Why can't the varying distance between the sun and the earth account for season?

Answer 1

Let's look at the following facts:

1) The distance between the Earth and the Sun is 149.6 million kilometers, the change of that distance is less than 1%.

2) When it's summer in the northern hemisphere it's winter in the southern - and vise versa. So the reason for the seasons cannot be the distance from the sun, but a property of Earth - it's axial tilt.

Answer 2

The distance between the sun and the Earth doesn't vary all that much; the elliptical orbit is nearly circular. Furthermore and more importantly, the northern and southern hemispheres of the Earth experience opposite seasons at any given time; when it is winter in the north, it is summer in the south. Yet both hemispheres are the same distance from the sun. So clearly, it must be the axial tilt that causes seasons, and not the varying distance from the sun.

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The eccentricity of the orbit is small, 0.0167, which means that the distance from the Sun varies over range of of 3.3%, so the power in the Sun's rays varies by about 7%, which is not very much for a yearly cycle although it would be serious if maintained for 100 years or so.

Answer 3

There is a change in the amount of energy from the sun reaching the earth due to the elliptical nature of earths orbit around the sun, but the limits of this change are small compared to the effect of the tilt of the earths axis, and its tendency to remain parrallel throughout its orbit of the sun.

For evidence, the fact that the northern and southern hemispheres have summer and winter at opposite times of the year from each other despite being exactly the same distance from the sun should be pretty convincing.

Answer 4

The two most obvious indications are:

1) The Southern Hemisphere has winter when the Northern Hemisphere has summer (and vice versa)

2) At the time of Earth's closest approach to the Sun (January), the temperatures in many parts of the Northern hemisphere are among the coldest that occur there.

Answer 5

Because when the Earth is closest to the sun (january) it isn't much closer to have an effect on the seasons.

Answer 6

Because Earth's orbit is not a perfect circle. It is more of an oval shape called an ellipse.

Answer 7

No, seasons are caused by the Earth's rotation, not by orbiting the sun.