# Planck length and time

**URL:** <https://boards.straightdope.com/t/planck-length-and-time/43143>\
**Category:** Factual Questions\
**Created:** [November 29, 2000, 4:17am UTC](https://boards.straightdope.com/t/planck-length-and-time/43143 "2000-11-29T04:17:53Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![jbird3000](https://avatars.discourse-cdn.com/v4/letter/j/aeb1de/32.png) [@jbird3000](https://boards.straightdope.com/u/jbird3000)\
**Post date:** [November 29, 2000, 4:17am UTC](https://boards.straightdope.com/t/planck-length-and-time/43143/1 "2000-11-29T04:17:53Z")

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OK, so a Planck length is the small measurement possible. A Planck time is the time for something travelling at c to traverse a Planck length. So if we name Planck lengths as A, B, C, etc… and Planck times as 1, 2, 3… this object’s space-time coordinates would be

A1  
B2  
C3  
etc

What about things NOT going c? Are they hanging around the same Planck length for more than one Planck time? Would

A1  
A2  
B3  
B4  
C5  
C6

Be the coordinates of something travelling at c/2?

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**Author:** ![Lumpy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lumpy/32/446_2.png) [@Lumpy](https://boards.straightdope.com/u/Lumpy)\
**Post date:** [November 29, 2000, 4:39am UTC](https://boards.straightdope.com/t/planck-length-and-time/43143/2 "2000-11-29T04:39:13Z")

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While it’s tempting to regard the Planck length as the “pixel size” of space, it doesn’t really work that way. Per Relativity, there is no background grid to spacetime. The Planck length is simply the scale at which, due to quantum mechanical considerations, it cannot be taken for granted that space is continuous. It’s more accurate to say that we cannot postulate anything happening at a smaller scale because our available theories break down.