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  1. NTW

    Ground return used for early telegraph?

    I have read that, in the early days of the telegraph, two wires were used, but Steinheil, of optics fame, discovered that the circuit could be completed by 'earth return', using the ground as return ...conductor? That's my question. It's hard to believe that currents strong enough to operate...
  2. NTW

    Moving feathers

    A small movement of the external part of the feathers can be appreciated In minute 2:56 of this documentary: . What could be the cause? Perhaps the residual atmosphere?
  3. NTW

    Do black holes vanish ?

    As I understand it, the Hawking radiation is produced when a pair particle-antiparticle are produced at a place close to the event horizon of a black hole, so that one of them, energy-negative for a distant observer, is swallowed by the hole, and the other appears as 'black hole radiation'. I...
  4. NTW

    Lift-dependent drag estimation

    I'm no engineer, but just a pilot trying to estimate the drag of my small two-place airplane from the relevant formulae. My plane is quite draggy, and from comparison with other aircraft data, I have taken Cd,0 as 0.043. Apart from this, I calculate the induced drag at a given speed from the...
  5. NTW

    Endurance & maximum range speeds

    Hello all... I know that it can be derived, from first principles, that maximum endurance and maximum range speeds are related by the factor 3^0,25. But I haven't been able to find a derivation. Could anyone here help...? Thanks in advance...
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