The two Voyagers weren’t even designed to be the fastest space probes we could build with current technology. Their speed was entirely dictated by the trajectories they had to follow in order to do their planetary flybys. The New Horizons mission to Pluto was a compromise between how long we’d wait for it to get there versus how long it would remain in Pluto’s vicinity. So to use Voyager’s sluggish pace as an indicator of how difficult interstellar flight would be is misleading.
@Mijin, you’ve emphasized that we’ve gone from sharpening rocks to interplanetary travel in thousands of years. I say that we’re no closer to interstellar travel than we were when an atlatl was the height of technology. Going from star to star is one hell of a different beast than shuffling around our little cosmic neighborhood.
I’m also struck by the obsession with asteroids in this thread. Is it because they’re In Space? For some perspective, the asteroid belt has three percent the mass of the moon. Three percent! Of the moon!
- Suggesting that we are no closer is absurd; we’ve sent probes out of our star system (depending on how we define it…they’re simultaneously considered in the oort cloud and in interstellar space. But anyway eventually they’ll be fully out). You can choose to scoff at that progress if you like, but it very obviously is progress.
- You’re missing the point: that all of human history is mere thousands of years and so the technological progress of millions or even hundreds of millions of years is orders of magnitude beyond unfathomable and engineering challenges just don’t cut it. It may be the case that species dont make it to that level of progress, or certain physics challenges are simply impossible to achieve. But that’s the level of claim we need to be making in the context of the fermi paradox.
- The reason people bring up asteroids is because of the concept of the self replicating probe: a probe that could find, extract and assimilate materials from asteroids, and use it to make more probes. In this context it is relevant that we’ve achieved some of the first steps towards this i.e. reaching and safely landing on an asteroid.
None of our probes is anywhere near the Oort Cloud, which is unambigiously in interstellar space. Voyager 1 will be there in about 300 years and take 30,000 years to get through it. Chemical rockets will not get us to the stars. Throwing a rock into the sea isn’t seafaring.
As for the asteroids, why asteroids? Why not planets?
If you’re just seeking naterials to make a self replicating probe, the smallest body with the weakest gravity well that has your entire shopping list is your friend.
On a planet, all the jillions of tons of mass deeper than a few dozen feet beneath the surface is simply an obstacle to your mission, not great bounty to be exploited.
So you’re talking iron, probably? There are asteroids that are very iron-rich, like mostly iron. What else might be easily available on an asteroid but not on the surface or within several dozen feet thereof on a rocky planet?
The rocky planet comes with a gigantic actively harmful gravity well that makes everything about your arrival and departure(s) vastly more difficult for zero benefit.
Atmospheres only make it doubly difficult.
It’s a total noob mistake to want to visit or even inhabit planets when suitable asteroids are also available.
Okay, so stated more generally, among bodies that offer the same resources, the body with least surface gravity is best?
This is probably correct. If we ever get to another planetary system, we had better be competent at exploiting asteroids, moons and other small objects rather than expecting to find suitable planets for colonisation. Planets are difficult to land on, and even more difficult to launch from. Asteroids and comets are made from the same materials as planets, but are easier to access.
By the time we are ready to leave our own system (maybe a thousand years from now) we will have plenty of practice exploiting asteroid resources; if we do not have this practical experience, we may as well not bother going at all.
If a civilization has the capacity to travel between stars, surely it can handle landing and launching from a planet. Hell, we can do that now.
Ok I misspoke about the oort cloud, but are you going to respond to my points?
I didn’t claim that what we have today is already interstellar travel, I was responding to your claim that since the stone age, we are “no closer” to interstellar travel.
Despite the fixation of science fiction on shirtsleeve climate oxygen atmosphere planets, a planet with its own life would most likely be a level-4 biohazard zone. It would probably require humans genetically engineered to live there. Interstellar colonists would probably prefer to terraform lifeless planets.
Why bother then? Because unless by that time we have the ability to construct really huge artificial habitats, a habitable planet could offer a far larger ecosystem, with more diversity and more passive stability. With carbon nanotubes, the strongest material we can confidently expect to exist, the largest spin-gravity cylinder possible might have about 5 million square miles living space. That sounds like a lot but the surface of the Earth is over 196 million square miles.
Asteroids are generally extremely rich in all kinds of useful and precious metals. They are made of the same stuff as the planets, but with planets virtually all of it sinks to the core where it’s out of reach. Medium-sized asteroids can contain more precious metals than we’ve ever mined.
(before anyone jumps in: yes I know this does not make asteroid mining anywhere near viable today)
“Extremely” is a matter of perspective. A handful of random undifferentiated asteroid regolith is going to have a higher ppm of, for example, gold than a handful of random Earth gravel, but it is still going to gave a much, much lower ppm of gold than a mined gold ore on Earth. You could mine gold on Earth by taking billions of tons of random rock and sorting through every atom for the gold, but it would be hugely expensive. That is exactly what you would have to do to mine it from an asteroid. There might be a higher ppm of gold, but you have the extra complications of trying to do it in space.
Citing a post by myself:
For many of the elements that are rare on Earth’s surface, those geological processes that concentrated them concentrated them down to the Earth’s core. In a differentiated asteroid, those same elements would be concentrated into the asteroid’s core. Luckily, most of the asteroids large enough to have differentiated into a core and mantle/crust have been blasted to bits and those pieces of core are floating around naked.
According to this chart the average concentration of gold in the Earth’s crust is 0.0031ppm. According to this PDF, the concentration of gold in meteorites varies, but certain iron meteorites (called “siderites” in the old study) contain up to 10ppm gold. In undifferentiated meteorites, the gold percentage is still much higher than the average for Earth’s depleted crust, with chondrites having from .1 to .37ppm. According to this page, the highest grade gold mines are at around 1 to 3ppm gold.
So asteroids range from “lower concentration than a rich mine but higher than a random handful of Earth’s crust” for stony meteorites to “similar to or greater than the gold concentration for the highest-yield mines” for iron asteroids. Plus other precious metals. Whether or not it would be possible in the short or long term to mine asteroids is questionable, but there is gold in them there floating hills.
At the rate of 1 ppm, you would need to sift through every atom of more than 30 tons of asteroid material to collect 1 ounce of gold.
No current technology can take travelers to another star system. Any potential interstellar travel tech is just that, potential. We haven’t built it. So far it’s all conceptual. As it was 30,000 years ago.
The Voyager probes launched in the 1970s are interstellar travel tech that is actually in use.
Sure, but are people going to travel to another star on it? Like I said upthread, that’s like throwing a rock into the cosmic seas.
Of course, but I was responding to the argument “What else might be easily available on an asteroid but not on the surface or within several dozen feet thereof on a rocky planet?” – the answer of course being “lots of useful materials”.
But the point is not that an asteroid is a gold mine but that it’s a gold mine and a iridium mine and a platinum mine or whatever else. And, for some asteroids, vastly bigger than all such mines combined on earth.
Did you think that was the claim I was making?
That humans are about to fly to alpha cen…we’ve got the engine running, we’re just grabbing snacks for the long journey to alpha centauri?
Why don’t you just say you misspoke? I said that upthread. I thought one of the voyagers had reached the oort cloud, it wasn’t correct, so I took it back.
Why can’t you just acknowledge that building, launching and steering probes on a trajectory out of our star system is very obviously progress towards interstellar travel. It doesn’t mean you can’t be skeptical about whether we, or anyone, could solve the remaining challenges.
Earth is a richly differentiated source of various resources, and has a nice oxygen atmosphere to exploit as well. But we can’t rely on finding an Earth-like planet in every planetary system - indeed, after discovering upwards of 6000 exoplanets so far, the number of worlds that resemble Earth is no more than a handful of largely unsuitable ‘Earth Clones’ that would be tricky to colonise and exploit.
Not easy to mine a terrestrial planet if it is covered in hundreds of kilometres of water and/or wrapped in a dense unbreathable atmosphere, and so on. To expand throughout the universe, humanity (or our successors) will need to be skilled in obtaining resources from space, and that means asteroids, Oort cloud objects, moons, and small low-gravity planets.