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Interstellar Hydrogen Prevents Light-Speed Travel? 546

Posted by CmdrTaco
from the einstein-brought-in-backup dept.
garg0yle writes "As if relativity wasn't enough to prevent us traveling at light speed, Professor William Edelstein of the Johns Hopkins University School of Medicine is now claiming that the interstellar hydrogen, compressed in front of the ship, would bring the journey to a shocking end. 'As the spaceship reached 99.999998 per cent of the speed of light, "hydrogen atoms would seem to reach a staggering 7 teraelectron volts," which for the crew "would be like standing in front of the Large Hadron Collider beam."'"
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Interstellar Hydrogen Prevents Light-Speed Travel?

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  • by jim_v2000 (818799) on Wednesday February 17, 2010 @12:35PM (#31170848)
    That's what the deflector array is for.
    • Re:Fuckin' Noobs (Score:5, Informative)

      by captaindomon (870655) on Wednesday February 17, 2010 @12:41PM (#31171002)
      Not to mention the Bussard Collectors.
      • by Rogerborg (306625)
        ...and how would you get to Ludicrous Speed without them?
      • Re:Fuckin' Noobs (Score:5, Informative)

        by rssrss (686344) on Wednesday February 17, 2010 @02:01PM (#31172636)

        The Bussard Collector is part of a Bussard Ramjet [wikipedia.org].

        The Bussard ramjet is a system of spacecraft propulsion proposed in 1960 by the physicist Robert W. Bussard. A moving spacecraft would use enormous electro-magnetic fields to collect and compress hydrogen from the interstellar medium. The hydrogen would be forced into a progressively constricted magnetic field, which would compress it until thermonuclear fusion occurs. The magnetic field would then direct the heated gas in the direction opposite to the intended direction of travel, thereby accelerating the vessel.

        More generally [wikipedia.org].

    • Re:Fuckin' Noobs (Score:5, Insightful)

      by Joce640k (829181) on Wednesday February 17, 2010 @12:55PM (#31171292) Homepage

      UM, I thought the plan was to scoop them up and use them for fuel, ie. you WANT those hydrogen atoms to pile up in front of the ship.

  • by verbalcontract (909922) on Wednesday February 17, 2010 @12:35PM (#31170858)

    And I was just about to get into my 99.999998% lightspeed spaceship.

    • by pla (258480) on Wednesday February 17, 2010 @01:48PM (#31172364) Journal
      And I was just about to get into my 99.999998% lightspeed spaceship.

      Aside from the current nonexistence of such a craft, that really does count as the faulty premise with Edelstein's conclusion...

      Why would you go that fast (presuming you can't go much faster, of course)? It takes exponentially more energy to accelerate as you approach the speed of light, but that doesn't get you to your destination all that much faster. At a mere 99.9% of the speed of light, you spend less than one extra hour of travel (externally measured, of course) per month. For a "realistic" trip to nearby stars, that means an extra day and a half out of the 4.37 years to get to Alpha Centauri.

      For relatively local trips, the difference amounts to a triviality - And longer trips simply will never happen unless we have some breakthrough that makes Star-Trek-like warp engines a reality.
      • by Fnkmaster (89084) on Wednesday February 17, 2010 @02:27PM (#31173174)

        Well, the only material difference is the time dilation factor for the person in the spaceship. At 99.9% the speed of light, that factor is about 22 - i.e. the 4.4 years seems to take only about 0.2 years, or 10 weeks. At 99.999998% of the speed of light, it is almost exactly 5000 - which means the trip would seem to pass in about 7 hours. This is ignoring the general relativistic effects of acceleration and deceleration.

        So, it's a material difference to the person traveling, but not so material to the observer stationary relative to Alpha Centauri.

      • by dmartin (235398) on Wednesday February 17, 2010 @02:35PM (#31173304)

        It really depends on what you think is relevant. For example if the purpose is to do research for people on Earth, you probably are interested (at least in part) in the time taken for the round trip, and how long people on Earth have to wait to see the benefits of their investment. If you are looking at colonization then you are probably more interested in the amount of time as experienced by the people travelling on the ship. In this case the difference between 99.9% of the speed of light, and 99.99% of the speed of light is significant.

        To make the example concrete, let us take your example of Alpha Centuri:
        Distance: ~ 4 light-years.

        • 99.9% of the speed of light:
          Time (Earth observer): 4 years and 1.5 days
          Gamma factor*: 22.4
          Time (Ship observer): 65 days
        • 99.99% of the speed of light:
          Time (Earth observer): 4 years and part of a day.
          Gamma factor*: 70.7
          Time (Ship observer): 20.5 days.

        So from the point of view of the *crew* the journey takes about a third the time, although from Earth you are correct in stating they are essentially the same.

        * The gamma factor, or time dilation factor (or length contraction factor), is given by special relativity. If you speed is v and the speed of light is c then
        Gamma factor = 1/sqrt(1-(v/c)^2)

        • Re: (Score:3, Insightful)

          by Grishnakh (216268)

          Yep, round-trip time from Earth is important. One-way time is only important if 1) you don't plan on returning home, and 2) you actually know where you're going. Without sending probes or whatever to various star systems, and getting data back from them showing what's there, then any one-way colonization ship isn't going to have a viable destination. It would spend way too much time jumping from star to star until you find something suitable.

      • Re: (Score:3, Informative)

        by Angst Badger (8636)

        For relatively local trips, the difference amounts to a triviality

        For relatively local trips, especially considering that you have to spend half the trip turned around and decelerating, there's going to be a point well before nine-tenths of C that the cost of further acceleration vastly outweighs the value of getting to the destination faster. Without knowing what the cost of energy is going to be if and when we can build propulsion systems capable of relativistic travel, I couldn't say where the point of diminishing returns would be, but for in-system travel, I'd be will

      • by microbox (704317) on Wednesday February 17, 2010 @03:39PM (#31174434)
        Actually you are missing something very important in your maths: relativity. It doesn't take much shorter to get to the destination from the perspective of someone on earth, but the tale is different for the people on the spaceship. The distance to the destination shrinks.

        Sagan talks about this in Cosmos. If a theoretical spaceship accelerated constantly, it could traverse the entire universe in a mere 50 years -- but by the time it returned earth would be long gone.

        Conceptually -- the universe has no "size" for a photon in a perfect vacuum. From the point of view of this theoretical photon, it is created in a distant star and intersects with your eye instantaneously. From our point of view it could take millions of years.

        Considering that mass is what prevents light-speed travel (as well as the density of the medium being travelled through), that implies an interesting relationship between space-time and the higgs boson.

        The universe is stranger than any fiction.
  • by Space cowboy (13680) * on Wednesday February 17, 2010 @12:35PM (#31170862) Journal
    After reading the article (yeah, I know...) tow thought spring to mind...

    1) Warp drive doesn't posit a traditional "go-very-fast-through-normal-space" type of spacecraft engine - it warps[*] space-time (hence the name!) in front of and behind the spacecraft - see here [wikipedia.org] for an explanation. The spacecraft itself is sitting in a bubble of normal space, possibly even at rest.

    2) Um, ramjets [wikipedia.org], anyone ?

    Seriously, any number of sci-fi authors have covered this problem in enormous detail over the last few decades

    Simon

    [*] And because this is /., I expect you all to forgive me for using the present tense here [grin]
    • by jgtg32a (1173373) on Wednesday February 17, 2010 @12:44PM (#31171062)

      You did not just link me to a astrophysics article of wiki that's worse than tv tropes for me
       
      I'm at 8 articles from just the first link you provided.

    • If this 'warp' were applied to one mass, hydrogen, then it should apply to anything in space -- nebulae, planets, suns, black holes. Most science fiction doesn't go that far. I suspect there are exceptions.
      • Re: (Score:3, Insightful)

        IANAP, but I believe the idea is that empty space require less energy to 'warp', and that a few disparate atoms and molecules don't significantly change that energy requirement (which albeit is still huge). However, when you fill space with a lot of mass, and mass is energy, it presents a 'resistance' to warping that drives energy costs up to accomplish the goal. Such is my understanding of science-fiction FTL physics. ;-p
    • Yes, and if I have the magic ring I can disappear too!
    • by DerekLyons (302214) <fairwater AT gmail DOT com> on Wednesday February 17, 2010 @01:04PM (#31171500) Homepage

      Seriously, any number of sci-fi authors have covered this problem in enormous detail over the last few decades

      Yes, any number of sci-fi authors have handwaved around these problems for the last few years. Actual scientists, not so much. And, as with TFA, the conclusions of the ones that have been less than sanguine. (From the POV of actually doing it.)

      • Re: (Score:3, Interesting)

        Seriously, any number of sci-fi authors have covered this problem in enormous detail over the last few decades

        Yes, any number of sci-fi authors have handwaved around these problems for the last few years. Actual scientists, not so much. And, as with TFA, the conclusions of the ones that have been less than sanguine. (From the POV of actually doing it.)

        Robert W. Bussard (August 11, 1928 – October 6, 2007) was an American physicist who worked primarily in nuclear fusion energy research. He was the recipient of the Schreiber-Spence Achievement Award for STAIF-2004.[1] He was also a fellow of the International Academy of Astronautics.

        See also, Bussard ramjet http://en.wikipedia.org/wiki/Bussard_ramjet [wikipedia.org]

        Without a ramjet, you'd probably run out of fuel before reaching 99.999998 per cent of the speed of light.

        • by DerekLyons (302214) <fairwater AT gmail DOT com> on Wednesday February 17, 2010 @01:30PM (#31172022) Homepage

          And if you actually read the Wikipedia article you link to, rather than just drooling over the qualifications of the inventor, you'll find that as people have actually began to seriously study it - there are now significant doubts as to how well it will work. (Even assuming we figure out how to do the parts Bussard handwaved into existence, like the magnetic scoop.) In addition, even if it does work, it may be subject to the problems outlined in TFA.

      • Re: (Score:3, Funny)

        We could just build the spaceships out of inside-out LHC tunnels!
  • by Hognoxious (631665) on Wednesday February 17, 2010 @12:36PM (#31170872) Homepage Journal

    Let's just hope the engine controls aren't made by Toyota, or it'll be hitting that speed whether the crew want or not.

  • Just engage the Edelstein compensators.

    Come to think of it, this professor is probably hoping to have some scifi tech named for him.

    • by jgtg32a (1173373)

      I thought that they just called it navigation shielding, originally they just talked about it to protect against asteroids, but looks like they would be far more useful against hydrogen.

  • by notgm (1069012) on Wednesday February 17, 2010 @12:36PM (#31170882)

    put a hydrogen-atom-splitter on the bow of the ship, they'll just get cut in half and fall out of the way.

  • LHC (Score:4, Funny)

    by mcgrew (92797) * on Wednesday February 17, 2010 @12:36PM (#31170884) Homepage Journal

    "hydrogen atoms would seem to reach a staggering 7 teraelectron volts," which for the crew "would be like standing in front of the Large Hadron Collider beam."

    Wow, free energy!

  • Oh noes (Score:4, Funny)

    by gparent (1242548) on Wednesday February 17, 2010 @12:36PM (#31170896)
    Guess we'll just have to go at 99.999997% of the speed of light then.
  • If you want to travel light speeds, you have to convert yourself into light first.

  • by Salgak1 (20136) <salgak@s[ ]keasy.net ['pea' in gap]> on Wednesday February 17, 2010 @12:38PM (#31170924) Homepage
    . . .to GET to .99999998 c, this is unlikely to be a concern. And if you have the effectively-infinite energy to move a ship at this speed, providing sufficient shielding should be a trivial exercise in additional hand-wavium. . . .
    • by Yvanhoe (564877)
      ...or one could slow down at 0.999 c and the trip is going to be two minutes longer.
      • Re: (Score:3, Funny)

        by Anonymous Coward

        Well to you it might be only 2 minutes, but at the destination you will be 5.67 days late and will probably miss your connecting flight.

    • by delt0r (999393) on Wednesday February 17, 2010 @01:12PM (#31171632)
      Some numbers! If the ship is just 100kg with cargo, then you need 6.36e22 J to get to .99999998c assuming 100% efficiency. About 1.4e21 J hits earth everyday from the sun. So a earth sized solar panel will collected the energy required in about 4 and half days. All assuming no energy losses.
  • "Hydrogen atoms are unavoidable space mines."

    Uhh.. Hey, Mr. Scientist... Ever hear of deflector shields? GOSH!

    Going out on a (geeky) limb... Don't warp drives (again, geek-out time, so just accept they exist a la Star Trek) make a bubble that the ship moves through that goes faster than light, instead of accelerating the ship up to and beyond light speed? I believe I've read that Einstein's theories technically allow for something moving faster than light, if that something can manage to alter their local space-time?

  • Spacetime is curved, so even if the ship is traveling at 15mph, it reaches its destination in a time indicating FTL travel. The actual distance traveled is much shorter, though.

    This is the stuff you should already know before you apply to Starfleet.

  • So use a ramscoop to collect all the hydrogen that's in the way and use it for fuel. Sheesh.

  • by nomadic (141991) <nomadicworld@@@gmail...com> on Wednesday February 17, 2010 @12:40PM (#31170962) Homepage
    All you have to do is navigate around the hydrogen atoms.
  • by wintermute3 (191382) on Wednesday February 17, 2010 @12:41PM (#31171004)

    I don't think anyone seriously contemplating relativistic or FTL travel expects to be physically accelerated to such speeds. After all, if stationary interstellar hydrogen is effectively hitting you at teravolt levels, it means that every particle in your body (and the ship) has actually been accelerated to velocities equivalent to the particles in the LHC beam. Not bloody likely. We need warp drive, subspace, wormholes, or something else to solve the problem, not ridiculous conventional acceleration.

    - Michael

  • by Vinegar Joe (998110) on Wednesday February 17, 2010 @12:43PM (#31171036)

    I'll bet that would sting.

  • Interesting - what WOULD happen if you stood in front of the Large Hadron Collider beam? Does it cut/burn like a laser, or something else? Just wondrin'...

  • by CrimsonAvenger (580665) on Wednesday February 17, 2010 @12:49PM (#31171170)

    So, what he's saying is that the interstellar hydrogen density will limit us to no more than about 9600 light years nonstop at a continuous 1g acceleration/deceleration.

    Given that even a matter/antimatter conversion drive would require about 116,000,000 tons of reaction mass (half antimatter) for every ton of payload, it would seem that we're going to be hitting a great many limits long before this particular limit begins to be meaningful.

  • AFAIK Luke, Han and friends did not collide with some giant Hydrogen ollider.
    They just nearly collide with a giant artificial moon.

  • According to the theories developed by Tessa Wendel, once you are traveling faster than the speed of light the nature of gravity changes from attraction to repulsion. This means that a spaceship traveling that fast would be effectively shielded from small objects by the gravitational force.
  • This is, of course, impossible - which is why the advertising executives of the star system of Bastablon came up with this slogan: "If you've done six impossible things this morning, why not round it off with breakfast at Milliways, the Restaurant at the End of the Universe?"
  • through the medium of interstellar space.

    I'm pretty sure I can't travel at 30,000 mph through the ocean either. Through space, not as big a problem.

    Most SF geeks would agree that if we're ever going to exceed C, we won't be doing it in meatspace.

  • The protons in the LHC are a little closer together than those in interstellar space. Density in interstellar space is about 1 atom per cubic centimeter. I can't readily find a number for the cross-sectional area of the LHC beam, but it is surely less than 1 cm^2 and each ring has 2835 x 10^11 protons over its 27 km length -- or better than 10^8 protons per cubic centimeter.

    So no, it's not quite like standing in front of the beam from the LHC, not by a factor of a hundred million.

  • I guess that we're just lucky that Earth is moving at roughly the same speed as those hydrogen atoms.

  • Wouldn't the hydrogen exist in ionized forms, and thus be possible to divert by electric fields? A 99.999% spaceship would probably have enough of an energy supply to power the LHC a few times over and thus be able to shield the significant part of the craft from any LHC strenght radiation?
  • by Al Al Cool J (234559) on Wednesday February 17, 2010 @01:01PM (#31171440)

    What does this guy know about space travel? He's a prof at a medical school, FFS. This is rocket science, not brain surgery!

  • We don't need 99.99999% of the speed of light. We need FTL (Faster Than Light), for before 2012 please !
  • Economics (Score:5, Insightful)

    by TrumpetPower! (190615) <ben@trumpetpower.com> on Wednesday February 17, 2010 @01:05PM (#31171512) Homepage

    Interstellar travel is fundamentally an economic paradox — ignoring, of course, such fantasies as Warp drives.

    Sending a Shuttle-sized craft to Alpha Centauri in a matter of years would require roughly the current total energy consumption of humanity.

    Only when our civilization advances to the point that we harness a significant portion of the Sun’s total energy output would the energy budget for interstellar travel approximate the same proportion of the energy budget we spend today on interplanetary missions.

    One can suggest “sleeper ships,” but building mechanical devices that will survive thousands of years is as hard a problem as throwing them across light years of distance. Any gas will leak out of any container in such a timeframe, and no plastic or rubber seal would last a fraction of the time necessary. The next thought is to provide power to the ship during the long journey, but you need as much total energy as for getting there fast — and, if you can comfortably survive for millennia in interstellar space, why even bother with stars in the first place?

    Oh — and the Fermi Paradox applies especially well. Assume that it takes even ten thousand years to colonize a remote solar system, and the entire galaxy would have been overrun by now if a colonizing civilization had started in the terrestrial Jurassic period.

    Interstellar travel makes for great space opera, but it has no more bearing on reality than unicorns and dragons.

    Cheers,

    b&

  • my proposition (Score:3, Interesting)

    by corbettw (214229) <`moc.oohay' `ta' `wttebroc'> on Wednesday February 17, 2010 @01:24PM (#31171924) Journal

    There's an old saying, nothing focuses the mind like a firing squad. When faced with imminent death, humans are famously adept at coming up with novel solutions to complex problems. To that end, I propose we gather a collection of prominent physicists and place them in a ship capable of accelerating to near-light speed over a period of some years. Put locks on the controls so that they are unable to halt or alter the acceleration, then inform they have X years to come up with a way to avoid being smashed to death by interstellar gasses. Either they come up with a solution and are all saved, or they perish in a fiery ball of glory. Either way, they'll probably all have high schools named after them.

  • http://science.slashdot.org/comments.pl?sid=177080&cid=14696574 [slashdot.org]

    The density of interstellar space is about one atom per cubic centimeter [hypertextbook.com]. If the spaceship were going near the speed of light (3 x 10^10 cm/sec), it would be hit by 3 x 10^10 relativistic particles per cm^2/sec. This is about the equivalent of one Curie [wikipedia.org] per cm^2, which would kill a human and cripple any electronics on board

    A very heavy magnet could deflect the protons, but the neutral atoms would be unaffected by the magnetic field.

  • TSA (Score:3, Funny)

    by WPIDalamar (122110) on Wednesday February 17, 2010 @03:21PM (#31174122) Homepage

    The real reason interstellar travel will never happen is the time in the security line with TSA would approach infinity for that sort of trip.

  • by Tetsujin (103070) on Wednesday February 17, 2010 @03:40PM (#31174446) Homepage Journal

    One of those classic complaints against popular sci-fi is that the ships are always pretty and "aerodynamic" (well, mostly, anyway) and that there's no need for this in a vacuum... Well, there you go, one good reason to have aerodynamic space ships. :)

    Making spaceships sleek was a key part of making them fast in the Lensman books for more or less the same reason. (Smith's goofy FTL drive idea negated the mass of the ship, allowing the ship to instantly accelerate to a speed where thrust equaled drag)

  • by Werrismys (764601) on Wednesday February 17, 2010 @06:29PM (#31177224)
    Lasers in front to plasmatize the hydrogen, huge magnetic fields to move the plasma to the REAR of the ship, where a "virtual" burn chamber (really just magnetic fields) captures the plasma. Another mag field keeps the antimatter from touching anything, and gradually releases anti-atoms to the furnace. BOOM mega boost. Easy to shield mere energies if you can do all that trickery with fields. Certainly possible - just very, very hard.

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