If solved
Interstellar probes
Gram-scale probes on light sails, pushed by a laser array on Earth to about a fifth of light speed, reach the nearest stars in about 20 years.
Open in the interactive tree →The Breakthrough Starshot study (announced 2016) planned sails about 4 m wide, a 100-gigawatt laser array and a trip of 20 to 30 years to Alpha Centauri, 4.3 light-years away. In 2025 Caltech measured the push of laser light on a 50-nanometre sail membrane in the lab for the first time. Still missing: a laser array whose beams add up into one, sail materials that survive the heat, and a way to send data back across light-years. The project was put on hold in 2025 after about 4.5 million of the announced 100 million dollars had been spent.
What it brings
- Close-up images of planets around other stars
- Measurements of the space between the stars
- A first step towards travel between star systems