Eli5: Why 10-43 (1 planck time) after the big bang? How did they calculate that number as the point of reference as to what we can know?
In: Physics
Copy pasted because I’m not smart enough to remember everything accurately.
Wikipedia:
There is no currently available physical theory to describe such short times, and it is not clear in what sense the concept of time is meaningful for values smaller than the Planck time. It is generally assumed that quantum effects of gravity dominate physical interactions at this time scale.
Forbes:
In order to measure anything at the Planck scale, you’d need a particle with sufficiently high energy to probe it. … If you had a particle that actually achieved that energy, its momentum would be so large that the energy-momentum uncertainty would render that particle indistinguishable from a black hole.
TL;DR:
Our current theories and techniques, and possibly physics, don’t let us clearly define anything below the Planck Scale
We know that some important thories, quantum theory and general relativity, are incompatible – they can’t both be perfectly true without leading to contradictions.
The planck units are units that define several fundamental physical constants, specifically the speed of light, the gravitational constant, the reduced Planck constant and the Boltzmann constant as 1 and derive all other units from that.
It just so happens that some planck units such as time or length are rough indicators for where we know quantum theory and general relativity to conflict with each other, meaning we know that our theories are inaccurate at those scales.
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