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.