The Fermi Paradox is the difference between the supposed number of planets supporting intelligent life that there should be in the vastness of the Milky Way, never mind the Universe, and the fact that we haven't picked up any radio-signals from any of them, let alone slapped a parking ticket on a visiting space-craft. Whenever anyone gets bored, they form a theory on why we have the Fermi Paradox.
The doozy is the Dark Forest Hypothesis, exploited by Cixin Liu in his Three-Body Problem trilogy, appearing so I gather on a Netflix near you. This is the idea that the universe is actually stuffed full of advanced civilisations, and they are all keeping quiet so that they aren't attacked by another one, rather like an animal moving through a forest at night, which keeps as quiet as possible to avoid giving its presence away to the predators all around it.
At the other extreme is the Uniqueness of Us hypothesis, which is that there's only us in the Universe, because making a planet that can support intelligent life and Kier Starmer is 0.000000000000000000000000000000001% possible. And that may be too high.
Then there's the We Got Here First hypothesis, which holds that we are the first civilisation advanced enough to support Angela Rayner, and all the others have just about reached Plato, or are currently building Stonehenge, or maybe are still single-cell organisms. Just think, in another million years, they too will be have their very own Rachel Reeves.
And of course, there's the Smartypants theory, which is that we have been visited by aliens, and they found us so stupid and crude, they flew off and give us a 1-star review on TripAdvisor. Or they found us too aggressive. Or they thought they would come back when Wes Streeting was not in charge of anything.
However, the boring answer is this....
Radio, television and radar broadcasts use electromagnetic waves, and electromagnetism is, as we know, magic + Maxwell's Equations. How these waves travel depends on the medium and the wavelength. Very short waves (1-10 mm) are absorbed by the atmosphere in a few kilometres. Very long waves (1-100 km) bounce between the earth and the ionosphere and can flow over hills and down valleys. Radio, television, mobile phones and radar use waves between 10cm and 100m, and these mostly travel in straight lines. The transmitters are designed to direct the waves to where the audience is, not spray it all over the place where the audience isn't, like outer space. Some of it leaks, but not a lot.
Here's the calculation. Whatever the aliens were using to listen, our signals would need to be audible above the white noise of the Universe, the Cosmic Microwave Background (CMB) radiation, that covers the radio, TV, radar and mobile phone frequencies. At those frequencies, the CMB has a power of on the order of magnitude of 10^(-7) Watts / sq metre. For a station broadcasting at 5,000 kW / sq m (which would be a lot) and an inverse-square fall-off, since 1 light-year is about 9.5 x 10^15 metres, that's a fall-off of 53dB, so our station's signal would have a strength of about 5.5x10^(-10) Watts/sq m, which is about 4dB below the CMB. To get 5dB above the CMB, we would need to have 1,024 transmitters of that strength going flat-out. All of them so badly designed that they sprayed energy in all directions equally.
At 10 light-year's distance, signal loses around another 20dB, and there aren't enough transmitters on earth to get the total above the CMB.
The nearest candidate planets are 4.22 light-years away, and the next is 11 light-years. And those aren't good candidates.
Nobody ain't hearing nothing.
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