COMPLETE GUIDE TO THE UNIVERSE …FROM HOW IT BEGAN TO ITS ULITIMATE FATE
WHAT IS THE UNIVERSE?
The universe is a vast expanse of space and time filled with matter and energy. The word comes from the Latin universus, meaning ‘all things’, although ours may in fact be just one of many universes in a so-called multiverse. Over the course of billions of years, the simple atoms that formed in the early history of the universe have come together to produce countless galaxies, stars and solar systems like our own, separated by enormous distances. Meanwhile, nuclear processes inside stars, or triggered by their violent deaths, have steadily processed the first simple atoms to enrich later generations of stars, and the space between them, with heavier and more complex elements in an ongoing cosmic recycling scheme.
COSMIC DISTANCES
Astronomers put a scale to the universe by measuring the distance to remote galaxies. The most accurate way of doing this is to look for ‘standard candles’ – rare objects that are bright enough to see across vast distances and which obey physical rules that reveal their intrinsic luminosity or light output. The most useful standard candles are variable stars called Cepheids, whose pulsation period is linked to their average luminosity. The distance
