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During the summer solstice that occurred last month, the northern hemisphere tilted towards the sun and was exposed to sunlight longer than any other day of the year.
] The solstice occurs because the Earth is housed at an angle of 23.5 degrees on an inclined axis. This obliquity of the ecliptic has long led astronomers to wonder if the inclination of the Earth has helped create the conditions necessary for life.
This is an issue that has been brought to the forefront of research while scientists have discovered thousands of exoplanets orbiting other stars in our galaxy, bringing them closer to each other. Earth 2.0
Astronomers suspect that the axial inclination of these exoplanets varies considerably, as happens in our solar system, with mercury leaning 0.03 degrees and Uranus at 82.23 degrees. These are two extremes, far from being livable, even though these worlds look like other aspects of the Earth, said René Heller, astronomer at the Max Planck Institute for Solar System Research in Germany.
The tilt of exoplanets can vary considerably, just as in our own solar system. An artistic representation (European Southern Observatory.)
If the planet had no obliquity, it would have no seasons. The hemispheres would never have an ascent or a decline relative to its star. The poles would be so cold that the carbon dioxide would be extracted from the sky, an effect that, according to Heller, would make the planet lose its precious greenhouse gas, so that the liquid water would never form [19659009]. For its part, life could also be complicated. There, one pole points directly to the host star and the other not, which would make a hemisphere be bathed in the sun day and night during this long summer, while the other hemisphere would have a cold, dark winter – before the stations were reversed. Even if such a planet does not lose liquid water on its surface, all life should adapt to a world that permanently alternates between porridge and jelly.
Heller estimates that the optimal axial inclination is between 10 and 40 degrees. There are several conditions that must exist to allow life, and the slight obliquity of the Earth is one of them.
Rory Barnes, astronomer at the University of Washington, does not agree. "The 23.5 degrees are nothing special," he said. "It could have any obliquity and still have habitable conditions."
The detail is that such a planet should have a dense atmosphere that could transfer heat to these icy regions.
David Ferreira, oceanographer at the University of Reading, England, and others found in 2014 that a 2.0 Earth even with an obliquity like Uranus could support life, if it had a global ocean. An ocean would absorb heat during the summer and release it in winter, allowing the planet to stay relatively warm.
© The New York Times, 1965, p.
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