<story><title>The Fermi paradox revisited: Technosignatures and the contact era</title><url>https://arxiv.org/abs/2211.16505</url></story><parent_chain><item><author>AlbertCory</author><text>Well said. The &amp;quot;Drake Equation&amp;quot; is complete and utter garbage. There is no such thing as a &amp;quot;probability&amp;quot; of any of those terms, in the way we normally understand probability, i.e. dice or card games.&lt;p&gt;That said, there probably &lt;i&gt;are&lt;/i&gt; intelligent civilizations somewhere in the universe, but we have that pesky problem of distance and the speed of light, as you said. People like to imagine that eventually civilizations find a way around it, but in all likelihood they don&amp;#x27;t.</text></item><item><author>credit_guy</author><text>The Fermi paradox is good for a nice chat at a party.&lt;p&gt;But it&amp;#x27;s not a paradox at all.&lt;p&gt;Imagine there&amp;#x27;s an alien civilization in our galactic neighbor Proxima Centauri. How would we know they are there?&lt;p&gt;To make it more plausible. Let&amp;#x27;s say we figure out a way to send a space probe to Proxima Centauri. How do we communicate with that probe? Easy, you say, just like we communicate with the Voyagers: they point a reasonably large parabolic antenna at us, we point a point a much larger one at them, and we chat all day long.&lt;p&gt;Except that Proxima Centauri is 2000 times farther that Voyager. And signals decrease with the square of the distance. By the time Voyager gets to be 4.25 light years away from Earth, their puny 22W antenna will send us a signal that&amp;#x27;s 4 million times weaker than what they send us now (when we get less than 200 bits&amp;#x2F;second).&lt;p&gt;It&amp;#x27;s actually worse than that, of course. If Voyager were to send a signal from some arbitrary place 4.25 light years away, we&amp;#x27;d get it as something 4 million times weaker. But if that place is in the solar system of Proxima Centauri, it&amp;#x27;s like us looking straight at the headlights of an incoming car. That very weak signal will need to be extracted from the extraordinarily bright noise coming from the star that&amp;#x27;s roughly speaking about 1 second of arc away from it.&lt;p&gt;Now imagine that instead of Voyager, it&amp;#x27;s just some aliens that are not pointing an antenna straight at us, but just minding their own business. They could be launching rockets, watching satellite TV, waging wars, and from time to time lobbing Himars at each others, and even nukes. How would we know they are there?&lt;p&gt;And now finally imagine that there are no aliens in the Proxima Centauri system, by the luck of the draw, but there are in 5% of all the star systems in the galaxy. Only the closest ones to us are 40 light years away, instead of 4. That&amp;#x27;s another reduction in signal by a factor of 100.&lt;p&gt;The only question is not why we didn&amp;#x27;t &amp;quot;see&amp;quot; any aliens so far. It&amp;#x27;s why we wasted so much money on SETI. Was Carl Sagan not able to do the back of the envelope calculation I just did here?</text></item></parent_chain><comment><author>nobody9999</author><text>&amp;gt;Well said. The &amp;quot;Drake Equation&amp;quot; is complete and utter garbage. There is no such thing as a &amp;quot;probability&amp;quot; of any of those terms, in the way we normally understand probability, i.e. dice or card games.&lt;p&gt;I&amp;#x27;d say that any &lt;i&gt;result&lt;/i&gt; you try to pull from the Drake Equation is &amp;quot;complete and utter garbage.&amp;quot;&lt;p&gt;The value in the Drake Equation isn&amp;#x27;t in any calculation we might do with it.  Rather, it&amp;#x27;s a way to categorize both the variables necessary for the development of technological civilizations, and our ignorance as to both the value of such variables and variables we don&amp;#x27;t even know exist (which can be added as we learn more).&lt;p&gt;In fact, the Drake equation[0] was never intended to be useful &lt;i&gt;as an equation&lt;/i&gt;:&lt;p&gt;&lt;pre&gt;&lt;code&gt;   The equation was formulated in 1961 by Frank Drake, not for purposes of 
   quantifying the number of civilizations, but as a way to stimulate scientific 
   dialogue at the first scientific meeting on the search for extraterrestrial 
   intelligence (SETI)
&lt;/code&gt;&lt;/pre&gt;
[0] &lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;en.wikipedia.org&amp;#x2F;wiki&amp;#x2F;Drake_equation&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;en.wikipedia.org&amp;#x2F;wiki&amp;#x2F;Drake_equation&lt;/a&gt;</text></comment>
<story><title>The Fermi paradox revisited: Technosignatures and the contact era</title><url>https://arxiv.org/abs/2211.16505</url></story><parent_chain><item><author>AlbertCory</author><text>Well said. The &amp;quot;Drake Equation&amp;quot; is complete and utter garbage. There is no such thing as a &amp;quot;probability&amp;quot; of any of those terms, in the way we normally understand probability, i.e. dice or card games.&lt;p&gt;That said, there probably &lt;i&gt;are&lt;/i&gt; intelligent civilizations somewhere in the universe, but we have that pesky problem of distance and the speed of light, as you said. People like to imagine that eventually civilizations find a way around it, but in all likelihood they don&amp;#x27;t.</text></item><item><author>credit_guy</author><text>The Fermi paradox is good for a nice chat at a party.&lt;p&gt;But it&amp;#x27;s not a paradox at all.&lt;p&gt;Imagine there&amp;#x27;s an alien civilization in our galactic neighbor Proxima Centauri. How would we know they are there?&lt;p&gt;To make it more plausible. Let&amp;#x27;s say we figure out a way to send a space probe to Proxima Centauri. How do we communicate with that probe? Easy, you say, just like we communicate with the Voyagers: they point a reasonably large parabolic antenna at us, we point a point a much larger one at them, and we chat all day long.&lt;p&gt;Except that Proxima Centauri is 2000 times farther that Voyager. And signals decrease with the square of the distance. By the time Voyager gets to be 4.25 light years away from Earth, their puny 22W antenna will send us a signal that&amp;#x27;s 4 million times weaker than what they send us now (when we get less than 200 bits&amp;#x2F;second).&lt;p&gt;It&amp;#x27;s actually worse than that, of course. If Voyager were to send a signal from some arbitrary place 4.25 light years away, we&amp;#x27;d get it as something 4 million times weaker. But if that place is in the solar system of Proxima Centauri, it&amp;#x27;s like us looking straight at the headlights of an incoming car. That very weak signal will need to be extracted from the extraordinarily bright noise coming from the star that&amp;#x27;s roughly speaking about 1 second of arc away from it.&lt;p&gt;Now imagine that instead of Voyager, it&amp;#x27;s just some aliens that are not pointing an antenna straight at us, but just minding their own business. They could be launching rockets, watching satellite TV, waging wars, and from time to time lobbing Himars at each others, and even nukes. How would we know they are there?&lt;p&gt;And now finally imagine that there are no aliens in the Proxima Centauri system, by the luck of the draw, but there are in 5% of all the star systems in the galaxy. Only the closest ones to us are 40 light years away, instead of 4. That&amp;#x27;s another reduction in signal by a factor of 100.&lt;p&gt;The only question is not why we didn&amp;#x27;t &amp;quot;see&amp;quot; any aliens so far. It&amp;#x27;s why we wasted so much money on SETI. Was Carl Sagan not able to do the back of the envelope calculation I just did here?</text></item></parent_chain><comment><author>gcanyon</author><text>&amp;gt; There is no such thing as a &amp;quot;probability&amp;quot; of any of those terms...&lt;p&gt;&amp;gt; That said, there probably are intelligent civilizations somewhere in the universe&lt;p&gt;...pick one :-)</text></comment>