Vultures have bald heads to…

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…regulate temperature and (maybe) to keep feathers clean while eating. Keeping the feathers clean was my inspiration for this sketchplanation - there’s something about the cold practicality of not messing up your feathers while you’re tucking into some carrion. However, it looks like it is more likely to be for the more prosaic reason of regulating temperature and keeping cool. As Dominic McCafferty, at the University of Glasgow points out:

‘…other groups of scavengers, particularly giant petrels, have feathered heads. Large mammalian scavengers also don’t have bald heads, so why vultures?’

Should you be interested, read more at the University of Glasgow’s Why do vultures have bald heads?

Published 19 Mar 2015

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Seasons

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The Earth’s tilt causes the changing seasons. As the Earth revolves around the sun, the tilt of its axis—23.5 degrees—causes the two hemispheres, North and South, to be either tilted towards the sun or away from it at different times of the year. In Winter, because light from the sun hits at a greater angle and closer to the poles, the solar energy gets spread over a larger area. This makes it weaker and cooler and gives rise to colder weather (aka winter). In summer, the sun's light hits more directly and is closer to the equator, so it’s concentrated on a smaller area, leading to hotter days. Because of the tile of the earth, seasons are reversed in the two hemispheres, so if it’s winter in the Northern Hemisphere, it’s summer in the Southern and vice-versa. The further from the equator you go, the bigger the effect of the seasons. As an example, temperatures in Ecuador stay relatively constant throughout the year, while the poles experience extremes of 24-hour daylight or 24-hour night and great freezes and thaws. A version of this sketch, along with a number of other planetary and seasonal ideas, features in my book Big Ideas Little Pictures Also see: Autumn leaves Equinox Solstice…The Earth’s tilt causes the changing seasons. As the Earth revolves around the sun, the tilt of its axis—23.5 degrees—causes the two hemispheres, North and South, to be either tilted towards the sun or away from it at different times of the year. In Winter, because light from the sun hits at a greater angle and closer to the poles, the solar energy gets spread over a larger area. This makes it weaker and cooler and gives rise to colder weather (aka winter). In summer, the sun's light hits more directly and is closer to the equator, so it’s concentrated on a smaller area, leading to hotter days. Because of the tile of the earth, seasons are reversed in the two hemispheres, so if it’s winter in the Northern Hemisphere, it’s summer in the Southern and vice-versa. The further from the equator you go, the bigger the effect of the seasons. As an example, temperatures in Ecuador stay relatively constant throughout the year, while the poles experience extremes of 24-hour daylight or 24-hour night and great freezes and thaws. A version of this sketch, along with a number of other planetary and seasonal ideas, features in my book Big Ideas Little Pictures Also see: Autumn leaves Equinox Solstice

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