A question about E=mc2

[Jimmy Ray]

I'm new to this so bear with me.

 

As i understand it all matter is, is lots of tightly compacted energy. so there is lots of energy in everyday objects. this is the basis for nuclear energy and nuclear bombs. they use uranium because it has the largest nucleus. but it has the downfall of all the unwanted radiation.

 

so my question really is: Why can't we use something other than uranium, like maybe limestone or iron and take the energy out of that? maybe we could even use things we would be putting in a landfill? if everything is just energy anyways we should be able to get energy out of anything?

 

 

thanks for any insight

 

Jimmy Ray

[Ice Demon]

Want a simple answer? Money. It would be 1. to expensive and 2. technology and time. It is a lot simpler with radioactive elements because of there unstable qualities. Hydogen bombs work in a different way, but with the same concept.

[Locrian]

To clarify, it isn't money that prevents us from using limestone for fission energy; the fact is that fissing atoms that limestone is made out of requires more energy than it produces. Roughly speaking the lighter the element the more energy produced by fusing it, and the heavier element the more energy produced by fissing it. You have losses in any energy production process, so when it comes to fusion and fission you use elements at far ends of the weight spectrum for good reason.

 

I would also highly object to your characterization of matter as tightly compacted energy. I don't feel that phrase has much meaning.

[Jimmy Ray]

I would also highly object to your characterization of matter as tightly compacted energy. I don't feel that phrase has much meaning.

 

 

I appreciate your clarification Locrian, I am a novice when it comes to understanding this stuff.

 

Thanks to all of you for your imput as well.

 

Jimmy Ray

[Xyph]

Apparently, black holes are 100% efficient matter-to-energy converters, in which case it wouldn't matter what you used. We're probably quite far from that at the moment, though.

[5614]

What do you mean by 100% efficient? Both energy and matter is conserved, so in what form would you consider it not useful?

[Xyph]

It wouldn't be useful as energy if it remained as matter.

[swansont]

I'm new to this so bear with me.

 

As i understand it all matter is' date=' is lots of tightly compacted energy. so there is lots of energy in everyday objects. this is the basis for nuclear energy and nuclear bombs. they use uranium because it has the largest nucleus. but it has the downfall of all the unwanted radiation.

 

so my question really is: Why can't we use something other than uranium, like maybe limestone or iron and take the energy out of that? maybe we could even use things we would be putting in a landfill? if everything is just energy anyways we should be able to get energy out of anything?

 

 

thanks for any insight

 

Jimmy Ray[/quote']

 

 

Part of the reason that Uranium gives us energy when it fissions is the same reason that it is radioactive (and the propensity to alpha decay).

 

What you have to consider is that there are two forces in a nucleus: a force of attraction - the nuclear force, which has a finite range, and the electrostatic force of repulsion of the protons, which has an infinite range.

 

Because the nuclear force is short-ranged (it's more or less attraction of nearest neighbors) the energy involved saturates. If you "built" a nucleus, as you made it bigger, there would be a larger binding energy as you added each particle and created more pairs of attracting particles, but the rate at which this energy gets bigger flattens out - a new particle added only attracts a finite number of other particles. But when you add protons, they all repel, and this repulsion keeps getting bigger, because of the infinite range of the electrostatic force.

 

So light nuclei can be fused together, and the nuclear force of attraction for the product grows faster than the electrostatic force of repulsion - there is energy released. But this is not true of heavy nuclei. Once you reach a nucleus with about 60 particles in it (about Fe on the periodic table), there are just too many protons, and the repulsion is too large.

 

For very heavy nuclei, there is so much electrostatic repulsion that it isn't held together as strongly. Getting rid of part of the nucleus doesn't change the nuclear force energy much, but it does reduce the electrostatic repulsion, so there is energy released. Which is why heavy nuclei tend to either alpha decay (eject a He-4 nucleus) or in some cases, undergo fission. Incucing fission is also possible, as happens with U-235: the nucleus is given some extra energy by absorbing a neutron, and this distorts the nucleus to the point where the electrostatic repulsion literally rips it into two parts.

 

So that's why light or intermediate nuclei won't release energy by indergoing fission. And iron would be pretty much useless as a nuclear fuel because neither fusion nor fission would tend to release energy.