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Gravity Speed of Light

16 December 2017

Jovan has sent in a lot of links this week. Here are two of them. At http://blogs.discovermagazine.com/d-brief/2017/12/08/speed-of-gravity-li… …. why does gravity travel at the speed of light. This idea is derived from the recent gravitational waves generated from a collision of two stars, 130 million years of age – in a far away galaxy. They reached the Earth in August 2017. These were neutron stars and the collision caused a gravitational wave – but gravity appears to have traveled at the same speed as light emitted from the same collision. Apparently, electromagnetism, when you shake an electron it creates a change in the electric field that spreads out with the speed of light. Gravity works the same way, shake a mass and the change in the gravitational field (the gravitational wave propagates at the same speed of light.

At http://blogs.discovermagazine.com/crux/2017/12/13/asteroid-geminid-meteo… … the asteroid named Phaeton, after the Greek god of the same name, is the origin of the meteor shower we all know as the Geminids. At peak shower there is a shooting star every minute. The asteroid '3200 Phaethon' is the progenitor of the Geminids but how did an asteroid rather than a comet emit a trail of debris. Its orbit is like a comet as it is elliptical but it is definitely no dirty snowball. What is the reason? Scientists hope to find ouot this year as telescopes are trained on Phaethon as it comes relatively close to Earth on its travels. Clube and Napier in their books 'The Cosmic Serpent' and 'The Cosmic Winter' did have something to say about Phaethon, namely the progeny of Zeus with a handle that means 'blazing star' in the vernacular. The asteroid Phaethon was named unwittingly after the Phaethon of mytholgy – that came so close to the Earth it threatened to set the world alight. They suggested the asteroid Hephaistos was once part of Comet Encke, separatomh from each other thousands of years ago, and the asteroid Oljato was another one that had fragmented from a bigger body more recently. Oljato, they said had come very close to the Earth between 3500 and 3000BC – at a time it may have been an active volcano. In other words, they saw no reason why an asteroid cannot be a dead or outgassed comet – and the same might apply to Phaethon. This implies Phaethon was active in the last couple of thousand of years in order for it to still produce a fairly active meteor shower (it has not had time to dilate and spread into a wider and less active trail of material). 

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