting on them — I’m talking about external interference like wind, a person hitting the object, another object hitting the he, you get the idea.

And yes, when I say all objects, I mean all objects. A feather; a piano; a basketball; you and I; whatever you can imagine, indeed, according to this principle, must fall in exactly the same way.

Project Microscope sent a satellite into Earth orbit containing two objects: a platinum alloy and a titanium alloy. “The selection was based on technological considerations,” Rodrigues said, such as whether the materials were easy and feasible to make in a lab.

But most important to understanding the weak equivalence principle, or WEP, these alloys were thrown into Earth’s orbit because things up there exist in our planet’s gravitational field without other forces acting on them. Perfect for the test criteria. Once the satellite was in space, researchers began testing, for years, whether the platinum bit and the titanium bit fell out. in the same way as they orbited the Earth.

They did — to an extremely precise degree.

“The most exciting part of the project was developing an instrument and a mission that no one had done before at such a level of precision – a new world to explore,” said Rodrigues. “As pioneers of this new world, we expected at every moment to encounter phenomena not seen before, because we were the first to enter.”

A cylindrical bronze structure supporting scientific devices, with a pointed bottom

A capsule used during the Microscope mission.

ZARM/Selig – ONERA 2013

If you’re interested in the technicalities, the experiment results showed that the fall acceleration of one alloy differed from the other by no more than one part in 10^15. A difference beyond that amount, the researchers say, would mean that WEP is violated by our current understanding of Einstein’s theory.

For the future, the team is working on a follow-up mission called Microscope 2, which Rodrigues says will test the principle of weak equivalence 100 times better.

However, this is probably as good as it will get for at least a decade, the researchers say.

Great, what does this mean for me?

In a way, the soundness of general relativity is kind of a problem. That’s because, while it’s an essential blueprint for understanding our universe, it’s not no more plan.

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 inseparable as general relativity, but they are not compatible with it. So… something must be wrong. And that something prevents us from creating a unified story of the physical universe. The standard model, for example, cannot explain gravity, and general relativity doesn’t really account for quantum phenomena. It’s like a huge battle to be the ultimate theory.

Four scientists, dressed in mint green outfits and hair nets, stand next to an oven-sized device wrapped in gold foil.

The Microscope team stands with the satellite equipment, right.

ONERA/Rodrigues 2016

“Some theories expect a coupling between gravity and some electromagnetic parameters,” Rodrigues offered as an example. “This coupling doesn’t exist in Einstein’s theory, that’s why WEP exists.”

We are at a crossroads.

But the good part is that the vast majority of scientists believe that all these theories are unfinished. So if we can somehow find a way cOMPLETION them—locate a new coupling, for example, as Rodrigues says, or identify a new particle to add to the standard model—that might lead us to the missing pieces of the puzzle of our universe.

“It should be a revolution in physics,” Rodrigues said of the WEP breach. “It will mean we find a new force, or maybe a new particle like the graviton – it’s the physicist’s Grail.”

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