Ummm... Uh oh...

[siliconshaman]

Ok, you've all heard of the Fermi paradox, right? Best estimates are that there should be intelligent life out there, what with an estimate of  few billion earth-like planets in our galaxy alone. But there's no evidence of them to date.

One possible reason is that 'something' is killing off civilisations, say every few hundred years. In particular wiping out technological or space going species. To date, no-one has any good ideas as what that might be... but I think I might just have come up with a possible candidate.

As you may or may not know, most galaxies have a super-massive black hole located at the centre. They are very active swallowing stuff at first, but quickly attract and 'eat' anything in range and go silent, only occasionally gobbling up a dust cloud that gets too close. Thing is, as they do so, they produce intense bursts of gamma and X-rays. Basically, they irradiate the hell out of anything too close. Such as is happening in Galaxy M106

Obviously, anything  living on a planet too close is going to get cooked by the radiation, but it's the effects further out that spell doom for a technological civilisation, producing a decades long EMP that would fry anything electrical, and lethal doses of radiation for anything outside of the atmosphere.  One could postulate that with a strong enough pulse, it could wipe out civilisations throughout the host galaxy. Sterilising planets orbiting core suns, and 'nuking' civilisations further out back into the stone age.

This need only happen every few hundred years to ensure that no intelligent life ever advances much further than our level...and thus ensuring that there aren't any advanced races within detectable distance.

To digress slightly, if a civilisation has been creating detectable signals for only a couple of hundred years, then they'd need to be within  a couple of hundred light years of us so we could 'see' them. A gamma & X-ray burst every so often would reset this clock and prevent there being any detectable civilisations within our range, depending on the distribution thereof.

Of course, the question then is, how big does a dust cloud have to be, in order to produce a strong enough radiation pulse that it would affect civilisations as far out from the core as we are for example....

This might seem like an academic question, except for one point:

There's a dust cloud falling inwards towards our own Galactic black hole that's due to impact at the end of this year.

Lets hope all it does is provide a pretty light show.

Comments

[natalief]

Hopefully it totally sterilises Earth rather than sending us back to the stone age. Which would you consider more likely?

[siliconshaman]

The distance we are from the core, plus the size of the dust cloud, the range of likely scenarios lies between 'damn all effect' to 'the lights go out all over the globe'. Heavily weighted towards the 'damn all' end.

I'd say a world sterilising event isn't all that likely. Now, if we were half the distance away from the core, I'd say there was a chance.

[maureenlycaon_dw]

The fact that it's in the Daily Mail doesn't encourage me. :P I'd be more worried about internal causes.

Plenty of elaborate explanations have been proposed for our being alone in the cosmos, including the idea that we're an incurably evil species and have been put in a permanent quarantine. But Occam's Razor suggests a simpler answer: that intelligence invents the economic, social, and technological conditions that allow psychopathy to thrive, and once that happens, psychopathy expands and kills a civilization. That vast silence that has greeted our SETI antennae has a simple message: You're Next. -- John Rember, on the blog Nature Bats Last, entry "Emotional Morons," http://guymcpherson.com/2011/10/emotional-morons/

[thnidu]

Spin.

[siliconshaman]

Eh, even a stuck clock is sometimes right. In this case the Daily Mail was accurate, probably because they cut&pasted it form the original article.

I don't know about internal causes... study of prior civilisations show that internal stresses and conditions can weaken a civilisations response to an external threat or natural disaster to a fatal degree.. but they don't seem to be sufficient as the prime cause of collapse by themselves. I suspect that any society posses enough momentum of habit to survive provided there is no external stress.

[thnidu]

To digress slightly, if a civilisation has been creating detectable signals for only a couple of hundred years, then they'd need to be within a couple of hundred light years of us so we could 'see' them. A gamma & X-ray burst every so often would reset this clock and prevent there being any detectable civilisations within our range, depending on the distribution thereof.

"Within our range"... We could still see any civilization whose signals we could pick up, no matter how far away they were (had been). But only within a certain ill-defined but limited range would they still be there, and only within half that range would they still be there to see our reply. Not that there'd be much point to starting such a conversation anyway.

Not that I grant the premise anyway, either.

[siliconshaman]

Ok, what I meant by 'within our range' is : within a distance less than the time it would take for a signal detectable by our technology and of sufficient strength to travel from them to us as measured from the point in their development when they first started transmitting said detectable signals. In other words, so we were within the signal wave front of their detectable signals.

So, if civilisation A has been transmitting something we can pick up for 100 years, they could be a maximum of 100 light years away... aka maximum range 100 light years.

Of course, if civilisation B started transmitting 10,000 years ago, provided it was a strong enough signal, then their maximum detectable range is 10,000 light years.. whether they are still there or not.

However, you can see why I attempted to condense that a bit...