[HN Gopher] How a mysterious star could help the search for extr...
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How a mysterious star could help the search for extraterrestrial
life
Author : rustoo
Score : 39 points
Date : 2024-04-27 11:16 UTC (11 hours ago)
(HTM) web link (www.theguardian.com)
(TXT) w3m dump (www.theguardian.com)
| bloopernova wrote:
| In this specific instance:
|
| _The idea that astronomers had stumbled on such a structure
| triggered headlines round the globe - though not for long.
| Subsequent research has now undermined the idea. "We have found
| that light of different wavelengths is blocked in different
| amounts: exactly what you would expect from starlight passing
| through a dust cloud," said Lintott._
| imglorp wrote:
| It's not just some dust There's no way it's just some
| dust It was just some dust
| pfdietz wrote:
| I mean, if alien species could build star-spanning
| structures, they could easily do interstellar travel and
| colonization. So the Fermi argument says this couldn't
| actually have been aliens -- someone would have turned the
| Milky Way into a completely colonized urban area billions of
| years ago. All the other galaxies would have been colonized
| too (IR observations say < 1 in 100,000 have been urbanized.)
|
| I think people are misled by all the SF stories with galactic
| empires that somehow left Earth alone for billions of years,
| not realizing stories are there to entertain, not reflect
| what could be real.
| jvanderbot wrote:
| That's not clear actually. We could, given a religious like
| motivation, build massive space stations right now with
| today's rockets, materials, and lifetimes. It's incremental
| building.
|
| We could not get to the nearest star with today's rockets
| (or eq.), materials, or lifetimes. There's no incremental
| engineering there.
| pfdietz wrote:
| The star is just 1470 light years from our solar system.
| So, either a huge coincidence occurred, or there are many
| stars like this in the Milky Way. In the latter case, you
| are proposing that every one of the alien civilizations
| that built each of these things had the same motivational
| inhibition to colonization. Even more, you are proposing
| that all such civilizations in the past, and all such
| civilizations in other galaxies, were similarly
| inhibited.
|
| A star-spanning civilization would have far more than
| enough energy to propel interstellar vehicles, for
| example by laser beaming.
| jvanderbot wrote:
| I'm proposing no such thing. GP said that _if_ they had
| built large structures _then_ it was obvious they could
| do interstellar travel.
|
| I said that implication was false, it's clear how we
| might build large orbital structures but not clear how we
| might to interstellar travel. As a counter example.
| pfdietz wrote:
| The implication is as clearly true as such things could
| be.
|
| The barrier to interstellar travel is largely
| economic(*). The resources needed to construct star-
| spanning structures are many orders of magnitude greater
| than needed to construct and launch a starship (or a
| laser with an aperture capable of projecting a beam to
| interstellar distances).
|
| (*) https://galileo.phys.virginia.edu/classes/109.jvn.spr
| ing00/n...
| jcranmer wrote:
| One of the problems with this stuff is most of the
| problems are analyzed by physicists, who tend to reduce
| the problem to "can we make the physics work" rather than
| looking at more practical problems like "do we know if
| any materials will stand up to getting front-row seats to
| nuclear explosions?" and the other kinds of engineering
| problems that have bedeviled rocket science in its entire
| existence. And that's before getting into more
| fundamental issues like "what is the effect of space life
| on human biology?" (to which the answer appears to be
| somewhere between "maybe unmitigatably harmful" to
| "catastrophic").
|
| There's a lot of questions that need to be answered
| before we can truly answer the question "what does it
| take to make interstellar travel", and the fact that many
| boosters for space exploration are glibly ignoring those
| questions is perhaps the biggest barrier of all.
| Nevermark wrote:
| We are getting close to fusion with magnetic containment.
| So at some point, regular materials won't be a limit
|
| But materials are improving at a rapid pace. So many
| orders of scale to co-optimize meta materials. Materials
| in the future will be magic compared to the limits we
| have now.
|
| Materials won't be a barrier to interstellar travel
|
| We are only decades away from being able to do it, for
| very low mass ships/probes with AI. Long before we will
| be able to create mega structures
| dotnet00 wrote:
| The technologies within our reach which would be very
| helpful with building massive space stations are such
| that they would very much allow for getting to the
| nearest star within a human lifetime.
|
| The only reason we don't actually reach out for those
| technologies right now is that many of us have a
| religious fear of anything nuclear.
| pfdietz wrote:
| Nuclear energy isn't needed for interstellar travel.
| Beamed propulsion would likely be faster.
| dotnet00 wrote:
| Beamed propulsion is a farther out technology, requiring
| development of more powerful lasers capable of pushing a
| crewed vehicle in reasonable amounts of time and has the
| issue that it is difficult to slow down at the
| destination.
|
| Nuclear rocket engines were already being developed
| during the cold war.
|
| Both suffer from the irrationality that the more useful
| they are capable of being, the more they can be
| misconstrued as orbital weapons.
| pfdietz wrote:
| I am amused you are objecting to a technology for
| interstellar travel on the grounds it is "farther out",
| especially in the context of what hypothetical aliens
| that are around for millions or billions of years would
| be using.
|
| We could build a 1% c starship using hydrogen bombs. But
| it wouldn't make much sense to build it, since in the
| time it would take to get to even the nearest star we'd
| likely have something much faster.
| dotnet00 wrote:
| I'm not objecting to it, my initial post was trying to
| emphasize the closeness of technologies capable of
| reaching the nearest stars, lasers are an option, but imo
| nuclear propulsion is "closer" in terms of time taken to
| achieve the energy densities needed to take humans there.
|
| Sure it's only a difference of a couple of decades at
| worst between the two but in the context of a human
| lifetime, that's significant.
| Nevermark wrote:
| In what important sense is nuclear closer?
|
| If we sent a nuclear craft today, a future laser or other
| propulsion craft will still get there much sooner.
|
| Worse, we don't actually have a nuclear craft design. By
| the time we worked out a design and built it, the other
| tech will already be ready.
|
| That is because other tech will require less mass, which
| will "massively" simplify and reduce cost of the venture.
|
| Given the time the trip will take, it will actually be
| decades at least, before the optimal time to design and
| send a ship - even if we had an unlimited budget with the
| only objective of getting there the soonest we can
| jvanderbot wrote:
| This just isn't true. It seems true, because we can treat
| interstellar travel as a problem of scale, but it doesn't
| follow that "build big rocket" equates to "go fast and go
| safe".
|
| The energetics of interstellar dust, radiation, the long
| timelines of travel. It's not clear at all.
| 0-_-0 wrote:
| Oh we absolutely could, we could have done it with 1960s
| technology in fact: https://en.m.wikipedia.org/wiki/Proje
| ct_Orion_(nuclear_propu...
| jvanderbot wrote:
| The propulsion may have been theorized to get us up to
| speed, but there are many other factors, not least of
| which is shielding from objects while you're going a
| decent fraction of the speed of light. There's no
| obstacle avoidance routines with that much momentum.
| pfdietz wrote:
| At 1% of the speed of light, the energy of a proton is 47
| keV. This is trivially easy to shield against. The energy
| of an electron is just 26 eV.
|
| One would need to shield against galactic cosmic
| radiation, but this really isn't much more of a problem
| than shielding a vehicle in the solar system.
| ThalesX wrote:
| What about a micrometeoroid?
| pfdietz wrote:
| The risk with these if they are sufficiently large would
| be an explosion on impact. This is dealt with by placing
| a thin barrier in front of the vehicle. The particle
| explodes on impact with the barrier, cutting a small
| hole. The debris shoots forward, spreading, and is
| absorbed on a shield. At 0.01 c, a 1 microgram particle
| deposits 450 joules of energy.
|
| If necessary, parts of this system could be replaced
| during the journey.
| fnordpiglet wrote:
| This line of logic doesn't hold.
|
| Star spanning structures requires the ability to move mass
| at scale which requires enormous but diffused in time and
| space amounts of controlled energy.
|
| Moving between stars requires immense energy focused on a
| single thing. The amount of acceleration required to any
| meaningful mass to speed necessary to travel between stars
| and maintain a coherent civilization is extraordinary and
| implies many things about the mass being accelerated as
| well. Most things would simply be crushed instantly,
| including any organism. The speed of light is also a major
| impediment as is time dilation, as is the need to
| decelerate, which require equal and opposite energy away
| from the destination. Ok - accelerate with large lasers
| based at home - how do you then stop? You first need to
| build large lasers both at home and destination. The
| problems expand, and this only helps for very local travel
| between close stars.
|
| It's difficult but plausible with today's technology scales
| up to build star spanning structures because they're built
| incrementally and the need for near light speed travel
| doesn't exist. Further the existence of a star spanning
| structure might enable interstellar travel, but not
| intergalactic.
|
| I'd also note that SF is meant to entertain with a story
| that is possible given some assumptions of progress or
| hidden nature of reality or small modifications to what is.
| It's not meant to be built on magic and other absurdities
| (not meant as a pejorative!). Many science fiction stories
| become true and many more will. Often science fiction
| inspires us to achieve what doesn't exist today but could.
| To couch it in something that's dismissible as say Gandalf
| the Wizard fighting a Balrog is to greatly underestimate
| what science fiction is. It's a roadmap to the future that
| helps us understand what to avoid on the road.
| pfdietz wrote:
| Building a starship reaching 1% of the speed of light
| seems quite reasonable without substantial technological
| advance (Dyson's 1968 H-bomb propelled Orion). What it
| would need would be lots of deuterium, but that's just a
| matter of large scale industry, which this putative
| civilization would have.
|
| If you are saying this civilization does its work over
| very extended periods of time, you're saying they're
| comfortable with efforts that take centuries or millenia
| or even longer. That alone makes interstellar travel and
| colonization much easier; the energy needed scales as the
| inverse square of the travel time (assuming Isp optimized
| for the travel time chosen and assuming non-relativistic
| travel).
|
| We (or they) _do not need_ close to light speed travel
| for interstellar colonization.
| HarHarVeryFunny wrote:
| Typical distance between any two stars in the Milky Way
| is 5 light years, which at 1% speed of light would take
| 500 years to get there. Assuming 25 years per generation,
| that represents a travel time of 20 human generations.
|
| That's like a family from the 1500's committing for their
| children and 19 following generations to live on a shitty
| rocket. They'd have just arrived.
|
| I wonder what 500 years of food, water, and oxygen looks
| like for a civilization-founding crew. What's the backup
| plan if the target planet isn't livable? Cyanide tablets?
| pfdietz wrote:
| Colonization wouldn't be aimed at planets, it would be
| aimed at structures in space. You know, like we're
| assuming this star-spanning civilization has been
| building in astronomical numbers?
|
| Food and air would be manufactured during the trip. All
| that's needed is a source of energy. At 1% c, that
| probably means a nuclear source (or beamed power), but at
| higher speeds they could simply exploit the energy being
| deposited by interstellar matter. At 1 proton/cm^3 and .1
| c, the power is 22 W/m^2.
| HarHarVeryFunny wrote:
| If we're talking inter-stellar travel then it doesn't
| seem to matter what the destination is (planet or space
| habitat). The travel time remains the same, and the only
| source of materials (incl. food etc) would be what you
| bring with you until you arrive at a planet (i.e. at
| nearest star that has a planet that has useful
| resources).
|
| Even if this were a robotic terraforming mission, it's
| hard to see humans committing to the expense of such an
| endeavor with no payoff for generations to come. Heck,
| we're reluctant to act to save the planet our lives
| depend on right now.
| pfdietz wrote:
| If we're talking about a species that has exploited the
| resources of its star system, and done so at a scale that
| includes noticeably blocking the light from its star,
| then said economy has billions of times the energy we're
| currently consuming. Proportionally, the cost of an
| interstellar spacecraft would be less than one week of
| your salary.
| bilsbie wrote:
| It's not advanced alien technology because it doesn't work like
| advanced alien technology.
| bayouborne wrote:
| It's not advanced alien technology because it doesn't work
| like our concept of advanced alien technology.
| roywiggins wrote:
| The Moon isn't a space station because it doesn't look like
| our concept of a space station.
|
| More likely it's just the Moon than an advance alien space
| station though.
| jajko wrote:
| From wikipedia: It has been suggested that it is an alien
| megastructure, but evidence tends to discount this suggestion
|
| Just read wiki on the topic seems to be the best idea these days,
| much less pompous and no fabulation unlike the article. It also
| has distant red dwarf companion, of course no mention of this at
| all in the article.
|
| Not sure why guardian needs to chase sensationalism, I guess view
| count trumps all other metrics.
|
| Also, haven't heard any rational objections for Dark forest
| theory, any sufficiently advanced civilization to build this
| would be tremendously stupid to expose themselves to whole Milky
| way and few surrounding galaxies.
| bilsbie wrote:
| Ducks: "evidence suggest duck blinds are just reeds"
|
| Which is a fun way to say the rules for evidence change a bit
| when what you're studying could be actively deceiving you and
| is smarter than you.
|
| How do the rules change? No idea.
| Nevermark wrote:
| The big weakness of the Dark Forest scenario, is that if the
| galaxy was a dangerous place, it would already have been
| defensively/offensively explored.
|
| There wouldn't be a star system with primitives like us that
| wasn't identified many millions of years ago.
|
| But for credible scenarios, your "too much smarter than us to
| predict" principle is a good one.
|
| "They went into another dimension" for instance, seems
| fantastical. But we have no idea what millions of years of
| science and technology will allow.
|
| For all we know, the re-acceleration of dark energy is the
| side effect of successive new civilizations harnessing the
| fine structure of space-time creating their own private
| megaverses.
| bilsbie wrote:
| Do you pick apple blossoms or do you wait for the apples?
| jajko wrote:
| If you mean that they are tricking anybody, that doesn't
| follow. We are already curious, and we are literally infants
| doing first baby steps and TBH we are still pretty much
| clueless about things like how universe works via single set
| of principles, how many dimensions are there and so on. Can't
| get even to nearest star in reasonable time. You don't hide
| yourself by doing something so far unique and extremely
| visible in cca whole galaxy and even beyond.
|
| The real threat to such 'builders' would be much more
| advanced civ than us that can clearly see and understand what
| they see.
|
| 'What if' can be a nice mental game if you let your
| imagination loose in right direction, but its just a game and
| this one doesn't stand on any solid facts, so lets treat it
| as such.
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