回复：一次流星雨能有多少人看到？

来源: wxcfan123 于 2011-08-13 12:05:27 [] [旧帖] [给我悄悄话] 阅读数 : (271 bytes)
回答: 一次流星雨能有多少人看到？ 由 贫论员 于 2011-08-09 20:20:12

Let r be the hight of the star. R is the radius of the earth. A is the area of the spherical cap and B is the area of the the surface of the earch. It is not difficult to get

A/B = r/(2(R+r)). Take r = 50, get A/B = 0.0038... r = 40 get A/B = 0.00310...

所有跟帖： 

• r/2(R+r)=about 4%o.Please note the tangent line. -jinjing- ♀ 给 jinjing 发送悄悄话 (0 bytes) () 08/13/2011 postreply 14:27:31

• 0.4%? -贫论员- ♀ 给 贫论员 发送悄悄话 (0 bytes) () 08/15/2011 postreply 12:07:10

• Yes.Only estimat,we don't know the time,it has relation with the -jinjing- ♀ 给 jinjing 发送悄悄话 (0 bytes) () 08/15/2011 postreply 16:33:51

• It has relation with the rotation of the Earth. -jinjing- ♀ 给 jinjing 发送悄悄话 (0 bytes) () 08/15/2011 postreply 16:50:46

• sorry, youare right. -jinjing- ♀ 给 jinjing 发送悄悄话 (0 bytes) () 08/13/2011 postreply 14:31:26

• 结果这么clean啊！怎么推倒出来的？ -贫论员- ♀ 给 贫论员 发送悄悄话 (0 bytes) () 08/15/2011 postreply 11:42:51

• 哦，原始推导居然用了曲面积分。 -贫论员- ♀ 给 贫论员 发送悄悄话 (19 bytes) () 08/15/2011 postreply 12:09:26

• 不是曲面积分。是积分求旋转面. -jinjing- ♀ 给 jinjing 发送悄悄话 (203 bytes) () 08/15/2011 postreply 16:26:28

• 死算出来的。一直没想出纯几何方法求h -wxcfan123- ♂ 给 wxcfan123 发送悄悄话 (219 bytes) () 08/15/2011 postreply 14:39:14

• You Rit. We also can use similar tringles and ...getting h(r-h)= -jinjing- ♀ 给 jinjing 发送悄悄话 (0 bytes) () 08/15/2011 postreply 16:44:33

• (R+r-h)^2=(R+r)^2-R^2-h^2,... -jinjing- ♀ 给 jinjing 发送悄悄话 (0 bytes) () 08/15/2011 postreply 17:31:02

• Sorry, It should be: (R+r-h)h=(R+r)^2-R^2-h^2,... -jinjing- ♀ 给 jinjing 发送悄悄话 (0 bytes) () 08/15/2011 postreply 17:33:49

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