The Earth goes through a constant cycle of day and night because it rotates on an axis. At any point in time, only about half of the Earth is facing the sun, while the other side is facing away from it. The side that is ... More »

The seasons occur because of Earth's tilt on its axis. The axial tilt of 23.5 degrees from the vertical axis influences how much sunlight the northern and southern hemispheres receive relative to one another. This in tur... More » Science Time & Calendars

The light independent reactions of photosynthesis, known as the dark reactions, use ATP and NADPH generated during the light reactions to synthesize sugar precursors. In the most common scenario, called the Calvin Cycle,... More »

June 21st is the longest day of the year in the Northern Hemisphere because it is the summer solstice, which describes the tilt of the Earth's axis. This phenomenon is only observable outside of the tropics as it is the ... More »

The circle of illumination is the line that separates the Earth to create equal parts of day and night. It passes through the poles and allows the entire Earth to have an equal amount of time spent during the daylight an... More »

The Moon rotates on its axis and so has day and night much like the Earth does. However, the period of the Moon's rotation and its orbit around the Earth take the same amount of time, so the near side of the Moon is alwa... More »

The ecliptic is the course the sun is observed to take from the point of a view of Earth as it appears to revolve around Earth in a line that is inclined with respect to the rotation axis at 23.50, according to Georgia S... More »