## The Three Pillars

Back to basics - Quantum Mechanics, Relativity, and Gravity... many physicists, including many graduate students, may not realize this very fundamental aspect of how physics perceives the world. Yet this is so easy and important to understand and is immensely helpful to get a gut feeling of how the natural laws tick. Here it is.

We all have, from birth, a perception of three different measures of the world around us: one for length, one for time, and one for mass. We see 3 realizations of the length measure, i.e. we live in 3D; we have a partial grasp of the concept of time since it seems to thrust us uncontrollably into our miserable futures; and mass has to do with a quantification of the amount of "stuff" in an object.

A priori, these 3 measures have no scales associated with them: 1 meter is equivalent to 1000 meters, etcetera. Philosophically, there is no reason to have a special scale for any of the three. Interestingly however, Nature has provided us with exactly three natural scales to make the world interesting: one is speed of light, the other is Planck's constant for Quantum Mechanics, and the third is Newton's constant for the gravitational force! These three scales add all the flavor to the world around us, and they delineate the three pillars of modern physics: Relativity, Quantum Mechanics, and Gravity. All three frameworks are tested ad nauseum individually in the lab. They also all fit together perfectly, except for Gravity and Quantum Mechanics... these two are inconsistent with each other! and hence arises one of the greatest puzzles of modern physics still desperately awaiting a resolution...

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