Matthews introduces the new studies that indicate that planets orbiting the sun have an affect the Earth:
At its heart is a curious coincidence noted by astronomers more than 150 years ago. If the number of sunspots appearing on the disk of our nearest star are plotted over time, they follow a distinct pattern, rising and falling over a period of about 11 years.
This is curiously close to the 11.9 years that it takes Jupiter, the biggest planet in the solar system, to complete one orbit of the Sun.
It is always hard to know what to make of such “coincidences”; all too often they prove to be the product of nothing more than random chance.
But in 1852, the Swiss astronomer Johann Wolf showed that despite its great distance, Jupiter has more gravitational effect on the Sun than any other planet. He went on to develop a theory that seemed to account for sunspot numbers via the influence of Jupiter and other planets.
As sunspots are a symptom of solar activity, and this in turn directly affects the Earth, Wolf’s ideas sound uncomfortably close to astrology.
This doubtless explains why the notion of planetary influence on the Sun was hastily dumped at the start of the 20th century, following the discovery of a link between sunspots and the solar magnetic field.
Clearly, there could be no connection between the gravity of the planets and the magnetic field of the Sun. But now a team led by Dr José Abreu, of the ETH Zurich Institute for Geophysics in Switzerland, has rekindled the controversy with impressive evidence for precisely such a link.
To make their case, the team has examined records of solar activity far more extensive than those used by Wolf, who could only go back as far as the mid-17th century, and the first telescopic observations of sunspots by Galileo.
Dr Abreu and his colleagues have exploited the fact that changes in the sun’s magnetic field affect the levels of cosmic rays smashing into the Earth’s atmosphere – which in turn create isotopes that get trapped in polar ice and tree rings.
By analysing the rise and fall in levels of these isotopes, the team has managed to reconstruct the peaks and troughs in solar activity covering more than 9,000 years.
Armed with so much data, they have been able to look for patterns in the activity far more subtle than those found by Wolf. And what they have found broadly confirms his idea of a planetary influence on the Sun.
Publishing their findings in the current issue of the journal Astronomy & Astrophysics, the team stresses that the planets cannot be the prime driver for the 11-year cycle of solar activity.
If that were so, the orbits of the planets would change noticeably through the energy needed to drive the activity. But the planets can and do seem capable of affecting the processes that generate the Sun’s magnetic field.