Is time instant? It's a question about how time passes. Time cannot pass in a single step, as that would be instant. So, how does then time pass?

It depends a bit on how you define time. It is, however, a concept that is frustratingly resistant to simple definition.

Many of the words you use are ambiguous and vague. They’re not helpful in understanding. Precision matters in topics like this.

Instant is meaningless. You cannot stop time. Time is change. Entropy increasing.

Perhaps you mean what our feeble limited human minds perceive as time. As right now. As this moment or this instant, but even that is delayed by several hundred milliseconds from when the event occurs. There is a measurable space between interactions and our awareness of them.

There are perhaps other dimensions to consider, too. We are aware of 3-dimensions and exist in 4, but perhaps there’s more. That likely informs the answer here.

Without input of energy, disorder increases. Time is a way we use imperfect human terms to describe that growing entropy. It’s a measure like distance and you’re essentially asking “how does distance pass?”

This conversation will forever remain a philosophical one, and it requires you ask better questions with clearer terms. This is part of why math is so appealing on this topic. Clarity is embedded and misinterpretation mitigated.

Edited December 7Dec 7 by iNow

We measure time in discrete steps, but it's actually continuous i.e undivided/smoothly progressive.

Edited December 7Dec 7 by StringJunky

41 minutes ago, StringJunky said:

We measure time in discrete steps, but it's actually continuous i.e undivided/smoothly progressive.

Is there a limit to how small an interval that can be measured?- and is that for practical reasons or intrinsic reasons (ie there are no intervals below a certain size that could be measured even if we had the capability-which obviously we could not have since the spacetime interval is built into our measuring tools as far as I know)

Or could we in theory build measuring tools (to measure time intervals) with unlimited capabilities so that the spacetime intervals themselves could be limitless small?

25 minutes ago, geordief said:

Is there a limit to how small an interval that can be measured?- and is that for practical reasons or intrinsic reasons (ie there are no intervals below a certain size that could be measured even if we had the capability-which obviously we could not have since the spacetime interval is built into our measuring tools as far as I know)

Or could we in theory build measuring tools (to measure time intervals) with unlimited capabilities so that the spacetime intervals themselves could be limitless small?

It’s practical considerations, but the Heisenberg uncertainty principle would be a limit even if experimental precision were improved.

34 minutes ago, swansont said:

It’s practical considerations, but the Heisenberg uncertainty principle would be a limit even if experimental precision were improved.

Cheers. What sort of duration range might that come into effect? Is it hypothesized? Would Planck time be a limit?

A similar question would be, "is space point-like?"

We prefer to say, "is time a continuum, or is it discrete (ie, made up of little 'jolts' of time)"?

@geordief , IMO, asked the right question.

It is perhaps telling that the HUP doesn't allow us to "see" this point-like structure of time, provided it makes any sense.

1 hour ago, StringJunky said:

Cheers. What sort of duration range might that come into effect? Is it hypothesized? Would Planck time be a limit?

We’re currently in the range where quantum limits come into play, but there are tricks to try and improve precision.

One limit from the HUP is the fact that the lifetime of atomic (or nuclear) states correlates with the transition width, i.e. the energy level has a fuzziness to it. Narrower levels have longer lifetimes, so it’s harder to cause the transition, which affects signal/noise.

A lot of the practical effects on the fountain clocks were at the part in 10^17 level, which was O.K. because the measurement itself started at a few parts in 10^-13, and it took around a year to get down to 10^-16. (white noise reduces with the square root of the number of measurements) Optical clocks start at a better short-term precision, and have to work hard to get their error contributions small enough to get their part in 10^18 (or better) results.

As far as quantum limits go, there are tricks using “squeezed” states - you let one error that you don’t care about be big, so you can make (“squeeze”) the conjugate variable’s error smaller

JILA and NIST have been exploiting entanglement

https://jila-pfc.colorado.edu/news-events/articles/entangled-time-pushing-atomic-clocks-beyond-standard-quantum-limit

“Each atom behaves independently, and their random quantum behavior adds noise to the measurement. This randomness is what defines the Standard Quantum Limit. It’s like trying to hear a single beat in a noisy crowd.

To reduce this noise, scientists often increase the number of atoms. The more atoms you measure, the better your estimate—kind of like averaging more coin flips to get closer to 50/50. But packing too many atoms together causes them to interact in ways that shift the clock frequency, introducing new errors. So instead of adding more atoms, the JILA team tried something different: they made the atoms entangled.

Entanglement is a quantum connection between particles. When atoms are entangled, their random quantum behavior becomes linked—even if they’re not touching. In this experiment, the researchers used entanglement to make the atoms behave more like a team, reducing the noise in their collective signal.

This approach allows the clock to beat the SQL, achieving better precision without needing more atoms”

1 hour ago, swansont said:

Entanglement is a quantum connection between particles. When atoms are entangled, their random quantum behavior becomes linked—even if they’re not touching. In this experiment, the researchers used entanglement to make the atoms behave more like a team, reducing the noise in their collective signal.

Cool stuff! Clever solution.

Edited December 7Dec 7 by StringJunky