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Science project - showing the earth is round

 
 
Reply Thu 15 Sep, 2005 10:26 am
My niece needs a science project and I've promised to help her. She wants to show the earth is round. Anyone have any suggestions?

LLH
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Type: Discussion • Score: 1 • Views: 1,318 • Replies: 16
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DrewDad
 
  1  
Reply Thu 15 Sep, 2005 10:55 am
Measure the angles of shadows at two separate locations at the same time. Preferably on the same lattitude.
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raprap
 
  1  
Reply Thu 15 Sep, 2005 09:17 pm
The shadow of the earth on the moon during a lunar eclipse.

Rap
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rosborne979
 
  1  
Reply Thu 15 Sep, 2005 09:40 pm
I think I read that Galilleo used to view ships on the horizon with his telescope and noticed that the masts appeared first, then then the rest of the ship.
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markr
 
  1  
Reply Thu 15 Sep, 2005 10:40 pm
Unfortunately, these only show that the earth is not flat (although in Rap's case, it could be a flat disk).
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vinsan
 
  1  
Reply Fri 16 Sep, 2005 03:05 am
Another way
markr wrote:
Unfortunately, these only show that the earth is not flat (although in Rap's case, it could be a flat disk).


Hey LordoftheLeftHand ,

You nice is a kid to whome the earlier evidences are sufficient for science experiment but if you really need undoubted evidence that earth is round then it can be seen the constellations shift relative to the horizon as you move north and south around the globe, something that could only happen if you were standing on a sphere (not possible with Flat Disc or curved unspehrical surfaces)
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nitindandriyal
 
  1  
Reply Fri 16 Sep, 2005 03:18 am
Now, do one thing go to the north pole, from there start moving towards South for about 200 miles, Stop, now turn to your right again move 200 miles, Stop & now again turn to your right and again move 200 miles, U will feel nice to know that you are back to the North pole.

How does this happen? hm.... Earth is a sphere
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nitindandriyal
 
  1  
Reply Fri 16 Sep, 2005 03:18 am
Now, do one thing go to the north pole, from there start moving towards South for about 200 miles, Stop, now turn to your right again move 200 miles, Stop & now again turn to your right and again move 200 miles, U will feel nice to know that you are back to the North pole.

How does this happen? hm.... Earth is a sphere
0 Replies
 
nitindandriyal
 
  1  
Reply Fri 16 Sep, 2005 03:18 am
Now, do one thing go to the north pole, from there start moving towards South for about 200 miles, Stop, now turn to your right again move 200 miles, Stop & now again turn to your right and again move 200 miles, U will feel nice to know that you are back to the North pole.

How doesthis happen? hm.... Earth is a sphere
0 Replies
 
nitindandriyal
 
  1  
Reply Fri 16 Sep, 2005 03:18 am
Now, do one thing go to the north pole, from there start moving towards South for about 200 miles, Stop, now turn to your right again move 200 miles, Stop & now again turn to your right and again move 200 miles, U will feel nice to know that you are back to the North pole.

How doesthis happen? hm.... Earth is a sphere
0 Replies
 
g day
 
  1  
Reply Fri 16 Sep, 2005 04:09 am
Hold a ruler at arms length to the horizon to show the horizon is curved - repeat this anywhere/every you care to sample on Earth - showing the world is curved with a fairly constant curve - and the only shape that fits this description is a sphere
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DrewDad
 
  1  
Reply Fri 16 Sep, 2005 11:05 am
nitindandriyal wrote:
Now, do one thing go to the north pole, from there start moving towards South for about 200 miles, Stop, now turn to your right again move 200 miles, Stop & now again turn to your right and again move 200 miles, U will feel nice to know that you are back to the North pole.

How doesthis happen? hm.... Earth is a sphere

Do we have to do it four times? Very Happy
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farmerman
 
  1  
Reply Fri 16 Sep, 2005 11:40 am
measure the lengths of shadows at 2 or 3 fixed points at solar noon on the summer solstice. You must know your lat and long. You should be at l;east 1 degree apart for your stations (anywhere from 40 to 70 miles for people NOT at the poles)


Gather all the stationary data from NASA about several geosynchronous satellites. From their orbits you can resolve the shape of the geoid.

Gather up data from USGS on tectonic plate resolution. You will have coordinates in polar trig and can compute the center of the axis of rotation of a specific plate by knowing its position through time. Thats all available through many U's
Id suggest using the data for the Himalayas, whose center axis of rotation is computed tobe somewhere around Cairo.

As a project, only number A. requires any field work , and even here, if you have some reliable relatives you can get them to measure at their homes (assuming they live at or greater than 66 miles). All the others can be done freom a desk with a computer hookup and a bunch of links.


There is a real simple way. Convert all sunrise times for a single day to GMT. Then figuring that it takes the sun 24 hours to traverse the entire world, convert those times to any convenient metric to prove that it ISNT round , you can only make it work by thinking in degrees. I may be wrong on this last one

Use NOAAs sunrise sunset formulae to compute the sunrise sunset for specific latitudes. This data is available and it can only resolve itself as an oblate sphere.
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LordoftheLeftHand
 
  1  
Reply Fri 16 Sep, 2005 03:22 pm
Thanks for all the tips. We'll use a few of these together I think.

LLH
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Steve 41oo
 
  1  
Reply Fri 16 Sep, 2005 03:31 pm
well you could shoot off into space and take a photograph but I suppose thats too simple

Pythagoras i believe satisfied himself the earth was round by measuring the time taken for the sun to strike the bottom of wells at fixed distances apart.

Alternatively you could sail off into the sunset, keep going, and some while later arrive back at the place you set off from...

but easier to shoot off into space as i said
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owl
 
  1  
Reply Sat 17 Sep, 2005 07:29 pm
The best way seems to be the shadow of the earth on the moon but there are 2 variations on this.

The first is to observe that the full moon occurs when the sun and moon are opposite each other and the partial moon occurs as the moon enters the earth's shadow. It would be interesting to photograph the moon on successive nights as the phase changed and correlate this with the time of moonrise & sunset.

The second is to observe a film of a eclipse of the moon when the moon disappears into the earth's shadow and emerges later. Note that this is an eclipse of the moon not the eclipse of the sun which is more dramatic.
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raprap
 
  1  
Reply Sun 18 Sep, 2005 01:41 am
Several already hit upon some of the polar geometric properties but there another not yet mentioned. That is measuring the sum of the angles of a triangle.

Start measuring the angles of progressively larger similar triangles. Initially, when small, the triangle's vertex angles will sum to 180 degrees because the surface of the globe on a micro scale approaches a plane. However; as the triangle grows progressively larger straight lines turn into polar geodesics (great circles) and the sum of the triangle angles increases to more than 180 degrees.

Rap
0 Replies
 
 

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