The speed of light is relatively great

A crucial fact underpinning the illusions created by vision is that c is enormous relative to speeds ordinarily encountered by humans: light travels over a hundred million times faster than a car moving at a hundred kilometres an hour. This is why humans have developed a sense of time which deceives us into believing that we see events as they happen: in ordinary human terms the speed of light is effectively infinite. This contributes to the conditioning that things are just happening ‘out there’ and that we can know all about them right there and then as they happen. This underpins the notion of simultaneity that classical mechanics (CM) has built into its foundations.

Thunderstorms remind us, however, that the speed of transition of signals is a crucial factor in our mental images: there is usually a delay of several seconds between us first seeing a lighting strike and then hearing the accompanying thunder. Light travels close to a million times faster than sound in Earth’s atmosphere.

If light took several seconds to reach us from nearby objects, our conditioned view of time would probably have evolved to be very different to the one we have now. We experience something like this when we are in a dense fog: our perceptions then become dominated by sounds and touch rather than vision. Under such circumstances, when delays become significant, our sense of time can appear distorted and we no longer have the immediacy of vision.

On rare occasions, we may be reminded that the speed of light is relatively enormous compared to the speed of sound. The author once saw a farmer driving a fence-post into the ground with a large hammer, the farmer being on the other side of a valley. The sound of the hammer blows was heard halfway between the sight of the hammer hitting the post, creating an illusion that the sound was being generated by the hammer hitting the air above the farmer’s head.

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