From Antony Naylor
In the concept proposed by Marcus Chown in the article “All the world’s a hologram” (17 January, p 24), the two-dimensional surface of the sphere surrounding the universe is the hologram and the universe (including you) is a holographic image – a point glossed over by the oversimplified wording that appeared on the cover of the issue.
There are two main problems with this theory. First, if there is a projected image, then some energy must interact with the hologram, either as transmitted or reflected energy. This cannot be electromagnetic radiation as its finite velocity would raise all sorts of problems with time, including predestination. So what is it and where does it come from?
Secondly, if the universe is expanding then the elements of the hologram must either be increasing in number or be being stretched. In the case of a black hole, the event horizon does increase in size as energy falls in, but there is no evidence that energy is falling into the universe. If the elements are being stretched, the graininess of the universe must be increasing.
These issues can be resolved if one accepts that while the elements in the universe and those on the surface of the sphere can be mapped or transformed onto each other, neither the elements inside nor those on the surface create each other. This concept still leaves the universe with graininess at a scale of around 10-16 metres – compared with the Planck length of 10-35 metres on the surface – but it does raise questions about the change in graininess as the universe has expanded, assuming the Planck length has always been the same.
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Wasaga Beach, Ontario, Canada
