E=mc² is Incomplete

You've heard of E=mc²... but you probably haven't heard the whole story.

And twitter - @minutephysics

Minute Physics provides an energetic and entertaining view of old and new problems in physics -- all in a minute!

Thanks to Nima Doroud and Bruno LeFloch for contributions and to Perimeter Institute for support.

[DrumsTheWord]

I need a good reminder occasionally just why geometry can be so useful in mathematics. Thanks for this!

[lbterlick]

To think the whole reason we can't go at the speed of light is because of triangles. Screw you trigonometry.

[nightman]

That triangle example made great sense. Thanks

[mybluemars]

So E=MC squared is also related to a right triangle? Arrgghh, , can't seem to get away from Pythagoras!

[screamingiraffe]

The best "Why mass can't reach the speed of light " video I've seen so far. Nice work! A+

[Heeknot]

If we want to travel the speed of light we must kill all the triangles. It's simple people.

[kapilesh]

I am not going to lie this was probably the only video so far which I didn't have to watch twice to understand. I am an average intelligence guy with a little interest in Science but Henry nailed it for me in this video.

[ThePCguy]

damn right triangles. I will now prove them obsolete.

[earthman]

I had been missing the momentum P variable. You helped me shape my understanding of relativity SO MUCH.

[AlonTako]

dafuq dude i just understood so much in 2 minutes i might collapse into myself

[oncebittentwiceshy]

I wonder, can we have "negative" mass ? Something that weights less than zero should pass light speed.  Yes, I know -  it sounds silly.  Maybe I should go to bed . .  . .

[BananaNeil]

So, E=(mC^2)^2 + pC^2, and because with photons, m = 0, therefore E=PC^2, excellent.

But P (momentum) = mV.... but m is still 0. so E is still 0. WTF physics?

[Fino]

My mind has been blown today !
I was doing my physics exercices during a physic lesson, and to solve one, I did some calculations and other integrals. (took me some time) And guess what ? I found E^2 = (mc^2)^2 + (pc)^2 !
The funny part is that as I wrote E = (p^2c^2 + m^2c^4)^1/2 I did not realize immediately that it was the exact same formula as I had seen in this video for ages !

[TayChinghern]

have no idea of what this wizard is saying

[Marconius]

Pretty good explanation, and I love the animation you used too! My only complaint is you use the word "mass", I would have liked at least a passing mention of the fact this is "invariant mass" (which light doesn't have), as opposed to relativistic mass.

[niklaspilot]

This is awesome! So you CAN actually describe complicated physics with basic mathematics.... :D WIN!!! 

[SamirHabibTheKing]

Newton be like I KNEW IT, I TOTALLY KNEW IT

[iiiiitsmagreta]

It never fails to amaze me how everything in math and science just *works*. Like, the same principles that apply to trigonometry and measuring triangles also explain why we can't exceed the speed of light. Just, think about that.

[iamcsxii]

E=mc^2 is about how much energy is in an object, not how much energy it can produce by moving

[clarenceho]

thank you, finally an explanation that makes sense and doesn't end with "just because"