Venus, the sister planet. Similar dimensions to those of the Earth, the same favourable position (in relation to the Sun) for the development of life. Two worlds apparently identical with a single, substantial difference: while our planet maintained over the millennia the conditions necessary for the biological processes, Venus has irrecoverably lost them. Scientists are questioning since decades on how this might have happened. The fact is that the second planet of the solar system has become a hostile environment, uninhabitable. A hellish world, hot (even more than Mercury which is located closer to our star), with a poisonous atmosphere due to the large presence of carbon dioxide and to the frequent rains of sulfuric acid. From eons Venus coexists, in fact, with a terrible greenhouse effect which keeps the temperature constant, preventing the dispersion of heat.
The alarm of Hawking
A destiny that, due to the effect of the action of man, one day might also concern the Earth. The known astrophysicist Stephen Hawking is convinced about it. Criticising the United States’ withdrawal from Cop21 in Paris wanted by Donald Trump, he stated: “We are close to the point of no return where global warming will become an irreversible process. The choice of Trump could push the Earth beyond this margin and make it become like Venus with temperatures of 250 degrees and rains of sulfuric acid”. For the scholar of the cosmos, interviewed by the BBC, “Climate change is one of the greatest dangers we face and if we want to stop it we must do it now. Denying the evidence of the existence of climate change and by withdrawing the USA from the Paris Agreement, Trump will cause environmental damage that are avoidable to our magnificent planet, putting nature in danger for us and our children“.
In fact, the possibility of an irreversible greenhouse effect is one of the scenarios to which scholars more often refer to when they are being asked to assume in what way the world we know (at least from the point of view of life) will cease to exist. But this is not the only one. In addition to the causes arising from the work of man, in fact, in the next centuries natural catastrophes may occur such as to compromise our existence on earth.
NASA has recently discovered near our planet 97 objects that were unknown. 10 of them have been defined as “Potentially Hazardous Objects” (Pho). Their size is such that any impact with the terrestrial ground or with the oceans might lead us to the same fate of the dinosaurs. The conditions in which we would be after the explosion would be those of a nuclear winter, with the dust raised that would prevent sunlight to reach us. The first ones to die would be the plants, then herbivores, carnivores, and finally man. The US space agency, after having spread the news invited people to remain calm: the fall of one of these killer meteorites in the next 100 years is judged as “unlikely“, while it will be “inevitable” in a longer period. In the meantime, we could however have developed advanced systems to defend ourselves. Nasa is developing “kamikaze” satellites (called Dart) that, in the event of danger, would be launched at full speed against the asteroids on a collision course with the Earth with the aim of changing their trajectory, thus preventing the apocalypse.
The Sleeping Giant
A similar scenario to the one caused by a killer asteroid could occur where the volcano of Yellowstone decides to wake up. Buried under the great American natural park, it extends for over 90 km and reaches a depth of approximately 14 km. It erupts approximately every 700 thousand years and the last phenomenon happened 640 thousand years ago. This means that the sleeping giant should leave us in peace for at least 60 thousand years. Yet in recent days American institutes of volcanology have recorded a seismic swarm of 878 earthquakes in the area, such as to generate alarm in the population. Experts argue however that similar episodes (even more powerful) have already occurred in 2002, 2004, 2006, 2008 and 2010. Therefore, there will not be an imminent awakening. And it is a good thing, because if the last eruption generated a quantity of powders such as to obscure the sky of North America, the next could have “devastating consequences that would harm the whole world” and “would affect the fate of the climate“.
The ray of the death
You write Wr 104 but it reads “time-bomb“. This is a giant star (about twenty times the sun) positioned in the constellation of the Sagittarius, 8 thousand light years from us. A distance that may seem sidereal but which in reality would not be sufficient to protect us in the moment in which the celestial body decides to explode. The consequent supernova will produce a powerful gamma ray, i.e. a series of electromagnetic radiations at very high energy which may last from a few milliseconds to tens of minutes. The optical effect can be astounding (in the sky for a few moments you will see another sun) while the actual one will be terrifying. According to some studies a gamma flash striking the earth from that distance would wipe away about 25% of the atmosphere, with catastrophic consequences on life. Some scientists argue that the mass extinction of the Ordoviciano-Siluriano (450 million years ago) that made the 85% of life on our planet disappear, has been caused precisely by one of these shocks. The problem of supernovae is that they cannot be accurately foreseen. And there is more: considering the time that the light takes to reach us from that distance, it is possible (although unlikely) that this explosion has already occurred.
So far, we have analysed the most plausible hypotheses of an early termination of the world. But there are others, albeit very remote, that the astrophysics scholars have theorized. Like the one which would result from the impact with an interstellar planet, i.e. a celestial body, similar to those that orbit around a star, intended to wander for eternity. According to the researchers the collisions between worlds would have already happened. One of the most suggestive theories supports, for example, that the moon would have been originated from debris generated by the clash between the earth and a planet similar to Mars. In the event of a collision with a celestial body large enough, among other things, own world could be the one to be transformed.
The most probable hypothesis
Physics has not yet developed so much as to enable us to understand how and when our planet will live the last hour. The most likely fate will be the absorption by the sun in approximately 5-7.5 billion years after that the star will enter in the phase red giant and will expand until crossing the orbit.