The theory revolutionised our understanding of gravity, light and time, and paved the way for many modern technologies.
The European Space Agency’s latest mission, Lisa Pathfinder, has successfully launched from its spaceport in French Guiana.
The spacecraft has an experiment on board that could revolutionise our understanding of the Universe.
“The purpose of this spacecraft is to eventually detect something that Einstein’s theory of general relativity predicts and hasn’t been detected yet which is gravitational waves,” Francisco Diego, senior research fellow at the Department of Physics and Astronomy, told Al Jazeera.
“We believe and we anticipate that this is the way gravity travels in space.”
Most of our knowledge about the Universe is based upon our observation of electromagnetic waves including visible light, infrared, X-rays and gamma rays.
But 100 years ago Albert Einstein, in his theory of general relativity, predicted another form of wave existed, and these gravitational waves have a profound effect on the Universe.
“What that basically says is when a gravitational wave passes by the Earth we get stretched and squeezed,” Paul McNamara, LISA Pathfinder’s Project Scientist, told Al Jazeera.
“We are trying to build a detector which will allow us to measure the stretching and squeezing of the fabric of space-time as the gravitational wave is passing.”
One billionth of a millimetre
To do this the mission is sending the spacecraft towards the Sun, stopping it at a point 1,500,000km away, where the Sun’s gravitational pull is cancelled out by that of the Earth’s.
This makes it an ideal location for testing the new highly sensitive gravity sensing technology that cannot be tested on Earth because of its own gravitational pull.
The spacecraft has two small identical cubes of solid gold-platinum alloy onboard.
These free-fall through space at the same speed as the craft, while a laser is used to measure their relative motion with unprecedented accuracy; movements as small as one billionth of a millimetre.
This level of precision is required as it is believed that space-time is largely rigid and only deforms as a result of extraordinary forces.
“When a gravitational wave is produced, for example when two massive back holes at the centre of galaxies smash into each other, it creates these ripples in space-time,” said McNamara.
“But because it is stiff, the ripples are not very big so we have to have a very precise instrument which allows us to pick up the minuscule changes in space-time itself.”
The Dark Universe
Previous research has lead scientists to believe that current telescopes are only able to detect just 4 percent of the matter in the Universe.
It is hoped a gravitational wave detector will help them “see” some of the other 96 percent of matter, including dark matter.
“When we open the gravitational wave window to the Universe we are seeing completely new objects, things that we have never been able to see before and never will be able to see using electromagnetic spectrum,” said McNamara.
“We’re really on the cusp of observing the Universe in a whole new way.”
Although Lisa Pathfinder will not be able to confirm the existence of gravitational waves it will help scientists test their technology and approach.
If successful, a large-scale experiment involving three satellites, placed a million kilometres apart is planned for launch in 2034.
“We are just trying to find out how the universe works and gravity is one of the components of the universe which is the most mysterious one,” said Diego.
“The results of all these experiments will have enormous applications that we cannot even imagine.”