Time and matter, is there a smallest unit?

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Discussion Overview

The discussion revolves around the concept of whether there exists a smallest unit for time and matter, exploring the implications of dividing these quantities indefinitely. Participants engage with both theoretical and conceptual aspects of this question, referencing established scientific ideas and personal reflections.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • Some participants suggest that electrons are considered "point particles," implying they cannot be divided further, while quarks are mentioned as the smallest known constituents of matter.
  • Others propose that time is not quantized, although there are theories suggesting it might be.
  • Planck length and Planck time are introduced as potential smallest units, with specific values provided, but the implications of these units are debated.
  • A participant challenges the validity of a claim regarding photons collapsing into black holes when measuring at Planck scales, asserting that current theories do not support the existence of a smallest unit based on current measurements.
  • Another participant notes that while practical limitations exist in measuring lengths smaller than Planck length, this does not necessarily imply that such lengths do not exist.
  • Concerns are raised about the conceptual understanding of Planck units, questioning whether they represent a fundamental limit or merely a measurement constraint.
  • Some participants express skepticism about the consensus that Planck length and time are the minimum possible units, suggesting that this belief may stem from misconceptions.

Areas of Agreement / Disagreement

Participants express a range of views, with no clear consensus on whether Planck length and time represent the smallest units of measurement or if smaller units could exist conceptually. The discussion remains unresolved, with competing perspectives on the nature of time and matter at fundamental scales.

Contextual Notes

Participants highlight limitations in current measurement technologies and the conceptual challenges in defining the smallest units of time and matter. There is also an acknowledgment that existing theories may not adequately address phenomena at Planck scales.

mrhoneycinnamo
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dear friends, I have always wonder: is there a smallest unit for time and matter? or in other words, can we continuesly divide time and matter into smaller pieces non-stop?
ive had this question since young when I imagined myself cutting a piece of cheese. I just can't help stop cutting it and it kinda troubled me.
Anyone please help me?
 
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mrhoneycinnamo said:
dear friends, I have always wonder: is there a smallest unit for time and matter? or in other words, can we continuesly divide time and matter into smaller pieces non-stop?
ive had this question since young when I imagined myself cutting a piece of cheese. I just can't help stop cutting it and it kinda troubled me.
Anyone please help me?

Electrons are considered "point particles" and you can't get any smaller than that. Otherwise, quarks are the smallest we know of.

Time is not considered to be quantized although there ARE theories that it is/might be.

This topic is beaten to death here regularly so I suggest a forum search.

HINT: every thread has a list at the bottom of the page of similar threads. That's a good place to start.
 
Yes. They're called Planck length and Planck time. The Planck length is 1.61619926 × 10-35 meters, Planck time is the time it takes light to cross a Planck length.

From wiki:

"Simple dimensional analysis shows that the measurement of the position of physical objects with precision to the Planck length is problematic. Consider the following thought experiment. Suppose we want to determine the position of an object using electromagnetic radiation, i.e., photons. The greater the energy of photons, the shorter their wavelength and the more accurate the measurement. If the photon has enough energy to measure objects the size of the Planck length, it would collapse into a black hole and the measurement would be impossible. Thus, the Planck length sets the fundamental limits on the accuracy of length measurement."
 
Unfortunately, the dimensional analysis of the wiki is wrong. A photon cannot collapse into a black hole regardless of its energy/wavelength.

At this point, I would say that we don't know. We have no reason to believe, based on current measurements, that there is a smallest unit. But our current theories are not expected to work on Planck scales and our current measurements are nowhere close to that level.
 
Last edited:
'Smaller and smaller = more and more difficult' doesn't necessarily imply an actual limit.
 
puncheex said:
Yes. They're called Planck length and Planck time. The Planck length is 1.61619926 × 10-35 meters, Planck time is the time it takes light to cross a Planck length.

No, the universe is not limited to them as any sort of "smallest unit". It does seem to be true that there would not be a way to measure smaller amounts, but that doesn't mean that there aren't smaller amounts.Because we don't have any specific names for smaller units, I can't say "consider the blumpf" but I CAN say "just think about a length of 10E-40 meters" or consider a length of 1/100th of a Plank length". There is nothing yet known that constrains the existence of such lengths in reality.

In practical terms it's reasonable to think of them as the smallest possible units since you can't measure anything smaller, but if you want to move away from the theoretical to the practical, then it seems more reasonable to say that in practice we will likely never be able to measure things anywhere near as small as they are so they are smaller than the minimum units. Using current technology we can't measure anything down below about 20 orders of magnitude larger than one Plank length, but of course that's likely to get better with new technology, but 20 orders of magnitude seems unlikely. The 20 by the way is just my recollection and might be off but some, but not many, orders of magnitude.
 
Many people and scientists say the Planck length is the minimum length possible. the same they say about the Planck time. but so far I have not read the reason for this answer. It is not a matter of measurement, is conceptual. if they say that the Planck length is or has been the minimum, does that mean the universe was that size in the BB? I do not think so
 
Ramon G.Wilmot said:
Many people and scientists say the Planck length is the minimum length possible. the same they say about the Planck time.

That's a common misconception - we even have an Insights article: https://www.physicsforums.com/insights/hand-wavy-discussion-planck-length/

As this is an old thread and we're working from a misconception, I think we can close the discussion here.
 

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