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Look at the time on your phone right now. You trusted it this morning. You will trust it again tonight. Of all the things people worry about, the clock is almost never one of them.
So here is a question that sounds silly until you try to answer it properly: can a clock be perfectly accurate? Not accurate enough. Not accurate to a billionth of a second. Perfectly. Exactly. Forever.
A small group of physicists in Italy sat down and worked out an answer. Their paper ran in the journal Physical Review Research, and the answer is no — with a catch that almost every write-up left out.
Can a Clock Be Perfectly Accurate? The Short Answer
No. But the reason is far stranger than a manufacturing flaw.
Every clock you have ever owned is imperfect for ordinary reasons. The battery weakens. The room warms up and the metal expands. The quartz crystal inside one wristwatch is very slightly different from the one in the watch sitting next to it on the shelf.
Those are engineering problems, and engineers keep solving them. Clocks have been getting better for centuries with no wall in sight.
What these researchers asked is a different kind of question. They wanted to know whether there is a wall — a floor underneath all the engineering, built into time itself, that no clock could ever get beneath no matter how good it became.
Their calculation says there is. Then it says something most people would not expect: that floor is so far below us that it makes no difference to anything you will ever do.
What the Physicists Actually Calculated
To follow this you need one piece of background, and it happens to be the oldest unfinished argument in physics.
A particle on its own can sit in several states at once. Here and there. Left and right. The moment anyone measures it, it settles into one. Standard quantum theory describes this with stunning accuracy but never explains what a “measurement” actually is, or why the settling happens at all.
Some physicists find that unacceptable. So they built alternatives, called collapse models, which say the settling is a real physical process running all the time, everywhere, on its own — no observer required. This paper works with the two best known versions: the Diósi–Penrose model, which ties collapse to gravity, and Continuous Spontaneous Localization.
Here is where it turns interesting.
If matter really is collapsing continuously, then the mass in any region is very slightly jittering. Mass produces gravity. Gravity bends time — and that last part is not speculation, it is ordinary tested physics, the reason a clock at sea level ticks at a fractionally different rate from one on a mountain.
So a permanent jitter in mass means a permanent jitter in gravity, which means a permanent, unavoidable wobble in the rate at which time passes. Not a wobble anyone causes. A wobble that is simply there.
The team — Nicola Bortolotti, Catalina Curceanu, Lajos Diósi, Simone Manti and Kristian Piscicchia — put numbers to that wobble and turned it into the ultimate limit on how precise a clock could ever be. Their preprint is public for anyone who wants the mathematics.
How Small Is the Wobble?
This is the part the headlines raced past, and it is the whole story.
The effect is not small the way a grain of rice is small next to a loaf of bread. It is small in the way that the researchers themselves say it has no practical consequence whatsoever.
“The uncertainty is many orders of magnitude below anything we can currently measure, so it has no practical consequences for everyday timekeeping,” Curceanu said when the work was described publicly. Piscicchia put it more bluntly still: modern timekeeping technology is entirely unaffected.
That includes atomic clocks — the ones keeping satellite navigation working, synchronising power grids and financial systems and the timestamps on your messages. Not “affected slightly.” Unaffected.
Bortolotti called the result “surprisingly reassuring,” which is not a phrase physicists reach for often.
So the honest version of this story is not that time is broken. It is this: if one particular family of theories turns out to be correct, time has a floor, the floor is real, and it sits so far beneath us that no instrument we have or can currently foresee will ever touch it.
The Part Almost Nobody Repeats
Notice that word. If.
Collapse models are not settled physics. They are rivals to standard quantum theory — serious, respected, and unproven. Nothing in this paper claims the world actually works that way. It says: suppose it does, and here is what would follow.
Then there is the detail that makes this genuinely unusual, and you will not find it in most coverage.
Lajos Diósi is one of the paper’s authors. He is also half the name of the Diósi–Penrose model — the very theory whose consequences are being calculated. He is doing arithmetic on his own idea.
It goes further than that. In 2021, a team including Diósi, Curceanu and Piscicchia published an experiment in Nature Physics that they ran deep beneath a mountain in central Italy, where the rock screens out the background radiation that would otherwise swamp a measurement this delicate. They were hunting for the faint radiation the Diósi–Penrose model predicts that collapsing matter should give off.
They did not find it. The result ruled out the natural, parameter-free version of the model — the simplest and most elegant form of the same theory some of them had spent careers developing.
Underground laboratories are full of results like this, where the most valuable thing an instrument does is fail to see something; the same discipline shows up in the rare occasions when a detector does catch an event it cannot explain.
So the people now working out what this model implies about time are among the same people who previously narrowed it down by failing to find what it predicted. That is not a weakness in the work. That is the work. A theory nobody can shoot at is not a theory. It is an opinion.
Why This Is Not a Frightening Story
There is something quietly humbling in all of this, and it is not the physics.
We are inside time. We cannot step out of it, set it down on a bench, and check it against something more reliable. Every instrument we would use to measure time is itself running on time. The best minds we have can calculate roughly where the floor lies and still cannot stand underneath it to look.
That is a strange position to occupy. It is also not a new one. Long before anyone could measure a billionth of a second, old writing described people as creatures with something eternal placed inside them — a real sense of the whole sweep of things — while remaining unable to see the work being done from beginning to end. A built-in reach, paired with a built-in limit.
It reads like poetry right up until a team of physicists arrives at the mathematics of the same shape: we belong to time, we can describe it in extraordinary detail, and we do not own it.
Which is worth sitting with for a moment, because the numbers involved get very large very quickly. If you have ever tried to hold the actual age of things in your head, you already know the feeling — our free How Old Is the Universe explorer lays those timescales out side by side, and it does not take long before the mind simply stops being able to picture them.
What Happens Next
Clocks keep improving. The engineering wall nobody has hit yet is still nowhere in sight, and this floor is not going to be the thing that stops anyone.
But there is a real prize buried in this paper. Most interpretations of quantum mechanics are untestable — they predict exactly the same experimental results as one another, so choosing between them comes down to taste. Collapse models are different. They make concrete predictions that can actually be checked, which is precisely why that underground experiment was able to narrow them down.
A limit on clock precision is one more place to go looking. Not this year. Probably not this generation. But it is a door rather than a wall.
The Clock on Your Phone Is Fine
So the next time you glance at your phone and it tells you that you are late, you can be confident the problem is not the fabric of time. Our sense of time is far shakier than time itself — which is a different puzzle altogether, and the reason time seems to go by so fast has very little to do with clocks.
It is also true that somewhere far below the reach of any instrument ever built, time may be trembling very gently. It has been doing that the entire time you have been reading this, and it changed nothing.
Some limits are worth knowing about precisely because they are not ours to solve. The clock is fine. The morning still comes. And the smallest crack in time turns out to be the very least of what anyone has to carry today.
What Do You Think?
Here is the one we keep going back and forth on: if a limit is completely real but so small it will never once touch your life, does knowing about it change anything? Some people say a fact you can do nothing with is still worth having. Others say it is just noise dressed up as news. Tell us where you land in the comments — we read them.
Share This
- Physicists worked out whether a clock could ever be perfectly accurate. The answer is no — but the flaw is so small it changes absolutely nothing. Best kind of science story. https://bgodinspired.com/index.php/bible-resources/bible-and-science/can-a-clock-be-perfectly-accurate/
- My favourite detail in this: one of the authors is the man the theory is named after, and his own earlier experiment already ruled out the simplest version of it. That is what doing science honestly looks like. https://bgodinspired.com/index.php/bible-resources/bible-and-science/can-a-clock-be-perfectly-accurate/
- “We belong to time, we can describe it in extraordinary detail, and we do not own it.” Rare for a physics story to leave me thinking about something else entirely. https://bgodinspired.com/index.php/bible-resources/bible-and-science/can-a-clock-be-perfectly-accurate/
Questions People Ask
Can a clock ever be perfectly accurate?
No. Beyond the ordinary engineering problems of temperature, battery drift and material differences, a study published in Physical Review Research argues that if quantum collapse models are correct, time itself carries a tiny built-in uncertainty that sets a floor on how precise any clock could ever be. The researchers stress that the effect is many orders of magnitude smaller than anything current instruments can detect, so no clock in use today, including atomic clocks, is affected in practice.
What are quantum collapse models?
Quantum collapse models are alternatives to standard quantum theory. Standard theory says a particle existing in several states at once settles into a single state when measured, but never explains what counts as a measurement. Collapse models propose that this settling is a real physical process happening continuously and everywhere, with no observer required. The two best known versions are the Diósi–Penrose model, which links collapse to gravity, and Continuous Spontaneous Localization. They are serious and respected, but they are unproven and they are not the mainstream consensus.
Does this research mean atomic clocks are unreliable?
No. The physicists behind the calculation state directly that modern timekeeping technology is entirely unaffected. The predicted uncertainty in the flow of time sits many orders of magnitude below what any current or foreseeable instrument can measure, so satellite navigation, power grids, financial systems and ordinary wristwatches are all completely unchanged by it. One of the researchers described the finding as reassuring rather than alarming.
Who carried out the research on limits to clock precision?
The paper, titled “Fundamental limits on clock precision from spacetime uncertainty in quantum collapse models,” was written by Nicola Bortolotti, Catalina Curceanu, Lajos Diósi, Simone Manti and Kristian Piscicchia, and published in the journal Physical Review Research. Bortolotti is based at the Enrico Fermi Research Centre in Rome. Lajos Diósi is also the co-originator of the Diósi–Penrose collapse model that the paper analyses.
Has the Diósi–Penrose model ever been tested experimentally?
Yes. In 2021 a team including Diósi, Curceanu and Piscicchia published an experiment in Nature Physics that was carried out deep beneath a mountain in central Italy, where rock screens out background radiation. They searched for the faint radiation the model predicts collapsing matter should emit, did not detect it, and ruled out the natural parameter-free version of the model. The fact that collapse models can be tested at all is what sets them apart from most interpretations of quantum mechanics.
