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The Kepler’s laws they taught us to predict the movement of the planets around their stars. Thanks to this great German astronomer and mathematician, today we know that the Earth’s translation speed varies depending on how we are more or less close to the Sun. Because our planet revolves around the Sun, describing an elliptical orbit of 930 million kilometers, at a speed half of 107,280 kilometers per hour, which means traveling the distance in 365 days and almost 6 hours, hence every four years a leap is counted.
But this Tuesday, specifically at 07.52 Spanish time, our planet will pass through the perihelion -or point closest to our star, regarding 147 million kilometers-, accelerating its journey to the 110,700 kilometers per hour, accelerating 3,420 kilometers per hour above average speed.
On the contrary, on July 4 the Earth will pass through its afelio -the farthest distance from the Sun in its orbit-, which will take it regarding 5 million kilometers further, which will cause its speed to slow down to 103.536 kilometers per hour, more than 7,000 kilometers per hour apart.
Because Kepler realized that the line connecting the planets and the Sun covers the same area in the same amount of time. This means that when the planets are close to the Sun in their orbit, they move faster than when they are further away. Thus, the orbital speed of a planet will be lower, at a greater distance from the Sun, and at shorter distances the orbital speed will be greater.
Why is it cold if we are closer to the Sun?
Another question in the air: why is it so cold when we are so close to the Sun? Here, the answer is given by tilt of the Earth’s axis of rotation, which determines the seasons and temperatures. Therefore, we must not forget that although in the northern hemisphere we are in winter, in the south it is summer. As the axis of the Earth is directed to the same place with the passing of the year, the Earth is illuminated differently in each hemisphere according to the same time of year: in one place of the orbit the north pole is inclined towards the Sun ( and in the northern hemisphere the sunlight falls more perpendicularly, in addition to the fact that the nights last less) and 6 months later it is pointing the other way.
Being a little closer to the Sun, we receive a little more light and also heat. Specifically, the Earth receives 6.8% more insolation in perihelion (when we are closer) than in aphelion (when we are further away). So winters in the northern hemisphere are a little less cold than they would be if the Earth’s orbit were circular and we were always at the same distance from the Sun. Something equivalent happens in summer: they are not so hot (in the northern hemisphere ) as they should if the orbit were circular. In the southern hemisphere the opposite is true.
We might also appreciate that we are closer to the Sun by comparing the apparent size of the star: being closer, it looks a little bigger. However, it is an almost imperceptible phenomenon to the eye.
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