Find a more recent prediction of the cicrumference of the earth and compare it to the value given by Eratosthe
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Kenneth R. Lang's "Astrophysical Data: Planets and Stars" gives the polar radius as 6356.755 km = 39,940.7 km circumfrence and the equatorial radius as 6378.140 km = 40,075.0 km circumfrence and using the mean radius of 6371.0 km gives a polar circumfrence of 40,0030.2 km.  Take your pick.  Whatever Eratosthenese used as a standard, it was his methodology that was the thing that made him memorable.  When the French first established the length of the meter and hence the kilometer, they were off in their estimate of the length of a meridian too.
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I hear rumors of something called Earth 2.0, subtitled "The New Heaven and the New Earth."\n\nThen again, those rumors have been going around for about two thousand years so I wouldn't invest any money in it if I were you.
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this should help             http://earth.google.com/
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try google earth, it's a program that you download and run but it gets updated as you move around the planet!
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I agree with the first answer.  That's nearly impossible to predict.  I have this book from the 70's that tried to predict where we would be by now and they had moon bases, flying cars, giant space stations, etcetra.  So they couldn't even figure out where we would be in 30 years let alone 1000.
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Hint: The Earth revolves 7.5 degrees every 30 minutes.
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Go to GoogleEarth.com
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"If the earth were a hundredth of an inch closer to the sun, we would burn to death and if it were one hundredth farther from the sun, we would freeze to death"\n\nHA HA HA HA HA HA LOL ROTFL\n\nThat's what you get for reading fairy tale books instead of science books... actually the earth is at 152 million km from the sun at aphelion and 148 million at perihelion (6 million km closer) ... get a clue!!
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circumference = pie times diameter\nradius is half of the diameter\n\nso if you have either the circumference or the diameter, you can figure it out.
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You could make a model of the solar system.  Use different sized Styrofoam balls for the planets.
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go to http://earth.google.com
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The ancient greeks knew the earth was round.  They knew it because they watched ships sail off.  Someone with good eyes could see that the ship was going over the horizon, the bottom of the ship dissappeared first.  Also, they knew that an eclipse of the moon showed the shadow of the earth on the moon.  Erastothenes calculated the diameter of the earth in about 200 bc.  He was accurate to about 3%.
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Have you ever tried Google Earth, it is a good program that might let you get the circumference of countries.
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the rotation of the earth and the semisic activity
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sorry i am no good at math, but this may help:\nhttp://www.fourmilab.ch/earthview/pacalc.html
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Either use volumes of revolution or compare cross sections of the sphere and a cylinder with a couple of cones removed. The latter is how Archimedes did it.
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circumference= 2*r*pi\nwhere r is the radius and pi is approximately 3.14