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In this blog, we explore the atom and the cosmos. What are they made of? What is their purpose? What is the difference between them?
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The Atom
Atoms are the basic units of matter and the defining structure of elements. The term “atom” comes from the Greek word for indivisible, because it was once thought that atoms were the smallest things in the universe and could not be divided. The structure of an atom is a central nucleus composed of protons and neutrons with electrons orbiting around this nucleus.
What is an atom?
At its simplest, an atom is the smallest particle of an element that has the chemical properties of that element. The first accurate description of the atom was given by the Greek philosopher Democritus, who believed that all things were composed of indivisible particles he called “atomos.” Although other scientists had earlier proposed the existence of some indivisible form of matter, it was not until the 19th century that advances in both experimental techniques and theoretical understanding led to the development of modern atomic theory.
In 1897, British physicist J.J. Thomson discovered the electron, which he determined was a component of atoms. Thomson’s model of the atom consisted of a sphere of positive charge with electrons embedded in it like raisins in a cake. In 1911, New Zealand-born physicist Ernest Rutherford discovered that atoms consisted mostly of empty space with a tiny, dense nucleus containing most of the atom’s mass. Rutherford also discovered that atoms could be physically divided into smaller parts—the protons and neutrons—although he did not know at the time what these particles were made of.
It wasn’t until 1932 that James Chadwick discovered the neutron, completing our modern understanding of the atomic structure. In his model, known as the Rutherford model, electrons orbit around a small, dense nucleus composed of protons and neutrons. The number of protons in an nucleus determines which element an atom is—for example, all atoms with six protons in their nucleus are carbon atoms.
The structure of an atom
An atom is the smallest particle of an element that has the chemical properties of that element. The structure of an atom is a central nucleus composed of protons and neutrons with electrons orbiting around this nucleus.
The history of the atom
In ancient times, the Greek philosopher Democritus proposed that everything in the universe is made up of tiny, indivisible particles that he called atoms. This was an insightful idea, but Democritus had no way of knowing whether atoms actually existed or what they might be like. The concept of the atom lay dormant for more than 2,000 years until the early 1800s, when a series of discoveries revealed that atoms are real and have measurable properties.
In 1803, English physicist John Dalton used the results of careful measurements to develop a model of the atom. Dalton proposed that each element is composed of atoms that are identical in size and mass. He also found that when elements combine to form compounds, their atoms join together in simple whole-number ratios. For example, water always contains two hydrogen atoms for every one oxygen atom. These discoveries helped chemists understand the basic principles of how atoms combine to form molecules.
In 1897, New Zealand-born physicist Ernest Rutherford performed a series of experiments in which he bombarded a sheet of metal with alpha particles—a type of radiation emitted by some radioactive elements. Rutherford expected the alpha particles to pass straight through the metal without being deflected. To his surprise, he found that some particles were scattered at large angles while others passed through undeflected. Rutherford realized that his results could be explained if atom were mostly empty space with a tiny, dense nucleus containing most of its mass. In 1911, he won the Nobel Prize in Chemistry for this discovery.
Over the next few decades, scientists developed increasingly sophisticated models of the atom based on Rutherford’s nuclear model. In 1913, Danish physicist Niels Bohr proposed that electrons orbit the nucleus like planets orbiting the sun. He also suggested that these orbits are quantized—that is, they can only have certain allowed values for their energy. This model explained many previously unexplained experimental results and was a major step forward in understanding atomic structure. Bohr’s model was later refined by other scientists including German physicist Werner Heisenberg and Austrian physicist Erwin Schrödinger.
The Cosmos
The cosmos is all of physical existence, including both the material universe and the invisible, spiritual world. It encompasses not only the stars and planets, but also the infinite space between them. The cosmos is also the home of God and the abode of the soul.
What is the cosmos?
In its simplest form, the cosmos is everything. It’s the sum total of all matter and energy in the universe, from the smallest particle to the Big Bang itself. In other words, it’s everything that exists.
The cosmos is huge beyond our ability to comprehend. The observable universe is more than 93 billion light years across. That means if you could travel at the speed of light, it would take you 93 billion years to get from one side to the other!
And that’s just the part of the universe we can see. It’s estimated that there is much more beyond our view, hidden from us by the limits of light and time.
The study of the cosmos is called cosmology, and it’s one of humanity’s oldest pursuits. For thousands of years, we’ve looked up at the stars and wondered about their mysteries. In recent centuries, we’ve made great strides in understanding our place in the universe. With powerful telescopes and advanced math and physics, we’ve uncovered some of cosmology’s biggest secrets.
But there’s still so much we don’t know. With each new discovery, we realize just how little we comprehend about this vast and fascinating cosmos we call home.
The structure of the cosmos
The cosmos is believed to have started with a Big Bang about 14 billion years ago. All matter in the universe emerged from a tiny point of infinite density and temperature.
In the first fraction of a second, the universe underwent an incredible expansion, doubling in size at least 90 times. This inflationary period created the space-time fabric of the universe and generated the seeds for all the structures that would come later: galaxies, stars, planets, and even us.
As the universe expanded and cooled, matter began to coalesce into clumps under the influence of gravity. The lightest elements, hydrogen and helium, formed the first stars and galaxies. Over time, these primitive objects evolved and grew more complex as heavy elements were synthesized in their nuclear furnaces.
Today, our best understanding of how the cosmos works is encapsulated in a theory called “the standard model of cosmology.” This theory describes the evolution of the universe from its earliest moments until today, and it has been tested against a wide range of observational data.
The history of the cosmos
The cosmos is all of space and everything in it. It began with the Big Bang, an unimaginably huge explosion that created everything we see today. Over the ensuing billions of years, the universe has continued to expand and change. Galaxies have formed and collided. Stars have been born and have died. And on our tiny planet, life has appeared and evolved.
Today, we are still learning about the cosmos and our place in it. We have sent spacecraft to explore other worlds, and we are using powerful telescopes to study distant galaxies. We are also learning more about the history of our own planet, and how the solar system came to be.
There is much still to be discovered, but each new discovery brings us closer to understanding the cosmos—and our place in it.
