Tried watching a few videos and reading articles, dumbed down even for me, still can’t get my head around it.
Let’s assume it is a 1 kg lead weight in the vacuum of space floating at 1mph.
if its floating through space then apart from kinetic energy which sent it there, and the gravitational energy which made it, what energy is there in that object which makes it applicable to the equation. “A small amount of mass is equal to a large amount of energy” but how?
Also, why is it the speed of light squared? Surely it’d just be the speed of light. If squared that’d be a massive speed so why is it used here?
Finally how come it’s so important? Why is it still important today? Don’t want to sound reductionist but this really makes no sense to me to why it’s so famous.
There are plenty of explanations, none of which make this equation make sense. So assume I am actually 5 years old and somehow figured out how to make a reddit post, how would you explain it?
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>Also, why is it the speed of light squared? Surely it’d just be the speed of light. If squared that’d be a massive speed so why is it used here?
There are a number of approaches to this question, but I’ll try a less common one that really helped me grasp it when I was younger:
You’ll need a concept called “Unit Analysis” (or dimensional analysis) – essentially, in order to add, subtract, or compare two things they have to be in the same units. You can’t compare a length (meters) and a mass (kg) – it just doesn’t work.
Mass is measured in kg (kilograms). Speed is measured in m/s (meters/second).
You presumably know that the formula for kinetic energy is E^k =1/2MV^2. In order for that equation to be true (and it is true) Energy must be measured in kg(m/s)^2.
Given that we can look at the units in E=MC^2 – E is in kg(m/s)^2, M is in kg, and C is in m/s.
If we weren’t squaring the speed on light, we would end up with units of kgm/s – which isn’t energy, it’s momentum.
Thus E=MC is impossible; only E=MC^2 works.
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