Do you think any aliens exist in the universe?

[steve_bank]

Ir is easy to get to another star. Just turn on a light on the back of your spaceship and away you go.

It helps to have a good soundtrack coming for all around you in space.

 

[DBT]

Our earth will probably not remain earthlike for much longer, cosmologically speaking.

Perhaps we have about a billion years before the sun roasts the earthlings.

…so its hospitable-to-life lifespan is like, over 80% spent?
That’s kinda how I feel lately. Maybe not 4 billion years old, but at least a billion or two.

Hospitable to macroscopic life, it's more like 99% done.

Indirectly, this is very good news. There must be something ridiculously low probability in the path from the first life to a starfaring civilization, the question is whether it is behind us or in front of us. And that 99% figure suggests that time might be an important factor--that most planets don't reach intelligence in time.

OTOH we have only been a mostly technological population for only a few tens of thousands of years as far as we know. If impactors or volcanoes don’t set us back or wipe us out, we might yet be able to rape and plunder the entire cosmic neighborhood. Even a million years would probably suffice to get pretty good at it.
And from there, the sky’s the - oh wait.
Never mind!
I learned some good news today though;
If we survive the first close encounter with Andromeda in about a billion years, there is only a 50% chance of a final galactic merger within 10 billion years, and even if that happens it is unlikely to effect our solar system - which will probably just be one bigass red giant by then, and therefore very hard to effect.

The chance that nature is going to wipe us out before we reach the stars is pretty close to nil. That would require extremely bad luck. The question is whether the filter is that intelligent life destroys itself before reaching the stars.

Reaching the stars seems to be practically impossible.

 

[Elixir]

Reaching the stars seems to be practically impossible.

IKR? It’s hard enough to get their phone numbers, and then it goes to VM. Sometimes you have to call and call and call …

 

[Loren Pechtel]

Our earth will probably not remain earthlike for much longer, cosmologically speaking.

Perhaps we have about a billion years before the sun roasts the earthlings.

A lot less than that. Earth has only about 50 million years left where it can compensate for the sun growing hotter over the eons. At that point CO2 levels peg low and the mercury starts rising. Life might hang on to the billion year mark but it will be extremeophiles, nothing like us. And that's the best case estimate in which the oceans have escaped into space. If they haven't it will be much, much worse. (Water molecules that get high enough into the atmosphere will photodisassociate and Earth can't hold hydrogen very well. This is currently a very slow trickle because the cold keeps the water down lower.)

Your numbers do not agree with the research on the subject. See, for example, this paper (https://arxiv.org/pdf/2409.10714), which I cited earlier, and the references therein in Table 1.

That's talking about the survival of any life, not of macroscopic life.

Are you sure about that? Did you even read the first sentence of the abstract?

Approximately one billion years (Gyr) in the future, as the Sun brightens, Earth’s carbonate-silicate cycle is expected to drive CO2 below the minimum level required by vascular land plants, eliminating most macroscopic land life.

That doesn't mean that it will have survived to that point. The thing is it will be much warmer then. Major evolutionary changes will be needed for anything beyond the extremeophiles to be around then--and remember that evolution proceeds at a rate set by generations, not years. That's why germs rapidly evolve to get around our defenses while we have little evolution towards resisting them.

 

[Loren Pechtel]

The chance that nature is going to wipe us out before we reach the stars is pretty close to nil. That would require extremely bad luck. The question is whether the filter is that intelligent life destroys itself before reaching the stars.

I foresee that man will wipe out his own capability to reach any stars for long enough that nature has a real good chance of beating them to the punch. Reaching stars is going to take stability on a scale no human society has ever exhibited.

Technology makes smaller and smaller groups capable of accomplishing any given objective. Space flight used to be something that could only be accomplished at major government scale. Now the majority of launches are private and the government buys capacity as they are not remotely competitive. If we don't collapse the same thing will eventually happen--star flight will become something a group can do.

 

[DBT]

Reaching the stars seems to be practically impossible.

IKR? It’s hard enough to get their phone numbers, and then it goes to VM. Sometimes you have to call and call and call …

At least they have agents.

 

[Elixir]

Our earth will probably not remain earthlike for much longer, cosmologically speaking.

Perhaps we have about a billion years before the sun roasts the earthlings.

A lot less than that. Earth has only about 50 million years left where it can compensate for the sun growing hotter over the eons. At that point CO2 levels peg low and the mercury starts rising. Life might hang on to the billion year mark but it will be extremeophiles, nothing like us. And that's the best case estimate in which the oceans have escaped into space. If they haven't it will be much, much worse. (Water molecules that get high enough into the atmosphere will photodisassociate and Earth can't hold hydrogen very well. This is currently a very slow trickle because the cold keeps the water down lower.)

Your numbers do not agree with the research on the subject. See, for example, this paper (https://arxiv.org/pdf/2409.10714), which I cited earlier, and the references therein in Table 1.

That's talking about the survival of any life, not of macroscopic life.

Are you sure about that? Did you even read the first sentence of the abstract?

Approximately one billion years (Gyr) in the future, as the Sun brightens, Earth’s carbonate-silicate cycle is expected to drive CO2 below the minimum level required by vascular land plants, eliminating most macroscopic land life.

That doesn't mean that it will have survived to that point. The thing is it will be much warmer then. Major evolutionary changes will be needed for anything beyond the extremeophiles to be around then--and remember that evolution proceeds at a rate set by generations, not years. That's why germs rapidly evolve to get around our defenses while we have little evolution towards resisting them.

Maybe if we arrange a ring of about a thousand rocket motors around the earth’s equator, all buried in the ground or affixed to the seabed with the exhausts going straight up, we could fire them in sequence, each one at local solar noon. Keep doing that a few days a week over a period of hundreds of millennia and we could move the earth further from the sun. It might buy us a little time.

Eventually we’d have to blast Mars out of the way of course, but doing that to Jupiter when the time comes, would be at the limit of even humans’ destructive capability.

 

[aupmanyav]

Maybe if we arrange a ring of about a thousand rocket motors around the earth’s equator, all buried in the ground or affixed to the seabed with the exhausts going straight up, we could fire them in sequence, each one at local solar noon. Keep doing that a few days a week over a period of hundreds of millennia and we could move the earth further from the sun. It might buy us a little time.

That is not necessary. Once the space ship is nearly out of Earth's gravity, no boost is required unless you want the spaceship to move faster. It goes by itself since there is nothing to stop its move. That is why the research is going on for ion rockets. They will weigh very little and add to the speed of the ship step by step. But even then the stellar distances are extremely huge. It will take generations of astronauts on the ship, born, raised and trained to handle the ship before its gets anywhere near Proxima Centauri - 25 trillion miles. Same if they do not like the place and want to come back.
It will be a multi-generational journey.

 

[Elixir]

Maybe if we arrange a ring of about a thousand rocket motors around the earth’s equator, all buried in the ground or affixed to the seabed with the exhausts going straight up, we could fire them in sequence, each one at local solar noon. Keep doing that a few days a week over a period of hundreds of millennia and we could move the earth further from the sun. It might buy us a little time.

That is not necessary. Once the space ship is nearly out of Earth's gravity, no boost is required unless you want the spaceship to move faster.

WHAT “spaceship”?
I’m talking about moving the earth out of harm’s way - buying a couple million extra years perhaps.

 

[aupmanyav]

WHAT “spaceship”?
I’m talking about moving the earth out of harm’s way - buying a couple million extra years perhaps.

Oh, my bad. I was not smart enough to understand your scheme. Suggest it to Trump or Musk. The research should start as soon as possible. They would not care about what Russia and China think about it.

 

[Elixir]

They would not care about what Russia and China think about it.

It would only effect equatorial territories … They’re already too hot, so they will be pleased to help with the effort.

 

[DBT]

Maybe if we arrange a ring of about a thousand rocket motors around the earth’s equator, all buried in the ground or affixed to the seabed with the exhausts going straight up, we could fire them in sequence, each one at local solar noon. Keep doing that a few days a week over a period of hundreds of millennia and we could move the earth further from the sun. It might buy us a little time.

That is not necessary. Once the space ship is nearly out of Earth's gravity, no boost is required unless you want the spaceship to move faster. It goes by itself since there is nothing to stop its move. That is why the research is going on for ion rockets. They will weigh very little and add to the speed of the ship step by step. But even then the stellar distances are extremely huge. It will take generations of astronauts on the ship, born, raised and trained to handle the ship before its gets anywhere near Proxima Centauri - 25 trillion miles. Same if they do not like the place and want to come back.
It will be a multi-generational journey.

A huge investment for possibility little return. Especially if none of the planets are habitatable.

 

[Loren Pechtel]

Maybe if we arrange a ring of about a thousand rocket motors around the earth’s equator, all buried in the ground or affixed to the seabed with the exhausts going straight up, we could fire them in sequence, each one at local solar noon. Keep doing that a few days a week over a period of hundreds of millennia and we could move the earth further from the sun. It might buy us a little time.

That is not necessary. Once the space ship is nearly out of Earth's gravity, no boost is required unless you want the spaceship to move faster.

WHAT “spaceship”?
I’m talking about moving the earth out of harm’s way - buying a couple million extra years perhaps.

That's not how to go about it. Earth has an atmosphere that we care about and Earth has seismic activity. And what's your fuel?

No, put your rocket elsewhere. Neptune is a likely candidate. Yes, there's nothing to mount it to--it floats. There's your fuel: fuse that hydrogen. You point the rocket at the sky, it pushes deeper into the atmosphere, the buoyancy pushes back and the planet moves. Very slow, but it does. You bring it around, it overtakes Earth far enough away that the tides aren't too problematic. It loses a little energy, Earth gains it. Maintain a resonance so it keeps coming past and giving a tug. It's extremely slow but that's fine, you just want to creep out as the habitable zone moves outward. Since it's not anchored you're free to reposition it as needed and don't need a whole bunch of extra rockets that aren't pointing in the right direction.

 

[Loren Pechtel]

Maybe if we arrange a ring of about a thousand rocket motors around the earth’s equator, all buried in the ground or affixed to the seabed with the exhausts going straight up, we could fire them in sequence, each one at local solar noon. Keep doing that a few days a week over a period of hundreds of millennia and we could move the earth further from the sun. It might buy us a little time.

That is not necessary. Once the space ship is nearly out of Earth's gravity, no boost is required unless you want the spaceship to move faster. It goes by itself since there is nothing to stop its move. That is why the research is going on for ion rockets. They will weigh very little and add to the speed of the ship step by step. But even then the stellar distances are extremely huge. It will take generations of astronauts on the ship, born, raised and trained to handle the ship before its gets anywhere near Proxima Centauri - 25 trillion miles. Same if they do not like the place and want to come back.
It will be a multi-generational journey.

A huge investment for possibility little return. Especially if none of the planets are habitatable.

1) I don't think a civilization that can push a rocket to the stars will be all that interested in planets other than as raw materials. The sci-fi idea of taking your tin can to habitable worlds makes no sense unless you have some sort of FTL and nearly free stardrive.

2) Realistically, there's only one reason people will take a slowboat to the stars: they want to set up their own community rather than be part of the general one.

 

[Swammerdami]

That is not necessary. Once the space ship is nearly out of Earth's gravity, no boost is required unless you want the spaceship to move faster. It goes by itself since there is nothing to stop its move.

The escape velocity from Earth is approximately 11.2 kilometers per second

The escape velocity needed to leave the solar system, starting from Earth's orbit, is approximately 42.1 kilometers per second.

... But even then the stellar distances are extremely huge. It will take generations of astronauts on the ship, born, raised and trained to handle the ship before its gets anywhere near Proxima Centauri - 25 trillion miles. Same if they do not like the place and want to come back.
It will be a multi-generational journey.

Some fun sci-fi novels based on this theme. In one, the inhabitants of a huge starship have forgotten their mission, or treat it as pure myth like Genesis.

 

[aupmanyav]

Some fun sci-fi novels based on this theme. In one, the inhabitants of a huge starship have forgotten their mission, or treat it as pure myth like Genesis.

^^ Great fun and conflicts on the ship about 'Truth'.
We will never change.

 

[Shadowy Man]

Our earth will probably not remain earthlike for much longer, cosmologically speaking.

Perhaps we have about a billion years before the sun roasts the earthlings.

A lot less than that. Earth has only about 50 million years left where it can compensate for the sun growing hotter over the eons. At that point CO2 levels peg low and the mercury starts rising. Life might hang on to the billion year mark but it will be extremeophiles, nothing like us. And that's the best case estimate in which the oceans have escaped into space. If they haven't it will be much, much worse. (Water molecules that get high enough into the atmosphere will photodisassociate and Earth can't hold hydrogen very well. This is currently a very slow trickle because the cold keeps the water down lower.)

Your numbers do not agree with the research on the subject. See, for example, this paper (https://arxiv.org/pdf/2409.10714), which I cited earlier, and the references therein in Table 1.

That's talking about the survival of any life, not of macroscopic life.

Are you sure about that? Did you even read the first sentence of the abstract?

Approximately one billion years (Gyr) in the future, as the Sun brightens, Earth’s carbonate-silicate cycle is expected to drive CO2 below the minimum level required by vascular land plants, eliminating most macroscopic land life.

That doesn't mean that it will have survived to that point. The thing is it will be much warmer then. Major evolutionary changes will be needed for anything beyond the extremeophiles to be around then--and remember that evolution proceeds at a rate set by generations, not years. That's why germs rapidly evolve to get around our defenses while we have little evolution towards resisting them.

Can you provide the analysis that led you to conclude that life (other than “extremophiles”) has only 50 million years left due to the increase of solar luminosity?

You provided a quantitative assessment. Can you back that up or is it just pure speculative opinion?

 

[Elixir]

Maybe if we arrange a ring of about a thousand rocket motors around the earth’s equator, all buried in the ground or affixed to the seabed with the exhausts going straight up, we could fire them in sequence, each one at local solar noon. Keep doing that a few days a week over a period of hundreds of millennia and we could move the earth further from the sun. It might buy us a little time.

That is not necessary. Once the space ship is nearly out of Earth's gravity, no boost is required unless you want the spaceship to move faster.

WHAT “spaceship”?
I’m talking about moving the earth out of harm’s way - buying a couple million extra years perhaps.

That's not how to go about it. Earth has an atmosphere that we care about and Earth has seismic activity. And what's your fuel?

No, put your rocket elsewhere. Neptune is a likely candidate. Yes, there's nothing to mount it to--it floats. There's your fuel: fuse that hydrogen. You point the rocket at the sky, it pushes deeper into the atmosphere, the buoyancy pushes back and the planet moves. Very slow, but it does. You bring it around, it overtakes Earth far enough away that the tides aren't too problematic. It loses a little energy, Earth gains it. Maintain a resonance so it keeps coming past and giving a tug. It's extremely slow but that's fine, you just want to creep out as the habitable zone moves outward. Since it's not anchored you're free to reposition it as needed and don't need a whole bunch of extra rockets that aren't pointing in the right direction.

Some people just can’t accept the simple solution, and have move heaven and earth just to move one ball of dirt further from the fire. Sheesh! Putting Neptune back where it belongs would be no mean trick!
Also I have a feeling that when all the orbital math is worked out, you’re gonna freeze us all.

 

[Jarhyn]

I’m more inclined to think alien biochemistries would be so different from one another that they couldn’t affect one another for good or ill, and certainly one could not and most assuredly would not want to eat the other. If speculative silicon life forms existed, for example, I imagine to us they would be like living rocks, and nobody wants to eat a rock.

Even a biochemistry that uses the same chemical elements as ours is likely to be very different. Some of our proteins' amino acids are prebiotic, while others aren't, and the latter ones are likely later add-ons.

The most plausible hypothesis to date for the origin of the DNA - RNA - protein system is the RNA-world hypothesis, which states that RNA was both information carrier and enzyme, "ribozyme". DNA is a modification of RNA that only does primary copies of genetic information, with messenger RNA being secondary copies. Proteins are assembled on ribosomes, RNA-protein complexes with the RNA parts being the primary working parts. So both DNA and sequenced proteins are a result of the RNA world.

About RNA itself, while the nucleobases are mostly prebiotic, the ribose maybe wasn't. It's hard to make sugars with prebiotic chemistry, and when one tries, one gets mixtures of every possible asymmetry of each molecule. While protein amino acids have one asymmetric carbon atom in them, ribose has three.

I've seen speculation that ribose wasn't the first, that it had some predecessor, though it is hard to pin down what that predecessor might be.

If that is the case, then it means that the possible biochemistries of carriers of heredity is broader than in our biota.

More speculatively, I wonder whether their arrow of time would be the same as ours. The block world picture of space time posits that the future exists along with the past, and we know that at the microscopic level processes are time symmetric, with no arrow of time. Could it be possible that an alien intelligence remembers the future? This was the theme of the sci-fi flick Arrival, which left any number of philosophical riddles to ponder include the old standby of free will.

I find that implausible, because the direction of time is embedded in our Universe's macroscopic physics. It's something like the problem of how one gets from quantum to classical mechanics, it seems to me. Both of them are problems that are much more difficult to solve than what they might seem like at first.

I would be willing to bet that most life is toxic in some chemical way to most other life, of life forms of distant planets.

Even life of the same species is subtly toxic in internal ways, generally, for earth.

I sometimes speculate about a lovecraftian organism that engineers originations of life and even fosters enclaves of various kinds on moons, and then repeatedly throwing examples into enclaves of their own form of life in a steady trickle, until the aliens are no longer bothered chemically by those systems of life: a sort of one-way evolution, to be adaptable to every form of life as they can.

They then go out into the universe attached as spores to objects with interstellar velocities, to attach and hatch and survive in the rugged outlands of a system where the gravity is low and energy is meager and time is slow, eventually seeking legrange points and sufficiently large belt objects until their slow biological or electromechanical processes have the accreted material and processing power to make inroads into terrestrial bodies capable of supporting their form of life, which would probably be universally toxic in every way to us, after doing the same for some thousands of years using earth life.

But that's like, cosmic horror level science fiction. It's actually entirely plausible, but unlikely.

Honestly, I expect that the name of this life form is "Earthers" and we will be a terror and a curse on the universe of we ever escape this rock, because this could as well be used as a roadmap in the same way as The Handmaid's Tale.

We exist at the dawn of life in our universe. It's hard to imagine other life getting an earlier start than life around Sol did. We had few mishaps, got plenty of interstellar material from plenty of weird events to make planets and it only took several billion years after the last time a star went "pop" and the gravity well here went a bit *fuzzy*.

Honestly, given how long life bearing planets are going to be precipitated by various stellar events, we're right near "the beginning" even if there were a big rip some time in our perceptual future that isolates us...

The amount of time it takes to evolve whatever various forms of life as various chemical signatures observed planets would imply is immense, especially to a level where such warfare would be possible or even advisable. They would have to appear early and plan the beach-head event.

Engineering how from our level of technology forward to "where it's going" would only take a few hundred years at most without a dark age, perhaps only a few thousand with one or a scant 100m if we managed to apocalypse most life this time around.

It would take a while before we ever encountered a life form that was our equal, and we could put down shop just around anywhere at that point, since we would plan out our game often before other forms of life first precipitated.

But humans aren't known well for their forward planning capabilities.

We're probably going to apocalypse ourselves trying to figure out how to travel whole-human in an interstellar air bottle, and whatever lifeform I described will evolve against the ashes of the life they find here and move in.

 

[aupmanyav]

It would take a while before we ever encountered a life form that was our equal, ..

I don't think it will ever happen. The constraints such as we have, will be there for those people also.