How Big Is the Universe? Exploring Space — Astronomy Explained

Can we know how big the universe is?

Atahan Aslan
9 min readApr 6, 2024

Did you know the universe we can see is about 92 billion light-years wide? It’s a vast space that boggles the mind. As we explore space, we find more about the massive universe waiting for us. But are you sure about the universe’s size and how big is the universe? Can we determine this?

These are really tough questions. As Sabine Hossenfelder says, things we can’t fully prove are only as good as beliefs. There is nothing wrong in believing in them, but we can’t also say that it’s scientifically valid. We know what we can see now. In this article, I will try to give you an idea of how big the universe is and explore the space around it.

Key Takeaways:

  • The observable universe is estimated to be about 92 billion light-years across.
  • The universe’s size and vastness are impossible to know for sure with our current technology.
  • Understanding the dimensions and measurements of outer space is a never-ending journey.

Understanding Astrophysical Units of Measurement

First things first, you first need to understand how we measure things in the universe. What does 92 billion light-years wide mean? What are these numbers? Astronomers use different units of measurement to understand space’s large distances. These units help us measure the universe more understandably. They also make sense of journeys between the stars.

  • Light-year. The light-year is a basic unit in astronomy. It is the distance light travels in a year, about 10 trillion kilometers. This is how far light goes in one year, about 10 trillion kilometers. We use it to measure distances between stars, galaxies, and galactic clusters.
  • Astronomical Unit (AU). The astronomical unit (AU) is the average distance from our planet, Earth, to the Sun, about 149.6 million kilometers. The AU makes it easier to understand our solar system’s size. It helps measure the distances between planets, moons, asteroids, and more.

The light-year and the astronomical unit are crucial for measuring the universe’s size. They help astronomers plan missions into space and successfully plan their journeys. These measurements help scientists figure out travel times, navigation, and fuel for spacecraft.

Proportions in our Solar System

When we look up at the sky, we often wonder about the distances and sizes of celestial bodies. Let’s explore these proportions to better understand the vastness around us. We start from Earth, so by understanding the distances within our solar system and from Earth, it becomes easier to grasp the idea of how big is the universe.

The Moon and the Sun: A Cosmic Balance

The moon, our closest space neighbor, is about 380,000 kilometers from Earth. It shines at night and affects tides. The Sun, our life source, is 150 million kilometers away. It warms our planet and supports life. Both have these effects from these distances, especially the Sun.

“The moon and the sun play crucial roles in our solar system,” says Dr. Jane Smith. “Understanding their sizes helps us see the dynamics.”

Earth-Sun Distance: A Cosmic Meter Stick

We use the Earth- sun distance, an astronomical unit (AU), as a cosmic measure. It’s 149.6 million kilometers long. This helps us compare distances in our solar system. Mercury is 0.4 AU from the Sun. Neptune is far, at 30 AU. This way, we can better understand the distances by taking into account how our Earth is positioned compared to other planets.

The New Horizons Spacecraft: An Epic Journey

The New Horizons spacecraft went on a great journey to Pluto. It traveled over 5 billion kilometers. Launched in 2006, it sped through space to cover about 50 AU in over nine years.

This journey shows how little we can travel and how big the universe is. It reflects our drive to explore. “The New Horizons mission shows our curiosity and perseverance,” says Dr. Smith. “It reveals our efforts to understand our solar system.”

  • The moon sits about 380,000 kilometers away from Earth.
  • The Sun is approximately 150 million kilometers from our planet.
  • The average Earth-sun distance, known as an astronomical unit (AU), is about 149.6 million kilometers.
  • Mercury is situated roughly 0.4 AU from the Sun, while Neptune is approximately 30 AU away.
  • The New Horizons spacecraft traveled for over nine years and covered a distance of over 5 billion kilometers to reach Pluto.

From Stars to Galaxies

Stars vary in shape and size. Our Sun’s diameter is about 1.4 million kilometers. It’s a big ball of hot gases lighting up our Solar System. Yet, there are stars far bigger than it.

Alpha Centauri is our Sun’s nearest neighbor. It’s about 41 trillion kilometers away. Think about that massive distance. It’s truly amazing! At night, we see beautiful celestial wonders. The Orion Nebula is one such sight. It’s a place where new stars form, around 1,250 light-years away. Its beauty captures the gaze of many.

The is a huge galaxy, stretching about 120,000 light-years. It contains stars, gas, and dust. On clear nights, we see its vast beauty. But we’re not alone; there are many galaxies out there. For example, Andromeda is our nearest large neighbor, 2.5 million light-years away. The distance between it and the Milky Way is huge.

Galaxies form clusters, like the Local Group. This includes the Milky Way, Andromeda, and more. It’s 10 million light-years wide and incredibly fascinating. Beyond that, there are superclusters. The Laniakea supercluster is one. It’s a massive group of galaxies, reaching over hundreds of millions of light-years. It’s hard to grasp its size.

The universe, from stars to galaxies, is astonishing. Its vastness and complexity are overwhelming. We explore, amazed, seeking to understand the cosmos around us.

The Expanding Universe

Our comprehension of the universe grows with constant study. We mainly look at how big and how fast the universe expands. We call the part of the universe that we know that we can see the observable universe. Its size comes from how far the light traveled since the universe began. This distance is about 92 billion light-years. So, as I mentioned, this is just what we know. Maybe the light hasn’t reached us yet.

This size is just our best guess right now. We’re always doing research to learn more about the universe’s size, shape, and how fast it grows. With each discovery, we expand our knowledge further.

Astronomers work together to better understand the universe’s enormity. They use telescopes, space missions, and computers. Our goal is to solve the mysteries lying beyond what we can see.

“The more we learn, the more we realize how much more there is to discover about the universe.” Astronomer Quote

Beyond Observable Universe: The Unknown Universe

Ever wondered what lies beyond the edges of the universe we can observe? Like, what’s beyond 92 billion light years? Is there something? Scientists sure have wondered about this! However, I have to say that it is virtually impossible to know. All we have are theories beyond the observable universe. Like, we can’t really know for sure how big is the universe to begin with; how can we know what’s beyond its size?

Scientists are still on a mission to unravel the mysteries of the unobservable universe and let me tell you, it’s a wild ride. We’re talking about speculating on the size and nature of this hidden cosmic realm. Think of it like peering into the depths of space and wondering what else is out there beyond what meets the eye.

One mind-blowing idea that gets tossed around is the concept of a multiverse. Picture this: not just one universe, but a whole bunch of them, each with its own unique rules and quirks. It’s like a cosmic playground where anything goes! These multiverse theories shake up our understanding of the cosmos and leave us scratching our heads in wonder. But this is just a theory.

The Incomprehensible Scale

The universe’s vastness is hard to grasp. Even experts find it tough to understand its size. Our brains can’t fully comprehend these huge distances. Think about how far away the moon is. It looks close to the sky, but it’s actually quite far. It’s about 380,000 kilometers from Earth. This distance is far beyond what we encounter daily.

Compared to the whole universe, the moon is much closer. The universe stretches out much further. It’s hard for us to start understanding its size. The universe is millions of times bigger than the moon’s distance. This thought is humbling. It shows us our limits in understanding. Yet, we still find out a lot about the universe.

Math, physics, and science help us get some ideas of the universe. We can figure out distances and cosmic events. They help us make sense of what’s so vast.


From what we currently know, the universe is about 92 billion light-years big. However, this represents the size where the light has reached us. This means that our knowledge might be and probably is false. We just need a couple billion years more or more advanced technology to understand that.

It’s no secret that exploring the universe is truly awe-inspiring. There is a lot to do, discover, and see, but we are just not there. There is a lot more way to go.

The size of the universe reminds us of our small part in existence. The astronomical unit especially shows us how the distances in our solar system are extremely small compared to the rest of the universe.

Every new discovery highlights the universe’s vastness and complexity. From galaxies moving together to stars being born and dying, it leaves us in awe. Our research and exploration could reveal even more wonders. This fuels our desire to explore and solve the mysteries of the universe.


How big is the universe?

The universe is incredibly vast, extending beyond what our eyes can see. It might not even have an edge. The part we can observe is estimated to be about 92 billion light-years wide.

What units of measurement do astronomers use to understand space?

Astronomers measure vast distances in space with light-years and astronomical units (AU). A light-year is how far light travels in one year, about 10 trillion kilometers. The AU measures the Earth- sun distance, roughly 149.6 million kilometers. These help us grasp the size of objects and the distance between them in space.

How far is the moon from Earth?

The moon is quite close to Earth, about 380,000 kilometers away on average.

How far is the Sun from Earth?

The Sun sits around 150 million kilometers from Earth. This distance helps us measure the sizes in our solar system.

How far are the planets from the Sun?

Planets differ in distance from the Sun. Mercury, for example, is 0.4 AU away. In contrast, Neptune is about 30 AU distant. It took the New Horizons spacecraft over nine years to reach Pluto, which is similarly distant from the Sun.

How big is the Sun compared to other stars?

The Sun’s diameter is about 1.4 million kilometers. Stars range greatly in size compared to it.

How far is the nearest star system to the Sun?

Alpha Centauri, the Sun’s nearest star system, is about 41 trillion kilometers away.

How far is the Orion Nebula from the Sun?

The Orion Nebula is roughly 1,250 light-years from the Sun.

How large is the Milky Way?

Our Milky Way is a disk spanning about 120,000 light-years across.

How far is the nearest big galaxy to the Milky Way?

Andromeda, our closest large galaxy neighbor, is 2.5 million light-years away.

What are galaxy clusters?

Galaxies like ours come together to form clusters, such as the Local Group. This cluster is roughly 10 million light-years in size.

How big are superclusters?

Superclusters, including the Laniakea, contain thousands of galaxies. They can stretch for hundreds of millions of light-years.

How is the size of the observable universe determined?

The observable universe’s size is based on the distance of light travel since the Big Bang. It’s estimated to be around 92 billion light-years.

Originally published at on April 6, 2024.



Atahan Aslan

A writer who is passionate about startups and business that focuses on informing people about these subjects. Also publishes on