Greg Chaffins Part of the NerdBeach Series “How Space Works“
The universe is already difficult enough to understand when it’s just sitting there being incomprehensibly enormous. But as if “endless cosmic void filled with stars and black holes” wasn’t weird enough, scientists eventually discovered something even stranger:
The entire universe is expanding.
Not just moving around. Not just galaxies drifting a little. The literal fabric of space itself is stretching outward in every direction all the time. Which means the universe is not a static backdrop where things happen. It’s more like a giant cosmic balloon that has been inflating for 13.8 billion years and shows no signs of calming down.
Naturally, this raises some questions.
Why is the universe expanding?
What is it expanding into?
How did we figure this out?
And why does every answer make reality sound more confusing?
Let’s stretch our brains a bit and break it down.
It All Starts With the Big Bang
- Big Bang Event: The universe began as an incredibly hot, dense point containing all matter, energy, and space.
- Expansion of the Universe: The Big Bang was the rapid expansion of space itself, not an explosion in space.
- Time of the Big Bang: The Big Bang occurred approximately 13.8 billion years ago.
To understand expansion, we need to start with the Big Bang. About 13.8 billion years ago, the universe began as an incredibly hot, dense point containing:
- all matter
- all energy
- all of space itself
Then suddenly everything expanded outward. And no, the Big Bang was not an explosion in space. It was:
the rapid expansion of space itself.
That distinction matters because the universe didn’t explode into empty space. Space itself began expanding everywhere at once. Which is already deeply rude to normal human logic.
Imagine Raisins in Expanding Bread Dough
- Universe Expansion Analogy: The universe expanding is like raisin bread dough rising, with galaxies as raisins moving farther apart as space itself stretches.
- Galaxies’ Movement: Galaxies are not moving through space but are carried along by the expanding space itself.
Scientists often explain expansion using the raisin bread analogy. Imagine:
- the universe is bread dough
- galaxies are raisins inside it
As the dough rises, every raisin gets farther from every other raisin. The raisins aren’t flying through the dough. The dough itself is expanding. That’s basically what’s happening with the universe.
Galaxies are not just zooming through empty space. Instead space itself is stretching between them. Which is somehow cooler and weirder.
How We Discovered Expansion
- Universe Expansion: The universe is expanding uniformly, with galaxies moving away from each other.
- Observation Evidence: Edwin Hubble observed that galaxies appear to be moving away from us, with farther galaxies moving faster.
- Relative Motion: The apparent motion of galaxies is due to the stretching of space itself, not because galaxies are moving through space.
For a long time, scientists assumed the universe was static. Then in the 1920s, astronomer Edwin Hubble observed something strange: Nearly all galaxies appeared to be moving away from us. And the farther away a galaxy was, the faster it seemed to be moving.
At first that sounds suspiciously like Earth is the center of everything. But no. What it really meant was:
The entire universe is expanding uniformly.
Every galaxy sees other galaxies moving away because space is stretching everywhere. No matter where you stand, it looks like everything else is receding. Which is either beautiful science or the universe gaslighting everyone equally.
Light Gets Stretched Too
- Redshift and Galaxy Movement: Redshift indicates that galaxies are moving away from us, with greater redshift corresponding to greater distance and faster movement.
- Redshift Mechanism: The expansion of space stretches light waves from distant galaxies, shifting them towards the red end of the spectrum.
- Evidence for Universe Expansion: The stretching of light waves, or redshift, provides evidence that the universe is expanding.
Scientists know galaxies are moving away because of something called redshift. When light travels from distant galaxies, the expansion of space stretches the light waves. As waves stretch, they shift toward the red end of the light spectrum. So:
- more redshift = farther away
- more redshift = moving away faster
Basically, scientists can tell the universe is expanding because:
the light itself gets stretched like cosmic taffy.
Physics remains delightfully weird.
Expansion Happens Everywhere
- Universe Expansion: The universe is expanding everywhere, not from a central point.
- Relative Stretching: Every region of space stretches relative to every other region.
- Center of the Universe: There is no center of the universe.
Here’s something strange: The universe is not expanding from one central point. There is no:
- middle of the universe
- “main expansion direction”
- special center spot
Expansion happens everywhere, all at once. Every region of space stretches relative to every other region. So asking “Where is the center of the universe?” is kind of like asking:
“Where is the center of the surface of a balloon?”
There isn’t one on the surface itself. Mind-bending, right?
The Expansion Is Speeding Up
- Universe Expansion: The universe is expanding faster over time, defying the initial assumption that gravity would slow it down.
- Dark Energy: A mysterious force driving the accelerated expansion of the universe, making up most of its composition.
- Current Understanding of Dark Energy: Scientists know it exists and drives acceleration but lack a definitive understanding of its nature.
Now here’s where things get extra bizarre. Scientists originally assumed expansion would gradually slow down because gravity should pull everything together. Makes sense. Except it isn’t slowing down.It’s actually speeding up.
The universe is expanding faster over time. Which means some mysterious force is overpowering gravity on cosmic scales. Scientists call this mystery:
Dark Energy
And what is dark energy? Excellent question. We have no idea. We know:
- it exists somehow
- it drives acceleration
- it makes up most of the universe
And that’s about it. So one of the most important forces in existence is currently labeled:
“Mysterious space stuff doing weird things.”
Very professional.
Why Doesn’t Expansion Pull Apart Everything?’
- Scale of Expansion: Expansion only matters across huge cosmic distances between galaxies and galaxy clusters.
- Local Effects of Expansion: Gravity and other forces overpower expansion on smaller scales.
- Stability of Structures: Planets, solar systems, and galaxies remain bound together due to these forces.
If space is expanding, you might wonder:
Why doesn’t Earth get bigger?
Why doesn’t the solar system stretch apart?
Why doesn’t my couch slowly drift away?
Because gravity and other forces overpower expansion on smaller scales. Expansion only matters across:
- huge cosmic distances
- between galaxies and galaxy clusters
So:
- planets stay together
- solar systems stay together
- galaxies mostly stay together internally
Only vast stretches of space between major structures are expanding noticeably. Which is good. Otherwise parking would become significantly harder.
What Is the Universe Expanding Into?
- Universe Expansion: The universe may not be expanding into anything, but rather creating more space as it expands.
- Mathematical Evidence: Current evidence suggests that the universe doesn’t need outside room.
- Nature of Expansion: The universe may simply be making more room as it expands.
This is one of the most common questions. And the answer is frustrating: Probably nothing. The universe may not be expanding into anything. It may simply be:
creating/stretching more space as it expands.
That sounds fake. But mathematically that’s what current evidence suggests. The universe doesn’t need outside room. It may simply be making more room as it goes.
Which is one of the most disrespectfully confusing concepts in science.
How Might It End?
- Possible Endings of the Universe: The Big Freeze and The Big Rip.
- The Big Freeze: Galaxies drift apart, stars die, and the universe becomes cold and dark.
- The Big Rip: Expansion tears apart everything in the universe.
If expansion keeps accelerating forever, scientists think the universe may end in one of several ways.
The Big Freeze
Galaxies drift apart until stars die and everything becomes cold and dark forever.
The Big Rip
Expansion gets so strong it eventually tears apart galaxies, stars, planets, atoms—everything.
Other Weird Possibilities
Because cosmology refuses to ever be simple. Basically future universe = probably bad vibes.
Expanding Since the Big Bang
The universe expands because space itself has been stretching ever since the Big Bang, carrying galaxies farther apart over billions of years. And somehow, for reasons we still don’t fully understand, that expansion is speeding up thanks to mysterious dark energy.
So the next time you look at the stars, remember: You’re living inside a universe where the fabric of reality itself is stretching outward endlessly in all directions… and even scientists are still kind of standing around saying,
“Honestly, this is getting weird.”
Nature remains gloriously unhinged.
This article is part of the NerdBeach series: How Space Works
