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The stars are not within our reach!
Catchy and contrarian title. But it has nothing to do with whether you can achieve your dreams or not. It has a more concrete meaning. It has to do with the reality of the universe, and why something that a lot of us assume will come to pass may never happen.
When I was a child my dad spent 6 months in Israel on an Exchange program between the Kenyan and Israeli Ministries of Agriculture. He spent a fair amount of that time in a kibbutz (Kenya and Israel sharing the common problem that they have a lot of arid land that they need to grow crops on). He brought me back a gift, a pair of 7x35 binoculars (that I later found out were military issue, which would explain their longevity. This was back in the late 70s or early 80s and in 2010 they were going strong). At the time, I had fallen in love with Astronomy and Science Fiction. I spent many a night on the roof of our house in a suburb of Nairobi (this was before Nairobi became woefully light polluted). I used those binoculars to scan the skies for my favorite stars and nebula (I loved the Large Magellanic Cloud and the Orion Constellation, especially the M42 nebula in Orion). I would fantasize about one day walking on the surface of planets orbiting distant stars.
Stellar distances are measured in light years or parsecs (a parsec is 3.26 light years). A light year is the distance light travels in a year. Light is very fast, traveling at 186,000 miles per second (300,000 km per second). It is hard to get ones mind around that speed. It is also hard to get ones mind around the universe. Light takes 8.5 minutes to get to us from the sun. Most Science Fiction (with a few notable exceptions), treats stellar distances as an inconvenience easily overcome by some esoteric technology (i.e. warp drive).
To really understand what those distances mean, you have to shrink the universe to a scale that we can better grasp. The sun is massive; about 865,000 miles in diameter. Let us take the sun and shrink it down to the size of a basketball (9.25 inches). At that scale, the Earth (diameter of about 7900 miles) would be a sphere 0.08 inches in diameter (very small, about the size of a BB ball). But what would be even more amazing is the distances between the celestial bodies. Earth, now the size of a BB ball, would orbit the sun at a distance of 83 feet. Mercury, the closest planet to the sun, would orbit at a distance of about 53 feet.
What about the other planets and stars. Pluto (smarting from the insult of being recently demoted from being a planet a few years ago and being summarily shrunk down in size for our thought experiment), would orbit at a distance of almost 3300 feet, or 0.6 miles on our scale model of the solar system. The closest star to the sun, Alpha Centauri (4.2 light years away), would be a whopping 4200 miles from our sun! That distance is greater than the distance from New York to Los Angeles (2448 miles).
The fastest spacecraft we’ve ever had is the Juno Space probe, which at one point achieved a velocity of 73,800 meters per second (165,000 miles her hour). If we shrank Juno to fit our scale model (it would be incredibly tiny), it would be moving at the absolutely blazing speed of … 1.7 inches per hour.
And therein lies the problem and why none of us will live to see humans walk on planets orbiting other stars, (and if we don’t blow up the world or somehow cause our own extinction) our children, and grand-children probably also won’t. Imagine how long it would take to get to Los Angeles from New York traveling at 1.7 inches per hour. If we were to accelerate a spaceship instantaneously to the fastest the Juno probe ever travelled, and set it on a course to Alpha Centauri, our closest neighboring star, it would take 17,296 years to arrive. And that’s just our closest neighbor. M42 in Orion, is a staggering 1,344 light years away. The Large Magellanic Cloud, a satellite companion of our galaxy (The Milky Way), is 163,000 light years away. When you look up at the stars you are looking back in time. Some of the light you see left its home star before we existed as a species.
Barring a massive leap in technology (wormholes, Alcubierre drive etc), space travel outside our solar system is beyond our reach for the foreseeable future.