Close to 50 years ago we humans graduated to what astronomers call a "civilization," or a lifeform that can send and receive messages over interstellar distances and that has the ability to travel in space.
This is wonderful. At the same time, while traveling to the Moon is one achievement, traveling to another star is a vastly different level of problem.
Alpha Centauri is the nearest star system to us out of the approximately 300 billion stars in our Galaxy, yet it appears to be profoundly out of reach. Such a journey would take approximately 100,000 years and require an amount of energy equivalent to one-hundred times the world's supply. It may be that this so-called "tyranny of distance" will preclude us from ever exploring our Galactic backyard.
On the other hand, humans have insatiable curiosities and a seemingly-boundless sense of imagination. One such example of dreaming big is put forward by the "Breakthrough Initiative," founded by Yuri and Julia Milner.
They ask us to consider the following question: what if we could pare down the prohibitive time and energy costs of long-term space travel by reducing the mass of a spacecraft from
hundreds of thousands of pounds to a total mass of one gram? That is right. What if the mass of the entire spaceship plus solar sail (part of its method of propulsion), plus telemetry electronics plus other electronics would weigh the same as a raisin?
If one can build such a nano-ship, then one could in principle send this probe to Alpha Centauri in 20 years instead of of canonical 100,000 years!
The suggested form of propulsion would make use of radiation pressure. In short, the wee spaceship would unfurl a solar sail which would then be bombarded with a concentrated beam of light.
The light would bounce off of the sail, therby imparting momentum to it just as wind that hits a boat sail on the ocean will propel a water-born vessel.
Using this "solar sail" the spacecraft can in principle accelerate to speeds of 100 million miles per hour. Is this for real? Well, it just might be. In fact, real research and development money is available now to contribute to designing the spacecraft.
Proposals are open to anyone with a good idea in this Breakthrough Initiative project that with any luck will literally propel us to Alpha Centauri to explore new potentially habitable worlds.