BIGSNAIL ISLANDS 大蝸牛群島
------------ [ 島民週報 2008/02/28 DEMO版第010期 ] -------------==================================================
日安  各位島民

二二八這一天，來看一則大新聞。
天文學家研究說：「地球氣數已盡，還有76億年。」
「蝦米？」也許你聽了會這樣驚呼！
「76億年？」
「是怎樣？我曾曾曾曾曾曾曾孫也碰不到吧！」
「這也算是大新聞？」
「Are you killing me？」
好、好、好，各位不要激動，聽我解釋一下。

英國薩塞克斯大學(University of Sussex)天文學名譽講師史密斯(Dr Robert Connon Smith)算出，一旦太陽燃燒殆盡，就會膨脹、變成危險的「紅巨星」。
史密斯目前與墨西哥瓜納華托大學(Universidad de Guanajuato)的施若德(Dr Klaus-Peter Schroeder)合作。他已重新計算過數據。不過可惜的是，結果顯示，地球死期已到。史密斯表示：「太陽表面稀薄大氣層將大幅延展，遠超過肉眼可見範圍，將擴及地球繞行軌道。」

簡單的說，太陽掛了，地球和其他的行星也不會好過。海洋會因太陽緩慢擴張(或說慢慢死去)而蒸發枯竭，水蒸氣(這一種強有力的溫室氣體 ，跟你家煮開水的那種不同！)將會充斥整片大氣層，使全球暖化一發不可收拾。

不過，這畢竟還要等個幾十億年，所以導致這場天災的天文知識，僅供參考。
但是，相關防範天災的一則新聞就有意思了。

聽過「全球種子地窖 Svalbard Global Seed Vault」嗎？

位於挪威的「全球種子地窖」 在本月26日正式啟用。距離北極點大約1000公里的北極斯瓦巴群島上，常年覆蓋著層層的冰雪，象徵人類希望的「全球種子地窖」就建造在此永凍層下。可以儲存450萬組種子的農作物種子儲藏室，由挪威耗資大約新台幣2億7000萬元所興建，未來一旦全球發生災難，導致糧食危機，這裡將成為提供人類糧食來源的種子庫。

全球種子地窖是由水泥和鋼鐵製成，可以抵擋地震、洪水甚至是核子彈的攻擊，另外，還有荷槍實彈的士兵駐守，戒備相當森嚴，目前地窖內已經有全球21個種子庫的複製樣本，保存在攝氏零下18度的恆溫中，未來種子的數量還會持續增加。 

厲害吧！
只是……真要用到種子的時候，會不會已經沒有合適的土壤可以讓植物生長呢？若真會如此，恐怕也還要多儲存一些土壤吧？

二二八，輕鬆一下。

季節的祝福

大蝸牛
2008-02-28
www.bigsnail.com

<<「地球氣數已盡，還有76億年。」新聞稿原文>>
Earth's destiny: A fiery end
New calculations by University of Sussex astronomers predict that the Earth will be swallowed up by the Sun in about 7.6 billion years unless the Earth's orbit can be altered.

Dr Robert Smith, Emeritus Reader in Astronomy, said his team previously calculated that the Earth would escape ultimate destruction, although be battered and burnt to a cinder. But this did not take into account the effect of the drag caused by the outer atmosphere of the dying Sun.

He says: "We showed previously that, as the Sun expanded, it would lose mass in the form of a strong wind, much more powerful than the current solar wind. This would reduce the gravitational pull of the Sun on the Earth, allowing the Earth's orbit to move outwards, ahead of the expanding Sun.

"If that were the only effect the Earth would indeed escape final destruction. However, the tenuous outer atmosphere of the Sun extends a long way beyond its visible surface, and it turns out the Earth would actually be orbiting within these very low density outer layers. The drag caused by this low-density gas is enough to cause the Earth to drift inwards, and finally to be captured and vaporised by the Sun."

The new paper was written in collaboration with Dr Klaus-Peter Schroeder, previously at Sussex, who is now in the Astronomy Department of the University of Guanajuato in Mexico.

Life on Earth will have disappeared long before 7.6 billion years, however. Scientists have shown that the Sun's slow expansion will cause the temperature at the surface of the Earth to rise. Oceans will evaporate, and the atmosphere will become laden with water vapour, which (like carbon dioxide) is a very effective greenhouse gas. Eventually, the oceans will boil dry and the water vapour will escape into space. In a billion years from now the Earth will be a very hot, dry and uninhabitable ball.

Can anything be done to prevent this fate? Dr Smith points to a remarkable scheme proposed by a team at Santa Cruz University, who suggest harnessing the gravitational effects of a close passage by a large asteroid to "nudge" the Earth's orbit gradually outwards away from the encroaching Sun. A suitable passage every 6000 years or so would be enough to keep the Earth out of trouble and allow life to survive for at least 5 billion years, and possibly even to survive the Sun's red giant phase.

"This sounds like science fiction," says Dr Smith. "But it seems that the energy requirements are just about possible and the technology could be developed over the next few centuries." However, it is a high-risk strategy - a slight miscalculation, and the asteroid could actually hit the Earth, with catastrophic consequences. "A safer solution may be to build a fleet of interplanetary 'life rafts' that could manoeuvre themselves always out of reach of the Sun, but close enough to use its energy," he adds.

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