Universe
In astronomy, the
universe is "everything out there". It contains the
sun, all the planets including
Earth, all of our
galaxy, plus many other galaxies, and all of outer
space. It's huge - scientists with radio telescopes can only see a tiny part of it. It's so big that distances are measured in light years - the distance light travels in a whole year. To travel in a spaceship, using today's knowledge, to even the nearest
star would take
centuries. There are more stars than we can count or even see. In between the stars and galaxies it is mostly empty and very, very cold.