If dispersion forces are always there wherever there are electrons, why don't two pieces of copper for instance meld together when put next to each other? Or why don't other substances stick to each other? For instance, I saw on a video that geckos have "sticky feet" due to dispersion forces.

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    $\begingroup$ They do. But the dispersion forces are weak. More importantly, real-life objects are very rough on atomic level. $\endgroup$ May 16 '18 at 13:34
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    $\begingroup$ In principle you can stick objects together by polishing their surfaces to a roughness of about 1 nm. See optical contact bonding. $\endgroup$
    – Paul
    May 16 '18 at 15:59
  • $\begingroup$ In particular liquids of non-polar molecules such as benzene for example but also any liquid. $\endgroup$
    – porphyrin
    May 16 '18 at 16:12