Scientists Say: Big Bang | Science News for Students

Scientists Say: Big Bang

This is the current theory about how our universe began
Jul 29, 2019 — 6:30 am EST
big bang

This image shows how the universe might have come to be, from a small dense point at left, through “quantum fluctuations” and then to the Big Bang. That time of rapid inflation left behind the light pattern that scientists see today — called cosmic background radiation. After a period called the “dark ages,” matter condensed and cooled, and stars and planets began to form. 

WMAP Science Team/NASA

Big Bang (noun, “Big Bang”)

This theory explains how our universe began. About 14 billion years ago, all the matter that makes up the universe was squashed into an incredibly small space. Because the matter was so condensed, it wasn’t in any form we would recognize today. No atoms, or even particles. Suddenly, though, that matter went through a rapid inflation — an explosion, in a way. That’s the Big Bang. The result was a super-hot mass of matter, including light and charged particles such as protons and electrons. The matter cooled slowly over billions of years. As it cooled, it formed elements such as hydrogen. The matter also began to clump together into stars and planets. At the same time, the universe kept on cooling and expanding. In fact, the universe is still cooling and expanding today. 

No one, of course, was around at the time of the Big Bang. And so scientists are always looking for more evidence that the Big Bang really occurred. For example, the Big Bang’s huge explosion should have sent ripples through space and time — gravitational waves. Using laser beams traveling down extremely long tubes, scientists have previously detected gravitational waves from two black holes colliding. In 2014, scientists thought they had detected gravitational waves from the Big Bang itself. Unfortunately, they were wrong. But don’t worry, they’re still looking.

In a sentence

The best evidence for the Big Bang is the remnants of the light — called cosmic background radiation — released from the original explosion.

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Power Words

(more about Power Words)

Big Bang     The rapid expansion of dense matter that, according to current theory, marked the origin of the universe. It is supported by physics’ current understanding of the composition and structure of the universe.

black hole     A region of space having a gravitational field so intense that no matter or radiation (including light) can escape.

condense     To become thicker and more dense. This could occur, for instance, when moisture evaporates out of a liquid. Condense can also mean to change from a gas or a vapor into a liquid. This could occur, for instance, when water molecules in the air join together to become droplets of water.

cosmic     An adjective that refers to the cosmos — the universe and everything within it.

density  The measure of how condensed some object is, found by dividing its mass by its volume.

electron     A negatively charged particle, usually found orbiting the outer regions of an atom; also, the carrier of electricity within solids.

element     A building block of some larger structure. (in chemistry) Each of more than one hundred substances for which the smallest unit of each is a single atom. Examples include hydrogen, oxygen, carbon, lithium and uranium.

hydrogen     The lightest element in the universe. As a gas, it is colorless, odorless and highly flammable. It’s an integral part of many fuels, fats and chemicals that make up living tissues. It’s made of a single proton (which serves as its nucleus) orbited by a single electron.

matter     Something that occupies space and has mass. Anything on Earth with matter will have a property described as "weight."

particle     A minute amount of something.

planet     A celestial object that orbits a star, is big enough for gravity to have squashed it into a roundish ball and has cleared other objects out of the way in its orbital neighborhood. To accomplish the third feat, the object must be big enough to have pulled neighboring objects into the planet itself or to have slung them around the planet and off into outer space. Astronomers of the International Astronomical Union (IAU) created this three-part scientific definition of a planet in August 2006 to determine Pluto’s status. Based on that definition, IAU ruled that Pluto did not qualify. The solar system now includes eight planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.

proton     A subatomic particle that is one of the basic building blocks of the atoms that make up matter. Protons belong to the family of particles known as hadrons.

radiation     (in physics) One of the three major ways that energy is transferred. (The other two are conduction and convection.) In radiation, electromagnetic waves carry energy from one place to another. Unlike conduction and convection, which need material to help transfer the energy, radiation can transfer energy across empty space.

remnant     Something that is leftover — from another piece of something, from another time or even some features from an earlier species.

star     The basic building block from which galaxies are made. Stars develop when gravity compacts clouds of gas. When they become dense enough to sustain nuclear-fusion reactions, stars will emit light and sometimes other forms of electromagnetic radiation. The sun is our closest star.

theory     (in science) A description of some aspect of the natural world based on extensive observations, tests and reason. A theory can also be a way of organizing a broad body of knowledge that applies in a broad range of circumstances to explain what will happen. Unlike the common definition of theory, a theory in science is not just a hunch. Ideas or conclusions that are based on a theory — and not yet on firm data or observations — are referred to as theoretical. Scientists who use mathematics and/or existing data to project what might happen in new situations are known as theorists.

universe     The entire cosmos: All things that exist throughout space and time. It has been expanding since its formation during an event known as the Big Bang, some 13.8 billion years ago (give or take a few hundred million years).

wave     A disturbance or variation that travels through space and matter in a regular, oscillating fashion.