It took me a few hours to complete these rough solutions, without any references. I am not entirely confident in their accuracy. It might be fun to compare solutions, though, and hopefully my thought process will be helpful in at least a few places.

- What's the gross state product of California?
*(10: 10-100 billion)* - How many people die per day on Earth?
*(6: 1-10 million)* - How many traffic lights are there in New York City?
*(a few hundred streets squared should give an upper bound to the intersections, so 4: 10-100k)* - How many Chinese restaurants are there in the U.S.?
*(4, which would work out to a few thousand in each state)* - How many passenger-miles are flown each day in the U.S.?
*(100k's of travelers * 100's of miles = 5 + 2)* - How many volumes are there in the Library of Congress?
*(tens of millions = 7)* - How many notes are played in the full career of a concert pianist?
*(a page of music has probably 10 bars, each of which has 10-100 notes (3); concert pianist probably plays 100s of pages of music a day (2); plays every day a year (2); plays tens of years (1); add the exponents: 8... hundreds of millions)* - How many square miles are there in the U.S.? How many of them have you been in?
*(1,000 x 1,000 = 3 + 3 = 6; not sure what he means by "been to," but I probably occupy a square foot, travel a few thousand (effectively unique) square feet a day (so < 10 miles), and have lived for more than 8,000 days: say 4, to account for driving/flying)* - How many syllables have been uttered by humans since 1400 A.D.?
*(100m people * a few thousand words a day (so, 10k+ syllables) * hundreds of years * hundreds of days = 8 + 4 + 2 + 2 = 16)* - How many "300" games are bowled in the U.S. per year?
*(probably 100-1,000, so 2)* - How many stitches are there in a stocking?
*(I have no idea how these things are woven, or what constitutes a "stitch," but as a wild guess, maybe a 100k or so: 5)* - How many characters does one need to know to read a Chinese newspaper?
*(I've heard about 10,000)* - How many sperms are there per ejaculate?
*(Douglas! A few million?)* - How many condors remain in the U.S.?
*(What's a condor? A few hundred?)* - How many moving parts are in the Columbia space shuttle?
*(I doubt that very many parts move, maybe a few thousand little guys?)* - How many people in the U.S. are called "Michael Jackson"? "Naomi Hunt"?
*(high 100ks for "Michael"s (5), maybe 70% born late enough for "Thriller" to do anything (low 5), then probably a 1% shot of having the name... so a few thousand? "Naomi Hunt" might be a full order of magnitude lower, giving 100 or so)* - What volume of oil is removed from the earth each year?
*(hundreds of millions of barrels? Maybe I should read the news...)* - How many barrels of oil are left in the world?
*(my last answer * < 100 years left: billions of barrels? 9)* - How much carbon monoxide enters the atmosphere each year in auto exhaust fumes?
*(sensing an agenda here... 100s of millions of cars, 10-100lbs each a day? 9)* - How many meaningful, grammatical, ten-word sentences are there in English?
*(the Q is ten words, too, not surprisingly... this is a hard one. Suppose there are 100k-1m common words, then 10 spots gives (100k-1m)^10, or 5 * 10 = 50 on the big scale. But the odds are pretty low it's grammatical, or meaningful, which might bring you way down, especially since each word has a chance of ruining the whole thing. Say, 10 independent chances to screw things up, at a .1% success rate each time, so the odds of a success are (1/1000)^10 or -30. Gives us 20 for the final answer)* - How long did it take the 200-inch mirror of the Palomar telescope to cool down?
*(I imagine things cool down at a decreasing rate, and that things with a high surface area cool down faster... maybe a few days?)* - What angle does the earth's orbit subtend, as seen from Sirius?
*(10-100 degrees?)* - What angle does the Andromeda galaxy subtend, as seen from earth?
*(1-10 degrees?)* - How many heartbeats does a typical creature live?
*(say, about one a second... 60 seconds * 60 minutes * 24 hours * 365 days * 20 years = 6, a few million)* - How many insects (of how many species) are now alive?
*(vaguely recall hearing "trillions of insects," maybe 100m's * 10k's of species?)* - How many giraffes are now alive? Tigers? Ostriches? Horseshoe crabs? Jellyfish?
*(5, 5, 5, 7, 8)* - What are the pressure and temperature at the bottom of the ocean?
*(10k times the surface? 100 times cooler?)* - How many tons of garbage does New York City put out each week?
*(10s of millions of people * 10 pounds a week = 100 million pounds/1,000 lbs per ton = 5)* - How many letters did Oscar Wilde write in his lifetime?
*(5-10 a day * 365 * 35 (?) = 4, 10k)* - How many typefaces have been designed for the Latin alphabet?
*(thousands?)* - How fast do meteorites move through the atmosphere?
*(100k miles per hour? no idea)* - How many digits are in 720 factorial?
*(say, each of 10 * 11 * 12 * ... * 99 in the product contributes a digit, and each of 100 * 101 * ... * 720 contributes 2, for a total of 711 digits... so, 3)* - How much is a brick of gold worth?
*($10k?)* - How many gold bricks are there in Fort Knox? How much is it worth?
*(I'll work backwards: a few hundred billion / 10k = 11 - 4 = ten million bricks?)* - How fast do your wisdom teeth grow (in miles per hour, say)?
*(to be generous, maybe an inch in 20 years.. then, do some dimensional analysis to give -7 (on the exponent scale))* - How fast does your hair grow (again in miles per hour)?
*(one inch in 20 days? cuts off two orders of magnitude, -5)* - How fast is Venice sinking?
*(a foot every 1,000 years?)* - How far is a million feet? A billion inches?
*(America is probably 2,000 * 5,280 ft wide, say 3 + 4, or ten million feet; so maybe the width of Texas? a billion inches is 7 - 1 + 3 = 2 orders of magnitude more, or about 100 million feet... say, two times around the globe?)* - What is the weight of the Empire State Building? Of Hoover Dam? Of a fully loaded jumbo jet?
*(a million tons? 10 million? 100?)* - How many commercial airline takeoffs occur each year in the world?
*(100k passengers / 100s on a flight = 1,000s flights a day = 3 + 2 = 5... probably 6 because 5 seems low)*

Here are my answers in raw format, in case anyone is interested in processing collective results.