A research program proposes launching a nanospacecraft with a light sail, propelled by a laser beam at up to about a third of the speed of light, to reach a nearby black hole within decades and test the theory of relativity under extreme conditions—if a nearby target is found and the laser arrays and tiny probes are developed.
It might sound like something out of a science fiction movie: a spacecraft weighing no more than a paperclip, propelled by a laser beam, hurtling through space at a third of the speed of light toward a black hole. The goal would be to explore the very nature of space and time while putting the laws of physics to the test. But for astrophysicist and black hole expert Cosimo Bambi, this vision is far from impossible.
In a paper published in iScience, Bambi outlines a plan to make such a deep-space mission a reality. If successful, the journey would take a century and provide data from nearby black holes that could change what we know about general relativity and the fundamental laws of the universe.
"We don't have the technology now," he says, "but in twenty or thirty years we might."
Two challenges ahead of us
This ambitious idea depends on overcoming two main hurdles – finding a black hole that will be a close enough target and designing probes that can withstand the entire journey.
Based on current knowledge of stellar evolution, there could be a black hole just 20-25 light-years from Earth. But detecting one is not easy, explains Bambi. Black holes do not emit light, so they are effectively invisible to telescopes. Instead, scientists detect them by observing how they affect nearby stars or bend light that passes close to them.
"There are new techniques for detecting black holes," says Bambi. "I think it's reasonable to expect that we could find one nearby in the next 10 years."
Nanospacecraft: The Quick Solution
Once the target is identified, the next hurdle is getting there. Traditional spacecraft, powered by chemical fuel, are too cumbersome and slow for this journey. Bambi points to nanospacecraft—gram-weight probes that include a microchip and a light sail—as a possible solution. Lasers from Earth would bombard the sail with photons, accelerating the spacecraft to a third of the speed of light.
At this rate, the spacecraft could reach a black hole 20-25 light-years away in about 70 years. The information it collects will take another two decades to return to Earth, so the total duration of the mission will be around 80-100 years.
Exploring physics at the edge of reality
As the spacecraft approaches the black hole, researchers will be able to conduct experiments to answer some of the most pressing questions in physics. Does a black hole really have an event horizon, the boundary beyond which not even light can escape its gravity? Do the laws of physics change near a black hole? Does Einstein's general theory of relativity hold under the most extreme conditions in the universe?
Bambi points out that the lasers alone would cost a trillion euros today, and the technology to create nanospacecraft doesn't exist yet. But in 30 years, costs may come down and technology will catch up with these bold ideas. "It sounds crazy and closer to science fiction, but they said we'd never detect gravitational waves because they're too weak. And we did, after a hundred years. They thought we'd never observe the shadows of black holes. Now, after fifty years, we have images of two."
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One response
In my opinion, we'll reach the nearest star first.
Suggestion: Use a particle accelerator to accelerate a chip into space. Or to spray fuel on its sail, because creating momentum with a laser is extremely energy-intensive (83 kWh to accelerate one kilogram by one meter per second).
Does physics change? I don't think there is a place where this happens. At most, under different conditions we pay attention to different laws, or ones we don't know. In the sense of "a law given and it will not pass away" (Psalms, chapter 148, verse 6).