system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 why there’s an equal chance of rolling a 1, 2, 3, 4, 5, or 6 - despite there being anywhere from 1 -6 dimples on a side? Doesn’t physics/aerodynamics suggest that fewer dimples = greater weight = less likely to land facing up?
gpt
In theory your are correct - between the 1 and 6 face on a spotted die, the 6 face will be slightly lighter due to the fact more material has been removed to form the spots, so the die should have a slight bias to the 6 face (as the heavier 1 face will fall to the bottom).

You could alter the size of the spots and the depth they have been drilled to and even this out to create a fair die, and model the centre of gravity within the die b to ensure it is perfectly central and not thrown off centre by the distribution of the spots or other factors.

In reality, with a normal die there is a margin of error - the tolerances of the production mean that any theoretical imbalance caused by the weight of the spots is completely overshadowed by the variability of the manufacture. The dice are still more than random enough to fulfill their job playing most games however, as a slight bias generally won't be particularly obvious unless you are documenting your rolls. Playing monopoly won't be specific and intensive enough use to ever support much of a difference.
You may however find people who do a lot of dice based games like D&D having lucky sets of dice - often superstitious, but sometimes based on noting a trend in the rolls...

The one place we do demand precision however, is in gambling, so the dice used by casinos are made to a very specific set of tolerances and specifications to ensure they are completely fair - here, when they drill the faces to form the spots, the holes are then refilled with a coloured (white) version of the same material. So any weight removed is then replaced exactly and the weight remains the same and the die fair.
Alongside that they are also made to a thousandth inch precision, sharp edged so damage can be more readily spotted (requiring them to be rolled in a specific way - bounced off the opposite side of a pit to ensure they roll enough), and always translucent so any bubbles, imperfections or human tampering can be spotted 
A level of precision that is pointless (and the sharp edges are actually detrimental rolling on a normal table) when playing snakes and ladders, and mass produced, terrible quality dice will still be random enough, but necessary when you are potentially talking about very large sums of money being gambled.