why does physics work differently depending on scale?

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I was talking to someone the other day who explained to me that the laws of physics as we understand them are not necessarily ‘rules’ that things on a really tiny scale obey, and the calculations we use to talk about physics on a scale that’s relevant to humans are more like estimations of what will *most probably* happen as a result. This also means there’s no such thing as a perfect circle or a perfect sphere I think? Could someone ELI5?

In: Physics

13 Answers

Anonymous 0 Comments

It’s about probabilities at different scales.

If you throw a dice 6 times, it’s likely you won’t get each number once

You may get {6,1,3,3,2,4}.

I’ve got twice as many 3s as 1s here for example.

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However if I throw a dice 6000 times, the chances are that I’ll get each number a roughly even number of times (in terms of percentage differences).

The chances of getting twice as many 3s as 1s would be incredibly small.

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In both these examples, the physics of the dice doesn’t change – it’s just that at larger scales, the laws of probabilities are more apparent.

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This is why individual particles at the quantum scale can be hard to predict but large groups of atoms (such as a bouncing ball) are much easier to predict

Anonymous 0 Comments

5 year olds wont understand the concept of relativity, in the sense of Duality. But, my explanation would be this: that person told you correctly. There is no rule anywhere. Its our choice of words (formulas, theories etc) that we use to explain what we see or experience. If you feel cold at 10celcius and i dont, then what is COLD anyways? Cold is a word which is relative – not real in absolute terms. What is ohms law? Well now we need to establish a common understanding of what we gonna call Ohm so we neet to set a “ruleset” for this concept. V=I.R is just words – its not absolute in any way or shape, its a common Wording we use to be able to communicate. Hence, physics doesnt work differently anywhere, it works however it works, but we call it differently. Weather is never cold, its just weather. Sometimes (at some scales, if you will) we call it Cold, sometimes we call it Hot.

Anonymous 0 Comments

It’s not PHYSICS that works differently. It’s our MODELS that work differently at different scales, which are imperfect, and therefore break down in certain situations.

Basically, our knowledge/mathematics of physics is incomplete, so we need to use a few “cobbled together” models that are the best we have right now.

BTW, saying “cobbled together” massively undersells the amount of genius and work that’s gone into our current models. It’s just that physics is even MORE complicated than that.