• Question: Can you approximately guess the mph form of light speed?

    Asked by Mia Burns to Hannah, Lucy, Phil, rochellevelho, Stephen on 14 Mar 2017.
    • Photo: Phil Sutton

      Phil Sutton answered on 14 Mar 2017:

      One way it was discovered that light has a finite speed was by watching Jupiter’s moons. I we watch Jupiter’s moons eclipse Jupiter throughout the year the timing of these changes away from the predicted times. When the Earth and Jupiter are far apart the lag time is greater. This lag can be used to work out the speed of light as we know the actual distances to the planets.

    • Photo: Hannah Sargeant

      Hannah Sargeant answered on 14 Mar 2017:

      670000000 mph! That means that light takes 8 minutes to get from the Sun to the Earth, which is very fast indeed!

    • Photo: Lucy Kissick

      Lucy Kissick answered on 14 Mar 2017:

      Hannah got there before me, it is indeed 670,000,000 mph. Considering the fastest moving object ever made by humans is 90,000 mph (NASA’s Juno spacecraft, now at Jupiter), you get the idea of how unbelievably fast this is.

    • Photo: Stephen Pulker

      Stephen Pulker answered on 15 Mar 2017:

      You don’t need to guess, a quick Google search will give you a very good answer . . . the speed of light is quite precisely known . . .
      299,792,458 m/s
      . . . which is equal to . . .
      670,616,629.3844 mph

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