• ilinamorato@lemmy.worldEnglish
    6·
    1 hour ago

    If the sticker is blue, one or the other of you is about to cease being biology and start being physics.

  • Sharlot@lemmy.worldEnglish
    6·
    3 hours ago

    Best kind of science joke: funny and educational. Bonus points for making people think about Doppler before speeding.

  • glorkon@lemmy.worldEnglish
    281·
    8 hours ago

    Even then, a BMW would tailgate and flash its headlights at you on a German autobahn.

  • RiceMunk@sopuli.xyzEnglish
    46·
    9 hours ago

    Exercise for the reader: Assuming average human eyesight, how many picoseconds away from a collision are you if you can read that size of text and the relative velocity between you and the car ahead of you is large enough that the red label is sufficiently blueshifted to look blue?

    • Zkuld@lemmy.worldEnglish
      44·
      8 hours ago

      for 800nm to 400nm, we need gamma=2. So v~.86c. At 20m this gives you ~80ns.

      • moriquende@lemmy.worldEnglish
        21·
        7 hours ago

        For perspective, this speed is:

        • 928 157 450 kilometers per hour
        • 576 730 301 miles per hour

        In one second, you would travel around:

        • 258 000 kilometers
        • 160 000 miles

        Which is around 6.43 times around the Earth’s equator.

    • glorkon@lemmy.worldEnglish
      15·
      8 hours ago

      The sticker should also say something like “But don’t worry, we’re going to be evaporated in a huge explosion anyway, due to the gigantic release of energy when you crash into my car in a few nanoseconds.”

    • spicy pancake@lemmy.zipEnglish
      2·
      8 hours ago

      does the observer have to be able to see the sticker with normal human eyesight? if so that constrains distance (which maybe doesn’t matter?)

  • glorkon@lemmy.worldEnglish
    59·
    11 hours ago

    Clever, I like it. I wonder how many people read it and have no clue what it means.

    • three@lemmy.zipEnglish
      29·
      3 hours ago

      Only us top-tier, special, educated, and privileged people get this hilarious joke! Do you know the answer?

      Clickbait f*cebook-ass post

  • ChaoticNeutralCzech@feddit.orgEnglish
    2·
    5 hours ago

    The color also depends on the ink’s near-infrared reflectivity (since the sun and halogen headlamps emit infrared, that will get shifted into the red to green parts of the visible spectrum when red becomes blue)

      • Mr_Dr_Oink@lemmy.worldEnglish
        2·
        6 hours ago

        Right, thanks for the explaination…

        Incidentally, my limited understanding and 5 seconds of research tells me the blueshift and redshift are directly related. One is linked to lower speeds and one to higher speeds. The sticker itself is red, so the joke is saying you must be travelling at some fraction of the speed of light to see the sticker as red and if you were going slower it would appear blue.

        So it would seem to me in my very limited understanding that this is in fact, to do with redshift…

        • ulterno@programming.devEnglish
          2·
          4 hours ago

          I was trying to be funny, but the 2 are related as in they are opposite cases of the same underlying phenomenon.

          The sticker itself is red, so the joke is saying you must be travelling at some fraction of the speed of light to see the sticker as red and if you were going slower it would appear blue.

          I’m not sure if you actually understand it and just did a brainfart while typing, or actually don’t understand it well, so I’ll just explain…

          • In both cases (redshift and blueshift), you need to be going fast enough relative to the sticker for either of them to happen in any noticeable way. Although it still happens even if you are going only 1 cm/s
          • The sticker is red and you will see it being red if you are not moving relative to the sticker. i.e. if the car is parked and you are just standing behind it, it will be red (don’t take my word for it. Go stand in front of a red thing and look at it to find out that you see red colour)
          • If you are going away from the sticker, you will observe a redshift. And since the sticker is red (let’s assume for simplicity that it is the reddest of red (whatever that would mean)) the redshift will make it go infrared and hence you won’t be able to see it with human vision.
          • If you are going towards the sticker, you will observe a blue shift and you can use the crude, but useful VIBGYOR to deduce that if you are not fast enough to see Blue, you can expect to see either of Orange, Yellow, Green.
          • This effect is similar to the phenomenon that occurs to sound. i.e. when a car comes towards you with the horn continuously blowing, you will hear a higher pitch and when the car with the horn blowing is going away from you, you hear a lower pitched horn sound. The reason this is more easily observable with sound, is because sound in air is slow enough for us to notice this.

          Bonus: I was playing the game X4: Foundations and realised that they actually have simulated this effect in the in-game sounds, which was an impressive little detail and I loved it.