by Ann » Tue May 29, 2012 9:40 am
Well, Epictetus, it's a pity that I'm the one trying to answer your question, since I am the great galaxy/blue stars nerd on these boards. I'm far less of a solar system nerd, but I'll do my best.
I am almost certain that the Earth reaches perihelion in January and aphelion in July. That explains why the South Pole is colder than the North Pole here on the Earth. The seasonal effect caused by the Earth's tilt counteracts and alleviates the effect of aphelion and perihelion in the Northern Hemisphere, where most people live. In the Southern Hemisphere these two effects work in tandem, making winters colder and summers hotter.
As for Mars, it seems obvious to me that seasons have to be almost twice as long as the seasons on the Earth. That's because the Martian year is almost twice as long as the Earth's year, and there is no way that, say, the northern hemisphere of Mars could have summer twice during one Martian year. But as Chris points out, the orbit of Mars is considerably more elliptical than the orbit of the Earth. For a planet with a very elliptical orbit, the effects of being at perihelion or aphelion will have a much greater effect on the planet's temperature than the tilt of its axis, unless that tilt is extreme. For Mars, I believe that the tilt of the Martian axis has a greater effect than the ellipticity of its orbit, but the elongated shape of the orbit of Mars will affect the Martian seasons more than the much less pronounced ellipticity of the orbit of the Earth affects the seasons here.
As for minor planet Pluto, the operative word is C-O-L-D. Even so, Pluto must experience considerable seasons, due to the strong ellipticity of its orbit. Some years ago Pluto was at perihelion, and then it was closer to us than Neptune. What happened when Pluto was at perihelion was that its atmosphere became more substantial, due to the fact that certain volatiles that are usually frozen on Pluto sublimated and turned into an atmosphere.
A strange world of the solar system is Venus. The Venusian orbit is extremely circular, and the Venusian day is almost as long as its year. I don't know anything about its axial tilt (but you can google it), but I believe that the very thick atmosphere of Venus probably spreads the killer heat of our sister planet pretty evenly all over its surface. I doubt that Venus experiences any noticeable seasons at all.
Ann
Well, Epictetus, it's a pity that I'm the one trying to answer your question, since I am the great galaxy/blue stars nerd on these boards. I'm far less of a solar system nerd, but I'll do my best.
I am almost certain that the Earth reaches perihelion in January and aphelion in July. That explains why the South Pole is colder than the North Pole here on the Earth. The seasonal effect caused by the Earth's tilt counteracts and alleviates the effect of aphelion and perihelion in the Northern Hemisphere, where most people live. In the Southern Hemisphere these two effects work in tandem, making winters colder and summers hotter.
As for Mars, it seems obvious to me that seasons have to be almost twice as long as the seasons on the Earth. That's because the Martian year is almost twice as long as the Earth's year, and there is no way that, say, the northern hemisphere of Mars could have summer twice during one Martian year. But as Chris points out, the orbit of Mars is considerably more elliptical than the orbit of the Earth. For a planet with a very elliptical orbit, the effects of being at perihelion or aphelion will have a much greater effect on the planet's temperature than the tilt of its axis, unless that tilt is extreme. For Mars, I believe that the tilt of the Martian axis has a greater effect than the ellipticity of its orbit, but the elongated shape of the orbit of Mars will affect the Martian seasons more than the much less pronounced ellipticity of the orbit of the Earth affects the seasons here.
As for minor planet Pluto, the operative word is C-O-L-D. Even so, Pluto must experience considerable seasons, due to the strong ellipticity of its orbit. Some years ago Pluto was at perihelion, and then it was closer to us than Neptune. What happened when Pluto was at perihelion was that its atmosphere became more substantial, due to the fact that certain volatiles that are usually frozen on Pluto sublimated and turned into an atmosphere.
A strange world of the solar system is Venus. The Venusian orbit is extremely circular, and the Venusian day is almost as long as its year. I don't know anything about its axial tilt (but you can google it), but I believe that the very thick atmosphere of Venus probably spreads the killer heat of our sister planet pretty evenly all over its surface. I doubt that Venus experiences any noticeable seasons at all.
Ann