Astronomers deal with some of the largest numbers. Whether they are measuring the distance to the next galaxy, or the weight of Jupiter, the numbers are, well, "astronomically large"!
Here is a drawing of our Solar System. Each planet is a different size, and the planets vary in their distances from each other and from our Sun.
How do scientists calculate distances and sizes in the Universe? They use a number of different methods, including proportions, brightness, and parallax. To find the distance from Earth to an imaginary Planet x, two photographs are taken from Earth: one at sunset (point A), and the other 12 hours later at sunrise (point B). Throughout this period, the earth rotated on its axis, placing our observation sites apart by 7,928 miles, the diameter of planet Earth.
The formula below works only for very small angles, but if the planet or object is very far from Earth, then the answer is only approximate anyway. The number 57.3 is an equation constant, M is the distance we are finding, P is the angle of parallax, and d is the diameter of the Earth.
Scientists use mathematics to calculate sizes and distances in the universe, and to calculate the orbits of planets and the paths of satellites. It is hard to even imagine the number of calculations needed to send a space ship to the moon.
"On July 20, 1969, Neil Armstrong became the first human being to set foot on the Moon. The first step onto the Lunar surface from the Apollo 11 Lunar Module, the Eagle, fulfilled the promise of President John F. Kennedy that the U.S. would land a man on the Moon before the end of the decade. It was the highlight of an extended U.S. program to study and map the Moon, beginning with Ranger 7 impacting the Moon on July 31, 1964 and culminating with Apollo 17, which left the Moon on December 14, 1972. The scientific return from these missions was immensely important and included nearly complete high-resolution imaging of the lunar surface, lunar samples, topographic, seismic, and gravity data, and information on the lunar environment." These data, as well as data from the Galileo, Clementine, and many Soviet missions, are currently available from the NSSDC at