Do you think any aliens exist in the universe?

[pood]

Phospherous shortage may make alien life very rare.

 

[Shadowy Man]

Phospherous shortage may make alien life very rare.

Fair enough. Interesting article. When I studied abundances in the interstellar medium, phosphorus wasn’t one of my targets.

 

[lpetrich]

But ET biochemistries might avoid phosphorus. Has anyone ever made a good argument as to why phosphate ions can't be replaced with (say) sulfate ions? Being needed for nucleic acids is not, I think a good argument, since an organism may use some other carrier of heredity.

 

[pood]

But ET biochemistries might avoid phosphorus. Has anyone ever made a good argument as to why phosphate ions can't be replaced with (say) sulfate ions? Being needed for nucleic acids is not, I think a good argument, since an organism may use some other carrier of heredity.

How about arsenic?

 

[pood]

And that is from more than 10 years ago. I wonder if more research has been done on this.

 

[lpetrich]

But ET biochemistries might avoid phosphorus. Has anyone ever made a good argument as to why phosphate ions can't be replaced with (say) sulfate ions? Being needed for nucleic acids is not, I think a good argument, since an organism may use some other carrier of heredity.

How about arsenic?

That's the "arsenic bug" -  GFAJ-1 - it has been discredited - Studies refute arsenic bug claim - BBC News - it needs phosphorus just like every other organism on this planet.

 Abundances of the elements (data page) - in the oceans, 20 times less abundant. So arsenic makes the problem even worse.

 

[pood]

But ET biochemistries might avoid phosphorus. Has anyone ever made a good argument as to why phosphate ions can't be replaced with (say) sulfate ions? Being needed for nucleic acids is not, I think a good argument, since an organism may use some other carrier of heredity.

How about arsenic?

That's the "arsenic bug" -  GFAJ-1 - it has been discredited - Studies refute arsenic bug claim - BBC News - it needs phosphorus just like every other organism on this planet.

 Abundances of the elements (data page) - in the oceans, 20 times less abundant. So arsenic makes the problem even worse.

Ah, thanks. I was wondering about a link more than 10 years old, which is why I was curious if it had been followed up. Apparently it was.

 

[bilby]

If life elsewhere in the universe depends on being in a rare patch of phosphorus rich space, then there might be less of it than would be the case if phosphorus were fairly evenly distributed.

But the universe is a big place.

Even if there were only one suitable planet for life per galaxy (which seems highly implausible to me, even if phosphorus is both critical and scarce, there should be far more than that), the observable universe would still have ~170 billion such planets.

 

[pood]

If life elsewhere in the universe depends on being in a rare patch of phosphorus rich space, then there might be less of it than would be the case if phosphorus were fairly evenly distributed.

But the universe is a big place.

Even if there were only one suitable planet for life per galaxy (which seems highly implausible to me, even if phosphorus is both critical and scarce, there should be far more than that), the observable universe would still have ~170 billion such planets.

Quite, and that’s also possibly the problem with finding aliens. The universe is vast in space and time, and may be teeming with life, but so far away in space and far away in time (before or after us) that the chance of somehow detecting them may be nil. The observable universe, of course, is what we can observe. The actual universe may be spatially infinite. If it is — and evidence suggets it is — the fact that there is one inhabited planet (our own) means that the prior probability of life is nonzero. From this it follows that in an infinite universe we should expect an infinite number of inhabited planets, no matter how rare life. is.

 

[bilby]

If life elsewhere in the universe depends on being in a rare patch of phosphorus rich space, then there might be less of it than would be the case if phosphorus were fairly evenly distributed.

But the universe is a big place.

Even if there were only one suitable planet for life per galaxy (which seems highly implausible to me, even if phosphorus is both critical and scarce, there should be far more than that), the observable universe would still have ~170 billion such planets.

Quite, and that’s also possibly the problem with finding aliens. The universe is vast in space and time, and may be teeming with life, but so far away in space and far away in time (before or after us) that the chance of somehow detecting them may be nil. The observable universe, of course, is what we can observe. The actual universe may be spatially infinite. If it is — and evidence suggets it is — the fact that there is one inhabited planet (our own) means that the prior probability of life is nonzero. From this it follows that in an infinite universe we should expect an infinite number of inhabited planets, no matter how rare life. is.

Indeed.

The fact is, we've only very recently been able to detect nearby planets outside our solar system. To say that life must be rare because we haven't seen any yet is to misunderstand just how difficult it is to see anything outside our solar system that's cooler than thousands of Kelvins.

A planet identical to Earth, but orbiting a star as little as fifty light years away, would be difficult for us to spot; Our ability to detect that it hosts life (or even has markers that might imply life, such as an atmosphere with high levels of oxygen) would be very limited. And 50ly is basically right next door.

 

[steve_bank]

Going into space even LEO is not easy or cheap.

Regardless of culture or economics large scale space travel for an ET as well as us as in Star Trek would consume enormous resources.

And then energy sources. It is easy in scifi, not so easy in reality.

 

[senor boogie woogie]

I do but the chances of meeting aliens is very slim.

Distance and Speed of Light. The Speed of Light is ver fast except when it comes to space travel. The Galaxy is huge and so large and vast, light speed is a crawl. We look at other Planets outside the Solar System in Light Years, as innit would take so many Light Years to get to a Planet that might support life. If it is impossible for us to get there, how is it more possible for an alien race to come here.

Second, we might destroy ourselves. Humanity has nuclear weapons. In the future, we may use them on ourselves. Hopefully not but a probability. Who says and alien race does not have the same issues? Before a race (ours or there’s) we are not thrown back because of nuclear war to nearly caveman times if we survive and have to spend thousands of years building ourselves up again?

Aliens have passed by Earth or even quietly came here. Maybe we are already being studied by alien life. Their conclusion, the Earth people are dangerous. We are. If aliens came, our first instinct is to kill them. To an alien race, Earth is a dangerous ghetto and it is best to steer clear, unless the goal is to annihilate the human race and steal the resources. This would be the best course of action. Humans are violent and will irradiate our Planet if need be. Aliens might go “Those beings are nuts, let us not go there.”

I like to think in 10,000 years humans have left this rock we call Earth and went into space. But again we have the limitations of the Light Year. Can we go beyond light speed or is light speed lie Absolute Zero where one cannot be colder than that? Beats me. I think at best, humans might go to Mars if that, and then we will destroy ourselves. Can’t escape Earth, not really and who is to say if humans find another Planet, humans won’t slowly destroy it like Earth?

 

[ZiprHead]

There's also the time factor. Advanced civilizations on other worlds could have come and gone thousands of times before we've gotten to this point in our civilization.

 

[Loren Pechtel]

There's also the time factor. Advanced civilizations on other worlds could have come and gone thousands of times before we've gotten to this point in our civilization.

That's only a solution if nobody does interstellar colonization for some reason.

 

[bilby]

There's also the time factor. Advanced civilizations on other worlds could have come and gone thousands of times before we've gotten to this point in our civilization.

That's only a solution if nobody does interstellar colonization for some reason.

I can c about 299,792,458 reasons.

 

[steve_bank]

I think the probability of detecting our forms of communication from distant planets is very small. Everything s in motion.

EMR diminishes 1/r^2. At some point ET's transmissions fall below our detection threshold.

We can look at the difference in technology between American civilizations and European at the time Europeans arrivd.

A humanoid species can evolve, develop language and writing, elements of practical engineering, but never make the leap to what came to be western science and technology.

An ancient Greek developed steam powered machines, but did not make the leap to pistons.

 

[excreationist]

I think the probability of detecting our forms of communication from distant planets is very small. Everything s in motion.

Yeah I don't think SETI will achieve anything but apparently there could be billions of potentially habitable Earth-sized planets in the Milky Way...

 

[Loren Pechtel]

There's also the time factor. Advanced civilizations on other worlds could have come and gone thousands of times before we've gotten to this point in our civilization.

That's only a solution if nobody does interstellar colonization for some reason.

I can c about 299,792,458 reasons.

Lightsail can do .01c simply off sunlight.

I find the notion that we will never be able to upload ourselves ludicrous (assuming we don't do ourselves in, that is.)

Combine them and it's possible to go to the stars. You send your human-receiver by lightsail, the humans go by laser.

All it takes is one race with a desire to colonize and the galaxy is teeming with life.

 

[Shadowy Man]

There's also the time factor. Advanced civilizations on other worlds could have come and gone thousands of times before we've gotten to this point in our civilization.

That's only a solution if nobody does interstellar colonization for some reason.

I can c about 299,792,458 reasons.

Lightsail can do .01c simply off sunlight.

I find the notion that we will never be able to upload ourselves ludicrous (assuming we don't do ourselves in, that is.)

But will it be you or just a copy of you with all your memories?

I would never use a star trek transporter for that reason.

 

[pood]

It is unproven that we will ever upload consciousness. I am skeptical. Uploading assumes consciousness is substrate independent. It may well not be. So-called artificial intelligence today is totally void of consciousness. Computers and brains function totally differently. We do not know how minds arise from brains. We do not know whence qualia arise. This is the hard problem of conscisousness.

If a physical spaceship with humans aboard could be propelled to a significant fraction of light speed, outbound travelers will be time-dilated and length contracted and could arrive at very distant stars in arbitrarily short times as measured by the ship’s proper time. Unfortunately it would be a one-way trip. If they returned to earth they would find that eons had passed and all their loved ones are long dead. In any case the energy requirements for propelling a physical ship to relativistic velocities are immense and will likely always remain beyond reach.

What else? Perhaps space warps, which are being studied. I won’t hold my breath.

Most likely we will destroy ourselves, as we are already doing with global warming, resource depletion and population overshoot. I suspect that in another century or so population will be greatly reduced, industrial civilization will have collapsed and our descendents will be struggling to feed themselves.