# Problem of the Week Problem B Are We There Yet?

Planets travel around the sun in elliptical orbits (ovals). Mercury is the planet closest to the sun. The distance between Earth and Mercury ranges from $$77\,000\,000\,$$km at its closest distance to $$222\,000\,000\,$$km at its farthest distance.

Because distances are so great in the solar system, scientists measure them in Astronomical Units, or AU. One AU is equal to the average distance between the Earth and the Sun, or about $$149\,600\,000\,$$km.

Complete the missing information in the table below.

Planet Distance in AU from Earth Distance in km from Earth Travel Time
Mars $$0.52$$
Venus $$61$$ days
Saturn $$1\,275\,000\,000$$
Neptune $$29.09$$

To calculate the travel time, assume you are travelling from Earth to the planet in a rocket at a speed of $$28\,000\,$$km per hour throughout your flight. Pick the most reasonable unit of measure for time (for example, $$15\,000$$ hours doesn’t mean much, but when divided by $$24$$ to get $$625$$ days, you know that it’s almost $$2$$ years).

Themes: Geometry, Number Sense