back to article Pulsars: the GPS beacons of the cosmos

Want to navigate over huge distances with nearly superhuman accuracy? All you need is a laptop, the right software, and some way to keep track of the signals of distant pulsars. What began as an attempt to improve the search for gravitational waves has had the unexpected secondary outcome of demonstrating that pulsars could …

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  1. jake Silver badge

    See: the Lensman series, by E.E "Doc" Smith, from 1948.

    Bad pulp fiction, but a few original ideas. I enjoyed reading it when I was in my early teens. Today, as a Grandfather? Maybe not so much ... But my nieces & nephews are having fun :-)

    1. Anonymous Coward
      Happy

      Re: See: the Lensman series, by E.E "Doc" Smith, from 1948.

      First read the series back in 1960s. Found them tucked away in a box a decade ago and read them again.

      I still enjoyed them.

  2. dssf

    Maybe Crewman Daniels was shot backwards in time again?

    Section 31, aka the NSA in current/old Earth 2013, will be setting temporal sslapp/sstymyy/zzapp coordinates for XP Deng. If he gets too close to threatening the Temporal Commission, XP will be "x'd" out, and his zeal in name Deng will be rewarded with a resounding (pulsars warbles and stellar nursery dazzling flashes) dong.

    Kudos for the discovery, but don't let Admiral/Crewman Braxton come after you! He almost eradicated Janeway, were it not for some help by 7 of mine, umm, 9.

    Seriously, thought, imagine if his/their discovery leads to finding a wormhole or "subspace eddy" or or other equivalent in the STreknobabble. It might do wonders for humanity if funding is directed to feeding probes of various sizes and signal strength into to find our where it ends up, or how many places they end up. Imagine the sudden surge of human focus, redirection away from other Terran issues. Why, with wormholes we could cover vast distances...

    (SLAPPPPPPP)

    Ah, shit, wait, i was forced to awaken from the dream of a lifetime. WTF, do I see Talosians and their jelanium veins throbbing?

    1. Martin Budden

      Re: Maybe Crewman Daniels was shot backwards in time again?

      I had to double-check this was not amanfrommars1.

    2. Andrew Newstead

      Re: Maybe Crewman Daniels was shot backwards in time again?

      Funny you should mention Star Trek, in 1980 there was a "Star Trek Maps" set published which included a navigation booklet. This discussed using pulsars and quasars as triangulation beacons for navigation, quasars becourse these were so far away that they would appear "fixed" on the sky compared to pulsars which are nearer and so would have a detectable proper motion. The manual even gave the equations you could use to plot your position in space!

      My set are nicely tucked away in an envelope in my attic 8-)

  3. Anonymous Coward
    Anonymous Coward

    TEMP02?

    I don't think TEMPO2 is a good name for a software project. It is very easy for 'O' to be read as '0'.

    Some confusion may arise, resulting in unfortunate consequences.

    1. Anonymous Coward
      Holmes

      Re: TEMP02?

      Folding space to jump right into the center of a planet... or phase shifting into an asteroid. These problems have been predicted, and will be "corrected" by our time police...

      (Holmes, for more fictional references, but alas, not space)

  4. mIRCat
    Alien

    Long distance calling not included.

    When can I expect this to be an included feature on my smartphone?

    1. Rukario
      Go

      Re: Long distance calling not included.

      It just requires a quick adjustment with a sonic screwdriver.

  5. Anomalous Cowshed

    And so, to the stars...

    "The time had come. We were gathered on the hill, shivering in the cold, but beside ourselves with excitement. And then it happened. There was a dull roar and a shaking of the ground. The first ship rose up into the dark and starry sky, in a deafening din, trailing a plume of fire. It was a magnificent machine, the outcome of years of invention and engineering. Now the universe would have to take note, for mankind had laid a wager. We were bidding to fulfil our destiny. This slither of silver cutting its way across the void, was our greatest gambit. The first affirmation of our presence. Of our coming of age."

    1. Ugotta B. Kiddingme

      Re: And so, to the stars...

      that sounds vaguely familiar, as if from a classic novel. From whence cometh such a quote?

      1. GBE

        Re: And so, to the stars...

        If that's not the title of a book, it sure ought to be.

      2. Anomalous Cowshed

        Re: And so, to the stars...

        Off the cuff, straight from the cowshed!

        1. Anomalous Cowshed

          Re: And so, to the stars...

          I can continue the story by popular request.

          1. Martin Budden
            Go

            Re: And so, to the stars...

            Please continue!

            1. Anomalous Cowshed

              Re: And so, to the stars...

              The time had come. We were gathered on the hill, shivering in the cold, but beside ourselves with excitement. And then it happened. There was a dull roar and a shaking of the ground. The first ship rose up into the dark and starry sky, in a deafening din, trailing a plume of fire. It was a magnificent machine, the outcome of years of invention and engineering. Now the universe would have to take note, for mankind had laid a wager. We were bidding to fulfil our destiny. This slither of silver cutting its way across the void, was our greatest gambit. The first affirmation of our presence. Of our coming of age.

              We stayed up for hours after it had vanished into the blackness of space, gazing up at this new frontier that we somehow knew had now been breached and would forever be a part of us. Then we walked back to the warmth of our homes, pondering the momentous event we had just witnessed.

              As those it left behind slept in the cosy fastness of their homes, the ship hurtled across the void, its Varyan shields deflecting anything that might obstruct its path and would otherwise spell its doom. The great streaks of fire that spewed out of the engines had by now abated and in their place came an eerie bluish haze, a device designed to accelerate the ship to unimaginable speeds without any perceptible sound or vibration. It looked and felt as though it were suspended motionless in the vast infinity of space – though in reality it was moving at immense velocity.

              It was while conducting research into innovative ways of shielding spaceships travelling between the planets of the solar system, that the Space Foundation’s scientists had discovered that the shields they had developed had an unexpected side-effect. Because of the way in which they bent the fabric of space and time around the ship, in order to deflect the deadly solar radiation and the infinitely rare but dreaded space rocks, they enabled a spaceship to accelerate to speeds far in excess of what had been thought possible under conventional relativistic physics. The Ruycliffe effect, named after the late 22nd century mathematician who had first developed a model that could describe it, would set up a network of distortion streams between the vessel and nearby artefacts and deformations in the space-time continuum, which in turn formed a channel that bypassed conventional space-time. The result was a gradual and paradoxical lessening of the effects of mass as the vessel’s speed increased, thereby negating what had always been one of the most fundamental barriers to interstellar travel. A ship travelling within such shielding could thus not only journey immune from all known external hazards. It could also accelerate without limitation, and the more it accelerated, the more the impact of the acceleration grew, meaning that its speed would increase exponentially over time. To decelerate, the shields would merely have to be powered down, gradually – very gradually and very carefully.

              A series of probes had been sent out, as the engineers gradually adapted the technology to the unknown scope of this new effect. The first dozen or so had exploded in mid-flight; many more were lost when all contact with them was broken off, on account of having reached speeds and distances at which any control was impossible. However, over the years, the designs had been refined to the point where probes could be sent out, accelerated to speeds beyond that of light, and returned to Earth intact – though of course they could not be monitored or controlled during that part of their journey when they were being accelerated to extreme velocities. Finally, after extensive tests, a decision had been taken to send out a manned mission. And this was it.

              Onboard the ship was a crew of three picked men, the best and most experienced astronauts from the Space Academy. There was Linden, tall and muscular, an icy Nordic god, ever dependable, if slightly ponderous at times. Rante, a fiery southerner, easily crossed and quickly brought to the boil, but single-minded and dedicated to the task at hand. And Shand, the captain, who appeared forever lost in thought, mysterious and unfathomable.

              They did not pilot the ship – such a task would have been beyond their powers. The ship was controlled by banks of concealed computers which handled all its vital functions without as much as a single whisper or flashing indicator. Neither did the crew know their final destination. They had not been told it.

              At the Mission Control Centre, in the main control room, buried deep in the bowels of an enormous reinforced concrete building bristling with antennas, legions of stern men and women pored over huge screens, watching a white cross move in a slow but deliberate way across fields of complex symbols and lines. That was the ship, making its way past the markers that science had chosen to track its progress through the universe.

              First came the moon, and the sphere extrapolated from its orbit around the Earth. Then that derived from the asteroid belt. Then Mars, which had taken its toll over the years in failed expeditions to settle the planet. Then the outer planets, the gas giants that could harbour no life and had been left unexplored, save as a source of raw materials.

              Several hours had passed, and the cross on the huge screens was nearing the very limits of the control centre’s ability to track it. By now it was travelling at several hundred million miles per hour. Any direct contact was impossible. The only record of the ship’s existence was provided by the beacons and detectors that had been stationed for that purpose along the path plotted for the vessel.

              Then the cross vanished off screen, as the Control Centre’s computers struggled in vain to assemble any meaningful data to plot its position and path. Although this event had been anticipated, it drew gasps from those present in the hall, and the countless millions who were watching the proceedings over PlaNet from their homes.

              1. Martin Budden
                Thumb Up

                Re: And so, to the stars...

                Thankyou :-)

                p.s. you should trademark "PlaNet"

                1. Anomalous Cowshed

                  Re: And so, to the stars...

                  Re. PlaNet: I could copyright it and then sue anyone who used that word in speech or in print; I could even force kids and teachers in school to pay me 10 cents each time they said the word, and make use of an NSA commercial service now being trialled and soon to be known as "Universal Copyright Enforcement Service" to know exactly who had said it and when. I would make billions!

                  I am continuing with this story and will post another instalment soon, but work is slowing me down. If the comments for this article are closed, I will put it on www.graziella-greenwich.net/and so, to the stars

                  Thanks for your interest!

  6. Destroy All Monsters Silver badge

    an exploding galaxy for example

    I would like to see that. Structures 100'000 ly in diameter don't explode. Maybe we are talking about merging black holes?

    1. Pascal Monett Silver badge

      Black holes cannot explode. Merging black holes do not explode either - they just suck harder.

      I agree that galaxies cannot explode in the Cameron sense - however if you have ever seen those simulations of a galaxy going through another one, well let's just say that your statement can be found incorrect for certain values of explode.

      1. Fibbles

        Black holes don't suck.

        1. dssf
          Joke

          "Black holes don't suck" But, they WILL

          Blow you away with the awesome highly-localized compression and dialating crushingness.

          OTHO, black holes could turn out to be all touchy-feely, as in Multi-Endpoint Anuses of the Uniwerse Cosmically Upending Leading Physicists Assumptions (MEAU CULPA), hahahha...

          In THAT case, this WOULD be one "Fantastic Voyage" (in terms of the movie AND the song, jingling on a journey from one ass-end off the uniewers to the other. Iff that's so, then EVERYwhere in the uniwerse can be be equi-distributed ass-ends of the uniwerse, no better, no worse tan anyplace in the uniworse...

        2. Anomalous Cowshed

          "Black holes don't suck"

          Black holes suck big time, dude, if you're driving your space ship and one of them gets hold of you and won't let you achieve warp speed or whatever.

          1. JeffyPoooh
            Pint

            Re: "Black holes don't suck"

            You're in a black hole, the Universe.

            1. Vociferous

              Re: "Black holes don't suck"

              > You're in a black hole, the Universe.

              Only from the POV of people outside the observable universe, and frankly, screw those guys.

    2. NukEvil
      Mushroom

      "Structures 100'000 ly in diameter don't explode."

      They do in a Michael Bay movie.

      This comment also exploded--------------------------------->

  7. Michael H.F. Wilkinson
    Boffin

    Known and used (differently) in Pioneering days

    The Pioneer 10 and 11 space probes (1972 and 1973) each had a plaque indicating the position of earth relative to 14 pulsars, s the principle is well known

    1. Armando 123

      Re: Known and used (differently) in Pioneering days

      When the first pulsar was discovered, it was initially thought that it might be a signal beacon for space-traveling extraterrestrials.

  8. Michael Hoffmann

    Missing something?

    I might have to read the Arxiv article but from the Reg article it's not clear how this Galactic Positioning System would work once you move quite a ways out of the solar system.

    IIUC, Pulsars are not omni-directions, in that they have quite narrow beams out of their poles. Move "aside" a bit and you are no longer swept by the beams, making the pulsar effectively invisible.

    Other would "appear", of course, as you move around space, but how would map them into an all-encompassing galactic navigation chart?

    This may be just general knowledge for those familiar with mapping techniques, which I'm sadly not.

    1. Anonymous Coward
      Anonymous Coward

      Re: Missing something?

      Nice. point. I'll remember that if I reference it in any fiction. We need mapmakers and starmaps!

    2. Anonymous Coward
      Anonymous Coward

      Re: Missing something?

      Maybe start by locating intersecting beams? Then you have a point of reference from one pulsar to another.

      1. JeffyPoooh
        Pint

        Re: Missing something?

        Don't cross the beams. - Ghost Busters

    3. mr.K

      Re: Missing something?

      Pretty much the same way you do with GPS satellites. The difference is that the pulsars are stationary (more or less) and you are moving. As long as you have more than enough, you can lose a few and when you gain a new one, you place that one into your already established system of references. You would get a little drift over distance unlike GPS where the satellites already know where they are, but that drift will not be more than a meter for each complete new set of pulsars. With time of course when we have sent more ships* out there they will share data and you will get a near perfect navigational starmap.

      *WHEN not IF!

  9. John Smith 19 Gold badge
    Thumb Up

    The idea of using pulsars for spacecraft nav has been around for a few years as well.

    But I suspect that it has taken this long for someone to work the unknowns to get a viable system out of it.

    Thumbs up for that.

    But remember the state of the art for spacecraft computers is about a 200Mhz POWER or SPARC processor., which is rather below what an Apple laptop can manage.

    1. jake Silver badge

      Re: The idea of using pulsars for spacecraft nav has been around for a few years as well.

      "But remember the state of the art for spacecraft computers is about a 200Mhz POWER or SPARC processor., which is rather below what an Apple laptop can manage."

      I suspect that me with my 25 year old 33Mhz 386SX+mathco, 8meg RAM can do more than almost all of all of Apple's current offerings in the hands of the current luser-base.

      1. Anonymous Coward
        Anonymous Coward

        @jake

        >>I suspect that me with my 25 year old 33Mhz 386SX+mathco, 8meg RAM can do more than almost all of all of Apple's current offerings in the hands of the current luser-base.

        I agree, but don't you mean DX rather than SX.

        I had a tower with the same chips and a huge fat SCSI drive (300MB IIRC)

        A great machine.

        1. jake Silver badge

          Re: @jake

          "don't you mean DX rather than SX."

          No. I mean SX+mathco.

          Mine has a pair of 200Meg Maxtor drives. She still runs quite nicely.

        2. Thesheep

          Re: @jake

          Wasn't an SX with a maths coprocessor the same thing as a DX?

          1. jake Silver badge

            @Thesheep (was: Re: @jake)

            No. The DX had a mathco on-board, operating at silicon speed. The SX+mathco was two different chips communicating across the motherboard, somewhat slower. Seat of the pants? No difference. Price? Probably $250 cheaper for the SX+mathco in 1988ish.

            1. Emo

              Re: @Thesheep (was: @jake)

              It was only the 486DX onwards where the math co-pro was incorporated into the chip. 486SX no math co-pro.

              386SX was a 32bit chip with a 16bit data bus - no math co-pro on board.

              386DX was a 32bit chip with a 32bit data bus - no math co-pro on board.

              387 Math co-pro's were separate chips.

              The math co-pro was quite a bit dearer than the cpu back in the day.

              1. jake Silver badge

                @Emo (was: Re: @Thesheep (was: @jake))

                ::heh:: You are quite correct. Mea culpa. Brain fart on my part.

                The old 386sx+mathco is still quite functional for day-to-day work, regardless :-)

                1. MrT

                  386DX...

                  ...my 25MHz one did sterling effort using MathCAD to calculate our iterative thermal comfort calculations based on Fenger's work - 387 co-pro kept each change in the data down to less than a minute to recalculate, and there were IIRC 4 or 5 variables changed per page. Roughly the same time as the dept 486SX-33, again IIRC. Good machine.

                  1. roger stillick
                    Happy

                    Re: 386DX...

                    IBM made a cheap PC using 386 chips w/ defective built in co processors and 387 co processors which were 386 chips w/ defective processors n good math set... at under USD 13.00 each, IBM had a way to sell a bunch of really good boxes really cheaper than anyone else could using USD 90.00 fully tested chips from INTEL...

                    Had one to run Mathcad 5.0 on some microwave plumbing problems... ah, the Maple engine... huge table of ops...

                    IMHO= really believe MS used this 'hidden tables' idea in their Office program...RS.

                2. dssf
                  Pint

                  Re: @Emo (was: @Thesheep (was: @jake))

                  Jake, your use of the term "mea culpa" preceded mine, and makes me wonder about the astronomical odds off it in two different uses in the same topic.

                  Cheers!

              2. dssf

                Re: @Thesheep (was: @jake)

                Wow! You're taking me back to 1992, when I bought my first computer:

                http://en.wikipedia.org/wiki/Intel_80486DX2

                Which had a 486dx2 66, a Spyder/Spider graphics card, tower casee, other stuff, and cost me about $1990. Back when home computers were FINANCED. Thanks for the memory lane trip/voyage!

    2. MacroRodent Silver badge

      Re: The idea of using pulsars for spacecraft nav has been around for a few years as well.

      But remember the state of the art for spacecraft computers is about a 200Mhz POWER or SPARC processor., which is rather below what an Apple laptop can manage.

      On the other hand, the original academic developers of the code have probably not really optimized its performance. Give the algorithm to a few good hackers and ask them to make it fast, and you will probably find the spacecraft hardware is quite sufficient.

      1. jake Silver badge

        @ MacroRodent (was: Re: The idea of using pulsars for spacecraft ::snippage::)

        "On the other hand, the original academic developers of the code have probably not really optimized its performance."

        You've never actually worked on spacecraft software/firmware, have you?

        1. bazza Silver badge

          Re: @ MacroRodent (was: The idea of using pulsars for spacecraft ::snippage::)

          @Jake,

          I suspect that they've not worked on any embedded system like that at all.

          The following may be of interest. The Lockheed A12 and SR71 did navigation by star tracking. They had a little telescope system on the top, they could sight for particular stars and work out their terrestrial position that way. Kind of like an automation of navigation by sextant. That was all done with 1960s era computing. It follows that that's all that is needed for this sort of problem. A modern day 200MHz rad hardened PowerPC is massive overkill for this sort of navigational problem.

          1. jake Silver badge

            Re: @ MacroRodent (was: The idea of using pulsars for spacecraft ::snippage::)

            Exactly.

            Long-range spacecraft had different issues ... SR71 is close, but is manually operated.

        2. Lord Elpuss Silver badge

          @Jake re MacroRodent

          "You've never actually worked on spacecraft software/firmware, have you?"

          Neither have you. And MacroRodent's point was the the original ACADEMIC developers of the code hadn't optimised it - and he's almost certainly quite right. If it were optimised for space use it might be quite a lot more efficient.

          As usual, in your attempt to be scathing and witty you manage once again to miss the point.

          1. jake Silver badge

            Re: @Jake re MacroRodent

            "Neither have you."

            OK. If you say so.

            "the original ACADEMIC developers of the code hadn't optimised it "

            Uh ... you are very, very wrong. We worked hard to optimize it. I think we did a pretty good job.

            "As usual, in your attempt to be scathing and witty you manage once again to miss the point."

            As usual, in your attempt to be "knowing", you fail to listen to your elders. Grow up.

        3. MacroRodent Silver badge

          Re: @ MacroRodent (was: The idea of using pulsars for spacecraft ::snippage::)

          You've never actually worked on spacecraft software/firmware, have you?

          No, but I was not aware the article was talking about software already prepared for spacecraft. In my experience from other fields, most code done for academic papers is more like proof of concept (getting it to work at all more important that making it fast), not something you can deploy for production use. Apologies if the assumption was wrong.

  10. -tim
    Pint

    Why is my prime meridian wobbling?

    A modern Navstar GPS receiver will have active filters to remove pulsar noise. A GPS engine runs a 12th degree polar coordinate polynomial solving engine using a Kalman filter and repeatedly solving for unknowns until everything is about right. By the time it decides everything is close enough, the clock inside the chip set tends to be match the ones on the transmitters to about 90 nanoseconds. The Sats send a message describing the wobble of the sat and has factors to account for the sun, moon and major planets. To do the same with pulsars, you need to adjust for the wobble of the earth around the sun and the suns local wobble as well as the effects near the pulsar where some of them have huge planets orbiting close enough to cause problems. The basics for a palsur based system have been well known for since before 2002 but the real problem is collecting enough data and distributing it to a computer in a reasonable way to be useful. The real world mapping issues will also need to set up local map datums for planets and currently that will require putting up a very large dish to collect the data and answering the difficult question of "exactly where is the meridian?" for each planet.

    A Beer for Wilhelm Beer who defined the meridian on Mars.

    1. jake Silver badge

      Re: Why is my prime meridian wobbling?

      During the meanwhile ... you are still on this muddy rock called "Earth". Learn to read a fucking map. It's all you really need to navigate as an average human ...

      1. Khaptain

        Re: Why is my prime meridian wobbling?

        The problem with maps is that they exist, in a meaningfull / complete state, only "after" someone has been where you are going ( and then relates the information to a map maker - or does it himself).......

        The world was flat until someone went over/round the edge. The maps before then had some "anomalies".......

        I am sure that when/if we learn to travel great distances in space we will learn that it is different from what we imagined/assumed/guessed/calculated.

        1. Charles 9 Silver badge

          Re: Why is my prime meridian wobbling?

          Actually, it was well known the world was round. After all, if it were flat, the horizon would move and you wouldn't see significantly further from atop a tower or upon a crow's nest.

          Now, the interior of Africa and anything west of Portugal was basically Terra incognita, and that was what kept down the idea of circumnavigation: not knowing what lay in the way.

          1. Khaptain

            Re: Why is my prime meridian wobbling?

            Effectively, after a quick Wikipedia search, these 2 articles state the approxiamate dates for believing that the earth was flat.Flat Earth and Myth of the Flat Earth, it was actually a very long time ago, pre 300 BC when "educated" men began to accept the spherical version.

            1. James Micallef Silver badge
              Thumb Up

              Re: Why is my prime meridian wobbling?

              "it was actually a very long time ago, pre 300 BC when "educated" men began to accept the spherical version."

              Not only did learned men accept the earth was round as early as 300BC, but by 200BC Erasthotenes* had already calculated the circumference to a remarkable accuracy** based on nothing more than the distance to a known point on the equator.

              *spelling??

              **within a couple of % IIRC

              1. wsm
                Happy

                Re: Why is my prime meridian wobbling?

                It actually takes only a bit of reason and some nearly accurate measurements to determine the dimensions of a meridian, with the prime meridian being an arbitrary point, for a planetary body. Here is a reasonable explanation of how Eratosthenes did it:

                http://geography.about.com/od/historyofgeography/a/eratosthenes.htm

                We can do the same more easily from orbit and have created accurate vertical datum for nearby planets of interest, such as Mars:

                http://mars.jpl.nasa.gov/mgs/faqs/faq_sci.html

                Beyond that, a universe-wide GPS that helps us navigate amongst the bodies is more complex than describing the ones we can observe.

              2. Annihilator Silver badge
                Boffin

                Re: Why is my prime meridian wobbling?

                "based on nothing more than the distance to a known point on the equator."

                Pedant mode on - was a point on the tropic of cancer (or close enough to where they thought it was) as it was based on the angle of the sun's rays on the summer solstice.

          2. Alan Brown Silver badge

            Re: Why is my prime meridian wobbling?

            The reason people thought Columbus was nuts wasn't because they throught the world was flat, it was because he was using flawed ideas which caculated the circumference of the earth at about 2/3 of reality and they thought he couldn't carry enough supplies to get to India the long way round.

            As it was his flotilla was well past the point where they could turn back and not starve along the way when they finally did hit land. He'd been faking log readings and keeping the real ones under wraps in order to avoid mutiny by an increasingly worried set of crew. The real distance covered was well in excess of what he'd calculated it should be.

            So as it turned out, he was wrong and they were right, but the americas got discovered along the way.

            1. Michael Wojcik Silver badge

              Re: Why is my prime meridian wobbling?

              So as it turned out, [Columbus] was wrong and they were right, but the americas got discovered along the way.

              Actually, the American continents - at least North America - were well known to several groups in Europe before Colon spoiled it for everyone else by letting the aristocracy and the Church in on the secret. The Basque had been fishing cod off the North American coast for decades, perhaps centuries; and some of the mercantile groups had caught on too. There's a letter from one Giovanni Caboto - "John Cabot" to his English employers - to Colon complaining about his spilling the secret.

              It's most likely Colon didn't know about the Americas, but he was far from the first European to discover them.

              1. Charles 9 Silver badge

                Re: Why is my prime meridian wobbling?

                "It's most likely Colon didn't know about the Americas, but he was far from the first European to discover them."

                Plus IIRC Vikings had taken some sojourns to the west but didn't make much of it.

                What Columbus did was tip off a country (Spain) that just happened to be itching for exploration. Asia was pretty much closed to them as the Turks controlled the Red Sea route and the Portuguese had the Horn of Africa covered. When Columbus came back and told them this new land to the west was full of novel (and valuable) goodies, Spain suddenly realized, "Who needs Asia?"

                So, not so much the first to find the place but the one to make the place famous.

    2. Martin Budden
      Boffin

      Re: Why is my prime meridian wobbling?

      "To do the same with pulsars, you need to adjust for the wobble of the earth around the sun and the suns local wobble"

      The academics have developed software which uses signals from pulsars to calculate the position of the centre of gravity of the solar system. That point doesn't wobble.

      Put the same software in a spacecraft and you get the position of the spacecraft. Yes the spacecraft will wobble due to pull from local planets & a slightly wobbling sun, but the whole point is that we know exactly where the spacecraft is, wobbles and all.

      1. JeffyPoooh
        Pint

        Re: Why is my prime meridian wobbling?

        "...the centre of gravity of the solar system. That point doesn't wobble."

        Of course it does. If all the heavy planets happen to be on the left, then the C of G will wobble to the left a bit.

        The C of G will wobble around as per the motions of the major planets.

        If the Sun moves at all, it'll be in-phase and add to the overall wobble.

  11. Christoph

    But my TEMPO2 told me to come this way!

    How was I to know there was a black hole there? What do you mean, 'why didn't I watch out where I was going'? The computer's supposed to do that!

  12. unitron
    Headmaster

    " *Bootnote: All right, all right. Here we are looking at the universe and an author can get pedantry over one poorly-phrased sentence. I've corrected it. RC. ® "

    Shouldn't that be "get pedantic"?

    Pedantic icon, natch.

    1. James Micallef Silver badge
      Headmaster

      No, I thing he's using the "get" in "an author can get pedantry" in the sense of receiving ie being on teh reveiving end of someone else's pedantry, as opposed to "get pedantic" in the sense of himself starting to become pedantic

      1. Frumious Bandersnatch

        Pedantry is just fine. As in "Behold! ... I give you THE UNIVERSE!. You... give me pedantry :("

  13. Arctic fox
    Thumb Up

    Thank you Richard for yet another contribution.

    Informative and interesting as always.

  14. Dave Harvey
    Black Helicopters

    Will an alternative to USA's GPS be allowed?

    How long before the US military decide that this system , like Galileo, shouldn't be allowed as it "threatens national security", and demand that the owners of said pulsars must agree to shut them down at times of "emergency"?

    1. cortland
      Alien

      Re: Will an alternative to USA's GPS be allowed?

      The soonest they could be served is 552 years at lightspeed; a reply will come back no faster, so we will become aware of their intent to appeal to the Intergalactic Court (if they even GET our puny radio wave signals) in the Andromeda galaxy in not less than 114 years. Our personal appearance at that court will be required , and since the loser pays court costs . . .

  15. JLV
    Joke

    Another Eureka moment - Independence Day.

    "It's free software that I can run on my Mac laptop with no worries at all,”"

    Ah ha, now we know why Jeff Goldblum was able to get a virus from a Mac into the invading alien's computers.

    And all that time we thought aliens being Mac compatible was a dumb idea.

    Just so you see, the next lot of aliens will be using Windows Phones.

    1. Matt Piechota

      Re: Another Eureka moment - Independence Day.

      "Ah ha, now we know why Jeff Goldblum was able to get a virus from a Mac into the invading alien's computers."

      I always figured it was emacs running on Mac. M-x alien-virus-mode.

  16. Anonymous Coward
    Anonymous Coward

    "we need to know the centre of mass of the solar system to within a metre or so …"

    Wow.

    ('cuz no-one has said it yet)

  17. RobHib
    Megaphone

    Duh?

    “we need to know the centre of mass of the solar system to within a metre or so … "

    Right!! ...And I need to know the dimensions of my house to an accuracy of 10^-18 cm or so--give or take a proton width or two.

    Would someone please explain to me how this would be achievable even with these precise time standards. May I also suggest we don't even know how big the the solar system is for that accuracy. For instance, in the last year or two there's been some debate whether Voyager has actually past the 'edge' of the solar system into interstellar space or not.

    1. asdf

      Re: Duh?

      >Sedna's highly elliptical orbit means that the probability of its detection was roughly 1 in 80, suggesting that, unless its discovery was a fluke, another 40–120 Sedna-sized objects [≈1 × 10^21 kg] would exist within its region [orbiting our sun].

      Yes its a small percentage of the total mass (isn't like %99.9 of solar system mass in the sun?) but as you imply knowing all mass in the solar system seems necessary to get meter sized accuracy.

      1. RobHib

        @asdf - Re: Duh?

        It's the sheer matter of fact way that quote was made, no qualifier, no supporting argument etc.

        Given the huge magnitudes of accuracy involved, not to mention how it would be achieved, the statement affronts my sensibilities in the same way a mathematician is affronted by a maths statement without proof.

        I can't recall ever having seen a statement like that before (in such a context that is).

    2. PC Paul

      Re: Duh?

      "For instance, in the last year or two there's been some debate whether Voyager has actually past the 'edge' of the solar system into interstellar space or not."

      *passed

      Well, to be fair that isn't anything to do with knowing where Voyager is, or even where the edge of the Solar System is. It's to do with 'what' the edge of the solar system is. And do you even need to know that to know where the centre of mass is? Isn't it just going to be the centre of rotation of the combined bodies making up the solar system?

      1. RobHib
        Alien

        @PC Paul -- Re: Duh?

        Hum, I didn't see that grammatical (nor the redundant 'the') even after a second reading, amazing! It irks me there's no post posting edit feature to correct it.

        Well, I'm not in disagreement with your points, but more on that in a moment. The trouble with forums is that précising, sweeping statements and over-generalisations are the order of the day. Some weeks back I made a quite detailed post to which there seemed to be little disagreement (all thumbs up) but the immediate following post was, quoting verbatim:

        "Summarize man. Summarize."

        To which there were 5 thumbs up and one down (and that wasn't me). One's damned either way.

        In my defence, I made the point about Voyager and the 'edge' of solar system because it's current and topical, it was not intended to be precise physics. Even if the solar system has a very sharp edge on a solar scale, it's still going to span a long way in human terms—a damn side larger than a few metres I'd suggest. In one sense that was the point I was making, but also I was suggesting that such extraordinary precision wasn't feasible, certainly not in any practical sense. You'll also note that I did put 'edge' in quotes because the concept was, for all practical considerations, hypothetical.

        You'll also note that I was affronted by the extraordinary and unqualified statement from which I quoted, this I amplified upon in my reply to asdf.

        Back to your point about the centre of mass of the solar system and the centre of rotation. In principle, I'd have to agree with this, but I come back to why I initially made the post which is the incredible ramifications of determining the centre of mass of the solar system to within a metre or so. Frankly, Dr Hobbs shouldn't be allowed to make such a sweeping statement without substantial qualification. Such an extraordinary statement requires an extraordinary explanation.

        In essence, Dr Hobbs statement brings more the engineer out in me than scientist. Not only is there the practical problem of measurement, which is well outside the scope and precision of any human endeavour to date, but also at such huge precision the question of whether our current understanding of the laws of physics is sufficient to make a reasonable / sensible calculation of such precision. (That's assuming we could actually measure the centre of mass to within an 'accuracy' of a metre.)

        Whilst we may think we've measured the centre of mass with such accuracy it may not be the case as our mathematical analogue of nature may be sufficiently imprecise as to make the measurement essentially useless. For starters, at extreme precision over many magnitudes, actual relativity in nature may not behave exactly as the mathematical analogue predicts, simply: relativity may be non-linear at the extremities. (This matter is still open to experimentation and debate, as with all aspects of relativity.)

        Remember, physics is accursed with that damn mathematical concept called zero, it mucks up the Big Bang, Black holes, and quantum equations. In fact, New Scientist, last week (17 August '13, No. 2930) had an article on the divide-by-zero problem titled 'The infinity illusion', p32:

        http://www.newscientist.com/article/mg21929300.700-infinitys-end-time-to-ditch-the-neverending-story.html

        However, for the moment let's assume relativity is precisely as the equations show it to be, then we're back again to the problem of measurement. As I see it, we've serious problems in determining an instantaneous result for the centre of mass, as the solar system is a big place and relativistic effects would matter at such precision—determining the integrand so to speak would seem very problematic. Moreover, calculating the centre of mass to such precision over time would also be problematic as the solar system is full of dynamic components, thus the centre would wobble and appear fuzzy. This, in turn, would be exacerbated by the fact that the solar system itself is being acted upon by our galaxy's components as it travels through space.

        I don't claim to know the extent of these effects but I'll need a damn good argument to convince me that 'within a metre or so' has any practical meaning outside the hypothetical.

  18. JeffyPoooh

    Got Rubidium?

    Yes. :-)

    A cheap Ublox NEO-6T chip gives one 15ns absolute accuracy. Time Nuts know all about this topic. One time nut owns several cesiums (and now masers) and has confirmed relativistic time shifts (23ns) of a short vacation up a mountain. Ref: http://www.leapsecond.com/great2005/tour/

    A pulsar's pulse should sweep across the Earth. The apparent movement of the pulse front is probably an interesting sub-topic itself, but this margin is too small etc. etc.

  19. passportholder
    Headmaster

    Gravity Waves --> Gravtiational Waves

    http://en.wikipedia.org/wiki/Gravitational_wave 'Not to be confused with Gravity Wave'

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