[HN Gopher] Kepler telescope glimpses population of free-floatin...
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Kepler telescope glimpses population of free-floating planets
Author : jaytaylor
Score : 154 points
Date : 2021-07-06 16:45 UTC (6 hours ago)
(HTM) web link (phys.org)
(TXT) w3m dump (phys.org)
| 0-_-0 wrote:
| Can we use this data to calculate how many rogue planets per star
| are in our galaxy?
| actually_a_dog wrote:
| This is expected to be the ultimate fate of the gas giants
| (Jupiter, Saturn, Uranus, and Neptune) after the Sun leaves the
| main sequence in about 5 billion years. Within 30 billion years
| of the Sun becoming a red giant, Jupiter and Saturn are predicted
| to fall into a 5:2 orbital resonance that destabilizes the
| system, eventually causing all but 1 planet to be ejected within
| 30 billion years. The remaining planet is expected to be ejected
| within another 50 billion or so years.[0]
|
| So, within about 100 billion years, all that's going to be left
| of our solar system is a white dwarf (which will likely survive
| for trillions of years[1]), and 4 rogue planets, each drifting
| alone in space.
|
| Somehow, I think this little story is more interesting than the
| posted article, perhaps because it literally hits home.
|
| ---
|
| [0]: https://arxiv.org/pdf/2009.07296.pdf
|
| [1]: https://en.wikipedia.org/wiki/White_dwarf#Fate
| ketanmaheshwari wrote:
| Would time even make any sense given that we use the very
| system to measure time.
| klodolph wrote:
| We stopped using the solar system to measure time a while
| ago, and now use atomic clocks. Civil time is periodically
| adjusted to match the rotation of the Earth, but the amount
| of adjustment necessary is measured using atomic clocks, and
| atomic clocks are still the basis of civil time.
| actually_a_dog wrote:
| Yes:
|
| > The second is defined as being equal to the time duration
| of 9,19,26,31,770 periods of the radiation corresponding to
| the transition between the two hyperfine levels of the
| fundamental unperturbed ground-state of the caesium-133 atom.
|
| https://en.wikipedia.org/wiki/Second
|
| Unless the laws of physics aren't constant over very long
| time periods for some reason, we could (if we were around to
| do it) measure time 10^18 years from now just the same as we
| do today.
| lizknope wrote:
| In Oklo, Gabon there was a natural nuclear fission reactor
| about 1.7 billion years ago. The concentration of uranium
| and groundwater was just right that nuclear fission
| occurred naturally.
|
| We can measure the elements left behind and we have
| determined that the fine structure constant was the same
| then as it is now.
|
| If the laws of physics have remained constant for that long
| then most scientists think they will remain constant in the
| future.
|
| https://en.wikipedia.org/wiki/Natural_nuclear_fission_react
| o...
| actually_a_dog wrote:
| Oh, sure, I wasn't saying the laws of physics were
| _likely_ to change, simply that _if_ they did, the SI
| definition of time might not be well posed.
|
| That said, although I agree the laws of physics are
| likely to remain constant, 1.7 billion years is only just
| about 12% of the age of the Universe. And, that time
| period only reflects the most _recent_ 1.7 billion years.
| So, there 's still some theoretical wiggle room there for
| the fine structure constant to vary over time. After all,
| heat death is not expected to occur for much more 100
| trillion years (if that is our ultimate fate)! [0]
|
| Edit: Come to think of it, if the laws of physics _aren
| 't_ constant, how would it be possible to pose a coherent
| definition of a unit of time at all?
|
| ---
|
| [0]: https://en.wikipedia.org/wiki/Future_of_an_expanding
| _univers...
| LeifCarrotson wrote:
| In the sense that one second is 9,192,631,770 transitions
| between two energy levels of the caesium-133 atom, no,
| there's no change. 50 billion years is just shorthand for a
| multiple of this number of transitions. International Atomic
| Time, or TAI, is precisely defined for this kind of
| measurement.
|
| Whether TAI is a fixed number of leap seconds away -
| potentially billions - from UTC, is another question
| entirely. If 'one day' is one rotation of the planet Earth
| around its axis, and 'one year' is one rotation around the
| Sun, and hours, minutes, and seconds are fractions of these
| rotations, yeah, those cease to have much meaning when the
| planet is swallowed up by and dissolved into the Red Giant
| Sun's expanding chromosphere.
| aquova wrote:
| Assuming the gas giants remain roughly the same as they are
| now, what would happen to them as they left the solar system
| and the heat of the sun? Would the gases condense down turning
| them from gas giants into rocky planets?
| Tuna-Fish wrote:
| Eventually, but it would take much, much longer than you'd
| think.
|
| Jupiter, Saturn and Neptune all radiate ~2x the heat they
| receive from the Sun. Most of their heat is primordial,
| residue from the gravitational potential energy of all their
| component parts falling together. A gas giant flung away from
| it's host star will likely remain more or less as it is much
| longer than the star is.
| areoform wrote:
| > Jupiter, Saturn and Neptune all radiate ~2x the heat they
| receive from the Sun.
|
| As I've said elsewhere, this is most surprising for
| Neptune, but the fact that these bodies radiate this much
| heat is a clue that something more is going on.
|
| The primordial heat hypothesis doesn't hold up, as Uranus
| was formed around the same time as Neptune and its energy
| balance is 1.05. If the comparison is indeed accurate, then
| the question remains what is making these planetary bodies
| so hot? Neptune especially.
|
| Here are the energy balances of each to our best estimates,
|
| Jupiter, 2.132 +- 0.051 [current estimate, older estimate
| was, 1.668 +- 0.085] (source,
| https://www.nature.com/articles/s41467-018-06107-2#Sec2)
|
| Saturn, 1.78 +- 0.09 (source, https://www.sciencedirect.com
| /science/article/abs/pii/001910... )
|
| Neptune 2.61 +- 0.28 (source, https://agupubs.onlinelibrary
| .wiley.com/doi/abs/10.1029/91JA... )
|
| My tweets on the topic,
| https://twitter.com/_areoform/status/1373376028861734918
| Tuna-Fish wrote:
| > as Uranus was formed around the same time as Neptune
|
| [citation needed]
|
| There is clearly an unexplained anomaly vis-a-vis Uranus
| and the other giant planets. But the closer you look at
| them, the more weird Uranus appears. It would be amazing
| if it turned out to be a much older planet captured by
| our solar system. (That would certainly explain the
| weirdo rotation...)
| areoform wrote:
| Here you go!
|
| https://books.google.com/books?id=RaJdy3_VINQC&pg=PA224&l
| pg=...
|
| https://iopscience.iop.org/article/10.1088/0004-637X/789/
| 1/6...
|
| http://www.psrd.hawaii.edu/Aug01/bombardment.html
|
| For me the anomaly is the heat of these planets, and the
| physical processes this suggests. I suspect that our
| current explanations are only partial and that a great
| discovery lies somewhere here.
| actually_a_dog wrote:
| Just to add on to this, NASA estimates that the internal
| core temperature of Jupiter could be as hot as 24,000degK
| [0]. For reference, the Sun's photosphere has a temperature
| of about 6000degK [1].
|
| ---
|
| [0]: https://www.nasa.gov/audience/forstudents/5-8/features
| /nasa-...
|
| [1]: https://www.scientificamerican.com/article/i-read-
| that-the-s...
| Florin_Andrei wrote:
| Okay, so as long as you have 3 or more bodies, I understand
| ejection. Energy gets transferred semi-randomly such that
| eventually one body gains too much energy and shoots out.
|
| But when N=2, what is the ejection mechanism? That's an
| elliptical orbit that should be spinning round and round
| forever (sans the losses via gravitational waves).
| actually_a_dog wrote:
| You mean how does the last planet get ejected? Well, that's
| an interesting question, actually. Because of the inherent
| stability of the 2 body system, the last planet gets ejected
| some ~50 billion years after the others.
|
| The authors' simulation takes into account the fact that a
| star comes close enough to the Solar System to have some
| tangible effect every 23M years or so. It's the cumulative
| effect of these stellar flybys that eventually nudges the
| last planet out of the system.
| ByThyGrace wrote:
| > the fact that a star comes close enough to the Solar
| System to have some tangible effect every 23M years or so
|
| Do you have a good source that expands on this? That sounds
| so interesting.
| Florin_Andrei wrote:
| Ok, external perturbation, got it.
|
| Yeah, that makes sense. Otherwise it would just very slowly
| spiral in, due to losses from general relativity.
| actually_a_dog wrote:
| Yep, and loss of angular momentum due to it being carried
| away by gravity waves would probably take many trillions
| of years, I would guess.
| jcims wrote:
| Understanding there's orders of magnitude of possible scale,
| what's the likelihood that one of these passing through the
| solar system would destabilize it enough to affect Earth? What
| happens if it hits the sun?
| vimacs2 wrote:
| Very low but a more common and likely possibility is that it
| could disturb the oort cloud and cause comets to fall in
| system. Guess that could classify as what you are referring
| to depending on your definition of solar system.
|
| A passing star is more likely to do this though and we
| believe that they indeed have caused disturbances in our oort
| cloud in the past. They might be potentially less numerous
| than rogue planets as our universe ages but they have a far
| larger potential hill sphere than even a very large planet so
| interactions with neighboring stars' hill spheres are more
| likely and frequent.
| adolph wrote:
| I've normally seen "oort" capitalized, so here is some
| background if others have the same question as me.
|
| _The Oort cloud ( /o:rt, U@rt/),[1] sometimes called the
| Opik-Oort cloud,[2] first described in 1950 by Dutch
| astronomer Jan Oort,[3] is a theoretical[4] concept of a
| cloud of predominantly icy planetesimals proposed to
| surround the Sun at distances ranging from 2,000 to 200,000
| au (0.03 to 3.2 light-years).[note 1][5] It is divided into
| two regions: a disc-shaped inner Oort cloud (or Hills
| cloud) and a spherical outer Oort cloud. Both regions lie
| beyond the heliosphere and in interstellar space.[5][6] The
| Kuiper belt and the scattered disc, the other two
| reservoirs of trans-Neptunian objects, are less than one
| thousandth as far from the Sun as the Oort cloud._
|
| https://en.wikipedia.org/wiki/Oort_cloud
| alistairSH wrote:
| It was not very long ago that I realized the outer bounds
| of our Oort cloud are actually closer to Alpha Centauri
| (4.25 light years away) than the sun.
|
| The scale of the universe never ceases to elicit feelings
| of existential dread.
| actually_a_dog wrote:
| The outer edges of the cloud seem to be at ~100K AU [0],
| while the a Centauri system is ~268K AU from us [1]. NASA
| also gives the same number [2] for the distance to the
| edge of the cloud. So, it looks like the Cloud extends
| _almost_ halfway to a Centauri, but not that it 's
| "closer to a Centauri than us").
|
| As for the scale of the Universe:
| https://htwins.net/scale2/
|
| ---
|
| [0]: https://en.wikipedia.org/wiki/Oort_cloud#/media/File
| :PIA1704...
|
| [1]: https://imagine.gsfc.nasa.gov/features/cosmic/neares
| t_star_i...
|
| [2]: https://solarsystem.nasa.gov/solar-system/oort-
| cloud/overvie...
| actually_a_dog wrote:
| This sounds reasonable to me, assuming Mercury didn't
| either fall into the Sun or hit Venus. However, from the
| perspective of Earth, we might not notice this much, due to
| the effect of Jupiter (usually) either flinging comets away
| from us, or actually absorbing the impact of the comets.
| actually_a_dog wrote:
| Ejection of the gas giants doesn't even take place until
| after the Sun has gone into its red giant phase. The Sun will
| swell so much that it engulfs the inner planets (Mercury,
| Venus, Earth, Mars), so, Earth won't even be around to become
| destabilized.
|
| Interestingly, the paper I linked talks about Mercury having
| a 1% chance of becoming unstable _before_ the Sun enters its
| red giant phase:
|
| > The mechanism forthe onset of Mercury's instability is well
| understood: by virtue of locking into a linear secular
| resonance with theg5mode of the solar system's secular
| solution, Mercury's eccentricity can attain near-unity
| values, resulting in a collision with the Sun, or even Venus.
| Intriguingly, General Relativistic effects factor into this
| estimate, with ancillary apsidal precession providing a
| stabilizing influence on Mercury's orbit.
|
| If Mercury collides with the Sun, not much interesting will
| happen. Mercury doesn't have enough mass to disrupt the
| center of gravity of the Solar System when it falls into the
| Sun, so, all that will happen is that the planet will get
| vaporized, and the Sun will become infinitesimally more
| enriched in metals. If you were around to witness the event,
| it might be _visually_ spectacular, but not particularly
| significant with respect to the fate of the system itself.
|
| They go on to say:
|
| > Within the context of this narrative, however, the
| remaining planets appear unaffected and are currently
| expected to remain stable for a lower limit of 10^18 years,
| when diffusion arising from the overlapping mean motion
| resonance of Jupiter and Saturn are expected to decouple
| Uranus.
|
| This analysis, however, is reflective of older studies, which
| don't take into account certain factors that this paper does.
| kjs3 wrote:
| _If Mercury collides with the Sun, not much interesting
| will happen._
|
| Yeah...but if it hits Venus......
| twiddling wrote:
| If they are in a pentagon formation then it is simply the
| Puppeteers
| CodeGlitch wrote:
| So it's entirely possible for one of these rogue planets to cross
| into our solar system and disrupt the stable orbits of any
| planet, including earth or the moon...
| actually_a_dog wrote:
| Sure, but a rogue planet would be far, far less disruptive than
| a star coming near enough to us to affect the Solar System.
| Such stellar flybys, according to a paper I linked in a
| previous comment, occur every ~23M years, and are, indeed,
| expected to act as a destabilizing force on the Solar System
| over long periods of time.
| cletus wrote:
| The prospect and opportunity of rogue planets is fascinating to
| me.
|
| So I'm firmly in the camp that the speed of light is a hard limit
| in the Universe. Any talk of wormholes, FTL and space folding
| just seems like wishful thinking and the product of not
| understanding the domain of functions (eg putting negative values
| into mass or energy).
|
| Additionally there's macro evidence to this speed limit because
| if it wasn't a limit it would make the likelihood of encountering
| spacefaring civilizations that much more likely.
|
| So given this, it seems like traveling to other stars requires
| some form of generational ship. And that seems like a problem
| because the energy required is massive and that's even before you
| get into issues of having reaction mass. There are workarounds
| for this (eg space laser propulsion) but the problems seem...
| significant.
|
| So, rogue planets. I wonder if the first vessel for interstellar
| travel will in fact be some largish rogue body that visits the
| Solar System. Even something 100km wide will contain a wealth of
| raw materials that would otherwise be prohibitively expensive to
| accelerate to interstellar speeds.
|
| And sure it might take 10,000 years or more for such a body to
| travel to a nearby star but there's really not a lot of
| difference between several centuries and 10,000 years.
|
| What's more, such travelers could likely seed other rogue bodies
| they encounter along the way.
|
| Could this be the initial vector of interstellar colonization?
|
| As an aside, George RR Martin 40+ years ago wrote a book called
| Dying of the Light. I really enjoyed it just for the concept. In
| this book there are so-called Festival worlds. These are worlds
| that wander between systems. When they approach stars they get
| sufficiently warm and thaw out and may have oceans and
| atmospheres in that time. People would build cities in that time
| knowing it was all temporary.
| avaldes wrote:
| > As an aside, George RR Martin 40+ years ago wrote a book
| called Dying of the Light. I really enjoyed it just for the
| concept. In this book there are so-called Festival worlds.
| These are worlds that wander between systems. When they
| approach stars they get sufficiently warm and thaw out and may
| have oceans and atmospheres in that time. People would build
| cities in that time knowing it was all temporary.
|
| Wow so this could be the explanation for erratic seasons of
| unpredictable duration in ASOIAF?
| InitialLastName wrote:
| Everything about ASOIAF can be explained by George RR
| Martin's long career as a military science fiction author.
|
| How else could one be free to build a medieval fantasy world
| so unburdened by historical realism?
| the_af wrote:
| Which long career as a military science fiction writer?
|
| I admit aside ASOIAF I haven't read much GRRM -- his
| awesome _Sandkings_ short story, and his collaboration with
| Lisa Tuttle, _Windhaven_ , and I'm aware of some of his
| horror/fantasy fiction.
|
| Checking on Wikipedia I don't see a lot of military scifi
| in the list...
| kzrdude wrote:
| There is no explanation for the erratic seasons. GRRM (just
| like any storyteller) creates mystery and interest in his
| world and fills in the details that are required, and not so
| many of those that are not.
|
| This is something he is very aware of. He will tell you that
| like any intriguing medieval world map, his world map also
| has tall tales, mysteries and stories about foreign
| countries, big monsters and weird men, lining the edge of the
| map.
| blacksmith_tb wrote:
| Hitching a ride on a fast-moving extrasolar object passing
| through sounds good, though it seems like finding one going the
| right direction (and with enough time to get aboard) would be
| tricky. I suppose once you landed on it you could try and alter
| its course with mass drivers, but of course the more massive it
| was, the harder that would be.
| actually_a_dog wrote:
| If such a rogue planet were the result of ejection from its
| previous planetary system, I wouldn't expect that its speed
| would much exceed its previous orbital velocity in terms of
| order of magnitude. For reference, the orbital velocity of
| Mercury is about 60km/s [0], which is about 130,000 mph, or
| 2e-4*c.
|
| We'd certainly notice something as big as a planet coming at
| us when it's at around the same distance as the Oort cloud,
| which NASA says lies at a distance of at least 2000 AU [1],
| or 3e12 km. Since it would take almost 1600 years to travel
| 3e12 km at 60km/s, I would say we'd have a fair amount of
| preparation time, even if my estimate for the body's speed
| were off by a factor of 15. ;-)
|
| As for choosing your course, I would say if a rogue planet is
| about to enter the Solar System, beggars can't be choosers.
|
| What I find more interesting is that in order for people to
| live on or near such a planet, it would almost have to have
| enough of its own internal heat to create temperatures
| suitable for life. So, you're almost certainly _not_ looking
| at a rocky planet with a surface. Therefore, you 'd want to
| design your habitat to orbit or exist within the atmosphere
| of a gas giant. To my knowledge, there hasn't been any
| serious proposal for such a habitat, and I'm unaware of the
| sci-fi perspective on this issue.
|
| Of course, the other issue is that at 2e-4*c, you're not
| going anywhere very fast. :P
|
| ---
|
| [0]: https://nssdc.gsfc.nasa.gov/planetary/factsheet/mercuryf
| act....
|
| [1]: https://solarsystem.nasa.gov/solar-system/oort-
| cloud/overvie...
| eloff wrote:
| What's the point of interstellar colonization?
|
| It's possible that will never be interesting to us given the
| expense, time, and hardships involved.
|
| We have more than enough space and resources in this solar
| system to support north of a trillion humans if we start
| building space habitats. So even if we start procreating again
| after our population is predicted to stabilize, we won't run
| out of room here very easily.
|
| My feeling is our digital worlds will get so engrossing we will
| turn our attention inwards rather than outwards. I don't think
| that lends itself to either population growth or interstellar
| colonization.
|
| If intelligent civilization is sufficiently rare, that could
| easily explain the Fermi paradox. They're out there, just too
| far away and too uninterested in expansion for us to meet.
| m4rtink wrote:
| Even digital worlds need power to run and mass for hardware
| to run on. Eventually there will not be enough of that in
| Solar System and you will have to expand.
|
| Also more source material from real world events could be
| useful for bootstrapping.
| benlivengood wrote:
| > What's the point of interstellar colonization?
|
| Gamma ray bursts can probably take out a whole solar system.
| So could rogue stars or black holes. I think humanity is neat
| and want it and its descendents to survive until the heat
| death, so interstellar colonization it is.
| saiya-jin wrote:
| We have the potential for greatness. If only we could
| somehow tame the darker aspects of humans we would actually
| deserve a fate like this and probably be able to do it (or
| at least that's my wishful thinking).
|
| But yeah diversification at least 100 light years around in
| neighboring systems would greatly increase our chances of
| survival any kind of random brutal event (unless one of our
| neighbors goes supernova). It will be more of a question of
| survival rather than 'do we want to colonize that other
| system'
| shkkmo wrote:
| I see two major dynamics that could drive interstellar
| colonization:
|
| 1) Eccentricity and Boredom: I think that with a solar system
| population in the trillions, you will inevitably have a
| sufficient population of eccentrics to eventually launch
| generational ships. This is especially likely if humanity
| survivea long enough for the lifetime our own sun to present
| a realistic limit on the survival of the species.
|
| 2) Eccentricity and Freedom: The major advantage of
| interstellar colonization is distance from dominant power
| structures in the solar sytem. I find it quite possible that
| there could be societies that view fleeing the solar system
| as their only path to survival as a cultural unit.
| Sanzig wrote:
| One of the interesting consequences of interstellar
| colonization in a universe without FTL travel or
| communication (which, by all indications, appears to be our
| universe) is the sheer amount of cultural diversity it
| would create. Even adjacent systems would have
| communications round-trip times on the order of single-
| digit years, and depending how far apart desirable systems
| for colonization are it could even conceivably be decades
| of round-trip comms lag to the nearest inhabited system.
| Centralization becomes impossible, and star systems would
| have only very weak cultural impact on their neighbors.
| shkkmo wrote:
| Interstellar trade of physical goods is quite impractical
| without FTL. If there is interstellar travel for non-
| colonization purposes it seems like the primary goal
| would be to enable low-latency communication to
| compensate for semantic/cultural drift that could
| interfere with the efficacy of the high latency
| communcations.
| m4rtink wrote:
| Not just cultural but also possibly biological/corporeal
| diversity as the different cultrues start to adapt to
| their specific local environments.
|
| The Orions Arm collaborarive hard SF universe has very
| many first contacts due to this as as often two
| civilisations of human origin that meet each other look
| to each other totally alien (one can survive in liquid
| methane, the other near stars in hard vacuum). They did
| meet a few actual (and very unique) aliens but it took _a
| lot_ of verification it 's not just another hyper adapted
| modification happy ofshoot of humanity. :)
| BurningFrog wrote:
| You or I won't go on this trip, but I'm sure _some_ people
| are crazy /bold enough to do it.
|
| And that's all it takes.
| dave_sullivan wrote:
| You would find "the transcension hypothesis" very
| interesting, it's along similar lines to what you are
| discussing.
| pfdietz wrote:
| > What's the point of interstellar colonization?
|
| The cheapest way to fully explore another stellar system is
| probably colonizing it, so explorers can be manufactured in
| situ.
| thechao wrote:
| We'll run out of _sun_ at some point, even though (most) of
| the time left for the energetic universe is still available.
| cletus wrote:
| > What's the point of interstellar colonization?
|
| Ultimately it's to claim matter, which is the ultimate
| limiting factor in how long a civilization lives. For
| example, you talk about engrossing digital worlds. Well,
| those worlds require energy and energy means matter.
|
| To be clear we're talking on truly staggering time frames
| here where a trillion years is a mere blink of an eye [1][2].
|
| [1]: https://www.youtube.com/watch?v=Qam5BkXIEhQ&t=107s
|
| [2]: https://www.youtube.com/watch?v=Pld8wTa16Jk&t=1108s
| shkkmo wrote:
| The most likely form of non-generational inerstellar travel is
| finding high efficiency methods to accelerate ships to high
| relatavistic speeds so that time dilation reduces the on-ship
| time to sub-generation scales.
| tempest_ wrote:
| There is an interesting book called Lockstep that explores
| how a civilization might work without light speed.
| Essentially they have perfected cryogenic sleep and the
| entire civilization moves in lockstep, sleeping for many
| years between waking up which allows for ships to move
| between.
|
| The book itself is only so so but the concept is interesting
| non the less.
| cletus wrote:
| This sounds appealing but there are a couple of major
| problems.
|
| The first is that you have to get to a significant percentage
| of light speed for this to manifest itself. Even at 0.95c
| time is only traveling at 1/3 of normal speed [1].
|
| Second, the energy cost for this is truly mind-boggling.
| Doing so when you carry the fuel seems highly impractical.
| The best bet are laser highways [2]. But, you need to build
| that first.
|
| The upper limit of laser propulsion isn't really high enough
| for that level of time dilation.
|
| Third, traveling at these speeds makes any potential impact
| within even a speck of dust potentially fatal.
|
| Lastly, fun fact: such a ship actually needs to be
| aerodynamic. Why? Above 0.95c the drag of hydrogen atoms in
| the interstellar medium will start to slow you down.
|
| [1]: https://www.fourmilab.ch/cship/timedial.html
|
| [2]: https://www.youtube.com/watch?v=oDR4AHYRmlk
| Myto wrote:
| You could get to the nearest star in a few years and to the
| other side of the galaxy well within a human lifetime with
| "just" constant 1 g acceleration. Obviously this is far
| from easy but it doesn't seem like it is necessarily out of
| reach given a few thousand more years of continued
| technological development.
| actually_a_dog wrote:
| Yes, and there are at least 76 stars ( _i.e._ potentially
| interesting destinations) within 100 light years of us
| [0]. So, assuming you can set an arbitrary course at
| 0.95c, and decelerate without turning the humans inside
| your ship to organic goo, you can reach quite a few
| interesting places.
|
| ---
|
| [0]: http://www.solstation.com/stars3/100-as.htm
| aardvark179 wrote:
| The quotes you put round just are doing a lot of heavy
| lifting. If you had a perfect photon rocket you'd only
| need 1000000000 kg of fuel for each kg of payload to do
| 1g to the centre of our galaxy and slow down again.
|
| Okay, maybe you can use a laser or something so you don't
| have to carry the fuel with you, but you'll still need a
| staggering amount of energy because the rocket equation
| is a harsh mistress, and the relativistic version is even
| worse.
| shkkmo wrote:
| Absolutely, there are huge problems and it may not ever be
| feasible. However, I find it far more likely that we will
| find a way to solve these concerns than that we will
| develop FTL travel.
| m4rtink wrote:
| The thing will also be a weapon of mass destruction of
| plannet cracking potential, one "parking accident" away
| from making planets uninhabitable.
|
| On the other hand a civilisation producing such things
| should hopefully be technically immortal with lots of
| distributed backups for each individual potentially
| affected by such accidents & resources to fix up any
| affected infrastructure. So still, totally worth it, go fo
| it! :-)
|
| (Less advanced neighbors might still be a bit on the edge,
| so please be considerate.)
| abecedarius wrote:
| Send a small autonomous robot; at the destination it builds a
| high-bandwidth radio receiver and factories; then 'upload'
| the colonists by radio. Much more practical if your
| civilization is reasonably advanced.
| m3kw9 wrote:
| Imagine meeting one of these planets while travelling in space,
| the entire planet all dark and you are ordered to investigate.
| escapecharacter wrote:
| https://en.wikipedia.org/wiki/Blindsight_(Watts_novel)
| rusanu wrote:
| also https://en.wikipedia.org/wiki/Dragon%27s_Egg
| astrange wrote:
| https://en.wikipedia.org/wiki/Flatlander_(short_story)
| actually_a_dog wrote:
| Also https://www.imdb.com/title/tt0572231/ ( _Star Trek:
| Enterprise_ , "Rogue Planet")
| krisoft wrote:
| Sounds spooky, but when I try to imagine it my mind throws an
| exception: In any non-imaginary scenairo you wont have enough
| energy and reaction mass to match speed with the object. in
| these scenarios "ordered to investigate" means that you will do
| some neat observations as you and the object drifts by. And if
| you have somehow enough energy to match the planet's speed then
| you are basically a god and you don't really have much which
| can spook you.
|
| While the story of squishy human meatsacks traveling in a tin-
| can braving the surface of one of these would be a compelling
| read it is not really realistic sadly.
| dwighttk wrote:
| Probably inadvertently click-bait title with "population"
| ambiguity
| hindsightbias wrote:
| If the planet isn't bound to a star and is behind the lensing
| object, what is illuminating the planet that it appears
| optically?
|
| Wouldn't be completely dark?
| goodcanadian wrote:
| The planet is the lensing object. It causes a background star
| to brighten slightly in a very characteristic way.
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