Why will planet Earth move slower on July 5?

Santa Cruz of Tenerife – He planet Earth It will move more slowly this Friday than the rest of the year, since it will be at the aphelion, or furthest point in its orbit around the Sun, he recalled this Thursday Alfred Rosenbergof the Institute of Astrophysics of the Canary Islands (IAC) of Spain.

Rosenberg noted that, due to aphelion, this event obviously happens every year. He added in a press release that to complete the orbit of about 940 million kilometers the planet travels at an average of about 30 kilometers per second.

The Earth’s orbit around the Sun is not circular, so sometimes it goes slower and sometimes slower, and once a year, on January 3 in the case of 2023, it is at perihelion or minimum distance, of about 147 million kilometers, while on Friday the distance between the planet and the sun will be about 152 million kilometers.

Rosenberg explained that Kepler’s second law says that the Earth will travel slower the farther it is from the Sun, and faster the closer it is.

He added that the velocities at both extreme points of the orbit can be determined, so on Friday the Earth will be moving at just over 29 km/s, 1 km/s less than what it moved at on January 3.

As a comparison of that distance, he has said that it would be equivalent to travelling the distance between the Spanish cities of Madrid and Barcelona (or the distance between the islands of La Graciosa and El Hierro, around 500 km in both cases) in 17 seconds.

It would take half a second longer to travel this distance at aphelion than at perihelion, and he commented that a curious effect of this difference in speeds is that summer in the northern hemisphere is about five days longer than winter.

From this data, Rosenberg said it can be deduced that the Earth’s orbit is quite close to a circumference, and added that in the case of a more extreme planet, such as Mercury, it suffers from a much more notable variation, from an aphelion at 70 million kilometers to a perihelion at 46 million kilometers.

From its surface, the apparent size of the Sun goes from being four times larger than that seen from Earth to being almost ten times larger, and moving around the Sun from almost 40 km/s at aphelion to almost 60 km/s at perihelion, noted the IAC presenter.

Rosenberg noted that there are two relevant factors in defining the seasons on a planet: the distance from its star and the tilt of the planet’s rotation axis.

In the case of Mercury, its inclination is zero, so it is the distance from the Sun that will mainly determine the temperature on its surface. But on Earth, which is tilted at 23.5 degrees, it is its inclination that is the main factor in defining the seasons, and not the distance from the Sun.

This is why the seasons are reversed in both hemispheres, and why the summer solstice on Earth coincides with the winter solstice in the southern hemisphere (and vice versa).

Rosenberg said one might think that the seasons in the southern hemisphere would be more extreme than those in the north, since the closest distance to the Sun coincides with the summer season, but “that is not the case.”

He also stressed that weather and climate are much more complex, and factors such as the surface area covered by land or ocean in each hemisphere must be taken into account, with the land area being approximately twice as large in the Northern Hemisphere as in the Southern Hemisphere, causing greater warming.

During aphelion, regions at a latitude between 20 and 25 degrees north will receive full sunlight (close to vertical), favoring maximum warming of these areas.