What Is the Universe? A Beginner's Guide Introduction Have you ever looked up at the night sky and wondered what lies beyond the stars? The answer leads us to one of the biggest questions in science: What is the Universe? The universe includes everything that exists—space, time, stars, planets, galaxies, matter, and energy. Scientists believe the universe began about 13.8 billion years ago and has been expanding ever since. Although we have learned a great deal about it, many mysteries still remain. In this article, we will explore what the universe is and what it is made of. What Is the Universe? The universe is everything that exists. It includes all matter, energy, space, and time. Every star, planet, galaxy, black hole, and even the smallest particle is part of the universe. The Earth is part of the Solar System, which is located in the Milky Way Galaxy. The Milky Way is just one of billions of galaxies in the observable universe. Scientists use powerful telescopes an...