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John Jaksich
2012-Aug-07, 03:09 PM
I wasn't too sure if the post belonged anywhere else, so I will put it here. If and/or when we do make some type of contact with intelligent ET, how likely will it be that our encounter will prove to be so foreign to us that we will not possess the ability to utilize any type of technology that they could offer us? Or, in short, will our encounter will prove to be meaningless to the average human---who may want his/her day-to-day needs met---and not want to care that the event would prove to be momentous beyond anything history may have recorded?

I am still trying to form the right words but I am a little fuzzy ---sorry.

primummobile
2012-Aug-07, 03:37 PM
I think it will be like what you read in Carl Sagan's Contact.

John Jaksich
2012-Aug-07, 03:48 PM
If I remember what I read---I don't happen to believe that art will imitate life. The reason why asked the question---I was watching one the episodes Cosmos---and maybe my question has been answered over and over. But I really don't know what some people will say? And, yes question is very fuzzy? It is a generalization.

Noclevername
2012-Aug-07, 03:54 PM
Depends on the type of contact. If it's a distant radio signal, I think the majority of people will say "Oh, cool" and then go back ot their day. If it's a ship entering our solar system, there will be trepidation, possibly some overrreaction and definitely military buildup. If they just appear hovering over our major cities, there will be panic and riots in the streets.

primummobile
2012-Aug-07, 04:08 PM
I do think that life will imitate art. A lot of people are going to start questioning many things if we make contact with an alien race, and unfortunately many people are going to give in to fear or superstition. Others will try to push themselves to the forefront. Yet others will pretend to be experts.

I don't think that there would be any significant sharing of technology until we learned to communicate with one another. That may be a problem, but I doubt the aliens would make themselves known to us without studying us very thoroughly first.

Noclevername
2012-Aug-07, 05:02 PM
I don't think that there would be any significant sharing of technology until we learned to communicate with one another. That may be a problem, but I doubt the aliens would make themselves known to us without studying us very thoroughly first.

That's assuming the contact is intentional. If we just detect signals leakage, or if they just send a probe or stop to examine this system because Saturn has pretty rings, then they won't know how to make heads or tails of us.

John Jaksich
2012-Aug-07, 05:12 PM
I am sure there are many who would panic and not know what to do if intelligent ET were to show up on the Earth? Appeals to authority and a higher power would be as likely riots in the streets--IMO. May be my question has turned into an exercise of philosophy--more than anything else?

John Jaksich
2012-Aug-07, 05:20 PM
I do think that life will imitate art. A lot of people are going to start questioning many things if we make contact with an alien race, and unfortunately many people are going to give in to fear or superstition. Others will try to push themselves to the forefront. Yet others will pretend to be experts.

I don't think that there would be any significant sharing of technology until we learned to communicate with one another. That may be a problem, but I doubt the aliens would make themselves known to us without studying us very thoroughly first.


If there is anything that I am certain of ---it is that we most probably would find it incredulous to understand anything beyond our own comprehension. It is as if we were all "flat-landers and someone from an alternate dimension introduced themselves to us" ---how would we know how to respond?

Ara Pacis
2012-Aug-07, 07:15 PM
This thread probably belongs in the Life in Space subforum.


I wasn't too sure if the post belonged anywhere else, so I will put it here. If and/or when we do make some type of contact with intelligent ET, how likely will it be that our encounter will prove to be so foreign to us that we will not possess the ability to utilize any type of technology that they could offer us? If they come from a planet with dramatically different chemical, magnetic and physical properties (different from STP) then we might not be able to use their tech on earth, though we might be able to recreate it in special labs if they send us details. If they arrive physically, then we know their tech will work in a space environment, at least, but I doubt it would be so far removed from what we know about physics that we won't be able to grasp it.


I don't think that there would be any significant sharing of technology until we learned to communicate with one another. That may be a problem, but I doubt the aliens would make themselves known to us without studying us very thoroughly first.

I doubt this, unless you're positing some vastly new physics. If they are using radio, we'll probably only hear them if they're trying to be heard, and they won't hear us unless we're trying to be heard, so there's very little they would actually know about is without contact. If they show up physically, most physical laws we currently understand would mean they would have had to be on their way for a long time now and wouldn't have known anything about us until they got really close, at which point it may be to late to prevent contact. A world ship on a ballistic trajectory through the galaxy with limited ability to stop would be hard set to establish a long term observation of us prior to commitment to contact or close approach. However, they might decide to not initiate contact and hope to slip by unnoticed.

Noclevername
2012-Aug-07, 07:19 PM
The long timeframe needed for signal return means a long-lived species could have sent probes millenia ago, and arrive expecting to find us in bearskins weilding spears.

eburacum45
2012-Aug-07, 08:18 PM
A civilisation that has been using advanced technology for thousands of years might be so used to it that they would find some difficulty explaining it to us. Especially if it is integrated partially, or totally, into their physical bodies (which might be very different to our own). Even though any technology they may possess will no doubt run on principles that we already know about or that we could, in time, appreciate, that doesn't mean we could easily grasp the way in which it works.

Advanced technology may be at least as complex (and as difficult to fully comprehend) as a biological organism; it may in fact be many times more complex than that. Complexity is likely to be a worse barrier to understanding alien technology than physical science.

swampyankee
2012-Aug-07, 08:59 PM
Radio (or something similar)? Nobody outside of a few specialists care. Similarly, if they snag a few KBOs. Indeed, not much popular effect until their spaceships hover above Earth in exactly the way bricks don't.

primummobile
2012-Aug-07, 11:23 PM
This thread probably belongs in the Life in Space subforum.

If they come from a planet with dramatically different chemical, magnetic and physical properties (different from STP) then we might not be able to use their tech on earth, though we might be able to recreate it in special labs if they send us details. If they arrive physically, then we know their tech will work in a space environment, at least, but I doubt it would be so far removed from what we know about physics that we won't be able to grasp it.



I doubt this, unless you're positing some vastly new physics. If they are using radio, we'll probably only hear them if they're trying to be heard, and they won't hear us unless we're trying to be heard, so there's very little they would actually know about is without contact. If they show up physically, most physical laws we currently understand would mean they would have had to be on their way for a long time now and wouldn't have known anything about us until they got really close, at which point it may be to late to prevent contact. A world ship on a ballistic trajectory through the galaxy with limited ability to stop would be hard set to establish a long term observation of us prior to commitment to contact or close approach. However, they might decide to not initiate contact and hope to slip by unnoticed.

I'm making the assumption that there would be an alien race who wants to and is able to direct communication to us. In that case, it's rather naive to think that they would not try to study us first, especially if they were arriving in person. I am making absolutely no statements on how they would get here because that's been talked to death on this forum, and it is completely off topic here.

I'm not positing any new physics. I'm saying what may happen if we were faced with advanced technology. If you took a microprocessor back to the nineteenth century they would have no idea what it was, though understanding it would not require any new physics. That's why you would need communication before any meaningful technology exchange.

Noclevername
2012-Aug-07, 11:55 PM
In that case, it's rather naive to think that they would not try to study us first, especially if they were arriving in person.

The question is, how would they study us? If they are relying on visual images or radio signals (whether direct or from a probe), there's the light-lag to take into consideration, barring FTL communication. For them to know anything about how we are now, they would have to be hiding somewhere in our solar system observing us up close-- which would require new laws of thermodynamics for their vessel's heat signature to be undetectable.

primummobile
2012-Aug-08, 12:12 AM
The question is, how would they study us? If they are relying on visual images or radio signals (whether direct or from a probe), there's the light-lag to take into consideration, barring FTL communication. For them to know anything about how we are now, they would have to be hiding somewhere in our solar system observing us up close-- which would require new laws of thermodynamics for their vessel's heat signature to be undetectable.

I wouldn't think it that difficult for them to hide from us. We're pretty good at hiding from ourselves. And they wouldn't need to park that far from us to be able to watch our 5:00 news every day but still be outside our detection range.

Noclevername
2012-Aug-08, 12:19 AM
I wouldn't think it that difficult for them to hide from us. We're pretty good at hiding from ourselves. And they wouldn't need to park that far from us to be able to watch our 5:00 news every day but still be outside our detection range.

I'm not so sure. If we can detect heat from distant galaxies, a starship, say, at the heliopause would stand out like a florescent thumb.

primummobile
2012-Aug-08, 12:42 AM
I'm not so sure. If we can detect heat from distant galaxies, a starship, say, at the heliopause would stand out like a florescent thumb.

But not if they had technology to conceal it from us. Look at the level of our stealth technology, and what we know about is over twenty years old. If they know how to fly here they can stay invisible to us until they decide to reveal themselves.

Frankly, I'm a little surprised at this line of questioning. Maybe I just don't see where you're coming from. You seem to be saying that they are limitex to technology little better than our own, but that they wouldn't try to learn about us before they landed on our yard. On Earth, we do very little without trying to find out something about what we are walking into. To do otherwise is foolish.

Noclevername
2012-Aug-08, 12:53 AM
But not if they had technology to conceal it from us.
Not without changing the laws of physics. Heat output is heat output at any tech level.



Frankly, I'm a little surprised at this line of questioning. Maybe I just don't see where you're coming from. You seem to be saying that they are limitex to technology little better than our own, but that they wouldn't try to learn about us before they landed on our yard. On Earth, we do very little without trying to find out something about what we are walking into. To do otherwise is foolish.

I'm saying they'd have no physical means of doing so without being detected, except for distances so extreme they would learn only what we used to be like. I'm saying that, not technology, but the laws of physics limit the amount of "knowing" that they can do without coming here directly and meeting us.

http://www.projectrho.com/public_html/rocket/thermodynamics.php
http://www.projectrho.com/public_html/rocket/spacewardetect.php#nostealth
http://www.projectrho.com/public_html/rocket/respectscience.php
Links to a site that may explain it better than I can.

From Project Rho:

So you know, university Physics is essentially three years of this discussion among like-minded enthusiasts.

Done with supercomputers, access to the textbook collections of five continents and thirty languages.

On four hours sleep a night.

With no sex.

You're not going to find the loophole these guys missed.

primummobile
2012-Aug-08, 01:06 AM
But that's not the point. I'm saying they could confuse our instruments. They may have probes inside asteroids. We have no way to know what they could do and even if they are only a hundred years ahead of us they could have things we can only dream about. Did you think you woukd have a computer in a phone twenty years ago? There is no way we have thought of everything because there are just too many questions about things we don't know. I'm sorry, I don't accept that a sufficiently advanced race couldn't hide from us. Space, even local space, is very big. They could be sitting in your own backyard and you may not know just because you aren't looking.

Noclevername
2012-Aug-08, 01:20 AM
The point is that, if we're wrong about basic thermodynamics, we're wrong about everything and none of our technology should work. None of our observations should match our current theories of physics. We can't be that wrong and still have a functioning industrial society or any consistent science.

More pertinent quotes from Project Rho:

Heat, by definition, is energy that comes with associated entropy. It is a well verified physical law that entropy cannot be destroyed, it can be created but the only way to decrease your amount of entropy is to move it somewhere else. To avoid having entropy build up on your spacecraft until something breaks, you need to get rid of it by moving it off the craft.

On a spacecraft, the only way you can move energy and entropy off the spacecraft is by putting it in something else and ejecting that something else, or radiating it away as electromagnetic waves. Since trying to put all your entropy in matter and dumping it is wasteful for your mass budget, radiation is the usual trick. However, the required radiator area scales as 1/temperature to the fourth power. The colder you are storing your entropy, the larger the radiator you need to get rid of it, and the size increases very rapidly with decreasing temperature.

"Maybe A Future Scientific Breakthrough Will Let Me Have My Way"
First off, from the standpoint of probability, there is at least a 50% chance that any new scientific breakthrough will actually make it harder to do what you want.

The general rule is what physicists call the correspondence principle or the Classical limit. This states that any new theory must give the same answers as the old theory where the old theory has been confirmed by experiment. Which means if you just state that in the year 2525 Professor XYZ came up with the "Take THAT, Einstein!" theory of FTL travel, you still have a problem. You have to explain how the TTE theory allows FTL flight while still giving the same answers that relativity theory did for all those experiments it confirmed. Experiments that were accurate to quite a few decimal points.

"A scientific explanation is one that is vindicated by practice." Radio transmitters transmit, and radio receivers receive. Lasers lase. Nuclear reactors react. Semi-conductors occasionally conduct. Tunnel diodes, LED's, SQUIDS, and other electromagnetic devices based on quantum mechanics do their thing repeatedly and reliably. So we're obviously doing something right! And we don't dare throw away the theoretical base on which these gadgets do indeed work. We can and should modify the theoretical base as necessary, but we can't throw it away. Any new theories of the universe must be compatible with the old ones or at least permit logical and rational modifications in order to shoe-horn the old theories into the new ones.

There is no unexplained phenomenon that might result in violating thermodynamics - and if there WERE something that violated thermo, it would radically change the universe as we know it - for instance, stellar processes require thermodynamics, the entire model of cosmology is based off of known properties for thermodynamics. Your car runs on thermodynamic processes. And all of these things work out the same way, and derive from the same knowledge base.

PlutonianEmpire
2012-Aug-08, 01:26 AM
"Maybe A Future Scientific Breakthrough Will Let Me Have My Way"
First off, from the standpoint of probability, there is at least a 50% chance that any new scientific breakthrough will actually make it harder to do what you want.
More like 100%. :(

/end rant.

swampyankee
2012-Aug-08, 01:49 AM
I know a bit about stealth -- I worked on low-observables for a few years -- and, yes, there are ways to hide a warm object from IR observations. One way is simply to cool (or heat) the side facing the observers to match the background, and radiate any waste heat off the back side. This would require that the stealthed ET know the location of the observers, but, right now, it's quite safe to assume they're all on Earth.


What would be more difficult would be for the ET's ship to hide itself if it is in front of something that has a well-known spectrum, so ET will have to be carefully located in front of a particularly boring part of the sky.

Ara Pacis
2012-Aug-08, 05:40 AM
A civilisation that has been using advanced technology for thousands of years might be so used to it that they would find some difficulty explaining it to us. Especially if it is integrated partially, or totally, into their physical bodies (which might be very different to our own). Even though any technology they may possess will no doubt run on principles that we already know about or that we could, in time, appreciate, that doesn't mean we could easily grasp the way in which it works. Maybe, if they don't have kids or don't need to explain it to them.


Advanced technology may be at least as complex (and as difficult to fully comprehend) as a biological organism; it may in fact be many times more complex than that. Complexity is likely to be a worse barrier to understanding alien technology than physical science.

This may be the kicker.

Ara Pacis
2012-Aug-08, 05:55 AM
I'm making the assumption that there would be an alien race who wants to and is able to direct communication to us. In that case, it's rather naive to think that they would not try to study us first, especially if they were arriving in person. I am making absolutely no statements on how they would get here because that's been talked to death on this forum, and it is completely off topic here. I'm not talking about intent, but ability. It's likely that they won't be able to study us before deciding on a course of action that reveals themselves, or risks revealing or stranding themselves here. If they have a limited ability to stop and no ability to leave again, or a limited ability which requires advanced infrastructure and gathering of resources, then they may not even know the system is inhabited before they've begun their deceleration. Once they're here, they're stuck. They may try to hang out in the distance and try to hide from us while trying to gather resources for a re-launch, or a distant settlement that doesn't conflict with ours (or even preparations for invasion), while studying us. They may be here already and may have been here for a while if that is the case. However, I make a distinction between "Hello, we come from far away and wanted to meet you" and "Oh, um, you mean this seat is already taken?"


I'm not positing any new physics. I'm saying what may happen if we were faced with advanced technology. If you took a microprocessor back to the nineteenth century they would have no idea what it was, though understanding it would not require any new physics. That's why you would need communication before any meaningful technology exchange.

Depends on who you show it to. They had electricity then and gear-based computers so they might understand the concepts, if not the engineering and materials science due to a lack in precision equipment and a few theories and observations yet to occur. We feel the standard model is mostly complete and we have the precision to see things very well at small scales, so I suspect we would be able to figure out the alien tech eventually.

primummobile
2012-Aug-08, 12:55 PM
The point is that, if we're wrong about basic thermodynamics, we're wrong about everything and none of our technology should work. None of our observations should match our current theories of physics. We can't be that wrong and still have a functioning industrial society or any consistent science.

More pertinent quotes from Project Rho:

Noclevername, you're not getting me, which is probably my fault. All I'm saying is that if they can travel here they can probably hide themselves. There are more ways to do that besides just not putting out any heat. They could actively block our detection of them. They could 'fool' our instruments into thinking they were something more benign. The US military invests a lot of money into doing those sorts of things. They're doing research now, all over the world, into how to make objects "invisible" not only to radar, but also to visible light. Every method involves actively projecting what you want others to see rather than just hunkering down and hoping you aren't noticed.

The ways and methods an advanced species may choose to do this are mostly unfathomable to us. But I don't think a sufficiently advanced race would have trouble hiding a probe the size of a satellite from our detection, especially if they wanted us to think it was something we would expect to find in space. Keep in mind, I don't think it likely this is happening, or will happen. I'm just not ruling out the possibility.

There are still some groups of people in this world, in South America and New Guinea, who are considered to be "uncontacted" by modern society. Any number of sufficiently advanced groups could spy on these people, from the air or the ground, and learn much about them without those people ever knowing they were being watched. Those groups of people, at most, are a few thousand years removed from us technologically. What could an alien civilization that was tens of thousands of years from us accomplish? The best place to hide is in plain sight. So they make us think we're looking at something else. That hummingbird you see outside your window may not be a hummingbird. The fly on the wall may not be a fly. Halley's Comet may not be a comet. Of course, I'm being absurd. But I'm being absurd to make a point. I'm not suggesting that they can change the laws of thermodynamics. I'm just suggesting that they can fool us.

primummobile
2012-Aug-08, 01:25 PM
I'm not talking about intent, but ability. It's likely that they won't be able to study us before deciding on a course of action that reveals themselves, or risks revealing or stranding themselves here. If they have a limited ability to stop and no ability to leave again, or a limited ability which requires advanced infrastructure and gathering of resources, then they may not even know the system is inhabited before they've begun their deceleration. Once they're here, they're stuck. They may try to hang out in the distance and try to hide from us while trying to gather resources for a re-launch, or a distant settlement that doesn't conflict with ours (or even preparations for invasion), while studying us. They may be here already and may have been here for a while if that is the case. However, I make a distinction between "Hello, we come from far away and wanted to meet you" and "Oh, um, you mean this seat is already taken?"

I don't argue that. I, however; am talking about intent, and not ability. I don't know what kind of propulsion system they would have. Maybe they have found a way to manufacture antimatter and they have a large storage capacity. Ten grams of antimatter (yes, I know that is many orders of magnitude more than what we have ever produced on Earth) could take a manned spacecraft to Mars in one month. What if they have access to a thousand kg of antimatter? It may sound absurd, but if you had told a physicist 200 years ago that we could slam atomic particles together (after you explained what atomic particles are) at just under the speed of light they would have thought you were crazy. The point is that I'm not making any assumptions on what they can do. All I'm doing is asking what they would do if they could. And I believe that if they were able to study us before they made contact they would do that, and that it would be foolish to not do that if they had the capability.



Depends on who you show it to. They had electricity then and gear-based computers so they might understand the concepts, if not the engineering and materials science due to a lack in precision equipment and a few theories and observations yet to occur. We feel the standard model is mostly complete and we have the precision to see things very well at small scales, so I suspect we would be able to figure out the alien tech eventually.

Eventually, I don't argue that we would figure it out. But electricity isn't the only game in town. And even in our own electronics, the theory of how it all works isn't complete. We aren't able to manufacture a transistor with a specific gain. All we are able to do is manufacture it within a range of gain. There are still tremendous improvements we could make just in manufacturing of our existing technology that an experienced engineer would have a tough time understanding if it was just thrown in his lap from a hundred years in the future. So, could we figure it out? Yes, probably. But when you consider that it may be unrecognizable to us, it may take a very long time.

And it would be really irresponsible of the aliens to drop something in our laps that was designed to cure cancer, but could be turned into a bomb with greater ease, without explaining to us how it works and what it is used for. They would especially understand how foolish that would be if they watched our nightly news broadcasts for a few weeks first.

Ara Pacis
2012-Aug-08, 06:26 PM
I don't argue that. I, however; am talking about intent, and not ability. I don't know what kind of propulsion system they would have. Maybe they have found a way to manufacture antimatter and they have a large storage capacity. Ten grams of antimatter (yes, I know that is many orders of magnitude more than what we have ever produced on Earth) could take a manned spacecraft to Mars in one month. What if they have access to a thousand kg of antimatter? It may sound absurd, but if you had told a physicist 200 years ago that we could slam atomic particles together (after you explained what atomic particles are) at just under the speed of light they would have thought you were crazy. The point is that I'm not making any assumptions on what they can do. All I'm doing is asking what they would do if they could. And I believe that if they were able to study us before they made contact they would do that, and that it would be foolish to not do that if they had the capability. Won't antimatter still require propellant? Won't it put out heat? They're still bound by the rocket equation and may have to decide what to do before studying us.


Eventually, I don't argue that we would figure it out. But electricity isn't the only game in town. And even in our own electronics, the theory of how it all works isn't complete. We aren't able to manufacture a transistor with a specific gain. All we are able to do is manufacture it within a range of gain. There are still tremendous improvements we could make just in manufacturing of our existing technology that an experienced engineer would have a tough time understanding if it was just thrown in his lap from a hundred years in the future. So, could we figure it out? Yes, probably. But when you consider that it may be unrecognizable to us, it may take a very long time.

Are you talking about spintronics, quantum computing and stuff like that? It's being looked into. We may not have the abilities to replicate it due to not-yet developed manufacturing techniques, but that doesn't mean that the design concept is necessarily unknown, nor the basic physics. The problem may be due to a lack of destructive exploration of a device if they are in limited supply.

primummobile
2012-Aug-08, 07:06 PM
Won't antimatter still require propellant? Won't it put out heat? They're still bound by the rocket equation and may have to decide what to do before studying us.

Propellant? It depends on what type of antimatter rocket you want to build. The easiest would be using the heat of a matter/antimatter reaction to raise the temperature of a propellant in a constant velocity chamber and allow that to escape through an engine nozzle at high velocity, just like our rockets do now. It is also a terrible waste of antimatter.

A more efficient antimatter engine would magnetically direct the highly charged particles travelling at around .5c from antimatter/matter annihilation out the engine nozzle to produce thrust. One gram of antimatter annihilating with one gram of matter produces about 180 terajoules and this type of antimatter rocket is thought to have a specific impulse as high as ten million seconds. For comparison, a solid rocket has a specific impulse of around 250 seconds and a liquid propellant rocket is about twice that. An ion thruster has a specific impulse of around 3,000 seconds. So, the "miles per gallon" of an antimatter rocket would be about 3300 times better than an ion thruster rocket. The point is that if the aliens have the know-how and can carry enough lightweight high-octane fuel to accelerate to a significant velocity, coast for a while, and then slow down at the other end they would do that.

I don't know what putting out heat has to do with that. If it's referring to Noclevername's argument it should be noted that I never said they would try to stay hidden before studying us. I said they would try to study us before offering us technology or attempting to make contact. Others assumed that they would need to be hidden to do that, and at that I argued that they could hide if they wanted to. In my discussion with you, the idea of needing to hide hasn't come up, to my knowledge, so I wasn't considering that.




Are you talking about spintronics, quantum computing and stuff like that? It's being looked into. We may not have the abilities to replicate it due to not-yet developed manufacturing techniques, but that doesn't mean that the design concept is necessarily unknown, nor the basic physics. The problem may be due to a lack of destructive exploration of a device if they are in limited supply.

I don't argue that. My point is that the same thing from then may be [I]radically different from how we would design it. If it uses a power source that is not electrons and holes moving in a conductive material we may be scratching our heads about it for quite a while. If applying an electrical current to it causes nothing to happen we wouldn't be able to do much to discern its purpose without quite a bit of thinking. We may think it is a weapon. They may give us a quantum computer and we may interpret it as them giving us a cup of water. The possibilities are endless. Giving any kind of technology to someone who doesn't understand how to use it is potentially very dangerous.

Noclevername
2012-Aug-08, 07:44 PM
Noclevername, you're not getting me, which is probably my fault. All I'm saying is that if they can travel here they can probably hide themselves. There are more ways to do that besides just not putting out any heat. They could actively block our detection of them. They could 'fool' our instruments into thinking they were something more benign. The US military invests a lot of money into doing those sorts of things. They're doing research now, all over the world, into how to make objects "invisible" not only to radar, but also to visible light. Every method involves actively projecting what you want others to see rather than just hunkering down and hoping you aren't noticed.

But for the ETs to know that much about our technology and/or biology that they could spoof our optics and other sensors at will, they would have to have studies us and our gear in great detail... you see where I'm going with this?

eburacum45
2012-Aug-08, 07:44 PM
An antimatter rocket would be phenomenally detectable; stealth would be impossible with that kind of drive. They would emit vast amounts of gamma rays and neutrinos, for a start, both of which are tricky to convert into thrust.

primummobile
2012-Aug-08, 07:55 PM
But for the ETs to know that much about our technology and/or biology that they could spoof our optics and other sensors at will, they would have to have studies us and our gear in great detail... you see where I'm going with this?

Yes, I do. That's why you should take a closer look at the fly on your wall! : )

See my above post to Ara Pacis. When I said "make themselves known" I meant "communicate". Like when you walk into a room full of people, you're not hiding, but you haven't made yourself known until you speak up. Despite that, I still think they could blind us to their presence if they were sufficiently advanced. I just want to make clear that although I think they could hide, I don't think they would have to hide to study us. It's true that we may change our behavior if we know they are watching, but I don't think it would change that much. You're talking about 7 billion people.

primummobile
2012-Aug-08, 08:06 PM
An antimatter rocket would be phenomenally detectable; stealth would be impossible with that kind of drive. They would emit vast amounts of gamma rays and neutrinos, for a start, both of which are tricky to convert into thrust.

Ok, we're having two different conversations here. One is could they stop and hang around, and the other is could they hide. The antimatter rocket is in the "could they get here, stop, and hang around" thread. I'm not making any assumptions about what kind of technology they could have other than to say that they may be able to be some pretty phenomenal things that would appear to us to be magic. In that vein, it's not a stretch to think they could do all kinds of things that we can't even imagine.

As for gamma rays and particles, they would have to reach us to be detectable. We have no idea even how to generate that much antimatter. With our technology, it would take us about a billion years to generate even one gram of antimatter, and we would lose nearly all of it before we were finished. The questions of how we would direct the particles (not the gamma rays) out the exhaust nozzle to create thrust are huge. A technology that could accomplish this would have to be far in advance of anything that will exist on Earth for a long time. If we were to build an antimatter rocket today with what we know today, it would be phenomenally detectable. I don't doubt that you are right that it will be that way for any level of technology. I have no idea how you would stop a stream of neutrinos. But that doesn't mean there isn't a way to do it.

Noclevername
2012-Aug-08, 08:16 PM
I'm not making any assumptions about what kind of technology they could have other than to say that they may be able to be some pretty phenomenal things that would appear to us to be magic. In that vein, it's not a stretch to think they could do all kinds of things that we can't even imagine.


Going back to the OP, if their technology is so different from what we understand that it violates the known laws of physics, it would be inoperable let alone impossible to copy by humans. It would also invalidate all our physical sciences.

primummobile
2012-Aug-08, 08:26 PM
Going back to the OP, if their technology is so different from what we understand that it violates the known laws of physics, it would be inoperable let alone impossible to copy by humans. It would also invalidate all our physical sciences.

That's true, but I don't think it would necessarily have to go that far. Obviously there is a limit to what technology can do, but I personally think that we're pretty far from that limit. I think if you could fast forward a thousand years you would be blown away by what you find.

Noclevername
2012-Aug-08, 08:39 PM
That's true, but I don't think it would necessarily have to go that far.

But that's the point. To do the things you describe, it would have to be that far.

primummobile
2012-Aug-08, 08:40 PM
And don't forget too that the 'known laws of physics' allow for some pretty weird things that we're highly unlikely to ever see.

primummobile
2012-Aug-08, 08:41 PM
But that's the point. To do the things you describe, it would have to be that far.

We may have to just agree to disagree on that.

Noclevername
2012-Aug-08, 08:45 PM
Well, I tried. :(

Ara Pacis
2012-Aug-08, 09:05 PM
Propellant? It depends on what type of antimatter rocket you want to build. The easiest would be using the heat of a matter/antimatter reaction to raise the temperature of a propellant in a constant velocity chamber and allow that to escape through an engine nozzle at high velocity, just like our rockets do now. It is also a terrible waste of antimatter.

A more efficient antimatter engine would magnetically direct the highly charged particles travelling at around .5c from antimatter/matter annihilation out the engine nozzle to produce thrust. One gram of antimatter annihilating with one gram of matter produces about 180 terajoules and this type of antimatter rocket is thought to have a specific impulse as high as ten million seconds. For comparison, a solid rocket has a specific impulse of around 250 seconds and a liquid propellant rocket is about twice that. An ion thruster has a specific impulse of around 3,000 seconds. So, the "miles per gallon" of an antimatter rocket would be about 3300 times better than an ion thruster rocket. The point is that if the aliens have the know-how and can carry enough lightweight high-octane fuel to accelerate to a significant velocity, coast for a while, and then slow down at the other end they would do that. And what is the thrust and how long in time and space would it take for them to decelerate into an orbit somewhere in the Sol system? If their exhaust is visible, as current science suggests it must be, then we may see them before they see us.


I don't know what putting out heat has to do with that. If it's referring to Noclevername's argument it should be noted that I never said they would try to stay hidden before studying us. I said they would try to study us before offering us technology or attempting to make contact. Others assumed that they would need to be hidden to do that, and at that I argued that they could hide if they wanted to. In my discussion with you, the idea of needing to hide hasn't come up, to my knowledge, so I wasn't considering that. I had already mentioned them possibly hiding and having been here already as a possibility to avoid the idea that we would see them decelerate. If they are already here, we may not have seen them decelerate or have known what it was if we did see it if they came before we had enough knowledge to understand what we were seeing. I include letting themselves be known and communicating in the same concept of first contact. If we see them, they've communicated that fact to us through their actions. Communication can be non-verbal, ya know. And then if we see them despite their best efforts, we may try to communicate with them first, and even if they don't respond, that in and of itself is telling.


I don't argue that. My point is that the same thing from then may be [I]radically different from how we would design it. If it uses a power source that is not electrons and holes moving in a conductive material we may be scratching our heads about it for quite a while. If applying an electrical current to it causes nothing to happen we wouldn't be able to do much to discern its purpose without quite a bit of thinking. We may think it is a weapon. They may give us a quantum computer and we may interpret it as them giving us a cup of water. The possibilities are endless. Giving any kind of technology to someone who doesn't understand how to use it is potentially very dangerous.

If we're left to figure it out ourselves, it may take a while. I think the original context was that they were trying to explain it. Once we overcome the language barrier, the science and math should flow fairly easily.

IsaacKuo
2012-Aug-08, 09:33 PM
If they wanted to hide from us, one method would be to decelerate hidden behind the Sun. We might see the deceleration phase in a lucky snapshot from Cassini, but the chances of that would be very low.

Ara Pacis
2012-Aug-09, 04:17 AM
If they wanted to hide from us, one method would be to decelerate hidden behind the Sun. We might see the deceleration phase in a lucky snapshot from Cassini, but the chances of that would be very low.

How fast would that be before it was visible again? (Assuming we don't have other observatories anywhere in the solar system that might see it and the aliens may or may not happen to know about.)

DoggerDan
2012-Aug-09, 08:05 AM
And don't forget too that the 'known laws of physics' allow for some pretty weird things that we're highly unlikely to ever see.

Er... What? Please elaborate. I'm all ears.

primummobile
2012-Aug-09, 09:43 AM
Er... What? Please elaborate. I'm all ears.


Please. QM allows for objects to pass through walls. You'll never see it, but it's still possible. GR allows wormholes. You'll never see one, but it's still possible. I could go on and on but I'm not going to parrot stuff you already know to satisfy you.

primummobile
2012-Aug-09, 11:38 AM
And what is the thrust and how long in time and space would it take for them to decelerate into an orbit somewhere in the Sol system? If their exhaust is visible, as current science suggests it must be, then we may see them before they see us.

I have no idea. Not I nor anyone else knows exactly how an antimatter rocket using charged subatomic particles for thrust would work. I'm just giving you an example of how it could work.


If we see them, they've communicated that fact to us through their actions. Communication can be non-verbal, ya know. And then if we see them despite their best efforts, we may try to communicate with them first, and even if they don't respond, that in and of itself is telling.

I agree. But there's no telling how we would interpret what we see. If it's something really unusual it could just be shelved for later investigation. When we first discovered quasars they were a complete mystery and no one was getting very excited about trying to figure out what they were. Granted, something in or close to our own solar system may generate some more excitement, but I'm not talking about the mother ship from Independence Day, with a quarter the mass of the moon, slowing down and stopping between the Earth and the moon. I'm talking about ships that may be relatively small and could swing into orbit perhaps near the Kuiper Belt and still pick up some of our transmissions from only around seven light hours away. How much excitement do you think that would really generate? Even if we saw it, do you really think people would interpret it as an alien craft?

I realize there are other methods of communication that aren't explicit. But if the listener interprets it as something else then it's not very effective communication. Personally, whatever happened up there in the heavens would have to be pretty dramatic to convince me that it was an alien ship or probe and not something natural.




If we're left to figure it out ourselves, it may take a while. I think the original context was that they were trying to explain it. Once we overcome the language barrier, the science and math should flow fairly easily.

I agree completely. Math is math and physics is physics. That doesn't change. Only the notation changes.

primummobile
2012-Aug-09, 11:41 AM
Well, I tried. :(

Sorry, I'm just more starry-eyed than you are. I happen to believe that we have barely scratched the surface of what is possible, and have dreamed only a small part of what is possible.

IsaacKuo
2012-Aug-09, 03:01 PM
How fast would that be before it was visible again? (Assuming we don't have other observatories anywhere in the solar system that might see it and the aliens may or may not happen to know about.)
I don't know if I understand your question. If they decelerated behind the Sun, it wouldn't ever be visible to us. It would occur behind the Sun. The Sun conceals an infinitely large cone about half a degree across behind it, but this cone is sweeping across space due to the motion of Earth. Earth orbits about 1 degree per day, so the practical limit of this concealment is about 12 hours--give or take a few factors depending on motion alignment with the direction of sweep. Assuming an acceleration of 1km/s/s, that's enough time for deceleration from 14% of c. An acceleration of 10km/s/s would be sufficient for high fractions of c. We already design robotics to survive 100km/s/s accelerations (guided artillery rounds).

Ara Pacis
2012-Aug-09, 05:21 PM
I don't know if I understand your question. If they decelerated behind the Sun, it wouldn't ever be visible to us. It would occur behind the Sun. The Sun conceals an infinitely large cone about half a degree across behind it, but this cone is sweeping across space due to the motion of Earth. Earth orbits about 1 degree per day, so the practical limit of this concealment is about 12 hours--give or take a few factors depending on motion alignment with the direction of sweep. Assuming an acceleration of 1km/s/s, that's enough time for deceleration from 14% of c. An acceleration of 10km/s/s would be sufficient for high fractions of c. We already design robotics to survive 100km/s/s accelerations (guided artillery rounds).

That's what I was asking, thanks. I wasn't sure. But it might be blind chance that they happen to have a trajectory that takes them into that infinite cone if they didn't know Earth was inhabited before they launched (assuming their point of origin allowed such a trajectory). And then there'd have to be some sort of propulsion system that could manage such high accelerations. Perhaps a probe might survive such high accelerations, but a ship with biological inhabitants? If my math is right, 1km/s/s is 102g, and 10km/s/s is 1020g. Isn't that chunky salsa territory?

And as I said, it assumes we don't have our own probes in other orbits around the solar system that would be able to see that blind spot. If the aliens don't know if someone is here, then why bother. If they just do it out of precaution, then they know there's a good chance that any life able to see them and understand what they see will have observatories that are off-axis and would nullify the advantages of making such a maneuver.

IsaacKuo
2012-Aug-09, 07:09 PM
That's what I was asking, thanks. I wasn't sure. But it might be blind chance that they happen to have a trajectory that takes them into that infinite cone if they didn't know Earth was inhabited before they launched (assuming their point of origin allowed such a trajectory).
If they were headed anywhere except our solar system, it would be extremely unlikely they would pass anywhere close to our star system anyway. So, whenever they decide that Earth is interesting, they would need to have sufficient delta-v capability to send something our direction anyway.

By the way, there is no special alignment necessary. The worst case scenario is if they are headed toward us from directly above or below the ecliptic plane. In that case, there's no getting around the 12 hour limit. The shadow is sweeping perpendicular to the direction of motion.

The best case scenario is if they are headed toward us from somewhere along the ecliptic plane. In that case, it's possible to time the arrival to the time of year when the shadow is sweeping away from their point of origin. That way, it's possible to conduct the deceleration phase while the shadow is sweeping in the same direction as the starship's motion, significantly extending the time available to decelerate.

The shadow is accessable from any direction, in any case.


And then there'd have to be some sort of propulsion system that could manage such high accelerations. Perhaps a probe might survive such high accelerations, but a ship with biological inhabitants? If my math is right, 1km/s/s is 102g, and 10km/s/s is 1020g. Isn't that chunky salsa territory?

Maybe, maybe not. It's hard to say even for future humans. Practical interstellar travel for humans could plausibly be strictly limited to ranges under 10 parsecs without some sort of suspended animation or extreme life extension technologies. Without those, longer trips may be impractical simply due to lifespan limits. Such short trips would make the sort of diversion scenario posited pretty much impossible. With some sort of suspended animation or extreme life extension technologies, survival of 100 gees or even 1000 gees may be trivial. It might even be typically used for starships due to the way it makes acceleration/deceleration easier (you don't need extremely long ranged acceleration beams/tracks).

Without such a diversion scenario, it might still be practical to send a robotic probe rather than diverting the entire starship.


And as I said, it assumes we don't have our own probes in other orbits around the solar system that would be able to see that blind spot. If the aliens don't know if someone is here, then why bother.

In the scenario we're discussing, they are hiding from us. Obviously, this scenario assumes that they are aware of our existence.


If they just do it out of precaution, then they know there's a good chance that any life able to see them and understand what they see will have observatories that are off-axis and would nullify the advantages of making such a maneuver.

It may be extremely obvious to the aliens that we have practically no development of space technology. For example, we obviously lack space based solar power satellites, or a cluster of space based industrial satellites, or a cluster of space colonies. Any of these would involve huge areas of solar arrays in orbit, and this is the sort of thing which any technological civilization with any half decent space technology capability would have.

Ara Pacis
2012-Aug-09, 09:06 PM
If they were headed anywhere except our solar system, it would be extremely unlikely they would pass anywhere close to our star system anyway. So, whenever they decide that Earth is interesting, they would need to have sufficient delta-v capability to send something our direction anyway.

By the way, there is no special alignment necessary. The worst case scenario is if they are headed toward us from directly above or below the ecliptic plane. In that case, there's no getting around the 12 hour limit. The shadow is sweeping perpendicular to the direction of motion.

The best case scenario is if they are headed toward us from somewhere along the ecliptic plane. In that case, it's possible to time the arrival to the time of year when the shadow is sweeping away from their point of origin. That way, it's possible to conduct the deceleration phase while the shadow is sweeping in the same direction as the starship's motion, significantly extending the time available to decelerate.

The shadow is accessable from any direction, in any case.Ahh, I see your point now, but it constrains that maneuver to when they are crossing that shallow disc of occasional eclipse. If they are far away, and moving slowly might take years with multiple eclipses once a year. If they are closer and moving faster, they may only get one opportunity with appropriately higher deceleration requirements. If they are coming here specifically, they may approach more directly, which means they may need data before launch as to whether there is life here (as well as knowing the actual orbit of Earth). Not to mention that since the sun is a sphere (circular cross-section), a more perpendicular trajectory would have less distance and time near the top and bottom than they would have in the middle because the moving cone of eclipse is narrower. Is that where you got the 12 hr estimate from?


Maybe, maybe not. It's hard to say even for future humans. Practical interstellar travel for humans could plausibly be strictly limited to ranges under 10 parsecs without some sort of suspended animation or extreme life extension technologies. Without those, longer trips may be impractical simply due to lifespan limits. Such short trips would make the sort of diversion scenario posited pretty much impossible. With some sort of suspended animation or extreme life extension technologies, survival of 100 gees or even 1000 gees may be trivial. It might even be typically used for starships due to the way it makes acceleration/deceleration easier (you don't need extremely long ranged acceleration beams/tracks).What sort of technologies or biologies are you suggesting?


Without such a diversion scenario, it might still be practical to send a robotic probe rather than diverting the entire starship.If passing near with no intent to stop, sure. Which is why I was focusing on them either coming here in person or contacting us by radio.


In the scenario we're discussing, they are hiding from us. Obviously, this scenario assumes that they are aware of our existence.Which is one of the problems. How do they know we're here?


It may be extremely obvious to the aliens that we have practically no development of space technology. For example, we obviously lack space based solar power satellites, or a cluster of space based industrial satellites, or a cluster of space colonies. Any of these would involve huge areas of solar arrays in orbit, and this is the sort of thing which any technological civilization with any half decent space technology capability would have.

And that would show that the aliens may be peaceful or naive because most military planners base their estimations of a potential threat on capability and not intent, and capability isn't always obvious from observation. Assuming we don't have space defense capability because we don't bother do to space mining might be a dangerous and potentially fatal assumption on their part if they ever met another alien race that simply didn't like using that tech for some reason but knew how. Did you ever see the "Stargate: SG-1" episode where they first meet the Nox?

IsaacKuo
2012-Aug-09, 10:04 PM
Ahh, I see your point now, but it constrains that maneuver to when they are crossing that shallow disc of occasional eclipse. If they are far away, and moving slowly might take years with multiple eclipses once a year. If they are closer and moving faster, they may only get one opportunity with appropriately higher deceleration requirements.

No, there's just one shot. There isn't going to be multiple eclipses. There can't be, unless the approach path is along the ecliptic plane, and even then it's not practical.


If they are coming here specifically, they may approach more directly, which means they may need data before launch as to whether there is life here (as well as knowing the actual orbit of Earth).

I presume that they will have telescopes, with which they can chart Earth's orbit and detect life on Earth from wherever they launched from. We're already making serious progress toward that sort of capability.


Not to mention that since the sun is a sphere (circular cross-section), a more perpendicular trajectory would have less distance and time near the top and bottom than they would have in the middle because the moving cone of eclipse is narrower. Is that where you got the 12 hr estimate from?
No, I have no idea what you're even thinking there. The 12 hour estimate is simply the length of time that a faraway point along the ecliptic plane would remain within the half degree shadow cone as it sweeps across space at about 1 degree per day. To a first approximation, the deceleration run takes place at a single point--this is accurate if the deceleration run takes place very far away, but it becomes less accurate if it takes place closer to the sun.

What sort of technologies or biologies are you suggesting?
With future humans, suspended animation might involve immersion in neutrally buoyant fluid and/or freezing the body. The frozen humans might be tolerant of high accelerations. Extreme life extension technologies might involve active robotics on a subcellular level. That could also make the humans tolerant of high accelerations, by carefully balancing density to maintain neutral buoyancy to a cellular resolution.

With alien biologies, the possibilities are endless. Obviously, aliens which had evolved in an extreme gravity environment could be naturally tolerant of high accelerations. Aliens which evolved in underwater environments might be naturally neutrally buoyant and thus naturally tolerant of high accelerations. Aliens which evolved in an environment with extremely rough winds or water currents might be naturally tough enough to survive extreme accelerations as they're pummeled against rocks.


Which is one of the problems. How do they know we're here?

Either telescopic observations, or detections of our radio signals.


And that would show that the aliens may be peaceful or naive because most military planners base their estimations of a potential threat on capability and not intent, and capability isn't always obvious from observation. Assuming we don't have space defense capability because we don't bother do to space mining might be a dangerous and potentially fatal assumption on their part if they ever met another alien race that simply didn't like using that tech for some reason but knew how. Did you ever see the "Stargate: SG-1" episode where they first meet the Nox?

Eh, who says this is a military mission? Anyway, it would be obvious that humans aren't a military threat. Without any serious expansion into space, humanity is limited to the puny amount of energy falling onto the Earth's surface from the Sun. This is nothing compared to the resources available to an interstellar civilization. Humans would have to start expanding into interstellar space before they were even a noticeable threat.

Ara Pacis
2012-Aug-10, 06:16 PM
No, there's just one shot. There isn't going to be multiple eclipses. There can't be, unless the approach path is along the ecliptic plane, and even then it's not practical.

I presume that they will have telescopes, with which they can chart Earth's orbit and detect life on Earth from wherever they launched from. We're already making serious progress toward that sort of capability.

No, I have no idea what you're even thinking there. The 12 hour estimate is simply the length of time that a faraway point along the ecliptic plane would remain within the half degree shadow cone as it sweeps across space at about 1 degree per day. To a first approximation, the deceleration run takes place at a single point--this is accurate if the deceleration run takes place very far away, but it becomes less accurate if it takes place closer to the sun.The last statement contradicts the first. I was going to say that they only have one shot to hide in the cone of eclipse, but then realized it would technically be incorrect if they were far enough away and/or slow enough. Although to be technically correct, they might not even have 1 chance if they are too close and didn't plan for it (assuming they have the capability to conduct such high acceleration maneuvers).

What sort of life? They might be able to sense gases in the atmosphere, but I think we had a thread about seeing signs of civilization the conclusion of which was it was not technically possible using known physics. Iv'e also read that it's unlikely that our radio data signals could be detected very far away with RADAR a bit farther, and that there's a low chance that anyone would happen to see it and even if they did, there wouldn't be enough information to learn anything about our life-form other than something is emitting radio signals.


With future humans, suspended animation might involve immersion in neutrally buoyant fluid and/or freezing the body. The frozen humans might be tolerant of high accelerations. Extreme life extension technologies might involve active robotics on a subcellular level. That could also make the humans tolerant of high accelerations, by carefully balancing density to maintain neutral buoyancy to a cellular resolution.

With alien biologies, the possibilities are endless. Obviously, aliens which had evolved in an extreme gravity environment could be naturally tolerant of high accelerations. Aliens which evolved in underwater environments might be naturally neutrally buoyant and thus naturally tolerant of high accelerations. Aliens which evolved in an environment with extremely rough winds or water currents might be naturally tough enough to survive extreme accelerations as they're pummeled against rocks.Are you talking possibility or probability WRT life-forms? I was thinking about tech, and freezing in a breathable solution (cf. "The Abyss") using the new vitrification technique using strong electro-magnets, but I don't know if that would make those strong accelerations more survivable or less survivable.


Either telescopic observations, or detections of our radio signals.See above.


Eh, who says this is a military mission? Anyway, it would be obvious that humans aren't a military threat. Without any serious expansion into space, humanity is limited to the puny amount of energy falling onto the Earth's surface from the Sun. This is nothing compared to the resources available to an interstellar civilization. Humans would have to start expanding into interstellar space before they were even a noticeable threat.

It doesn't have to be a military mission to have military repercussions. They'd have to know our capabilities before they get here, which isn't going to happen. And it would be silly for them to assume we're limited to solar energy of some sort and haven't developed nuclear power, unless they don't know about nuclear power, which seems like a silly assumption for a race we're presuming as space-faring. And if they'd only think of us as a threat if we expand into interstellar space, then they may want to re-think the idea of sending a ship or probe with interstellar transportation tech to us (assuming there is such a thing we don't already know about or won't develop from known physics eventually).