4 ms·

If we just stop for a moment and think how little we can “receive” from our surrounding (100 hundred light year max?) and how vast the universe, even our galaxy

If we just stop for a moment and think how little we can “receive” from our surrounding (100 hundred light year max?) and how vast the universe, even our galaxy is and how incredible long the time span between the birth of the first stars and the birth of our petite civilization then we will realize we still can deduce nothing about the existence or non-existence of other civilizations.

lukastr0 5y ago
What do you mean? Why can't we receive signals from more than "100 hundred light year" away?
- SimplyUnknown 5y ago
  I mean, we definitely can. We see stars that are thousands of lightyears away! However, maybe OP means "receive" as "response to a message we sent". This is indeed something we are able to do since ~100 years, so our communication bubble is currently ~100 lightyears.
- hoseja 5y ago
  Well, signals sent from Earth (radio, TV, etc...) are indistinguishable from noise at about that distance.
- plutonorm 5y ago
  Because of the very large amounts of energy to transmit information in all directions from such a large distance. Also because it's such a stupid waste of energy. Why send radio waves out in all directions in order to communicate with a neighbor? Use a light beam instead. So the lack of huge radio transmitters that we can detect really just means aliens aren't investing huge amounts of money into letting us know they exist. Why would they? Especially if they already know of other civilisations.
koheripbal 5y ago
This is only for omnidirectional radio signals. Directional beams can go arbitrarily further.
- sinuhe69 5y ago
  What kind of “directional” signal you can think of sending from a planet millions years ago that can hit earth exactly in the moment a SETI antenna directed at it and ready to receive? And how much energy should this civilization keep pumping in the signal to increase the probability that someone can receive them? And why it should make any sense to waste energy like this when the probability that you can receive a confirmation is equal zero even when other civilizations are out there? About the required power and signal degradation over distance, see this: https://www.quora.com/How-far-do-radio-signals-travel-into-space-before-they-degrade-to-a-degree-beyond-being-possible-to-be-detected https://www.quora.com/How-far-do-radio-signals-travel-into-s...

lukastr0 5y ago

What do you mean? Why can't we receive signals from more than "100 hundred light year" away?

SimplyUnknown 5y ago
I mean, we definitely can. We see stars that are thousands of lightyears away! However, maybe OP means "receive" as "response to a message we sent". This is indeed something we are able to do since ~100 years, so our communication bubble is currently ~100 lightyears.
hoseja 5y ago
Well, signals sent from Earth (radio, TV, etc...) are indistinguishable from noise at about that distance.
plutonorm 5y ago
Because of the very large amounts of energy to transmit information in all directions from such a large distance. Also because it's such a stupid waste of energy. Why send radio waves out in all directions in order to communicate with a neighbor? Use a light beam instead. So the lack of huge radio transmitters that we can detect really just means aliens aren't investing huge amounts of money into letting us know they exist. Why would they? Especially if they already know of other civilisations.

koheripbal 5y ago

This is only for omnidirectional radio signals. Directional beams can go arbitrarily further.

sinuhe69 5y ago
What kind of “directional” signal you can think of sending from a planet millions years ago that can hit earth exactly in the moment a SETI antenna directed at it and ready to receive? And how much energy should this civilization keep pumping in the signal to increase the probability that someone can receive them? And why it should make any sense to waste energy like this when the probability that you can receive a confirmation is equal zero even when other civilizations are out there? About the required power and signal degradation over distance, see this: https://www.quora.com/How-far-do-radio-signals-travel-into-space-before-they-degrade-to-a-degree-beyond-being-possible-to-be-detected https://www.quora.com/How-far-do-radio-signals-travel-into-s...