The fate of the Earth?
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From: Yousuf Khan on 3 Sep 2009 23:46 mike3 wrote: > So with Mars the thing that caused loss of atmosphere was simply not > having enough gravity, and the loss of magnetic field was not > important > in the loss of atmosphere? They were both important. I'd say that once the magnetic field left, Mars was doomed completely, and the rate of atmospheric loss increased. I'm not suggesting that the magnetic field was bottling up the atmosphere on Mars like a magnetic bottle. But the magnetic field is instrumental in diverting solar winds away from the planet's atmosphere. This results in less atmospheric loss. It's been suggested that Mars is probably too small to be life-bearing world, and that Earth and Venus are probably the minimum mass planets required for life-bearing. Of course we won't know that for sure until we study some large sample of extra-solar planets directly. Yousuf Khan
From: dow on 4 Sep 2009 16:31 On Sep 3, 11:24 pm, Yousuf Khan <bbb...(a)yahoo.com> wrote: > George wrote: > > Has tidal locking been ruled out in the case of Venus? Just curious. > > Well, Venus tidally locking with the Sun has been ruled out, but there > is a possibility that Venus is tidally locked to Earth. > > "For years it was thought that in the case of Venus that the Earth was > the culprit. It is a curious fact that as Venus rotates three times on > its axis in 729.27 days, the Earth goes twice around the Sun ( 728.50 > days) This has suggested to many dynamicists that Earth and Venus are > locked into a 3:2 tidal resonance."http://www.astronomycafe.net/qadir/q50..html > > Yousuf Khan The rotation speed of Venus is not *exactly* related to the orbital period relative to the earth. If there were a tidal lock, we should expect the periods to be exactly related. The torque that the earth's gravity exerts on Venus is minuscule compared with the torque that the sun exerts on it. The tidal torque that the sun exerts is slowing down Venus's retrograde rotation. Eventually, it will set Venus rotating in the prograde direction, and will synchronize Venus's rotation with its orbital motion. Probably, Venus used to rotate in the retrograde sense faster than it does now. The sun is slowing the rotation, and we just happen to be seeing it when it is roughly, but not exactly, synchronized with the movements of the earth. dow
From: Yousuf Khan on 5 Sep 2009 00:43 dow wrote: > The torque that the earth's gravity exerts on Venus is minuscule > compared with the torque that the sun exerts on it. The tidal torque > that the sun exerts is slowing down Venus's retrograde rotation. > Eventually, it will set Venus rotating in the prograde direction, and > will synchronize Venus's rotation with its orbital motion. > > Probably, Venus used to rotate in the retrograde sense faster than it > does now. The sun is slowing the rotation, and we just happen to be > seeing it when it is roughly, but not exactly, synchronized with the > movements of the earth. > > dow It's possible it's just a coincidence, but there are a lot of astronomical coincidences that we're experiencing right now. Not only the Venus thing, but also the fact that the Moon's disk is so close in size to the apparent disk size of the Sun. Etc. Yousuf Khan
From: Aki Karppinen on 5 Sep 2009 07:46 Pertti Koivisto kirjoitti > To thinking the future of the earth is much more difficult than the > past. But certainly I predict 100 % certainty that sun sets and rise > again. We can know future ! The sun shines also tomorrow ! Future can > be revealed ! > Astronomers collecting data from billions of stars try to think > timetable of future. Will the sun become to red giant ? Perhaps but > perhaps not. To know future of astronomical dimensions needs data of > such numbers that astromers have no certainty. But to think how well > planetary system work that we can live here is such a miracle that it > needs God to explain our existence. > http://users.utu.fi/pertkoiv/ - The Bible says that the sun darken, in one day.... + But also that in one day the sun will give seven times bigger brightness! * What is the next episode?
From: =?ISO-8859-1?Q?Anders_Ekl=F6f?= on 5 Sep 2009 08:28
Aki Karppinen <aki.karppinen(a)tut.fi> wrote: > Pertti Koivisto kirjoitti > > To thinking the future of the earth is much more difficult than the > > past. But certainly I predict 100 % certainty that sun sets and rise > > again. We can know future ! The sun shines also tomorrow ! Future can > > be revealed ! > > Astronomers collecting data from billions of stars try to think > > timetable of future. Will the sun become to red giant ? Perhaps but > > perhaps not. To know future of astronomical dimensions needs data of > > such numbers that astromers have no certainty. But to think how well > > planetary system work that we can live here is such a miracle that it > > needs God to explain our existence. > > http://users.utu.fi/pertkoiv/ > > - The Bible says that the sun darken, in one day.... > + But also that in one day the sun will give seven times bigger brightness! And this is relevant/interesing because... ? -- I recommend Macs to my friends, and Windows machines to those whom I don't mind billing by the hour |