I was reading Energy-momentum, and I came across this simplified equation: $$E^2 = (mc^2)^2 + (pc)^2$$

where $m$ is the mass and $p$ is momentum of the object. That said, the equation is pretty fundamental and nothing is wrong when looked upon, I similarly also believed this but I came across an "special" cases where this does not apply:

• If the body's speed $v$ is much less than $c$, then the equation reduces to $E = (mv^2/2) + mc^2$.

This I find really crazy, because first Einstein, always wanted to create a theory\equation that applied to every aspect of physics and has no "fudge" factors, that said irony is present from Einstein. Next, why does this not work in every aspect? surely a equation should be "universal" and should still work with any values given.

Most importantly why does this not work, if velocity is "much" slower than light? What do they mean by "much slower", what is the boundary for "much slower"?

Regards,

I was reading Energy-momentum, and I came across this simplified equation: $$E^2 = (mc^2)^2 + (pc)^2$$

where $m$ is the mass and $p$ is momentum of the object. That said, the equation is pretty fundamental and nothing is wrong when looked upon, I similarly also believed this but I came across a "special" cases where this does not apply:

• If the body's speed $v$ is much less than $c$, then the equation reduces to $E = (mv^2/2) + mc^2$.

I find this really crazy, because first Einstein, always wanted to create a theory\equation that applied to every aspect of physics and has no "fudge" factors, that said irony is present from Einstein. Next, why does this not work in every aspect? surely a equation should be "universal" and should still work with any values given.

Most importantly, why does this not work, if velocity is "much" slower than light? What do they mean by "much slower", what is the boundary for "much slower"?

Regards,

I was reading Energy-momentum, and I came across this simplified equation: $$E = mc^2 + pc$$

where $m$ is the mass and $p$ is momentum of the object. That said, the equation is pretty fundamental and nothing is wrong when looked upon, I similarly also believed this but I came across an "special" cases where this does not apply:

• If the body's speed $v$ is much less than $c$, then the equation reduces to $E = (mv^2/2) + mc^2$.

This I find really crazy, because first Einstein, always wanted to create a theory\equation that applied to every aspect of physics and has no "fudge" factors, that said irony is present from Einstein. Next, why does this not work in every aspect? surely a equation should be "universal" and should still work with any values given.

Most importantly why does this not work, if velocity is "much" slower than light? What do they mean by "much slower", what is the boundary for "much slower"?

Regards,

I was reading Energy-momentum, and I came across this simplified equation: $$E^2 = (mc^2)^2 + (pc)^2$$

where $m$ is the mass and $p$ is momentum of the object. That said, the equation is pretty fundamental and nothing is wrong when looked upon, I similarly also believed this but I came across an "special" cases where this does not apply:

• If the body's speed $v$ is much less than $c$, then the equation reduces to $E = (mv^2/2) + mc^2$.

This I find really crazy, because first Einstein, always wanted to create a theory\equation that applied to every aspect of physics and has no "fudge" factors, that said irony is present from Einstein. Next, why does this not work in every aspect? surely a equation should be "universal" and should still work with any values given.

Most importantly why does this not work, if velocity is "much" slower than light? What do they mean by "much slower", what is the boundary for "much slower"?

Regards,