In this Sunday’s comic strip “Beetle Bailey”, the dumbest guy in Camp Swampy asks the smartest questions, and nobody knows the answers. Zero: “Boy! I’d like to visit one of those stars.” Sarge: “It would take you years to travel through space to get to one of them.” Exactly. But how long would that really take?
Happily, Wikipedia has provided in-depth answers for Beetle, Sarge and Zero. Check out these two links:
As it happens, I had been musing about the same question. I know the numbers, but can’t wrap my head around the calculations. For questions like “how long to Alpha Centauri”, I need a spreadsheet:
The Moon and Sun are included only to give an idea of scale here. My spreadsheet is compressed to fit on this page. Distances: Proxima Centauri 4.23, Barnard’s Star 5.96, Sirius 8.58, Gliese-581 20.3 light years.
Speeds: Earth orbital velocity is a puny 18-24,000 miles per hour. Pioneer was accelerated by Jupiter to an escape velocity of 132,000 miles per hour before leaving the solar system in 1995 — at a distance of 6.5 billion km from Earth. At that distance, its radio signal took 6 hours to reach Earth.
Scientists believe that speeds of one-one thousandth of the speed of light ( .001 c) are attainable with current technology, probably ion engines, though it would take such low-thrust propulsion systems decades to accelerate to those velocities. In the next century or so, it is thought newer technology might allow us velocities approaching .01 c.
Even so, the spreadsheet makes it crystal clear that travel to even the very closest star, Proxima Centauri, would require sending a massive vehicle with support for suspended animation or multiple generations of space travelers. At a million miles an hour, a one-way trip would take over 3,900 years; at 9.2 million miles an hour, several human lifetimes. It would take radio signals from those travelers up to 4 years to reach us, but no one alive on Earth at launch time would ever live to hear whether the mission arrived successfully. A return trip, if any, would double travel time.
Speeds of one-tenth light speed are still in the realm of science fiction. Even then, travel beyond Sirius, say a visit to the nearby Orion Nebula (1,344 light years distant), would take over 12,000 years, one way. We could pedal around the globe infinitely faster on a kiddie tricycle. It seems clear we’ll never get to cross the street or leave the neighborhood without the hyper-drives of Hollywood’s Star Wars.