Even the space race wasn't for science but for politically one-upping the others, doubly so because being able to bring a payload into space also demonstrates they can bring a payload anywhere on the world.
Also note that "solar sail" is a bit misleading, the (now apparently dead) Breakthrough Starshot design was a big reflector "sail" in space and very many lasers on Earth to power it, it's not actually driven by a stellar wind directly.
"...or by ejecting a reflector that is then used as a braking system (similar to thrust reversal on jets) but this only works if the payload is still within illumination range of the primary laser system"
This is actually I "love" to think about:
What would it be like, to be "stranded" in the space far from any stars?
or in the "voids" where there are relatively very few stars/galaxies to begin with?
There must be things drifting there right now...
It would also be the perfect place to HIDE something :)
Note that the “naked eye” stars we see in our night sky are all big, bright stars in our immediate vicinity.
Outside of a galaxy the night sky would be black, other than some fuzzy smudges of other galaxies.
It would be a long time before any such species would figure out what galaxies are, what stars are, and their own relationship to those things.
Their study of astronomy would take a wildly different path even assuming they end up at the same conclusions!
And then what? What missions could they envisage, tens of thousands of light years away from the next nearest… anything?
One thing that is clear is that the intergalactic medium has a highly variable density. In the vicinity of a recent galactic merger or near-miss, there would be a smear of stars fading off into the distance.
Conversely, even a fairly quiet and passive galaxy like our own is expected to eject stars at a rate of one every few hundred years from the core region immediately nearby the black hole there.
Even better, (or worse): A species that evolved on a rogue planet! Without any star!! (heated by it's core or nuclear elements or space magic or whatever)
> It would be a long time before any such species would figure out what galaxies are, what stars are, and their own relationship to those things.
Humans are bad enough with our "We're unique and special!" complex, imagine theirs!! lol
Getting hit by some random molecule when orbiting Earth or just travelling say 30,000 kmh is one thing. Getting hit by swarms of molecules with say 0.5c can be catastrophic to the material. Now imagine wading through some space dust cloud, or even plasma cloud (ie remnant of some bygone supernova).
Star trek had shields, and for good reasons. Super strong magnetic field may divert some charged particle, but helium molecule is just a helium molecule, no extra charge to play with.
Does anyone have an idea how to equip a 1g spacecraft with any means to steer itself at 1/3 speed of light? The kinetic energy at that speed would seem to require something very incompatible with the weight constraint, to my understanding.
> The most challenging phase of the mission may be related to how the nanocraft can transfer from an unbound to a bound orbit and start orbiting around the compact object. All possible solutions should be considered carefully. In the case the transfer is not possible, we may redesign the mission to perform the scientific tests when the nanocraft passes close to the black hole. For example, when the nanocraft is close to the black hole, it may separate into a mother-nanocraft (with a wafer and sail) and a number of small nanocrafts (without sails). The nanocrafts could communicate with each other by exchanging electromagnetic signals. The mother-nanocraft could compare the trajectories of the small nanocrafts to those expected in a Kerr spacetime and send the data to Earth.
Light sales can theoretically be used to not only accelerate away from Earth, but also decelerate at the end of an interstellar journey (see Robert L Forward's work). The practicality of that is another matter.
More seriously, it floors me how often and consistently people forget that the accretion disk is essentially a partial accelerator and crossing or entering it will probably pulverize you to radioactive dust. Possibly before you could hit the event horizon.
And how do you get into orbit?
Yes. Yes it most certainly is. Whatever we learn will be new.
I was a bit confused by your comment, but I think the article you're referring to is not the OP, but the article the OP was commenting on: https://www.cell.com/iscience/fulltext/S2589-0042(25)01403-8...
> Does anyone have an idea how to equip a 1g spacecraft with any means to steer itself at 1/3 speed of light? The kinetic energy at that speed would seem to require something very incompatible with the weight constraint, to my understanding.
I'm also wondering how such a thing is supposed to communicate back to us over dozens of light years. That also seems incompatible with the weight constraint.
Split particle pairs. We just need to repeal the no cloning theorem, maybe if we promise to not use it for FTL communication the legislators would go for it.
Just spit-balling here. Send out the first batch of probes and then 5 years later send another batch of probes. The first batch of probes does their surveying for 5 years, when the later batch of probes start arriving. The data is uploaded to the late-comers, who aren't on an intercept course. Instead they are on a trajectory that causes them to swing around the black hole, and head on back to earth with the data.
What's the separation there, at 0.33 lightspeed? 1.65 light years? Wikipedia says Voyager is 168.35 AU away, and Google says that's 0.00266 light years. Voyager has 23-watt radio focused by a 3.7m dish and its signals are received by a 70-meter dish on Earth.
So you're talking about a 1g spacecraft signaling another 1g spacecraft over 620 times the distance to Voyager, without any of the beefy equipment that exists on both ends of the Voyager link.
Also, the probes are in deep space, right? No solar power. Where are they going to get the energy?
Not like a 1 gram probe is going to be expensive compared to the launch system.
https://en.wikipedia.org/wiki/Gravity_assist
also:
Roundtrip Interstellar Travel Using Laser-Pushed Lightsails
https://ia800108.us.archive.org/view_archive.php?archive=/24...
Notably, this also has a particularly bad ISP?
Also, probes are presumably also heavier and rarer?
The 'spring action' of fuel is very good because there's a lot more energy (per unit mass) stored in the bonds. Orders of magnitude more than a mechanical spring.
Specific impulse.
Please read.
Reaction wheels are used to make adjustments to orientation. See https://en.wikipedia.org/wiki/Reaction_wheel
Thrusters of all sorts can also be used, generally to maintain altitude in satellites, and more generally to provide thrust for space probes.
Idk, i think the fact they are using statistical arguments that there should be a nearby black hole, but haven't actually found any or have any idea where they are, is pretty blocking.
A change in direction in space requires accelerating the vehicle in some direction, the effect of which is just simple vector addition of the velocity vector of the vehicle.
So if you are going with a huge velocity in one direction and you want to change direction significantly in another direction you have to change velocity (accelerate) a lot in order for the combined vectors to produce a significantly different final velocity vector
Won't happen under this administration and really might take a planet-wide effort but it would be incredible
https://www.centauri-dreams.org/2022/07/22/solar-gravitation...
https://www.nasa.gov/general/direct-multipixel-imaging-and-s...
https://www.universetoday.com/articles/a-mission-to-reach-th...
Not in my lifetime I suspect...
api•3mo ago
It would be super hard to detect though. We’d have to spot it by gravitational effects or get very lucky and notice lensing. It would emit nothing unless it happened to be nomming on some matter, and even then it’d be so small that the signal would be weak.
noam_k•3mo ago
I read somewhere that a black hole with the mass of the moon will absorb about as much cosmic radiation as it emits Hawking radiation. This is a fine line between "the black hole disappears before we can examine it" and "oops, we got eaten by a black hole".
MomsAVoxell•3mo ago
gus_massa•3mo ago
MomsAVoxell•3mo ago
api•3mo ago
I've actually posted this a few times:
If you suddenly transformed the Moon into a black hole of the same mass, it would continue to orbit the Earth in the same spot. It wouldn't suck up the Earth or anything. The ocean tides would continue as normal under the influence of the black-hole-moon's gravity, which would be the same if it was orbiting at the same distance. You wouldn't see a moon in the sky, but if you focused a good telescope on where it was you'd see gravitational lensing. It would be a little smaller than a BB.
antonvs•3mo ago
What makes black holes special is that you can get much close to their center of mass than you can with normal objects. When you're that close - inside the radius that a normal density object of that mass would have - then you experience gravity at a much higher strength than normal.
Put another way, even if our Moon was a black hole with the same mass, very little would change except that it would no longer reflect sunlight. Ocean tides on Earth would remain the same. You wouldn't want to try to land on it though...
akomtu•3mo ago
api•3mo ago
throwaway290•3mo ago
antonvs•3mo ago
antonvs•3mo ago
A white dwarf smaller than the moon seems unlikely, if not impossible. If it were that small, unless it was in the (fast) process of collapsing to a neutron star, it wouldn't have enough mass to remain that compact.
A neutron star or black hole would work fine, because both can easily have radii much smaller than the Moon's.
Here's an article about that - https://www.fandom.com/articles/moonfall-real-life-astrophys... :
> “There are just so many things wrong with [the idea of a white dwarf inside the moon],” says Romer. “Now, a white dwarf is a very compact object. But, you know — people have heard of neutron stars — neutron stars are ultra-compact objects, they’re a few tens of kilometres across. White dwarfs are actually about the size of a normal star.”
You can come up with scenarios where white dwarfs are much smaller than a star, but smaller than the Moon is iffy at best.
As for the Dyson sphere idea, the biggest problem with it in this scaled-down scenario is stability. You can't exactly support it with struts, or something.
On that subject, I highly recommend the video "dyson spheres are a joke": https://www.youtube.com/watch?v=fLzEX1TPBFM , by astrophysicist Angela Collier. But you need to either watch all 53 minutes, or skip to near the end, to find out just how literal the title is.
the8472•3mo ago
api•3mo ago
the8472•3mo ago
"This implies that M must be less than 0.8% of the mass of the Earth"
NL807•3mo ago
Would it? I would've thought there is enough dust in the solar system that it would create constant xray emissions. Even if it's faint, it would stick out like a sore thumb on super sensitive xray telescopes.
TheOtherHobbes•3mo ago
Any tiny black hole born in the big bang would either have evaporated (if Hawking was right...) or would have grown much larger by now.
Even a moon-mass black hole (0.1mm) wouldn't be eating much, although its gravitational effects would be much more obvious.
antonvs•3mo ago
terminalshort•3mo ago
terminalshort•3mo ago
pavel_lishin•3mo ago
It would be detectable as an asteroid that's twice as dense as it should be.
Cthulhu_•3mo ago
api•3mo ago
AFAIK an asteroid mass black hole wouldn't evaporate yet since the CMB is still warmer than its Hawking temperature. Very tiny black holes would have evaporated earlier in the universe. A black hole evaporates when its Hawking temperature exceeds the ambient temperature.