Ah yes, we’re speculating about a hypothetical advanced extraterrestrial species’ technology.
So we can say pretty much nothing about what kind of fuelling their probes require.
Whether they carry fuel, whether they can in some sense be fuelled remotely or whether they can obtain energy from chemicals they find on planets such as earth etc
I wouldn’t know, but I’d guess an advanced extraterrestrial species might – pretty much by definition – have some ideas about this, beyond our current understanding.
I’m not saying “Aliens are among us”. As I’ve said, I find such a thing extremely unlikely.
What I’m saying is, your objections are meaningless given the context of this hypothetical.
You do know that once a ship is in motion it stays in motion. The more interesting question is how it carries enough fuel to slow down to match the earth’s path in space.
Right. We are talking about aliens on Earth, not aliens who shoot by at the speed of light. Or some fraction of the speed of light that would make a ten light year trip feasible.
No. There are several ways to cross interstellar distance that are almost certainly possible; they’re just really hard, take a long time, and/or require technology we’re not close to yet, but which doesn’t violate any known laws of physics.
I hope you’re not positing that interstellar travel is simply impossible, forever, no matter how advanced a civilization’s technology.
Well, how about if as well as launching probes they also periodically fire capsules containing fuel towards a target planet, and the probes are smart enough to locate and use these capsules?
What I’m expecting you to respond with now, is some practical matter of how they could ensure the capsule landed nearby, withstood atmosphere entry etc.
And my point, two posts ago, is that such practical matters are of no significance at all when we’re hypothesizing an advanced race’s technology. The point is, it’s not defying the laws of physics as we know them.
You’re aware of course that maintaining a constant velocity requires no fuel, i.e, energy?
So the fuel required to travel to a planet 10 light years away is the same as the fuel required to travel to a planet 1,000 light years away: enough energy to escape the initial gravity well and accelerate to the desired velocity and then the energy required to land safely.
(being pedantic, travelling across outer space you will collide with some particles, and therefore require some energy for the journey, but it’s a negligable amount, even for 10 light years)
How did the LEM carry enough fuel to land on and then leave the moon? Maybe the probe could be accelerated, with a full load of fuel, by stages. Maybe it could collect hydrogen in space. Maybe it could be slowed, from a long way out, through solar sails. (It would take a long time, and quite an interesting set of orbits.)
People with balloon technology only are going to pooh-pooh going to the moon. A ten light year trip, given a lot of time for a probe, is not impossible. We’ve only had orbital capability for 50 years and haven’t given a crap for about 30 of them, so it’s not surprising we aren’t that far along.
Check out a book called “The Great Airship Mystery.” In the 1890s people all across the United States claimed to have seen a giant airship, and even talk to its pilot and inventor, who said he was from New England. Multiple witnesses were quite common. Of course, no such airship actually existed.
Read it, and you’ll see an almost perfect match to UFO sightings. It is a bit hard to believe that the airships weren’t real when you read the stories, but they weren’t.
It was really tough, and they only had to slow down from a few thousand miles an hour - not a large fraction of C. They left a lot of the LEM on the moon to make the takoff easier. In addition, the moon has 1/6 of the gravity of earth. Once they left the moon’s orbit they could “fall” back to earth.
I have seen a couple radical videos from pseudo-scientists that claim that since space/time is a fabric, it can be folded. So instead of actually travelling the distance between points A and B across a set distance in the Universe, you have technology that “folds the fabric” of spacetime in such a way that you bring points A and B together so the travel time is minimal.
Great idea for a book, anyway.
Or, we just need to figure out how to master wormholes. At least that’s what the prevailing theme in many sci-fi books leads us towards. And as we all know, if it was written in a sci-fi novel, invariably it will become reality in the future.
Given our very limited observational basis for planetary life (1), it appears from the fact that simple single-celled life appears to have developed on Earth as soon as it was cool enough that similar simple life forms are likely to develop on any planet with liquid water (or possibly liquid methane). Given the additional billions of years before any more complex life forms developed on Earth, it appears that the development of more complex life is not a given, and is dependant on favourable mutations occuring. Evolution provides no particular bias towards the eventual development or survival of intelligent life, despite our own species existence, and requires additional random mutation in order to develop.
If we assign a WAG chance of any given solar system currently having a suitable planet at 1/100, that planet currently having developed life at 1/2, that life currently having progressed to complex multi-celled forms at 1/1,000,000, that multi-celled life currently having developed an intelligent species at 1/1,000,000,000, and that intelligent species currently having an advanced technology civilization at 1/1,000, THEN we will expect there to be billions of other intelligent species in the universe, millions of them with advanced technologies. The chances of one of them even being in the same galaxy as us - pretty damned low. The chances of them being advanced enough and close enough to have reached us without some form of super-science light years-per-hour star drive, pretty much non-existant.
Won’t stop me from enjoying my science fiction books, but it’s enough to make UFOs as alien spacecraft NOT my default belief.
That’s what “warp drive” meant before Gene Roddenberry screwed it up. I think it may also have been what “hyperspace” referred to, back in the ancient days when most science-fiction writers were scientifically literate, but I’m not sure about that.
You’re missing the point, which is that they didn’t have to carry the infrastructure that got them off earth with them. I’d assume a probe would be one way, and so the fuel needed to decelerate could be accelerated by an unlimitedly large booster which would detach once the desired speed was reached. (Assuming the other techniques I mentioned weren’t used, which are kind of equivalent to atmospheric braking.) If a return trip were required, the probe might be able to refuel, since I’m sure the culture sending it out would know the composition of the gas giants in the target system. It would have to be caught on return, but they could dump the fuel tanks, so the energy requirements to slow it down would be reduced. I don’t really see why it would have to return in any case.