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The Earth is the only planet known to be inhabited by life and is among the few with ideal conditions for life to flourish. Therefore, the Earth is quite special, and its protection is paramount to all species which inhabit the planet Earth. However, there are several natural factors which have been identified by scientists as likely causes for the destruction of the Earth and humanity, with man鈥檚 intervention to avert them from happening being limited. These factors are also known as the non-anthropogenic causes of a global catastrophe.

Impact Event

An impact event is the falling of extraterrestrial objects on the Earth鈥檚 surface which usually results in a range of physical effects. The extraterrestrial objects range in size from tiny meteoroids to huge asteroids which can be several miles in diameter. While most of the energy from these astronomical objects is absorbed by the Earth鈥檚 atmosphere during entry, impacts of large asteroids have produced thousands of megatons of energy, more energy than that in all nuclear weapons. The Earth has had a long history of impact events which have been integral in shaping its physical and chemical composition. Scientists even believe that an impact event which happened millions of years ago was the origin of the Earth鈥檚 water. These collisions also have detrimental effects on the Earth鈥檚 biosphere and have in the past led to the extinction of thousands of species. One example was the Chicxulub impact which happened some 66 million years ago and was the main cause of the Cretaceous-Paleogene mass extinction where about 75% of all plant and animal species were wiped off. The astronomical object behind the Chicxulub impact was an asteroid estimated to be 6.2 miles in length and 9.3 miles in width which left a 112-mile wide crater in the Gulf of Mexico.

Such impact events involving huge astronomical objects are quite rare and are estimated to happen once in millions of years. In recent history, few impact events have been observed including the 1908 Tunguska Event, during which a 600-foot meteoroid fell near the Tunguska River and flattening 770 square miles of the surrounding forest, in the largest impact event in recorded history. Impact events generally occur in regions with little or no human settlement and hence have minimal human casualties. However, in the hypothetical scenario that a large astronomical object falls on a large city, the effects would be disastrous both in human casualties as well as in property damage. Impact events have the potential of ending human civilization and even the extinction of humanity. In light of the potential danger asteroids and other near-Earth-objects pose, governments and major institutions are involved in coming up with ambitious projects to avert such a disaster from happening. For instance, the US government has been surveying to map at least 90% nearby asteroids over 1 kilometer in diameter.

Alien Invasion

The invasion of aliens is a popular theme in literary science fiction. The first publication depicting an alien invasion on Earth was 鈥淢icromegas,鈥� published in 1752 by Voltaire whose storyline involved huge aliens from Sirius and Saturn. However, the 鈥淲ar of the 海角社区s鈥� by HG Wells was the book which popularized the theme all over the 海角社区. Outside of literary works, the alien invasion is considered as a possible cause of a global catastrophe with scholars believing that an extraterrestrial invasion would either lead to the enslavement of humanity or even the complete destruction of the planet. While the existence of such extraterrestrial life is yet to be discovered, some scientists believe that it does exist, albeit in far-away galaxies. Nonetheless, the risk of alien invasion is a serious concern in the United States, with the country even passing legislation based on the subject in 1969 which was known as the 鈥淓xtra-Terrestrial Exposure Law.鈥�

Pandemic

A pandemic is the uncontainable spread of an infectious disease over a large area, usually crossing international boundaries. Pandemics are the one of the most plausible nonanthropogenic cause of a global catastrophe since the spread of infectious diseases is usually extremely hard to contain due to the logistical issues involved. According to the 海角社区 Health Organization, a pandemic begins as an animal infection which is later transmitted to humans, with the spread among people making it affect millions of people over a relatively short period before it is contained either naturally or through human intervention. The current pandemic experienced around the 海角社区 is the HIV/AIDS pandemic which has cost millions of lives globally.

Another ongoing pandemic in the 海角社区 is the malaria pandemic, with about 0.5 billion new cases of the disease being reported each year globally. The Black Death of the medieval period is by far the worst pandemic in the Earth鈥檚 history. The Black Death which was a pandemic caused by the bubonic plague and spread by rats led to the death of as many as 200 million people globally between 1347 and 1353. The pandemic decimated Europe鈥檚 population by as much as 60% and it took more than a century for the population to stabilize. The Spanish Flu of the early 20th century is one of the deadliest pandemics in recent history, with this influenza pandemic killing about 100 million people (equivalent to 5% of the global population) in 18 months. Scientists foresee the emergence of a new pandemic in the near future as pathogens are becoming more resistant to antibiotics such as the Enterococcus and Serratia marcescens bacteria.

Natural Climate Change

In many instances, humanity has been blamed for climate change due to man鈥檚 activities which are detrimental to the environment. However, climate change is not a recent phenomenon and even pre-dates the evolution of man. Throughout the Earth鈥檚 history, the climate has been in a perpetual cycle of change ranging from ice ages to temperate periods. The Earth is believed to undergo an ice age after 40,000 years when global temperatures dip, causing the spread of ice caps from the poles towards the tropics. An ice age would have disastrous effects on modern civilization because, while the tropics would still have ideal temperatures for normal habitation, water would become scarce and plunge the 海角社区 into a food crisis.

Cosmic Threats

Cosmic threats are arguably the most frightening of all nonanthropogenic causes of global catastrophe as they are extremely hard to predict and some have the potential of destroying the 海角社区 without humanity knowing. An example of a cosmic threat is a gamma-ray outburst which is among the most powerful energy sources in the universe, with an outburst releasing as much energy as that released by the sun in its entire lifespan. While highly unlikely, a gamma-ray outburst directed at the Earth would lead to its destruction. Other cosmic threats include solar flares, hypernovas, and black holes.