(Glazba)
You probably already know everything is made up of little tiny things called atoms or even that each atom is made up of even smaller particles called protons, neutrons and electrons. And you've probably heard that atoms are small. But I bet you haven't ever thought about how small atoms really are. Well, the answer is that they are really, really small. So you ask, just how small are atoms? To understand this, let's ask this question: How many atoms are in a grapefruit? Well, let's assume that the grapefruit is made up of only nitrogen atoms, which isn't at all true, but there are nitrogen atoms in a grapefruit. To help you visualize this, let's blow up each of the atoms to the size of a blueberry. And then how big would the grapefruit have to be? It would have to be the same size of -- well, actually, the Earth. That's crazy! You mean to say that if I filled the Earth with blueberries, I would have the same number of nitrogen atoms as a grapefruit? That's right! So how big is the atom? Well, it's really, really small! And you know what? It gets even more crazy. Let's now look inside of each atom -- and thus the blueberry, right? -- What do you see there? In the center of the atom is something called the nucleus, which contains protons and neutrons, and on the outside, you'd see electrons. So how big is the nucleus? If atoms are like blueberries in the Earth, how big would the nucleus be? You might remember the old pictures of the atom from science class, where you saw this tiny dot on the page with an arrow pointing to the nucleus. Well, those pictures, they're not drawn to scale, so they're kind of wrong. So how big is the nucleus? So if you popped open the blueberry and were searching for the nucleus ... You know what? It would be invisible. It's too small to see! OK. Let's blow up the atom -- the blueberry -- to the size of a house. So imagine a ball that is as tall as a two-story house. Let's look for the nucleus in the center of the atom. And do you know what? It would just barely be visible. So to get our minds wrapped around how big the nucleus is, we need to blow up the blueberry, up to the size of a football stadium. So imagine a ball the size of a football stadium, and right smack dab in the center of the atom, you would find the nucleus, and you could see it! And it would be the size of a small marble. And there's more, if I haven't blown your mind by now. Let's consider the atom some more. It contains protons, neutrons and electrons. The protons and neutrons live inside of the nucleus, and contain almost all of the mass of the atom. Way on the edge are the electrons. So if an atom is like a ball the size of a football stadium, with the nucleus in the center, and the electrons on the edge, what is in between the nucleus and the electrons? Surprisingly, the answer is empty space. (Wind noise) That's right. Empty! Between the nucleus and the electrons, there are vast regions of empty space. Now, technically there are some electromagnetic fields, but in terms of stuff, matter, it is empty. Remember this vast region of empty space is inside the blueberry, which is inside the Earth, which really are the atoms in the grapefruit. OK, one more thing, if I can even get more bizarre. Since virtually all the mass of an atom is in the nucleus -- now, there is some amount of mass in the electrons, but most of it is in the nucleus -- how dense is the nucleus? Well, the answer is crazy. The density of a typical nucleus is four times 10 to the 17th kilograms per meter cubed. But that's hard to visualize. OK, I'll put it in English units. 2.5 times 10 to the 16th pounds per cubic feet. OK, that's still kind of hard to figure. OK, here's what I want you to do. Make a box that is one foot by one foot by one foot. Now let's go and grab all of the nuclei from a typical car. Now, cars on average weigh two tons. How many cars' nuclei would you have to put into the box to have your one-foot-box have the same density of the nucleus? Is it one car? Two? How about 100? Nope, nope and nope. The answer is much bigger. It is 6.2 billion. That is almost equal to the number of people in the Earth. So if everyone in the Earth owned their own car -- and they don't -- (Cars honking) and we put all of those cars into your box ... That would be about the density of a nucleus. So I'm saying that if you took every car in the world and put it into your one-foot box, you would have the density of one nucleus. OK, let's review. The atom is really, really, really small. Think atoms in a grapefruit like blueberries in the Earth. The nucleus is crazy small. Now look inside the blueberry, and blow it up to the size of a football stadium, and now the nucleus is a marble in the middle. The atom is made up of vast regions of empty space. That's weird. The nucleus has a crazy-high density. Think of putting all those cars in your one-foot box. I think I'm tired.
Vjerojatno već znate da je sve stvoreno od malih čestica zvanih atomi. Također zasigurno znate da je svaki atom sastavljen od još manjih čestica zvanih protoni, neutroni i elektroni. I vjerojatno ste čuli da su atomi mali. Ali vjerujem da niste razmišljali o tome koliko su zaista mali. Pa, odgovor je da su zaista, zaista, zaista mali. Pa se pitate, koliko su zaista atomi mali? Kako bismo ovo razumjeli, postavimo ovo pitanje: Koliko atoma ima u grejpu? Pretpostavimo da se grejpu sastoji samo od atoma dušika, što nije u potpunosti istina, ali postoje atomi dušika u grejpu. Kako bismo vam pomogli to vizualizirati, povećajmo svaki atom na veličinu borovnice. I onda koliki bi morao biti grejp? Morao bi biti iste veličine -- pa kao Zemlja. To je suludo! Hoćete reći da ako napunim Zemlju borovnicama, imao bih isti broj dušikovih atoma kao grejp? Tako je! Pa koliki je atom? Pa, zapravo je jako, jako, jako, jako mal. I znate što? Postaje još luđe. Pričajmo sada o unutrašnjosti svakog atoma -- i borovnici? Što vidite ovdje? U centru atom je nešto što se zove jezgra, koja sadrži protone i neutrone, i sa vanjske strane vidjeli bi elektrone. Pa kolika je jezgra? Pa, ako su atomi kao borovnice u Zemlji, kolika bi bila jezgra? Možda se sjećate starih slika atoma s nastave, gdje ste vidjeli ovu malu točku na stranici sa strelicom koja pokazuje na jezgru. E, pa te slike nisu napravljene srazmjerno, tako da su ponešto krive. Kolika je jezgra? Ako bi otvorili borovnicu i tražili jezgru, znate što? Bila bi nevidljiva. Premala je da bi se vidjela! OK. Povećajmo atom -- borovnicu -- na veličinu kuće. Zamislite loptu koja je velika kao dvokatnica. Pogledajmo jezgru u središtu atoma. I znate što? Bila bi jedva vidljiva. Kako bismo shvatili kolika je jezgra, moramo povećati borovnicu na veličinu stadiona. Zamislite loptu veličine nogometnog stadiona, i u sred tog atoma, našli biste jezgru, vidjeli biste je! I bila bi veličine male pikule. I ima još, ako vas već sada nisam raspametio. Pogledajmo još malo atom. Sadržava protone, neutrone i elektrone. Protoni i neutroni žive unutar jezgre, i sadrže gotovo svu masu atoma. Na samom rubu su elektroni. Ako je atom lopta veličine stadiona, sa jezgrom u središtu i elektronima na rubu, što se nalazi između jezre i elektrona? Iznenađujuće, odgovor je prazan prostor. (Zvuk vjetra) Tako je. Prazno! Između jezgre i elektrona postoje veliki prazni prostori. Sad, tehnički postoje neka elektromagnetska polja. ali po pitanju stvari, materije, prazno je. Upamtite ova velika regija praznog prostora je unutar borovnice, što je unutar Zemlje, a to su zapravo atomi u grejpu, Još jedna stvar, ako mogu biti bizarniji. Pošto je sva masa atoma u jezgri -- postoji neka količina mase u elektronima, ali većina je u jezgri -- koliko je gusta jezgra? Pa, odgovor je lud. Gustoća tipične jezgre je četiri puta 10 na sedamnaestu kilograma po metru kubnom. Ali to je teško vizualizirati. Ok, prebacit ću u engleske jedinice. 2.5 puta 10 na šesnaestu funti po kubnoj stopi. OK, to je još uvijek teško pojmiti. OK, ovo želim da učinite. Napravite kutiju koja je velika stopu puta stopu puta stopu. Sada pokupimo sve jezgre iz tipičnog auta. Sada, auti prosječno teže 2 tone. Koliko jezgri auta bi morali staviti u kutiju da biste imali jednu kutiju iste gustoće kao jezgra? Je li jedan? Dva? 100? Ne, ne i ne. Odgovor je puno više. 6,2 milijarde. Skoro koliko ima ljudi na Zemlji. Kada bi svi na Zemlji posjedovali vlastiti auto -- a ne posjeduju -- i stavimo sve aute u vašu kutiju, bila bi gustoće kao jezgra. Kažem da ako uzmete svaki auto na svijetu i stavite ga u kutiju, imali bi gustoću jedne jezgre. Ok, ponovimo. Atom je zaista, zaista, zaista malen. Zamislite atome u grejpu kao borovnice u Zemlji. Jezgra je suludo mala. Pogledajte u borovnicu i povećajte ju na veličinu stadiona, i sada je jezgra pikula u sredini. Atom je sačinjen od velikih regija praznog prostora. To je čudno. Jezgra je suludo gusta. Zamislite stavljati one aute u vašu kutiju. Mislim da sam umoran. (Zjevanje)