Here, I’ll just summarize the physics of the
nuclear weapon/nuclear plant.
Let’s start with an atom. An atom is
made of electrons surrounding a much smaller
(about 100000 times smaller than the atom)
positively charged center called the nucleus. The
nucleus itself is made of smaller particles,
namely protons (positively charged) and neutrons
(neutral particles). All of the mass (weight) of
the atom is mostly stored within the nucleus.
Larger the number of protons and neutrons in the
atom, heavier the atom is. So Hydrogen having only
a single proton and no neutron is the lightest
element and most abundant element in the universe
too! This is why a block of Lead or Iron is
heavier compared to a block of Aluminum. Uranium
is a very heavy element with 92 protons.
Now, remember the famous energy-mass equivalence
principle developed by Einstein: E =
mc2 . This meant that if all the
mass inside the nuclei can be converted to energy,
you can make a bomb.
How do you convert the mass into energy?
By splitting the nucleus and reducing its
mass! So if one splits Uranium’s nucleus, a
huge energy is bound to be released.
The splitting of the nuclei can be done by
bombarding the atom with a heavy particle. Proton
is a good candidate, except for its positive
charge that will be repelled by the positively
charged nucleus and deflect. So the physicists
decided to use the neutron bombardment, which is
neutral and won’t be repelled by the positive
Even with the neutron bombarding, a single atom
will not give enough energy to make a bomb or get
useful energy out of it. The physicists learnt
that it has to be a chain reaction, which
means that for every neutron bombardment, there
must be more neutrons released by the nucleus and
these released neutrons will bombard other nuclei
creating more and more neutrons in the process.
This chain reaction produces LOTS of energy by
multiplying the number of neutrons, enough to make
a nuclear weapon or a nuclear plant.
If this chain reaction is left uncontrolled,
i.e. the neutrons released are always allowed to
collide with a nucleus, we have an nuclear bomb.
On the other hand, if this chain reaction is
controlled by blocking the neutrons released,
usually using heavy water (Hydrogen with one
proton and one neutron called “Deuterium” combined
with oxygen: D_2O), we have a source of nuclear
energy that can be used to run your computer,
phones and everything useful to you.
This addresses the physics portion of the
answer to “why do we have nuclear power and
weapons” question. If this question was
asked from a humanitarian/existential point of
view, I don’t have an answer. But, may be reading
this document could help you:
please read here