Fermi paradox

[Jek Jek Roo]

extraterrestials? maybe, highly intelligent? I doubt that.

[Dr.Bill]

If we find some.I suggest enslaving them and robbing their home planet of anything precious to improve our own,give them a taste of humanity.I mean,what else can we do with space aliens?

 

 

Now that my mentally ill side has said,what it said.We can continue the civilized discussion.

[BTGBullseye]

Ok, on to the civilized discussion... How would we have sex with them?

[Seattleite]

Aliens have much better stealth technology than us.

 

There's no stealth in space. You can't conceal your exhaust, reflectivity or the infrared emissions from your ship's relative heat. Unless you have FTL. In which case, there's not much chance of of any civilization detecting you until you pass them. Though, depending on how it works, that might make it incredibly obvious you were there to anybody who you passed, and if they have FTL they can warn those ahead, but that's a bit of a moot point. Or you could use teleportation to move around without making a lot of heat, that's stealthy-ish. Either one is a bit far fetched, and you ARE still detectable, just only in poor circumstances.

 

And... BTG? Let's wait to see what they look like first, and find out enough about their biology and culture to see if it's safe, THEN we can worry about sex. Good thing is, convergent evolution is a massive possibility, they may well be humanoid. Or they might not, if their environment is drastically different from ours. Either way, though, they're almost certain to reproduce sexually and internal fertilization is the most effective means if their environment is like ours, so this might totally be an option.

[Vapymid]

The stealth in space is provided by the sheer distances involved. The inverse-square law of attenuation of radiation means that relatively low-energy source like an engine exhaust will not be detectible at anything like interstellar ranges.

 

Regards

[Seattleite]

The stealth in space is provided by the sheer distances involved. The inverse-square law of attenuation of radiation means that relatively low-energy source like an engine exhaust will not be detectible at anything like interstellar ranges.

 

Regards

 

I do believe you are missing context here.

[Vapymid]

If I am, that escapes me

 

Regards

[Seattleite]

If I am, that escapes me

 

Regards

 

She specifically referred to "stealth technology". A thing that is largely impossible in space, no technology significantly disguises engine exhaust or infrared radiation emitted by the hot ship. Even if such a thing was possible, without the infrared emitted to radiate off waste heat, the ship would *cook*.

[Vapymid]

Ah, OK.

 

For close-range stealth, you can direct and focus the exhaust away from expected detectors; directionally radiate waste heat using lasers; use cloaking devices for quasi-transparency and resistance to active detection.

 

If you keep your ship on station for long time for surveillance purposes you don't need propulsion as you can place it in a solar orbit and the heat management then should not be difficult even with our existing technology - put your station inside a much larger asteroid and the excess heat radiating away (given the surface area of the shell asteroid) will be negligible even without the gimmicks like lasers etc.

 

Regards

[Seattleite]

Ah, OK.

 

For close-range stealth, you can direct and focus the exhaust away from expected detectors; directionally radiate waste heat using lasers; use cloaking devices for quasi-transparency and resistance to active detection.

 

If you keep your ship on station for long time for surveillance purposes you don't need propulsion as you can place it in a solar orbit and the heat management then should not be difficult even with our existing technology - put your station inside a much larger asteroid and the excess heat radiating away (given the surface area of the shell asteroid) will be negligible even without the gimmicks like lasers etc.

 

Regards

 

Directing exhaust away accomplishes very little. The heat coming off the exhaust will still give you away with huge amounts of infrared radiation anytime you try to change the ship's velocity, positively or negatively.

Directionally radiating heat is ridiculous. Heat radiates on its own, naturally, from all directions, and for your information lasers don't work like that either.

If you're close enough to see anything on the surface of a planet, everything we have here to observe space, especially the other things in space, can see you plain as day. I mean, we're good enough at this to spot planets around orbiting stars and determine their composition from hundreds of light years away, I'm pretty damn sure we can spot a spaceship in orbit. Unless the government knows damn well they're there and is hiding it, which they'd totally do I admit, there's no way they'd stay an unknown.

The only rock close enough to observe the surface of Earth that could hide them is the moon. So you're saying what, aliens could be hiding on the moon? You don't say. But that doesn't change the fact that if they leave the moon their ships will be visible to anybody with simple a telescope, so there's just about no way NASA wouldn't pick them up the infrared on its sensors, so either they're not hiding there, not leaving it much, or NASA is totally aware that they are there and isn't telling anybody. Which, actually, fits with what we know of the US government.

 

So space being what it is, if they're getting close enough to be relevant to us at all, any government with a space program absolutely knows they exist and isn't telling anyone. While I can believe that quite well and that seems to be the most likely explanation, the truth is still that they can't be this close without *somebody* knowing.

 

Actually, that might explain all those UFO sightings and alien landings, to the point where so damned many people know about them, if we're relying on national governments to cover up their presence when they screw up or periodically just decide "fuck stealth" and harass a town for a couple months. (Like Colares, Brazil, in 1977.) Maybe people shouldn't be so quick to dismiss sightings and look into the story first before calling "hoax".

[Vapymid]

I think you may need to radiate some accumulated heat, directionally or otherwise

 

Maybe you should first define your alien spooks mission parameters and then we discuss? Otherwise, you are moving goalposts every time.

 

You are saying the aliens can only observe the Earth from not farther away than the Moon, yet Nasa can magically spot them anywhere in the Solar system (with the very same NASA being constantly surprised by asteroids passing unexpectedly between Earth and Moon). We can't see even our own spacecraft from Earth unless they actively transmit.

 

We have just lost a big aircraft right here on Earth and no one can even say remotely where the frack did it go.

 

Extrasolar planets are being detected, yes, but because they affect the light from their stars and we can indirectly deduce that something must be there.

 

We know we must have thousands of asteroids in the Solar system which have not yet been found and most of those already discovered we only observed a couple of times each. Every one of them can potentially house an alien observation post and we have no chance in hell to detect it, unless by pure chance. Our telescopes don't even have the resolution to see asteroids' surface from Earth, neither in optical nor in IR.

 

Basically, there is no escaping the fact that there may be hundreds of alien ships, bases and stations in the Solar system without us knowing anything about them.

 

I am not saying they are here but they may be and we should not overestimate our abilities to detect them.

 

Regards

 

P.S. I don't see why you are so categorical about lasers - if you design a laser that can be pumped with IR radiation from the internally collected waste heat, it will then radiate it out as a coherent beam which will be virtually undetectable unless it is directed at you. OK, we don't have this now but we started from the assumptions that the alien's technology is more advanced than ours...

[Seattleite]

I think you may need to radiate some accumulated heat, directionally or otherwise

 

Maybe you should first define your alien spooks mission parameters and then we discuss? Otherwise, you are moving goalposts every time.

 

Let's assume that they just want to observe human activity on our planet. Keep tabs on the new kids on the interstellar block, for whatever reason. That's as little as they can be doing and still be at all relevant to us at this point in time.

 

You are saying the aliens can only observe the Earth from not farther away than the Moon, yet Nasa can magically spot them anywhere in the Solar system (with the very same NASA being constantly surprised by asteroids passing unexpectedly between Earth and Moon). We can't see even our own spacecraft from Earth unless they actively transmit.

 

An *accelerating* spaceship produces a MASSIVE amount of heat that no amount of technological advancement could ever conceal. Human activity doesn't. And it's in the atmosphere. You need to be a LOT closer to observe human activity than you do to pick up a hot trail of rocket exhaust.

 

We have just lost a big aircraft right here on Earth and no one can even say remotely where the frack did it go.

 

There's a huge difference between detecting things in atmosphere with significant parts of a PLANET in the way, and detecting something (especially something larger and more energetic) outside of the atmosphere with almost nothing in the way.

 

Extrasolar planets are being detected, yes, but because they affect the light from their stars and we can indirectly deduce that something must be there.

 

No, no, no. We aren't just detecting them. We're measuring their composition with mass spectrometers from hundreds of light years away. That takes some damned impressive equipment.

 

We know we must have thousands of asteroids in the Solar system which have not yet been found and most of those already discovered we only observed a couple of times each. Every one of them can potentially house an alien observation post and we have no chance in hell to detect it, unless by pure chance. Our telescopes don't even have the resolution to see asteroids' surface from Earth, neither in optical nor in IR.

 

No, but if they ever leave it, or go to it, we can see the infrared coming off massive trail of plasma erupting from the back of their ships. And if they come close enough to observe surface activity, we can detect them by their cabin heat alone.

 

Basically, there is no escaping the fact that there may be hundreds of alien ships, bases and stations in the Solar system without us knowing anything about them.

 

I am not saying they are here but they may be and we should not overestimate our abilities to detect them.

 

They would have to erase the laws of physics to remain undetectable anywhere between here and the moon, and because of the limits on magnification they'd need to be that close to observe surface activity optically, and neither radar nor IR will work from further off through an atmosphere, not with any precision.

 

Regards

 

P.S. I don't see why you are so categorical about lasers - if you design a laser that can be pumped with IR radiation from the internally collected waste heat, it will then radiate it out as a coherent beam which will be virtually undetectable unless it is directed at you. OK, we don't have this now but we started from the assumptions that the alien's technology is more advanced than ours...

 

You can't just collect waste heat and turn it into photons and fire it away from your ship. Lasers can't do that. So you can't dispose of waste heat that way. The only option is to allow it to radiate off naturally (as it'll do anyway, no matter how hard you try to stop it) and that's detectable. The hotter your ship gets, the more visible it'll be to infrared sensors, and if you're running powerful sensors, computers, or anything of that nature there should be a considerable heat signature. Even just life support, even if the life support is handled with personal space suits instead of a full ship system, will also great an at least noticeable amount of heat, which will become an at least noticeable amount of infrared radiation for our sensors to pick up. Since there's nothing significant to absorb it between their ships and our sensors, we can detect them from much farther off than in atmosphere, and our equipment is quite sensitive.

 

There is no stealth in space.

[Vapymid]

Let's assume that they just want to observe human activity on our planet. Keep tabs on the new kids on the interstellar block, for whatever reason.

 

OK. If I were them I would place autonomous probes *on the surface* near the most interesting targets. The probes would gather the data and directionally burst-transmit it at regular intervals to listening posts in the asteroid belt. There I would, in addition, place some *large* passive sensors which will collect long range sigint and register and track anything leaving out of or arriving anywhere on to an Earth orbit. From the Asteroid belt I would directionally burst-transmit the data to a relay station in Kuiper belt. None of my assets will use any form of propulsion, except in emergencies.

 

We're measuring their composition with mass spectrometers from hundreds of light years away.

 

Not mass spectrometry, it's impossible to do it from a distance. EM spectrometry (including radio, IR, visible, UV, X-Ray and gamma) and interferometry have to be used.

 

These planets have the benefit of having a great shining floodlight behind them, which lets us see enough light to detect any signals (dipping intensity, doppler drifts, gravitational microlensing etc). AFAIK, very few planets have so far been detected by direct imaging and those are all extremely hot giants. All lower mass planets are being discovered indirectly. All of it involves long observations with large or space-based telescopes with very small field of view and not suitable for sweeping search.

 

They would have to erase the laws of physics to remain undetectable anywhere between here and the moon

 

In my scenario they will only appear at that distance on very few occasions. For landing the probes they don't need to be hidden - they will just look like meteorites as they fall. For short-term detailed observations of the events of interest they can be shrouded and use the perturbation theory to change their orbits with very short and low-power bursts (if, of course, they don't use some kind of gravitic propulsion, in which case they can fly around at will).

 

You can't just collect waste heat and turn it into photons and fire it away from your ship. Lasers can't do that.

 

Why not? This is a basic technique of lasing, demonstrated in 1950s.

 

http://en.wikipedia.org/wiki/Optical_pumping - you use light (which can be IR) to excite the gain medium of the laser.

 

As for heat and photons - *any* radiation of heat is done via photons, there is no other way to do it AFAIK.

 

Regards

[ThePest179]

Guys, you know there's a lot more factors involved in explaining why we haven't contacted extraterrestrials, right? Not having sufficient tech to get here might be one, but there's DOZENS.

[Seattleite]

Let's assume that they just want to observe human activity on our planet. Keep tabs on the new kids on the interstellar block, for whatever reason.

 

OK. If I were them I would place autonomous probes *on the surface* near the most interesting targets. The probes would gather the data and directionally burst-transmit it at regular intervals to listening posts in the asteroid belt. There I would, in addition, place some *large* passive sensors which will collect long range sigint and register and track anything leaving out of or arriving anywhere on to an Earth orbit. From the Asteroid belt I would directionally burst-transmit the data to a relay station in Kuiper belt. None of my assets will use any form of propulsion, except in emergencies.

 

One word retort: Blooming.

 

Expansion: Undetectable transmissions are impossible in-atmosphere due to the atmosphere not being totally transparent. Some refraction and absorption will always remain. If these transmissions are frequent, they'll get worse with each shot due to this.

 

Not to mention you're trusting unmaintained machines to do this. That might be okay on mars, with its thin, dry atmosphere, but on Earth corrosion makes that untenable. They'd need maintainance on the ground. In all circumstances, personnel need supplies, as do equipment, so they need constant, visible shipments.

 

We're measuring their composition with mass spectrometers from hundreds of light years away.

 

Not mass spectrometry, it's impossible to do it from a distance. EM spectrometry (including radio, IR, visible, UV, X-Ray and gamma) and interferometry have to be used.

 

Semantics.

 

These planets have the benefit of having a great shining floodlight behind them, which lets us see enough light to detect any signals (dipping intensity, doppler drifts, gravitational microlensing etc). AFAIK, very few planets have so far been detected by direct imaging and those are all extremely hot giants. All lower mass planets are being discovered indirectly. All of it involves long observations with large or space-based telescopes with very small field of view and not suitable for sweeping search.

 

A few years ago you'd be right. We're finding terrestrial planets with this all the time. We're also finding them very, very, very quickly now. Keep up.

 

They would have to erase the laws of physics to remain undetectable anywhere between here and the moon

 

In my scenario they will only appear at that distance on very few occasions. For landing the probes they don't need to be hidden - they will just look like meteorites as they fall. For short-term detailed observations of the events of interest they can be shrouded and use the perturbation theory to change their orbits with very short and low-power bursts (if, of course, they don't use some kind of gravitic propulsion, in which case they can fly around at will).

 

Your scenario is untenable. The machines would break down and personnel to maintain them would die without supplies, they'd need supply shipments. Unless they're scavaging on-world, which is even MORE visible. They'd need help from people who can move around freely to manage this. That means locals.

 

Not to mention meteor impacts are already investigated and those that actually impact at all are rarities. If they're falling in the wilderness to avoid it, a crater with nothing in it is suspicious, and they'd need to move to observe anything and that's clearly detectable. Add on the difficulty of transporting personnel or fragile equipment like this and this plan looks like swiss cheese. *Somebody* would know. Lots of somebodies. They'd need local help to cover it up.

 

Why not? This is a basic technique of lasing, demonstrated in 1950s.

 

http://en.wikipedia.org/wiki/Optical_pumping - you use light (which can be IR) to excite the gain medium of the laser.

 

As for heat and photons - *any* radiation of heat is done via photons, there is no other way to do it AFAIK.

 

Regards

 

Optical pumping doesn't work like you seem to think. You can't just collect all your waste heat and turn it into a laser. Even if you could, it would NOT be completely efficient and you'd get visible heat buildup in the laser itself. This will not make a warm ship look cold. This is untenable.

[Vapymid]

Semantics

 

It is the attitude like that which causes resonance cascades, unforeseen consequences and stuff!

 

 

You seem to have an unshakable belief that there are lots of people on government payrolls around the world whose job it is to constantly monitor every square inch of visible sky for signs of possible alien invasion and also detect, log and decode every laser beam shone from anywhere on Earth towards the outer space.

 

I can assure you it is not the case. No government agency in the world has resources, budgets and desire to do anything like that. It is easy to hide stuff even here, in front of all the spies' eyes and in the big black space you currently can have a fleet of Star Destroyers parked in the asteroid belt and nobody will suspect they are even there.

 

Again, I would like to point out that to have a capability to discover an exoplanet is not the same as being able to search and detect transient targets, just like having a powerful microscope does not mean that you can use it to find, count and monitor every bacteria around you.

 

On technology, your objections are valid but they assume the technological level of Daleks. Even now we can do better than that - we can build machines that can work for years without maintenance, why would some aliens, who have already managed to cross the interstellar space to get here, not be able to?

 

All of the fancy technology I used as examples (cloaking shrouds, directed comms, laser heat dumps) is feasible based on what we know today. The concepts have been postulated and a lot of principles has even been demonstrated. In a hundred years or so we will have it become commonplace here. And I haven't even mentioned more exotic stuff like entanglement and teleportation, which more advanced extraterrestrials may as well have already implemented technologically.

 

Having thought further about our theoretical alien observers I think I would put at least a couple of their probes into the NSA - they will then have access to intercepted comms on the global scale. I would get all of my probes to tap into the internet so that they could pass their data to those which are landed in a remote location (say in Africa) where there is no risk at all that their transmissions can be detected. The probes can scavenge the power from the local grids, which will minimise the need for onboard generation.

 

I would also put some cloaked transponders in orbit right next to some defunct parked com satellites. They will never be spotted there and it will cut the required transmission power for the land based primary probes.

 

Sounds like good fun. We can write a whole SciFi novel like that

 

Regards

 

P.S. I have really taken your criticism of my laser heat dissipation idea to heart. You say it doesn't work like that - can you explain why do you think so?

 

P.P.S. Actually, it is not my idea at all. The first I read about it, I think, was in David Brin's "Sundiver"

Edited July 2, 2014 by Guest (see edit history)

[Vapymid]

Guys, you know there's a lot more factors involved in explaining why we haven't contacted extraterrestrials, right? Not having sufficient tech to get here might be one, but there's DOZENS.

 

Yep! But we seem to be discussing now the possibility that they may be here but we just don't know it.

 

Regards

[Seattleite]

You seem to have an unshakable belief that there are lots of people on government payrolls around the world whose job it is to constantly monitor every square inch of visible sky for signs of possible alien invasion and also detect, log and decode every laser beam shone from anywhere on Earth towards the outer space.

 

I said nothing of that nature. But given just how many people there are on this planet, and just how visible such a transmission would be due to blooming, it's unlikely to stay hidden very long.

 

I can assure you it is not the case. No government agency in the world has resources, budgets and desire to do anything like that. It is easy to hide stuff even here, in front of all the spies' eyes and in the big black space you currently can have a fleet of Star Destroyers parked in the asteroid belt and nobody will suspect they are even there.

 

You're severely underestimating the power of the crowd here. You wanted probes on the ground. These probes WILL be discovered, no matter how far out they are, by somebody. There is no way to hide probes close enough to observe humanity without humans eventually discovering at least some of them. It is SO much more likely that at least *some* people know they're here. It would take so many less assumptions, and so much less effort, and get so much more reward for them to just use local resources, and you know as well as I do how many governments would jump at the opportunity to cover up their existence and give them information in exchange for just about anything.

 

Again, I would like to point out that to have a capability to discover an exoplanet is not the same as being able to search and detect transient targets, just like having a powerful microscope does not mean that you can use it to find, count and monitor every bacteria around you.

 

Do you have any idea how many infrared sensors we have on this planet pointed towards space, or what many of them are for? Because most of them are there as part of our missile defence net, which picks up a rocket launch within minutes from across the planet. These are transient targets both smaller and less energetic than a space ship, and they pick them up even with the atmosphere in the way. Alien spaceships would stand NO CHANCE of evading detection by our missile net.

 

On technology, your objections are valid but they assume the technological level of Daleks. Even now we can do better than that - we can build machines that can work for years without maintenance, why would some aliens, who have already managed to cross the interstellar space to get here, not be able to?

 

Earth, that's why. This planet changes temperature frequently, has a corrosive atmosphere and a lot of moisture, strong winds and magnetic fields, natural disasters and violent inhabitants. Everything breaks down on Earth if given time.

 

All of the fancy technology I used as examples (cloaking shrouds, directed comms, laser heat dumps) is feasible based on what we know today. The concepts have been postulated and a lot of principles has even been demonstrated. In a hundred years or so we will have it become commonplace here. And I haven't even mentioned more exotic stuff like entanglement and teleportation, which more advanced extraterrestrials may as well have already implemented technologically.

 

Nothing allows stealth in space. Nothing ever has, nothing ever will. The best-case scenario is faster than light travel, which only makes you invisible until you've passed an observer and likely VERY visible once you have.

 

Having thought further about our theoretical alien observers I think I would put at least a couple of their probes into the NSA - they will then have access to intercepted comms on the global scale. I would get all of my probes to tap into the internet so that they could pass their data to those which are landed in a remote location (say in Africa) where there is no risk at all that their transmissions can be detected. The probes can scavenge the power from the local grids, which will minimise the need for onboard generation.

 

This tap would be VERY noticeable. You're also making the "independence day" mistake and assuming alien computers would be in any way compatible with terrestrial computers. Which is nonsense.

 

Now, if it were me, I'd keep it strictly off the grid and get the information delivered by subverted locals. Like, you know, the NSA. Why bother tapping the NSA and getting caught when you can just have the NSA do the work for you? The trade would be HEAVILY in the alien's favour if they did, and there's much less risk. The government would ever cover up your mistakes (and gladly).

 

I would also put some cloaked transponders in orbit right next to some defunct parked com satellites. They will never be spotted there and it will cut the required transmission power for the land based primary probes.

 

"Cloaking" is nonsense. You can't stop infrared emissions through your hull.

 

Sounds like good fun. We can write a whole SciFi novel like that

 

Funny you should mention SciFi. I happen to be a writer of both science fiction and fantasy myself. Haven't written anything lately, though. I have a LOT of projects going on, like working on making a tabletop game with my friend.

 

P.S. I have really taken your criticism of my laser heat dissipation idea to heart. You say it doesn't work like that - can you explain why do you think so?

 

P.P.S. Actually, it is not my idea at all. The first I read about it, I think, was in David Brin's "Sundiver"

 

Convection.

 

Heat itself is not infrared radiation and does not transmit solely through infrared. The heat in the ship will transmit directly to the material around it, then through it to other material, and then eventually out to the hull where it will *then* radiate off through infrared. There WILL be heat escaping through the hull. No amount of technological wizardry will change that. This is not something that can be changed.

[Vapymid]

It is SO much more likely that at least *some* people know they're here.

 

People are crap at keeping secrets. If anyone knew - that would probably be open secret by now. But what do I know? With enough incentive and the right amount of threat a *very small* number of people could probably keep their mouths shut...

 

part of our missile defence net, which picks up a rocket launch within minutes from across the planet.

 

But those look down, not up.

 

Alien spaceships would stand NO CHANCE of evading detection by our missile net.

 

I won't be so sure. If a GA plane could be flown across the Soviet border at the height of the Cold War and landed in the middle of the Red Square in broad daylight, anything is possible. And we are not even at war with the aliens.

 

Everything breaks down on Earth if given time.

 

The question is how much time. A device that would work for 5 - 10 years without any maintenance can be made easily even by us. That should be long enough, as it will probably become obsolete and will have to be replaced anyway to keep up with the changing technology of the targets.

 

which only makes you invisible until you've passed an observer and likely VERY visible once you have.

 

Only if somebody's looking at the right time in the right direction.

 

You're also making the "independence day" mistake and assuming alien computers would be in any way compatible with terrestrial computers.

 

With aliens being more technologically advanced it would be easy for them to build an interface for our systems, unlike us for theirs.

 

Why bother tapping the NSA and getting caught when you can just have the NSA do the work for you?

 

Depends on the alien spooks' brief...

 

"Cloaking" is nonsense.

 

No, it isn't. Cloaking can hide you from active search and from being exposed by back-light. Various cloaking concepts, protecting from various wavelengths, have been already demonstrated. No reason for aliens to not be able to develop practical applications.

 

The heat in the ship will transmit directly to the material around it, then through it to other material, and then eventually out to the hull where it will *then* radiate off through infrared.

 

Of course. What you'd want to do is to divert enough of your IR in the desired direction so that the remaining flux will be inconspicuous to a potential observer.

 

Regards

 

P.S. I will be "off-grid" for the next few days, so it may take me some time to resume this conversation. Thanks, it's been my pleasure

[BTGBullseye]

I would also put some cloaked transponders in orbit right next to some defunct parked com satellites. They will never be spotted there and it will cut the required transmission power for the land based primary probes.

 

"Cloaking" is nonsense. You can't stop infrared emissions through your hull.

 

P.S. I have really taken your criticism of my laser heat dissipation idea to heart. You say it doesn't work like that - can you explain why do you think so?

 

P.P.S. Actually, it is not my idea at all. The first I read about it, I think, was in David Brin's "Sundiver"

 

Convection.

 

Heat itself is not infrared radiation and does not transmit solely through infrared. The heat in the ship will transmit directly to the material around it, then through it to other material, and then eventually out to the hull where it will *then* radiate off through infrared. There WILL be heat escaping through the hull. No amount of technological wizardry will change that. This is not something that can be changed.

https://en.wikipedia.org/wiki/Thermoelectric_cooling

 

Plate the hull with them, and run cooling tubes around the inside... You can direct the thermal energy anywhere you want it to go. (and can even be used to generate electricity when it's not cooling)

 

An *accelerating* spaceship produces a MASSIVE amount of heat that no amount of technological advancement could ever conceal. Human activity doesn't. And it's in the atmosphere. You need to be a LOT closer to observe human activity than you do to pick up a hot trail of rocket exhaust.

https://en.wikipedia.org/wiki/Ion_thruster

 

Who says they have to use rockets, or can't use something that won't show up through the stellar wind?

 

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Also, unless the aliens are using organic or certain optical computers, (we already have interfacing systems for binary and trinary [quantum] computers, both optical and not) we can still interface normally. (who can say with certainty they developed their computer tech radically differently than ours, and have no way to build a basic interface like we do)

 

_____________________________________________________________________________________________

 

 

As for blooming, that is only for high-powered lasers that have constant output for long periods. It's easy to send a transmission with a low power laser or pulse laser into space, and not cause blooming. Even changing wavelengths can massively affect blooming from a laser. (using something similar to an x-ray or gamma ray laser, which would also theoretically increase the bandwidth considerably)