到那時，太陽的質量也會減降到現在的67%，在那之後的500萬年間，太陽將橫掃整個內太陽系（inner Solar System），此後的1.3億年間，它將開始燃氦進程（helium-burning phase），熱浪到地球時，太陽的質量損失速率將達到每年4.9 x 10^(20)噸！ 在他們的計算中，即便到那時，地球到太陽的平均距離將會從1.0AU擴張到1.5AU：
上圖只是展示距離和質心變化，比例嚴重失調請忽略
但是地球「逃離」的速度趕不上紅巨星「腫脹」的速度，這是最關鍵因素所在。大家如果想了解詳細內容，請到http://arxiv.org/abs/0801.4031去下載他們的文章，這篇文章發表在《Monthly Notices of the Royal Astronomical Society》上。
我來安利一個老頭叫做David Brin的視頻，名字叫做「How to lift the earth」，這是源地址：https://www.youtube.com/watch?v=Ai8x-ZqjXPc，大意是利用電動力學和電磁學結合的方法實行引力遷移。 為防止大家可能無法觀看，我把重要部分截取出來，圖和文字都是自己配的：
憂患意識很重的樣子
上面earth忘了大寫，大家原諒，湊活看：
下面是他做的一些計算：
We immediately run into a scale problem: The Earth』s magnetic field is very strong -- 25,000 nanotesla in LEO, near the equator. But we』ve already seen we cannot use that to move the Earth, only satellites near it. In contrast, the sun』smagnetic field at Earth"s radius from sun (1 a.u.) is only ~1 nanotesla. This is partly compensated for by the fact that Earth"s velocity around the sun is four times higher than a satellite orbiting Earth in LEO. Put it all together and you induce along the beanstalk』s length an EMF of ~200V/km. If our baseline tether, suspended outward from the far side of the moon, is say 50,000 kilometers long… a hefty engineering feat, but no obstacle to future folk… and if we also assume use of superconductors, then it should be possible to inducemany kV -- and the associated force. Another important factor: the EM tether trick requires having a cloud of electrons nearby that can complete the circuit. In effect, to make this work, our descendants may need to generate sufficient electron densities near the Moon to provide it with an ionosphere. A challenge, as would be ohmic losses and the inefficiency of pumping during the whole orbit, rather than just at those peak, inner and outer sites. All right, let』s assume a probably optimistic average efficiency of ~25%. This gives an intentionally round number of order 1E33 joules, to be supplied in 1E8 (a hundred million) years. That requires 3.2E17 watts average power during that time. Now let』s triple that, because there will likely be many times when the tether-elevator isn』t properly used, is ignored, or does not exist – till the next long-seeing generation or species comes along. Call the requirement ten to the eighteen watts. Or a billion gigawatts. The current energy use of Earth civilization is about 20 terawatts or 20,000 gigawatts. So… it would seem that our Earth lifting system would need to apply only 50,000 times the total generating capacity of all artificial energy systems currently used by humankind. Only 50,000 times our current energy use? A pittance! David還用陽傘陰影（parasol shades）技術做了一番比較： Let』s take a look at a project that is of similar scale, easier (by far) for a primitive civilization like ours to implement, but with other disadvantages. For our purposes, it will set things in perspective.
That major example would be a Shade Parasol,established a bit sunward of the L1 Lagrangian point, ~1.5E9 m sunward of Earth, with the purpose of countering global warming by slightly reducing the amount of sunlight hitting the planet. Calculations by Oldson and Carroll suggest that such a parasol might cool the planet by the same amount as increasing the planet』s orbit by 10%, just by removing 17% or so of the sunlight. This requires a parasol a bit more than half the Earth』s diameter or about 7000 kilometers. This advantages of somewhat smaller surface area, and not requiring a lunar beanstalk to work with, are countered by the fact that any shading system must be maintained, almost constantly. And the moment you lose the parasol, heating resumes, as before, but with many transients caused by any sudden change. These effects might be especially devastating if the parasol failed because of a civilization setback that prevented quick repairs.
參考資料： David Brin"s EXISTENCE Death of the Sun Planet Survives its Star Becoming a Red Giant http://arxiv.org/abs/0801.4031 http://www.universetoday.com/12648/will-earth-survive-when-the-sun-becomes-a-red-giant/ http://www.udel.edu/PR/UDaily/2008/sep/pla http://davidbrin.blogspot.ca/2014/11/lets-lift-earth.html https://www.youtube.com/watch?v=Ai8x-ZqjXPc Electrodynamic tether http://www.davidbrin.com/shortstories.html http://phobos.colorado.edu/COSGC_Projects/Past_Projects/dino/MAGIC%20Boom/Other%20Documentation/Tether%20Research%20Documents/Guidebook%20For%20Analysis%20of%20Tether%20Applications%20-%20Joe%20Carroll.pdf Gravity-gradient stabilization C:DOCUME~1BRYANY~1DesktopSPACER~1 echnologies.html Space Elevator Futuristic Moon Elevator Idea Takes Aim at Lunar Lifts The Kardashev Scale
