that a doughnut is topologically equivalent to a coffee mug, because each has
precisely one hole (you know where it is in the doughnut; the hole in the coffee
mug is where you put your finger through when you hold the mug). If you had a
piece of clay, and poked a hole in it, you could shape it like a doughnut (easy) or
a coffee mug (not so easy) by stretching and bending the clay without any fur-
ther tearing.- See http://en.wikipedia.org/ wiki/Standard_Model. This is an excellent short ex-
position of the Standard Model, along with a beautiful chart that puts the peri-
odic table to shame. You have to click several times on the chart before you get to
a readable resolution, but it’s worth it. - See http://en.wikipedia.org/ wiki/ Electroweak. The first two paragraphs give you
all you need, but if you like staring at equations, there’s a nice little window that
has the basic equations of the theory—if Emc^2 is the most impressive equation
you’ve ever seen, take a look. Because Wikipedia is user composed, the depth of
treatment in different sections varies wildly. I’m not a physicist, but I can recog-
nize the symbols and what the equations are saying, but I have no idea where
they come from and how they might be used. - See http://en.wikipedia.org/ wiki/ Big_Bang. If explanatory Web sites were rated
on a 1 to 10 scale, this one would be a 10 —it’s as good as it gets. Good graphics,
understandable explanations, excellent hyperlinking—this site is so good if it
had pop-up ads, you wouldn’t mind it. - See http:// en .wikipedia .org/ wiki/ Steady _State _theory. This site is nowhere near
as impressive as the one for the big bang theory. No graphics, a rather perfunc-
tory explanation, but that’s not really surprising, because the steady state theory
is dead, dead, dead. I imagine that sighs of relief were heard throughout the
astrophysical community when this theory bit the dust, because matter-energy
conservation is so fundamental a principle you’d hate to abandon it.
40 How Math Explains the World