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Jianguo Wu
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面朝大海,春暖花开
面朝大海,春暖花开

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It's Create the Future week on #makercamp ! Using some basic materials and software running on your computer, we're going to make a 3-dimensional virtual reality controller - yes really! We call this Weekend Project powered by +RadioShack the Touchless 3D Tracking Interface. Look for it immediately following today's field trip, see the project here: http://makezine.com/projects/a-touchless-3d-tracking-interface/ - and have a great weekend everyone! #RSLetsPlay  
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Jupiter and the Sun are the two largest objects in our Solar System, and as they orbit around one another, they create regions where their gravity roughly cancels out. These are the Lagrangian points, created whenever two objects orbit one another: places where gravity is such that another small object can follow along in the orbit without being pulled in or out. And since things aren't getting pulled out of there, they get stuck in there as well: and so we have two large clumps of asteroids (and miscellaneous smaller space debris) in Jupiter's orbit. These are called the Trojan Asteroids; the group ahead of Jupiter is known as the Greek Camp, and the group behind it the Trojan Camp, with the asteroids in each camp being named after famous people in that war. Together, these two camps have as many asteroids as the Asteroid Belt.

Other stable patterns are possible, too: another one is what's called a 3:2 resonance pattern, asteroids whose motion gets confined to a basically triangular shape by the combined pull of Jupiter and the Sun. This group (for Jupiter) is called the Hilda Family, and their route forms a triangle with its three points at the two Lagrange points and at the point on Jupiter's orbit directly opposite it from the Sun. 

None of these orbits are perfectly stable, because each of these asteroids is subject to pulling from everything in the Solar System; as a result, an asteroid can shift from the Lagrange points to the Hilda family, and from the Hilda family to the Asteroid Belt (not shown), especially if it runs into something and changes its course. 

The reason that Pluto was demoted from planet to dwarf planet is that we realized that these things are not only numerous, but some of them are quite big. Some things we formerly called asteroids are actually bigger than Pluto, so the naming started to seem a little silly. So our Solar System has, in decreasing order of size, four gas giant planets (Jupiter, Saturn, Neptune and Uranus); four rocky planets (Earth, Venus, Mars, and Mercury); five officially recognized dwarf planets (Eris, Pluto, Haumea, Makemake, and Ceres); and a tremendous number of asteroids. (We suspect that there are actually about 100 dwarf planets, but the job of classifying what's an asteroid and what's actually a planet is still in progress -- see the "dwarf planet" link below if you want to know the details)

Ceres orbits in the Asteroid Belt, about halfway between Mars and Jupiter, just inside the triangle of the Hilda Family; Pluto and Haumea are both in the distant Kuiper Belt, outside the orbit of Neptune but shepherded by its orbit in much the same way that the Hildas are shepherded by Jupiter; Makemake is what's called a "cubewano," living in the Kuiper Belt but unshepherded, orbiting independently; and Eris is part of the Scattered Disc, the even more distant objects whose orbits don't sit nicely in the plane of the Solar System at all, having been kicked out of that plane by (we believe) scattering off large bodies like Jupiter.

But mostly, I wanted to share this to show you how things orbit. This picture comes from the amazing archive at http://sajri.astronomy.cz/asteroidgroups/groups.htm, which has many other such pictures, and comes to me via +Max Rubenacker

More information about all of these things:
http://en.wikipedia.org/wiki/Lagrangian_point
http://en.wikipedia.org/wiki/Trojan_(astronomy)
http://en.wikipedia.org/wiki/Hilda_family
http://en.wikipedia.org/wiki/Dwarf_planet
http://en.wikipedia.org/wiki/Kuiper_belt
http://en.wikipedia.org/wiki/Scattered_disc

#ScienceEveryDay
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The White Tower Building, Madrid, Spain
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爱马仕的作用?

有一天,一位其貌不扬的男士,带着一位十分美艳的小姐,来到一家爱马仕店。他为小姐选了一款价值565000元的包包。付款时,男士掏出支票本,十分潇洒地签了一张支票,店员有些为难。
男士看穿了店员的心思,十分冷静地对店员说:"我感觉到,您担心这是一张空头支票,对吗?今天是周六,银行关门。我建议您把支票和包都留下。等到下周一支票兑现之后,再请你们把包送到这位小姐的府上。您看这样行不行?"
店员放下心来,欣然地接受了这个建议,并且大方的承诺,送包的费用由该店承担,他本人将亲自把这件事情给办妥。
星期一,店员拿着支票去银行入账,支票果真是张空头支票! 愤怒的店员打电话给那位男士,男士对她说:"这没有什么要紧啊! 你和我都没有损失。上星期六的晚上我已搞定那女孩! 哦,多谢您的合作。"
这个故事揭示了次贷危机的本质。人们在对未来收益充满良好预期的时候,就可能忽略巨大的风险。美女认为周一60万的爱马仕包包就到家了,自然也就放松了警惕,认为投资是值得的,对于投入产出的预期是建立在一个具有巨大不确定性的风险上的。而对未来收益预期的包装则是投资机构最擅长的事情。中国人大多跟这个美女一样,对未来有着美好的憧憬,而盲目地把钞票送到股市楼市。没有这些人,股市楼市赚谁的钱呢。而媒体和分析家们,往往在其中扮演了爱马仕店员的配合角色。

这个故事告诉我们:“亲眼所见”的事物也未必是真实的,贪慕虚荣是要付出代价的…
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深港澳国际车展,人太多了!
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此货果真乃神器也!
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