The Reality Frame: Relativity and Our Place in the Universe by Brian Clegg

Author:Brian Clegg [Clegg, Brian]
Language: eng
Format: epub
ISBN: 9781785782084
Amazon: 1785782088
Barnesnoble: 1785782088
Goodreads: 31921735
Publisher: Icon Books Ltd
Published: 0101-01-01T00:00:00+00:00

Whatever Newton believed God’s role to be – and he added a short section to the end of the Principia where he emphasised that the wonder of nature should be taken to imply the existence of God – he did not believe that the deity was in favour of action at a distance. The attacks Newton received from the likes of Leibniz and Huygens must have stung, particularly because Newton did not believe in action at a distance either. Like many of his contemporaries, he thought that there must be some kind of material in space, an ‘aetherial medium’ or ether that played the same role in transmitting the attractive force of gravity as the air did in carrying sound to the ear. This ether was harder to detect than the effects of air, but Newton believed it surely must be there.

The difficulty was that it’s much easier to use an intervening medium to send a push than it is to transmit a pull. Although various scientists and mathematicians would play with concepts like vortices in the ether that could provide that ‘pull’ effect, none was particularly satisfactory. As time went on and still no way of detecting a mechanism for gravity to work had been discovered, the ether was replaced by another mechanical approach that Newton had also considered as a possibility, though in a cruder form. This involved a universal bombardment of invisible particles, and variants of this particle shower theory would remain popular all the way up to the end of the nineteenth century, when William Thomson, Lord Kelvin, would be one of its last physicist supporters.

It goes something like this. Imagine that the universe is full of flows of invisible particles that are able to put pressure on the bodies they encounter. These particles act on massive bodies, but do not act on each other. (If this seems extremely unlikely now we know it is unnecessary, bear in mind that this is not dissimilar to the quantum theory of light, which acts on matter, but not on itself.) Now think what would happen to the flow of these particles coming, for instance, towards the Moon. From most directions, the particles would be coming in the same quantities and would cancel each other out, producing no net effect. But from the direction of the Earth, the Moon is in the Earth’s particle shadow. The Moon will receive fewer particles from that direction. The result would be that the Moon feels a force that pushes it towards the Earth.

There has to be more to the theory than the simple description I have given, or gravitational pull would depend on the size of a body rather than its mass, and plenty of explanations for this variation were provided. But the theory does produce an inverse square law and, as such, it’s not a bad start for an attempt to provide an explanatory mechanism for the attractive force of gravity. As we’ve seen, variants of this theory lasted for over

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