Why do we have day and night?

Each day in earth begins at midnight. Different countries have their midnight starting at different intervals depending on their location on the Earth’s globe. The day occurs when the sun lights up the sky. This usually starts at around 6:00 in the morning. The night takes place when the sky is dark and only bright tiny spots and the moon are seen. The night usually starts at around 6:00 in the afternoon and ends to the same cycle the next day.

Midnight happens when a certain part of the Earth is directly opposite the sun and noon occurs when that part directly faces it. The changing of the sky from day to night is due to the Earth’s continuous spinning on its imaginary axis. While the Earth revolves around the sun, it is also rotating and spinning, like a ball being turned on top of a finger while the person carrying the ball moves around another person. Every time it completes a turn, a day is finished. It takes 24 hours for the earth to complete a rotation on its axis. This means that at any time, one half of the earth sees the sun while another is directly the opposite. This also means that different parts of the Earth such as countries and continents experience different parts of day and night in different times. That’s why there are different time zones. While a family in Athens eats their breakfast at 7:00 in the morning, a person that lives in Kiritimati eats his dinner at 7:00 in the evening at the same time.

Every time a certain part of the earth is facing the darkness or opposite the sun, it may or may not see the moon. The moon also orbits around the earth just like how the earth revolves around the sun; the moon doesn’t spin on its position though. It takes 27.3 days for the moon to completely go around the earth and this is the reason why the moon doesn’t look the same every night on the same part of the world. This is why every month, there are times when only quarter, half or the wholeness of the moon can be seen at different intervals. The moon’s revolution around the earth doesn’t mean that every month, it will be directly in between the sun and the earth, forming a direct line. This was calculated to only happen every 18 years, 11 days and 8 hours, causing a solar eclipse. A solar eclipse, which only happens when the moon is between the sun and the earth and when the three forms a perfect line, doesn’t happen every month. This is because the moon’s orbit is inclined at 5 degrees with respect to the Earth’s orbit around the sun. It does not orbit in parallel with the Earth’s orbit.

Even when the earth spins, the movement of the planet is not at all noticed by humans. It is because the planet is so massive and its strong gravitational force keeps everything on the ground just like a great, powerful and spherical magnet.

Filed under: Earth, Universe


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