The crafts will be in “free-fall” between Earth and the sun.
A team from the European Space Agency (ESA) recently positioned a spacecraft 1.5 million kilometers (932,000 miles) away from Earth.
The spacecraft, named the Laser Interferometer Space Antenna (LISA) Pathfinder, is in a region of space where the gravitational pull of both Earth and the sun are cancelled out by one another. What this means is that the objects onboard, which include two 1.9-kilogram (4.1-pound) cubes of gold-platinum alloy, are actually free-falling through space — floating exactly 37.5 centimeters (14.8 inches) apart.
Since the cubes are in free-fall, they shouldn’t move, and if they do, it's likely because they were influenced by an external force, such as gravitational waves, which are 'ripples' in the fabric of space-time, and cause objects to slightly wiggle. After some experimentation, the team announced that they are able to accurately measure movements of the cubes smaller than the width of an atom. It is not gravitational wave small, but it is still an amazing achievement.
The spacecraft can measure movements at the femtometer scale, which is one millionth of a billionth of a meter, explained Jesse Emspak for Smithsonian Magazine. "We wanted to see picometer scale motions," Martin Hewitson, the mission’s senior scientist, told Smithsonian Magazine. "It's more than 100 times better than [observations] on the ground."
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What has physicists excited is that this measurement will likely lead to a better way to detect gravitational waves, which were detected for the first time in February by the Laser Interferometer Gravitational Wave Observatory (LIGO).
While the LISA Pathfinder isn’t big enough to detect gravitational waves — the objects being measured must be very far apart so that the wave can hit both of them at slightly different times — researchers should be able to use similar environments in space in discern them.
In fact, the team will soon begin the next phase using the Evolved Laser Interferometer Space Antenna (eLISA). The team will launch and park three separate spacecrafts in orbit between the sun and Earth — just like LISA Pathfinder. However, these crafts will link up to form an L shape, with each of them 999,402 kilometers (621,000 miles) apart.
At these distances, and using the same measuring techniques inside LISA Pathfinder, the team should be able to measure movements that are only a few trillionths of a meter, but also detect gravitational waves that are 0.0001 to 1 Hertz — much more sensitive than LIGO.
"We now know gravitational waves are detectable — they exist," explained ESA’s Directorate of Science, Fabio Favata, to Al Jazeera, "and now, thanks to LISA Pathfinder, we know that we have sufficient sensitivity to observe them from space, and therefore a new window to the Universe has been opened."
Understanding gravitational waves may lead to new insight into how the universe works. The study is published in the journal Physical Review Letters.