September 6th, 2008
People who read books are suckers. Why put yours eyes through hours of tortuous labour when you can trade the horrible noise pollution of the city for a beautifully read audiobook? My latest audatory book digestion was Christopher Hitchen’s tirade on the big G in God Is Not Great.
In the book, Hitchens shares a fond memory of his grade school teacher informing the class that God made all the trees and grass the colour green because it was most relaxing to the human eye. For brevity’s sake, Hitchens clarifies that “eyes were adjusted to nature, not the other way around” but it’s really a fantastic question. Why is the grass green?
Colour mostly boils down to the absorption spectrum of a particular chemical element in an object. Flowers have evolved enticing colours to attract pollinators, birds/humans have evolved sexy tailfeathers to attract mates, but sometimes nature throws you a color you didn’t expect. Especially with stuff that I expect would be either black or white.
Why are plants not black?
Plants are green because they are packed with the photoreceptor chlorophyll. This pigment is used to capture energy from the sun to fuel the chronic plant craving for sugars. So if plants evolved to be truly efficient, why the heck are they wasting all that green light and reflecting it at us?
This post by Todd Holland at University of Illinois explains that plants get all they need from the sun in the blue and red portions of sunlight. In different sunlight conditions, astrobiologists theorize that plants may be completely black!
Why is the sun not white?
The surface of the sun is like 6000K. The emission spectrum of a black-body is definitely in the white area, so why does the sun look yellow and even orange at sunsets?
The sun is yellow for the same reason that the sky is blue. The molecules in our atmosphere scatter sunlight like nobodies business and since blue and violet light is scattered easiest, we are left with a red/orange/yellow looking sun. The sun is orangiest when light has to pass through more atmosphere when we observe it at dusk/dawn.
Why is the moon white?
Now that I’ve explained why the sun is yellow, why the heck isn’t the moon also yellow? It’s the same light as the sun and it travels through the same amount of atmosphere. Damn you science you make no sense!
The reason the moon appears white is because the light is too dim! Our eyes are too crappy at night time because we only use the rods in the back of our eyes which don’t provide very good color information.
Why is space not white?
If there are 70 sextillion stars in the visible universe, why isn’t space completely white? Dudes in the 1800′s were all over this problem and it’s known as Olbers’ Paradox. I wish I had a paradox named after me… Anyway, Wikipedia gives the “mainstream” explanation as follows:
- The speed of light is finite so a lot of starlight hasn’t reached us yet.
- The age of the universe is finite due to the Big Bang so beyond a certain point there aren’t any stars at all.
- Space is expanding so visible light gets shifted into the UV and microwave spectrum which explains that snazzy cosmic microwave background radiation.
Why are black holes black?
It seems obvious that photons cannot escape the super strong black hole gravity, but why? Photons have zero rest mass and equation for a gravitational force has mass in it… so you should be saying “i dont c what u did there”.
Turns out that Einstein came up with this crazy thing called General Relativity says that the geometry of space time can be curved, which in turn, can alter the trajectory of photons.
Why is snow snow white?
Tap water is clear, ice cubes are clear, and Dasani is the clearest of all since it costs extra. Snowflake whiteness comes from the complexity and imperfections of the snowflake structure. Light gets scattered all over the place and makes for the best Christmas ever.