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willstaruss22
2013-Oct-10, 04:20 PM
There are 3 scenarios i see of an advanced race of aliens visiting Earth.
1. They have indirect contact and merely observe our way of life.
2. They have direct contact and are hostile they want our resources and want to exterminate any life that may pose a threat in the future.
3 They have direct contact and are friendly and want to teach us their ways of life and culture and would understand our way of life and culture. They might welcome us into their society or wait until we reach a maturity within our own society.

Would any of these scenarios make sense?

Noclevername
2013-Oct-10, 04:31 PM
Scenario #1: Makes the most sense of the three.

Scenario #2: The only resource they could find here that they could not get or make far more easily closer to their home, is us. Human beings, and our unique cultures and concepts, if any. So combining "gather resources" with "wipe us out" makes no sense. Considered as two separate scenarios, far easier to get our songs and stories through communication rather than travelling the immense distances of space. As for wiping us out, sending a near-C impactor will take care of pest control without them coming here in person.

Scenario #3: you seem to be assuming there are social maturity "levels" that transcend species. Life on Earth doesn't work like that, why would alien life? Least likely.

ADDED: Scenario #4: they communicate from a distance or via probe relay, out of curiosity but we do not unite cultures due to mutual fundamental differences. Just learning to communicate may be a major challenge.

willstaruss22
2013-Oct-10, 04:37 PM
The hostile part again maybe they would want to terraform every planet that could potetially resemble theirs in order for their species to occupy every corner of the galaxy. Meaning they would terraform Earth to match what their home world is. I realize that is way out there. Not doing it for survival purposes but for strategic purposes. Your right they would be able to find resources in their own solar system.

ravens_cry
2013-Oct-10, 04:39 PM
Number three is almost the most scary. "Oh, those benighted apelings are so primitive. We must raise them up to be model citizens of the galaxy. It is for their own good after all."
A cursory glance of our own history shows what a chilling thought that is.

willstaruss22
2013-Oct-10, 04:40 PM
Yes that is what we have done and it is scary either be like us or dont exist.

Noclevername
2013-Oct-10, 04:42 PM
The hostile part again maybe they would want to terraform every planet that could potetially resemble theirs in order for their species to occupy every corner of the galaxy. Meaning they would terraform Earth to match what their home world is. I realize that is way out there. Not doing it for survival purposes but for strategic purposes.

Since finding a world that is a twin to theirs is not guaranteed, if they really want to fill the galaxy they would learn to build space habitats; planets then become unnecessary. They could inhabit red dwarf star systems, the most common and long-lived suns. And if they can travel between stars, they already have the know-how to build such habitats.

ravens_cry
2013-Oct-10, 05:40 PM
Yes that is what we have done and it is scary either be like us or dont exist.
Commas, dude. They are the difference between "No, pardon possible" and "No pardon possible."
Of course, they don't have to threaten it in exactly the terms you describe. They just have to make sure we remain in this solar system, think of it as a reserve for wild species, and let nature take its course.

Elukka
2013-Oct-10, 08:33 PM
Number three is almost the most scary. "Oh, those benighted apelings are so primitive. We must raise them up to be model citizens of the galaxy. It is for their own good after all."
A cursory glance of our own history shows what a chilling thought that is.
I feel the fact we have no material wealth (or land) that is of interest to them makes it a pretty different situation.

Jens
2013-Oct-10, 11:02 PM
Number three is almost the most scary. "Oh, those benighted apelings are so primitive. We must raise them up to be model citizens of the galaxy. It is for their own good after all."
A cursory glance of our own history shows what a chilling thought that is.

I don't really see the parallel. You are talking about our interactions with members of our own species. Consider maybe our relationship with dolphins. We know they're highly intelligent, but we can't communicate with them in a way that would make the idea of educating them make any sense.

Regarding the question, I think the first would be most likely. If we were to find evidence of say intelligent jellyfish-like creatures floating high in the clouds of Jupiter, I think that's the approach we would take, so I can only assume that would be most likely for others as well.

ravens_cry
2013-Oct-11, 12:07 AM
I feel the fact we have no material wealth (or land) that is of interest to them makes it a pretty different situation.

I don't really see the parallel. You are talking about our interactions with members of our own species. Consider maybe our relationship with dolphins. We know they're highly intelligent, but we can't communicate with them in a way that would make the idea of educating them make any sense.

Nope, we just kill them or capture them to put in aquatic zoos. The thing is though, any intelligent species is a potential competitor. If they can make us 'good galactic citizens', that's less of a worry for them. After all, no one wants another Berserker outbreak.

Noclevername
2013-Oct-11, 01:09 AM
Nope, we just kill them or capture them to put in aquatic zoos. The thing is though, any intelligent species is a potential competitor. If they can make us 'good galactic citizens', that's less of a worry for them. After all, no one wants another Berserker outbreak.
Assuming they see us as intelligent.

ravens_cry
2013-Oct-11, 02:44 AM
Assuming they see us as intelligent.
That is the assumption of number three, yes.

Noclevername
2013-Oct-11, 04:58 AM
That is the assumption of number three, yes.

OK, got it. For some reason I thought you were talking about the invasion scenario. That'll teach me to read the whole thread before replying! :doh:

I typically associate the word "welcome" with non-aggressive invitation, but I guess it has different connotations for different people.

Jens
2013-Oct-12, 12:24 AM
. If they can make us 'good galactic citizens', that's less of a worry for them. After all, no one wants another Berserker outbreak.

To be honest, I don't know what you're talking about but I have a feeling it may be fictional.

Spacedude
2013-Oct-12, 02:45 PM
1. They have indirect contact and merely observe our way of life.

That would be my choice since obviously we would be considered extremely inferior and hardly worth the effort. Besides, after observing us for just a very short time they'd see that humans on the whole would not be mentally or emotionally able to handle direct contact.....perhaps even those of us who think that we could handle it could not do so. It will not even remotely resemble Vulcans knocking on our door as sci-fi entertainment would have us believe.

ravens_cry
2013-Oct-12, 03:28 PM
To be honest, I don't know what you're talking about but I have a feeling it may be fictional.
Berserkers are a hypothesis to explain the Fermi paradox. Basically, the idea is there is a life so xenophobic, they wipe out all other minds (or, in more extreme cases, life) if they make so much as a cosmic peep.
Hence why no one is saying anything. They either have and have been with wiped out or are huddling scared in the dark.

Noclevername
2013-Oct-12, 04:07 PM
The Fermi "paradox" is more easily explained by: ETI is too far away, doesn't have obvious "tells" that we can detect, or doesn't exist.

ravens_cry
2013-Oct-12, 04:21 PM
The Fermi "paradox" is more easily explained by: ETI is too far away, doesn't have obvious "tells" that we can detect, or doesn't exist.

Only the last really explains it as the Fermi paradox is not just asking why we haven't detected them but why they aren't in this solar system, as even a quite modest rate of galactic expansion in vessels far slower than the speed of light would mean all suitable stars would be colonized within a quite short order in relation to the age of the galaxy. Intelligent life that escapes its home star's cradle would have to be rarer than one to the galaxy for the 'too far away' or 'no tells' idea to work.
Now, I am not saying I agree with the Berserker explanation, but it would certainly be a motive for an interstellar civilisation to want to 'civilize' other races.

Noclevername
2013-Oct-12, 04:26 PM
Only the last really explains it as the Fermi paradox is not just asking why we haven't detected them but why they aren't in this solar system, as even a quite modest rate of galactic expansion in vessels far slower than the speed of light would mean all suitable stars would be colonized within a quite short order in relation to the age of the galaxy. Intelligent life that escapes its home star's cradle would have to be rarer than one to the galaxy for the 'too far away' or 'no tells' idea to work.

You are making a number of assumptions there: That ETI's have the capacity for interstellar travel, that they are expansive, that they are much older than us, and that they colonize star systems like ours. Without all of those assumptions being true, your scenario would fall apart.

Also, 'less than one per galaxy' IS 'too far away'.

ravens_cry
2013-Oct-12, 06:22 PM
Yes, I admit those are assumptions, though I don't see how our star couldn't be suitable. If it's too hot, be farther away than you would otherwise, if it's too cold, move closer. If you don't like the spectra, stay inside and use the energy to power lights of the right spectra.
I myself have mentioned the (albeit very depressing) idea that no one leaves the cage, that perhaps the hurdles of interstellar colonization are too much, but given that there second generation stars are over 13 billion years old, there is more than enough time for a single species to develop in the time we took and to colonize the stars in the galaxy (and likely beyond) without being very 'expansionist' beyond having interstellar flight at all.

Noclevername
2013-Oct-12, 09:08 PM
I myself have mentioned the (albeit very depressing) idea that no one leaves the cage, that perhaps the hurdles of interstellar colonization are too much, but given that there second generation stars are over 13 billion years old, there is more than enough time for a single species to develop in the time we took and to colonize the stars in the galaxy (and likely beyond) without being very 'expansionist' beyond having interstellar flight at all.

Maybe we're atypical. We know our solar system is.

Perhaps there's more to developing sapient intelligence than time. And perhaps there's more than opportunity needed for large scale colonization; it might be that unrestrained growth is something only young civilizations engage in, or it might be that they are slower than we imagine and just haven't reached here yet. Perhaps they avoid systems that already have native life, out of fear of contamination (ours or theirs!) or for some other reason.

There's a large spectrum of possibilities between "no one leaves the nest ever" and "our neighbors just haven't come here yet".

Noclevername
2013-Oct-13, 06:58 AM
Even if very old spacefaring ETI civilizations do exist in our galaxy, and even if they have failed to colonize other stars than their home, that doesn't mean it's necessarily physically impossible, just that it's enormously hard and they haven't done it. We could be trend-setters!

Noclevername
2013-Oct-13, 09:23 AM
Here's a premise; ETIs that are able and willing to develop starships need a large enough population and social organization to build industrial civilizations, and (since the OP specifies aliens visiting in person) enough wanderlust and exploratory nature to risk life and limb by throwing themselves out into space.

Now, the large population means that like humans, they reproduce prolifically; The social nature means they are social animals who can work in large groups, but the explorer nature means they probably have some instinct to go where no ET has gone before, IE, into unpopulated "wild" areas. These three drives are somewhat contradictory even in us. In animal species, or even primitive sapients such as hunter-gatherers, there is a balance; not too much population growth at a time. But once you become "civilized", increased production and medicine allow for huge population booms. Therefore a society may outstrip its resources and living space in a relatively short order, leading to social conflicts, resource fights, and all the war and revolution that entails, and a civilization falls.

Think of the Moties in The Mote In God's Eye. Their obligatory reproduction is an extreme exaggeration, but even with just our own reproductive instincts we're already outgrowing our limits here on Earth. We know from our history that human empires rise and fall, with dark ages in between. But now thanks to the same scientific and technological development that contributed to such overcrowding in the first place, and that can potentially lead us into space, we can and have developed weapons that can prune our population considerably more; perhaps even too low to maintain an industrial society, which must be slowly rebuilt. Suppose now that this boom-and-bust cycle is an innate quality of beings similar enough to us to develop along a path leading to a space age, for the reasons given above.

There are two options; to continue to boom-and-bust and be knocked back to earlier states again and again, or learn to control the reproduction and population growth to sustainable levels. Thus those who colonize space, and perhaps someday to other stars, will not feel the need to fill every available corner of the galaxy; any who attempt to do so without such reproductive discipline will themselves fall victim to the population boom-and-bust, and in space a dark age means no life support. Those who go to the stars will do so, not for lebensraum but out of curiosity, boredom, for adventure, to seek out other minds, a desire to have a back-up location for their kind, or for other reasons besides unrestrained growth.

Now, this is not necessarily what I think will happen, but it's one potential explanation for why the galaxy is not already full to the brim with advanced ETs, besides the ones already given. It may be inherent in the way what we call "civilization" develops. There may be other intelligences that do not follow this pattern but consequently lack the drive and capability for interstellar travel. They may not be tool-users, or they may lack the creativity to develop technology, or they may be too territorial to leave their homeworld. They may be post-biological, "colonizing" virtual worlds instead of physical space. They could be immortal, and no longer have a need to reproduce, or it might give them a long-view perspective that allows them to resist the temptation to spread across the galaxy.

All we do know is, we haven't found any signs of them out there.

Noclevername
2013-Oct-13, 01:51 PM
Now if an ET starship does show up tomorrow, and demands our unconditional surrender, we'd have little way to resist them. They wouldn't even have to point their main drive at us and blaze away, they could stand off a few AU and just toss dinosaur killer asteroids at us. The most we could do is play along and hope that we can someday learn some weakness or leverage. After all, ruling a whole planet takes more than the threat of death from above.

Maybe if they are sufficiently inattentive we could take a page from the novel Footfall and secretly build Orion pulse-drives, except instead of one we'd need a fleet. Half as a battle fleet loaded for nuclear bear, half as lifeboats to flee the other way while the enemy is distracted by fighting. Send small groups out across the Solar System and hope that the fighters do enough damage to prevent the invaders from going after them. Then hope again that the refugees can build a survivable home using only what they bring with them or find along the way.

That's if they have one starship. If they bring a fleet we're screwed.

absael
2013-Oct-13, 07:05 PM
Here's another scenario: they identify a few key people to make contact with, for the purpose of accelerating our technological process. Perhaps their intentions are entirely altruistic; they want to give us advanced medical technologies and drugs to reduce suffering, for example. Or, perhaps their motives are a bit less benign, and they want to influence us for some other reason.

This may sound far-fetched (even in the context of this discussion), but I think it's more likely than a scenario in which they make their presence widely known, given that, IMO, this would be so disruptive that the negative effects would likely outweigh any benefits. For us, anyway.

Noclevername
2013-Oct-13, 07:11 PM
Here's another scenario: they identify a few key people to make contact with, for the purpose of accelerating our technological process. Perhaps their intentions are entirely altruistic; they want to give us advanced medical technologies and drugs to reduce suffering, for example. Or, perhaps their motives are a bit less benign, and they want to influence us for some other reason.

This may sound far-fetched (even in the context of this discussion), but I think it's more likely than a scenario in which they make their presence widely known, given that, IMO, this would be so disruptive that the negative effects would likely outweigh any benefits. For us, anyway.

How could they avoid being discovered? Interstellar travel would be enormously noticeable, given the massive amounts of energy expended.

absael
2013-Oct-13, 07:59 PM
How could they avoid being discovered? Interstellar travel would be enormously noticeable, given the massive amounts of energy expended.

I don't know; AFAIK it hasn't been demonstrated that interstellar travel within a reasonable time frame is even possible (especially given the distance at which we might "reasonably" expect to find intelligent beings), so as long as we're making that leap, I reserve the right to make another one :)

Noclevername
2013-Oct-13, 08:09 PM
I don't know; AFAIK it hasn't been demonstrated that interstellar travel within a reasonable time frame is even possible (especially given the distance at which we might "reasonably" expect to find sentient beings), so as long as we're making that leap, I reserve the right to make another one :)

Interstellar travel may be possible, there's no law of physics that prevents it. What constitutes reasonable time frames vary depending on what life supporting/preserving technologies the travelers have going for them; generation ships, cryogenic suspension, or life extension, as well as the acceleration rates and delta-V of their vessel. Relativistic time dilation may even play a role in making the trip subjectively shorter.

Arriving undetected in our Solar System, however, is definitely not possible by any known physics. It breaks the laws of thermodynamics to have a massive power expenditure without hugely detectable energy output.

absael
2013-Oct-13, 08:25 PM
Interstellar travel may be possible, there's no law of physics that prevents it. What constitutes reasonable time frames vary depending on what life supporting/preserving technologies the travelers have going for them; generation ships, cryogenic suspension, or life extension, as well as the acceleration rates and delta-V of their vessel. Relativistic time dilation may even play a role in making the trip subjectively shorter.

Arriving undetected in our Solar System, however, is definitely not possible by any known physics. It breaks the laws of thermodynamics to have a massive power expenditure without hugely detectable energy output.

Would the power output have to be massive as they approach the solar system? They have to start slowing down well before they get here anyway. By my calculations, if they reduce their speed relative to Earth to 0.001c by the time they reach the outer fringes of the solar system, they could finish the journey in a couple of years.

Noclevername
2013-Oct-13, 08:34 PM
Would the power output have to be massive as they approach the solar system? They have to start slowing down well before they get here anyway. By my calculations, if they reduce their speed relative to Earth to 0.001c by the time they reach the outer fringes of the solar system, they could finish the journey in a couple of years.

Yes, and they'll still have .001c relative velocity to shed. Which requires either thrust (radiates heat) a solar sail (big bright light and heat reflected towards the inner Solar system, IE us) or a magnetic drag-chute against the solar wind (generates cyclotron radiation, resulting in large radio frequency emissions).

Plus there's all the slowing down they did before reaching the heliopause, which would be visible from a very long distance.

absael
2013-Oct-13, 09:46 PM
Yes, and they'll still have .001c relative velocity to shed. Which requires either thrust (radiates heat) a solar sail (big bright light and heat reflected towards the inner Solar system, IE us) or a magnetic drag-chute against the solar wind (generates cyclotron radiation, resulting in large radio frequency emissions).

Plus there's all the slowing down they did before reaching the heliopause, which would be visible from a very long distance.

Are we looking for these type of energy signatures in interstellar space? What are the odds that we would actually detect it? Is it possible to come up with more-or-less real numbers to try to figure this out?

And even if we did detect it, we wouldn't know what it was (we might guess that it could be a spacecraft slowing to enter the solar system, but this is so unlikely that we certainly wouldn't assume it to be the case). And this could very well be good enough for their purposes; even if they come in peace, they may decide that the benefits that they're going to bring us are such that it's worth raising a mild suspicion. This sort of thing wouldn't have a calamitous effect on our society.

Regarding their energy expenditure within the solar system, they have 10 billion miles to decelerate. It seems to me that, if they adjust their deceleration rate such that they're expending less and less energy as they get closer, it should be possible to approach undetected (we can also assume a somewhat slower initial velocity at the heliopause). They could even shut off the engines entirely and coast once they get close.

Jens
2013-Oct-14, 02:06 AM
Here's another scenario: they identify a few key people to make contact with, for the purpose of accelerating our technological process. Perhaps their intentions are entirely altruistic; they want to give us advanced medical technologies and drugs to reduce suffering, for example.

Medical technology seems possible, perhaps they would teach us new scanning techniques like MRI or PET. But in terms of drugs, whatever they have would be irrelevant to us. We would probably appreciate blood thinning drugs, but they probably wouldn't even have blood the way we do. Our blood is loosely derived from seawater.

Noclevername
2013-Oct-14, 02:58 AM
Are we looking for these type of energy signatures in interstellar space? What are the odds that we would actually detect it? Is it possible to come up with more-or-less real numbers to try to figure this out?

And even if we did detect it, we wouldn't know what it was (we might guess that it could be a spacecraft slowing to enter the solar system, but this is so unlikely that we certainly wouldn't assume it to be the case). And this could very well be good enough for their purposes; even if they come in peace, they may decide that the benefits that they're going to bring us are such that it's worth raising a mild suspicion. This sort of thing wouldn't have a calamitous effect on our society.

Regarding their energy expenditure within the solar system, they have 10 billion miles to decelerate. It seems to me that, if they adjust their deceleration rate such that they're expending less and less energy as they get closer, it should be possible to approach undetected (we can also assume a somewhat slower initial velocity at the heliopause). They could even shut off the engines entirely and coast once they get close.

10 billion miles is nothing to the blazing glow of a starship engine. And it would have to thrust for many years to match velocities.

As for numbers, the calculations required for IS travel have been made and remade for decades and always come out with the same results; yes, a starship would be easily detectable and identifiable from far, far away. Even when not thrusting, the energy expended to keep up the day-to-day maintenance of such a vessel would glow hot against the cold cosmic background and move in ways no star does. And a decelerating ship would always be thrusting.

http://www.projectrho.com/public_html/rocket/slowerlight.php#id--Relativity

http://www.projectrho.com/public_html/rocket/spacewardetect.php#id--There_Ain't_No_Stealth_In_Space

http://en.wikipedia.org/wiki/Interstellar_travel#Required_energy

https://www.google.com/#q=interstellar+travel+calculator

Which leads to the question, how would they know in advance what our detection technology is like? How would they develop communications with us? How, again, would they pass for human? How would they know enough about our societies and psychology to reliably manipulate us?

casey10s
2013-Oct-14, 03:39 AM
I made a comment a few years ago concerning an alien civilization visiting earth. One can say that recorded human history is under 10,000 years depending on how one looks at it. What are the random chances that any alien civilization would have visited earth in this time frame? If an intelligent civilization could have existed for the last few billion years, 10,000 years is a very small window to hit. An alien civilization could have visited a million years ago, looked around, maybe take some samples, noted this planet in their archives, and we would have never known this happened. The recorded human time frame is nothing special. Why would anyone expect from a statistical view that a visit would have happened in our recorded history? If it did, it would have been a very rare occurrence.

I fit into the group that we, as humans, may not appear very intelligent to any alien civilization. We may look like chimps and dolphins do to us. Maybe they would try to interact with us but then again, they may say "interesting" and move on. Maybe they would come back and check on us at some time in the future. We may have been visited, cataloged, and put on a revisit at a later time list.

Colin Robinson
2013-Oct-14, 09:21 AM
I made a comment a few years ago concerning an alien civilization visiting earth. One can say that recorded human history is under 10,000 years depending on how one looks at it. What are the random chances that any alien civilization would have visited earth in this time frame? If an intelligent civilization could have existed for the last few billion years, 10,000 years is a very small window to hit. An alien civilization could have visited a million years ago, looked around, maybe take some samples, noted this planet in their archives, and we would have never known this happened. The recorded human time frame is nothing special. Why would anyone expect from a statistical view that a visit would have happened in our recorded history? If it did, it would have been a very rare occurrence.

I fit into the group that we, as humans, may not appear very intelligent to any alien civilization. We may look like chimps and dolphins do to us.

Maybe, if we're very lucky. Chimps (as a species) are our closest relatives, after all.

Another possibility is that an alien civilization might see the whole human species as a bigger than average frog in a very small pond.

absael
2013-Oct-14, 06:44 PM
10 billion miles is nothing to the blazing glow of a starship engine. And it would have to thrust for many years to match velocities.

As for numbers, the calculations required for IS travel have been made and remade for decades and always come out with the same results; yes, a starship would be easily detectable and identifiable from far, far away. Even when not thrusting, the energy expended to keep up the day-to-day maintenance of such a vessel would glow hot against the cold cosmic background and move in ways no star does. And a decelerating ship would always be thrusting.

http://www.projectrho.com/public_html/rocket/slowerlight.php#id--Relativity

http://www.projectrho.com/public_html/rocket/spacewardetect.php#id--There_Ain't_No_Stealth_In_Space

http://en.wikipedia.org/wiki/Interstellar_travel#Required_energy

https://www.google.com/#q=interstellar+travel+calculator

Which leads to the question, how would they know in advance what our detection technology is like? How would they develop communications with us? How, again, would they pass for human? How would they know enough about our societies and psychology to reliably manipulate us?

Interesting links, thanks. The articles certainly seem to demonstrate that sneaking up on another planet may very well be impossible, especially if someone with our current technology, or better, is looking for you. And I'm not sufficiently attached to my scenario to stubbornly defend it in the face of overwhelming evidence that it's impossible; for one thing, I think it's highly unlikely that aliens would visit earth for any reason. I just presented this as a possible (using a liberal definition) scenario that I felt the OP neglected to consider. But I'll address your points and your questions here, since I brought it up.

Regarding the articles, and in particular the one on stealth in space, there were a couple of assumptions that may not necessarily apply here. One is that we are scanning the skies with equipment that would detect their heat output; I'm not sure that this is the case, but I could be wrong. Another assumption in the article is that the approaching ship would need to engage other ships in battle, so it would have to be able to maneuver. In my scenario, the ship could set its course from quite a distance from Earth and coast the rest of the way.

To address your other questions, they wouldn't have any way to assess our detection capabilities until they got close, and even then I think they could make only a very rough guess. So, if they really wanted to avoid detection, they're taking a huge risk.

I don't think that they would have to pass as human; all they would need to do is get a message to someone who's qualified to evaluate its worth. They would have to land, hide somewhere, and observe us for a while to do much more than that. Yes, we're getting well into woo territory here, but after all, the topic of the thread is pretty far out there to start with IMO. ;)

absael
2013-Oct-14, 06:56 PM
Medical technology seems possible, perhaps they would teach us new scanning techniques like MRI or PET. But in terms of drugs, whatever they have would be irrelevant to us. We would probably appreciate blood thinning drugs, but they probably wouldn't even have blood the way we do. Our blood is loosely derived from seawater.

I thought about this, but it occurred to me that it's possible that there may be enough similarities in our physiology that they might have, or be able to develop, drugs that would work for us. For example, maybe they have viruses, just not the same ones that we do, and they've found a drug that is effective on all viruses.

Noclevername
2013-Oct-14, 09:15 PM
I thought about this, but it occurred to me that it's possible that there may be enough similarities in our physiology that they might have, or be able to develop, drugs that would work for us. For example, maybe they have viruses, just not the same ones that we do, and they've found a drug that is effective on all viruses.

There are some problems with that idea. Viruses use Earthly RNA and/or DNA and are adapted specifically to Earth life, and would likely have little in common with alien biochemistry. Aliens might have some biological agent similar to viruses, but they would not be viruses, any more than an alien shaped roughly humanoid would actually be human.

Viruses are also so widely varied biologically that the only thing some of them have in common is being viruses, and needing the cells they've adapted to in order to reproduce. A drug that could kill all viruses could probably also kill everything else, at least all life that uses RNA and DNA.

Jens
2013-Oct-14, 11:27 PM
Just adding to Noclevername's explanation, a virus is essentially a parasitic entity. In order to replicate it has to hijack a cell's machinery, so it has to trick the cell into allowing it to insert it's own genes. So by blocking those tricks you can stop the virus. But an alien virus, if such a thing existed, would not use the same tricks because the cellular machinery would be different. Even on earth, where life is related, there are viruses that can infect plants (which have cell walls) but not animal cells, which don't.

absael
2013-Oct-14, 11:48 PM
There are some problems with that idea. Viruses use Earthly RNA and/or DNA and are adapted specifically to Earth life, and would likely have little in common with alien biochemistry. Aliens might have some biological agent similar to viruses, but they would not be viruses, any more than an alien shaped roughly humanoid would actually be human.

Viruses are also so widely varied biologically that the only thing some of them have in common is being viruses, and needing the cells they've adapted to in order to reproduce. A drug that could kill all viruses could probably also kill everything else, at least all life that uses RNA and DNA.

Alien biochemistry could be somewhat similar, or even very similar, to our own. Perhaps the arrangement of guanine, cytosine, adenine, and thymine into a double helix structure is common in all advanced life forms. Or perhaps some other advanced alien life forms use something more chemically related to our RNA, but some combination of the chemicals (GATC, uracil, ribose, deoxyribose) is either required or extremely common. Even if their physiology is substantially different from ours, they might have detailed information on another alien life form that is much more similar. Article on wired.com: Humans and Aliens Might Share DNA Roots (http://www.wired.com/wiredscience/2009/04/thermodynamino/) [EDIT: link fixed]

Or, perhaps they visited Earth thousands of years ago and probed a human, and have been developing drugs in the meantime. Or perhaps their technology is so advanced that they are able to examine us and develop something on the spot.

In any case, I brought it up only in an attempt to consider a wide range of possibilities. As I mentioned, I think it's unlikely that aliens would visit Earth, and I think it's even less likely that they would do so solely for the purpose of advancing our medical knowledge out of the goodness of their alien hearts.

absael
2013-Oct-14, 11:57 PM
Just adding to Noclevername's explanation, a virus is essentially a parasitic entity. In order to replicate it has to hijack a cell's machinery, so it has to trick the cell into allowing it to insert it's own genes. So by blocking those tricks you can stop the virus. But an alien virus, if such a thing existed, would not use the same tricks because the cellular machinery would be different. Even on earth, where life is related, there are viruses that can infect plants (which have cell walls) but not animal cells, which don't.

And there are also viruses that infect both humans and animals that we diverged from tens of millions of years ago. I'm not sure that we can assume that alien life forms will be fundamentally different from us (as different as us and plants, for example). Perhaps some of them are, but it doesn't seem unreasonable to postulate that some aren't, since we at least know that our physiology is a possibility in an intelligent being. We have no evidence that a drastically different one is.

Colin Robinson
2013-Oct-15, 10:06 AM
And there are also viruses that infect both humans and animals that we diverged from tens of millions of years ago. I'm not sure that we can assume that alien life forms will be fundamentally different from us (as different as us and plants, for example).

Are plants fundamentally different from us?

Plants, and metazoans (such as humans), belong to the domain Eukaryota — one of the three main divisions of life on Earth.

I'd suggest an extraterrestrial might look carefully at a human and a radish, and find it very hard to say which was which: "Sorry, but all Eukaryota look the same to me."

Noclevername
2013-Oct-15, 10:09 AM
Plants and humans share about half our DNA in common on average. An examination will quickly show that we share the same microbial ancestors.

Noclevername
2013-Oct-15, 12:28 PM
In fact we share more in common genetically with beer (barley, hops, yeast) than we could ever hope to with any living product of a completely different biochemical origin, and evolutionary and ancestral lineage.

absael
2013-Oct-15, 05:35 PM
In fact we share more in common genetically with beer (barley, hops, yeast) than we could ever hope to with any living product of a completely different biochemical origin, and evolutionary and ancestral lineage.

How do you know that? What data are you using to support your assumptions?

From the article that I linked to in the previous post: "The building blocks of life may be more than merely common in the cosmos. Humans and aliens could share a common genetic foundation." "If the observed patterns of amino acid formation — simple acids require low levels of energy to coalesce, and complex acids need more energy — indeed follow thermodynamic laws, then the basic narrative of life’s emergence could be universal." ""There’s a possible universality . . for any code that would use amino acids."

Given the vastness of the cosmos, I don't think it's unreasonable to surmise that there are alien beings with a genetic makeup that bears some similarity to ours.

Noclevername
2013-Oct-15, 06:00 PM
How do you know that? What data are you using to support your assumptions?

From the article that I linked to in the previous post: "The building blocks of life may be more than merely common in the cosmos. Humans and aliens could share a common genetic foundation." "If the observed patterns of amino acid formation — simple acids require low levels of energy to coalesce, and complex acids need more energy — indeed follow thermodynamic laws, then the basic narrative of life’s emergence could be universal." ""There’s a possible universality . . for any code that would use amino acids."

Given the vastness of the cosmos, I don't think it's unreasonable to surmise that there are alien beings with a genetic makeup that bears some similarity to ours.

We're talking about two fundamentally different things here by "genetic makeup". How much of our genetic code is common to other Earth life from our first common ancestor (http://en.wikipedia.org/wiki/Last_universal_ancestor) and how much has diverged is increasingly known and measured. An alien species, even one that uses DNA for their genes, will still have an entirely different informational coding; just because two species both communicate with sound does not mean they speak the same language. See http://en.wikipedia.org/wiki/Evidence_of_common_descent

absael
2013-Oct-15, 06:54 PM
We're talking about two fundamentally different things here by "genetic makeup". How much of our genetic code is common to other Earth life from our first common ancestor (http://en.wikipedia.org/wiki/Last_universal_ancestor) and how much has diverged is increasingly known and measured. An alien species, even one that uses DNA for their genes, will still have an entirely different informational coding; just because two species both communicate with sound does not mean they speak the same language. See http://en.wikipedia.org/wiki/Evidence_of_common_descent

I think our disagreement is based more on opinion than evidence. We don't know how many other ways our LUA could have evolved, and we don't how many variations from a single-celled organism could have survived to eventually evolve into much more complex life.

I realize that, even assuming similar planetary environments, there are a very large number of accidents that affect the path of evolution. But we don't have a good grasp of how many substantially different primitive life forms could possibly develop into an intelligent species (or the relative likelihood).

There are a lot of planets out there (60 Billion Habitable Planets in the Milky Way Alone? (http://www.universetoday.com/103379/60-billion-habitable-planets-in-the-milky-way-alone-astronomers-say-yes/)). I don't think we disagree that there are probably a lot of them with life forms that are fundamentally different from those on Earth. But I don't see how anyone can state with certainty that evolution didn't follow a somewhat similar path twice, or a hundred times, or a million times.

Noclevername
2013-Oct-15, 08:59 PM
But I don't see how anyone can state with certainty that evolution didn't follow a somewhat similar path twice, or a hundred times, or a million times.

Sharks and dolphins both are morphologically similar, large vertebrate sea predators. But I don't think they could be mistaken for each other in daylight.

Noclevername
2013-Oct-15, 09:12 PM
Or perhaps a better example is snowflakes; made of the same composition under the same conditions with the same symmetry, yet they are unique molecular patterns.

absael
2013-Oct-15, 10:07 PM
OK, but I don't see the relevance of either analogy to the possibility that there are planets where evolution followed a path that is somewhat similar to that which occurred here. Until you can provide good evidence that it can't happen (which is what you're claiming), the reasonable assumption IMO is that it can. And I see no reason to believe that it will ever be possible for anyone to provide that evidence. Until then, we're talking about probabilities, which we're guessing at using entirely insufficient data.

eburacum45
2013-Oct-16, 12:12 AM
There could be as many as 1084 different genetic codes, each discernable from the other. Some large proportion of those codes might be sub-optimal, or be unlikely to exist, but even if only one trillionth of those codes are likely to emerge elsewhere, that still means there could be 1072 different possible codes. That is enough to allow every planet around every star in our galaxy to have more than 1050 unique codes.


Earth has at least nineteen,
http://en.wikipedia.org/wiki/List_of_genetic_codes
each distiguishable from the other but all descended from a common ancestor; this demonstrates that more than one unique code is possible.

absael
2013-Oct-16, 01:01 AM
While it may sound reasonable at first blush to allow for only one-trillionth of the possible number of codes, there seems (in my very brief Internet search) to be a lot of controversy regarding viable codes. This article on Wikipedia (http://en.wikipedia.org/wiki/Genetic_code#Transfer_of_information_via_the_genet ic_code) states "There are enough data to refute the possibility that the genetic code was randomly constructed ('a frozen accident').", "Natural selection has led to codon assignments of the genetic code that minimize the effects of mutations.", and ". . . all known naturally-occurring codes are very similar to each other, and the coding mechanism is the same for all organisms. . ." Also see the quotes in my post above from the wired.com article, to which I'll add this one:


The building blocks of life may be more than merely common in the cosmos. Humans and aliens could share a common genetic foundation.




Thatís the tantalizing implication of a pattern found in the formation of amino acids in meteorites, deep-sea hydrothermal vents, and simulations of primordial Earth. The pattern appears to follow basic thermodynamic laws, applicable throughout the known universe.




"This may implicate a universal structure of the first genetic codes anywhere," said astrophysicist Ralph Pudritz of McMaster University in Hamilton, Ontario.



I was not able to find any research which sheds light on number of codes that are likely to actually survive long enough to evolve into intelligent beings. If you have links to any such articles, I'd certainly be interested in reading them.

Noclevername
2013-Oct-16, 01:35 AM
I was not able to find any research which sheds light on number of codes that are likely to actually survive long enough to evolve into intelligent beings.

How do you know that intelligent beings will evolve? Evolution is a sorting process for replicating informational sets adapted to specific environments. It does not have a set path. It seems like more than time is required to reach sapient intelligence as we know it.

The human genome contains a number of population bottlenecks (http://en.wikipedia.org/wiki/Population_bottleneck) where our own ancestors were reduced to a mere handful on the edge of extinction. So homo sapiens almost didn't evolve even here on Earth.

Noclevername
2013-Oct-16, 01:44 AM
OK, but I don't see the relevance of either analogy to the possibility that there are planets where evolution followed a path that is somewhat similar to that which occurred here.

"A" path here? Which one?

Noclevername
2013-Oct-16, 01:54 AM
Until you can provide good evidence that it can't happen (which is what you're claiming), the reasonable assumption IMO is that it can.

A reasonable assumption is by definition based on reasoning. Can you explain yours?

absael
2013-Oct-16, 01:56 AM
How do you know that intelligent beings will evolve? Evolution is a sorting process for replicating informational sets adapted to specific environments. It does not have a set path. It seems like more than time is required to reach sapient intelligence as we know it.

The human genome contains a number of population bottlenecks (http://en.wikipedia.org/wiki/Population_bottleneck) where our own ancestors were reduced to a mere handful on the edge of extinction. So homo sapiens almost didn't evolve even here on Earth.

I don't, but that is the topic of the thread, so like everyone else here I'm entertaining the notion for the sake of argument. ;)

absael
2013-Oct-16, 02:00 AM
"A" path here? Which one?
The one which resulted in you and me. We seem to have strayed so far from the original topic that we've lost sight of the reason for our discussion.

Noclevername
2013-Oct-16, 02:02 AM
I don't, but that is the topic of the thread, so like everyone else here I'm entertaining the notion for the sake of argument. ;)

OK, then.

Let's say intelligence requires tool use, large complex brains, and visual spacial and color perception.

Octopus.

It has exhibited complex object manipulation, communication, problem solving and learned behavior. There's no reason to assume it can't develop its own sapience and go on to build a civilization. Prove it's impossible! :D

eburacum45
2013-Oct-16, 02:04 AM
I was not able to find any research which sheds light on number of codes that are likely to actually survive long enough to evolve into intelligent beings. If you have links to any such articles, I'd certainly be interested in reading them.

Freedman, Wu and Kuelman has a rough estimate, in that only one in a million codes is as error-free as the 'standard' genetic code
http://euplotes.biology.uiowa.edu/web/transitionspapers/week6/FWK.pdf
this is a million times more favourable than my 'one-in-a-trillion' speculative figure, which could itself be optimistic by many orders of magnitude and yet still allow for a vast range of potential genetic codes.

If only one in a million codes are suitable, that could explain why only nineteen such codes have emerged on Earth; but the fact that nineteen different codes have emerged, does suggest that alternative codes are not only possible, but are viable.

absael
2013-Oct-16, 02:06 AM
A reasonable assumption is by definition based on reasoning. Can you explain yours?
Yes. We know for certain that it can happen, therefore it's reasonable to assume that it could happen again, absent evidence to the contrary. Also, since you're making the claim that it's impossible that it could happen again, I'm not sure that I'm the one who bears the burden of proof here.

Noclevername
2013-Oct-16, 02:08 AM
Yes. We know for certain that it can happen, therefore it's reasonable to assume that it could happen again, absent evidence to the contrary. Also, since you're making the claim that it's impossible that it could happen again, I'm not sure that I'm the one who bears the burden of proof here.

Can you find the exact quote where I said it was impossible?

It's possible to roll seven a million times in a row. It's not going to happen (at least with any dice that are not loaded!)

Noclevername
2013-Oct-16, 02:12 AM
I'm not sure that I'm the one who bears the burden of proof here.

Under Forum policy, you'd be the one since you're making the extraordinary claim.

absael
2013-Oct-16, 02:22 AM
OK, then.

Let's say intelligence requires tool use, large complex brains, and visual spacial and color perception.

Octopus.

It has exhibited complex object manipulation, communication, problem solving and learned behavior. There's no reason to assume it can't develop its own sapience and go on to build a civilization. Prove it's impossible! :D

I can't prove it's impossible, so I'll give you the octopus. How many more examples can you come up with? Divide that into the number of planets on which life could arise and evolve :D

absael
2013-Oct-16, 02:25 AM
Under Forum policy, you'd be the one since you're making the extraordinary claim.

I disagree that my claim is the extraordinary one; I'm merely saying that it could happen - and no one has yet cited mainstream scientific articles stating otherwise. Also, I wasn't aware that that policy applied outside of the ATM and Conspiracy Theory forums.

Jens
2013-Oct-16, 02:25 AM
The building blocks of life may be more than merely common in the cosmos. Humans and aliens could share a common genetic foundation.

It's certainly an interesting idea that DNA may be shared by ETs because it has unique properties as a molecule that make it particularly suited for its task. Even if it is true, it leaves you very far from any kind of biological compatibility. Having genetic information coded in the same type of molecule is not remotely sufficient to allow a virus to infect a cell. It has to be able to attach itself to a receptor, which even if they exist would not have the same shapes, and then must hijack the cell's machinery, which is not set in stone in any way and would surely be very different in an alien lifeform. So the virus would not be able to hijack the machinery and replicate itself. Viruses are able to infect cells because they have evolved together for specifically that purpose.

Noclevername
2013-Oct-16, 02:27 AM
I can't prove it's impossible, so I'll give you the octopus. How many more examples can you come up with? Divide that into the number of planets on which life could arise and evolve :D

I can only divide it into one, sine Earth is the only planet with proven life. Do you need me to cite an article that shows there's life here?

absael
2013-Oct-16, 02:37 AM
Can you find the exact quote where I said it was impossible?

It's possible to roll seven a million times in a row. It's not going to happen (at least with any dice that are not loaded!)

You said,

In fact we share more in common genetically with beer (barley, hops, yeast) than we could ever hope to with any living product of a completely different biochemical origin, and evolutionary and ancestral lineage.
I took "more than we could ever hope to" to mean that the other option isn't a possibility. And you said


An alien species, even one that uses DNA for their genes, will still have an entirely different informational coding
Since you spoke here in certainties instead of probabilities, it seemed to me that you were saying it can't happen.

And, since all I'm saying is that it can, and you're continuing to say I'm wrong, I assumed that you are saying it can't (IOW, it's impossible). Not so?

Noclevername
2013-Oct-16, 02:41 AM
You said,

I took "more than we could ever hope to" to mean that the other option isn't a possibility. And you said

[/COLOR]
[/COLOR]Since you spoke here in certainties instead of probabilities, it seemed to me that you were saying it can't happen.

And, since all I'm saying is that it can, and you're continuing to say I'm wrong, I assumed that you are saying it can't (IOW, it's impossible). Not so?







Not so. If I meant impossible I would say impossible.

I made a statement about what we can expect, not an absolute. As I said, just because something is technically possible doesn't meant it's ever going to happen. Every particle in my body might spontaneously quantum-tunnel through a wall at the same time. I'm not losing sleep over it.

absael
2013-Oct-16, 02:48 AM
I can only divide it into one, sine Earth is the only planet with proven life. Do you need me to cite an article that shows there's life here?

Sarcasm noted; I'm beginning to lose interest in this discussion, since you seem to be more interested in proving me wrong (without evidence) than in staying with the spirit of the discussion, which - again - is premised on the assumption that there are intelligent beings who might build a spacecraft and visit Earth.

I'm starting to feel badly for pulling the OP's thread so far off track. I originally meant only to provide another scenario for discussion, but felt an obligation to defend my post when you questioned it. This isn't the ATM forum, but perhaps I should have known better than to float an unpopular idea. I didn't suspect that merely saying that it's a possibility would result in a whole page of posts arguing about it.

Noclevername
2013-Oct-16, 02:57 AM
Sarcasm noted; I'm beginning to lose interest in this discussion, since you seem to be more interested in proving me wrong (without evidence) than in staying with the spirit of the discussion, which - again - is premised on the assumption that there are intelligent beings who might build a spacecraft and visit Earth.

I'm starting to feel badly for pulling the OP's thread so far off track. I originally meant only to provide another scenario for discussion, but felt an obligation to defend my post when you questioned it. This isn't the ATM forum, but perhaps I should have known better than to float an unpopular idea. I didn't suspect that merely saying that it's a possibility would result in a whole page of posts arguing about it.

It would have been helpful if you had indicated at the start that you were not seriously proposing a scenario you thought would happen.

The reason I tried so hard to "prove you wrong" was because I thought I was correcting someone who had a fundamental misunderstanding of evolution, not someone who knew better and was playing devil's advocate. "Prove it's impossible" is usually a red flag for that kind of belief. I was attempting to avoid misinformation.

absael
2013-Oct-16, 03:06 AM
It would have been helpful if you had indicated at the start that you were not seriously proposing a scenario you thought would happen.

The reason I tried so hard to "prove you wrong" was because I thought I was correcting someone who had a fundamental misunderstanding of evolution, not someone who knew better and was playing devil's advocate. "Prove it's impossible" is usually a red flag for that kind of belief. I was attempting to avoid misinformation.

OK :)

It looks like this was an unfortunate misunderstanding, and reading your explanation and thinking back to previous threads here, I can see how it could happen. Despite my join date, I haven't posted a lot, so I'm essentially new here. In any case, I learned some things in researching the points I was trying to make, and I hope some others here did too.

Oh, and you were successful in changing my mind about the "stealth spaceship" thing, so I do appreciate your input.

Noclevername
2013-Oct-16, 03:19 AM
OK :)

It looks like this was an unfortunate misunderstanding, and reading your explanation and thinking back to previous threads here, I can see how it could happen. Despite my join date, I haven't posted a lot, so I'm essentially new here. In any case, I learned some things in researching the points I was trying to make, and I hope some others here did too.

Oh, and you were successful in changing my mind about the "stealth spaceship" thing, so I do appreciate your input.

I'm glad we worked out the conflict without resorting to violence. ;)