Can the Size of the Universe Be Calculated?

The universe is a vast whole that expands in dimensions of time and space, had a beginning, but whose boundaries are not precisely known, and contains billions of galaxies.

The Boundary Open to the Sky: How Much of the Universe Can We See?

Since its existence, humanity has looked to the sky and questioned its place in the universe. As our observations have advanced, we have come to realize that we can directly observe only a small portion of the universe. This visible part is scientifically defined as the observable universe. In fact, the universe itself may be much larger; however, we can only acquire information up to the distance from which light has had time to reach us.

Light and Time: Understanding Cosmic Distances

The age of the universe is estimated to be approximately 13.8 billion years. This information also helps us understand how long the light from the most distant celestial objects has been traveling. Because information in the universe reaches us largely through light. If light travels at approximately 300,000 kilometers per second, then a celestial object located 13.8 billion light-years away means that its light has been traveling since the earliest periods of the universe.

A Visualization of the Scale of the Universe (Generated with Artificial Intelligence)

However, while one might expect the diameter of the observable universe to be only 27.6 billion light-years, calculations reveal that this boundary is much larger: approximately 93 billion light-years. The primary reason for this large discrepancy is the expansion of the universe over time.

The Expanding Universe: Light Arrives from the Past as Distances Increase

The universe is not a fixed-size structure. On the contrary, it has a structure that expands over time. This expansion pushes large structures such as galaxy clusters farther apart. Therefore, when the light from a celestial object reaches us, that object was actually much closer to us than it is today. Over the elapsed time, the distance between us and the object has increased, creating a significant difference between the distance at the moment the light was emitted and the current distance.

As a result, a celestial object whose light we observe now may currently be much farther than 13.8 billion light-years away from us. Because while the light emitted 13.8 billion years ago has only just reached us, the light source has continued moving away from us during that entire period. In other words, what we currently see of the object is how it appeared 13.8 billion years ago. Who knows, perhaps in some distant region another civilization is observing the light from our Stone Age era, light that has only just arrived there.

Are We at the Center of the Universe?

Another important point concerns the perception of a center of the universe. The observable universe appears as a sphere centered on the observer. However, this does not imply the existence of a physical center. In reality, every observer in the universe perceives the universe similarly from their own location. This situation demonstrates that the universe is homogeneous and isotropic on large scales.

The absence of a center of the universe, or the fact that every location appears as if it were the center, reveals that the search for a spatial center in the classical sense is meaningless. Since the universe is a structure in which space-time itself is expanding, expansion occurs equally in all directions, and no fixed center can be defined.

The Invisible Universe: Depths Beyond the Reach of Light

We do not know what lies beyond the regions of the observable universe. Light from these areas has either not yet reached us or never will, due to the rate of the universe’s expansion. This means we lack definitive data about the entirety of the universe.

Nevertheless, scientists assume that the rest of the universe shares similar properties to the part we can observe, based on the matter density and structural patterns within our observable region. As long as this assumption is supported by observational data, it is reasonable to accept that the universe is largely structured similarly throughout.

The Most Distant Galaxy from Earth (AA)

Between the Known and the Unknown Universe

The universe challenges the limits of the human mind not only by its physical scale but also by its inherently difficult-to-comprehend structure. The observable universe offers us a vast window; however, beyond this window lies an immense realm of the unknown. This unknown makes it impossible to make a definitive and irrefutable calculation regarding the total size of the universe.

Knowing that the universe is expanding allows us to form deeper insights into its origin. Yet it also reveals how little we truly know. The universe beyond our observable limits may never be directly explored. But this does not hinder the human mind from pushing its boundaries further, as long as curiosity and the desire for scientific discovery endure.