Even mysterious ghost particles that barely interact with ordinary matter adhere to the theory of general relativity, proving Einstein right once again.
These lightweight high-energy subatomic particles called neutrinos provide the strongest piece of evidence yet for the Lorentz principle.
The Lorentz principle is a cornerstone of Einstein's relativity theory stating that all objects follow the laws of physics as long as they are traveling at a constant speed.
Lorentz Symmetry
According to one aspect of Einstein's relativity theory, all objects will observe the same speed of light even if they are traveling at different speeds.
An astronaut traveling at a speed of millions of miles per hour will observe light traveling at the same speed as a snail crawling at its own pace on a sidewalk in Massachusetts. Both will still observe light traveling at 985 million feet per second.
However, scientists have not stopped challenging Einstein's theory of relativity since it was first published in 1905. Since neutrinos were discovered in the late 1950s, some experts have been questioning if the chargeless particles would adhere to the Lorentz principle.
They wondered if, at the scale of neutrinos, a mysterious force called Lorentz violation could cause these objects to change their behavior in a way that Einstein would not have known.
Neutrinos Adhere To Relativity Theory
In a new study published in the journal Nature Physics, scientists at the Massachusetts Institute of Technology in Cambridge and the IceCube Experiment at the Amundsen-Scott South Pole Station in Antarctica found that even neutrinos are not above Einstein's theory of relativity.
After analyzing two years' worth of data collected by the 1-gigaton IceCube neutrino detector, the team of researchers concluded they found no anomalies indicating that a neutrino defied the laws of physics as suggested by Einstein.
"We were looking to see if a Lorentz violation caused a deviation, and we didn't see it," says lead author Janet Conrad, professor of physics at MIT. "This closes the book on the possibility of Lorentz violation for a range of high-energy neutrinos, for a very long time."
What Are Neutrinos?
Neutrinos are high-speed, high-energy particles streaming through the universe. They hit the Earth every day but rarely interact with ordinary matter. These particles oscillate between three different flavors: electron, muon, and tau.
When neutrinos coming from space hit the 1-kilometer block of ice sitting beneath the IceCube observatory, they oscillate into muons. IceCube is composed of more than 5,000 light sensors buried deep in the ice.
As the neutrinos oscillate into muons, they produce light that is picked up by the sensors, allowing them to be spotted by the particle detector.
This makes neutrinos a natural interferometer, says Teppei Katori, study co-author and professor of particle physics at the Queen Mary University in London. The changes in oscillations can help scientists find the smallest of effects, such as deficits in space-time.
No Evidence Of Lorentz Violation
If the Lorentz principle holds true, the researchers should be able to predict the oscillation rate of a neutrino of a given mass. This means a neutrino should have to travel a certain distance before it becomes a muon.
Any deviation from this could be enough to upend Einstein's relativity theory, at least at the level of neutrinos. However, the researchers failed to find anomalous variations in the oscillations of these neutrinos.
The result is even more remarkable since the researchers studied the highest-energy neutrinos ever detected on Earth. If a Lorentz violation existed, they would have easily spotted at such high energies.
"We were able to set limits on this hypothetical field that are much, much better than any that have been produced," says Conrad.
