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COMMENT PAGE FOR:
HTML Interstellar Mission to a Black Hole
dlasud wrote 3 hours 33 min ago:
Sied
LogicFailsMe wrote 18 hours 10 min ago:
Seems like first we need to get out of the gravity well...
Then we need to cure ageing to give people skin in these games...
Then we need to crack FTL or find a way to cryo-sleep or we end up with
dystopian science fiction ships of the damned...
Not in my lifetime I suspect...
optimalsolver wrote 18 hours 40 min ago:
Having read Michael Crichton's Sphere, I think I know how this ends.
hunterpayne wrote 19 hours 18 min ago:
Isn't Relativistic time dilation a problem for this idea? To the
probe, the trip is only a few centuries but to us on Earth, millions of
years. Maybe 0.1c isn't enough to cause this to be a huge problem but
I think it is. Perhaps one of you Einstein enjoyers can tell us for
certain.
prerok wrote 18 hours 21 min ago:
Time dilation is exponential. At 0.1c it's definitely measureable but
not a practical problem.
turtletontine wrote 18 hours 28 min ago:
Time dilation is 1/sqrt(1 - (v/c)^2). So at 0.1c thatâs 0.5%.
Certainly much higher than any human has ever experienced! But not
exactly gonna change 100y to 100,000,000y.
kakacik wrote 18 hours 31 min ago:
No need to be snarky and especially not here re basic science. Time
dilation happens exponentially, ie with 0.5c you don't have time
going 1/2 slower, rather a miniscule amount. Once you keep
approaching speed of light closer and closer, all things go extreme
(time, energy required, mass and so on).
amai wrote 23 hours 21 min ago:
What is the point of such a mission? There is literally nothing to see
there.
Cthulhu_ wrote 20 hours 55 min ago:
A black hole may be invisible but its accretion disk and the effects
on the light being deflected around it are anything but.
ck2 wrote 1 day ago:
The most aggressive yet most realistic project we could reasonably do
is the SGL Telescope
Won't happen under this administration and really might take a
planet-wide effort but it would be incredible [1] [2]
HTML [1]: https://www.centauri-dreams.org/2022/07/22/solar-gravitational...
HTML [2]: https://www.nasa.gov/general/direct-multipixel-imaging-and-spe...
HTML [3]: https://www.universetoday.com/articles/a-mission-to-reach-the-...
vee-kay wrote 1 day ago:
Related:
"Project Solar Sail" by Arthur-Clarke and others, is a good anthology
(stories, essays and illustrations) about the new Age of Sailing
(Sailing in Space)via lightships and solar sails.
wartywhoa23 wrote 1 day ago:
It is stated multiple times across the article that the probe would
need a means of changing is trajectory, but not even a hint of idea how
that could possibly be done is given. So the most important and
blocking aspect of the mission is simply skimmed over, and the rest of
it is built upon this omission as if it was something trivial to come
up 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.
ithkuil wrote 18 hours 54 min ago:
"steering" is a word that can lead to confusion because it leverages
the intuition that we have with our ground vehicles.
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
bawolff wrote 21 hours 58 min ago:
> So the most important and blocking aspect of the mission
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.
stronglikedan wrote 22 hours 29 min ago:
gyroscopes?
floxy wrote 1 day ago:
Since momentum is conserved, why not just have a 2 of the 1 g probes
strapped to each other with a spring in between. When you need a
course correction at 100 AU out (or whatever). The probes calculate
how much of a correction is needed, adjusts a screw that tightens or
loosens tension on the spring, reorients itself appropriately with a
reaction wheel, then the two probes are released from each other,
begin pushed apart with the spring. One probe gets the trajectory
correction it needs, and the other gets further off course. Maybe
with some gravity assists with nearby objects. [1] also:
Roundtrip Interstellar Travel Using Laser-Pushed Lightsails
HTML [1]: https://en.wikipedia.org/wiki/Gravity_assist
HTML [2]: https://ia800108.us.archive.org/view_archive.php?archive=/24...
sheepscreek wrote 11 hours 45 min ago:
Can a gyro work in space? Probably not or all the satellites would
be using it instead of gas/ionized gas based propulsion.
nandomrumber wrote 6 hours 53 min ago:
Gyroscopes are used in spacecraft / satellites in the same manner
they are in aircraft, to measure changes in orientation.
Reaction wheels are used to make adjustments to orientation. See
[1] Thrusters of all sorts can also be used, generally to
maintain altitude in satellites, and more generally to provide
thrust for space probes.
HTML [1]: https://en.wikipedia.org/wiki/Reaction_wheel
Cthulhu_ wrote 21 hours 5 min ago:
What would the "screw" push off of? That rotational force would
need to go somewhere or be corrected, else the probes would just
rotate. I guess a gyroscope could do that, but what you're
describing just sounds... very roundabout, and in terms of force, a
few kilos of propellant would have the same effect.
floxy wrote 20 hours 7 min ago:
This is infeasible for the reason other have mentioned about
specific impulse. But surely you can imagine a set of parallel
boards with a coil spring between them and a set of cylindrical
guide rods to prevent relative rotation between the boards. A
motor fixed to one board turns a screw that engages with threaded
nut on the other board, mounted on a thrust bearing, and guide
bushing that allows a linear movement, but disallows the rotation
degree of freedom. Think of the lead screw on a milling machine
or lathe.
Alex-Programs wrote 21 hours 10 min ago:
That's just a really, really ineffective rocket. A spring has
nowhere near the energy density of chemical fuel.
hinkley wrote 21 hours 21 min ago:
Because the specific impulse of the spring is negligible when
youâre moving at 1/10c and why would they send a 1g probe if they
could accelerate 100kg to that speed? Why do you suppose doubling
the weight would be free instead of making the system infeasible?
vjvjvjvjghv wrote 23 hours 44 min ago:
Isnât that basically how a rocket works? Throw stuff out one side
to get the thing on the other side moving. Not sure how this would
compare to a rocket engine with hyperbolic fuel.
hinkley wrote 21 hours 25 min ago:
Only in the sense that throwing a knife at someone is the same as
shooting a howitzer at them.
Specific impulse.
vjvjvjvjghv wrote 20 hours 41 min ago:
As far as impulse goes, the spring will probably be pretty
inefficient relative to mass.
sandworm101 wrote 19 hours 12 min ago:
No. Very much no. The spring system would literally throw
away half the mass of the craft for, maybe, a 10m/s delta.
Fireworks would be more efficient. A pitching machine
attached to a huge pile of baseballs would be more efficient
(ie the baseballs could be thrown faster).
celticninja wrote 3 hours 57 min ago:
They all weigh a lot more than 1g though.
hinkley wrote 21 min ago:
[1] Please read.
HTML [1]: https://en.wikipedia.org/wiki/Specific_impulse
hinkley wrote 20 hours 17 min ago:
The point we are trying to make is that there hardly anything
that would be less efficient relative to mass.
dylan604 wrote 22 hours 45 min ago:
It compares in that it doesn't require said hyperbolic fuel. That
fuel is heavy and finite.
mlsu wrote 9 hours 33 min ago:
You can think of the hypergolic fuel as a type of spring. The
chemical energy stored in the bonds of the fuel is what pushes
the fuel products apart when it reacts. This is what pressure
is, it's nothing more than KE of molecules.
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.
dylan604 wrote 2 min ago:
But a mechanical spring will reset itself to its natural
position once tension is released
lazide wrote 22 hours 30 min ago:
Uh, it does - the âfuelâ is the other probe.
Notably, this also has a particularly bad ISP?
Also, probes are presumably also heavier and rarer?
floxy wrote 23 hours 7 min ago:
Yes.
palmotea wrote 1 day ago:
> It is stated multiple times across the article...
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:
[1] > 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.
HTML [1]: https://www.cell.com/iscience/fulltext/S2589-0042(25)01403-8...
floxy wrote 1 day ago:
>I'm also wondering how such a thing is supposed to communicate
back to us over dozens of light years.
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.
palmotea wrote 23 hours 28 min ago:
> Send out the first batch of probes and then 5 years later send
another batch of probes.
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.
floxy wrote 23 hours 8 min ago:
Hmm. Seems like you are you multiplying 5 years by 33% of
light speed to come up with 1.65 light years? I apparently
didn't explain well enough. The 5 years is for the first batch
of probes to gather data over an extended period of time (while
in orbit around the black hole). The second set of probes is
just a roundtrip "fly-by" to collect the data from the first
probes and return it to earth. No reason that the return trip
probes would have to be very far from the data gathering
probes. Maybe you can't orbit close enough to the black hole
at these speeds without getting too close to the accretion
disk?
palmotea wrote 22 hours 29 min ago:
Even then, I think you're going to have massive distances
between tiny probes moving very fast relative to each other.
Maybe not 1.65 light years, but communication over Voyager's
0.00266 light years or even a much smaller distance (e.g.
Earth to moon) seems insurmountable for two 1g probes.
Also, the probes are in deep space, right? No solar power.
Where are they going to get the energy?
floxy wrote 20 hours 19 min ago:
So skip the communication, and just have the one probe do
the gravity assist to get headed back to earth with the
data it collected.
floxy wrote 21 hours 36 min ago:
[1] ?
HTML [1]: https://en.wikipedia.org/wiki/Betavoltaic_device
NoMoreNicksLeft wrote 1 day ago:
>I'm also wondering how such a thing is supposed to communicate
back to us over dozens of light years.
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.
VonTum wrote 16 hours 41 min ago:
We could call them "Sophons" while we're at it.
sigmoid10 wrote 1 day ago:
People don't realise this, but you can steer perfectly fine with a
solar sail. That's because photons transfer momentum not just when
they hit the sail, but also when they are emitted after reflection.
So just by turning the sail at an angle, you can create a force in
any direction perpendicular to the velocity vector. Using a two sail
system, you can even accelerate and slow down along a single beam
path. So you could theoretically travel to mars with a constant
acceleration/deceleration phase (like a flip-and-burn in the Expanse)
using only one beam emitter on earth.
kragen wrote 22 hours 44 min ago:
How long would it take for a person to get to Mars with a sail
powered by an Earth-based laser?
lazide wrote 17 hours 25 min ago:
Infinite time since we have no realistic way of making such a
laser at this time - and anyone trying it is likely to get nuked
before they finish their massive death ray.
kragen wrote 16 hours 8 min ago:
Stipulate that we have the laser.
sigmoid10 wrote 8 hours 37 min ago:
Depends entirely on the power output of the laser, the
dispersal length and the size, weight and reflectivity of the
sail. Since we are already talking about imaginary
technology, any answer between "slower than current chemical
rockets" and "some significant fraction of the speed of
light" could be valid.
marcellus23 wrote 1 day ago:
It's not skimmed over, they cover it near the end in the
"Requirements and challenges" section:
> 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.
hinkley wrote 21 hours 17 min ago:
Thereâs a really straightforward way to avoid a parabolic
trajectory with a black hole. But data retrieval gets a bit
difficult.
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.
marcellus23 wrote 20 hours 11 min ago:
Not every black hole has an accretion disk, especially not
isolated ones.
hinkley wrote 11 hours 13 min ago:
So the question there is if itâs worth it for us to study a
naked singularity. What would it teach us?
And how do you get into orbit?
celticninja wrote 3 hours 54 min ago:
Is it worth studying?
Yes. Yes it most certainly is. Whatever we learn will be new.
estimator7292 wrote 1 day ago:
Solar sails. You can fire a shit ton of lasers from the planet (or
orbit) at the probes and very,very slowly boost them up to the
desired velocity.
dvh wrote 1 day ago:
Simply. You do Monte Carlo with the probes. You fire 1000 and one or
two will have perfect trajectory so that no correction is needed.
gus_massa wrote 1 day ago:
I don't think 1000, or even 1000000 are enough if you use random
directions. Space is huge. This has been posted here afew times
HTML [1]: https://joshworth.com/dev/pixelspace/pixelspace_solarsyste...
magnat wrote 1 day ago:
Did you, by any chance, play Outer Wilds recently?
antonvs wrote 1 day ago:
Easy fix: change the description to "Interstellar Mission to the
General Galactic Vicinity of a Black Hole"
Mistletoe wrote 1 day ago:
How do you stop if your solar sail has you going near light speed? Or
does it strand you halfway between stars in the doldrums where the
force on both sides of your sail equals out from two stars?
kakacik wrote 18 hours 23 min ago:
I don't think we can just go near speed of light. Even hard vacuum
out there contains particles. Heliosphere is chock full of them, then
Oort cloud has stuff way bigger than that (or any probe), even if
sparsely spread out. Then there is cosmic stuff outside, as Voyager
found out.
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.
prerok wrote 18 hours 11 min ago:
Nit: shields were just for battle, for this they used the
deflector.
Razengan wrote 1 day ago:
> Or does it strand you halfway between stars in the doldrums where
the force on both sides of your sail equals out from two stars?
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 :)
dumpsterdiver wrote 1 day ago:
Itâs where the future hides :)
jiggawatts wrote 1 day ago:
If intelligent life evolved on a planet of a brown dwarf â a
âfailedâ star â that was ejected from its original galaxy
deep into intergalactic space, then that species would be
spectacularly isolated.
Note that the ânaked eyeâ 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?
Razengan wrote 18 hours 55 min ago:
> If intelligent life evolved on a planet of a brown dwarf â a
âfailedâ star â that was ejected from its original galaxy
deep into intergalactic space, then that species would be
spectacularly isolated.
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
floxy wrote 23 hours 56 min ago:
Do we have a good estimate for the density of intergalactic
stars? Or how far away from a star will you be on average, when
you are, say halfway between the Milky Way and Andromeda?
HTML [1]: https://en.wikipedia.org/wiki/Intergalactic_star
jiggawatts wrote 10 hours 58 min ago:
Apparently this is very new science, the information is still
being collected as cutting edge research.
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.
SiempreViernes wrote 1 day ago:
You don't stop this type of craft, it's strictly accelerate and coast
type of thing.
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.
ianburrell wrote 19 hours 35 min ago:
Solar sails aren't powered by solar wind but by light reflecting
off like the probe. But the probe would be powered by laser so not
really "solar" sail. Light sail is the generic term.
zelos wrote 1 day ago:
This suggests ejecting a secondary mirror in front of the craft to
reflect light to brake the original craft: [1] :
"...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"
HTML [1]: https://arxiv.org/pdf/1604.01356
dotnet00 wrote 19 hours 40 min ago:
Flipping the sail around would probably be the lightest option,
though tricky because the larger sail designs would not be rigid.
hvb2 wrote 1 day ago:
You would fold the sail?
hansmayer wrote 1 day ago:
That would not stop the probe from continuing to glide further.
He's making a good point here.
ceejayoz wrote 1 day ago:
Gliding is fine. We whizzed past Pluto with New Horizons. Never
stopped, just a photo flyby.
voidUpdate wrote 1 day ago:
That only stops you accelerating, it doesn't put the brakes on
jordanb wrote 1 day ago:
Deceleration is the same as acceleration. You use the light of
the star you're approaching to slow down.
Cthulhu_ wrote 20 hours 56 min ago:
But if you're going near light speed, the light / particles
would be too faint to have any significant effect until you get
very close. You'd basically just fly backwards straight into
it. Unless your sail is very large and/or the total mass is
very small.
hansmayer wrote 1 day ago:
Such a fantastic overview. And here we are, instead of building the
infrastructure for accelerating solar sails, we're investing the money
in AI-pornbots instead :/
wewtyflakes wrote 15 hours 20 min ago:
Well, they are both on a mission to a black hole.
Cthulhu_ wrote 20 hours 52 min ago:
AI porn sells, solar sails are a research project at best. There is
no money to be made from space flight, only discovery, and
unfortunately capitalist forces far outweigh curiosity.
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.
TheOtherHobbes wrote 1 day ago:
What are the odds the first alien probe to visit the solar system
will be a pornbot or some form of marketing droid?
Cthulhu_ wrote 20 hours 52 min ago:
If you subscribe to the Futurama school of comedy, very high, lol.
prerok wrote 18 hours 0 min ago:
HTML [1]: https://xkcd.com/1642/
radu_floricica wrote 1 day ago:
Considering AI-pornbots are increasing the derivate of the function,
they might actually be the right move.
einrealist wrote 1 day ago:
At least the AI-pornbots will operate from space. /s
api wrote 1 day ago:
Whatâs be super cool is discovering a! asteroid mass primordial black
hole in our solar system. No epic interstellar flight needed.
It would be super hard to detect though. Weâd 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 itâd be so small that the signal would be weak.
Cthulhu_ wrote 20 hours 58 min ago:
If it was asteroid mass, wouldn't it have the same gravitational
effect of an asteroid itself? Plus, someone else mentioned it'd be
like a micron across, which if my pop-sci understanding of these
things is correct, it'd disappear in a poof of hawking radiation.
api wrote 19 hours 36 min ago:
It would have the same mass, and it would be tiny -- like the size
of a hydrogen or helium atom.
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.
pavel_lishin wrote 23 hours 32 min ago:
I remember reading somewhere that it's possible for such a black hole
to get captured by an asteroid (or vice versa, I guess), and happily
live inside a rock, slowly orbiting inside the asteroid, sucking up
atoms here and there.
It would be detectable as an asteroid that's twice as dense as it
should be.
terminalshort wrote 1 day ago:
Could you find it by Hawking radiation?
antonvs wrote 1 day ago:
We wouldn't have to get lucky if it was on the last stages of
evaporating. If it has reached a mass of about a billion kg it would
be shining plenty bright to detect, and would only have a few
thousand years to live before destroying most life on Earth with
gamma radiation.
terminalshort wrote 1 day ago:
According to this calculator [1] , the luminosity would only exceed
that of the sun for 46.7 nanoseconds, so unless it's much less than
1 AU away we would probably be fine.
HTML [1]: https://www.vttoth.com/CMS/physics-notes/311-hawking-radia...
NL807 wrote 1 day ago:
>It would be super hard to detect though.
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 wrote 1 day ago:
An asteroid-mass black hole is around a micron across. It's not
going to be nomming on much because the matter distribution inside
the solar system isn't that dense.
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.
the8472 wrote 1 day ago:
We do not what such a thing anywhere near Earth though.
HTML [1]: https://arxiv.org/abs/astro-ph/9911309
api wrote 19 hours 35 min ago:
Only if it evaporates, which it probably wouldn't do for billions
of years.
the8472 wrote 16 hours 21 min ago:
Something of asteroid mass would be above the CMB equilibrium
temperature, thus already be undergoing runaway evaporation. From
the paper:
"This implies that M must be less than 0.8% of the mass of the
Earth"
noam_k wrote 1 day ago:
That would be cool.
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".
antonvs wrote 1 day ago:
If it's in a stable orbit in the solar system, it wouldn't be able
to "eat" us. Black holes gravitate exactly the same as any other
mass, so it would have the same gravitational effect on Earth as
any object if the same mass.
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 wrote 22 hours 11 min ago:
There was a movie where Moon was a hi-tech 'megastructure' with a
white dwarf inside. I wonder if it would be theoretically
possible to set up such a mini-dyson sphere around a
mini-blackhole.
api wrote 19 hours 33 min ago:
If you set it up at the right radius it would have 1g gravity
at the surface, like a little mini-world. It wouldn't be able
to hold an atmosphere though, so it would have to have
pressurized buildings on it.
throwaway290 wrote 40 min ago:
Somebody write a sci fi with this please, just make sure to
describe how trash disposal works
MomsAVoxell wrote 1 day ago:
Hey, its not like an analog of "Yeah, lets just throw some more
mass at the newly-forming black hole in our neighbourhood", said
every human that has ever thrown things into the fire, forever ..
api wrote 19 hours 39 min ago:
Black holes aren't cosmic vacuum cleaners. They're just super
super super compact objects.
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.
gus_massa wrote 1 day ago:
Sorry, but I have to link the "Hole Lotta Trouble" episode of
Pocoyo
HTML [1]: https://www.youtube.com/watch?v=HL_0OL7vZ44
MomsAVoxell wrote 19 hours 46 min ago:
Yes, you really do.
DIR <- back to front page