God, aliens and Nick Pope.

[Old Seer]

The evidence is the cosmos itself. There's far to much debris in interstellar travel to ever make to the next star. No spacecraft could travel for 20,000 years without encountering enough debris to destroy it. It can be safely assumed that no one from anywhere could make it here. It's like a person in Montana on a bicycle going grocery shopping in China while every now and then someone throws a rock at you. An acquaintance likens space travel as a ride on the great cosmic sanding belt.   

But surely they have deflector shields.

Not Likely. At 200,000 mph velocity in ft/sec, would be about 300000 ft/sec. An antitank non explosive penetration rod rounds velocity is 4800/3200 ft/sec and capable of destroying the vehicle. A 20 lb iron meteor strike would destroy anything to a point of damage loosing a lot, if not all, internal atmosphere, before repairs could be completed. Very likely more then one would be encountered along the route. The periodic table is all there is so that's all one has to work with.

[Asmodean]

That's also a bit of an issue with generation ships as a means of preserving the species. The probability of hull loss before ever reaching anything approaching a destination.

Of course, Sci-Fi has given us shields and kinetic barriers, but practically speaking, we are talking a ship's own magnetosphere of a suitable size and external atmosphere or armour plating sufficient to do the same job.

[The Magic Pudding..]

That's also a bit of an issue with generation ships as a means of preserving the species. The probability of hull loss before ever reaching anything approaching a destination.

Of course, Sci-Fi has given us shields and kinetic barriers, but practically speaking, we are talking a ship's own magnetosphere of a suitable size and external atmosphere or armour plating sufficient to do the same job.

Sci Fi has given us shields but it has given us the threats too.
Han Solo just barely navigating the asteroids, seems unlikely, how do all those big rocks remain big rocks in all the herly burly?

I don't think any of the probes that have been sent out have been destroyed by rocks, some have pretty much made it out of the solar system.

There's this business

In our solar system, the planets, asteroids, comets, and meteoroids all orbit the sun in a thin disk called the Invariable Plane.

Send out ten ships avoiding the obvious thin disky bits and loose one or nine, a thousand and lose 999 or none? I don't know.

I've been watching the Star Trek movies though and I have issue.  All weapons have failed so we'll ram them, why does that work, is it like Dune's slow blade penetrating the shield, I don't think so, I think the writers have some sort of trireme/bireme fetish

[Asmodean]

Han Solo just barely navigating the asteroids, seems unlikely, how do all those big rocks remain big rocks in all the herly burly?

They do, and they do not. Two objects, mutually attracted by gravity and moving in roughly the same direction at roughly-similar speeds may connect and stick together. Enough such connections, and the gravity of the nacent planetoid becomes enough that minor collisions do not send the whole thing flying apart. If it gets smacked by something bigger at a different sort of angle, however... Yeah. Big rocks turning into tiny rocks, full of sharp edges and murderous intent.

Both situations do occur. Still, space is... Well, a lot of space - most of it empty, even within a planetary system. I suppose "real life" asteroid hopping would be at far higher speeds over far greater distances. If being tracked into an asteroid belt, I see no immediate non-movie-script related reasons why it would be more difficult to continue tracking you within it - largely because how far apart them rocks actually are.

I imagine the "sandpaper" effect from cosmic dust and a occasional slug from gravel-sized meteoroids would be a far greater long-term danger than stuff you can "readily" detect in time to manoeuver around.

The probes we currently send out are, by interstellar standards, excruciatingly slow and satellites do get an occasional huwhack from space debris - both of natural and man-made variety.

[Old Seer]

May be something of interest.

https://www.youtube.com/shorts/gq77HquPJpo?feature=share

[zorkan]

Not Likely. At 200,000 mph velocity in ft/sec, would be about 300000 ft/sec. An antitank non explosive penetration rod rounds velocity is 4800/3200 ft/sec and capable of destroying the vehicle. A 20 lb iron meteor strike would destroy anything to a point of damage loosing a lot, if not all, internal atmosphere, before repairs could be completed. Very likely more then one would be encountered along the route. The periodic table is all there is so that's all one has to work with.

Oumuamua could have started as highly advanced alien tech, but just look at it now.
https://www.sci.news/astronomy/extraterrestrial-oumuamua-09261.html

[Old Seer]

Not Likely. At 200,000 mph velocity in ft/sec, would be about 300000 ft/sec. An antitank non explosive penetration rod rounds velocity is 4800/3200 ft/sec and capable of destroying the vehicle. A 20 lb iron meteor strike would destroy anything to a point of damage loosing a lot, if not all, internal atmosphere, before repairs could be completed. Very likely more then one would be encountered along the route. The periodic table is all there is so that's all one has to work with.

Oumuamua could have started as highly advanced alien tech, but just look at it now.
https://www.sci.news/astronomy/extraterrestrial-oumuamua-09261.html

If that's an actual  pic it's just a big rock.

[zorkan]

But everything looks like a rock to us out there in space.
If you could have showed a smart phone to a caveman, he would only recognise it as a rock.
Only a century ago we understood the Moon, Mars, Venus etc. to be only rocks.
Go back to the distant past the stars were only pinholes in heaven.
Unless there are laws of physics we don't yet know, Oumuamua might be an alien probe.
If it is the argument that aliens don't exist because we would have detected their probes is false.

[Asmodean]

But everything looks like a rock to us out there in space.

Not even a little bit. Clouds of gas look like clouds. Stars look like balls of plasma when magnified, dots of light when not. The Moon looks like cheese, apparently.

If you could have showed a smart phone to a caveman, he would only recognise it as a rock.

Untrue. He may be ignorant of its purpose, but any caveman worth his obsidian knife making sklills would recognise it as a shaped tool. (Herein, jewelry and decorative items)

Only a century ago we understood the Moon, Mars, Venus etc. to be only rocks.

Venice has been known to have a atmosphere for probably 2-300 years. It was also not uncommon in the period to which you refer to think of the neighbouring planets as well as the Moon, to a degree, as somewhat Earth-like, having rivers, forests, aliens... such-like.

Go back to the distant past the stars were only pinholes in heaven.

Still are to the naked eye.

If it is the argument that aliens don't exist because we would have detected their probes is false.

As presented, it is not a serious argument. There are far more compelling ideas for why aliens, whether or not they exist, have not visited Earth at least in written history.

[Old Seer]

But everything looks like a rock to us out there in space.
If you could have showed a smart phone to a caveman, he would only recognise it as a rock.
Only a century ago we understood the Moon, Mars, Venus etc. to be only rocks.
Go back to the distant past the stars were only pinholes in heaven.
Unless there are laws of physics we don't yet know, Oumuamua might be an alien probe.
If it is the argument that aliens don't exist because we would have detected their probes is false.

Biological Life at other places in the universe is possible and very likely is. The problem at hand is travel between stars.

[zorkan]

Venice has been known to have a atmosphere for probably 2-300 years.

That's because fog is whipped up by the lagoon to provide a romantic atmosphere at certain times of the year.

[Asmodean]

Venice has been known to have a atmosphere for probably 2-300 years.

That's because fog is whipped up by the lagoon to provide a romantic atmosphere at certain times of the year.

Yep. Walked into that one. Thanks, autocomplete.