Scientists figure that life on earth can only exist for about another billion years due to increased solar flux. Someone has proposed that it may be possible to move the earth to an orbit further from the sun by using an asteroid which first passes Earth and then Jupiter. It was calculated that enough orbital energy could be transferred between the two planets so that such menouvers (sp) need be carried out only about once every six thousand years or so to maintain a constant flux.
So I got to thinking. We know that the solar wind and sunlight exert a force. Why, then, is there not a constant force pushing the earth away from the sun like lighter elements were supposedly blown out to the outer solar system in the period following the creation of the sun? Why doesn’t that affect the earths orbit?
Mmmmkay, at our distance from the Sun the solar wind force equals something like 3 pounds per square mile, IIRC. There’s a muuuuch, much bigger force holding us close to the Sun. They call it gravity.
That’s not strictly true. Two bodies can exchange orbital energy through a close fly-by. It’s used all the time for launching interplanetary probes - first the probe swings by, say, Venus, stealing some orbital energy from Venus.
As for the solar wind and photon pressure, the effects are small on large bodies. Photon pressure is proportional to cross-sectional area of an object, while mass and gravitational force are proportional to the volume. If you double the radius, you increase photon pressure by a factor of 4 and mass by a factor of 8.
Enh, wouldn’t life on Earth be drastically different if the Earth was more (or less, for that matter) than 93,000,000 miles from the Sun? Moving the Earth out, however implausible, would make the planet a helluvalot colder.
actually, what they are trying to do is maintain the earth’s temperature when Sol goes into it’s red giant phase.
in our current orbit, the earth would be well inside the predicted diameter of the sun when it goes red giant, and bee pretty much melted. what this plan is set up to do is to move the earth out of that region and to put it in the new equatorial region, which would be closer to the sun than currently due to the ‘colder’ radiation- that is why we only have to scoot back once every 6,000 years to stay in this equatorial region.
a problem would be that our new orbit would be in such a position as to be gravitationally disrupted by mars, so we will probably have to bitchslap mars off past the asteroid belt to keep it from screwing with us.
hopefully, by the time Sol supernovas we will have moved out of this solar system. if not, then we are just fucked.
Interesting idea. But it’s silly to talk about what our descendents might want to do millions of years from now, when the advance of science and technology is making our concepts of the future completely obsolete every 50 years.
What scientists are saying this? Most data seems to show that the luminosity of a star stays constant over its main sequence life, and old Sol still has four or five billion years left on the main sequence. Once it does leave the main sequence, we’ll have bigger problems than just a gradually-increasing flux.
Oh, shit! I thought we still had four billion left! There goes my vacation!
Stars like the Sun don’t go supernova. The worst we can expect is that it will swell up so big that we’ll be right in the middle of it. Personally, I can’t wait to see if that makes George Bush believe in global warming.
This article from USA Today reports that “the sun gradually is getting brighter and hotter.” The article also indicates that life on Earth in its present orbit will only be possible for the next 500 million years.
This site states that “the sun has been increasing in luminosity over time. Early in the Earth’s history (several billion years ago), the Sun had only 70% of its current luminosity.”
This detailed site states that “While on the MS the Sun gradually has been increasing its luminosity–by about 40 percent since birth…”
(I have heard this numerous times recently, but these are the only fast cites I came across.)
The idea was to gradually move the Earth to a larger orbit in an effort to “save the Earth’s atmosphere from the heat of the sun, which is predicted to grow 11% over the next 1.1 billion years.” (quoted from the USA Today article)
This may be accomplished by using a 100-km diameter asteroid that slingshots around the Earth, Sun, and Jupiter, gradually increasing the orbital radius of the Earth from 93 million miles to 140 million miles. Each round trip of the asteroid (emphasis added) is expected to take 6000 years. The whole operation is expected to take millions of years.
and i am sorry about my various mistakes in my earlier post. i scraped the idea from a fungus-encrusted wall in an ancient corner of my vaults of knowledge, and only collected part of it before i had to run from the ancient demonic temple guards defending that region.
A.K.A. i thought the idea was a little silly and promptly forgot about it.
and i couldn’t remember if Sol would just shuffle off it’s mortal coils (and outer layers of gas) calmly or if it would go supernova, and i picked the wrong choice.
that reminds me-
{off topic and probably wrong HIJACK alert}
would the offslough of gas from Sol’s endstage destroy the earth? or would it just be an exceptionally strong solar wind(followed by a slow freezing death as we orbited a red dwarf)?
Yes, the Sun is getting hotter. The diameter (according to the models) should slightly decrease with time, and the Sun will heat up. I am not sure how much hotter it will get.
Over time, the helium in the Sun’s core builds up, like an ash. It will not fuse unless temperature and pressure are very large. But it gets compressed, and very hot. Eventually, the hydrogen in the core runs out, and the core begins to collapse under its own gravity. The temperature goes way up, and hydrogen will fuse in a shell surrounding the core. This dumps a vast amount of heat into the outer layers, which expand to compensate. The total energy goes up, but the surface area goes up even more. The energy per square centimeter emitted will drop, so the Sun becomes red, a red giant.
However, by that point the Sun will have been blowing a solar wind for several billion years. It will have lost mass, and mass defines gravity. As the gravity weakens, the Earth’s orbital radius increases. Some models show that by the time the Sun becomes a red giant, the Earth will actually be too far to be directly consumed. However, with an object at a surface temperature of 2500-3000 Kelvin filling half our sky, we’ll have other problems.