Solar System vs Galaxy vs Universe


A Very Big Question…

The solar system, the galaxy, and the universe, while all part of the same entire entity, are very different in their relative sizes and compositions. This article will break down the differences between them and discuss the evolution and facts about each.

What is the Solar System?

The solar system consists of the Sun and all of the objects that orbit around it, including planets, moons, asteroids, comets, and other celestial objects. The eight planets in our solar system are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. The solar system is held together by the gravitational pull of the Sun, and each planet and celestial object has its own unique characteristics, from the rocky terrain of Mars to the gas giant Jupiter.

The solar system was formed about 4.6 billion years ago from a giant cloud of gas and dust known as the solar nebula. Gravity caused the nebula to collapse, leading to the formation of the Sun at its center. The leftover material in the nebula began to clump together to form the planets and other celestial objects. This process is known as accretion, and it took millions of years for the process to be completed. Some of the leftover material also formed into smaller objects, like asteroids and comets. The exact process and timeline of the formation of the solar system are still being studied and are an active area of research in astronomy.

The Earth was formed during the process of the formation of the solar system in the accretion disk. In the center of this disk, the Sun formed, and the rest of the disk began to clump together to form the planets. The Earth was formed from the heavier elements that were closer to the Sun, which eventually clumped together to form our planet. Over time, the Earth’s surface cooled and solidified while keeping a molten core, allowing for the formation of oceans and volcanic activity, which led to the beginnings of life on Earth.

solar system

What is the Galaxy?

The Milky Way Galaxy was formed approximately 13 billion years ago. It is believed to have formed from the collision and merging of several smaller galaxies. The exact process of how this took place is still not completely understood. Still, it is believed that the Milky Way started as a small, compact cloud of gas and dust that gradually grew through the accretion of smaller clouds and through the merging of smaller galaxies. As the cloud of gas and dust collapsed, it formed stars and other celestial objects and eventually organized into the spiral shape that we observe today. The Milky Way has continued to grow and change over the billions of years since its formation, through the accretion of smaller galaxies and through the formation of new stars and other celestial objects.

The Milky Way is currently in the process of tearing apart its nearest satellites, the Large and Small Magellanic Clouds. Luckily, the Milky Way has not merged with a galaxy of similar mass in its entire 13 billion-year history, as the results would be catastrophic. The collision triggers the rapid formation of so many stars to where all of them form at once, and then eventually die out with no new stars to take their place, thereby causing the galaxy to become stagnant with stars all of the same age.

According to recent measurements, however, the Milky Way is on a collision course with its nearest major neighbor, the Andromeda Galaxy. In about 4 billion years, the two will collide, twisting themselves into an odd, unrecognizable shape and triggering rapid star formation.

What is the Universe?

The universe is everything that exists, including all matter, energy, and space. It encompasses all galaxies, stars, planets, and other celestial bodies, as well as all physical laws and constants that govern their behavior. The observable universe has a diameter of about 93 billion light-years and is not only expanding but is expanding at an accelerated rate.

We are in love with the amazing image below, which represents just a tiny sliver of the universe.

Photo Credit:

The beginning of the universe is believed to have occurred with the Big Bang, a massive explosion that happened approximately 13.8 billion years ago. This event marked the start of the universe’s expansion and the formation of the first stars and galaxies. The exact cause of the Big Bang is still unknown, but there are multiple hypotheses out there that attempt to explain it.

The most widely accepted idea is that the universe originated from a singularity, a point of infinite density and temperature, that caused the universe to expand explosively into what it is today.  Some other physicists believe that the universe was created by the collapse of a higher-dimensional object, one that released its energy into our plane to create our universe. Others believe that the Big Bang was caused by a quantum fluctuation, a random fluctuation of energy in the vacuum of space-time, which triggered the expansion of the universe. None of these have been definitively proven, but they do provide some interesting insights and explanations of the universe’s origins.

Universe vs Galaxy

The Milky Way is a large barred spiral galaxy with a diameter of about 100,000 light-years and contains hundreds of billions of stars, gas, and dust. The universe, on the other hand, is much larger and contains an estimated 2 trillion galaxies, each with its own collection of stars, gas, and dust. The observable universe has a diameter of about 94 billion light-years, while the entire universe is thought to be much larger, possibly infinite. This makes the diameter of the observable universe almost 1 million times larger in one dimension than our own galaxy!

milky way galaxy

So, all-in-all the Milky Way is just one of many galaxies in the universe, and our sun is just one of the hundreds of billions of stars in our galaxy, amongst trillions of other galaxies in the universe with their own stars as well.

Solar System vs Galaxy

The differences in scale between the solar system and the galaxy are vast and can be difficult to comprehend. The solar system, consisting of the sun and its orbiting planets and other objects, is relatively small compared to the scale of the galaxy. The average distance from the Earth to the Sun is about 93 million miles (150 million kilometers), while the diameter of the solar system is estimated to be about 100 astronomical units (AU). In comparison, our Milky Way galaxy is estimated to be about 100,000 light-years across ( ~6.4 billion AU) and contains billions of stars and other objects. The scale of the galaxy is so large that even at the speed of light, it would take 100,000 years to travel from one end of the galaxy to the other. These differences in scale demonstrate the vastness of the universe and the relatively small size of our own solar system within the grand scheme of things.

The formation of the solar system occurred over eight billion years after the formation of the Milky Way galaxy. The Milky Way galaxy is estimated to have formed about 13.2 billion years ago, shortly after the Big Bang. Over time, clouds of gas and dust within the galaxy began to condense and collapse to form stars and planetary systems, including our own solar system 4.6 billion years ago.

What Will Happen to the Universe in the Future?

The future of the universe is uncertain, and many scenarios have been proposed by astronomers and cosmologists. When it comes to the end of the universe, there are a few leading theories. One of the most popular theories is referred to as “the big bounce”. This theory proposes that, eventually, the universe will stop expanding and begin to contract on itself, eventually making its way back to the singularity from which it came. After reaching the point of a singularity, the universe will “bounce” back and form a new universe.

Another theory is called the “big freeze” or the “heat death” of the universe. In this scenario, the universe will continue to expand. Eventually, all matter will be evenly distributed, resulting in a state of maximum entropy where there is no energy available anymore for anything to happen. It will have expanded so much that no distant galaxies will be visible from our own Milky Way. Because of the even spread of energy, the universe will become the coldest possible temperature: just above absolute zero. Trillions of years later, galaxies will be gone. Stellar remnants will break apart, and all known matter will exist in the form of black holes, which will eventually radiate away as well.

A third cosmological model to predict the future of the universe is the “Big Rip.” The Big Rip is a theoretical scenario for the end of the universe in which the fabric of space-time is torn apart. According to this theory, the expansion of the universe will continue to accelerate until it reaches a point where the force of the expansion becomes stronger than the forces that hold matter itself together. As a result, everything from galaxies and stars to planets and even atoms will be torn apart, resulting in the complete destruction of the universe. This scenario is based on the idea that the universe is filled with a mysterious force known as dark energy, which is causing the expansion to accelerate. If this force continues to grow, it will eventually overcome the forces that hold matter together, leading to the Big Rip.

Heavy, But Interesting

The universe we live in is vast, containing trillions of galaxies with their own stars, planets, nebulae, and other celestial objects, which tells us that there is so much left to discover. Despite the advancements in scientific research, there is still so much that remains a mystery, from the formation of galaxies to the ultimate fate of the universe. However, the relentless pursuit of knowledge through scientific investigation continues to deepen our understanding of the universe and our place within it. With each new discovery, we are able to expand our view of the cosmos and gain new insights into its workings. The continued study of the universe, through observational and theoretical research, promises to reveal even more wonders and mysteries in the years to come.

Scroll to Top