AST101H5 Study Guide - Final Guide: South Magnetic Pole, Ancient Greek Astronomy, Solar System
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Ho(cid:449) (cid:862)(cid:271)ig(cid:863) is the ola(cid:396) (cid:455)ste(cid:373): wo(cid:396)ds like (cid:862)(cid:271)ig(cid:863) do(cid:374)(cid:859)t (cid:272)o(cid:374)tai(cid:374) e(cid:374)ough i(cid:374)fo(cid:396)(cid:373)atio(cid:374). We ha(cid:448)e to use numbers: don(cid:859)t memo i)e numbe lea n how we know the numbe !!, earths radius= 6,378km, earths diameter= 2 x radius= 12,756km, always remember units!!! Numbers in ratios: ratios compare two numbers. One value is a multiple or fraction of another (cid:448)alue, (cid:373)o(cid:396)e i(cid:374)fo(cid:396)(cid:373)atio(cid:374) tha(cid:374) the (cid:862)pu(cid:396)e(cid:863) (cid:374)u(cid:373)(cid:271)e(cid:396): atio do(cid:374)(cid:859)t (cid:272)o(cid:374)tai(cid:374) u(cid:374)its. Radius of moon/ radius of earth = 1738km/6378km =0. 272. Numbers in scientific notation: nu(cid:373)(cid:271)e(cid:396)s (cid:272)a(cid:374) (cid:271)e (cid:862)ast(cid:396)o(cid:374)o(cid:373)i(cid:272)all(cid:455)(cid:863) la(cid:396)ge o(cid:396) s(cid:373)all, it is easier to write very large (and very small) numbers in scientific notation, example: the distance from earth to sun. 150000000 km => 1. 5 x 108 km (appendix a1 explains the notation) Numbers using new units: familiar units, such as km, are too tiny for astronomy, invent new units that are more appropriate, example: astronomical unit= au, average distance between earth and sun, 150,000,000km.
