I think you mean powered flight…the first balloon flights were in the late 1700’s (or you mean the late 18th century).
I don’t know of anything that specifically makes anti-gravity impossible (I seem to recall that every ‘force’ has an opposite, so it’s not beyond the realm of possibility that there is a anti-gravity force, and in fact there is some sort of repellant force at work out there pushing galaxies away from each other). We might never be able to tap into it, but I can’t think of anything that makes it theoretically impossible.
UFO sightings were huge here in Israel back in the mid-90’s; I remember reading about a new one every week or so. The trend ran its course, and by 2000 or so people went back to being scared of more… earthly threats.
Well, they could be coming from counter-earth or from inside the hollow earth. Both of those possibilities would also require radical changes to our understanding of physics as well, of course.
Really? Can you cite physics professors or researchers suggesting that manned flight was theoretically impossible?
My understanding is that movement without inertia violates one of our most basic ideas of physics, i.e., that a body in motion tends to remain in motion. It may be possible, but we’d need to revise physics from the ground up in order to understand it.
Manned flight required no such rejiggering of our basic precepts of physics, but rather required some excellent engineering.
An earlier thread on the subject. It appears there’s some doubt that Kelvin actually said flat-out that heavier-than-air flight could never happen; rather he seemed to be saying that the engineering hurdles were too great for it to ever be practical.
That’s still totally wrong, of course, but it’s not like he was saying that basic physics prevented it, in the same way that basic physics prevents inertialess flight.
I assumed that meant “unknown to the public at large.” Most of these sort of stories include the idea that the government knows a lot more about the aliens than the rest of us - often to the extent of actively working with (or even being controlled by) the aliens.
UFOs before WW II were not saucer-shaped, but dirigible shaped. Charles Fort has many examples of these. This argues for FTL travel - they brought in the new model year.
Aliens are so impressed by human entertainment that they take on the form of aliens shown in TV and movies - since many of them happen to look like aliens from popular culture.
BTW, given how little we know about gravity, saying anti-gravity is impossible is a bit presumptuous. Impossible under current theories, sure, but we had better understand dark energy a bit more first.
Firstly, physics as we know it would be wrong, given the FTL travel alone.
Secondly, biology as we know it would be wrong, given the ease with which aliens are shown to hybridize with us.
Lastly, human nature as we know it would be wrong, because there’s no way any big government can organize a cover-up of that magnitude.
Depends on propulsion systems.
If we can come up with some sort of a constant-boost engine, the stars are fairly close.
For the thrust-and-drift model, say three generations to get there, the grandchildren of the initial voyagers arrive at the planet.
You’d need a pretty big population, for lots of reasons.
5,000 to 10,000 is plausible. And genetic material, eggs and sperm, from others on Earth.
When you get to a new star system, it takes a while to prepare a colony.
Getting from orbit to land and establishing a viable base could take 20-30 years, so you encourage extra births during that time. Part of the crew complement goes to the planet, part stays on board the ship- then sets sail for the next destination when the time comes.
Think of settling Polynesia on rafts.
This would be more effective and less risky than that.
Sorry I’m replying to myself- I tried to edit the above post, guess I waited too long.
@Trinopus: Yes, quite expensive, but you could spread the cost of several decades.
As for size, not all that huge. Something the size of a dozen aircraft carriers would be adequate.
Might be cheaper to mine lunar regolith vs boosting from Earth to LEO assembly point.
@Czarcasm: I’d point the thing at Capella, the nearest star that is most like our, a G2 at 11 light years.
I think there are lots of planets everywhere. If not, just keep sailing until you find a good one.
But the thread is about others coming here- pointing their generation ships at Sol.
Gotta admit, it’s a sweet little star.
I think you might have been replying to me, not Czarcasm.
I’ve got an envelope in front of me, on the back of which I’ve done a few calculations. A few facts (they may or may not be fun):
Voyager 1 was launched in 1977, and is presently the farthest man-made object from Earth. In 36 years it has traveled 124.34 AU (at 93,000,000 miles per AU, that’s 11.56 billion miles). One light-year is roughly 5.87 trillion miles.
Speaking algebraically, that means it would take roughly 507 Voyager 1 trips of thirty-six years each to make it one light-year. So about 18,261 years to reach the one light-year milestone. And 200,872 years to make it out to eleven.
Just out of curiosity, how does that work with a non-FTL ship making it in three generations?
We’re assuming a fusion-powered drive, not a chemical rocket.
It’s beyond today’s technology, but not by much. We know fusion works, the evidence is right there.
The biggest problem really is engineering a closed-loop environment.
And we need some advances in materials handling and manufacturing.
Nothing out of reach, just not yet available. Nanotechnology could be super helpful if we get it in time.
The ship will be in touch by communications laser, too.
so if there are advances in technology, that information can be transmitted to them.
Edit- and again, we’re talking about aliens.
Something like a solar sail might be a perfectly feasible choice for an alien psychology.
For humans, I think a journey of 50-100 years between stops is about the max.
