# Rest Mass The [Principle of Relativity](Principle%20of%20Relativity.md) tells us that there is no meaning in saying "an object is stationary". Therefore it would not make sense to say that rest mass is the intransigence of a stationary object. Instead, rest mass is the intransigence of an object *as measured by something who is stationary relative to the object*. The say that rest mass isn't relative is to say that every one of us agrees on how it should be measured and by whom, so there will never be any dispute about whether one measurement is better than another. The easiest way to find an object's rest mass, we all agree, is to ask a [Privileged Observer](Privileged%20Observer.md) to measure it. [https://chatgpt.com/share/1490e4ce-1430-417f-880a-70df7a68ec5e](https://chatgpt.com/share/1490e4ce-1430-417f-880a-70df7a68ec5e) --- Date: 20240629 Links to: Tags: References: * [Waves in an Impossible Sea](Waves%20in%20an%20Impossible%20Sea.md) pg 67-68