Seven scientific mysteries that still defy explanation
For as long as humans have walked the planet, we have tried to answer the questions that nature keeps throwing at us. Fire, gravity, disease, the stars overhead: each was once a puzzle and each, eventually, yielded to patient inquiry. Yet for every solved riddle there always seemed to be another waiting in the wings, and a handful of these stubborn mysteries remain almost exactly where our ancestors first encountered them.
What makes these puzzles fascinating is that they sit at the edge of working science rather than the fringe. Researchers in Canberra, Melbourne, Perth and Sydney investigate them daily, publish in respected journals, and still return home without an answer that satisfies their peers. The mystery is not that nobody is looking. The mystery is that the looking has not yet finished.
They range from the very small to the very large, and from the very old to events happening right now over our heads. Some concern physics, some biology, some the strange borderland where both meet. Together they form a quiet hum of unfinished business running underneath every confident textbook chapter, and they remind us that the map of knowledge still has large blank spaces.
Below is a quick comparison of the seven phenomena covered in this piece, followed by a closer look at each one. Readers who enjoy unresolved puzzles from history will recognise the same stubborn spirit running through them all.
| Mystery | Field | First serious study | Where it appears | Best current theory |
|---|---|---|---|---|
| Dark matter and dark energy | Cosmology | 1930s | Everywhere in the cosmos | Unknown particles plus a cosmological constant |
| Consciousness | Neuroscience and philosophy | 1990s, named the hard problem | Every animal brain | No consensus |
| Fast radio bursts | Astrophysics | 2007 | Distant galaxies | Magnets near neutron stars |
| Origin of life | Chemistry and biology | 1950s | Earth, possibly elsewhere | RNA world and variants |
| Ball lightning | Atmospheric physics | 1638 | Thunderstorms worldwide | None widely accepted |
| Sleep | Biology and neuroscience | Modern study from the 1920s | All animals studied so far | Multiple competing ideas |
| Matter-antimatter imbalance | Particle physics | 1960s | The early universe | CP violation, but not enough |
The dark matter that fills the cosmos
Astronomers have known for almost a century that the visible matter in galaxies does not produce enough gravity to hold them together. Galaxies rotate too fast, galaxy clusters bend light too strongly, and the cosmic microwave background carries fingerprints of something we cannot see. The term for this missing ingredient, dark matter, was coined by the Swiss astronomer Fritz Zwicky in 1933, and the search for what it actually is has only grown more urgent.
Every credible candidate so far has fallen short. MACHOs were ruled out by gravitational lensing surveys. WIMPs, once the favourite, have mostly evaded detectors such as the one buried deep under the Stawell gold mine in regional Victoria, which was purpose built to spot them in the quiet rock far below the heat of an Australian summer. Axions remain a possibility but have not been found. Modified gravity theories can explain some observations but not all.
On top of that there is dark energy, an even larger puzzle. Observations of distant supernovae in the late 1990s revealed that the expansion of the universe is accelerating, and the simplest explanation is a vacuum energy that fills space itself. The numbers, however, do not match quantum theory by a factor of about ten to the sixtieth power, a discrepancy so large that many physicists quietly suspect the real answer is something nobody has yet imagined.
The hard problem of consciousness
Most mysteries in science can in principle be tackled with more data and cleverer instruments. Consciousness appears to be different. A person can know every neuron that fires in a brain and still not explain why there is a subjective experience of seeing red, tasting Vegemite on warm toast, or feeling the salt breeze at Bondi Beach at sunrise. The philosopher David Chalmers named this gap the hard problem in the mid 1990s, and it has refused to close.
Australian researchers have weighed in from several angles. Groups at the University of Sydney and the Australian National University have mapped the activity of fruit flies and mice during complex tasks, building some of the most detailed connectomes in existence. Their work shows how signals move through brains with extraordinary precision, yet each new map makes the subjective side of experience seem stranger, not more familiar.
Theories abound. Integrated information theory treats consciousness as a property of any system with enough internal complexity. Global workspace theory treats it as a kind of internal broadcast. Predictive processing suggests the brain is a prediction machine, and awareness is what error correction feels like from the inside. Each has supporters and each has critics, but none has reached the status of a working theory in the way general relativity describes gravity.
Fast radio bursts that light up the sky
In 2007, archival data from the CSIRO Parkes telescope in New South Wales revealed an intense burst of radio waves lasting only a few milliseconds. The signal had travelled across billions of light years, which meant its source had released in an instant as much energy as the Sun produces in a century. Since then thousands more fast radio bursts have been detected, many of them by instruments built or upgraded right here in Australia.
The Australian Square Kilometre Array Pathfinder in the Western Australian outback, the upgraded Parkes receiver, and a new detector at Molonglo near Canberra have together turned Australia into the world's leading site for these fleeting signals. Even so, no one knows what produces most of them. Some repeating bursts have been traced to magnetars, highly magnetised neutron stars, but the majority are one-off events whose origin remains unconfirmed.
Each new detection sharpens the mystery rather than resolving it. Bursts arrive from every direction, at every time of day, and at frequencies that suggest they have passed through surprisingly empty space. As Australia builds its share of the international Square Kilometre Array, the country looks likely to play a central role in finally catching one of these events in the act.
How life first appeared on Earth
Roughly four billion years ago, a planet of molten rock and toxic air became a planet of stromatolites and shallow seas. Somewhere in between, chemistry became biology. The window in which this happened was tiny in geological terms, and the odds against it seem long enough that even conservative researchers call the origin of life the deepest puzzle in science.
Theories lean on molecules that can both store information and catalyse reactions. RNA world models propose an early stage in which RNA did both jobs now shared between DNA and proteins. Lipid world models propose that bubble-like compartments came first. Iron-sulphur world models place the action in hydrothermal vents on the early ocean floor. Each idea has laboratory support, and Australian groups at the University of New South Wales and Monash University have produced some of the most cited work in the field.
The trouble is that every theory only explains a piece of the puzzle. No single pathway has yet produced a living cell from simple chemicals, and the conditions on the early Earth remain uncertain enough to allow many possibilities. Until that changes, the question of how lifeless chemistry turned into living biology will stay open.
Ball lightning in the wild
Reports of glowing spheres floating through thunderstorms date back to at least 1638, when the wide-ranging scholar Robert Dale described glowing balls in a rural English church. Pilots, storm chasers and puzzled farmers have added thousands of accounts since. The reports are too consistent to dismiss and too rare to study at will.
Mainstream explanations tend to fall into two camps. One treats ball lightning as an optical effect created by the way lightning strikes vaporise soil and minerals. The other treats it as a real plasma phenomenon involving charged air, perhaps supported by a thin shell of silicon combustion. Both have experimental backing in narrow conditions and neither captures the full range of reported behaviour.
What makes ball lightning awkward for science is that it appears to pass through glass, leave sulphur smells, and sometimes persist for tens of seconds before fading. Those properties, if real, hint at physics we do not yet understand. Researchers at CSIRO have collected eyewitness reports across the country, and a few laboratories in Adelaide and Brisbane have even produced small examples in the lab, but the field still feels closer to folklore than to settled physics.
Why every animal sleeps
Almost every animal studied so far sleeps, from tiny fruit flies to huge whales, and yet the function of sleep is still argued over. A person can survive longer without food than without sleep, and a rat deprived of sleep dies within a couple of weeks. Sleep cannot simply be rest, since the brain is often more active during certain sleep stages than during quiet waking hours.
Modern research, including studies led from the University of Melbourne and the Woolcock Institute in Sydney, has mapped what happens at the cellular level. Memories appear to be consolidated, metabolic waste seems to be flushed from the brain through the glymphatic system, and the immune system is recalibrated. Each of these jobs is real and important, but together they still do not explain why such a vulnerable state evolved in the first place.
Other animals offer clues. Some birds sleep with one half of the brain awake, which suggests sleep can be sliced. Octopuses appear to dream in colour. And yet even after a century of careful work, no single theory has pulled all the pieces together into something that feels complete.
Why matter won the early universe
When the big bang produced equal amounts of matter and antimatter, the two should have annihilated almost completely and left a universe filled only with radiation. That is not the universe we live in. Somehow, for every billion antimatter particles there were a billion and one matter particles, and the tiny leftover built every star, planet and person that has ever existed.
Particle physics has a candidate explanation. The 1960s showed that certain reactions do not treat matter and antimatter identically, a property called CP violation. Experiments at CERN and in Japan have measured the effect, and Australian physicists at the University of Adelaide have contributed to related work on the Belle experiment. The numbers, however, do not quite add up. Standard CP violation falls short of the cosmic imbalance by many orders of magnitude.
Closing that gap may require new particles, new forces, or a rethink of how the early universe cooled. Until then, the simple fact that anything exists at all will keep feeling stranger than any of the textbook explanations on offer.
Ways to keep following the science
If a subject like this sparks your curiosity, here are a few gentle ways to follow it further without needing a laboratory of your own:
- Follow the monthly research notes from the ARC Centre of Excellence for All-Sky Astrophysics, much of it run from Sydney and Perth.
- Listen to ABC Radio National's science programs during your commute, particularly the regular interviews with Australian researchers.
- Visit a public open day at CSIRO's sites, including the telescopes at Parkes and Narrabri, where staff explain current work in plain language.
- Read the Australian Institute of Physics magazine for accessible summaries of new findings.
- Watch for updates from the Square Kilometre Array as construction progresses across Western Australia and South Africa.
- Browse university museums in Melbourne, Sydney and Brisbane, which often hold free evening lectures on unsolved problems.
The questions above have waited longer than most modern scientific theories, and a few may still be waiting long after the next generation of researchers has retired. That is the strange and humbling part of being human. We get to ask the questions, but the universe decides when, if ever, to answer. Bring your curiosity back to this page whenever a new headline makes you wonder what is really going on out there, and share these mysteries with a friend who still believes science has explained everything.