What happens if Earth has 12 months of 45 days due to longer orbit?

Question

OK, so something happened to Earth, huge cosmic calamity type thing, and now Earth's orbit is longer.

My story is set 100 years after this event, and everyone has had a pretty hard memory wipe as to what life was like before.

The Moon is still doing its thang, same as now. Unless several of you NASA types shout at me and tell me why this could not possibly be so.

I have basically divided the year into 12 months of 45 days. So the inhabitants of my story still have some old calendars from the Time Before - but as the years began to go by in this new Age, they noticed the discrepancies and eventually, 100 years later, have worked it out. For simplicity's sake they kept the months that were written on all the calendars and just added the extra days.

What are the implications? Would Summer and Winter be too extreme?

Would it be possible to have human, or any, life? [ Other than tardigrades and cockroaches ;-) ]

This is my 1st ever question, so please go easy on me, but also please feel free - obviously - to geek out and give me as much intense and gory detail as you want as to why this would / wouldn't work. Magic definitely exists in this universe, so your answer does not have to be strict science - feel free to wave the wizard's wand if needed.

So. It's Saturday night, team - what better offer could you possibly have other than 'go crazy on that keyboard'.

Many thanks in advance, folks.

Answer 1

Nothing much has changed, except the Earth is spinning faster.

All of the time terms we use - day, month, year relate to cyclical phenomena that humans experience.

The "day" reflects the rotational period of the Earth. The "month" reflects the Moon's phases, and ultimately its orbital period around the Earth. The "year" reflects the passage of the seasons, which ultimately reflects the Earth's orbital period around the Sun.

The counts to convert one period to another reflect the ratios between the different periods.

Your question has an assumption that the "year" gets longer. But that requires some complicated orbital balancing, moving the Earth farther out from the Sun and the Moon farther out from the Earth in a way that the new ratio between the periods coincides with the old one

The key criterion you put in your question was 12 months, presumably 12 months in a year. This means that the ratio between the Moon's orbital period and the Earth's orbital period is about the same as before.

It's simpler to assume that the Earth and Moon haven't changed their orbits at all. Thus, the month and year don't change at all. Instead, we change the length of the day.

If we "spin up" the Earth so that it rotates in a little under 16 hours, we can get 45 revolutions within one lunar orbital period, which is the same "month" as before.

This new configuration a little unstable. The Moon is gradually moving away from the Earth, and the Earth's rotation is gradually slowing down, because of tidal forces. This effect would accelerate with a faster day, because there is more energy for the Moon to steal.

The Earth's magnetic field would get stronger. Its equatorial bulge would be greater, and the difference in gravity between the poles and Equator would be bigger. The axis would precess and wobble less. Storms would be stronger because of an increased Coriolis effect. There would probably be some geological effects, more earthquakes and volcanism.

But the Earth would keep its atmosphere and people could live on the surface. There would be disruption to organisms' circadian rhythms and new evolutionary pressures.

But that will be the reality people are living in. N.K. Jemisin's The Fifth Season and followup books provide closest analogy I can think of to life on a spun-up Earth.

Answer 2

Colder earth

Assuming the new orbit is still roughly circular. The new orbit will be 1.31 times as distant from the sun.

Illumination will be 58.3% as bright.

Old Earth normal temperature is 288K (15C, 59F)
Here's a handy tool to calculate planet temperature.
The average temperature, with the planet's albedo remaining constant, will now be 251K This is some 37C colder than before.

BUT With this cold, the sea surface will form ice. Ice has a much higher Albedo, reflecting more light away.

Taking the change in Albedo in consideration (change from 0.29 to 0.50) the new stable temperature averages 230K (-43C, -45F)

Your people will starve to death due to the complete shutdown of the plant ecosystem, but only if they locate a good stock of parkas first. Otherwise they will freeze to death.

To fix this, just use the same Handwavium that shifted the Earth's Orbit to increase the sun's activity, to whatever level you desire. Setting it to 100/58.3 = 171.5% level will suffice nicely.

(This had other issues, with the sun now being warmer, thus shining more towards the blue side of the spectrum, and UV output going nuts.. but that is trivial compared to the forces needed to shift the orbit like that without mulching the planet in the process) . But ignoring this.

You now have an Earth orbiting a hotter sun, and receiving about the same sunlight levels. The sun will be visibly smaller, if the moon is somehow in the same orbit it used to be, then it will appear quite a bit bigger than the sun. No more annular eclipses for you, sorry.

Seasons: With each season being 50% longer, the summer will be a bit longer, but a lot hotter, drier and more extreme. Your winters will not be much more extreme, but will be lots longer. Quite a bit more than the expected 50% increase you think. Spring flooding from melting snow will be about double what you were used to, due to heavier snows.

Answer 3

The world freezes, and everyone dies. A 540 day year puts the Earth about halfway between its current orbit and the orbit of Mars, call it 1.25 AU, so insolation is reduced by around 35%. That’s a lot.

Answer 4

The world is ~50° colder

The surviving people 100 years later are living in cramped underground shelters converted from old mines, as the rocks are still hot a few hundred meters underground.

The big freeze, as it's now known, wiped out 99.99% of the earth. Only a fraction of humanity survived, most dying of starvation or thirst a few weeks after the freeze. People in extremely hot regions managed to get hit with "only" -10 degree temperatures which they could survive with a wardrobe change, and they were able to gather persevered food, ans migrate to large underground mines and set up hydroponics using geothermal power, and have survived, there are a few dozen such colonies scattered around the planet, but they have never made contact with each other.

Were the shift to have occurred after we'd dismally failed at global warming mitigation - that might be another matter. An increase in atmospheric methane from too many cattle melts tundra containing methane which causes a runaway greenhouse effect, if this were to occur at roughly the same time as the orbit shift it could counteract the damage we did with global warming and leave us with a nice planet again.