• whotookkarl@lemmy.dbzer0.com
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      8 hours ago

      When sailing boats pushed for speed they ended up hitting an unexpected speed barrier. As you increase velocity the break wave created by the bow of the ship elongates until the length of the ship is at 1 wavelength, then the hull drag prevents further acceleration. For a 50 meter ship it’s about 17 knots. You can get much faster lifting the boat from the water as you gain speed with an underwater wing, the current max speed was set 47 years ago at ~276 knots. But that’s only because they can remove the hull from the high drag environment and is extremely dangerous to attempt to break. The speed of light is nothing like that because spacetime itself can stretch and squish, I just wanted to talk about boats for a bit.

    • FuglyDuck@lemmy.world
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      9 hours ago

      You have two observers, moving directly opposite each other.

      Each has a flashlight pointing back at the other.

      The speed of the light from those torched is the same for both observers.

      (Instead the light would be red-shifted.)

      Add a third observer, stationary to one and moving towards the other. As the third observer passes that observer, the speed of light from their flashlight never changes, and it’s the same speed as from the other two. (Instead it would go from being blue shifted to red shifted.)