Two-light years and then… enjoy the silenceMori - forgetomori.com
June 19th, 2008
In the breathtaking opening of the movie “Contact” – adaptation of the even more inspiring original Carl Sagan novel – we travel from Earth, faster than the speed of light and listening to the reverse history of our electromagnetic transmissions through the Universe.
From the Spice Girls (1997…) to the first radio broadcasts, we get farther and father from our Pale Blue Dot, seeing even bigger spaces full of billions and billions of stars in the Cosmos.
The scene is literally poetic, namely it involves a big deal of poetic license, as we listen to transmissions from decades ago while still in the outer solar system – Pluto is not that far. It even has a small joke, as the Face on Mars make a very brief appearance.
But the cold (and perhaps surprising) hard fact is that the scene is impossible. No, not only because it’s impossible to travel faster than light, but because our radio transmissions have a very limited range, and our first radio transmissions are not in some place tens of light-years away. In fact the range of our transmissions is just… well, if you read the title you already know it.
Two light-years for almost all of our transmissions. After that, even ginormous antennas turned exactly to our planet and listening to the right frequencies applying the necessary corrections would not be able to capture an intelligible signal. Even a 3.000 km antenna wouldn’t be enough to capture our TV transmissions from a distance greater than only 0,01 light-years away!
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