Eratosthenes 2010-2011

HôChiMinhCity Vietnam

Wednesday 23 June 2010 by perbosc

 Ho Chi Minh City Amateur Astronomy Club- HAAC

Résults on HAAC forum

  • Founded by some people who loved astronomy in Ho Chi Minh city 19/5/2007. At now, the club is supported by Vietnam Astronomy and Space Association and Ho Chi Minh City Institute of Physics.
  • At now the club is the biggest amateur astronomy club in Vietnam with more than 100 members in Ho Chi Minh city. Besides, nearly hundreds of members participate and discuss online through our website www.thienvanhoc.org. More than 60 percent of members are students and pupils.
  • HAAC: always holds a lot of events such as astronomy observations, basic knowledge, hand-made telescopes. Coordinate with some schools to widespread astronomy in Vietnam.

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 The result in HCM City (20 June)

  • The pole length =130cm, shadow length = 29.1cm
  • Local noon at 11:53AM
  • Angle n = arctan (29.1/130)= 12.61754 degree
  • Distance from hcm to Tropic of Cancer (D) is 1409.17 km (10.769N)
  • Earth’s circumference =360* D/n= 40206 km

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 The result in HCM City (21 June)

  • The pole length =130.5cm, shadow length = 29.3cm
  • Local noon at 11:55AM
  • Angle n = arctan (29.3/130.5)= 12.65426 degree
  • Distance from hcm to Tropic of Cancer (D) is 1409.17 km (10.769N)
  • Earth’s circumference =360* D/n= 40089.35 km

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 Result in another province in VN

Hà Nội: 21.033 N, Local noon is 11:58AM, D= 268.94 km, n= arctan (5.7/100) = 3.26°

  • Earth’s circumference =360* D/n=?

Đà Nẵng: 16.07N, Local noon at 11:57AM, D=822.38 km, n=arctan(7.5/58)=7.37 degree\

  • Earth’s circumference =360* D/n=40181.15 km

Bảo Lộc: 11.5N, D= 1350.27 km,n= arctan(17.5/83.4)= 11.85 degree, distance to tropic of cancer is 1328.04 km,

  • Earth’s Circumference = 40345 km

Thanh Hóa: 19.81 N, D= 402.52 km, n= arctan (6.2/99)= 3.583619 degree

  • Earth’s circumference =360* D/n= 40436 km

Đồng Tháp: 10.35N, D=1451.03 km, n=arctan(27.1/116.9)=13.05187676 degree

  • Earth’s circumference =360* D/n=40022.658 km

Playku: 13.99N, D= 1031.52 km,n= arctan(17.5/83.4)= 11.85 degree

  • Earth’s circumference =360* D/n=31 430 km

Bảo Lâm:11.7N, D= 1313.04 km,n=arctan(17.5/83.6)=11.823 degree

  • Earth’s circumference =360* D/n=39980.92 km

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 Result in Method 2

  • Reason: Thanh Hoa and Dong Thap have the same longitude 105.7 East
  • n1 in Thanh Hoa at local noon is 3.583619 degree
  • n2 in Dong Thap at local noon is 13.05187676 degree
  • Distance (D) between two locations above is 1048.51 km
  • n= n2-n1 = 9.46825776 degree
  • Earth’s circumference =360* D/n=39886.215 km
  • Local noon at one place: the time which have shortest shadow length or the time between sunrise and sunset

 Achievement

  • Help participants know more about Earth’s sphere, Tropic of Cancer, sunlight’s shadow on earth, principles for computing and explain some equations.
  • The way Eratosthenes uses to determine the Earth’s Circumference thousands years ago.
  • Participants can compute Earth’s Circumference themselves by measured the angle of elavation of Sun in Summer Solstice.

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