Today is the Summer Solstice, the longest day of the year (in the Northern Hemisphere). Because Earth’s axis of rotation is tilted about 23.4 degrees relative to its orbit around the sun, this means that the different parts of the Earth receive the amount of light based on the position of the earth in its orbit around the sun. This tilt causes the earth’s seasons - From March to September, the Northern Hemisphere tilts more toward the sun, creating spring and summer, while in the Southern Hemisphere it’s fall and winter.