How do seasons arise from the tilt of Earth’s axis?

angle: The space (usually measured in degrees) between two intersecting lines or surfaces at or close to the point where they meet.

Arctic: A region that falls within the Arctic Circle. The edge of that circle is defined as the northernmost point at which the sun is visible on the northern winter solstice and the southernmost point at which the midnight sun can be seen on the northern summer solstice. The high Arctic is that most northerly third of this region. It’s a region dominated by snow cover much of the year.

Arctic Circle: The northernmost point at which the sun is visible on the northern winter solstice and the southernmost point at which the midnight sun can be seen on the northern summer solstice.

average: (in science) A term for the arithmetic mean, which is the sum of a group of numbers that is then divided by the size of the group.

constant: Continuous or uninterrupted. (in mathematics) A number that is known and unchanging, usually based on some mathematical definition. For example, π (pi) is a constant equal to 3.14. . . and defined as the circumference of a circle divided by its diameter.

data: Facts and/or statistics collected together for analysis but not necessarily organized in a way that gives them meaning. For digital information (the type stored by computers), those data typically are numbers stored in a binary code, portrayed as strings of zeros and ones.

degree: (in geometry) A unit of measurement for angles. Each degree equals one three-hundred-and-sixtieth of the circumference of a circle.

equator: An imaginary line around Earth that divides Earth into the Northern and Southern Hemispheres.

factor: Something that plays a role in a particular condition or event; a contributor. (in math) The numbers (or any algebraic expressions) that can divide another number (or expression) evenly, with no remainder. For example, 2 and 5 are factors of 10 (as 10 can be divided by 2 and give you 5, with no leftovers).  Ten’s other factors are 1 and 10.

horizontal: A line or plane that runs left to right, much as the horizon appears to do when gazing into the distance.

laser: A device that generates an intense beam of coherent light of a single color. Lasers are used in drilling and cutting, alignment and guidance, in data storage and in surgery.

latitude: The distance from the equator measured in degrees (up to 90). Low latitudes are closer to the equator; high latitudes are closer to the poles.

longitude: The distance (measured in angular degrees) from an imaginary line — called the prime meridian — that would run across Earth’s surface from the North Pole to the South Pole, along the way passing through Greenwich, England.

longitudinal: (in research) Using data gathered from study subjects over a long period of time.

model: A simulation of a real-world event (usually using a computer) that has been developed to predict one or more likely outcomes. Or an individual that is meant to display how something would work in or look on others.

moon: The natural satellite of any planet.

online: (n.) On the internet. (adj.) A term for what can be found or accessed on the internet.

orbit: The curved path of a celestial object or spacecraft around a galaxy, star, planet or moon. One complete circuit around a celestial body.

Pacific: The largest of the world’s five oceans. It separates Asia and Australia to the west from North and South America to the east. The term can also refer to island nations that sit within the Pacific Ocean.

parallel: An adjective that describes two things that are side by side and have the same distance between their parts. In the word “all,” the final two letters are parallel lines. Or two things, events or processes that have much in common if compared side by side.

perpendicular: An adjective that describes two things that are situated approximately 90 degrees to each other. In the letter “T,” the top line of the letter is perpendicular to the bottom line.

PhD: (also known as a doctorate) A type of advanced degree offered by universities — typically after five or six years of study — for work that creates new knowledge. People qualify to begin this type of graduate study only after having first completed a college degree (a program that typically takes four years of study).

solar: Having to do with the sun or the radiation it emits. It comes from sol, Latin for sun.

solar energy: The energy in sunlight that can be captured as heat or converted into heat or electrical energy. Some people refer to wind power as a form of solar energy. The reason: Winds are driven by the variations in temperatures and the density of the air, both of which are affected by the solar heating of the air, ground and surface waters.

sun: The star at the center of Earth’s solar system. It is about 27,000 light-years from the center of the Milky Way galaxy. Also a term for any sunlike star.

surface area: The area of some material’s surface. In general, smaller materials and ones with rougher or more convoluted surfaces have a greater exterior surface area — per unit mass — than larger items or ones with smoother exteriors. That becomes important when chemical, biological or physical processes occur on a surface.

unit: (in measurements) A unit of measurement is a standard way of expressing a physical quantity. Units of measure provide context for what numerical values represent and so convey the magnitude of physical properties. Examples include inches, kilograms, ohms, gauss, decibels, kelvins and nanoseconds.

vertical: A term for the direction of a line or plane that runs up and down, as the vertical post for a streetlight does. It’s the opposite of horizontal, which would run parallel to the ground.