The aliens are silent because they're dead

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Re: The aliens are silent because they're dead

Postby gnome » Mon Jan 25, 2016 6:36 pm

We can fail to reject the null hypothesis (that we are alone) but before we do anything that resembes "accepting" it, it is perfectly reasonable to note that it intelligent life could exist in non-trivial amounts while still not being detected at all yet.

I don't think that Drake's equation is about agreeing on a final figure, so much as it is about expressing the scale of the variables involved.
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Re: The aliens are silent because they're dead

Postby Witness » Wed Jan 27, 2016 12:15 am

Abdul Alhazred wrote:So my calculation would be 39 light years etc.

But I figured plain radio (or even just wireless telegraph) would be easier to decode than a TV signal (assuming one picks it up in the first place).


Image
Extent of human radio broadcasts
Humans have been broadcasting radio waves into deep space for about a hundred years now, since the days of Marconi. That, of course, means there is an ever-expanding bubble announcing Humanity's presence to anyone listening in the Milky Way. This bubble is astronomically large (literally), and currently spans approximately 200 light years. But how big is this, really, compared to the size of the Galaxy in which we live (which is, itself, just one of countless billions of galaxies in the observable universe)? To answer that question, Adam Grossman put together this diagram. It's not the black square; it's the little blue dot at the center of that zoomed-in square.

"Space is big", to quote Matt.

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Re: The aliens are silent because they're dead

Postby Harte » Wed Jan 27, 2016 12:32 am

A guy on ATS just forced me to do the calculation. A 20 gigawatt signal one light year away would reach us with the undetectable power of around 20X10^-22 watts.

IOW, no way Jose.

Try it yourself: link

Don't forget to:
1) convert light years to meters,
2) square the distance

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Re: The aliens are silent because they're dead

Postby ceptimus » Wed Jan 27, 2016 1:37 am

If there are intelligent aliens, it's reasonable to assume that some of them - maybe half - appeared before us.

Given the age of the galaxy, they likely appeared a long time before us - a few tens of millions of years is nothing compared to the age of the earth - let alone other solar systems.

If just one of those intelligent alien species sent out self-replicating space probes, then even if those probes travel at just a few tens of thousands of miles per hour, they've had time to spread across a sizable chunk of the galaxy.

So we have to assume that either there are no such probes, or that the probes don't want to be discovered by civilisations like ours.

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Re: The aliens are silent because they're dead

Postby Witness » Wed Jan 27, 2016 1:51 am

↑ That's the Fermi paradox.

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Re: The aliens are silent because they're dead

Postby Anaxagoras » Wed Jan 27, 2016 2:02 am

Harte wrote:A guy on ATS just forced me to do the calculation. A 20 gigawatt signal one light year away would reach us with the undetectable power of around 20X10^-22 watts.

IOW, no way Jose.

Try it yourself: link

Don't forget to:
1) convert light years to meters,
2) square the distance

Harte


Plus, wouldn't stuff like the nearby star also mask this signal with lots of electromagnetic noise?

I forget, but isn't SETI looking for aliens that might be intentionally sending us a message? It might be hard to pick up their signals if they aren't pointing them right at us, right? Because, why do that anyway? Yeah, perhaps we've done it once or twice ourselves, but we're weird.
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Re: The aliens are silent because they're dead

Postby Abdul Alhazred » Wed Jan 27, 2016 2:32 am

Fitting the aliens in the gaps.

Sort of like the "god of the gaps" argument.
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Re: The aliens are silent because they're dead

Postby Anaxagoras » Wed Jan 27, 2016 3:09 am

These are more like huge gaping chasms than gaps. The universe is big, as somebody once observed.

If we are the only ones, well, it sure would be a huge waste of space. :wink:



Also not comparable to god in other ways. We know that life (even semi-intelligent life) evolved here. So it is demonstrably possible in principle. Not so with god.
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Re: The aliens are silent because they're dead

Postby Abdul Alhazred » Wed Jan 27, 2016 3:16 am

Anaxagoras wrote:If we are the only ones, well, it sure would be a huge waste of space. :wink:


An argument that implicitly presupposes an intelligent designer.
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Re: The aliens are silent because they're dead

Postby Anaxagoras » Wed Jan 27, 2016 3:20 am

Scientists can be silly sometimes, too though.

Take those gold-plated records they sent out with the Voyager probes. Did anyone stop to calculate the odds that anyone would ever find these things floating out there in deep space? You'd probably have a better chance of winning the powerball lottery 10 times in a row with just 10 tickets (number pulled out of my ass, sure, but it's only magical thinking to suppose that those probes will ever be seen by anyone other than us again.)
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Re: The aliens are silent because they're dead

Postby Witness » Wed Jan 27, 2016 4:20 am

http://communicating.seti.org/

Universe Today wrote:Sending radio messages over sizable interstellar distances is feasible with present day technology. According to SETI Institute radio astronomer Seth Shostak, who presented at the conference, we are already — by accident — constantly signaling our presence to any extraterrestrial astronomers that might exist in our neighborhood of the galaxy. Some radio signals intended for domestic uses leak into space. The most powerful come from radars used for military purposes, air traffic control, and weather forecasting. Because these radars sweep across broad swaths of the sky, their signals travel out into space in many directions.

With radio telescopes no more sensitive than those astronomers on Earth use today, extraterrestrials out to distances of tens of light years could detect them and figure out that they were artificial. The Arecibo radar telescope in Puerto Rico is designed specifically to send a narrow beam of radio waves into space, usually to bounce them off celestial bodies and learn about their surfaces. For a receiver within its beam, it could be detected hundreds of light-years away.

FM radio and television broadcasts also leak out into space, but they are weaker and couldn’t be detected more than about one tenth of a light year away with present day human technology. This is quite a bit less than the distance to the nearest star. The size and sensitivity of radio telescopes is progressing rapidly. An alien civilization just a few centuries more advanced than us in radio technology could detect even these weak signals over vast distances in the galaxy

http://www.universetoday.com/116467/communicating-across-the-cosmos-part-1-shouting-into-the-darkness/

I also remember vaguely having read that with sufficiently low bitrate we could communicate across the Galaxy, even with today's technology. :?

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Re: The aliens are silent because they're dead

Postby Anaxagoras » Wed Jan 27, 2016 4:41 am

An alien civilization just a few centuries more advanced than us in radio technology could detect even these weak signals over vast distances in the galaxy


I think they are making assumptions about future advances in technology. Perhaps reasonable assumptions, but still assumptions.

So anyway, they would not see our TV broadcasts (given current technology), only radar signals probably. And then only as far as "tens" of light-years.


That's why I'm not surprised that SETI hasn't found anything yet, and also why I don't think it is strong evidence that we are alone.
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Re: The aliens are silent because they're dead

Postby Anaxagoras » Wed Jan 27, 2016 4:45 am

Abdul Alhazred wrote:
Anaxagoras wrote:If we are the only ones, well, it sure would be a huge waste of space. :wink:


An argument that implicitly presupposes an intelligent designer.


Hence my winky. :wink:
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Re: The aliens are silent because they're dead

Postby Bruce » Wed Jan 27, 2016 5:36 am

Abdul Alhazred wrote:The aliens are silent because they're dead
Science Daily

The universe is probably filled with habitable planets, so many scientists think it should be teeming with aliens. But life on other planets would likely be brief and become extinct very quickly, say astrobiologists. In research aiming to understand how life might develop, the scientists realized new life would commonly die out due to runaway heating or cooling on their fledgling planets.

...


One way or the other, we're all alone. :)


If you're going to dream, dream small. Very small. :roll:
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Re: The aliens are silent because they're dead

Postby Bruce » Wed Jan 27, 2016 5:38 am

Anaxagoras wrote:Scientists can be silly sometimes, too though.

Take those gold-plated records they sent out with the Voyager probes. Did anyone stop to calculate the odds that anyone would ever find these things floating out there in deep space? You'd probably have a better chance of winning the powerball lottery 10 times in a row with just 10 tickets (number pulled out of my ass, sure, but it's only magical thinking to suppose that those probes will ever be seen by anyone other than us again.)


The odds are probably much less than the probability that life could exist at all in the universe, and yet here we are. :|

:)
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Re: The aliens are silent because they're dead

Postby Doctor X » Wed Jan 27, 2016 7:13 am

There was a cheesy but fun science fiction series which opened with Marconi testing his apparatus. Angry puffed up Italian surrounded by incompetents, but he gets it to work.

And off goes his signal.

In to space . . .

. . .

. . . until it reaches a colony of parasites that decide to follow it.

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Re: The aliens are silent because they're dead

Postby Anaxagoras » Wed Jan 27, 2016 8:35 am

Witness wrote:
I also remember vaguely having read that with sufficiently low bitrate we could communicate across the Galaxy, even with today's technology. :?


Maybe ELF or VLF frequencies?

These are very long waves which can travel through water (useful for communicating with submarines) and even the earth's crust, but as you say, the longer the wave, the slower the bitrate. You also need a very large antenna.

https://en.wikipedia.org/wiki/Extremely_low_frequency
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Re: The aliens are silent because they're dead

Postby Doctor X » Wed Jan 27, 2016 8:49 am

I sometimes wonder if astronomers/astrophysicists cannot accept the implications of their own discipline: that the distances are so vast compared to the speed of information transfer limited by the speed of light the reasonable chance of contacting any life form let alone enter into a communication is negligible.

In fact, if I understand the popularly reported physics correctly, the "edge" of expansion of the universe from the Big Bang has passed the point of light ever reaching us. Take that with an appropriate scoop of sodium chloride since I am going on memory. If I understand it correctly, the universe is accelerating and at the "edge" it is accelerating faster than the speed of light which does not violate relativity since it is space-time rather than something within it and fuck it math is involved and math is hard. The point is there are areas which we not only will never receive information from we never can.

So it is not simply that we are receiving light from a star that is effectively a billion years old--what has happened to the planets around that star in a billion years since? Do they have Spray Cheese?--we will never receive signals from a civilization that developed near the "edge" assuming they even can have civilizations because there is probably a sparks there as well.

In the rain.

That is not a satisfying answer. So we keep looking. All wet.

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Re: The aliens are silent because they're dead

Postby Anaxagoras » Wed Jan 27, 2016 9:19 am

Doctor X wrote:I sometimes wonder if astronomers/astrophysicists cannot accept the implications of their own discipline: that the distances are so vast compared to the speed of information transfer limited by the speed of light the reasonable chance of contacting any life form let alone enter into a communication is negligible.

In fact, if I understand the popularly reported physics correctly, the "edge" of expansion of the universe from the Big Bang has passed the point of light ever reaching us. Take that with an appropriate scoop of sodium chloride since I am going on memory. If I understand it correctly, the universe is accelerating and at the "edge" it is accelerating faster than the speed of light which does not violate relativity since it is space-time rather than something within it and fuck it math is involved and math is hard. The point is there are areas which we not only will never receive information from we never can.

So it is not simply that we are receiving light from a star that is effectively a billion years old--what has happened to the planets around that star in a billion years since? Do they have Spray Cheese?--we will never receive signals from a civilization that developed near the "edge" assuming they even can have civilizations because there is probably a sparks there as well.

In the rain.

That is not a satisfying answer. So we keep looking. All wet.

--J.D.


Yes, and of course I too am merely a layman in these matters, but let's not let that prevent us from pontificating.
I don't think it's really known for certain how big the universe actually is. Some estimates put the observable universe at about a radius of 46 billion ly IIRC (and there are some decent youtube videos I could link to if anyone cares).

But even our own galaxy is plenty large enough. It contains 100 billion stars. Something a billion ly away would be far beyond our own galaxy (although not so far compared to the observable universe). I would rather confine the search to stuff that's relatively near to us, in our own spiral arm say, or at least prioritize that.
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Re: The aliens are silent because they're dead

Postby Abdul Alhazred » Wed Jan 27, 2016 9:38 am

Anaxagoras wrote: Did anyone stop to calculate the odds that anyone would ever find these things floating out there in deep space?


If they ever are found by some spacefaring species, it will be future humans with no idea that the ancients were capable of producing such a thing.

It will be evidence of alien life. :)
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