How could Piccolo blow up the moon, while Goku barely managed to leave a small crater?


In Dragonball Z, when Gohan changed into an Ozoro, Piccolo found an
appropriate solution, destroy the moon. Easy-peasy.

The real question is, when Goku used his Genki Dama (on two occasions, by the
way), it never resulted in anything more than a relatively small crater. With
all the power stored inside that sphere (easy above a _billion_ , and over
9000), shouldn't it have caused a _bit_ more damage? Piccolo managed to
_destroy the moon_ , easily, with power level of less than 1000.




Piccolo isn't the only character to blow up the moon in Dragon Ball. Master
Roshi (disguised as Jackie Chun) destroys the moon at the end of the 21st
World Martial Arts Tournament using the [MAX Power
Kamehameha](http://dragonball.wikia.com/wiki/MAX_Power_Kamehameha), which
takes considerably more effort than for Piccolo. In the meantime, Kami
recreated the moon, so this isn't a plot hole.

However, it's a good question as to why the moon is so easy to destroy, while
the earth is so much harder. Part of this can be explained since the moon is
much less massive, but even then the numbers don't quite add up if we assume
the Earth and Moon are the same as ours. Let's assume that physics in the DB
universe is at least somewhat similar to our own, modulo spirit attacks and
whatever else. Of course, this assumption might be wrong, but if you start
changing how physics works, there's no reason why the moon can't be filled
with TNT so that it explodes whenever anyone so much as looks at it.

I've made some approximations in the following calculations. I calculated the
gravitational binding energy of the moon to be 1.2 * 10^29 J. That's the
minimum amount of energy to blow up the moon so that it won't reform by its
own gravity, so we can assume that the characters were using at least that
much energy. That amount would be enough to knock 3.4 * 10^20 kg of matter off
of the surface of the earth, which is roughly 0.006% of the mass of the earth.
That doesn't seem like a lot, but if we assume a uniform density of the earth,
that's about 1.6 * 10^7 cubic miles of matter, which corresponds to a cube
where each side has length 250 miles. That's a pretty huge crater. So just
saying that the moon is easier to blow up than the earth isn't going to cut
it.

There are 3 ways to resolve this. First, the earth and moon in the DB universe
could be very different from what they are here. Specifically, the moon could
be larger and less massive, and the earth smaller and more massive than in
real life. However, it takes quite a bit of stretching to get believable
values, and that's ignoring the vast power difference between DBZ Goku and DB
Roshi. If you push things that far, I wouldn't expect it to be consistent with
everything else in the series. The second possibility is that the moon is
somehow more vulnerable than the Earth to attacks. This is roughly what
Alenanno's answer says. It's entirely possible, but as far as I can tell
there's little indication of this in the series apart from the Genki Dama, so
I don't know why other attacks directed at planets would not destroy them.

This leaves the third possibility, which is my personal choice: the producers
weren't really thinking about it when they did this, and were more concerned
with making things dramatic than making them consistent. As such, I'd call
this a plot hole, but it's a pretty minor one in the grand scheme of things.




Piccolo isn't the only character to blow up the moon in Dragon Ball. Master
Roshi (disguised as Jackie Chun) destroys the moon at the end of the 21st
World Martial Arts Tournament using the [MAX Power
Kamehameha](http://dragonball.wikia.com/wiki/MAX_Power_Kamehameha), which
takes considerably more effort than for Piccolo. In the meantime, Kami
recreated the moon, so this isn't a plot hole.

However, it's a good question as to why the moon is so easy to destroy, while
the earth is so much harder. Part of this can be explained since the moon is
much less massive, but even then the numbers don't quite add up if we assume
the Earth and Moon are the same as ours. Let's assume that physics in the DB
universe is at least somewhat similar to our own, modulo spirit attacks and
whatever else. Of course, this assumption might be wrong, but if you start
changing how physics works, there's no reason why the moon can't be filled
with TNT so that it explodes whenever anyone so much as looks at it.

I've made some approximations in the following calculations. I calculated the
gravitational binding energy of the moon to be 1.2 * 10^29 J. That's the
minimum amount of energy to blow up the moon so that it won't reform by its
own gravity, so we can assume that the characters were using at least that
much energy. That amount would be enough to knock 3.4 * 10^20 kg of matter off
of the surface of the earth, which is roughly 0.006% of the mass of the earth.
That doesn't seem like a lot, but if we assume a uniform density of the earth,
that's about 1.6 * 10^7 cubic miles of matter, which corresponds to a cube
where each side has length 250 miles. That's a pretty huge crater. So just
saying that the moon is easier to blow up than the earth isn't going to cut
it.

There are 3 ways to resolve this. First, the earth and moon in the DB universe
could be very different from what they are here. Specifically, the moon could
be larger and less massive, and the earth smaller and more massive than in
real life. However, it takes quite a bit of stretching to get believable
values, and that's ignoring the vast power difference between DBZ Goku and DB
Roshi. If you push things that far, I wouldn't expect it to be consistent with
everything else in the series. The second possibility is that the moon is
somehow more vulnerable than the Earth to attacks. This is roughly what
Alenanno's answer says. It's entirely possible, but as far as I can tell
there's little indication of this in the series apart from the Genki Dama, so
I don't know why other attacks directed at planets would not destroy them.

This leaves the third possibility, which is my personal choice: the producers
weren't really thinking about it when they did this, and were more concerned
with making things dramatic than making them consistent. As such, I'd call
this a plot hole, but it's a pretty minor one in the grand scheme of things.

