The Simple Secret of Runway Digits

Summary

This script delves into the intriguing world of airport runway numbering, explaining how they are determined by wind direction, compass headings, and the Earth's magnetic field. It humorously highlights the complexities of aviation logistics, the Coriolis Effect's impact on wind patterns, and the distinction between magnetic and true north. The video also touches on the history of navigation and the potential chaos a geomagnetic reversal could cause for runway designations.

Takeaways

• 🛫 Runway numbers at airports are determined by the direction of the prevailing winds, which influence the orientation of the runways for safe takeoff and landing.
• 🌬 Planes typically take off and land into the wind to use less runway and ensure more stable landings.
• 📊 Wind roses are used to visualize the dominant wind directions and frequencies, helping in the planning of runway orientations.
• 🌀 The Coriolis Effect influences wind patterns, creating stable trade winds that are considered when planning airport layouts.
• 📐 Runway numbers are derived from compass headings, rounded to the nearest ten, and then the zero is dropped for simplicity in communication.
• 🔢 Runways are numbered from the perspective of the plane approaching the airport, not from the airport's perspective.
• 🔠 Parallel runways are designated with an 'L' for left, 'R' for right, and sometimes 'C' for center to distinguish between them.
• 🧲 There are two 'norths': the Magnetic North that compasses point to and the True North used by GPS; runway numbers are traditionally based on the Magnetic North.
• 🌐 The Earth's magnetic field is not stable and can move, which may require runway numbers to be repainted to reflect changes in the magnetic north.
• 🇨🇦 Canada has adopted a system based on True North due to the frequent need to repaint northern runways as the Magnetic North moves.
• 🌐 The potential for the magnetic poles to flip could cause further confusion in runway numbering if it were to occur during a transition to True North.

Q & A

Why do planes take off and land into the wind?

Planes take off and land into the wind because it allows them to use less runway and provides safer and more stable landings.

What is a wind rose and how is it used in airport planning?

A wind rose is a data visualization tool that shows the direction, strength, and frequency of wind. It is used in airport planning to determine the most efficient runway orientation based on prevailing wind patterns.

Why do some airports have an X or V layout?

Airports with an X or V layout have multiple runways oriented in different directions to accommodate crosswinds and ensure safe landings when the wind is not aligned with the runway.

How are runway numbers determined?

Runway numbers are determined by the magnetic compass heading that planes use when approaching the runway. The heading is rounded to the nearest ten degrees and then adjusted according to aviation conventions.

What is the significance of the Coriolis Effect in relation to wind patterns?

The Coriolis Effect causes air currents to twist clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere, creating stable wind patterns like trade winds.

How do parallel runways at an airport get numbered?

Parallel runways share the same number but are distinguished with an 'L' for left, 'R' for right, and 'C' for center to indicate their position relative to each other.

Why might runway numbers change over time?

Runway numbers may change if the Earth's magnetic field shifts, as runway numbers are based on compass headings which are affected by the magnetic north pole's position.

What is the difference between Magnetic North and True North?

Magnetic North is the direction that a compass points to, which is influenced by the Earth's magnetic field. True North is the geographic north, based on the Earth's axis of rotation and used in GPS navigation.

Why do pilots still use the traditional magnetic north in navigation?

Pilots use the traditional magnetic north because it has been a longstanding practice in aviation, and the magnetic north and true north are currently close enough for practical purposes.

How does the Earth's magnetic field movement affect runway numbering?

As the Earth's magnetic field moves, the compass headings change, which in turn requires runway numbers to be updated to ensure they accurately reflect the correct approach direction for pilots.

Why did Canada switch to using True North for runway numbering?

Canada switched to True North for runway numbering to avoid the need for frequent updates due to the movement of the magnetic north pole, which is particularly problematic in northern regions.

Outlines

00:00

🛫 Runway Numbering Explained

This paragraph delves into the logic behind airport runway numbering. It starts with the observation of a seemingly excessive number of runways at L.O.L. Airport and leads into a discussion about the importance of wind direction for safe takeoffs and landings. The video explains the historical use of wind socks and the creation of wind roses to determine the most favorable runway orientations. The concept of the Coriolis Effect and its impact on wind patterns is introduced, highlighting the need for multiple runways in certain locations to accommodate varying wind directions. The paragraph concludes with an explanation of how runways are named based on compass headings, adjusted for the perspective of approaching aircraft.

05:01

🔢 The System of Runway Numbering

This section further explores the specifics of runway numbering, detailing the rounding and zero-truncation conventions used to simplify communication between air traffic control and pilots. It discusses the challenges of numbering parallel runways and the introduction of 'L', 'R', and 'C' suffixes to differentiate them. The paragraph also touches on the standardization of runway number fonts and sizes for clarity. The speaker humorously acknowledges a personal navigational error, emphasizing the importance of accurate runway identification. The discussion then shifts to the broader implications of runway numbering, including the impact of the Earth's magnetic field on compass readings and the potential need for runway number adjustments due to shifts in the magnetic North Pole.

10:02

🧭 Magnetic North vs. True North

The paragraph explores the distinction between magnetic north and true north, explaining how the Earth's magnetic field is generated by convection currents of molten iron in the Earth's core, influenced by the Coriolis Effect. It discusses the historical and ongoing alignment of the magnetic north with the geographic north, despite the magnetic field's inherent instability. The speaker highlights the potential for the magnetic field to change dramatically, such as through a pole reversal, and the implications this would have for navigation and runway numbering. The paragraph concludes with a reflection on the Earth's magnetic field's movement and its impact on the need for periodic updates to runway numbers, particularly in regions closer to the magnetic poles.

15:05

🌐 The Dilemma of Runway Numbering Systems

This final paragraph addresses the issue of having two systems for runway numbering due to the movement of the magnetic North Pole. It explains how Canada, affected by frequent changes in the magnetic field's position, has shifted to using a system based on true north, which is fixed and does not change. However, this creates inconsistencies with the rest of the world that still primarily relies on magnetic north for runway orientation. The speaker satirically suggests that a global switch to true north should occur before another pole reversal, emphasizing the need for a unified and stable system for the sake of aviation safety and efficiency.

Keywords

💡Runway Numbers

Runway numbers are numerical designations given to airport runways based on their magnetic headings. In the video, it explains that these numbers are derived from the compass heading that aligns with the runway's direction when facing the wind, rounded to the nearest ten degrees. The concept is integral to the theme of aviation and navigation, as it helps pilots identify and communicate the correct runway for takeoff and landing.

💡Windsock

A windsock is a simple cone-shaped fabric sock that indicates wind direction to pilots and ground crew. The video mentions its use in early aviation for directing pilots to the runway that is parallel to the wind, which is crucial for safe takeoffs and landings. It is an example of a simple yet effective tool that has contributed to the evolution of runway design.

💡Wind Rose

A wind rose is a data visualization tool used to depict wind direction and frequency. The script explains that by recording wind data, a wind rose can help in determining the predominant wind direction at an airport, which is essential for runway planning. It is a key concept in the video as it relates to the strategic layout of runways to accommodate prevailing wind patterns.

💡Coriolis Effect

The Coriolis Effect is a phenomenon that causes the path of objects, including air currents, to deflect due to the Earth's rotation. In the video, it is mentioned as the reason why wind currents twist clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere, affecting the formation of trade winds and the orientation of runways.

💡Convection Currents

Convection currents are the movement of fluids (like air or liquid metal) due to differences in temperature. The video describes how these currents are responsible for the Earth's heat distribution and the creation of wind patterns, which in turn influence the direction of runways. This concept is central to understanding the natural forces that shape the layout of airport infrastructure.

💡Magnetic North

Magnetic North refers to the point on the Earth's surface where the planet's magnetic field points directly downwards. The video discusses the distinction between Magnetic North and True North, explaining that runway numbers are traditionally based on the compass heading to Magnetic North, which can move over time, affecting the accuracy of runway designations.

💡True North

True North is the geographic location of the Earth's northernmost point, as opposed to Magnetic North, which is based on the planet's magnetic field. The script highlights the debate over whether runway numbers should be based on True North, which is fixed, or Magnetic North, which can change. This distinction is crucial for the accuracy and consistency of navigational systems in aviation.

💡Electromagnetism

Electromagnetism is one of the four fundamental forces in nature, arising from the interaction between electric currents and magnetic fields. The video touches on this concept to explain the Earth's magnetic field, which is generated by convection currents of molten iron in its core. Understanding electromagnetism is key to grasping the dynamics of the Earth's magnetic field and its impact on navigation.

💡Parallel Runways

Parallel runways are multiple runways that run alongside each other in the same direction. The video script explains that when there are parallel runways, they are designated with the same number but are distinguished as 'left', 'right', or 'center' to avoid confusion for pilots. This concept is important for the organization and safety of air traffic at large airports.

💡Magnetic Pole Reversal

Magnetic Pole Reversal refers to the phenomenon where the Earth's magnetic north and south poles switch places. The video mentions that such an event could potentially disrupt the current system of runway numbering based on Magnetic North. This geological occurrence is a significant factor in the ongoing debate about the use of True North versus Magnetic North in navigation.

💡Cockpit

A cockpit is the area in an aircraft from which the pilot controls the plane. The video script uses the term to illustrate the importance of the pilot's compass in the cockpit for aligning with the correct runway heading. The cockpit is central to the theme of aviation safety and precision, as it is where pilots rely on various instruments, including the compass, for navigation.

Highlights

Runway numbers at L.O.L. Airport in Nevada's desert suggest more runways than actually exist, raising questions about their purpose.

Runway numbering is based on the direction planes take off and land, influenced by wind direction for safety and efficiency.

Early aviation used wind socks and triangular runway layouts to align with wind direction, but this became impractical with larger airports.

Wind roses, a data visualization tool, help determine predominant wind directions for runway planning.

The Coriolis Effect influences wind patterns, creating stable trade winds that are important for airport planning.

Airports with frequent crosswinds may have an X or V layout to accommodate safe landings in varying wind conditions.

Runway numbers are derived from compass headings, rounded to the nearest ten for simplicity and clarity in communication.

Pilots use compass headings to match runway numbers, ensuring correct approach and landing direction.

Parallel runways are numbered with an L, R, or C to distinguish left, right, or center, with additional runways receiving nearby numbers.

Runway number clarity is crucial for air traffic control communication, with standardized digit pronunciation and font sizes.

The difference between magnetic north and true north affects runway numbering, as compasses point to magnetic north.

Earth's magnetic field is generated by convection currents of liquid metal, influenced by the Coriolis Effect.

The magnetic north pole's movement requires periodic updates to runway numbers, especially in areas close to the pole.

Canada has transitioned to a True North based runway numbering system, differing from the rest of the world's Magnetic North approach.

The potential for Earth's magnetic field to flip could further complicate runway numbering and navigation for pilots.

The video humorously suggests subscribing for updates in the event of a magnetic pole flip, highlighting the unpredictable nature of Earth's magnetic field.

Transcripts

While waiting on a plane  during taxi 'till takeoff,

looking out the window,

you may have noticed the giant  number numbering the runway,

say eight, which implies  seven others exist, at least,

but this is a flight out of L.O.L. Airport,

in Nevada's desert of nothing,  there's only two runways.

Which given the passenger load seems  like maybe one too many already?

What's the deal with runway numbers?

You might wonder aloud.

Oh, hello, again. Flying to Nuuk as well are you?

It is a looong flight.

So there’s tons of time for me  to tell you all about runways.

Let’s begin.

So, before you can number a runway at an airport,

you need to build the airport.

And before you can build the  airport you need to plan the 'port,

and what needs figuring first  is which way to run the way.

Pilots want runways with winds in parallel  for physics reasons that we are going to skip,

both because lift physics is something  people really like to argue about,

[aggressively] and this isn't a physics video.

Yeah, I'm recoding a runway video  right now, hope you don't mind.

But the summary is, planes take  off and land *into* the wind

because it lets them use less runway and makes  for safer and stabler landings in particular.

Now planes can land with winds unaligned but it's,

unsettling to watch these crosswind attempts  as pilots do their best to face into the wind,

while landing on a runway that does...not.

Ooofff.

So airports too want winds  running with the run way,

but the Universe is indifferent to human desires.

Wind winds as it wants. So the simple  solution in aviation early days

was to build a triangle of  runways, put up a little wind sock,

and direct the pilot to the  runway that paralleled the sock

and thus the wind.

But, as aviation grew, so did  airplanes, and thus their runways,

making the triangle trick impractical  for big, urban internationals.

But the simple sock still solved it.

See if you record when and  which way the wind sock blows

and with what wind force,

you've grown yourself a wind rose.

A clever little dataviz tool,

with the sock in the center of  compass points for orientation,

and bars colored and sized for  strength and frequency of wind.

Though it reads opposite actually  of everyone’s expectations,

with the lines showing the way  the wind blows from and not too.

Physics stuff just loves to opposite actually.

Let's just agree to avoid  physics for this video, shall we?

Wind roses' reverse readings aside,  they reveal that in most places,

most of the time, most of the wind,

mostly blows back and forth in one direction,

so that's surprisingly convenient.

Thanks indifferent Universe!

Oh, you did it for other reasons, well still,

this convenient wind happens  because wind is a current of air

transporting heat from where  there's more to where there's less.

The earth is blasted by the  nuclear heat of the sun,

with the equator getting hit hot  hardest, making hot air rise there,

as it cools out along the edge of  space, before coming back down,

creating a big scale convection current,

that repeats in a pattern all up and down.

And because the earth is a sphere that spins,

those cylindric convection  currents of air on the surface,

twist clock wise north of the  equator and counter below.

This is the Coriolis Effect.

Creating coiled currents of  air everywhere, which is cool,

but is also physics trying  to sneak back into the video,

and this isn't a physics video.

All that matters is this creates the  pretty stable pattern of trade winds,

and if you're planning a  'port, you need only know,

which way does the wind [mostly] blow.

Though at some locations the wind rose  reveals two frequent directions of wind.

So, if you want to constantly and  safestly keep open the airport,

you're going to need to run a second way.

This is why many airports have  an X or V layout, like LOL.

They're not necessarily doing double  the traffic of a one runway port,

but rather, have double the chance of crosswinds

when the tower will need to reroute pilots toward

the other alignment for safer landings.

And once you have two of something,  you need names or numbers.

Sure, you could just go with  Run 1 and Run 2 but, pro tip,

try never to use the very  first thing that comes to mind

without giving in a bit of a ponder first.

And the wind rose reveals a better  way with the compass points,

which form a circle of 360 degrees.

Starting at 0 North, East 90, South 180, West 270,

and back to North, makes it 360 as well.

These compass degrees come from ships of the seas,

because Captains and Quartermasters,

when in the vast featureless nothing,

could still count on their compass  to point toward the North Pole,

[assuming no iron hooks happened nearby]

and with north as a fixed navigational point,

could then communicate their  heading with names broadly,

East, South-east

or numbers precisely,

healm to 1-0-8.

Quite handy.

So it's no surprise these compass headings  got passed from sea ships to air ships.

Thus on the wind rose devised  plans for any airport the runway

is already aligned with navigational  numbers begging to be used,

but before grabbing the obvious one, again,

ponder for a moment,

the runway points from the  perspective of the 'port,

toward the plane.

The rather more important heading to  use is from the planes' perspective

approaching the port,

which on the plan is at the opposite end actually,

because it's what number matches the  compass in the cockpit that's critical.

Alright, this needs a couple of example airports.

Take one with a north, south runway,

when the wind blows from the north to the south,

the tower directs pilots  to approach from the south.

Meaning, they need to point the plane north,

which on their compass is  a heading of 360 degrees.

So, let's put a big 360 on that end for now,

When the winds reverse, the  tower directs pilots to approach

from the north, to fly south, which reads 180,

so let’s put a big 180 on that end as well.

Now that we've got our heading numbers,

the convention is to round them to ten

and cut off the zero for the runway number.

Because we don't need three sig  figs of precision when airports

have single digit numbers of runways and the

very stressed air traffic controllers in the tower

need to repeat precisely these  numbers hundreds of times a day

so saving syllables here really matters.

Thus when the tower tells the  plane to use runway three six,

the pilot knows they need to get south  of the airport to land facing north

and while there are like, a  million indicators in a cockpit,

the pilot can always confirm their doing it right

by reading 360 on their  ancient ancestor's compass.

This low-tech check is useful  as a fallback because a compass

can see the way even when eyes  and other equipment cannot.

As a two-runway example, an airport with a  perfect ordinal X would get numbered thusly,

north west to south east,  gives 315 for one end because

that's the way the pilot needs  to point and 135 at the other.

Round to ten, for 320 and 140,

then drop the zeros to get runways 32 and 14.

On the other side.

225 and 45, round to ten again,  drop the zeros for 23 and 5.

Now when the towers talk to the pilots,  they say each digit individually.

So, “runway two three”, because  clarity here is critical

which is also why the font  and exact size of these digits

is standardized worldwide,

though there are disagreements  between the abundant aviation agencies

as to if single digit runways like, 6,  should have a leading zero for clarity

or if that leading zero  should only be in our hearts,

which, it shouldn't be.

Anyway, that's the surprisingly good  system behind numbering these numbers,

which is always a delight to discover,

unlike some other numbers I could mention.

Though there are a couple of  wrinkles, for, think about it,

if the wind mostly blows  back-and-forth in most places,

then most big busy urban international airports  will need multiple runways in parallel.

But parallel runways have the same heading,

thus the same number under  this system which would be,

unclear for pilots to say the least.

So all the agencies assembled to agree.

If you have two parallel runways,  they will have the same number,

but add an L or an R for left and right.

If you need to construct a third  runway add a C for center too.

But with four or more, two runways  will get the correct heading number,

with L and R, but the others,

[painfully] they’re going to  get the next closest numbers,

but not exactly correct numbers.

Which is practical, I suppose, but also,

ahhhh! It’s all slightly misaligned.

[frustratingly] It’s big airports,  like it d-d-doesn’t line up.

Like, just try not to think about it  okay, just try not to think about it.

[ding dong ding]

Oh! We’re landing at Nuuk already?

Wow. Flights fly fast when  you're flapping about flying.

Time to put this knowledge to use.

Our compass heading reads 42  degrees, so round to 10 for 40,

cut the zero, and we'll be  landing on runway zero four.

And since there's only one runway  at Nuuk, it'll be perfectly aligned.

No doubt about that...ohhhh.

It's five, not four. How embarrassing.

I guess I need to delete this video now.

Hey! Why are you painting a new runway number?

You do that every few decades? That must mean.

Ohhhhhhh.

Runways numbers depend on  where the North Pole is and so,

Watch out!

There's a geography video  inside this video called,

Where is the North Pole, Really?

Okay, to find the North Pole, remember  that the Earth is a sphere that spins.

Oh sorry, we already went over that.

We draw a line about which this spin occurs,

and name each end the North and South Pole.

Starting with these poles,

we clever humans created a  square-ish co-ordinate system

for our spherical earth,

[the detailed creation of which I'm going to skip

because that's a physics story for a never time

that took hundreds of years  and needed lots of clocks,

and to make it official  thatLondonrulesandParisdrools.]

But anyway! This grid is what every  modern navigational system uses

to get around with the GPS, global  positioning, co-ordinates it gives.

But if you were to use your GPS  to direct you to the North Pole

so that you could experience the  planet rotating you in place,

as the stars circled over head,

and you pondered the scale of  the indifferent universe and

your tiny, tiny existence within it,

if you took out your compass to double  check that the GPS got the spot right.

The compass points you over the  horizon toward another north pole.

What gives, compass?

Well what did you expect? A compass is a magnet.

And magnets follow magnetic fields,  that's like their only thing.

It's not a math magnet.

Your magnet compass will take you  to the gigantic magnetic field

spewing forth from inside the earth.

So there are two north poles.

One for math, and one for magnets.

I mean, I guess if you want  to be technical about it,

there are three north poles,

because the magnetic field the  north pole of a magnet points to is,

the south pole of the earth's magnetic  field, because opposite's attract.

But look, we're just going to ignore that,

because this isn't a physics video.

And there's been enough, "oh it's the  opposite, actually" already, and yes,

I know you can define more  norths, but we're moving on.

There two norths: math and magnet.

The compass points to the magnetic north

and GPS points to the geographic north,

they don't have anything to do with each other,

but for navigation humans have used  both, one isn't better than the other.

Though, the math slash geographic  north is now often called True North,

which feels a bit like humans picking  the new one as their favorite one.

Oh, and ships of the seas have  stopped using the old magnetic north,

and now navigate with GPS using the  true north, even modern pirates,

but planes and pilots are still  love the traditional magnet north.

And we can stop thinking about this  because they’re pretty close anyway.

Although….

Isn't that kind of weird just how close the  unrelated poles are, on a planetary scale?

Earth just so happens to have  a giant magnet that sort of,

but not quite lines up with  the planet's top and bottom.

Indifferent Universe, are  these things secretly related?

And, still why would runway numbers change,

just because they're pointing at the  magnet one, but not the math one?

Oh no, there really is an unavoidable  physics video inside this geography video,

and it’s called,

Magnets, what's your deal?

Okay, we really can't cover  everything about magnets,

because, it's just so much,

but some bits of some metals such as iron,

generate around them a magnetic field.

Why? and How? were a mystery for a long time

until we discovered that if you take a wire  and run a current of electrons though it,

aka electricity, this current also  generates a magnetic field around the wire.

But weirder, if you start  with a current of electrons,

and pop them in a magnetic  field, the current will curve.

And, oh look, you've stumbled upon a clue to  one of the fundamental secrets of the universe.

Magnets and electricity are two  expressions of the same thing.

Electromagnetism!

That's why in science class  you can coil up a wire,

send a current of electricity through it,

and the whole thing becomes a magnet.

One you can make stronger and  stronger with each additional coil,

'cuz curving currents are magnets.

Which is why when you cut the  current, everything drops.

Our just iron magnets are  doing the same thing but,

you need to zoom down and down and down  and down to the atomic level to see.

Here an atom of iron has a cloud of electrons,

each electron with a charge and as they

whirl around

they create a tiny current  and a tiny magnetic field.

Zooming even closer each electron

spins

and this

spin

acts like the universes'  teeny-ist-tiny-est current

creating the teeny-ist-tiny-est electromagnet.

Okay, look,

whirl around

and

spin

don't mean what you think down here,  because in the land of quantum,

[eerily] words mean nothing, there is  only math, that we’re not gonna do.

So. Just go with it.

Anyway, in most atoms, all these  current created tiny-magnetic fields

arrange themselves against themselves  so it all cancels out to nothing,

but in a rare few atoms like iron,

does there happen to be an  imbalance that aligns and adds up.

And thus each iron atom, is a tiny  magnet, and if adjacent atoms align,

their little magnetic fields add  up, and zooming out and out and out,

if all the atoms in the iron are aligned,

then the iron acts as one big monkey-size magnet,

but deep down inside it's just  electron-sized electromagnets.

And scaling up and up and up and up  to the whole earth's magnetic fields,

it's an electromagnet all over again.

See the earth is made of parts,

the thin, perilous, cool crust on which we live,

the inner solid core that is  several thousands of degrees hot,

a middle mantle mostly solid and  relatively cool, and critically,

a ring of metal liquified by the hot hot core.

And, just as on the surface

do hot spots cause convection currents  of air to try to even the energy out,

so too does the unbelievably hot inner core  cause convection currents of liquid metal.

Metal that happens to be mostly  iron, our magnetic friend.

Thus as this mixture circles  so do all its electrons,

curving currents which gets us magnet fields baby!

Though as individual coils  it’s not very strong to start.

To get a planet sized field you'd  need to somehow stack the coils,

[gleefully] which is where the  Coriolis Effect comes back in.

For just as earth's spin causes  convection currents of air into coils,

so too does earth spin cause convection  currents of liquid metal to coil,

making the fields stronger,

turning the whole of the earth  into a giant electromagnet.

Wow! If there's one thing the  indifferent Universe loves,

it's repeating the same patters  across scales and domains.

Such austere efficiency. It’s beautiful.

Oh get back to the runways?

Ohhhhh, unlike a real  electromagnet, made of stable metal,

all that swirling liquid iron  inside earth is not...stable.

So at any moment the field can  split into multiple magnetic poles,

roam randomly, or diminish entirely before, oh my,

flipping north to south and south to north.

Which it does every couple  hundred thousand years or so,

and we have no way of predicting when.

Great.

That’ll cause some trouble and  there’s a clue that it’s coming

because the strength of Earth's  magnetic field has dropped

10% over the last couple hundred  years which is…concerning.

So, ah, if you're watching  this video after the flip.

One, take everything I said about  the magnetic north and magnetic south

and it's the now the opposite, actually, and,

two, if it's been a couple hundred  thousand years since my last upload,

don't worry, that's about normal, so,

be sure to smash that subscribe button,  so you don't miss the next video.

Oh. And hit the bell.

[begrudgingly] God I hate  that you have to do that now.

Oh right, time to wrap this up.

First, this giant electromagnet made of  liquid metal Coriolis convecting inside earth,

only semi-stably, means,  earth’s magnetic field moves.

That finishes with the physics and  means the magnet north pole moves,

and quite a lot on human time scales.

When we started measuring it  was safely inside of Canada,

but it's recently rocketed north.

Geography over so we can  finally get back to the start.

Since runway numbers are derived  from the heading on a compass,

when the Magnet North moves the runway  numbers need to change to match.

And the closer your airport is to a magnet pole,

the bigger a difference its movement makes,

and thus the more frequently  you need to update the number.

Which is why it's no surprise that Canada,

with more northern runways that anyone,

was the first to get pretty tired of  frequently repainting all her northern runways

and so changed her system to be based  on the unmoving math north instead.

But, this means when flying over her territories,

pilots can't count on their compass  to match the runways and the winds.

They can use their GPS,  assuming the battery is charged,

but, these runway numbers  are inconsistent with runways

in the {\i1}whole{\i0} rest of the world.

Now Canada thinks her system  is better and has created

an aviation agency to try to convince  all her international friends,

with airports more equatorial  and thus less of this problem,

to try and switch with her from the old and  busted Magnetic North to the new True North.

If pirates can do it, why not planes too?

Well, because it's mostly a problem for you.

And thus, there's not one system  for numbering runways, but two.

Hey guys, if you are going  to switch to True North,

best to get it done before  the poles flip. Just sayin'.