The Universe's vastness is a concept that often leaves us in awe. While scientists debate whether it might be infinite, the portion we can observe, known as the 'visible Universe', is so immense that it challenges our understanding. Let's step back and contemplate our minuscule presence in this grand cosmic theatre.

To begin, let’s focus on Earth—a remarkable, wet sphere teeming with life. The only known home for life, except for a few fortunate astronauts aboard the International Space Station, which orbits merely 408 km above our planet's surface.

Now, let's put Earth's dimensions into perspective. The planet has a diameter of 12,742 km (7,917.5 mi) and a circumference of 40,075 km (24,901 mi). These figures can feel abstract, so let’s relate them to something tangible.

Imagine the entire population of Australia (approximately 25.5 million people) lying down in a line. With an average height of 1.65 m (5 ft 5 in), they would stretch around the Earth’s equator—plus, we’d have over a million extra Australians! If we did the same with the USA, they would wrap around the Earth more than 13 times.

If you still struggle to visualize Earth's size, picture this: if there were a road encircling the planet and you could drive nonstop at 70 mph (112.7 kph), it would take you 14 days, 19 hours, and 35 minutes to complete a lap—without any breaks!

All of human history and the natural world has unfolded on this single planet, which feels like an endless array of landscapes, oceans, and coffee shops—our home.

As we zoom out further, we encounter the Solar System, which encompasses Earth, other planets, numerous asteroids, and comets, all orbiting our star—a glowing ball of plasma.

The boundaries of our Solar System are somewhat unclear; anything that orbits the Sun could be considered part of it. Presently, the furthest confirmed object from the Sun is the dwarf planet Sedna. While the existence of the Oort cloud may extend further, it remains a topic of debate.

Sedna boasts an elongated orbit, taking about 11,400 years to complete one rotation. Its closest point is 73 times the distance from Earth to the Sun (73 AU), while at its furthest, it reaches an astonishing 900 AU away, roughly 130 billion km (80.77 billion mi).

If we define the Solar System's boundary at that distance, it becomes a staggering expanse. Traveling from Earth to this outer limit at the maximum speed achieved by humans—24,791 mph (39,897 kph) by the Apollo 10 astronauts—would require nearly 385 years. To arrive at this point today, one would have needed to leave Earth in 1635, during Charles I's reign in Britain.

For those of us not accustomed to such speeds, let’s consider a more relatable option: a Boeing 747-8i, which flies at 659 mph (1,060.5 kph). Even at this pace, the journey would take approximately 14,477 years. If you embarked on this flight today, you would have to set off when agriculture was first developed.

Moving outward, we next encounter the Milky Way galaxy. Measuring 105,700 light-years across, it represents a significant leap from our Solar System.

If we lined up 372 million Solar Systems, they would span the same width as the Milky Way. This number surpasses Twitter's user count (around 330 million at the time of writing).

Similarly, to align Earth side by side, we would need 78 billion of them—an amount slightly less than the yearly clothing purchases worldwide.

Crossing the Milky Way in a conventional spacecraft would be impractical and take eons. The only feasible method for humans to traverse it involves hypothetical wormholes, whose existence remains uncertain.

The Milky Way is home to approximately 250 billion stars, nearly double the number of mammals on Earth (about 130 billion). These stars are all located more than five light-years away, indicating that while our cosmic neighborhood is populated, it is not congested.

However, the Milky Way is just one of many galaxies. It is estimated that there are around 2 trillion galaxies in the observable Universe, separated by an average distance of 9.9 million light-years. Such enormous figures can be difficult to grasp, so let’s find some relatable comparisons.

This quantity of galaxies is akin to the number of cells in a newborn baby, which average around 100 micrometers in size. Unlike the cells in a baby, however, these galaxies are spaced sufficiently apart, with enough room to fit approximately 93 Milky Ways in between.

The Universe is rich with galaxies yet remains far from cramped. But what about the most distant object we can observe?

The farthest known galaxy is GN-z11, positioned 31.96 billion light-years away from Earth. This raises an intriguing question: how can we observe something so distant when the Universe is only 13.8 billion years old?

In reality, we don’t see this galaxy at that distance. It formed just 400 million years after the Big Bang, meaning the light we observe has been traveling for 13.4 billion years. Since that time, the galaxy has moved away from us due to the expansion of space, so the light we see is from an ancient galaxy that is now 31.96 billion light-years distant.

We could fit around 302,365 Milky Ways between us and GN-z11, a number comparable to the total of wolves (both wild and captive) alive today or the grains of rice in a 5.5 kg bag.

What about the theoretical limit of the observable Universe? You might expect it to measure 13.8 billion light-years based on the Universe's age, but as GN-z11 illustrates, the expansion of space means that the further we look, the deeper back in time we see. Thus, the estimated diameter of the observable Universe is 93 billion light-years.

Nevertheless, we cannot 'see' objects that far away. For us to observe an object 93 billion light-years distant, its light would need to have been emitted during the Big Bang. Unfortunately, no celestial body emitted light that early in the Universe's history (for more information, see my article on Did The Big Bang Really Go Bang?).

This is the vastness of the Universe from our viewpoint. Anything beyond 93 billion light-years will never influence us, as information cannot travel quickly enough to reach us, even if it had originated at the Big Bang.

So, how vast is 93 billion light-years? You could fit 880,000 Milky Ways in a line across the diameter of the observable Universe. This figure is roughly equivalent to the population of Jacksonville, Florida, or the number of African buffalo alive today.

To visualize Earths in this context, we would need 68.6 quadrillion of them—an amount comparable to the number of molecules we breathe in over two days.

Thus, we have explored the staggering scale of the Universe. This cosmic journey reminds us of our smallness, yet it is essential to remember that within this vastness, each individual remains unique.