This is a question that has been bugging me for a while now, I was wondering about the effects on the Earth if it was in different orbital situations to what it is now, and one of those was what would happen, if somehow, the Earth was in a polar orbit around the Sun? Would the equator be perpendicular to where it is now? As well as time zones?

This is taking that everything else about the Earth was the same as it is now, E.G it's axis, distance from the Sun and the presence of the Moon were all the same.

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    $\begingroup$ Can you clarify what you mean by "polar"? That is: are you changing the Earth's axis of rotation but keeping the same orbit, or are you rotating the orbit by $pi/2$ and then mucking with the axis of rotation? $\endgroup$ – Carl Witthoft Dec 14 '15 at 14:31
  • $\begingroup$ By polar I mean by how artificial satellites are in polar orbit around Earth. I guess you could say, a longitudinal orbit? $\endgroup$ – MisoMaths Dec 14 '15 at 14:34
  • $\begingroup$ It would be interesting to have an answer clarifying whether frame drag or any other gravitational effects would be large enough to be significant. I doubt they would be, but I'm not good enough at the math to be sure. $\endgroup$ – Todd Wilcox Dec 14 '15 at 19:09

the Earth was in a polar orbit around the Sun?

If you took the Earth's current orbit and rotated it so that the Earth's orbit took it over the Sun's poles (with respect to the Sun's axis of rotation). The Earth's current orbit is approximately in the plane through the Sun's equator.

This is called orbital inclination. Earth's is about 7 degrees (to Sun's equator), dwarf planet Eris has an inclination of about 44 degrees (to the ecliptic)

Would the equator be perpendicular to where it is now?

That would depend on what events caused the planet to get into that orbit. Some planets don't have their axis of rotation aligned very closely to the axis of orbit.

Object  Axial Tilt in degrees
Sun     7.25    
Mercury 0.03    
Venus   178.36  
Earth   23.44   
Moon    6.68    
Mars    25.19   
Jupiter 3.13    
Saturn  26.73   
Uranus  97.77   
Neptune 28.32   
Pluto   122.53  

The tilt is shown by the arrows through the various bodies in this diagram:

enter image description here

It is worth noting that the tilt (or "obliquity") isn't constant. Some planets vary a lot, Mars varies from 15 to 35 degrees and over tens of millions of years may have varied between 0 and 60 degrees. The obliquity of Mars is often referred to as being in a chaotic state.

As well as time zones?

Time zones are a reflection of the Earth's rotation and not it's orbit. They are also a political invention.

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  • $\begingroup$ Thank you! Your description of the orbit is exactly what I was trying to get across, thanks for the info! $\endgroup$ – MisoMaths Dec 14 '15 at 14:47
  • $\begingroup$ It would be helpful to add units to the figures here for inclination and axial tilt. At least so we know you mean degrees and not radians. $\endgroup$ – Asher Dec 14 '15 at 16:54
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    $\begingroup$ Would rotating the Earths orbital plane affect perturbations from the rest of the planets to a significant amount? $\endgroup$ – Dan Is Fiddling By Firelight Dec 14 '15 at 18:58
  • $\begingroup$ Wouldn't it be unlikely that any planet would have a polar orbit, if we were to consider the currently known theories of planet formation? Also, wouldn't Jupiter's tug topple down such an orbit fairly quickly (this is a gut feeling I have). $\endgroup$ – sampathsris Dec 15 '15 at 10:32
  • $\begingroup$ @Krumia: I agree but note Pluto's inclination. I think there are some smaller bodies in more elliptical orbits with higher inclinations. The question focused on consequences rather than causes and probabilities - but you make an interesting point. $\endgroup$ – RedGrittyBrick Dec 15 '15 at 10:49

If you leave the spin angular momentum unchanged with respect to the Sun's spin angular momentum then this has drastic effects. Whilst a "day" is still 24 hours, the periods of daytime and night time become much longer. I think the effect is equivalent to changing the inclination of Earth's spin to its orbit to 67 degrees. Thus anything above 23N or below 23S would be considered "polar" and would experience 24 hour illumination during some parts of the year. Equatorial latitudes would still experience a 24 hour diurnal cycle but the height that the Sun got above the horizon would vary with a much bigger amplitude.

One of the main changes would be in the Earth's geocoronal environment. The magnetic activity of the Sun is concentrated toward low solar latitudes - this means that during solar activity cycles, then every 11 years or so the Earth is subjected to a considerable bombardment in the form of accelerated charged particles and coronal mass ejections (CMEs). However the solar wind character would also change throughout the year. The polar regions of the Sun emit a thin, fast wind, whereas the equatorial regions are dominated by a slower, denser wind.

If the Earth was on a polar orbit, then major magnetic-related events, such as CMEs would be much less frequent - these are confined to latitudes $\pm 30$ degrees for most of the solar cycle, but can extend to $\pm 60$ degrees near solar maximum (Webb & Howard 2012). The "space weather" environment could be considerably quieter for several months of the year. This would be of considerable significance in my field (astrophysics) in terms of the kinds of satellites, detectors and observations one could make with lower interference from solar activity. It would also have significance for dosage of radiation that is received by astronauts working for lengthy periods of time in low-Earth orbit. We'd also miss out on a number of northern lights displays!

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I'm surprised no one's mentioned the effect on Earth's 24-hour days...

If this is what you mean by a polar orbit:

enter image description here

Except the Earth in the picture is the sun, and the satellite the Earth, and the Earth still rotates "horizontally," then the most noticeable effect to humans would be that the rotation of the Earth no longer creates 24-hour days! Half the Earth would be exposed to the sun for 6 months (creating a 6-month "day") while the other half would be shrouded in darkness for equally as long (ignoring tilt). I imagine life as we know it could not survive the temperature variation, then.

That answers your question about timezones, sort of :-)

Meanwhile the equator is by definition the plane perpendicular to the axis of rotation going through the center, so no, the equator doesn't move, relative to the Earth.

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    $\begingroup$ This is incorrect. The "day" is defined by the spin period. What would happen is that there would be much more extreme yearly changes in the length of day vs night as a function of latitude. The Earth does not rotate in the plane of its orbit ("horizontally"', as you put it) now. $\endgroup$ – Rob Jeffries Dec 15 '15 at 7:39
  • $\begingroup$ Hm. Suppose we live in the Northern hemisphere, and the Earth is revolving the sun on a polar orbit and we're now starting our descent "under" the sun (like the satellite in the image going "under" the Earth). If the Earth continues to orbit the sun at the current rate (1 year) then wouldn't we be exposed to the sun for several months? Is your argument more about the technical definition of a day? $\endgroup$ – Andrew Cheong Dec 15 '15 at 16:08
  • $\begingroup$ I suppose closer to the equator at a latitude lesser than Earth's "tilt" Northeners would indeed experience some night (more like dusk) but my main thought seems to hold as far as I can tell. $\endgroup$ – Andrew Cheong Dec 15 '15 at 16:14
  • $\begingroup$ @RobJeffries - Would you consider commenting? I see others also saying there won't be significant changes and I wonder what it is that I'm seeing wrong... $\endgroup$ – Andrew Cheong Dec 18 '15 at 0:21

As I interpret your questions, there would not be "significant" changes. The equator would be just like it is, and so would the time zones. This is easier to understand if you do the equivalent operation, rotate the axis of the sun 90 degrees, instead of the earth's orbit!

Obviously, the night sky view would change, and the solar effects would also change.

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    $\begingroup$ I don't think this is equivalent. The question specifies leaving the spin axis unchanged. $\endgroup$ – Rob Jeffries Mar 12 at 7:24

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