Galaxies & the Universe (G6-8)

How long does it approximately take for light to travel from Mars to Earth when they are closest?

Scientists estimate that there are _____ galaxies in the universe that can be seen from Earth.

Thousands of years ago, ancient _____ philosophers first suggested that the Milky Way might be made of far away stars that were close together.

The planets, moons, and stars make up less than ___ of all the mass in the universe. The rest lies in the realm of absolute darkness.

_____ is believed to be responsible for the expansion of the universe, and is considered to be the fifth force acting on matter that counteracts the force of gravity.

The distance between Earth and our Moon is 384400 kilometers, which could fit (select all that apply):

How long does it take for light to travel from Earth to our Moon?

How long does it take for light to travel from the Sun to Earth?

Our best estimates tell us that the Milky Way is made up of approximately ____ stars, and probably at least 100 billion planets in it. 

A light year is the distance light can travel in one year, nearly 5.9 trillion miles or 9.5 trillion kilometers. The Milky Way is massive, at least _____ light-years across.

There are four main parts in the Milky Way: