Earth is Probably Unique

[Calilasseia]

Whilst large stars do indeed live fast and die young, the question is, do they do it at a fast enough rate? Large stars have to form before they can run through the cycle and deliver heavy elements. At the moment, stars large enough to end their days as supernovae comprise around 0.1% of all observable stars. Red dwarfs, on the other hand, comprise nearly 80% of the known stellar population. The distribution would have had to be considerably different in the distant past, to facilitate the existence of numerous star systems giving rise to spacefaring civilisations long before us. Then there's the little matter of the requisite star systems being formed in relatively quiescent locations, allowing evolution time to do its work.

Plus, if a civilisation had emerged in our galaxy a billion years before humans appeared, and had been successful in spreading itself across interstellar space, then it would have have had far more opportunities to persist than a civilisation tied to one planet. Even catastrophes affecting a region of space tens of light years across, wouldn't impact significantly on a civilisation whose extent spanned over 10,000 light years, just as a catastrophe limited to the Japanese mainland doesn't impact significantly on the human species globally. A civilisation that survives its initial teething troubles, to the point of becoming established over that sort of range, is going to generate a lot of evidence of its existence. For one thing, it's going to leave behind it a lot of garbage, and some of that garbage could be sufficiently large and persistent for us to detect it long after it was generated. Humans and their ancestors have left enough garbage behind them over three million years or so, to allow us to elucidate much useful information about the past which was either not explicitly recorded, or for which records were lost. Now, some of our garbage is leaving the Solar System, and we're becoming, in effect, interstellar polluters.

Plus, one reason I can think of why no interstellar civilisation passed this way, is simply this. The Solar System hasn't been exploited before our arrival. Earth in particular managed to remain untouched by exploitation until we arrived on the scene. Any antecedent civilisation turning up here would almost surely not have passed up the chance to exploit this planet and its contents, leaving nothing behind that we could use to reach the stage we've attained today.

[mistermack]

Plus, one reason I can think of why no interstellar civilisation passed this way, is simply this. The Solar System hasn't been exploited before our arrival. Earth in particular managed to remain untouched by exploitation until we arrived on the scene. Any antecedent civilisation turning up here would almost surely not have passed up the chance to exploit this planet and its contents, leaving nothing behind that we could use to reach the stage we've attained today.

Actually, I wouldn't agree with that.
If you have plenty of energy, then everything can be recycled.
And energy is actually in abundance. Just because we are short of it, doesn't mean that it's in short supply.
Crack the fusion of hydrogen, and there is more energy available than we can possibly use. As is the case everywhere above our atmosphere within range of the Sun.

So no matter how spent material is, it can be recycled as new, if you have the cheap energy.

Really, the only stuff that can't be re-processed would be stuff that gets contaminated by radioactivity, to dangerous levels, with a long half-life.

But with all the free energy available from the Sun, I can't see aliens having to bother for long with any kind of nuclear power generation.

But anyway, if aliens were after materials, they would have used the Moon first. And we would see their tracks in the dust, and all the crap that they left behind.
So I think we can safely say that we haven't been visited.

[JimC]

mistermack wrote:

...But anyway, if aliens were after materials, they would have used the Moon first. And we would see their tracks in the dust, and all the crap that they left behind....

Even more likely, the asteroids...

[mistermack]

mistermack wrote:

...But anyway, if aliens were after materials, they would have used the Moon first. And we would see their tracks in the dust, and all the crap that they left behind....

Even more likely, the asteroids...

And Trojans. And Oort cloud stuff like comets.
All of it is easier to access and use than the Earth.

And of course, the Earth could be dangerous to aliens. They might have no immunity to Earth bacteria and viruses.

[pErvinalia]

And Donald Trump.

[JimC]

mistermack wrote:
And of course, the Earth could be dangerous to aliens. They might have no immunity to Earth bacteria and viruses.

You've been watching "War of the Worlds" too much.

Biologically implausible...

[rainbow]

And Donald Trump.

...unless Donald Trump is actually a Shape-shifting Alien Lizard.

[rainbow]

mistermack wrote:

...But anyway, if aliens were after materials, they would have used the Moon first. And we would see their tracks in the dust, and all the crap that they left behind....

Even more likely, the asteroids...

And Trojans. And Oort cloud stuff like comets.
All of it is easier to access and use than the Earth.

And of course, the Earth could be dangerous to aliens. They might have no immunity to Earth bacteria and viruses.

This does perfectly illustrate the silliness of trying to extrapolate from a single sample.
We have only one example of life emerging, and we have only one example of that life evolving into intelligent beings.

...from which we can conclude very little except that we may be the only life in the Universe.

[NineBerry]

mistermack wrote:
And of course, the Earth could be dangerous to aliens. They might have no immunity to Earth bacteria and viruses.

You've been watching "War of the Worlds" too much.

Biologically implausible...

Why would that be implausible? Considering the viruses yes, but what about bacteria if the aliens' bodies are made up of proteins (and that is very likely)

[JimC]

mistermack wrote:
And of course, the Earth could be dangerous to aliens. They might have no immunity to Earth bacteria and viruses.

You've been watching "War of the Worlds" too much.

Biologically implausible...

Why would that be implausible? Considering the viruses yes, but what about bacteria if the aliens' bodies are made up of proteins (and that is very likely)

They may be protein-like, but they could be put together from a different series of amino acids, for example. An alien biochemistry, even a carbon-based one, is unlikely to provide the right nutrients for microbial invasion.

[mistermack]

mistermack wrote:
And of course, the Earth could be dangerous to aliens. They might have no immunity to Earth bacteria and viruses.

You've been watching "War of the Worlds" too much.

Biologically implausible...

Why would that be implausible? Considering the viruses yes, but what about bacteria if the aliens' bodies are made up of proteins (and that is very likely)

They may be protein-like, but they could be put together from a different series of amino acids, for example. An alien biochemistry, even a carbon-based one, is unlikely to provide the right nutrients for microbial invasion.

I disagree. Every animal and plant on Earth rots pretty quick, once it dies.
If bacteria don't have to fight immune systems, they are pretty much unstoppable.
So if aliens have no immunity built up, they might well struggle.
Just like the American Injuns did against immigrant illnesses.

And not just bacteria, but fungal infections and yeasts etc could cause them problems.

Of course, if it was a totally different type of life, they might be ok.
Or, they might be self-replicating machines, designed billions of years ago by biological aliens which then took over and continued improving and replicating more machines.
They might be impervious to practically everything. Except rust.

[piscator]

Black smoker ecosystems with crabs skipping around in 150c water at 49 bar, grazing on worms that feed on plants that use use H2S instead of sunlight.




Jus sayin'

[JimC]

mistermack wrote:

So if aliens have no immunity built up, they might well struggle.
Just like the American Injuns did against immigrant illnesses.

This example involves not only the same planetary biota, but the same species! Of course that was always going to happen. However, raccoons did not get decimated by smallpox...

Personally, I would doubt that the dead flesh from an alien biota would even be food for our decomposers. Our biochemistry effectively has a single origin, so we share the same amino acids, the same nucleic acids, the same phospholipids...

Alien analogues to these would be unlikely to have enzymes that could interact with them, for example.

[laklak]

FSM created all life, so we're all marinara based. Our bacteria will chow those aliens, assuming we don't find them tasty.

[JimC]

Black smoker ecosystems with crabs skipping around in 150c water at 49 bar, grazing on worms that feed on plants that use use H2S instead of sunlight.




Jus sayin'

Sure.

And they have the same amino acids as me.

But, unlike me, they cannot be infected by the flu virus...