Learn more physics!
Thanks for answering my question on bike rotational weight. Hereís another one I think about on long rides: with the high rate of obesity in the U.S., letís just say that on average every person could stand to lose ten pounds. So ten times 300 million (making the math easy) is 3 billion pounds, and at 3500 calories/pound, thatís a bunch of calories (Iíll let you figure that one out--youíre the scientists). So Iím wondering: if people lost all the weight they should, how many degrees of heat would that make, and how big a contribution to global warming? Thanks.
- mark bloom (age 50)
The trick is that global temperatures are set almost entirely by the balance between sunlight input and the Earth's infrared radiation output. Dumping a little heat into the system by exercise would have no noticeable effect.
However, what we eat does have a big effect in the long run. That's because modern agriculture uses lots of fossil fuels. Burning them releases CO2
, slowing the escape of infrared energy, i.e. the greenhouse effect. Also, raising cows not only uses lots of fossil fuels to grow grains (in the standard feeding procedure) but also releases a lot of methane (another greenhouse gas) from the cows themselves.
So if we lost weight largely by eating less, it would be very good for the planet. Biking is also very good if it replaces driving a car.
(published on 10/22/2007)
Follow-up on this answer.