I Does the Uncertainty Principle imply a linear cosmology?

AI Thread Summary
The discussion centers on the application of the Uncertainty Principle to cosmology, specifically regarding the age of the Universe and its energy fluctuations. It argues that if the age of the Universe has an uncertainty, then energy fluctuations could theoretically lead to photon creation, suggesting a linear cosmology model. However, several participants challenge this interpretation, stating that the Uncertainty Principle cannot be applied to the Universe as a whole due to the lack of external measurements. They also clarify that there is no established "energy-time" uncertainty principle applicable in this context. Overall, the conversation highlights significant misconceptions in the initial argument regarding the fundamental principles of quantum mechanics and cosmology.
jcap
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If the uncertainty in the age of the Universe is ##\Delta t## then the Uncertainty Principle implies that it has an uncertainty in its energy ##\Delta E## given by
$$\Delta E \ \Delta t \sim h.\tag{1}$$
If this energy fluctuation excites the zero-point electromagnetic field of the vacuum then a photon is created with energy ##\Delta E## and wavelength ##\lambda## given by
$$\Delta E \sim h \frac{c}{\lambda}.\tag{2}$$
Combining Equations ##(1)## and ##(2)## we find that
$$\lambda \sim c\ \Delta t.\tag{3}$$
Now as this characteristic length ##\lambda## is the wavelength of a photon it is a proper length that expands with the Universal scale factor ##a(t)## so that
$$\lambda \sim a(t).\tag{4}$$
Combining Equations ##(3)## and ##(4)##, and taking ##\Delta t \sim t##, we arrive at a unique linear cosmology with the normalized scale factor ##a## given by
$$a(t) = \frac{t}{t_0}.$$
where ##t_0## is the current age of the Universe.
 
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I'll leave it to more knowledgeable folks to weight in, but what I think is that you have extrapolated the HUP to WAY outside of it's domain of relevance.
 
jcap said:
If the uncertainty in the age of the Universe is ##\Delta t## then the Uncertainty Principle implies that it has an uncertainty in its energy

You can't apply the uncertainty principle to the universe as a whole since there is no way to make an external measurement on it, and the uncertainty principle applies to external measurements.

Also, there is no "energy-time" uncertainty principle as you are using it. See, for example, here:

http://math.ucr.edu/home/baez/uncertainty.html

So your post is based on at least two incorrect premises.
 
jcap said:
If this energy fluctuation excites the zero-point electromagnetic field of the vacuum

Correction, three incorrect premises. The universe as a whole doesn't have "energy fluctuations" in this sense.
 
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https://en.wikipedia.org/wiki/Recombination_(cosmology) Was a matter density right after the decoupling low enough to consider the vacuum as the actual vacuum, and not the medium through which the light propagates with the speed lower than ##({\epsilon_0\mu_0})^{-1/2}##? I'm asking this in context of the calculation of the observable universe radius, where the time integral of the inverse of the scale factor is multiplied by the constant speed of light ##c##.
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