Earth is broadcasting on many different frequencies 24/7. Why is it that a parabolic antenna cannot just scan for all ‘fields’ of the sky for similar activity? Like an automated sweep.
Will only specific frequencies, be able to traverse the light years of distance?
I am guessing old UHF or DVB is not the most likely candidate?
So what specific ranges are being listened on?
In: Physics
Given the speed of light and how long we’ve been broadcasting, our first signals have barely gotten to any any further than a few neighboring stars, which we’re certain enough don’t have life or advanced civilizations themselves.
Consider, what is regarded as the first radio transmission was on December 23, 1900. And that may not have been at an adequate frequency or power to get past the ionosphere and into space. So if we’ve only been broadcasting for 120 years, we’ve only transmitted, AT BEST, 120 lightyears away. The Milky Way is more than 104,000 light years across.
Consider also that the power of transmission depletes with the cube of the distance. So the further away the signal goes, the weaker it is. Eventually the power over distance will sink into the noise floor of the universe and be utterly indistinguishable.
If you want a high power transmission that will go the distance, you need a powerful transmitter and you need to focus the energy. And focus isn’t perfect, so it, too, will eventually sink into the noise floor. But also consider if we transmitted this signal now, it’s still limited to the speed of light, and will take centuries to get anywhere. And also, you would have to aim that signal at something specific, or no one will hear it if they’re out of the beam.
And they themselves have to be listening.
SETI is also trying to pick up any incidental chatter, but they have to contend with all the same problems. Radio from the opposite side of the galaxy very likely won’t have the power to reach us, especially through all the gas and dust in the way.
And considering the time it takes light to travel, these civilizations may be gone by the time we hear them. We may be gone by the time they hear a response from us, IF they could hear a response from us…
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