Gravity of Jupiter and Venus elongates Earth’s orbit every 405,000 years – study 

Arizona, USA

Amazing what can be gleaned from a 1,700 feet long rock core.
H/T Ian Wilson

Every 405,000 years, gravitational tugs from Jupiter and Venus slightly elongate Earth’s orbit, an amazingly consistent pattern that has influenced our planet’s climate for at least 215 million years and allows scientists to more precisely date geological events like the spread of dinosaurs, according to a Rutgers-led study.

The findings are published online today in the Proceedings of the National Academy of Sciences, reports ScienceDaily.

“It’s an astonishing result because this long cycle, which had been predicted from planetary motions through about 50 million years ago, has been confirmed through at least 215 million years ago,” said lead author Dennis V. Kent, a Board of Governors professor in the Department of Earth and Planetary Sciences at Rutgers University-New Brunswick.

“Scientists can now link changes in the climate, environment, dinosaurs, mammals and fossils around the world to this 405,000-year cycle in a very precise way.”

The scientists linked reversals in the Earth’s magnetic field — when compasses point south instead of north and vice versa — to sediments with and without zircons (minerals with uranium that allow radioactive dating) as well as to climate cycles.

“The climate cycles are directly related to how the Earth orbits the sun and slight variations in sunlight reaching Earth lead to climate and ecological changes,” said Kent, who studies Earth’s magnetic field. “The Earth’s orbit changes from close to perfectly circular to about 5 percent elongated especially every 405,000 years.”

The scientists studied the long-term record of reversals in the Earth’s magnetic field in sediments in the Newark basin, a prehistoric lake that spanned most of New Jersey, and in sediments with volcanic detritus including zircons in the Chinle Formation in Petrified Forest National Park in Arizona.

They collected a core of rock from the Triassic Period, some 202 million to 253 million years ago. The core is 2.5 inches in diameter and about 1,700 feet long, Kent said.

The results showed that the 405,000-year cycle is the most regular astronomical pattern linked to the Earth’s annual turn around the sun, he said.

Continued here.