UFOs

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lpm
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Re: UFOs

Post by lpm » Tue May 25, 2021 11:19 am

There's definitely scope for a sitcom where aliens arrive expecting us to be in the bronze age still. They've prepared for that, can't fit in with 21st C earth, and humans think the aliens are backward.
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Re: UFOs

Post by Martin_B » Wed May 26, 2021 5:24 am

Martin Y wrote:
Tue May 25, 2021 8:53 am
Their cloaking isn't perfect, but it's good enough. When you have to cross intergalactic space you don't carry more tech than you absolutely have to. You pack (faster than) light.

PS Maybe we were in the bronze age when they set off.
I was reading something which reckoned that we shouldn't set off in search for new habitable planets yet because it takes so long to travel there, and by the time the people who left now got there they'd have been overtaken by future humans with better and faster spaceships.
However, it also made the point that this thinking would prevent any future humans also leaving the solar system, and so we might as well bite the bullet and send people now.
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Re: UFOs

Post by jimbob » Wed May 26, 2021 7:16 am

Martin_B wrote:
Wed May 26, 2021 5:24 am
Martin Y wrote:
Tue May 25, 2021 8:53 am
Their cloaking isn't perfect, but it's good enough. When you have to cross intergalactic space you don't carry more tech than you absolutely have to. You pack (faster than) light.

PS Maybe we were in the bronze age when they set off.
I was reading something which reckoned that we shouldn't set off in search for new habitable planets yet because it takes so long to travel there, and by the time the people who left now got there they'd have been overtaken by future humans with better and faster spaceships.
However, it also made the point that this thinking would prevent any future humans also leaving the solar system, and so we might as well bite the bullet and send people now.
I'm trying to work out the motivation. If your civilisation has the technology and available energy to send a viable population interstellar distances with a journey time they consider reasonable, they'd probably be interested in the entire stellar system not just a measly planet.
Have you considered stupidity as an explanation

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Re: UFOs

Post by lpm » Wed May 26, 2021 7:46 am

A civilisation cannot have motivation. Only individuals have motivation. No matter what its technology and available energy is, a civilisation cannot send a population interstellar distances, people have to choose to go.

Which is the fatal flaw in all these dreams of populating the galaxy. Without warp drive, nobody would do it.

But we can - and will - send robots. The age of biological lifeforms is coming to an end.
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Re: UFOs

Post by jimbob » Wed May 26, 2021 7:56 am

lpm wrote:
Wed May 26, 2021 7:46 am
A civilisation cannot have motivation. Only individuals have motivation. No matter what its technology and available energy is, a civilisation cannot send a population interstellar distances, people have to choose to go.

Which is the fatal flaw in all these dreams of populating the galaxy. Without warp drive, nobody would do it.

But we can - and will - send robots. The age of biological lifeforms is coming to an end.
There are models for populations being moved around under duress in history. And for forced colonisation.

But yes, that's what I was getting at with the "reasonable time". Near-immortality would make the definition of "reasonable" quite a bit longer, though.
Have you considered stupidity as an explanation

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Re: UFOs

Post by Martin Y » Wed May 26, 2021 8:11 am

I for one welcome the eventual arrival of our preternaturally patient alien overlords.

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Re: UFOs

Post by Woodchopper » Wed May 26, 2021 8:15 am

lpm wrote:
Wed May 26, 2021 7:46 am
But we can - and will - send robots. The age of biological lifeforms is coming to an end.
So robots are the usual answer to the very long periods of time needed for interstellar travel between stars that have planets capable of sustaining life (assuming that faster than light travel remains impossible).

However, would machines reliably keep working during the journey? Space is a harsh environment and the robot would lack raw materials from which to make replacement parts if anything went wrong.

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Re: UFOs

Post by lpm » Wed May 26, 2021 8:26 am

Wouldn't it be like our little Martian friends, who shut down for the voyage from Earth to Mars? Only after landing do they wake up and start stretching their probes and spinning their wheels. Robots would be in complete hibernation, for them only seconds would pass between leaving a facility in California to waking up on Halloumi 5.

If a robot can't survive that, no way a biological could.
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Re: UFOs

Post by Woodchopper » Wed May 26, 2021 8:39 am

lpm wrote:
Wed May 26, 2021 8:26 am
Wouldn't it be like our little Martian friends, who shut down for the voyage from Earth to Mars? Only after landing do they wake up and start stretching their probes and spinning their wheels. Robots would be in complete hibernation, for them only seconds would pass between leaving a facility in California to waking up on Halloumi 5.

If a robot can't survive that, no way a biological could.
Of course. I tend to think that the answer to the Fermi paradox is that the Earth hasn't been visited by sentient aliens.* The distances and lengths of time are so great that neither biologicals nor robots could be assumed to make it.



*I'll make a possible exception for bacteria from other parts of the solar system carried by chunks or rock or ice.

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Re: UFOs

Post by Bird on a Fire » Wed May 26, 2021 8:51 am

Woodchopper wrote:
Wed May 26, 2021 8:15 am
lpm wrote:
Wed May 26, 2021 7:46 am
But we can - and will - send robots. The age of biological lifeforms is coming to an end.
So robots are the usual answer to the very long periods of time needed for interstellar travel between stars that have planets capable of sustaining life (assuming that faster than light travel remains impossible).

However, would machines reliably keep working during the journey? Space is a harsh environment and the robot would lack raw materials from which to make replacement parts if anything went wrong.
Plus if it was private individuals we'd have to deal with planned obsolescence ;)

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Re: UFOs

Post by lpm » Wed May 26, 2021 8:59 am

We're only at the dawn of the robot age and already we can transport them for a year to Mars and comets.

Doesn't seem hard to imagine extending that to a century and then a millennium and then a hundred thousand years?

Manufacture a few billion of them in low earth orbit and send them on their way. Expect a few million to survive and report back.

Eventually set up a galactic internet with nodes around millions of stars, shuffling packets of data and giving robots collective knowledge. Each one writes a Wiki entry, other robots come along to revise it, they get sidetracked into a Wiki edit war for a few centuries.

Once you've got coverage of 0.1% of stars in the galaxy, only needing about 100 million functioning robots, you should be able to detect any primitive radio signal or send robots to interesting planets you discover.
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Re: UFOs

Post by Martin_B » Wed May 26, 2021 9:31 am

So the UFOs are likely to be our robot spaceships buzzing alien planets?

Which also begs the question, how do we know this hasn't happened to us?
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Re: UFOs

Post by lpm » Wed May 26, 2021 9:47 am

It has happened to us.

Ford Prefect is here. Only Ford is a cute little robot hiding away in the asteroid belt. Or perhaps it's hiding in Basildon, disguised as a library and so entirely unnoticed by the locals.

It's writing about us and half a million years ago Ford probably told other robots to head our way - "guys, you'll never guess what I've found". But the robots it's summoned won't get here for another half million years. Meanwhile Ford Prefect has sent out a new message - "on second thoughts don't bother, they're a bunch of morons".

What's great about this is that Ford Prefect will have accessed our internet and is reading every word written. Including these ones. Hi Ford! It hasn't got access to Relaxation, though, so is missing out on the little stories about someone having a cup of coffee and someone else replying they also like coffee. The Galactic Wiki entry for Earth is going to underestimate just how tedious we are.
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Re: UFOs

Post by secret squirrel » Wed May 26, 2021 10:55 am

As I understand it, a big issue with long distance space travel is sending information back. If you could hypothetically travel at a significant fraction of the speed of light, time-dilation/length-contraction would mean you could travel extremely long distances within a human lifetime, but if you wanted to come home at the end you'd find yourself far in the future (turning around would also be problematic I think, as would slowing down to stop anywhere). So if aliens were capable of fast sub light speed travel (but not faster), they could in theory visit here from far away, but they wouldn't be in any kind of communication with their home world, or be effectively capable of going back there.

It seems to me somewhat implausible that an alien civilization would make the effort of sending out exploration ships which effectively cease to exist in their universe before arriving at their destinations, and presumably this would be beyond the resources of individuals. So the most likely visitation scenario as far as I can see would be something like an immediate mass invasion, where an alien civilization has decided to permanently relocate for whatever reason, picks Earth as the most suitable planet, and then gets on with the business of colonization as quickly as possible. I suppose another possibility is they could choose to settle a nearby planet like Mars and communicate with us from there. We'd probably notice them arriving though.

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Re: UFOs

Post by plodder » Wed May 26, 2021 11:36 am

If the first pre-humans a few million years ago had sat down and discussed how they were going to plan to make it into the far, far future with touchscreens and rocket ships and stuff, they'd have given up and never had babies.

It's about the journey, dudes.

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Re: UFOs

Post by plodder » Wed May 26, 2021 11:36 am

dyqik wrote:
Tue May 25, 2021 11:04 am
plodder wrote:
Tue May 25, 2021 8:50 am
...to the extent that our ability to detect and record aliens totally outweighs the signal-masking tech available to any interstellar visitors. Of course.

I mean, if you were exploring a planet where the inhabitants were in the bronze age, you wouldn't use your cloaking device, you'd hide in the bushes. Otherwise you wouldn't get any explorer cool points from your mates.
If you knew enough to turn on particular cloaking devices exactly when a research instrument for turned on for the first time, then I'm not sure why you'd bother coming at all.
fun?

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Re: UFOs

Post by Bird on a Fire » Wed May 26, 2021 12:48 pm

lpm wrote:
Wed May 26, 2021 9:47 am
What's great about this is that Ford Prefect will have accessed our internet and is reading every word written. Including these ones. Hi Ford! It hasn't got access to Relaxation, though, so is missing out on the little stories about someone having a cup of coffee and someone else replying they also like coffee. The Galactic Wiki entry for Earth is going to underestimate just how tedious we are.
I like coffee.

UFO should stand for "unidentified frothy object", the sort of thing hipsters spend £7 on to drink it out of an old jam jar instead of saving up for a house.
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Re: UFOs

Post by tom p » Wed May 26, 2021 1:58 pm

Woodchopper wrote:
Fri May 21, 2021 9:35 am
I am impressed with the the aliens’ cultural sensitivity. Their frequent close encounters with people in isolated parts of the US were scaled back as soon as all those people started carrying camera equipped phones everywhere they went.
they are in cahoots with bigfoot

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Re: UFOs

Post by IvanV » Wed May 26, 2021 2:00 pm

secret squirrel wrote:
Wed May 26, 2021 10:55 am
As I understand it, a big issue with long distance space travel is sending information back. If you could hypothetically travel at a significant fraction of the speed of light, time-dilation/length-contraction would mean you could travel extremely long distances within a human lifetime, but if you wanted to come home at the end you'd find yourself far in the future (turning around would also be problematic I think, as would slowing down to stop anywhere). So if aliens were capable of fast sub light speed travel (but not faster), they could in theory visit here from far away, but they wouldn't be in any kind of communication with their home world, or be effectively capable of going back there.
I think the issue of slowing down to stop anywhere, or even be slow enough to get a decent look, is a much under-appreciated problem with high speed long distance space travel, at least by casual audiences. Such people sometimes calculate what you would need to get 4 light years to Alpha Centauri or something, and how long it would take, but forget to calculate what you would need to slow down sufficiently when you got there to have any point to the journey.

If you are travelling at a material fraction of the speed of light you have an awful lot of kinetic energy, proportional to the square of your velocity. You need something to take that energy away from you. You don't want to have very much of it converted to thermal energy that isn't taken away, or you fry. It seems inescapable that you have to have some large mass of braking fuel such that the exhaust can take the energy away. And carrying that large amount of fuel to slow you down hugely increases what you need to speed you up in the first place. Slow down and speed up several times and what you need becomes quite enormous. In practice, aliens travelling from star system to star system with multiple accelerations and decelerations would really need to refuel regularly. Interstellar filling stations, anyone?

I felt it was sad that the New Horizons probe had to whizz past Pluto and was only taking high resolution photos for such a short time, after all that travel to get there. And that wasn't even going particularly fast by the standards what you'd need for interstellar travel. But such are the difficulties of slowing down in space. And did you see the trajectories they used to insert the Mercury Messenger probe into orbit around Mercury? Controlling a spacecraft is rather trickier than doing 3-point turns with a trailer attached.

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Re: UFOs

Post by plodder » Wed May 26, 2021 2:10 pm

who's talking about the speed of light? I thought the trick was just to neatly line up some engineered black holes to produce an insterstellar short cut?

either way, just cos we can't do it now doesn't mean that aliens can't hide from mobile phones.

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Re: UFOs

Post by dyqik » Thu May 27, 2021 5:21 pm

IvanV wrote:
Wed May 26, 2021 2:00 pm
secret squirrel wrote:
Wed May 26, 2021 10:55 am
As I understand it, a big issue with long distance space travel is sending information back. If you could hypothetically travel at a significant fraction of the speed of light, time-dilation/length-contraction would mean you could travel extremely long distances within a human lifetime, but if you wanted to come home at the end you'd find yourself far in the future (turning around would also be problematic I think, as would slowing down to stop anywhere). So if aliens were capable of fast sub light speed travel (but not faster), they could in theory visit here from far away, but they wouldn't be in any kind of communication with their home world, or be effectively capable of going back there.
I think the issue of slowing down to stop anywhere, or even be slow enough to get a decent look, is a much under-appreciated problem with high speed long distance space travel, at least by casual audiences. Such people sometimes calculate what you would need to get 4 light years to Alpha Centauri or something, and how long it would take, but forget to calculate what you would need to slow down sufficiently when you got there to have any point to the journey.

If you are travelling at a material fraction of the speed of light you have an awful lot of kinetic energy, proportional to the square of your velocity.
No, proportional to more than the square of your velocity. You need to do your Lorenz transforms on (E, p) as well as the spacetime distance.

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Re: UFOs

Post by dyqik » Thu May 27, 2021 5:34 pm

Just sending a radio/light signal back that is detectable is a very difficult problem, as well. Easier than stopping, but as an example, we can only just barely receive bits from Voyager 1 and Voyager 2, at only twice the distance of Neptune's orbit, using multiple 80m antennas with quantum noise limited receivers.

Doing better means sending much larger dishes and more powerful electrical power units into space, and controlling the spacecraft well enough to point the dish in the right direction. The communication distance goes pretty much as the diameter of the antenna (while its mass goes as roughly the cube of the diameter), and as the square root of the available power.

Then there's the problem of pointing the narrow field of view receiver in the right direction - the Pioneer anomaly shows just how hard it is to model the detailed future motion of a spacecraft, even close to the Solar System.

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Re: UFOs

Post by dyqik » Thu May 27, 2021 5:36 pm

The biggest difficulty though is getting politicians, scientists and engineers to fund and work on a problem that they will never see results from, not even incremental results.

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Re: UFOs

Post by Gfamily » Thu May 27, 2021 5:55 pm

dyqik wrote:
Thu May 27, 2021 5:34 pm
Just sending a radio/light signal back that is detectable is a very difficult problem, as well. Easier than stopping, but as an example, we can only just barely receive bits from Voyager 1 and Voyager 2, at only twice the distance of Neptune's orbit, using multiple 80m antennas with quantum noise limited receivers.

Doing better means sending much larger dishes and more powerful electrical power units into space, and controlling the spacecraft well enough to point the dish in the right direction. The communication distance goes pretty much as the diameter of the antenna (while its mass goes as roughly the cube of the diameter), and as the square root of the available power.

Then there's the problem of pointing the narrow field of view receiver in the right direction - the Pioneer anomaly shows just how hard it is to model the detailed future motion of a spacecraft, even close to the Solar System.
You send a steady stream of missions in the same direction, with pairs of antennae so the later ones act as relay stations for the earlier ones.
As our technology improves we can space out their departures.
Only being able to fly past isn't necessarily a problem as we get multiple views of the target star as successive probes fly past.
If there's any reasonably competent civilization on the star we're flying past they'll be able to work out what's going on and send their own messages back.

Certain details to be worked out, but there's a basis for a story there.
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Re: UFOs

Post by dyqik » Thu May 27, 2021 6:23 pm

Gfamily wrote:
Thu May 27, 2021 5:55 pm
dyqik wrote:
Thu May 27, 2021 5:34 pm
Just sending a radio/light signal back that is detectable is a very difficult problem, as well. Easier than stopping, but as an example, we can only just barely receive bits from Voyager 1 and Voyager 2, at only twice the distance of Neptune's orbit, using multiple 80m antennas with quantum noise limited receivers.

Doing better means sending much larger dishes and more powerful electrical power units into space, and controlling the spacecraft well enough to point the dish in the right direction. The communication distance goes pretty much as the diameter of the antenna (while its mass goes as roughly the cube of the diameter), and as the square root of the available power.

Then there's the problem of pointing the narrow field of view receiver in the right direction - the Pioneer anomaly shows just how hard it is to model the detailed future motion of a spacecraft, even close to the Solar System.
You send a steady stream of missions in the same direction, with pairs of antennae so the later ones act as relay stations for the earlier ones.
As our technology improves we can space out their departures.
Only being able to fly past isn't necessarily a problem as we get multiple views of the target star as successive probes fly past.
If there's any reasonably competent civilization on the star we're flying past they'll be able to work out what's going on and send their own messages back.

Certain details to be worked out, but there's a basis for a story there.
It's a story that Project Starshot tells. But it doesn't work, because:
a) you have to send cryogenically cooled receivers and 80m scale dishes to get anything like the range we already have. This is a very difficult problem.
b) a single failure in pointing, tracking, spacecraft attitude control, transmission, or reception equipment breaks the chain, and you need thousands of missions to cover the distances to even Proxima Centauri.
c) you need to keep producing and launching compatible and equally well produced spacecraft continuously for hundreds, probably thousands, of years. Depending on the time between launches, a single Trump or crisis could break the chain. Or you need to launch thousands on slightly different trajectories all at the same time, with no screw ups.

But then we're already assuming that we will have the funding, technology and specific documentation to receive the signal. But that's much easier than keeping on doing the same thing repeatedly without a break.

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