From the mockery-born ‘Big Bang’ theory to the mysteries of dark matter and dark energy that make up 95% of the universe, follow humanity’s great intellectual exploration.
- Four key pieces of evidence supporting the Big Bang theory, the origin of our existence
- The nature of dark matter and dark energy, which constitute 95% of the universe
- New horizons in cosmology opened by the James Webb Space Telescope
The Great Beginning Born from Mockery: The Big Bang Theory
Did you know? The name of the Big Bang theory, which explains the origin of our existence, actually started as a term of ridicule and sarcasm. In 1949, astronomer Fred Hoyle was a supporter of the ‘Steady-State’ theory, believing the universe was eternal without a beginning. To belittle the competing idea that the universe began from a single point, he sarcastically said, “This idea called the ‘big bang’…”
Ironically, history adopted the name he mocked because it was so intuitive and easy to remember. In the end, the theory’s strongest opponent unknowingly became its best marketer.
However, this name caused a fatal misunderstanding. I myself initially imagined the Big Bang as a bomb exploding with a ‘bang’ in empty space. But this is the first misconception to correct. The Big Bang was not an explosion inside pre-existing space. It was an event where space itself began expanding simultaneously at every point.
This article aims to clear up that misunderstanding and follow the 13.8 billion-year history of the universe as one grand ‘detective story.’ Shall we search for the fingerprints left at the cosmic crime scene together?
Decisive Evidence of the Big Bang: Four Cosmic Fingerprints
Like every great detective story, the Big Bang theory revealed its truth through decisive clues—‘fingerprints’—left throughout the universe.
Clue #1: The Whisper of Receding Galaxies (Cosmic Expansion)
In the 1920s, American astronomer Edwin Hubble proved that the ‘spiral nebulae’ in the night sky were actually other massive galaxies beyond our own.
His real revolution began when analyzing the light from these external galaxies. He discovered that almost all galaxies showed a phenomenon called ‘redshift’, meaning their light wavelengths were stretched, indicating they were moving away from us.
Furthermore, he found the astonishing law that the farther a galaxy is, the faster it moves away. This was the first observational evidence that the universe is expanding uniformly in all directions.
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Clue #2: The First Light of the Universe, the Cosmic Microwave Background
The smoking gun for the Big Bang theory was accidentally discovered in 1964 by Arno Penzias and Robert Wilson at Bell Labs.
While trying to eliminate mysterious noise picked up by a giant antenna, they realized this noise was the ‘afterglow’ left from the hot early universe cooling down, known as the Cosmic Microwave Background (CMB).
About 380,000 years after the Big Bang, light trapped in a fog of matter was finally free to spread—the ‘first light.’ This light has cooled over 13.8 billion years of cosmic expansion and now reaches us as cold microwaves at about 2.7 K.
Clue #3: The First Three Minutes, the Universe’s Element Recipe (Big Bang Nucleosynthesis)
In just three minutes after the Big Bang, the entire universe became a giant nuclear fusion factory, creating the basic building blocks of matter we see today. This process is called Big Bang Nucleosynthesis.
Theory predicts that during these three minutes, the lightest elements, hydrogen and helium, were mainly produced in a mass ratio of about 3:1. Remarkably, the elemental ratios observed in the oldest gas clouds today exactly match this prediction.
Clue #4: Recreating the ‘Primordial Soup’ in the Laboratory
While we cannot travel back 13.8 billion years in a time machine, we can recreate that moment on Earth. The Large Hadron Collider (LHC) at CERN is just such a place.
Scientists collide protons at near light speed to reproduce the state of the universe just one millionth of a second after the Big Bang, called the Quark-Gluon Plasma—the ‘primordial cosmic soup.’ These experiments directly test the physics of the early universe, refining the Big Bang theory.
| Evidence | Observation / Experiment | What It Means |
|---|---|---|
| Cosmic Expansion | More distant galaxies move away faster (redshift phenomenon). | The universe was once a smaller, hotter single point. |
| Cosmic Microwave Background | Nearly uniform microwave temperature observed in all directions. | The ‘afterglow’ or ‘first light’ left from the hot early universe. |
| Element Ratios | Hydrogen to helium mass ratio about 3:1 observed across the universe. | Matches the nucleosynthesis results from the first 3 minutes after the Big Bang. |
| Particle Accelerator Experiments | Recreate quark-gluon plasma state via proton/heavy ion collisions. | Experimentally confirms early universe physics matches current theory. |
The Mystery of Modern Cosmology: The Invisible 95% of the Universe
Although the Big Bang theory was a great success, this detective story led us into deeper, darker mysteries. All the stars, galaxies, planets, and even ourselves make up only about 5% of the universe. What about the remaining 95%?
Searching for the Invisible Glue: Dark Matter
Galaxies rotate so fast that the gravity from visible matter alone cannot explain it. This means something with strong gravity, invisible to us, acts like an ‘invisible glue’ holding galaxies together. This is Dark Matter, which makes up about 27% of the universe.
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For a long time, the particle called ‘WIMP’ was the leading candidate but was never found. Recently, Professor Jin Kim from Korea proposed the ‘Axion’ particle as a new hopeful candidate. Korea’s Institute for Basic Science (IBS) is leading world-class axion search research.
The Unknown Force Pushing the Universe Apart: Dark Energy
In 1998, astronomers discovered that contrary to expectations that cosmic expansion would slow due to gravity, it is actually accelerating. This implies the existence of a ‘repulsive’ force filling space, called Dark Energy, which accounts for about 68% of the universe.
Recent early data from the Dark Energy Spectroscopic Instrument (DESI) project suggests this dark energy might not be a constant, raising new questions for the standard cosmological model.
Humanity’s New Eye: The Dawn Revealed by James Webb
In 2021, humanity launched the great gift of the James Webb Space Telescope (JWST) into space. Following Hubble, this telescope observes the universe in infrared, allowing us to peer into the dawn of the cosmos.
‘Baby Galaxies’ Larger Than Expected
JWST discovered ‘baby galaxies’ in the early universe just 500–700 million years after the Big Bang that are much larger, brighter, and heavier than predicted by existing theories. This does not disprove the Big Bang theory but suggests we need to revise our understanding of how stars and galaxies formed and grew after the Big Bang.
Deepening Mystery: The Hubble Tension
JWST also examined the major cosmological puzzle called the Hubble Tension—the discrepancy between two methods of measuring the universe’s expansion rate (Hubble constant). JWST confirmed Hubble’s observations were accurate, proving this is a real problem, not a measurement error. This strongly hints at the existence of new physics unknown to us.
Comparison: Steady-State vs. Big Bang Cosmology
Let’s briefly compare the two theories central to early cosmology debates:
| Aspect | Steady-State Theory | Big Bang Theory |
|---|---|---|
| Universe’s Beginning | No beginning or end; eternal. | Began about 13.8 billion years ago from a hot, dense point. |
| Universe’s Appearance | Overall density unchanged over time. | Expands, cools, and density decreases over time. |
| Key Evidence | Lacks observational support. | Multiple evidences: expansion, CMB, element ratios, etc. |
| Current Status | Considered a fringe theory today. | Established standard model of modern cosmology. |
Conclusion
From Fred Hoyle’s cynicism to a grand journey spanning 13.8 billion years, this story is ultimately about us.
- Key Point 1: The Big Bang theory is the established explanation supported by diverse observational evidence. Cosmic expansion, cosmic microwave background, and light element ratios all point to a massive beginning 13.8 billion years ago.
- Key Point 2: 95% of our universe remains an unknown mystery. Dark matter and dark energy are the greatest challenges for modern physics and hold the keys to the universe’s fate.
- Key Point 3: James Webb is fundamentally changing our understanding of the cosmos. Discoveries of early galaxies and confirmation of the Hubble tension challenge existing theories and herald a new era of ’new physics.’
The great astronomer Carl Sagan said, “We are made of star stuff.” Hydrogen and helium created by the Big Bang formed stars that made carbon, oxygen, and iron, and the dust from those stars came together to form us. The 13.8 billion-year history of the universe is contained within your very body as you read this.
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How about reflecting once more on the meaning of our existence in this vast universe?