OK, thanks to both of you. My key misunderstanding was this: I thought
that they were claiming to see the photons which were moving in a
straight line through the medium. Instead, they are seeing the portion
of those photos which are being scattered to the sides at each point
within the medium.


On Sun, Dec 18, 2011 at 8:47 PM, IVP <joecolquitt@clear.net.nz> wrote:
>> Any idea what exactly is going on in that photo?
>
> My take on it, based on the explanation in the video, is that
> it's similar to the technique used in high-speed oscilloscopes,
> where the display is not of a single event, but an assemblage
> of samples of a repetive and predictable waveform
>
> So the light 'moving' across the screen is not made up of just
> one pulse of photons, but is a movie of a series of pulses captured
> by the camera, their positions being reflected to it by tilting the
> mirror. But in effect, as they are all identical, it might as well be
> the same photons
>
> Similar to how lower-speed strobes can capture water droplets
> in a stream or freeze cartwheels in old cowboy films
>
> This page is more helpful
>
> http://www.tested.com/news/mit-photographs-light-at-one-trillion-frames-p=
er-second-video/3278/
>
> "Finally, our algorithm uses this captured data to compose a single 2D
> movie of roughly 480 frames, each with an effective exposure time of
> 1.71 picoseconds"
>
> Photons travel at 300,000,000,000,000,000 pm/s, implying that an
> individual photon will have moved about 0.5mm in the exposure time,
> which is seriously blurred. But an impressive technical feat nonethless
>
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