Is it possible to stop the world from ending

Killing all life on Earth would require an impact that literally boils away the oceans. There is evidence that infant Earth was struck by a large planetoid called Theia. But these days, collisions of such large objects are extremely unlikely. For a more likely glimpse of an Earth-altering cataclysm, we need to look to the distant past. Nearly 2. An eruption of cyanobacteria, sometimes called blue-green algae, filled our atmosphere with oxygen, creating a world where multicellular life-forms could take hold, and where creatures like humans could ultimately breathe.

The planet saw a sudden drop in oxygen levels that lasted for several million years. What could have caused such an extreme event? During the Ordovician period, the continents were one jumbled mass called Gondwana.

Most life on Earth still lived in the oceans, but plants were beginning to emerge on land. Then, near the end of the Ordovician, a sweeping climate shift left the supercontinent covered with glaciers. That global cooling alone was enough to start killing off species. But then a second pulse of the extinction ramped up as oxygen levels plummeted.

Scientists see evidence of this shift in seafloor samples collected from around the world. Some researchers think that the glaciers were responsible for fundamentally changing the layers of the oceans, which have unique temperatures and specific concentrations of elements like oxygen. Yet, the exact cause of the oxygen drop is still up for debate.

Whatever the cause, the end result is that more than 80 percent of life on Earth died during the Late Ordovician mass extinction, according to some estimates. So, it may have happened before, but could a deoxygenation event happen again? In an eerie comparison to today, researchers involved in the recent Nature Communications study say that climate change is already reducing oxygen levels in our oceans, potentially killing off marine species.

Even if a sudden spate of global cooling sparked the Late Ordovician mass extinction, what set that in motion in the first place? Over the years, numerous astronomers have suggested the culprit might have been a gamma-ray burst GRB. So far, GRBs have only been spotted in other galaxies. But if one did happen in the Milky Way, as has likely happened in the past, it could cause a mass extinction on Earth. A GRB pointed in our direction might last just 10 seconds or so, but it could still destroy at least half Earth's ozone in that short period of time.

Wiping out the ozone on a large enough scale could wreak havoc on food chains, killing off huge numbers of species. A GRB would wipe out the lifeforms that live in the upper levels of the ocean, which currently contribute significant amounts of oxygen to our atmosphere. And, it turns out, gamma rays also break apart atmospheric oxygen and nitrogen. These gasses get converted into nitrogen dioxide, which is more commonly known as the smog that blocks out the Sun above heavily polluted cities.

Having this smog blanketing the entire Earth would block out sunshine and kickstart a global ice age. Any of the devastating scenarios above, while undoubtedly terrible for life, are just a fraction as bad as future Earth's ultimate fate.

Gamma-ray burst or not, in about a billion years, most life on Earth will eventually die anyway due to a lack of oxygen. The researchers suggest that our oxygen-rich atmosphere is not a permanent feature of the planet. Instead, in about a billion years, solar activity will cause atmospheric oxygen to plummet back down to the level it was at before the Great Oxidation Event. To determine this, the authors combined climate models and biogeochemistry models to simulate what will happen to the atmosphere as the Sun ages and puts out more energy.

They found that, eventually, Earth reaches a point where atmospheric carbon dioxide breaks down. At that point, oxygen-producing plants and organisms that rely on photosynthesis will die out. The meltdown at Three Mile Island and the decades-long debate about storing nuclear waste at Yucca Mountain have made people skittish about the prospects of this carbon-free energy source, but the UN and many experts say fission energy will be key to hitting our climate goals.

The world needs to halve its carbon emissions by , and embracing the new generation of nuclear reactors may be key to making that happen. In he showed off, for the first time, the rocket that could make that happen. In he predicted SpaceX would send a cargo mission to Mars by The following year, he said the first crewed mission to Mars would happen in seven to ten years, or no later than Musk is notorious for wildly underestimating the amount of time it takes to accomplish his ambitious goals, so don't schedule your launch parties just yet.

Still, he tends to follow through on his promises—eventually. Predictions for the future often have a sci-fi bent: jet packs, flying cars, brain-computer hybrids. The United Nations is supposed to stick to more solid ground, but some of its Sustainable Development Goals for sound nearly as fantastical.

No big deal. The good news is that crushing global poverty has declined significantly: The World Bank reports that 1. The organization has been working with countries to improve education, gender equality, food security, social services, and more.

The prospect of ending poverty seems, well, poor. But let's face it, the future is unknowable. Yet it also foresaw the mobile phone and color photography.

Welcome to the Moon Base. Topics nuclear power genome. Whether in the form of organisms and their biophysical games with inanimate environments, or the back and forth of feedbacks in the dynamics of a well-heated, chemically rich rocky planet. There are two principal aspects to these. For example, the trigger for that trauma might be when species approaches a particular level of planetary dominance.

With their civilization reaching a tipping point of scale that is far more likely to produce detectable technosignatures for distant astronomers —whether as infrared excesses from waste energy or a flood of peculiar atmospheric compounds from polluting industrial processes. But it could also be that it is precisely at this point in its existence that a species begins to really look beyond its planetary confines.

Or a coincidence that there is a resurgence of scientific interest in the search for extraterrestrial intelligence? Or that there is an ongoing acceleration in machine learning and algorithms and devices that have the potential to grow exponentially and subvert aspects of our cognitive existence? Apart from passive technosignatures, like rapid climate change, the launch of interplanetary or interstellar spacecraft could, if beamed-light propulsion is utilized, produce potent signals detectable elsewhere in the cosmos.

Communications with a growing population of exploration vehicles and settlements within a planetary system, or with probes launched to other stars, could also create a noisy beacon for other species to detect.

Even efforts to terraform other worlds and of course this is stretching the realm of possibilities a little , would present a rather shocking event to advanced alien observers steadily tracking the properties of a system. And perhaps the ultimate in last-ditch attempts to avert a slow-rolling planetary disaster is to send out a distress signal, looking for answers to existential challenges; because at that point why not? There is a catch though, and it relates to the well-worn ideas of the Fermi paradox.

By the time a species is compelled into doing any of these things, and even before its planetary environment is pushed to a Klaxon-like tipping point, perhaps it simply fails.