Space Concepts

Force of Gravity

Force of gravity is the theory that every object is attracted to every other object directly proportional to their masses and inversely proportional to the distance between them squared. When force of gravity is directly proportional to an object's masses (Fg~m), the greater the masses, the more gravitational force between. However, it is also indirectly proportional to the distance between the objects squared (Fg~1/d^2), meaning, the further away the objects are, the force of gravity becomes weaker. The equation you use to find force of gravity is Fg= Gm1m2/d^2. This means that force of gravity is equal to the gravitational constant times the masses of the first and second objects. Then you divide the product of that by distance squared. The unit for force of gravity is Newtons (N).

Gravitational Constant

Gravitational constant is a unit of measure that represents the gravitational effects in Newton's law of Universal Gravitation. The equation for gravitational constant is G= 6.67*10^-11 Nm^2/kg^-2. Gravitational constant is usually used when it is plugged into the equation for force for gravity. This mean, in the end, after going through an equation, the end unit is usually Newtons (N).

Orbital Period

This is the time it takes for a planet to orbit the Sun from one vernal equinox to the next in Earth time. Also known as the tropical orbit period, this is equal to a year on Earth. To find a planet's orbital period, use the formula T= 2(pi)r/v. In other words, you find the radius of the planet, multiplied by pi times two. Then you divide the product by the planet's velocity. After that you will have the planet's orbital period in seconds. Most likely, you should convert it to either days or years. Whichever makes more sense.

Orbital Velocity

Orbital velocity is the average velocity or speed of the planet as it orbits the Sun, in kilometers per second or miles per second. The formula used to find the orbital velocity is V=2(pi)r/T. In other words, multiply the radius of the planet by two pi. Then, divide the product by the orbital period, or time to get the orbital velocity in either m/s or km/s.

Obliquity to Orbit

Obliquity to orbit is the angle in degrees the axis of a planet is tilted relative to a line perpendicular to the planet's orbit around the Sun, north pole defined by right hand rule. Obliquity to orbit can help people predict surface temperatures of certain planets, how long the planet's seasons last, and even if a planet has seasons at all.