Life is Only on Earth

Assuming your figures are correct, I did not know that signal loss was this severe. If that's the case the odds of detecting anything is pretty much zero.
It's technically not a loss, the signal simply gets diluted by time and space. Since we have been transmitting anything at all, it has only propagated so far and it perforce is spread out in space it is pretty feeble in a galactic scale.
 
At this point we branch into the 'generation ship' discussion. If alien races want to 'take our stuff' or just live on our planet then they face a colossal engineering challenge, a multi-thousand year trip and a serious fight when they arrive. SILLY!

No we don't.
 
I think that while we are talking about 'aliens' perhaps coming here, the chances that our planet is toxic to them is a definite possibility, even with panspermia of some sort.
 
I think that while we are talking about 'aliens' perhaps coming here, the chances that our planet is toxic to them is a definite possibility, even with panspermia of some sort.
Nothing that evaporating it in to raw compounds from orbit can't fix.
 
We can estimate the odds of getting hit by a meteor/comet. These odds are not zero, they are knowable.

But that's not the argument he was making. He was talking about the extreme possibility as a reason for hiding. The same logic applies to asteroids, and the odds are irrelevant because that's not the point either he or I were making.
 
But that's not the argument he was making. He was talking about the extreme possibility as a reason for hiding.

The possibilities aren't extreme, they're simply unknown.

The same logic applies to asteroids, and the odds are irrelevant because that's not the point either he or I were making.

No, asteroids are a known threat. Annihilation from aliens is unknown. When dealing with unknown threats, one should be cautious. The risks outweigh the benefits.
 
The possibilities aren't extreme, they're simply unknown.

I would think "nothing" and "everything" are pretty much extreme possibilities, since there is nothing beyond them.

No, asteroids are a known threat. Annihilation from aliens is unknown.

So how can you possibly claim that the latter is more threatening than the other?

When dealing with unknown threats, one should be cautious. The risks outweigh the benefits.

That makes zero sense. The asteroid thread is KNOWN to be existential. Being known doesn't make you more benign.
 
You didn't say "weird", but you mentioned "life came so quickly after life on Earth first became possible it seems like there is probably some underling mechanism whereby life isn’t just common it’s inevitable" and "There is a need to explain why we only see one specific chemical regime ( eg right handed DNA with 4 specific nucleotides)".

I'm 100% clueless on the topics of what about the quickness of the appearance of life implies anything, as well as why there's a need to explain the why's behind that specific DNA formation.

The fact that every organism uses the same basic chemistry for DNA when there are other possibilities suggests that all life on earth arose from a single series of events that only occurred once in its 4-billion-year history. This suggests these events could be very rare and life is very rare. Conversely this series of events happened almost as soon as they were physically possible on the earth’s surface. The suggests life should be common or even inevitable, popping up quickly whenever suitable conditions exist.

If you want to know how common life is in the universe, therefore, you need to know which of these two is really the case, and for that you need to explain why life started so early but never again.
 
The fact that every organism uses the same basic chemistry for DNA when there are other possibilities suggests that all life on earth arose from a single series of events that only occurred once in its 4-billion-year history. This suggests these events could be very rare and life is very rare. Conversely this series of events happened almost as soon as they were physically possible on the earth’s surface. The suggests life should be common or even inevitable, popping up quickly whenever suitable conditions exist.

If you want to know how common life is in the universe, therefore, you need to know which of these two is really the case, and for that you need to explain why life started so early but never again.

Oh! I actually did already know about that, sort of. I've always learned towards life being very rare, and the original event that sparked life being something like "infinite monkey theorem" as applied to molecules in the primordial soup.
 
Oh! I actually did already know about that, sort of. I've always learned towards life being very rare, and the original event that sparked life being something like "infinite monkey theorem" as applied to molecules in the primordial soup.

There is also the possibility that shortly after life got going, it had changed the environment so much that the conditions for for life to begin no longer existed. Or at least the conditions changed to make a second start much more unlikely.
 
This reminds me of Roko's basilisk
https://rationalwiki.org/wiki/Roko's_basilisk

The risk of me trashing AI is unknown as well


So are the risks of you muttering about what a lousy simulation this is. They might just erase you.

The caution Hawking was talking about is an entirely different thing. We know there is a technologically advanced race with a penchant for war: us. There might be others like us. Who knows how they would react? Hawking's caution works for any interpretation of the Drake Equation: if one thinks there are no other advanced races out there, beaming hello messages to habitable planets is pointless. If one thinks there are a lot (or just some) advanced races out there, beaming hello messages carries a risk.
 
There is also the possibility that shortly after life got going, it had changed the environment so much that the conditions for for life to begin no longer existed. Or at least the conditions changed to make a second start much more unlikely.

As I said before, if it's a one in a million year occurrence, then most of the likely locations for the second start would already have been colonised. It's highly unlikely that proto-life would be anything other than a concentrated food source for actual life.
 
So are the risks of you muttering about what a lousy simulation this is. They might just erase you.

The caution Hawking was talking about is an entirely different thing. We know there is a technologically advanced race with a penchant for war: us. There might be others like us. Who knows how they would react? Hawking's caution works for any interpretation of the Drake Equation: if one thinks there are no other advanced races out there, beaming hello messages to habitable planets is pointless. If one thinks there are a lot (or just some) advanced races out there, beaming hello messages carries a risk.

Not much of one. Interstellar probes (or missiles) would require massive resource commitments and probably take thousands of years to reach their destination.

A civilisation would have to decide to develop the technology and launch the weapons, whilst hoping that their target doesn't notice over whatever technological improvements they develop over these thousands of years and doesn't decide to retaliate.

Suppose you found a technological civilisation on Alpha Centuri, what would you target? Maybe the home planet, but what if they colonise other planets within their solar system or even asteroids in the intervening centuries.?
 
There is a Douglas Adams quote for every occasion. Re being annihilated by aliens:

"For thousands more years the mighty ships tore across the empty wastes of space and finally dived screaming on to the first planet they came across—which happened to be the Earth—where due to a terrible miscalculation of scale the entire battle fleet was accidentally swallowed by a small dog."
 
If one thinks there are a lot (or just some) advanced races out there, beaming hello messages carries a risk.

Remaining ignorant of the situation regarding life in the universe also has risks. There are too many unknowns to determine which is more dangerous.

For example, what if civilizations that do not attempt to make contact with others are deemed to be dangerously unsocial.
 
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Not much of one. Interstellar probes (or missiles) would require massive resource commitments and probably take thousands of years to reach their destination.

A civilisation would have to decide to develop the technology and launch the weapons, whilst hoping that their target doesn't notice over whatever technological improvements they develop over these thousands of years and doesn't decide to retaliate.

Suppose you found a technological civilisation on Alpha Centuri, what would you target? Maybe the home planet, but what if they colonise other planets within their solar system or even asteroids in the intervening centuries.?

Turn it around a bit. Suppose you're a very advanced civ in Alpha Centuri and you've been monitoring this incredibly violent civ that is going through a technological explosion. They are not a threat NOW, but at their rate of progress they will eventually become one, and they're right next door and they like wars a lot. How hard would it be to send a couple asteroids their way at 10%C? Probably not that hard. Problem solved.
 
Remaining ignorant of the situation regarding life in the universe also has risks. There are too many unknowns to determine which is more dangerous.

For example, what if civilizations that do not attempt to make contact with others are deemed too be dangerously unsocial.

I don't think the risk is the same. Other races will have evolved, like we did. The same "laws of the jungle" will have applied to them as it did to us (kill or be killed). They'll probably understand the desire to be cautious in an unfamiliar environment.

But you're right, staying silent carries a risk. What if a race evolved without any history of predation? They might wonder about us. Why are you guys so quiet over there? What are you up to? Looks like you've got something to hide...

Good point.
 
Turn it around a bit. Suppose you're a very advanced civ in Alpha Centuri and you've been monitoring this incredibly violent civ that is going through a technological explosion. They are not a threat NOW, but at their rate of progress they will eventually become one, and they're right next door and they like wars a lot. How hard would it be to send a couple asteroids their way at 10%C? Probably not that hard. Problem solved.

.10c? How about a more realistic speed.
 
Well good luck to any race trying to achieve those numbers.

Personally I think life, at least at the level we're at, is rare. I don't state it as fact but my incredulity from considering all of the factors--could be circular reasoning.
 
Well good luck to any race trying to achieve those numbers.

.

Indeed, I'll just write 30,000 km/s that you presumably want to steer to hit the sun after at least decades of travel at speeds where dust will be dangerous to the impactor.

And just on the off chance that they might do the same, as opposed to just waiting to see if that happens and develop a retaliation.

Nope, not a concern.
 
Assuming in silico life is possible (meaning as uploads or A.I.s), life in a solar system could be distributed in thinking matter, making it resistant to any physical shock bar a supernova.
 
Indeed, I'll just write 30,000 km/s that you presumably want to steer to hit the sun after at least decades of travel at speeds where dust will be dangerous to the impactor.

And just on the off chance that they might do the same, as opposed to just waiting to see if that happens and develop a retaliation.

Nope, not a concern.

If you take a ten ton asteroid, slap some fusion motors on the back of it, random bits of interstellar dust won't do anything to it. There's no delicate machinery you have to protect at the bow end. Your motors and fuel are protected by the mass of the asteroid and you don't have to worry about decelerating. Just fire the motors occasionally to course correct, and then wait for the fireworks.
 
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how do you course-correct without detectors? They would be vulnerable.

What sort of motors would have an exhaust velocity of 30,000 km/second?

What temperature would the control "electronics" get to over the decades of acceleration?
 
I don't think the risk is the same. Other races will have evolved, like we did. The same "laws of the jungle" will have applied to them as it did to us (kill or be killed). They'll probably understand the desire to be cautious in an unfamiliar environment.
You cannot even possibly know that. Look at the "Independance Day" scenario. "We will kill you all and take your stuff" is the bottom line. How can you know that your imaginary aliens are not taking that position? How can you know that they don't regard us as some kind of vermin to be exterminated?

You simply do not and can not.

Hell, if you want to apply the "laws of the jungle" they would likely eat us. Protein, Yum.
 
Turn it around a bit. Suppose you're a very advanced civ in Alpha Centuri and you've been monitoring this incredibly violent civ that is going through a technological explosion. They are not a threat NOW, but at their rate of progress they will eventually become one, and they're right next door and they like wars a lot. How hard would it be to send a couple asteroids their way at 10%C? Probably not that hard. Problem solved.

Staggeringly hard, given the difficulty of projecting the asteroids, the range and the tiny moving target. So stunningly hard that only a race of morons would try it.
 
how do you course-correct without detectors? They would be vulnerable.

Have the homeworld give you the telemetry. Communicate with them with instruments on the back end. They would know your position and the position of your target. You wouldn't even need to do that. You would know the Earth's position because it's entirely predictable. You would know your position by looking at stars. You wouldn't need to leave the back end to fix your position in space.

What sort of motors would have an exhaust velocity of 30,000 km/second?

Why would you need that? Constant acceleration of 1 foot per second (squared) would get you to 10%C in three years.

What temperature would the control "electronics" get to over the decades of acceleration?

I couldn't begin to guess. Constant acceleration of 1fps, isn't all that fast, but you are moving a lot of mass.
 
You cannot even possibly know that. Look at the "Independance Day" scenario. "We will kill you all and take your stuff" is the bottom line. How can you know that your imaginary aliens are not taking that position? How can you know that they don't regard us as some kind of vermin to be exterminated?

You simply do not and can not.

Hell, if you want to apply the "laws of the jungle" they would likely eat us. Protein, Yum.

I'm saying evolutionary pressures wouldn't be different for them than they are for us. Survival of the fittest is a universal principle. Alien life couldn't just pop into existence. It would have begun simple at some point, and become complex. Natural selection would have been at work. It would know this about itself. It would know the benefits of caution.

This was in response to a post suggesting that hiding ourselves might carry risks.
 
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Better to use some sort of micro-probe with self replicating machines. Turn the alien world to grey goo or a star gate.
 
Staggeringly hard, given the difficulty of projecting the asteroids, the range and the tiny moving target. So stunningly hard that only a race of morons would try it.

If you had a big enough telescope, you could fix the positions of the planets in the solar system. You wouldn't even need that big a telescope. We're only talking 4 LY. Once you've studied the orbits, calculating the position of the Earth at any future time is very easy, assuming no wandering black holes come through the system. The range is irrelevant, as long as you can course-correct along the way. There wouldn't be any need for shielding, since all the delicate stuff is on the back end of an asteroid and you're not planning on any decelerating. You could get up to pretty good speed using a solar sail, and then the motors could do the rest.
 
how do you course-correct without detectors? They would be vulnerable.
Carry enough detectors to toss one to the side every once in a long while, communicating with it via some advanced technology such as radio or infrared.

What sort of motors would have an exhaust velocity of 30,000 km/second?
If you're traveling at 30,000 km/s relative to some coordinate patch and toss stuff off the back at 3000 m/s relative to yourself, which can be done using conventional rockets, then the exhaust velocity is 30,003 km/s relative to that coordinate patch, so tossing that stuff off the back causes you to accelerate.

What temperature would the control "electronics" get to over the decades of acceleration?
Whatever motors you're using to toss stuff off the back will probably generate enough heat to keep the electronics as warm as necessary. Those motors could also be made to generate enough electricity to run a heat pump that keeps the temperature of the electronics below any threshold you like, radiating excess heat into space.

I'm not saying 0.1c is easy. I'm saying getting to 0.1c is a whole lot harder than solving the three problems mentioned and solved above.
 
There are a couple of possible candidates in our own backyard like Europa or Encaladus. We struggle to even test those, albeit, they do have possibilities. But you are correct, For any exoplanet the best we can do so far is claim that the evidence merely "suggests" the presence of liquid water. Sometimes I wonder if some people think Star Trek tricorders actually exist.

If we are able to observe exoplanets using spectroscopy in the future, we may be able to determine their atmospheric composition. There are certain elements which, if found in an exoplanet's atmosphere would be strong indicators for life.

Photosynthesis is the primary reason the Earth has such high oxygen levels as well as the ozone layer. This would make O2 and O3 atmospheric biomarkers; indicators that oxygen-producing biological activities may be present. Some other biomarkers are methane and nitrous oxide (emitted by microbes) and chloromethane (given off by seaweeds). Detecting the presence of all these chemicals in the atmosphere, in the right quantities, could indicate that life may be present on the planet.

Examining the atmospheres of exoplanets is something that has only been done rarely in a very limited way. It is hoped that the James Webb Space Telescope will allow astronomers to do so much more easily.

ETA: The observable universe is estimated to contain 200 billion to 2 trillion galaxies. Based Kepler data regarding the number of exoplanets discovered in our immediate vicinity of our galaxy astronomers reported that there could be as many as 40 billion Earth-sized planets orbiting in the habitable zones of Sun-like stars and red dwarfs in the Milky Way.

Even a conservative estimate makes that 200 billion x 40 billion Earth-like planets in their star's habitable zones. Thats 8e+21 or eight sextillion of these planets in the universe... 8,000,000,000,000,000,000,000 of them. I find it very difficult to believe that in all those potential opportunities for life (as we know it) it only happened once.
 
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