Future of Earth: Death of the Sun, Ice Age & Deadly Warming
The long-term destiny of planet Earth is difficult to predict: according to scientific models, it is doomed to go up in smoke or, on the contrary, will see its oceans frozen ...
The inevitable death of the Sun precipitates that of the Earth
Born 4.6 billion years ago from a cloud of gas, dust and ice crystals, the solar system of which the Earth is a part will not last forever. Within 5 to 7 billion years, the Sun will have exhausted its fuel, hydrogen. The pressure and the temperature increasing in its center, it will follow an extraordinary and very fast dilation of its gaseous envelope: our sun will then become a star known as a red giant. Its outer layers will have cooled, but will have expanded enough to encompass and consume Planet Earth. Heat will have already killed all forms of life in some 3.5 billion years.
No longer able to maintain a thermonuclear reaction, the Sun will eventually collapse on itself. Transformed into another type of star called white dwarf, no bigger than Earth, the Sun will become as cold as the planets orbiting around it.
A new ice age
Recent simulations also suggest a completely different fate. It is thus possible that one of the planets of our solar system will be attracted by the passage of a star which would modify its orbit accordingly. However, if Jupiter slightly changed its orbit, the Earth would risk being ejected into space or, on the contrary, rushing towards the Sun. In the first case, life could continue to exist near hydrothermal vents, in the deep ocean floor. The oceans, in fact, would not turn into ice until after a million years.
Unfortunately, there is only one chance in 100,000 that such an event will occur in the next 3.5 billion years ...
Or a deadly warming?
In contrast, rising temperatures could lead to the complete disappearance of the oceans in a billion years "only". Earth's troubles could even start 500 million years earlier, due to a drop in the level of carbon dioxide (CO2) in the atmosphere. With the help of heat, carbonates (minerals that are formed from CO2) would precipitate more easily in water, thereby pumping more carbon dioxide. And, in 500 million years, the available carbon would run out: forests and crops could no longer carry out their photosynthesis. Some tropical plants would manage to survive, but without being sufficient to feed the biosphere.
As for the current greenhouse effect, which contributes to maintaining an average “livable” temperature on Earth, it would only give our descendants a reprieve of a few million years …
What if the Earth stopped spinning?
Another catastrophic scenario! There is indeed a gradual slowing down of the speed of rotation of the Earth, which several mechanisms try to explain. Thus, the friction between the nucleus and the Earth's mantle changes the speed of rotation of the planet. When this friction becomes very strong, the planet could find itself irreparably blocked. However, this phenomenon is still poorly quantified.
However, it has been calculated that the Earth takes to spin on itself 2 thousandths of a second less per century! Thus, at the beginning of the carboniferous, 350 million years ago, a year counted 400 days of 22 hours. We are currently experiencing years of 365 days of 24 hours. In a billion years, the day will last almost 30 hours and the year will have 290 days. On the other hand, we do know the influence of the tides. On Earth, they result in a maximum water level in the area facing the Moon and in that which is diametrically opposite, particularly important when the Earth, the Moon and the Sun are aligned. To a lesser extent, the tides also act on the earth's crust and the atmosphere. They form beads which create a couple of recall slowing down the rotation of our planet, while moving the Moon away: the Earth-Moon distance thus increases by a few centimeters per year, and the Moon would eventually escape from Earth's attraction.
Or if Planet Earth tipped over?
Losing its satellite, turning less and less quickly, the Earth also risks tipping over ... The obliquity of the Earth - the inclination of the plane of the equator relative to the orbital plane - varies continuously under the influence of various factors. Currently, this obliquity is 23.3 degrees and undergoes, over a period of approximately 41,000 years, small variations of 1.3 degrees. Although weak, these are enough to cause variations of almost 20% of insolation, in other words the amount of energy received from the Sun, and could explain the ice ages experienced by the Quaternary era (the some last 2 million years). In general, it is this obliquity that is the origin of the seasons.
Also, the factors that slow down the rotation of the Earth could have the consequence of tilting it at a much greater angle than today, with two extreme possibilities: a Earth blocked either at zero obliquity (with the axis of the poles perpendicular to the orbital plane) or, on the contrary, equal to 180 degrees (with the axis of the poles in the orbital plane). Result: literally, there would be no more seasons ...
