Why The Prime Meridian Isn't At 0º

  • Published on: 05 January 2015
  • http://tomscott.com - http://twitter.com/tomscott - If you travel to Greenwich, stand on the famous Prime Meridian Line -- which is marked with a physical line and a sculpture at the Royal Observatory -- and look at your GPS, it won't read 0° longitude. It'll be slightly out. Who's right? And why?

    Many thanks to my lovely cameraman Tom Morris (http://tommorris.org), who dealt with the cold wind admirably!
  • Runtime : 3:14
  • tomscott tom scott things you might not know Greenwich (City/Town/Village) greenwich meridian Prime Meridian (Invention) Royal Observatory Greenwich (Astronomical Observatory) Greenwich (Location) Global Positioning System (Industry) Location (Literature Subject) Johns Hopkins University (College/University) Applied Physics Laboratory (Spacecraft Manufacturer) george airy astronomer royal wgs84 ellipsoid spheroid GPS Navigation Device (Consumer Product)


  • AtomicFPV
    AtomicFPV   2 days ago

    0:35 Flat earther: ThAt iS iNcoRrEct

  • en gu
    en gu   3 days ago

    Flat earthers have left the chat.

  • Cam Adams
    Cam Adams   4 days ago

    So what you are saying is: we need to pound out the lumps

  • 4dee 9arr
    4dee 9arr   1 weeks ago

    2:24 shows a kid and his father hitting that t-pose

  • Qermaq
    Qermaq   2 weeks ago

    We're ALL in all hemispheres at once, depending on how you measure it.

  • C J Bowen
    C J Bowen   2 weeks ago

    yea all that plus magnetic north aint north and the declination moves a bit now and then so if u are a bit confused really nobody knows really which way truly is up....

  • Kavi Gupta
    Kavi Gupta   3 weeks ago

    I love that the actual standard meridian is in America 🇺🇲

  • David Lewis
    David Lewis   3 weeks ago

    After the big earthquake in Japan in 2011, I measured a 76mm (average) change in position of control points at Southend Airport using an accurate GPS device (+/-7mm) until the GPS network was recalibrated :)

  • KnowBounds
    KnowBounds   3 weeks ago

    Fun Fact: The video length has the digits of pi

  • namensklauer
    namensklauer   3 weeks ago

    Why the prime meridian isnt at 0°? easy! because 0 isnt prime

  • Nutelephant08
    Nutelephant08   4 weeks ago

    It still confuses me how Greenwich is pronounce Grenn Itch

  • Warp Zone
    Warp Zone   1 months ago

    At the time of writing, it's not 0º at the Prime Meridian because it's the middle of spring! 😛

  • gundam fan
    gundam fan   1 months ago

    What the Earth is not flat???? what is this madness

  • Stephen West
    Stephen West   1 months ago

    Was anyone else told if the earth were scaled down to the size of a cube ball, it would be significantly smoother than most and very much acceptable for play? And does that feel like it contradicts this a bit?

  • Mr Zu
    Mr Zu   1 months ago

    But, ... but the earth is flat! There is no Meridian!!!

  • James Bond
    James Bond   1 months ago

    I'm in whatever hemisphere I say I'm in. Humans invented the different hemispheres, therefore it has no basis in reality.

  • Mystical Apple
    Mystical Apple   1 months ago

    I propose a new system: Wherever Tom Scott’s red shirt is at any given moment is 0,0

  • Red Dwarf
    Red Dwarf   1 months ago

    Flat earthers measure longitude and latitude like a pizza being sliced up.

  • Peter Weatherley
    Peter Weatherley   2 months ago

    Just saying - opportunity missed to include the Death Star superlaser on that red animation hehehe

  • Christopher Morrow
    Christopher Morrow   2 months ago

    At scale isn't the Earth more smooth then a billiard cue? How do you call that lumpy? Also, of course it's an abstraction. Therefore the line itself cannot move as the abstraction stays stationary and the physical potion it corresponds to shifts. That's not movement.

  • hussami khaldoun
    hussami khaldoun   2 months ago

    Mecca should be the prime longitude and latitide line 0 because it is in the center on the dry land and all but Mecca drifts from its position .

  • Mia Kay
    Mia Kay   2 months ago

    So.. you're in a superposition of "in both hemispheres" and "in 1 hemisphere"

  • Guy Boo
    Guy Boo   2 months ago

    Just once I want to see a YouTube video with a model earth that says (1:1 scale (camera is very far away))

  • firefist x
    firefist x   2 months ago

    I could be on vacation if if i only i knew the math

  • Volcanoman
    Volcanoman   2 months ago

    Longitude is an abstraction. There is no way to definitively call one point of the Earth the zero meridian in any objective sense. However, you CAN call the equator objective, since it's the place where there is no variation in length of day, ignoring the effects of altitude (i.e. keeping it constant). So if you set an imaginary, unobstructed line of equal daytime length no matter the date at a height higher than any of the mountains on Earth, and project that line onto the Earth, you have an objectively defined equator. And if you do the same thing for every other latitude, defining them independently of the peaks and valleys that alter the length of the daylight (at the equator it's always about 12 hours, though it's actually technically shorter than that given that the sidereal day is about 4 minutes short of 24, and APPEARS longer than that because of atmospheric refraction*), you have an objective system. Granted, it's wrong, since the Earth is squashed, so that the distance from the center of the Earth is greater at the equator than at any other point, but it's still objective (and you CAN create an ellipsoidal latitude system that would be MORE correct, though there are still variations in shape that mean that it's never exactly right). So latitude is not an abstraction but a fact of Earthly life.Of course, every point on land or sea-floor will see its latitude and longitude change with the movement of the tectonic plates. So those lines on the ground that countries like Ecuador (at la Mitad del Mundo monument) paint to represent the equator eventually go out of date (the time it takes for this to happen varies depending on the SPEED of the respective plate, which varies from 2 cm to over 8 cm per year, and the direction in which it's moving**). But that doesn't mean that latitude isn't objective at any given time, nor that it can't be predicted objectively years ahead of time. *Also, the equatorial day IS longer than 12 hours due to the fact that sunrise and sunset are defined as the times at which part of the disk of the sun become visible and not visible, respectively; sidereal "daytime" on the other hand is defined as the time between which the CENTER of the sun goes above, and below the horizon, which in the absence of atmospheric refraction and in a perfect 24-hour day, would be exactly 12 hours at the equator...or at an equinox.**In the case of Ecuador, the South American plate is moving slightly north of west (by 10-15 degrees), at a speed of about 30 mm a year. It's been awhile since I've done vector calculations (and doing so on a kind-of-spherical surface likely requires some VERY complex maths), but simplifying the problem by assuming a flat Earth, within a year, the plate will move about 5-7 mm north (this depends on the exact angle of course, and the speed varies a bit, from 27-34 mm). Thus, the line, being about 10 cm thick (iirc...it's been 15 years since I visited Ecuador), would still cover A PART of the actual equator for at least 10 years after being painted (since 5 cm are north of it, and 5 are south at the time of drawing, the equator only needs to travel 50 mm to leave the line, which would take a minimum of 10 years). More interestingly, the continent could be rotating very slightly clockwise, which would subtley change the orientation of the line on the ground (you'd have to move it COUNTER-clockwise to compensate). But this effect would be so minimal it would take lasers to accurately perceive.

  • AceHighJohn
    AceHighJohn   2 months ago

    Does anyone else sometimes wonder if Tom has a nemesis called Scott Tom that wears a blue shirt and believes flat earth theory and is generally a complete conspiracy nut.... Just me?

  • Malta
    Malta   3 months ago

    Technically, you’re always in both hemispheres if you think about it. It just depends how you measure it

  • ryan B
    ryan B   4 months ago

    The earths, a bit Wanky and Wonky, and lumpy and that bit...i really like how these people think they know the military reasons.

  • Lee Elliott
    Lee Elliott   4 months ago

    A few years ago I was in Ecuador and visited the equatorial monument a few kilometers north of Quito. It, supposedly, is located on the equator. There were even basins of water located on either side of this "line" showing water swirling down the drain in opposite directions. Later, when looking at this monument on Google Earth, it appeared the equator was about 900 feet south of the monument. Made me strongly suspect the opposite swirling drains were a scam. Next time I'm down that way I'm going to demand my money back.