Riding a laser beam to Alpha Centauri, how the Sun pushes on the Earth and 22 kinds of space tape

Stars in their eyes: Yuri Milner (left) and Stephen Hawking. (Courtesy: Bryan Bedder)

By Hamish Johnston

What to do if you have millions of dollars lying around and a keen interest in physics? The physicist turned Internet tycoon Yuri Milner has already spent some of his fortune rewarding leading scientists and funding research. His latest project is called “Starshot” and involves spending a cool $100m on sending a spaceship to Alpha Centuri – the closest star system to Earth at just 40 trillion kilometres away.

Backed by Stephen Hawking and Freeman Dyson, the spaceship would essentially be a disk-like sail that’s about two metres in diameter and would carry a tiny electronic cargo. Once launched into space, a powerful laser on Earth would be fired at the sail, propelling it into the cosmos. Researchers working on the project reckon that the spaceship could be accelerated to a significant percentage of the speed of light and would be passing Pluto after about a day’s journey. What’s more, a number of identical spacecraft could be launched in the hope that one of them reaches Alpha Centuri in a journey that would take about 20 years. The best description I have found of Starshot is in The Atlantic: “Inside a billionaire’s new interstellar mission”.

Staying on the subject of radiation pressure, Chad Orzel has done a back-of-the-envelope calculation about the force exerted by sunlight on Earth. If you want to know the answer, you will have to read the blog that he writes for Forbes: “How hard does the Sun push on the Earth?”.

Finally, what do you think astronauts use to make minor repairs aboard the International Space Station? The answer, according to the French astronaut Thomas Pesquet, is a choice of 22 different kinds of tape. He has posted a lovely display of all the different tapes on his Twitter feed. Can you guess what each sample is used for?