Your bits of totally useless geographical trivia please...

[backontrack]

I suppose someone arguing a circle is a straight line makes a change from arguing black is white, as often happens on this forum

A perfect circle or a perfect straight line are by definition impossible to generate - for now, anyway.

In the case of the former, it may depend on when the Heptapods arrive.

 

[Bromley boy]

Argh... terminology and frames of reference - the cause of many a great argument.

I didn't mean compass heading (which you correctly point out will change for any great circle other than the equator) but rather rotation around the Z (up/down) axis of the boat/plane/whatever.

So, let me rephrase the question: by how much do you rotate in yaw while following a great circle route?

I'm off out... To be continued later!

 

[Dai Corner]

Surely a straight line between two points on the Earth's surface would have to go through the Earth?

Love how we've gone from geography to geometry

 

[backontrack]

Surely a straight line between two points on the Earth's surface would have to go through the Earth?

Love how we've gone from geography to geometry

If there's a circle in the forest and nobody's there to see it, it would still get more votes than UKIP.

 

[DaleCooper]

Surely a straight line between two points on the Earth's surface would have to go through the Earth?

Quite right, you didn't need the question mark.

Love how we've gone from geography to geometry

Not much difference really:

geography - from Greek "earth writing".
geometry - from Greek "earth measuring"

 

[Cowley]

We seem to be going around in circles. Has anyone got any more interesting facts? I was enjoying them.

 

[backontrack]

I think Causey Pike is the only Lakeland fell where you can see both 'cats' - Catbells and Catstycam - at the same time.

(The one in my avatar is Pillar I think. I took it by Innominate Tarn on Haystacks.)

 

[Howardh]

We seem to be going around in circles. Has anyone got any more interesting facts? I was enjoying them.

Certainly. Pheasant Island is under joint sovereignty of Spain and France; they run it for 6 months each. It has a population of 0.

 

[Cowley]

Certainly. Pheasant Island is under joint sovereignty of Spain and France; they run it for 6 months each. It has a population of 0.

I had to look that up. I don't know what I was expecting but it's not very big

 

[najaB]

Certainly. Pheasant Island is under joint sovereignty of Spain and France; they run it for 6 months each. It has a population of 0.

Sovereignty over Hans Island is similarly disputed between Denmark (via Greenland) and Canada - the Canadian and Danish military alternately 'invade' the island and claim it for their respective governments. Usually by taking down the other side's flag and leaving a bottle of whiskey or schnapps.

 

[Calthrop]

Certainly. Pheasant Island is under joint sovereignty of Spain and France; they run it for 6 months each. It has a population of 0.

But do any pheasants live there?

 

[DaleCooper]

But do any pheasants live there?

... or pheasant pluckers?

 

[DynamicSpirit]

Election boundaries aren't always the same as district boundaries.

I did specifically select London Borough council boundaries on the OS map I screenshotted. Is there some reason to think that doesn't give actual boundaries? (I'm afraid I couldn't figure out from the openstreetmap image what was there that showed boundaries).

 

[DynamicSpirit]

Yes, it's curved in three-dimensional space. However, in two-dimensional space (which the surface of the Earth is at human scale) if it were possible to walk on water, etc. you would turn neither left nor right when following a great circle route.

I'm sure there's a word that could be used to describe a line that can be followed without a change of heading...

geodesic is the word you're looking for.

No, but if you were following a great circle arc, you would be following the curvature of the earth. If you were following a straight line you would end up in space as the earth curved away beneath your course!

The shortest distance between two points over the surface of a sphere, or an approximate sphere in the case of the earth, is a non-straight great circle. Not a straight line.

In a way, it's a matter of perspective. You think of a straight line as heading out into space because you're considering all of 3D space to be the 'universe' that the line exists in.

But think of it instead from the point of view of a 2-dimensional being that is incapable of perceiving anything other than the surface of the Earth. As far as that being is concerned, space outside the surface of the Earth does not exist. The surface of the Earth is all that there is. What we perceive as a great circle this being would perceive as a straight line.

By the way this isn't just theory: General relativity theory tells us that the space (or more accurately the space-time) that we live in really is curved, in a way that we can't perceive directly with out senses. Speaking very, very, crudely and simplistically, the actual Universe that we live in really isn't that dissimilar from the surface of the earth in some ways!

 

[Calthrop]

But do any pheasants live there?

... or pheasant pluckers?

Back into your study, Dr. Spooner...

 

[MotCO]

And the Black Isle isn't an island.

Nor is the Isle of Grain, Isle of Dogs, Isle of Ely...

 

[Cowley]

Nor is the Isle of Grain, Isle of Dogs, Isle of Ely...

And Purbeck

 

[Dai Corner]

And Purbeck

Or Barry

 

[Barn]

By the way this isn't just theory: General relativity theory tells us that the space (or more accurately the space-time) that we live in really is curved, in a way that we can't perceive directly with out senses. Speaking very, very, crudely and simplistically, the actual Universe that we live in really isn't that dissimilar from the surface of the earth in some ways!

Indeed. The surface of the Earth is a good way of understanding gravity in general relativity.

Imagine that you can only think in 2D and consequently do not know that the Earth is a 3D sphere (but you do have access to a good compass). You and your friend stand 50 metres apart on the equator and both walk due north. As far as you can tell, you're walking parallel to each other. But as you continue northwards you end up getting, strangely, closer and closer together until, as you approach the north pole itself, you're almost touching each other. You are sure that you have been walking on the same heading and can't understand why you have got closer together.

It appears that some strange force has pulled you together. In fact, you've been walking across a sphere. Moving up in dimensions, gravity can seem like that strange force when we think of the world as 3D, but if we were able to picture the universe in 4D, the force might really be simply due to the curvature of space-time in that fourth dimension.

 

[341o2]

Back into your study, Dr. Spooner...

No, not until I have had a few jars at my local, the Fish and Duck

 

[fowler9]

Birkenhead in Auckland is really not very similar to Birkenhead on the banks of the Mersey. Also Southport on the Gold Coast in Australia is not very similar to Southport on Merseyside, they are both at the north end of the regions they are part of though so that is something.

 

[DaleCooper]

No, not until I have had a few jars at my local, the Fish and Duck

My local is "The Cooking Fat".

 

[Rick1984]

Nor is the Isle of Grain, Isle of Dogs, Isle of Ely...

Ely however was an Island.

 

[61653 HTAFC]

Birkenhead in Auckland is really not very similar to Birkenhead on the banks of the Mersey. Also Southport on the Gold Coast in Australia is not very similar to Southport on Merseyside, they are both at the north end of the regions they are part of though so that is something.

The only "New World" places named after Huddersfield are a hunting/trekking lodge in the wilds of Canada, and a small farmhouse on Jamaica.

 

[Cowley]

The only "New World" places named after Huddersfield are a hunting/trekking lodge in the wilds of Canada, and a small farmhouse on Jamaica.

My stepbrother from Exmouth in Devon flew across the world and married his wife in Exmouth in Western Australia.
(Show off )

 

[najaB]

The only "New World" places named after Huddersfield are a hunting/trekking lodge in the wilds of Canada, and a small farmhouse on Jamaica.

I believe that the greatest distance between a UK city and it's namesake is Perth to Perth (9120 miles) Newcastle to Newcastle 10440 miles Devonport to Devonport (Tasmania) 10,890 miles Oban to Oban (New Zealand) - 11,730 miles. (I give up!)

 

[DaleCooper]

I believe that the greatest distance between a UK city and it's namesake is Perth to Perth (9120 miles) Newcastle to Newcastle 10440 miles Devonport to Devonport (Tasmania) 10,890 miles Oban to Oban (New Zealand) - 11,730 miles. (I give up!)

Do towns count? Christchurch UK to Christchurch NZ - 11880 miles.

 

[Howardh]

At 8', and not surprisingly called a Mount, the Maldives has the world's lowest highest point. Mt. Villingili.

Wonder when they'll build a cable-car to the top??

 

[AlterEgo]

I believe that the greatest distance between a UK city and it's namesake is Perth to Perth (9120 miles) Newcastle to Newcastle 10440 miles Devonport to Devonport (Tasmania) 10,890 miles Oban to Oban (New Zealand) - 11,730 miles. (I give up!)

There's a Newcastle in New Zealand IIRC.

 

[najaB]

Do towns count? Christchurch UK to Christchurch NZ - 11880 miles.

There's a good example of how the Earth being a globe leads to non-intuitive results. Oban (UK) is further North than Christchurch (UK) and Oban (NZ) is further south than Christchurch (NZ). So the natural assumption is that Oban to Oban would be longer than Christchurch to Christchurch.