# What would happen if the Earth starts revolving around the sun in the reverse direction? [closed]

Scenario:

Some major gravitational changes occur between the Sun and the Earth. As a result, now the Earth starts revolving around the sun in the reverse direction

Timespan for this gravitational shift: within a decade.

I am interested in the following points:

• What are the major effects on ecosystems?
• What will the climate changes be on the all continents?

EDIT:

I have observed that everyone is concerned about physics. I can understand that as its most important aspect, but it is possible to answer the above question about after the reversal? Assume that physics is handled by some type of magic, and there not much loss of living beings while the Earth starts to revolving around the sun in the reverse direction.

• Wait, revolving around the Sun in the opposite direction or on its axis in the opposite direction? Also, over what time period? Because instantly changing that would almost certainly kill everyone. Commented Apr 22, 2015 at 5:41
• @Samuel Please See Edit Commented Apr 22, 2015 at 5:57
• I'm still confused if you are going for the earths rotation changes on it's axis or if the earth is revolving around the sun the other way. Commented Apr 22, 2015 at 17:32
• Everyone and his mother is thrown out of the world while earth is being slowed down :P Commented Apr 22, 2015 at 21:25
• Now it's the Earth axis reversal? After several answers were given for the other completely different version? I'm voting to close since you even seem unclear what you're asking. Commented Apr 23, 2015 at 5:34

I know that in above scenario sun would rise in the West and set in the East.

The sun would still rise in the east and set in the west.

The easterly sunrise is due to the direction the Earth spins on its own axis, not its direction around the Sun. This is immediately obvious, if the opposite were true a day would actually be a year long.

If you've given appropriate time for the shift in momentum to occur, and bring the Moon along, then there likely won't be any noticeable effect. If you lose the Moon, see the relevant question.

If you want to see what this would look like, simply view the solar system from the south pole of the Earth.

• ok.. got ur point.. Commented Apr 22, 2015 at 6:52
• If the moon orbit was unchanged and you magically flipped the earth to spinning in the opposite direction the moon would stop receding from the Earth and begin getting ever closer. Wait a few billion years and you will definitely notice the difference as the tides get thousands of feet high, the Earth's crust melts and the moon crumbles when it hits the Roche Limit Commented Apr 23, 2015 at 5:20
• @GaryWalker The Earth reversing on its axis was not the original question. Commented Apr 23, 2015 at 5:43
• I figured that out, but I thought that the effect was interesting, no disrespect intended. But yeah, people should not totally change the question as that can be very confusing. You still got my upvote. Commented Apr 23, 2015 at 5:52

Not really an answer to the central ecosystem/climate question, but rather something about physics: the change will severely alter the orbit if not happening magically, instantaneous and momentum-free. In any case, it will require gigantic amounts of energy.

But what's really important to make this at least plausible is that this world is not going to slow down in its tracks, stop, and then start up again in the other direction. This would make it crash into the Sun long before the stop. Instead, the orbit's so called inclination must (slowly) shift by 180° into a retrograde orbit. So it will steadily climb or dive from its orbit with respect to the solar system's main plane.

So, over the course of the year, the sun is going to traverse other constellations until it arrives in the traditional ones again but will loop through them the other way around.

Another thing is that the planet will be barreling down the orbital highway the "wrong" way. Almost all of the stuff in a solar system goes around in the same direction, and many orbits are shared by several objects. So after your change, you'll have a much higher chance for hitting all this stuff coming up heads-on, until the planet has cleared up its path. Your average crash will be of much higher energy, too, because the relative speeds will be much higher.

Ok, this last point is even highly relevant to ecosystems and climate.

Assuming we handwave the physics problems with slowing down an orbit in the first place (as noted by Samuel and hiergiltdiestfu already; it may pull the Earth out the goldilocks zone towards Venus, probably eventually resulting in everyone's death due to extreme temperature increases), then at some point during the decade shift in direction, probably about 3-4 years in, you would lose seasons. This is because the seasons are due to the Earth's tilt and its position in relation to the sun.

Seasons would resume when the Earth starting going back the other way. This may cause some upheaval in the ecosystem; some places will have a winter/summer lasting half a dozen years.

Other than that, assuming the actual orbit has not been altered, there shouldn't be much change, as Samuel has already noted.

• I don't think you would totally lose seasons. They might alter drastically.
– Jax
Commented Apr 22, 2015 at 13:30

The ecosystem should be relatively fine, but the big concern is the point when the earth changes direction. The earth is revolving around the sun at a very high speed. You want to bring it to zero, and accelerate it again. Buildings would be crushed, people would be hurt and killed. So yes, the ecosystem would suffer.

Edit: I got it a bit wrong. I originally said the length of the year changes by a day--now I realize that while the number of calendar days changes by 1 the length of the year remains the same--the length of the day also changes. Neither effect will matter ecologically but the inhabitants very well might care.

Also, interplanetary spaceflight is severely curtailed. Until we build a supercatapault on the moon there will be no manned missions beyond the moon and the only way to rendezvous with another planet will involve really brutal aerobraking--twice that of the Galileo probe's plunge into Jupiter. (Which burned away a quarter of the total weight of the probe.)

• Why would the length of the year change? Commented Apr 22, 2015 at 21:16
• @HDE226868 Earth gets one rotation from going around the sun--but now that one rotation is in the opposite direction. Commented Apr 22, 2015 at 21:31
• That wouldn't change the length of the year, though. Commented Apr 22, 2015 at 21:33
• @HDE226868 Yeah, after some digging I realize I got it wrong--it's the length of the day that changes. Commented Apr 22, 2015 at 21:43