What is the Universe? Everything around us, like Earth, the sky, plants, animals, stars, planets. It's all part of something larger called the "Universe." Universe includes all we can see and things beyond our reach. Contains stars, planets, moons, galaxies, and space itself. We are just a tiny part of this vast space. Observable Universe The part of the Universe we can see and measure with telescopes. Doesn’t mean this is the whole Universe—just what’s visible with our tools. Enormous size, about 93 billion light-years across. A light-year is the distance light travels in one year—extremely fast! Our Journey Through the Universe Begins with the "Big Bang," the event scientists think started it all. We learn how stars, galaxies, and planets formed after the Big Bang. Our Solar System and Earth were also created during this journey. Explore amazing objects like black holes, dark matter, and dark energy. Concepts are explained with examples so we can understand better. Basic Concepts: Time, Space, and Matter Time: Shows the sequence of events—past, present, and future. For example, we were babies (past), are now grown (present), and will grow older (future). Space: The empty area where planets, stars, and galaxies exist. Space is vast and has no boundaries; it includes everything around us. Matter: The substance that makes up everything we see and touch. Comes in three forms: solid, liquid, and gas. Everything, including us, is made of atoms and particles. The Big Bang and the Beginning of the Universe Theory that the Universe began from a tiny, high-energy point. This point expanded, spreading matter and energy everywhere. The Big Bang happened about 13.8 billion years ago. The Universe is still expanding today, moving galaxies apart. Formation of Particles and Elements After the Big Bang, it was hot and dense; basic particles formed. Particles like protons and neutrons combined to form hydrogen and helium. These became the building blocks for stars, galaxies, and planets. Process known as "nucleosynthesis" created the first elements. Formation of Stars and Galaxies Gravity pulled scattered gas clouds together to form dense areas. Dense areas got hot and began nuclear reactions, creating stars. Stars grouped into clusters, which became galaxies. Galaxies come in different shapes: spiral (like the Milky Way), elliptical, and irregular. Our Solar System The Sun: Center of the Solar System; gives light, heat, and energy. Formed 4.6 billion years ago from a cloud of gas and dust. Nuclear fusion in the Sun creates energy, allowing life on Earth. Earth: Has the perfect distance from the Sun for life. Atmosphere protects life from harmful rays and keeps temperatures balanced. Water, essential for life, is in oceans, rivers, and lakes. Moon: Likely formed after a large object collided with Earth. Affects Earth’s tides and stabilizes its rotation. Helps keep Earth’s seasons steady. Black Holes and Other Cosmic Phenomena Black Holes: Form when massive stars collapse after running out of fuel. Gravity is so strong that not even light can escape. Known as the "event horizon," beyond which nothing can return. Neutron Stars: Result from smaller star collapses, extremely dense. Pulsars: Neutron stars that spin and emit regular beams of light. Quasars: Very bright objects powered by black holes at galaxy centers.
