Given the Universe is expanding. Therefore everything within the U is expanding, in all dimensions, subatomic to cosmic. Then all metre sticks are expanding. The question: How can we measure U expansion with metre sticks that are also expanding? Alice only knew she had grown ten feet tall by comparing herself to her surroundings.


Space is expanding. However, nearby atoms (e.g. those in a metre stick) are not moving away from each other because the inter-atomic forces restore them to their original positions.

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Similarly, as the space between the earth and the sun increases (at an insignificant rate), the gravitational force restores the earth and sun back to their equilibrium distance.

  • $\begingroup$ Great visual explanation for this common (and reasonable) question. $\endgroup$ – BMS Sep 5 '14 at 23:44
  • $\begingroup$ This is true, but only for a constant rate of expansion. In an increasingly accelerating universe the newly created space does have a non-trivial effect, hence the possibility for a "big rip" event. $\endgroup$ – CuriousOne Sep 6 '14 at 0:42
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    $\begingroup$ Also we should note that the current expansion rate is about $2\times 10^{-18}/\mathrm{second}$. This tiny expansion is completely swamped by thermal vibrations that are many orders of magnitude greater. $\endgroup$ – Mark Adler Sep 6 '14 at 4:21

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