I guess the fate of the universe is relevant, if we find a way to travel 99.99999...% of the speed of light.  It would be good to know what the destination would look like.  But this is mainly a question of knowing the universe.

I'm not sure if I would prefer an immortal universe or an eventual end. Both are difficult to contemplate. 

Banana wrote:

Source of the post I'm not sure if I would prefer an immortal universe or an eventual end. Both are difficult to contemplate.

Perhaps we live in both, universe dies, new universe replaces it, and this repeats forever.

^^^ Hopefully there'd be something new each time. The exact same people and the exact same events each cycle would be some combination of depressing and boring.

Anyways, I thought of a new question while exploring a lopsided binary system in SE. If we replaced the Earth with a non-flaring red dwarf star of 0.12 solar masses, and replaced the Moon with the Earth and adjusted the SMA to make the period match the old lunar orbital period of 27.32166.... days with tidal locking, how would weather patterns and climate systems change? Assuming all other orbital properties remain the same (low eccentricities, inclinations, etc).

Well...it would certainly be warm, for one! 

i'm not too well-versed in these matters, but from what I can tell:
Life as we know it probably wouldn't fare too well, so we can subtract its effects on the environment. There wouldn't be much oxygen as no photosynthesis would occur and remaining stores would be used in oxidation processes such as rusting. There likely wouldn't be much water left on the side of the planet exposed to the star at that distance, so no water-related precipitation or hurricanes. The greenhouse effect would become quite noticeable. Earth may become Venus.

Banana wrote:

Source of the post Well...it would certainly be warm, for one! 

Are you certain?  I get the opposite answer.

By my calculations (described here), the star would have 0.175% the luminosity of the Sun, and the Earth would have to orbit at 0.0876AU to have a 27.3 day orbital period.  Therefore the intensity of sunlight at the new Earth would be 22.8% as strong.

If we assume the greenhouse effect works the same way (which is wrong -- the sunlight would have a cooler spectrum) then the surface temperature would be 200K (-73C).  With no greenhouse effect, it would be 176K (-97C).  The Earth would quickly freeze over and life on the surface would go extinct. =(

Watsisname wrote:

Source of the post life would go extinct

Probably not, some extremophiles will probably survive

True that -- probably not so much on the surface though, but deep underground and at thermal vents.

Another thing is that the temperature of 176 to 200K is an upper estimate, because as the Earth freezes the albedo would increase, making it even colder.  Basically we're looking at an extreme snow-ball Earth scenario.  I don't think even volcanoes would be able to pull the climate out of it, because it would get so cold that even the CO2 would freeze out instead of accumulating in the atmosphere.

Oh, wait a minute.  Are we keeping the original Sun in the picture, or no?

Well, PlutonianEmpire's post said nothing about removing the sun...

Watsisname wrote:

Oh, wait a minute.  Are we keeping the original Sun in the picture, or no?

Yes, we are.

The new red dwarf parent takes Earth's old orbit, at 1 AU from Sol.

Without sun

With sun

Pictures are made with SE 0.971.

In SE 0.981 the result is somewhat different. (With sun.)
 

Space Engine 0.971 has a bug where temperatures of objects in binary systems are incorrectly calculated, resulting in very hot temperatures. I was more interested in how the new configuration would affect both day to day weather patterns in addition to the long term climatic effects.

PlutonianEmpire wrote:

Source of the post Yes, we are.

Yeah, my bad, I misunderstood. Actually I was surprised that the Earth would be within the Hill Sphere of the red dwarf in that case, but it is and the scenario works.  It is quite interesting!

So basically we'd be adding an additional 22.8% solar flux to the Earth, which would raise the average temperature by about 10 to 15 degrees C, (before accounting for climate feedbacks, which would probably push it higher), and this roughly agrees with what Jack shows in SE.

A ~10c warmer world is difficult to contemplate, and we have to look back at least as far as the Paleocene-Eocene Thermal Maximum (~50 million years ago) to find a comparable climate state in Earth history.  During the PETM there was a mass migration of species as temperatures rose, and subtropical species even made it to the poles.  Species that could not adapt or migrate died out, particularly bottom ocean dwellers.  Weather patterns similarly shifted poleward, and precipitation was much more intense with the extra water vapor in the atmosphere.

In this case though, Earth's rotation also changes from a day to a month, and the heat would be distributed differently.  About 1/5 of the heat lands on a fixed side of Earth, while the other 4/5 rotates around the Earth with the "solar day", which lasts a month (29.5 days, assuming Earth orbits prograde).  This is a pretty wonky climate situation.  When the red dwarf is near its "new phase", the side of Earth facing it would be hottest, while the other side is in cold night.  When near "full phase" the heating is more even, but the side facing the red dwarf is colder.  So there would be a monthly cycle in the atmospheric circulation and weather patterns, with a "hot pole" that rotates around the planet with the sun and is strongest when it is aligned with the red dwarf.

I'm not sure if it would get cold enough for oceans to start freezing on the night (sun-relative) side.  I'm inclined to doubt it because this oscillation is pretty short (not a whole lot of time to heat up and cool down each cycle) and the oceans and atmosphere are pretty effective at transferring the heat.  Basically I imagine a flow of wind and storms away from the sub-solar point, just like a typical tidally locked planet, except that this flow also moves and changes intensity.

Most species would be in trouble if Earth suddenly found itself in this scenario, but if the system evolved this way then life could adapt to it and probably even thrive.  Even photosynthesis should be fine with the seasonal loss of sunlight -- it already manages this in the polar winters which last a lot longer.

I would really love to see a global climate model simulating this.

Watsisname wrote:

Source of the post Even photosynthesis should be fine with the seasonal loss of sunlight -- it already manages this in the polar winters which last a lot longer.

I wonder if there then would be deciduous trees.  There hardly would be enough time to shed and regrow leaves.  If there only are evergreen trees, they would have to be more robust to withstand snow which is much easier without leaves.  The long polar winters may be an advantage - it allows plants to adapt, but a monthly cycle makes that more difficult.