Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: thedoc on 01/08/2013 14:37:54
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Camilla asked the Naked Scientists:
If the world is a globe, why is it that people in eg Australia do not feel they are upside down?
Camilla
What do you think?
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As a person in Australia, I can assure you that the Earth's gravitational field pulls me quite firmly towards the center of the Earth with an acceleration of about 10 m/s2.
It also pulls all of the rocks and dirt, trees and buildings in the same direction with the same acceleration.
So when I stand in a field and look around me, the field appears flat and everything I see on Earth is "the right way up".
When I visited Europe, the Earth's gravitational field still pulled me quite firmly towards the center of the Earth with an acceleration of about 10 m/s2, and everything I could see on Earth still appeared "the right way up".
It is only when you are in a spaceship (or looking at a globe of the world) that you can see that for people who are at widely separated parts of the Earth, the center of the Earth appears to be in different directions. But for each of these people, the center of the Earth is still "down".
In practice, the main side-effects of living at the antipodes are:
- Migratory birds & animals tend to head North for the Winter
- Moss grows better on the South side of the trees.
- Cyclones/Tornadoes/Hurricanes spin the other direction when viewed on a weather-map
- It gets 2 hours easier (or harder) to phone people in the other hemisphere when Daylight Savings starts.
- December is the middle of Summer, so Australians tend to go swimming at the beach or have an outside BBQ for Christmas
- We see a different set of stars, so astronomy instructions that start with "look for Polaris" don't work for us.
So visitors to Australia from the Northern hemisphere are more likely to notice differences due to North/South or Summer/Winter, rather than Up/Down. (Although visitors from North America or Continental Europe may also experience some Left/Right confusion on the roads...)
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People often get lost in the outback when quite close to roads could this have something to do with the sun going round the wrong way ?
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People often get lost in the outback when quite close to roads could this have something to do with the sun going round the wrong way ?
Everything still rises in the east and sets in the west wherever you are in the world.
The moon may appear upside down as compared to a northern latitude observer, but it rises in the east and sets in the west still.
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People often get lost in the outback when quite close to roads could this have something to do with the sun going round the wrong way ?
Yes that is part of the story. When I visited Britain some years ago, I got lost in Richmond Park because I assumed at 11 am that South would be to the left of the sun (as North is at home)
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At dawn and sunset, it is pretty clear which directions are East & West - the Sun is right near those compass points. This works in both hemispheres (but not so well in polar regions).
However, I too have had East/West confusion when traveling in the other hemisphere on a clear day around noon.
At noon, you can't tell East or West directly, because the Sun is not near the horizon. However, if you turn to face the Sun at noon:
- In Australia, East is on the right, and West is on the left.
- In North America, East is on the left, and West is on the right.
The first time I encountered this, it gave me quite a sense of vertigo.
I found my navigation was better on cloudy days (and even better when they started fitting hire cars with GPS!).
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And I thought all Australians walked on their hands
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Ffarm3.staticflickr.com%2F2263%2F5761847215_a554a17258_z.jpg&hash=857a14c7b1f6e85018af7c515f4134f1)
As mentioned, gravity pulls towards the center of the Earth. If it didn't, rocks and mountains would not stay put either. The Earth, of course, spins in the same direction for everyone, but despite what turns out to be a very fast speed (1,674 km/h at the equator), it seems stationary and flat. This would be true essentially everywhere, although the biggest differences might be viewed at the poles.
Of course, due to the axial tilt, seasons are flopped between the North and South.
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If the world is a globe, why is it that people in eg Australia do not feel they are upside down?
Our sense of up and down comes from the effects of the force of gravity on the body, namely its dirction. Since the direction of the force of gravity on a person is always in the direction towards the cemter pf the earth then down will always be felt as the direction from towards the center of the earth.
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Clifford - you had the photo upside down!
This Australian was supporting the Earth...
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They all think they do. And the sun shines from their nether regions. That's why we Poms had to invent cricket, rugby and tennis.
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Ahhh.
So Atlas (http://en.wikipedia.org/wiki/Atlas_(mythology)) was Australian?
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Ahhh.
So Atlas (http://en.wikipedia.org/wiki/Atlas_(mythology)) was Australian?
Atlas was a croweater: http://www.atlas.sa.gov.au (http://www.atlas.sa.gov.au)
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The question would be rather if it does feel different in Australia than in Euorope or whatsover. North isn't up, it is only up on the map. When it wasn't established, there were other benchmarks (like a castle, this big tree, the mountains or whatever) and putting a few maps together would be quite a puzzle.