Transparent Earth

Norkie

Norkie

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I'm not sure what made me dream this question up? I was watching the ISS Earth Viewing experiment on t'internet and I thought, "Hmm, who can I ask?"

If the world were semi transparent, so you could see through it but were still be able to identify continents, how big would Australia appear if viewing from England?

A4 sized, A3 perhaps?

Also, what continent is directly opposite us, is it Australia, or New Zealand maybe?
 
Pretty much open water directly opposite the UK (IIRC!) Closest sizeable land mass is South Island, NZ.
 
Fear not, the answer is here...:)

You could also understand why objects seem smaller from a certain distance and further and why they look bigger when they are to close as this:

The retina has in humans a mean distance from the lens of in the eye about 0.02 metres. Thus, from simple trigonometry, we have:

I=(QP)O

, where O is the real size of the object, I is the size of the idol at the lens, P is the distance between the object and the observer and Q is the distance of the idol, that is the 0.02 m we mentioned before.


Thus, the distance where the object seems to the observer to its real size is where the O is equal to I, that is

P=Q=0,02m

Hope this helps.
 
Norkie said:
If the world were semi transparent, so you could see through it but were still be able to identify continents, how big would Australia appear if viewing from England?

A4 sized, A3 perhaps?
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Unfortunately that's not a meaningful question. You need to specify how far from your eyes the sheet of paper is. An A4 sheet stuck on the end of your nose would take up pretty much all of your field of view. An A4 sheet on the wall at the far end of the room wouldn't.
 
StewartR said:
Unfortunately that's not a meaningful question.
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It would be meaningful to ask how big a sheet of paper you would need to cover Australia if you held it at a specified distance (eg arm's length, say 1 metre). Alternatively it would be meaningful to ask how far away you would have to hold a sheet of paper of a specified size (eg A4 or A3) in order for it to cover Australia.
 
I think it’s a question of perspective.

Speaking of which, I think it amazing that the sun and moon (given their differing size and distance from us) appear exactly the same size to us from our perspective here on earth.
 
That's because Sol and Luna came to an agreement when they tricked Gaea into hosting mankind - she's been regretting taking them on for years! :p
 
So anyway, I used Google Maps to find the latitude and longitude of Birmingham (approximately the centre of England) and Ayers Rock (approximately the centre of Australia). Then I used a great circle distance calculator to determine the great circle distance between them, which turns out to be 14,990 km. Then I used the relationship

ED = 2 * R * sin ( 0.5 * GCD / R )

where ED is the Euclidean distance (straight line through the earth), GCD is the great circle distance, and R is the radius of the earth. Substituting GCD = 14990 km and R = 6371 km, we get ED = 11,764 km.

Now Australia is 4,000 km from east to west and 3,860 km from north to south. (That might sound a bit surprising - I'd have though the east-west dimension was considerably longer than the north-south dimension - but if you look at a map you'll see that the north of Queensland to the south of Tasmania is a long way!)

So we have a continent which is 4,000 x 3,860 km, and we're viewing it from a distance of 11,764 km. If we scale all those dimensions proportionately, it's equivalent to a piece of paper measuring 218 x 210 mm, viewed from a distance of 640 mm. In other words, Australia seem through your transparent Earth will just about be covered by a sheet of A4 paper held at arms length.
 
Norkie said:
I'm not sure what made me dream this question up? I was watching the ISS Earth Viewing experiment on t'internet and I thought, "Hmm, who can I ask?"

If the world were semi transparent, so you could see through it but were still be able to identify continents, how big would Australia appear if viewing from England?

A4 sized, A3 perhaps?

Also, what continent is directly opposite us, is it Australia, or New Zealand maybe?
Click to expand...

Sorry to rain on your parade but you won't see through it to identify continents on the other side.

If the ground and most of the mantle all the way down were semi transparent enough to see through when viewing from the ISS, you would end up seeing the outer core which is very hot fluid moving around a even more hotter and brighter solid inner core, and the outer core is spinning around the inner core at a alarming speed.

I don't know of any suitable analogy to use, scientist would be better people to ask for an example. But if I had to take a wild guess, I would have to say, it is like trying to look through a fish tank filled up with bright yellow water that is moving around like a fast flowing river, and in the middle of the fish tank is a very bright waterproof light. It'll be hard to see what is on the other side of the fish tank.
 
StewartR said:
So anyway, I used Google Maps to find the latitude and longitude of Birmingham (approximately the centre of England) and Ayers Rock (approximately the centre of Australia). Then I used a great circle distance calculator to determine the great circle distance between them, which turns out to be 14,990 km. Then I used the relationship

ED = 2 * R * sin ( 0.5 * GCD / R )

where ED is the Euclidean distance (straight line through the earth), GCD is the great circle distance, and R is the radius of the earth. Substituting GCD = 14990 km and R = 6371 km, we get ED = 11,764 km.

Now Australia is 4,000 km from east to west and 3,860 km from north to south. (That might sound a bit surprising - I'd have though the east-west dimension was considerably longer than the north-south dimension - but if you look at a map you'll see that the north of Queensland to the south of Tasmania is a long way!)

So we have a continent which is 4,000 x 3,860 km, and we're viewing it from a distance of 11,764 km. If we scale all those dimensions proportionately, it's equivalent to a piece of paper measuring 218 x 210 mm, viewed from a distance of 640 mm. In other words, Australia seem through your transparent Earth will just about be covered by a sheet of A4 paper held at arms length.
Click to expand...
Aha so a piece of A4 at arms length, excellent thank you (y)
 
Major Eazy said:
Sorry to rain on your parade but you won't see through it to identify continents on the other side.

If the ground and most of the mantle all the way down were semi transparent enough to see through when viewing from the ISS, you would end up seeing the outer core which is very hot fluid moving around a even more hotter and brighter solid inner core, and the outer core is spinning around the inner core at a alarming speed.

I don't know of any suitable analogy to use, scientist would be better people to ask for an example. But if I had to take a wild guess, I would have to say, it is like trying to look through a fish tank filled up with bright yellow water that is moving around like a fast flowing river, and in the middle of the fish tank is a very bright waterproof light. It'll be hard to see what is on the other side of the fish tank.
Click to expand...
It's only a theoretical question, I'm short sighted so I couldn't see it anyhow :cool:
 
Norkie said:
It's only a theoretical question, I'm short sighted so I couldn't see it anyhow :cool:
Click to expand...

Okay, you win.

Well, Earth could also mean soil, and world could also mean the lands, you didn't say anything about it being a transparent planet. :)
 
[
Major Eazy said:
Sorry to rain on your parade but you won't see through it to identify continents on the other side.

If the ground and most of the mantle all the way down were semi transparent enough to see through when viewing from the ISS, you would end up seeing the outer core which is very hot fluid moving around a even more hotter and brighter solid inner core, and the outer core is spinning around the inner core at a alarming speed.

I don't know of any suitable analogy to use, scientist would be better people to ask for an example. But if I had to take a wild guess, I would have to say, it is like trying to look through a fish tank filled up with bright yellow water that is moving around like a fast flowing river, and in the middle of the fish tank is a very bright waterproof light. It'll be hard to see what is on the other side of the fish tank.
Click to expand...

What is your point????? When the original poster specified the theoretical conditions of their question.


Norkie said:
If the world were semi transparent, so you could see through it but were still be able to identify continents, how big would Australia appear if viewing from England?
Click to expand...
 
Australia is about 20% wider than the moon. The diameter of the earth is about 1/32 of the distance to the moon.

So Australia would look a lot bigger than the moon. Somebody could use maths to work out how much bigger - I suspect is has more to do with square roots than the size of your eye.
 
PS: About the link supplied by @Jimmy_Lemon

To settle the question of if Australia is supposed to be on the other side of the planet from England, I figure it would be a lot easier to find out what is on the other side of the Earth from Australia.

It seems all that U-Boats attacks on convoys sailing between USA and UK in WWII, could easily cover the whole map of Australia and still overfill the map too.
 
JonathanRyan said:
Yeah, I couldn't figure out what you were doing with a great circle distance. Isn't that something like the shortest distance from point to point on a spheroid?
Is that to cope with the fact that it isn't really opposite us? I'm going to guess that with all the other roundings that's basically irrelevant.
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You're completely correct. The difference between Australia's actual location and the precise antipodean point is small enough to get lost in the "at arm's length" simplification which I put in my answer. However I'm a mathematician which means I'm basically lazy. I reasoned that if I start with the GCD, my solution readily generalises to situations where the two points aren't even nearly opposite. When somebody asks how big, say, Japan would appear though a transparent earth - I've already done the work.

JonathanRyan said:
Which reminds me of this excellent project - https://io9.gizmodo.com/the-tale-of-the-epic-struggle-to-make-an-earth-sandwich-5823320
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Nice one!
 
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