The length of days can vary depending on the year due to the tilt of the Earth's rotation axis relative to the plane of its orbit around the Sun. This leads to variations in the angle of incidence of solar rays and therefore to longer or shorter days depending on the season.
The Earth moves through space with a slightly tilted axis (about 23.5 degrees relative to its orbit). This detail is not trivial; it is even responsible for the seasons and influences the length of the days. You see, when the northern hemisphere tilts towards the Sun, it receives its rays more directly: the days get longer and it's summer. Conversely, when it tilts the other way, the days shorten and winter approaches. This effect is exactly reversed for our neighbors in the southern hemisphere. During the equinoxes, both hemispheres receive roughly the same amount of light, with days lasting about 12 hours everywhere; this is the period of balance. This regular back-and-forth rhythm shapes our daily lives throughout the year.
The Earth orbits the Sun in an elliptical shape, which means it is not always at the same distance from the Sun. It is closest at perihelion in early January, and farthest at aphelion in early July. This variation in distance leads to a slight change in the Earth's speed: it accelerates a bit when it is close to the Sun and slows down when it moves away from it. As a result, this affects the length of the true solar day, creating a difference of a few seconds at certain times of the year. Therefore, days do not last exactly 24 hours all year round—an intriguing and rather amusing astronomical nuance.
Our watch indicates an average, regular time, while the real sun is not so precise: it advances or lags slightly depending on the days. This discrepancy between the time on our watches and the true solar time is called the equation of time. Two reasons explain this: first, the elliptical orbit of the Earth causes us to speed up or slow down slightly over our annual orbit. Then, due to the tilt of our planet, the sun does not always move at the same apparent rate in the sky. These two phenomena combine and can create a difference of up to about fifteen minutes over the course of a year. As a result, the true solar days, during which we really measure the time between two passages of the sun due south, vary slightly in length.
Some astronomical events like powerful earthquakes or the El Niño phenomenon slightly influence the length of the day. A major earthquake can subtly alter the distribution of the Earth's mass, which slightly changes the Earth's rotation speed. Sometimes, even a massive volcanic eruption can have this kind of ultra-minimal effect on rotation by redistributing different amounts of material. However, the fluctuations remain negligible, on the order of a few milliseconds or less. Although this is negligible on a daily basis, over the long term, these small variations accumulate and force scientists to regularly adjust time measurement systems.
The massive movements of the oceans and the atmosphere can slightly influence the rotation speed of our planet. When significant ocean currents or strong winds move, they exchange some of their energy with the Earth. This transfer acts somewhat like a collective dance, creating tiny fluctuations in the exact length of the day. These effects are too weak to be noticed on a daily basis, but very precise tools like atomic clocks can clearly detect them. The phenomenon is similar to a figure skater subtly adjusting their speed by extending or bending their arms.
Did you know that the Earth's orbit around the Sun is elliptical rather than circular? Thus, the Earth reaches perihelion (the closest point to the Sun) in early January and aphelion (the farthest point) in early July, resulting in slight variations in orbital speed that indirectly influence the length of our solar days.
Did you know that powerful earthquakes can slightly alter the Earth's rotation axis and thus have a minimal impact on the exact length of a day? For example, the 9.1 magnitude earthquake that occurred off the coast of Sumatra in 2004 shortened the length of the day by about 6.8 microseconds.
Did you know that the length of the shortest day and the longest day can vary significantly depending on your location on Earth? For example, during the summer solstice, areas near the Arctic Circle experience nearly 24 hours of continuous daylight, a phenomenon known as "midnight sun."
Did you know that the equation of time is the technical term that refers to the difference between the time indicated by a sundial and the time shown by your watches or smartphones? It can vary by as much as +/- 15 minutes within a single year!
Indeed, certain specific astronomical phenomena such as powerful earthquakes, significant volcanic eruptions, or the gravitational effects associated with the approach of very massive celestial objects (even if very rarely) can slightly influence the Earth's rotation speed and thus temporarily affect the length of the day. However, these effects remain very minimal and are generally impossible to detect without extremely precise scientific instruments.
Sure! Here’s the translation: "Yes, but very slightly! Tides, primarily caused by the Moon and the Sun, create friction between the ocean, the seabed, and the Earth. This friction gradually slows down the Earth's rotation speed, resulting in a slight increase in the length of the day over time. However, this phenomenon is imperceptible on the scale of a human life."
The equation of time represents the difference between mean solar time used for our clocks and true solar time based on the actual position of the Sun. It largely explains why the Sun does not reach its highest point at exactly the same moment every day. This equation varies throughout the year due to the elliptical shape of Earth's orbit and the tilt of its axis.
This is mainly due to the tilt of the Earth's axis and the Earth's elliptical orbit around the sun. Depending on the time of year, certain regions of the Earth receive sunlight more or less directly, thereby accentuating the differences between the length of day and night.
Days are shorter in winter due to the tilt of the Earth's axis. During this period, the Earth is tilted in such a way that the affected hemisphere receives sunlight at a shallower angle, resulting in shorter days and longer nights.
No one has answered this quiz yet, be the first!' :-)
Question 1/5
