# Why Use So Small A Mass For The A-Bomb

#### Scram

I am going to offer my rudimentary understanding of E=mc2.

I have always taken that equation to mean that massive amount of Energy can be gleaned from even the smallest amount of mass.

If that simplistic view is correct, then I want to raise a question:

If great Energy can be obtained from small mass, why not make use of greater mass...thus the Energy would be even greater. Why go for the tiny mass of a nucleus of an atom? Wouldn't something of greater mass produce even more energy than what the A-Bomb unleashed?

#### neila9876

The key might be: the technology people hold (to unleash energy from matter).

#### topsquark

Forum Staff
I am going to offer my rudimentary understanding of E=mc2.

I have always taken that equation to mean that massive amount of Energy can be gleaned from even the smallest amount of mass.

If that simplistic view is correct, then I want to raise a question:

If great Energy can be obtained from small mass, why not make use of greater mass...thus the Energy would be even greater. Why go for the tiny mass of a nucleus of an atom? Wouldn't something of greater mass produce even more energy than what the A-Bomb unleashed?
I think it's likely to be a case of efficiency: Why build one big bomb (for one target) when you can build two (for two targets.)

-Dan

#### Woody

I think Neila has it,
There are only certain circumstances (that we have found)
where mass to energy conversion can be triggered at will.

Even in an A-Bomb the percentage of the reacting mass that becomes energy is actually tiny.

It is actually only the mass that is associated with the energy binding the nucleus of the atoms together that is released,
not the actual mass of the neutrons and protons etc...

1 person

#### HallsofIvy

First in an atomic explosion only a very small part of the mass is converted to energy. Second, as of the building of the first three atomic bombs, only a small amount of U235 was available. There was plenty of "Uranium" but only U235 was usable for a bomb and it was difficult to extract from the rest.