“Whenever I gaze up at the moon, I feel like I’m on a time machine. I am back to that precious pinpoint of time, standing on the foreboding — yet beautiful — Sea of Tranquility. I could see our shining blue planet Earth poised in the darkness of space.” –Buzz Aldrin

Seen from afar, Earth is often described as a pale blue dot. But why is our planet blue? Is it because the skies are blue? That can’t be right, or the clouds and icecaps would appear blue-hued as well. Is it because the blue skies are reflected by the oceans? That can’t be right either, or we wouldn’t see different shades of blue at different oceanic depths.

Image credit: NASA’s Blue Marble / VIIRS / Suomi NPP.

Image credit: NASA’s Blue Marble / VIIRS / Suomi NPP.

The answer lies in the properties of water itself: it absorbs different wavelengths of light with different efficiencies, and is worst at absorbing blue light. That’s why, the deeper you go, the bluer underwater marine life appears, and that’s also why the blue light is most efficiently reflected back off the water, at all depths, and into space.

Image credit: public domain photo by pixabay user shanerkidwell, via https://pixabay.com/en/turtle-ocean-blue-sea-underwater-287973/.

Image credit: public domain photo by pixabay user shanerkidwell, via https://pixabay.com/en/turtle-ocean-blue-sea-underwater-287973/.

The Earth may not be our Solar System’s only blue planet, but the physics of its blueness is unique! Find out the full story on Forbes today.

Comments

  1. #1 Dan Milton
    March 4, 2016

    Why do I get and endless loop of Forbes welcome pages?
    Please make content accessible somehow.

  2. #2 Michael Kelsey
    SLAC National Accelerator Laboratory
    March 4, 2016

    @Dan Milton #1: Do you have your browser configured to disallow cookies? The Forbes site (which Ethan has no control over whatsoever) Is set up to block users who are using AdBlock plug-ins.

    It saves a cookie in your browser once it has determined that you aren’t blocking their ads. If you don’t allow cookies you won’t get past that (and, once you do get past it, you can turn AdBlock back on!).

  3. #3 Wow
    March 5, 2016

    But by then, if there’s malware in their ads, you’re infected. So all you;re doing with adblocking after the first visit is removing the adverts that “pay” for the “content”. Most of the other non-selfish reasons for blocking ads such as protection of your computer are gone.About all you’re doing is saving everyone some wasted bandwidth sending ads you’re completely and 100% uninterested in.

    Which the advertiser doesn’t give a shit about.

    If Forbes won’t let you in without adblock, don’t go. See how well they “monetise” when nobody is looking. They’ll find out you can’t eat adverts, and you can’t pay the rent with them.

  4. #4 Wow
    March 5, 2016

    Dan, it DOES appear in Ethan’s medium.com area a few days later (like about a week).

    If you’re not interested in reading it a week later, it wasn’t all that necessary to read it in the first place, was it?

  5. #5 Dan Milton
    March 6, 2016

    Thanks, all.
    Unblocking seems to do it, and I guess it doesn’t hurt to be offered hotel discounts in places I’ll probably never go to.

  6. #6 Brian
    CA
    March 6, 2016

    So WOW is back and still a douche. It was nice while it lasted, wasn’t it? Imagine, people discussing physics without some loser talking down to everyone as if he thinks he’s on Xbox Live.

    Don’t worry though. We all know he’d never say any of these things to someone’s face. Take for instance the whiny comment he’s about to make in response to THIS comment. He can only say that from the safety of his computer. That’s what we call a “pussy”.

  7. #7 Wow
    March 7, 2016

    So brian is still a whiney little brat with nothing to offer.

    It was nice when the little cockstain was silent and let their betters talk, but such idiocy cannot remain silent for long.

  8. #8 Wow
    March 7, 2016

    Weird, though, how brian whines on the thread where I’ve posted helpful comment. Not others where I’ve given all *due* respect to the morons posting.

  9. #9 Brian
    CA
    March 7, 2016

    Wow, NO ONE likes you on this message board. And you know it. And since you love saying things anonymously from behind your computer, let’s cut the BS. Post a link to your Facebook page. (You and I both know that you won’t because a complete fucking pussy)

    You won’t post the link. Instead you’ll call me some more names and give me excuses as to why you won’t do it. Like I said…you’re a complete pussy.

  10. #10 Brian
    March 7, 2016

    And I love the whole “everyone on here is a moron” comment. Yeah, believe that. Everyone ELSE is stupid and you’re right, huh pussy? I’m sure you’re a real hit with the ladies.

  11. #11 Wow
    March 7, 2016

    Whine whine bitch moan.

    Do you do ANYTHING constructive, bri?

    Or do you just whine about those who do?

  12. #12 Wow
    March 7, 2016

    Did you take a poll, bri? How many people are on this message board and how long did it take you to contact them all (And where’s their list, I want to see if they like you at all).

    Or are you talking bollocks again?

  13. #13 Wow
    March 7, 2016

    Hey, bri, if s a top isn’t a moron, maybe you can explain what his proofs mean.

  14. #14 Brian
    March 7, 2016

    Yup. Didn’t think you’d provide your Facebook link. Better to stay anonymous, huh? What a complete fucking pussy.

  15. #15 Wow
    March 7, 2016

    Blah blah blah, bri.

    So, no, you don’t have anything productive to add, only a whinge at your betters.

    INTERNET ALERT! BRIAN IS A HARD MAN. HE CALLS SOMEONE A PUSSY ON THE INTERNET.

    APPROACH WITH EXTREME CAUTION IN CYBERSPACE!

    CONSIDERED ARMED AND DIPSHIT.

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