Curious to know how much plastic, which is made with oil, is used to make an electric car weigh less. And by using electricity made by burning coal or oil aren't you just rearranging how you use energy, coal made electricity vs gasoline? What would be a break even point? Kind of like taking over 20 years to break even by driving a hybrid truck, or Porsche SUV. And while I'm at it, why do electric car have to be so goofy looking, as if the owners want everyone to know they are driving an electric car.........oh, never mind. Kind of like charity where celebrities get their photo taken while doling out turkey meals in the morning on Thanksgiving, then get into their Porsche SUV and go back to their million dollar home, while I just give money anonomously.
As the Earth's moon is locked in what is called 'Tidal Locking', the far or dark side of the moon was not seen by any human until December, 1968, during the Apollo 8 mission. From Earth, only about 59% of the moon's surface is visible although not all of that at any one particular time of course.
Eventually, the Earth may be tidally locked with the moon, at which point 1 Earth day would equal one lunar month.
Brian
I'm surprised by this. I always thought it would be 50% or maybe 50.009%. I didn't think the angle difference between a moon rise and moon set and north pole and south pole would be enough to see another 9% of the surface. But after calculating ( cos(7,000/240,000) I used 7,000 since the diameter of the moon is ~1,000 miles and earth is ~8,000 miles ) there is almost 1 degree difference in observation angle.
I think the 50% thought is quite intuitive but incorrect because we do not observe from a point but rather the surface of a <relatively> large object and so have varying views of the moon.
But that is not the majority of the reason anyway- most of the increase beyond 50% is due to libration, of which there are three kinds: libration in latitude, libration in longitude and diurnal libration.
There is a pretty good explanation along with a video of how it works here:
http://www.wwu.edu/skywise/lunar_libration.html
When doing celestial navigation by hand, via a sextant and sight reduction tables, there is an error correcting calculation needed because the Earth does not rotate neatly but rather wobbles slightly and unless compensated for can cause, if memory serves, up to an eight minute error, which would be eight nautical miles at the equator- not an insignificant error.
Hey, this is not my world, I just happen to live here and so have to compensate all the time for lots' of stuff.
Brian
Exactly. 2 people observing the moon on the horizon, one from around the north pole the other the south pole will be seeing it from about a 1 degree angle difference. Now add in this libration wobble thingy and I now see why we can see 59% from the surface of the earth.
So we all know there are 52 weeks in a year, and we all know there are 7 days in a week. So obviously there are (7 X 52 =) 364 days in a year.
Brian
We all know there are 365 days in a year (except leap years) and 7 days in a week. So obviously there are 52.1428571 weeks in a year, except leap years. We could go round and round all day.
Toasted England and the Queen tonight with my Queen Elizabeth coronation shot glass. Seeing double at the moment so I have one eye shut as I post this.