How Big Is the Universe? A Journey Into the Vast Unknown

How big is the universe?
It’s a question that stretches not just our curiosity—but the limits of our imagination.

From the planets in our solar system to the farthest galaxies ever observed, the scale of the cosmos is almost beyond comprehension. Let’s explore just how vast our universe really is and what science says about its size.

Start Small: Our Place in the Cosmic Neighborhood

To grasp the size of the universe, it helps to start close to home.

• Earth to Moon: ~384,400 km
• Earth to Sun (1 AU): ~150 million km
• Solar System width: ~9 billion km (up to the edge of the Kuiper Belt)

Even at light speed, it takes:

• 8 minutes to reach the Sun
• Over 4 years to reach the nearest star (Proxima Centauri)

We’re already talking in light-years — the distance light travels in one year (~9.46 trillion km)!

The Milky Way Galaxy: Home, Sweet Home

Our galaxy, the Milky Way, is a massive disk containing over 100 billion stars.

• Diameter: ~100,000 light-years
• Thickness: ~1,000 light-years
• It takes our solar system about 230 million years to orbit the galactic center once.

And guess what? The Milky Way is just one of billions of galaxies out there.

Observable Universe: The Part We Can See

Here’s where things get truly mind-bending.

The observable universe — the part we can detect with telescopes — stretches about 93 billion light-years across.

That’s because the universe has been expanding since the Big Bang (13.8 billion years ago). So even though light from distant galaxies started traveling billions of years ago, those galaxies are now much farther away due to expansion.

This observable bubble contains:

• ~2 trillion galaxies
• Countless stars, planets, black holes, and cosmic wonders

Is There More Beyond?

Absolutely — and that’s where the mystery begins.

The observable universe is not the whole universe. It’s just the part light has had time to reach us from.
The universe might be infinite — or it might curve back on itself in ways we can’t yet perceive.

There could be regions far beyond our sight with different physical laws, or even other universes (multiverse theory). We simply don’t know... yet.

So how big is the universe? The truth is, no one knows for sure.

What we do know is awe-inspiring: a cosmos that stretches tens of billions of light-years in every direction, full of mysteries, stars, and questions waiting to be answered.

We are just a tiny dot in a cosmic sea — and that only makes the journey more amazing.

For more information here is our Youtube channel: Science 101