The atomic blast is a product of nuclear fission, which was discovered by German scientists in the late 1930s, around the time of a very big war known as World War II. You are probably too young to have lived through this war, but it was a very important event that changed the course of both science and history. So big that we must leave the other details to your History text; all you need to know right now is that one of those changes was the discovery of nuclear fission.

Nuclear fission is a type of exothermic reaction. Recall that in Chapter 5 we defined an exothermic reaction as a reaction that gives off energy. Well, the exothermic reaction of nuclear fission involves the splitting of atoms, particularly Uranium atoms, as in the case of the atomic blast. Scientists use a special type of Uranium known as Uranium 235 in the nuclear fission used in an atomic blast. This kind of Uranium is known as an isotope.An isotope is a different form of an element that weighs either more or less than the standard form because it has greater or fewer neutrons, the neutral subatomic particles we discussed in Chapter 3. You have much experience with weight in your everyday life, whether you realize it or not, and you probably understand it very well. By now you have surely noticed that, though your little brother is much like you in appearance and mannerisms (he even wears some of your old clothing!), he weighs less than you do, and you can pick him up, and even carry him out into the backyard, but he could not do the same for you. This is because of your different weights, just like the weight differences in isotopes. Isotopes have the same make up in protons and electrons, the other two subatomic particles, as you will remember (because you are very bright!), but their weights are rather different from the standard form. The important thing to know is that there is something in the lightness of the Uranium 235 isotope that makes it more susceptible to nuclear fission, which is why scientists use it in the creation of the atomic blast.

Now, we have discussed that nuclear fission in an atomic blast relies on the isotope Uranium 235, but just how does the actual fission occur? That's a very good question (you always were such a curious boy, weren't you?). Well, the term fission comes from Latin, meaning to split, and that is exactly what occurs in nuclear fission. In the nuclear fission of U-235––a convenient abbreviation for Uranium 235––an atom of U-235 is bombarded with free moving neutrons. You have experienced bombardment; it is similar to that time you threw rocks at the hornet's nest until it finally broke free, and all of the hornets flew out, stinging you on your face and hands. That was last summer, and your mother was very distraught and you father very angry, you will recall. Well, throwing rocks at a hornet's nest is the same sort of bombardment as nuclear fission. But in this case, tiny little neutrons, so small you could never ever see them with your naked eye, are "thrown" at an atom of U-235 until the nucleus of the atom becomes weakened and tired, much like your mother after a long day of taking care of you and your brother, and breaks apart into two different nuclei (remember, that's the plural of nucleus. You are clever enough to realize that it could not be nucleuses, aren't you now. Just like your father). Those two nuclei are now part of two different, new atoms, no longer recognizable to one another as what they were together, when they made up that U-235 atom. It's not that the neutron that bombarded the U-235 atom wanted the fission to happen, per se, just as you couldn't have known that banging on the piano like that would cause your mother such a headache, nor could your father have realized that the birth of your baby brother would throw his loving wife into such a depression that she could barely get out of bed each day. No, it's wrong to assign fault in these events. But regardless of intent, the bombardment by neutrons from all directions to the nucleus of the U-235 atom causes the element to breakdown and split apart, separating into two, often unequal parts. But you already understand separation, don't you? A little too well.

We are getting a little off track, now. Let us get back to the nuclear fission! As you might imagine, the splitting of one little U-235 atom alone is certainly not enough to create a lethal atomic blast. No, in order for nuclear fission to prove its ability to obliterate, to be really powerful, it must rely on what's known as a chain reaction. Chain reactions are very common––scientists study chain reactions all of the time! You are familiar with chain reactions, too. Watching dominoes fall in long rows around the kitchen in order to delight your little brother is a twofold chain reaction. The first reaction involves the dominoes––each one that falls hits the next one and causes it to fall, which causes the next after that to fall, and so on. The second reaction is a little trickier––you hit the dominoes, causing them to fall, and their falling causes your little brother to laugh. This laughter might cause your mother, trying to sleep in the living room, to cry out of anger and frustration. But it also might cause her to laugh, to feel the first joy you have seen from her in months. That is the tricky part of chain reactions––all of the different stages must fit perfectly to keep the reaction going! This is true with nuclear fission, too. In order to keep the reaction going, neutrons from the broken nucleus of the U-235 atom must break off and bombard other U-235 atoms nearby, known as later generations of atoms, causing their nuclei(didn't I say you were clever now) to split, releasing even more neutrons to bombard even more U-235 nuclei, and so the reaction keeps going, the sobbing noises keep coming from your mother's darkened room, your father keeps working later and later every day, the yelling keeps getting louder each night, and you keep singing your brother to sleep under the tent you have made out of your bedsheets. Aren't chain reactions powerful!

But the chain reactions alone aren't exactly what make the atomic blast such a, well, blast (why don't you laugh at the joke. Are you too clever for puns?). Instead, it is the energy produced from the fission that is multiplied exponentially (there's a big word for your curious little mind now) in the chain reactions that creates enough power for the atomic blast. You see, when the U-235 atom splits apart under the constant pestering of the free neutrons, the splitting of the atom releases quite a bit of kineticenergy. You will recall from Chapter 4 that kineticenergy is the energy of motion. You experience kineticenergy on a regular basis––when you pump your legs to ride your bike away from your home late at night, when you threw those rocks at that hornet's nest in a rage last summer, all of the times you worked hard to carry your little brother out of the house, into your fort in the backyard after dinner, away from the sounds of your parents' screaming. All of those actions required kineticenergy. Well, as you might guess, kineticenergy is pretty powerful, and with enough kineticenergy built up from enough nuclearfission, scientists can create an enormous, devastating atomic blast that will reach far enough to kill hundreds of thousands of people all in one blow. Now that's strength!

But let's review what we've learned so far to make sure you've understood (try to keep up now, this is important): the atomic blast is a product of nuclearfission involving the isotope Uranium 235, or U-235 for short (lazy, aren't you? You couldn't have washed those dishes for your mother, could you?). During fission, neutrons bombard the nucleus of the U-235 atom and break it in two (she could've slept off the pain while you enjoyed the soap bubbles and delighted your little brother). This breakage releases more neutrons which then split morenuclei(but instead the dirty dishes led to the dirty kitchen which led to the dirty house), each time releasing more and more kineticenergy until there is enough kineticenergy for an enormous, earth-shattering atomic blast (and then your father came home, grew angry over the dishes, over your mother's constant crying, and began packing his big, dark suitcase, the one he only used for really long trips). But here's something I bet you didn't anticipate, just like the scientists who discovered nuclearfission in the first place (you didn't realize that that was the last time you'd see him, did you? So clever, but so oblivious, too busy worrying about your mother's sobbing to consider your father's departure): the devastation of the atomic blast doesn't even end with the actual blast. No, the destruction continues with an effect known as radiation.

You see, during an atomic blast, all of the people and animals and houses and plants within a certain range are destroyed almost instantly in a huge, blinding explosion. Other living beings, outside of this range, can go on living, sometimes completely unaffected by the blast. But still there are other people and animals that are affected by something else that is let off by the atomic blast, something you can't even see with your own eyes (it's funny how you can hardly see anything, but you feel it, don't you. So perceptive). This something is called radiation. Radiation is an awful side-effect of nuclearreactions that damages living tissue, much like a poison, but absorbed through the whole body, not just taken in through the mouth. You understand poison, though, the way your mother began poisoning herself, afterwards. You cleaned up the bottles each day, but it was a little too late by then. Enough poisonous radiation can interfere with cell division, and the more radiation a person or animal is exposed to, the less like they are to survive or come away unharmed (you couldn't stop the pain from reaching your brother, but you could still make him laugh sometimes, making shadow puppets in your fort, turning the TV loud enough to drown out your mother's sadness).

What's more, radiation doesn't always stop at the first people it hits. No, radiation can injure the geneticmaterial, which we will discuss in Chapter 11 (if you would just be patient), which is necessary for development in the next generation. In fact, after early atomic blasts, scientists began to notice that children would sometimes be born with abnormalities. You are familiar with abnormalities in your own life, like with the man down the street with no legs, or your little brother who still refuses to speak even though he is nearly four years old now. In all kinds of different ways, abnormalities change the lives of children and adults. And the trouble with abnormalities is that they can't always be detected or predicted. How could you know that your grandmother told your mother that the only way she would ever be worth anything was by marrying your father and having you? How would you have ever been able to guess that your father was afraid of you and your little brother, terrified of failing you like his father did him? And you certainly couldn't have realized the way your grandfather's father-in-law forced him into the family company, destroying his will to live! No, you couldn't know these things, but just look at their effect on you––the way your mother eyes you suspiciously as you grow older, complaining to friends that you are beginning to look just like your father. And there are probably still even more effects even you can't predict (even smart, smart you. Getting smarter every day)!

Who is to say if maybe one day you won't get together for beers with your brother and his new wife. And maybe by then he will even has his own little baby, and you will watch her as you and your brother speak of everything but your childhood. And maybe your brother will seem afraid of her, too, of his position in her life. Maybe this little daughter will grow up to bottle up all of her thoughts and feelings in order to ease your brother's anxiety, and one day maybe she will have her own children, who will walk the earth carrying inside them an inexplicable and debilitating sense of guilt. Indeed, we may not be able to see the effects immediately, but they will find a way of coming out.

The wonders of modern science!