Planck length and space expansion/contraction

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SUMMARY

The discussion centers on the implications of the Planck length in relation to the expansion and contraction of space. It asserts that while a cubic volume of space can expand with the cosmological scale factor, reversing time to contract this volume raises questions about reaching sizes smaller than the Planck length. The consensus is that this scenario does not present a contradiction, as the Planck length is not an absolute limit but rather a scale at which classical concepts of space and time break down.

PREREQUISITES
  • Understanding of Planck length and its significance in quantum physics
  • Familiarity with cosmological scale factors and their role in space expansion
  • Basic knowledge of time-reversibility in physics
  • Concepts of classical versus quantum mechanics
NEXT STEPS
  • Research the implications of Planck length in quantum gravity theories
  • Explore the concept of scale factors in cosmology and their mathematical representations
  • Study time-reversibility in physical systems and its consequences
  • Investigate the transition from classical to quantum mechanics and its impact on spatial dimensions
USEFUL FOR

Physicists, cosmologists, and students of theoretical physics interested in the foundational aspects of space-time and quantum mechanics.

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Imagine a cubic volume of space, defined today, with edges of the order of the Planck length.

As cosmological time goes forward this volume expands so that the edges of the cube expand with the scale factor. This seems ok.

However, as physics is time-reversible, it should be valid to imagine time going backwards so that the edges contract with the scale factor.

But then they would be smaller than the Planck length. If the Planck length is the smallest length scale then is there a contradiction here?
 
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