# Why is E=MC2 significant?

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I understand it’s “energy equals mass times the speed of light squared”, but it’s always portrayed as the most significant equation.
Is this just because Einstein was a popular figure, or is it particularly important in understanding the universe? Moreso than other equations?

In: Physics

Before this, the ideas were murky in physics about the relationship between matter and energy. They were seen as different things. This basically demonstrated that all things are energy. Then it puts down the conversion between the two in a way that explains nuclear fusion, fission, and radioactivity.

In real world ways it explained radioactivity. It also explained why Mercury’s orbit didn’t act in Newtonian physics ways, leading to a fundamentally different understanding of the universe.

First thing, that’s actually a simplified version of Einstein’s equation.

What this equation tells us is that it’s possible to convert between mass and energy. This is a bit of a bonkers idea. From a young age, we’re used to the idea that mass doesn’t change. You pour something from one container into another and the amount of stuff stays the same. Even when something gets burned, all that happens is the stuff gets turned into gasses, which still have mass. The energy we get is unlocked from being stored in the bonds of the molecules, but it’s not new energy.

E=m×c² tells us that we can actually convert physical matter into energy. This is what happens in nuclear reactors. It’s not that stuff gets turned into gas and the energy is unlocked. The matter itself actually *becomes* energy. So it’s a pretty simple equation that rolls off the tongue pretty well, but the idea contained in it is deep and powerful and far beyond what we are used to in everyday life.

The importance is that it said that energy can be converted to mass, and mass can be converted to energy. And that a tiny little bit of mass can yield a huge amount of energy. That’s an absolutely insane thing to understand. Prior to E=MC^2 if you wanted to do an experiment where you burned a candle and checked if any mass was lost you could be pretty confident no mass had been. The gasses you capture would weigh the same as the candle well beyond the ability of your scale to distinguish. And yet it doesn’t. Some tiny, tiny, tiny, bit of mass is lost in that process. Likewish a fully charged vs. fully discharged battery has a different mass.

All of the above.
Einstein was famous, that helped a lot.
It’s also short and doesn’t use a lot of more complex sciences terms.
It’s useful in that it tells you how much energy a nuclear bomb/ fuel would give off (a certain percentage of the mass is converted into energy). And everyone was obsessed with everything atomic at the time.

It’s not so much fundamental to relativistic physics as it is the culmination.

If you look at all the things that go into deriving the equation you get a pretty quick summary of everything that went into advance physics since Newton.
It’s what happens when a whole bunch of terms in relativistic physics starts canceling out or going to zero.

I think your question is just as much why is it significant in pop culture, as well as why is it significant in physics?

It’s significant in pop culture for many reasons. One of them is how famous Einstein became. Everyone knows who he was, but many people don’t actually know that much about his work or what it means. E=mc^(2) is a relatively simple equation with a relatively simple meaning and so people could latch on to it as understanding Einstein’s work. It’s also just such an interesting revelation that mass is (constrained) energy (the c^(2) is just a unit conversion, you could create a new unit system in which c=1 and so E=m).

It is significant in physics because it helps us understand where the mass of a system comes from, or where another type of energy came from. It is fundamental to particle and nuclear physics, which are both foundations of much of other physics and modern technology.

Because if shows a fundamental truth about the universe that was completely unknown before, AND, it is a very simple equation. Take a look at other physics equations and you will see that they are (for the most part) very complicated.

People tend to value elegance and simplicity and when such an important piece of knowledge can be expressed in such a simple equation, that’s a big deal.

Also, it’s not simply that mass can be converted into energy, it works the other way around as well. There was a paper that blew up just last week which showed that energy can be converted into matter as well. It analyzed a lot of data from particle accelerators and showed that there are times when photons convert into electron proton pairs (I think, I’m solid on the electron iffy on the proton. It was definitely a pair).

That’s equally mindblowing, that photons, light, can, under the right circumstances, turn into matter.

It’s significant because it explains a lot about what mass is. It’s a form of carrying energy.

The mass of the particles you are made up of (quarks and electrons) together is nowhere near enough to account for your total mass. That mass comes from the energy in the bonds (gluons) that hold these particles together. A lot of energy in fact – proportional to the square of the speed of light.

The more energy an object contains, the more it weighs. So a hot pan weighs more than a pan at room temperature. Why, because heat is a form of energy and mass is a way of carrying that energy.

If you can split apart the bonds in these gluons, you can release a terrific amount of energy – the bonds in a walnut can power a whole city.

The bonds in atoms of uranium were used to bomb cities.

Source: the big questions in physics – Michael Brooks

Other s have explained what it means but it’s not necessarily more important than say, the law of gravitation which was used for the moon missions.

It’s fame likely comes form [this](http://content.time.com/time/covers/0,16641,19460701,00.html) TIME cover which linked EInstein the equation and the power of the atom bomb in peoples minds just as the cold war was starting.

the TLDR version: it offers a mathematical link between Mass and Energy that allowed us as a result to link Mass with Gravity and explains some of oddities we noticed regarding the universe(specifically how bodies like Stars affect the space around them)

it also offers an explanation as to why reaching lightspeed might not be physically possible for anything that has Mass(which is a bit of pickle because we still aren’t quite sure if light itself is a particle or wave. the 1st would mean there is something about this particle that we dont understand, while the latter would mean that this wave would carry infinite energy, which is a big “Nope”.)

Lastly this equation also proves that it is possible to turn Mass into energy and viceversa, which came in handy at understanding nuclear fusion/fission.