Day and Night, Seasons, White Night, Polar Night
* If you are asked to access your location, please allow it. * Your personal data is not stored on the server. * For iOS devices, please allow location access as follows. Day and night The … more
Planet Earth Simulation
Earth’s Revolution and Seasons (WebGL)
Earth Rotation and Seasonal Changes The Earth’s rotation axis is tilted at an angle of about 23.5 ° to the orbital axis. Because of this inclination, seasonal changes occur like spring, summer, autumn, and winter. The … more
Real Size & Orbit of Earth and Moon
The photographs of the Earth and the moon close together that you can see on posters, etc., are designed to be easy to see. The moon’s apparent diameter is only about 0.5˚. This tells us that … more
Eratosthenes’ Calculation of Earth’s Circumference 2
Eratosthenes’ Calculation of Earth’s Circumference The first person to measure the earth’s size was Eratosthenes, an ancient Greek scientist about 2,000 years ago. Eratosthenes lived in Alexandria, near the Nile River’s mouth by the Mediterranean coast, … more
Foucault Pendulum (WebGL)
Foucault’s pendulum is a device invented by French scientist Leon Foucault to prove the Earth’s rotation in 1851. The fact that the Earth rotates has been known for a long time, but it is the first … more
Daylight Map
* If you are asked to access your location, please allow it. * Your personal data is not stored on the server. * For iOS devices, please allow location access as follows. day and night The … more
Latitude of Polaris
Latitude of Polaris Polaris is far from Earth. Thus, light from the North Star reaches parallel to the Earth. And since the earth is round, the North Star’s latitude varies depending on where it is observed. … more
Is Sun Rays Parallel?
Parallel sunlight The radiant energy of the sun spreads in every direction. However, since the sun and the earth are far apart, we assume that they are usually almost parallel. Ancient Greece’s Eratosthenes measured Earth’s size … more
Eratosthenes’ Calculation of Earth’s Circumference
Eratosthenes’ Calculation of Earth’s Circumference The first person to measure the earth’s size was Eratosthenes, an ancient Greek scientist about 2,000 years ago. Eratosthenes lived in Alexandria, near the Nile River’s mouth by the Mediterranean coast, … more
Path of Satellite
From the perspective of an observer on Earth, the orbits of satellites with an orbiting period of less than 24 hours appear to move westward little by little with each turn. This phenomenon occurs because of … more