Could you explain this?

[WiFO215]

After the link to TED was posted a few threads below, I began to browse through the videos and I found this one which I liked a lot.

http://www.youtube.com/watch?v=5hJCxSiH4ts&feature=channel_page

I got questions 1 and 2 right. But the 3rd and 4th questions wrong and along the lines of the misconceptions he was referring to. I understood 4 myself but his explanation for 3 was a bit brief and I'm not sure I got it. Could someone explain the answer to Q3?

 

[Cyrus]

Why don't you just put this video in the TED thread?

 

[Ivan Seeking]

It is the angle of incidence that make the difference. As the sun gets lower in the sky, the angle of incidence is smaller, so the total energy received is smaller than in the summer when the sun is nearly directly overhead. Note that in the arctic, in the winter, the most extreme example of winter, the suns rays are striking the Earth at almost glancing angles.

The total energy received over a fixed interval goes as the dot product of the vector representing the sun's rays, and the area vector of the Earth's surface, at any point.

 

[WiFO215]

Why don't you just put this video in the TED thread?

Alright. I shall do that.

EDIT: I have done so. The mods can delete this thread now.