THE UNIVERSE

• Milky Way

• Interstellar Medium

• Our local Neighbourhood

• Perseus Arm

• Sagittarius Arm

The most distant galaxies are so far away that their light takes some 10 billion years to reach us, even though light rays travel so fast that they could go seven times round the world in a single second. Even astronomers cannot visualize these distances, but they can chart the Universe at different scales. They use a variety of methods to measure distances: some are appropriate for planets, others for stars or galaxies. Often astronomers build on the distances of nearer objects to push out farther, so each measurement becomes a step in a ladder of distances stretching across the Universe.