02-16-2019, 10:27 PM | #11 | |
Join Date: Feb 2007
|
Re: Shielding Earth/Moving Earth from Suns Red Giant phase.
Quote:
Within the limits of the technology and physics we know, or can project, it all comes down to just how big Sol gets in the red giant phase. If the expansion stays small enough, then the smart move isn't to try to move the Earth at all (though the orbit may change on its own as the Sun changes). Instead, you build sunshades and mirrors to cut the insolation down to whatever level is convenient. If the Sun is going to get so big that we just must move the Earth, there's no obvious reason to go out to Jupiter or anywhere else in specific, if you've got the tech, you just widen the Earth's orbit to get far enough out to use sunshades and mirrors for the rest. Note also that the red giant phase of a main sequence star like Sol is relatively brief (we believe). On a cosmic scale, it won't be long before Sol sheds big shells of mass and starts shrinking down to a white dwarf. At that point, you might want to close the Earth's orbit inward again to maintain insolation, at least as long as the white dwarf is still hot enough to be useful (and it'll take the white dwarf a long time to cool. OTOH, if you've got the tech, you could leave Earth out in a big wide orbit and put an energy source in orbit at an appropriate distance to simulate the Sun.
__________________
HMS Overflow-For conversations off topic here. |
|
02-16-2019, 11:27 PM | #12 |
Join Date: Dec 2006
Location: Meifumado
|
Re: Shielding Earth/Moving Earth from Suns Red Giant phase.
I thought you could only park objects of negligible relative mass in Trojans. Is the Earth under the limit?
__________________
Collaborative Settings: Cyberpunk: Duopoly Nation Space Opera: Behind the King's Eclipse And heaps of forum collabs, 30+ and counting! |
02-17-2019, 03:01 AM | #13 |
Night Watchman
Join Date: Oct 2010
Location: Cambridge, UK
|
Re: Shielding Earth/Moving Earth from Suns Red Giant phase.
I think so. Jupiter is over 300 Earth masses. And if we can move Earth out there, we can presumably do occasional adjustments.
__________________
The Path of Cunning. Indexes: DFRPG Characters, Advantage of the Week, Disadvantage of the Week, Skill of the Week, Techniques. |
02-17-2019, 03:10 AM | #14 | |
Join Date: May 2005
Location: Oz
|
Re: Shielding Earth/Moving Earth from Suns Red Giant phase.
Quote:
Read about the Theia hypothesis for more information.
__________________
Decay is inherent in all composite things. Nod head. Get treat. |
|
02-17-2019, 06:55 AM | #15 |
Join Date: Feb 2016
|
Re: Shielding Earth/Moving Earth from Suns Red Giant phase.
I wonder if it would not just be easier to relocate everything of importance from the Earth to another system rather than moving the Earth. The Earth will not be consumed, that is an old theory from the 60s, and we have plenty of examples of stars more massive than Sol in the red giant phase that prove that stars of Sol mass only expand around 20 times or so. For example, Arcturus is a red giant of 1.08 Sol-masses and is 25 times the radius of Sol while Aldebaran is a red giant of 1.16 Sol-masses and is 45 times the radius of Sol. Gacrux is a red giant of 1.5 Sol-masses and is 84 times the radius of Sol.
Now, where GURPS Space falls flat is that it greatly underestimates L changes. Arcturus has a L of 170, which would have required it have stared as F2, which would have meant that it lost 30% of its mass. Aldebaran has a L of 518, which would have required it to start as an A2, which would have meant that it would have lost 45% of its mass. Gacrux has a L of 840, which would have required it to start as an A0, which would have meant that it would have lost 35% of its mass. I think that a possible solution would be to increase the L throughout the lifespan of the red giant phase of a star. L would start at 25x the maximum L of the main sequence and increase by 20% for every 10% of the red giant phase that the star passed through. For example, Sol would start at L 40 but would end at L 120 as it burned through the last of its available hydrogen. During that time, mass would start at 90% and mass losses would be 1% per 10% of the red giant phase. Of course, none of this includes red clump or asymptomatic red giant stars, which break all of the rules for standard red giant stars. Red clump stars are more massive, smaller, and brighter than red giant stars. Asymptomatic red giant stars are more massive, larger, and brighter than red giant stars. |
02-17-2019, 09:30 AM | #16 | |
Join Date: Aug 2015
|
Re: Shielding Earth/Moving Earth from Suns Red Giant phase.
Quote:
|
|
|
|