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From: David Brown <david.brown@hesbynett.no>
Newsgroups: comp.lang.c
Subject: Re: "A diagram of C23 basic types"
Date: Tue, 15 Apr 2025 19:22:47 +0200
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On 15/04/2025 07:40, BGB wrote:
> On 4/14/2025 11:15 PM, Lawrence D'Oliveiro wrote:
>> On Mon, 14 Apr 2025 19:43:04 -0500, BGB wrote:
>>
>>> On 4/14/2025 5:33 PM, Lawrence D'Oliveiro wrote:
>>>>
>>>> I figured that it would be hard to find an epoch less arbitrary than
>>>> the Big Bang ...
>>>
>>> But, we don't really need it.
>>>
>>> If so, could probably extend to 128 bits, maybe go to nanoseconds or
>>> picoseconds.
>>
>> The reason why I chose the Planck interval as the time unit is that
>> quantum physics says that’s the smallest possible time interval that 
>> makes
>> any physical sense. So there shouldn’t be any need to measure time more
>> accurately than that.

Quantum mechanics, the current theory, is not complete.  Physicists are 
aware of many limitations.  So while Plank time is the smallest 
meaningful time interval as far as we currently know, and we know of no 
reason to suspect that smaller times would be meaningful, it would be 
presumptuous to assume that we will never know of smaller time intervals.

> 
> Practically, picoseconds are likely the smallest unit of time that 
> people could practically measure or hope to make much use of.

The fastest laser pulses so far are timed at 12 attosecond accuracies - 
100,000 as accurate as a picosecond.  Some subatomic particle lifetimes 
are measured in rontoseconds - 10 ^ -27 seconds.  Picoseconds are 
certainly fast enough for most people, but certainly not remotely fast 
enough for high-speed or high-energy physics.

> 
> While femtoseconds exist, given in that unit of time light can only 
> travel a very short distance, and likely no practical clock could be 
> built (for similar reasons), not worth bothering with (*).
> 
Physicists have measured times a thousand millionth of a femtosecond. 
It is not easy, of course, but not impossible.