According to Heisenberg's uncertainty principle it is impossible to determine accurately momentum and position of an electron simultaneously. Whereas it's not much of a problem in case of a football because of it's negligible wavelength.

Now suppose, suddenly everything in the universe increased by a factor of $7.8\times 10^{13}$. Such that an electron would acquire the dimensions of a football ball.

As everyone and everything in the universe increased, so nobody will find any change and would still find it difficult to measure the position and momentum of an electron simultaneously. Whereas if you ask someone in our universe, he would measure this electron's position and momentum simultaneously with good certainty. As for him that electron is similar to a football.

So what's with the relative size. Is this uncertainty due to low precision of our instruments. I don't find any such thing mentioned in the uncertainty principle.


closed as off-topic by StephenG, WillO, John Rennie, ZeroTheHero, Buzz Jan 13 at 0:11

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  • 3
    $\begingroup$ Wouldn't people have noticed that the speed of light got $7.8\times10^{13}$ times slower? That seems like something hard to miss. $\endgroup$ – eyeballfrog Jan 12 at 8:34
  • $\begingroup$ I did up voted the above comment because it is not true that we won't notice. But the question is somewhat intriguing. I would say that even a macroscopic hydrogen atom in a parallel universe should pose the same problems scientists experienced here on earth as for its stability would require anyway a kind of quantum physics. A big electron would still radiate as orbiting a giant proton. I may say something stupid but such an example could be use to show that uncertainty is inherent and has nothing to do with sizes let alone. Which enforced the fact that operational precision does not count. $\endgroup$ – Alchimista Jan 12 at 9:25
  • $\begingroup$ Or in other words, OP assumes that scaling up a wavefunction make the electron soccer ball alike. But one should rather see it as described by a scaled wavefunction. Something like that. $\endgroup$ – Alchimista Jan 12 at 9:29

so your question is really is there a case where two universes of different have sizes been put together so that an observer in the relative smaller one can measure the momentum and position of the electron and relay that information to the observer in the larger universe - i dont believe there is a way to test that as we do not have two different size universes to experiment with.


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