Deep ocean sediment cores, drawn from the Atlantic, Indian and Pacific oceans, are said to show a heartbeat of the Earth's ecosystem, a 100,000 year (100ka) cycle of eccentricity that is modulated and amplified by smaller cycles of recession (23ka) and obliquity (41ka). That is the consensus view – earth's orbit around the sun is elliptical in shape rather than strictly circular. Over time the the shape of the orbit changes from elliptical to less so. The greater the eccentricity the more pronounced will be the difference in solar radiation receipt – affecting summer/ winter contrasts. The periodicity, the time taken for the orbit to change from one point of greater eccentricity to the next is around 100ka although some variation is apparent with cycles of 95ka and 123ka also recognised. It is interesting to note that only eccentricity will affect the total amount of solar radiation rreceived by the earth – the other variables redistribute that energy at different latitudes. However, each will exert an affect on the others – and it is these minor changes in earth's orbit that are said to drive the Ice Ages. For example, accentricity at its farthest point is more distant from the sun than at other points in the orbit of the earth. What is peculiar, in some respects, is that warming episodes, the intervening inter-glacials, are shortlived, between 10ka and 20ka.
Now, it just happens this is all remarkably similar to the cycle of the sun around its barycentre as perceived by Rhodes Fairbridge (see Richard Mackey, 'Rhodes Fairbridge and the Idea that the Solar System regulates earth's climate' in the Journal of Coastal Research 50 (Canberra, 2007) – see www.griffith.edu.au/conference/ics2007/pdf/ICS176.pdf or http://jennifermarohasy.com/2007/08/rhodes-fairbridge-and-the-idea-that-… Isaac Newton, in 1687, showed that the sun is engages in continual motion around the centre of mass in the solar system, the barycentre. This is as a result of gravitational forces exerted by the planets, especially the big ones such as Jupiter, Saturn and Neptune. Newton came to this conclusion not by observation but by working through the consequences of his Law of Gravitation. The sun, in effect, is in free fall around the barycentre, and whilst the barycentre is mostly within the circumference of the sun itself when too many planets line up on one side the barycentre will shift outside the sun in order to maintain equilibrium. Fairbridge assumed gravity is the driving force of the solar system and found a cycle of 93,400 years – which is not too far from the cycle of eccentricity in the consensus model. So what is the heartbeat of the of the earth? Is it eccentricity or does the cycle of the sun around the barycentre have an effect on life on earth, even in the oceans?
Rhodes Fairbridge did not see the two things as incompatible and was supportive of the Milankovitch theory. He visualised eccentricity and the orbit of the sun around the barycentre as mutually supportive.