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(Max, professor doing AI research at the Massachusetts Institute of Technology https://time.com/6290977/nuclear-war-impact-essay/)

We know that an all-out U.S.-Russia nuclear war would be bad. But how bad, exactly? How do your chances of surviving the explosions, radiation, and nuclear winter depend on where you live? The past year’s unprecedented nuclear saber-rattling and last weekend’s chaos in Russia has made this question timely. To help answer it, I’ve worked with an amazing interdisciplinary group of scientists (see end credits) to produce the most scientifically realistic simulation of a nuclear war using only unclassified data, and visualize it as a video. It combines detailed modeling of nuclear targeting, missile trajectories, blasts and the electromagnetic pulse, and of how black carbon smoke is produced, lofted and spread across the globe, altering the climate and causing mass starvation. As the video illustrates, it doesn’t matter much who starts the war: when one side launches nuclear missiles, the other side detects them and fires back before impact. Ballistic missiles from U.S. submarines west of Norway start striking Russia after about 10 minutes, and Russian ones from north of Canada start hitting the U.S. a few minutes later. The very first strikes fry electronics and power grids by creating an electro-magnetic pulse of tens of thousands of volts per meter. The next strikes target command-and-control centers and nuclear launch facilities. Land-based intercontinental ballistic missiles take about half an hour to fly from launch to target. Major cities are targeted both because they contain military facilities and to stymie the enemy’s post-war recovery. Each impact creates a fireball about as hot as the core of the sun, followed by a radioactive mushroom cloud. These intense explosions vaporize people nearby and cause fires and blindness further away. The fireball expansion then causes a blast wave that damages buildings, crushing nearby ones. The U.K. and France have nuclear capabilities and are obliged by NATO’s Article 5 to defend the U.S. so, Russia hits them too. Firestorms engulf many cities, where storm-level winds fan the flames, igniting anything that can burn, melting glass and some metals and turning asphalt into flammable hot liquid. Unfortunately, peer-reviewed research suggests that explosions, the electromagnetic pulse, and the radioactivity aren’t the worst part: a nuclear winter is caused by the black carbon smoke from the nuclear firestorms. The Hiroshima atomic bomb caused such a firestorm, but today’s hydrogen bombs are much more powerful. A large city like Moscow, with almost 50 times more people than Hiroshima, can create much more smoke, and a firestorm that sends plumes of black smoke up into the stratosphere, far above any rain clouds that would otherwise wash out the smoke. This black smoke gets heated by sunlight, lofting it like a hot air balloon for up to a decade. High-altitude jet streams are so fast that it takes only a few days for the smoke to spread across much of the northern hemisphere. This makes Earth freezing cold even during the summer, with farmland in Kansas cooling by about 20 degrees centigrade (about 40 degrees Fahrenheit), and other regions cooling almost twice as much. A recent scientific paper estimates that over 5 billion people could starve to death, including around 99% of those in the US, Europe, Russia, and China – because most black carbon smoke stays in the Northern hemisphere where it’s produced, and because temperature drops harm agriculture more at high latitudes. It’s important to note that huge uncertainties remain, so the actual humanitarian impact could be either better or worse – a reason to proceed with caution. A recently launched $4M open research program will hopefully help clarify public understanding and inform the global policy conversation, but much more work is needed, since most of the research on this topic is classified and focused on military rather than humanitarian impacts. We obviously don’t know how many people will survive a nuclear war. But if it’s even remotely as bad as this study predicts, it has no winners, merely losers. It’s easy to feel powerless, but the good news is that there is something you can do to help: please help share this video! The fact that nuclear war is likely to start via gradual escalation, perhaps combined by accident or miscalculation, means that the more people know about nuclear war, the more likely we are to avoid having one.

IN the early 1980s, American and Russian scientists working together outlined a stark vision of the Cold War future. In a battle between the two superpowers, smoke from fires ignited by nuclear explosions would be so dense that it would block out the sun, turning the earth cold, dark and dry, killing plants and preventing agriculture for at least a year. This dystopia became known as nuclear winter. We haven’t heard much about this apocalyptic future in recent years. But the research into the destructive potential of a war involving nuclear weapons has continued. Even with the reduced nuclear arsenals that the United States and Russia agreed to in 2010, we have the ability not only to set off instantaneous destruction, but also to push global temperatures below freezing, even in summer. Crops would die and starvation could kill most of humanity. But it is not just the superpowers that threaten the planet. A nuclear war between any two countries using 100 Hiroshima-size atom bombs, less than half of the combined arsenals of India and Pakistan, could produce climate change unseen in recorded human history. This is why we should celebrate the recent agreement with Iran, which may stop it from producing a nuclear weapon. And it is also why we should look with deep alarm at North Korea’s recent launching of a rocket to put a satellite in orbit, in what is believed to be an effort to develop an intercontinental ballistic missile. Nine countries have nuclear arsenals, with an estimated total of 15,695 weapons, according to the Ploughshares Fund, a global securities group. About 94 percent are held by the United States and Russia. Except for North Korea, the other nuclear nations have each kept their arsenals at roughly 100 to 300 weapons. All have the destructive power to alter the global environment. These weapons have not been a deterrent to war or aggression. But even if you think they can be, how many would you have to use? The answer is, probably one. There are simply too many nuclear weapons in the world, by as much as a factor of 1,000, for anyone, anywhere, to be safe from the potential effects of even a small war. The chance that nuclear weapons would be used by mistake, in a panic after an international incident, by a computer hacker or by a rogue leader of a nuclear nation can be eliminated only by the removal of the weapons themselves. We were among the scientists involved in the initial research that discovered the potential for nuclear winter. More modern and advanced climate modeling has confirmed the initial findings and shown that the effects would last for more than a decade. The reason is that smoke from nuclear conflagrations would rise as high as 25 miles into the atmosphere, where it would be protected from rain and take at least 10 years to dissipate. In more recent research, we looked at the potential impact of a nuclear war between India and Pakistan, with each country detonating 50 Hiroshima-size bombs. These explosions would produce so much smoke that temperatures would plunge, shortening growing seasons and threatening the global food supply. Our calculations, based on how crops grow in different weather, showed that wheat, rice, corn and soybean production could be reduced by 10 percent to 40 percent overall for five years. The ozone layer would also be depleted, allowing more ultraviolet radiation to reach the earth’s surface. We hope this continuing research on the effects of even a so-called small nuclear war will highlight the threat to the planet in the same way that visions of a nuclear winter did more than three decades ago for Russian and American leaders, when the total number of nuclear weapons peaked at about 70,000. As Ronald Reagan put it in 1985, “A great many reputable scientists are telling us that such a war could just end up in no victory for anyone because we would wipe out the earth as we know it.” Mikhail S. Gorbachev, the last leader of the Soviet Union, echoed Reagan’s comment in an interview in 2000: “Models made by Russian and American scientists showed that a nuclear war would result in a nuclear winter that would be extremely destructive to all life on earth; the knowledge of that was a great stimulus to us” to reduce the size of nuclear arsenals in both countries. The Obama administration’s goal is to work for the elimination of nuclear weapons, with no specific timetable. But President Obama does not need a treaty with the Russians to take this action. He can just follow the lead of President George H. W. Bush, who unilaterally reduced America’s nuclear arsenal as the Soviet Union was disintegrating. With less than a year left in office, President Obama could add to his legacy by sending a similar signal to the Russians today. We could reduce our arsenal from roughly 7,000 weapons to 1,000, eliminating land-based missiles and outlining plans to further reduce air- and submarine-based missiles. Mr. Obama said himself in 2009 that “the existence of thousands of nuclear weapons is the most dangerous legacy of the Cold War” and that the United States, as the only nation to have used these weapons, had “a moral responsibility” to seek a world without them. “We have to insist,” he said, “‘Yes, we can.’”

If we look at the four categories in which SIOP targets were grouped by the Cold War’s end (US GAO 1991: 2), we can easily see that moving from the first to any of the next three— and especially the fourth— amounted to countervalue targeting: (1) Nuclear Forces (ballistic missiles and their launch facilities and con- trol centers; nuclear weapons storage sites; airfields supporting nuclear- capable aircraft; ballistic missile submarine bases); (2) Leadership (command posts; key communication facilities); (3) Other Military Forces (barracks, supply depots, marshaling points; airfields not supporting nuclear forces; ammunition storage facilities; tank and vehicle storage yards); and (4) War- Supporting Industrial and Economic Factories (industrial: ammunition factories, tanks and armored per- sonnel carrier factories, petroleum refineries, railway yards and repair facilities; eco- nomic: coal, basic steel, basic aluminum, and electric power).

We could argue that “Nuclear Forces” are counterforce targets, but even that distinction takes no account of their vast number, or locations proximate to urban areas. Indeed, a counterforce strategy aimed “strictly” at nuclear- force targets would require many more times the weapons needed to destroy Soviet cities (Lortie 2001: 23). Thus, the United States could not destroy military targets without imposing significant “value” damage through errant blasts, fallout, and the destruction of collocated targets (McKinzie et al. 2001). Although warfighters touted the idea of counterforce exchanges that would “spare” urban targets, the indirect and collateral effects on cities— ensuing, for instance, from the spread of fallout from “surgical strikes” on nuclear missiles— would include the deaths of millions of Soviet and US citizens. The destruction of roads, governmental facilities, communi- cation links, vital industries, and so forth would destroy critical economic, societal, and governmental nodes, with (cumulative) contagion effects that would, in turn, destroy society as it previously existed.

With the new NATO plan for installation of nuclear tactical weapons in Europe, nuclear missiles may reach Moscow in only 6 minutes, and the opposite case is also possible in the same time. The question is: how can we be sure that this will not be triggered by a human error or computer malfunction. An adequate reaction dictated by the dilemma “to be or not to be” and the concept of preventive nuclear strike may lead to a nuclear consequence that is difficult to stop. At the present level of distributed controlled systems and military global navigations, this will lead to unstoppable global nuclear war. However, there is something not predicted, of which the military strategists, politicians and powerful forces are not aware. Probably, it will not be a nuclear winter that they hope to survive in their underground facilities. The most probable consequence will be a partial loss of the Earth’s atmosphere as a result of one or many powerful simultaneous tornadoes caused by the nuclear explosions.

In a tornado, a powerful antigravitational effect takes place. The official science does not have an adequate explanation for this feature due to an incorrect concept about space. The antigravitational effect is not a result of the circling air. It is a specific physical effect in the aether space that is dismissed in physics as it is currently taught. Therefore, the effective height of this effect is not limited to the height of the atmosphere. Then in the case of many simultaneous powerful tornadoes, an effect of suction of the earth atmosphere into space might take place. Such events are observed on the Sun and the present physical science does not have an explanation for them. The antigravitational effect is accompanied by specific electric and magnetic fields with a twisted shape. This is observed in tornado events on the Sun. Some effects in the upper Earth atmosphere known as sprites have a similar combination of electrical and magnetic fields but in a weaker form. They are also a mystery for contemporary physical science.

In the nuclear conversation, what are we not talking about that we should be?

We are not talking enough about the climatic effects of nuclear war.

Humanity is facing its greatest test in the million-year ascent of our kind. This isn’t a single challenge. It’s a constellation of huge man-made threats, now coming together to overshadow our civilisation’s stability and even, maybe, its future survival. These ten intersecting risks are: ecological collapse, resource depletion, weapons of mass destruction, climate change, global poisoning, food insecurity, population and urban failure, pandemic disease and uncontrolled new technologies (like killer robots, artificial intelligence and universal surveillance) – reinforced by a prodigious capacity for human self-delusion. But sticking our heads in the sand and trying to ignore them will not remove the danger.

These threats are known as ‘existential risks’ because they imperil our future existence, both as individuals, as a civilisation and maybe even as a species.

Now 10 years ago, several of the world’s leading climatologists and physicists chose to reinvestigate the long-term environmental impacts of nuclear war. The peer-reviewed studies they produced are considered to be the most authoritative type of scientific research, which is subjected to criticism by the international scientific community before final publication in scholarly journals. No serious errors were found in these studies and their findings remain unchallenged.

Alan Robock et al., “Nuclear winter revisited with a modern climate model and current nuclear arsenals: Still catastrophic consequences,” Journal of Geophysical Research: Atmospheres 112 (2007).

Every few days, Russia’s rhetoric around the potential use of a nuclear weapon in Ukraine seems to shift back and forth. One day, Russian military leaders are discussing plans for the use of a tactical nuclear weapon; another day, the Kremlin is stating explicitly that a nuclear war should never be fought, and that using such weapons would have no political or military value. More From Our Experts Stephen Sestanovich How Should NATO Think About Ukrainian Membership After Russia’s Coup Attempt? Thomas Graham Expect Changes in Russia as Response to Wagner Rebellion Robert D. Blackwill Policy Prescriptions for U.S.-China Relations While there are numerous rungs on the metaphorical escalation ladder before the nuclear question would come into play, there are at least three distinct scenarios for Russia’s use of a nuclear weapon, each of which differs in rationale and likely consequences. Scenario 1: A Signaling Device More on: Russia Ukraine Military Operations Defense and Security NATO (North Atlantic Treaty Organization) Rationale: Russia could test nuclear weapons as a warning to Ukraine and its supporters, demonstrating both its resolve and capability. Actions speak louder than words, so testing a nuclear weapon could drive home Russian President Vladimir Putin’s past statements that this “special military operation” in Ukraine is becoming an existential conflict for the Russian state. The World This Week A weekly digest of the latest from CFR on the biggest foreign policy stories of the week, featuring briefs, opinions, and explainers. Every Friday. Email Address View all newsletters > The last Russian nuclear test occurred under the Soviet Union on October 24, 1990; and, apart from North Korea, no state has conducted a nuclear test since 1998. Russia could conduct a nuclear demonstration in its northern regions, international waters, or an uninhabited part of Ukraine. Each of these options would, respectively, be more brazen in the extent to which they would depart from decades-old norms surrounding testing. Russia would likely take care to ensure that the test causes no casualties and yields minimal radioactive fallout. Likely effects: A nuclear demonstration would not tilt the balance in favor of either side. The efficacy of even Russia’s most advanced nuclear weapons is likely already known to relevant Western governments, and a test likely would not incentivize Ukraine to capitulate because Kyiv already feels that the conflict is existential. Russia’s recent aerial bombing campaigns have shown that, if anything, a nuclear demonstration is likely to harden Kyiv’s resolve and engender more sympathy and support from the West. The humanitarian and environmental effects are also likely to be minimal, as the test site would be chosen with those impacts in mind. One unwanted side effect could concern Russia’s relations with China. China has tried to tow a careful line in maintaining the strong personal relationship between President Xi Jinping and Putin without kindling outright hostility from the West. China has thus far been sympathetic to Russia’s broader strategic goals in Ukraine, but a Russian nuclear test could put Beijing in a tough position. Xi recently stated China’s opposition to any country using or threatening to use nuclear weapons. Scenario 2: A Battlefield Weapon Rationale: Russia could use nuclear weapons against Ukrainian military or energy infrastructure targets in an attempt to weaken the country’s will and damage its military capacity. Tactical nuclear weapons have a smaller payload and more precise targeting, which makes them conducive to battlefield use. Russia has about two thousand tactical nuclear weapons that it could deploy by plane, missile, or ship. It would most likely use the short-range Iskander-M missile system. These weapons have yields of 1–50 kilotons, the largest of which would have a blast radius about half a kilometer wider than the bomb the U.S. military dropped on Hiroshima, Japan, at the end of World War II. A Russian nuclear test could put Beijing in a tough position. In one hypothetical, Russia could target Ukrainian forces in Luhansk near the Troitske-Svatove-Kreminna line to prevent Russian forces from having to retreat, like they did in Kherson. A nuclear attack could weaken those Ukrainian forces and create an uninhabitable no-man’s-land that would make Ukraine think twice about advancing before or during the winter. Likely effects: Russia’s use of a tactical nuclear weapon against military targets on the battlefield would be unlikely to halt the Ukrainian counteroffensive. Even if a battlefield nuclear weapon made a land advance more challenging, Ukraine would likely continue its focus on aerial attacks and air defense in ways that have been successful in recent weeks. Moreover, using nuclear weapons on the battlefield would be less effective in shutting down Ukrainian electricity and energy infrastructure than conventional bombing because their higher yield and lower accuracy makes them ill-suited for those targets. The environmental effects of tactical nuclear weapons use are difficult to calculate and would depend on warhead yield, detonation height, weather, and local geography. Russia would be cautious not to detonate weapons too close to its own soldiers or occupied territory. China would almost certainly be forced to publicly denounce such weapons use by Russia, and the resulting distancing would have repercussions for future China-Russia cooperation more broadly. The West likely would not respond to tactical nuclear use by sending troops into Ukraine, but the United States and its allies would likely ramp up the number of conventional weapons they send to Ukraine. Western states would also be more willing to provide non-military humanitarian assistance in response to the fallout and radiation, which could also affect neighboring countries. Scenario 3: A Weapon of Terror Rationale: Russia’s most escalatory option is also the least likely—using a strategic nuclear weapon against Ukrainian civilian targets or Ukraine’s neighboring international partners. Such an attack would be hundreds of times more powerful than one that used tactical weapons. Russia’s aim would be to weaken Western resolve, and it would likely target military installations or infrastructure relevant to the Ukrainian war effort, such as arms supply lines in Poland or weapon storage facilities in the Baltics. Bombing a major Western city such as Paris or Los Angeles, by comparison, would only elicit a stronger Western reaction. This is also the scenario where a Western nuclear response is most likely. Abandoned strollers are pictured under a destroyed bridge as people flee the city of Irpin, west of Kyiv. Abandoned strollers are pictured under a destroyed bridge as people flee the city of Irpin, west of Kyiv, in March 2022. Aris Messinis/Getty Images While the Ukraine conflict is not an existential threat to Russia, Putin could perceive it as a threat to himself. He likely fears that losing the war would mean losing power or his life. As the likelihood of that prospect increases, Putin could view nuclear weapons as a last resort for self-preservation, no matter the external costs. Russia recently raised alarms in Western capitals by alleging that Ukraine was planning to use an improvised nuclear device often referred to as a “dirty bomb.” Experts say most of the damage from such a device would be from its explosion, and that it would pose far less of a radiation threat than a traditional nuclear weapon. Ukraine and its allies dismissed the claim as false and potentially deceptive propaganda intended to give Russia a pretext to escalate the war with nuclear weapons. Likely effects: Using a nuclear weapon against civilian or non-Ukrainian targets would certainly generate a retaliatory response from Western states. The United States would be unlikely to default to nuclear weapons given its confidence in the demonstration of resolve that would result from a swift, sophisticated conventional response, which would also be tactically effective. Eastern European members of the North Atlantic Treaty Organization (NATO), who could fear becoming Russia’s next target, would be particularly interested in ensuring that the alliance mobilizes a response that sends a strong signal to Russia that nuclear use will never help it achieve expansionist objectives. President Joe Biden has staked out the U.S. position on the issue, noting, “Any use of nuclear weapons in this conflict on any scale would be completely unacceptable to us as well as the rest of the world and would entail severe consequences.” This vagueness is intentional and consistent with a long-standing U.S. policy of “strategic ambiguity” aimed at giving U.S. policymakers flexibility in deciding how to respond to nuclear events. More direct Western involvement would dramatically change the intensity of the conflict. Absent U.S. casualties from a Russian nuclear attack outside of Russia or Ukraine, U.S. involvement will likely remain indirect through increased arms sales and nonmilitary support. The United States could be more likely to use conventional weapons directly against Russia, although it would take care to signal that it aims to defend Ukraine and the West rather than conquer Moscow. Any Western troop deployment would not cross the border into Russia, and even the use of advanced cruise missiles, drones, and ground operations would be limited to Russian targets in Ukraine. Non-kinetic operations such as cyberattacks would likely continue, although little would be known about those until well after the war is over.

Who owns the world’s nuclear weapons? Despite progress in reducing nuclear weapon arsenals since the Cold War, the world’s combined inventory of nuclear warheads remains at a very high level: nine countries possessed roughly 12,500 warheads as of early-2023. Combined, the United States and Russia now possess approximately 89 percent of the world’s total inventory of nuclear weapons, and 86 percent of the stockpiled warheads available for use by the military. Currently, no other nuclear-armed state sees a need for more than a few hundred nuclear weapons for national security, although many of these states are increasing their nuclear stockpiles. Globally, the overall inventory of nuclear weapons is declining, but the pace of reductions is slowing compared with the past 30 years. Moreover, these reductions are happening only because the United States and Russia are still dismantling previously retired warheads. In contrast to the overall inventory of nuclear weapons, the number of warheads in global military stockpiles – which comprises warheads assigned to operational forces – is increasing once again. The United States is still reducing its nuclear stockpile slowly. France and Israel have relatively stable inventories. But China, India, North Korea, Pakistan and the United Kingdom, as well as possibly Russia, are all thought to be increasing their stockpiles (see map below, click here for higher resolution image): Of the world’s approximate 12,500 nuclear warheads, roughly 9,576 are in the military stockpiles for use by missiles, aircraft, ships and submarines. The remaining warheads have been retired but are still relatively intact and are awaiting dismantlement). Of the 9,576 warheads in the military stockpiles, some 3,804 are deployed with operational forces (on missiles or bomber bases). Of those, approximately 2,000 US, Russian, British and French warheads are on high alert, ready for use on short notice (see table): Estimated Global Nuclear Warhead Inventories, 2023 HANS M. KRISTENSEN, MATT KORDA, AND ELIANA REYNOLDS, FEDERATION OF AMERICAN SCIENTISTS, 2023 The exact number of nuclear weapons in each country’s possession is a closely held national secret, so the estimates presented here come with significant uncertainty. Most nuclear-armed states provide essentially no information about the sizes of their nuclear stockpiles. Yet the degree of secrecy varies considerably from country to country. Between 2010 and 2018, the United States disclosed its total stockpile size, but in 2019 the Trump administration stopped that practice. In 2020, the Biden administration restored nuclear transparency – a brief victory for nuclear accountability in a democratic country – but then declined to declassify any US stockpile data for 2021 or 2022. Similarly, in 2021 the United Kingdom announced that it would no longer disclose public figures for its operational stockpile, deployed warhead or deployed missile numbers. Additionally, as of 2023 both the United States and Russia have elected to no longer exchange publicly-available data about their deployed strategic warheads and launchers as mandated by the New START Treaty. Despite these limitations, however, publicly available information, careful analysis of historical records, and occasional leaks make it possible to make best estimates about the size and composition of the national nuclear weapon stockpiles. For a breakdown of the nuclear warhead categories of the different nuclear-armed states, and for links to more details overviews of each country’s arsenals, see this table: Status Of World Nuclear Forces 2023 COUNTRY DEPLOYED STRATEGIC DEPLOYED NONSTRATEGIC RESERVE/NONDEPLOYED MILITARY STOCKPILE(A) TOTAL INVENTORY(B) RUSSIA 1,674(C) 0(D) 2,815(E) 4,489 5,889 UNITED STATES 1,670(G) 100H 1,938(I) 3,708(J) 5,244(K) FRANCE 280(L) N.A. 10(L) 290 290 CHINA 0(M) N.A. 410 410 410(M) UNITED KINGDOM 120(N) N.A. 105 225 225(N) ISRAEL 0 N.A. 90 90 90(O) PAKISTAN 0 N.A. 170 170 170(P) INDIA 0 N.A. 164 164 164(Q) NORTH KOREA 0 N.A. 30 30 30(R) TOTALS ~3,744 ~100 ~5,732 ~9,576 ~12,512 Status of World Nuclear Forces, 2023 How to read this table: “Deployed strategic warheads” are those deployed on intercontinental missiles and at heavy bomber bases. “Deployed nonstrategic warheads” are those deployed on bases with operational short-range delivery systems. “Reserve/Nondeployed” warheads are those not deployed on launchers but in storage (weapons at bomber bases are considered deployed). The “military stockpile” includes active and inactive warheads that are in the custody of the military and earmarked for use by commissioned deliver vehicles. The “total inventory” includes warheads in the military stockpile as well as retired, but still intact, warheads in the queue for dismantlement. For additional guidance, see endnotes below (note: as estimates are updated, they may vary from the printed materials below). EXPAND FOOTNOTES

An AI researcher has called on the countries of the world to use the threat of nuclear war to prevent the rise of artificial general intelligence. In an op-ed for TIME, AI theorist Eliezer Yudkowsky said that pausing research into AI isn’t enough. Yudkowsky said that the world must be willing to destroy the GPU clusters training AI with airstrikes and threaten to nuke countries that won’t stop researching the new technology. ADVERTISEMENT Yudkowsky’s op-ed was a response to an open letter calling for a six month moratorium in the study of AI by asking the world to shut down all its AI research. In Yudkowsky’s thinking, the pause isn’t long enough. For him, it is not a matter of if AI will kill humanity, but when. “Not as in ‘maybe possibly some remote chance,’ but as in ‘that is the obvious thing that would happen,’” he wrote. Yudkowsky believes that the only way to stop the creation of AGI—machine intelligence that matches or surpasses humans—and therefore the destruction of the entire human race, is to take actions that would inevitably cause a wider war and lead to millions, or even billions, of dead humans. In his piece for TIME, Yudkowsky said that the world must shut down all the large GPU clusters and put a ceiling on the power draw used by a computing system training AI. “No exceptions for governments and militaries,” he said. “Make immediate multinational agreements to prevent the prohibited activities from moving elsewhere. Track all GPUs sold. If intelligence says that a country outside the agreement is building a GPU cluster, be less scared of a shooting conflict between nations than of the moratorium being violated; be willing to destroy a rogue datacenter by airstrike.” ADVERTISEMENT Yudkowsky is asking the audience to be more afraid of the hypothetical possibility that AI will kill humans than the likelihood that his prescriptions would cause a nuclear war. “Frame nothing as a conflict between national interests, have it clear that anyone talking of arms races is a fool. That we all live or die as one, in this, is not a policy but a fact of nature,” he said. “Make it explicit in international diplomacy that preventing AI extinction scenarios is considered a priority above preventing a full nuclear exchange, and that allied nuclear countries are willing to run some risk of nuclear exchange if that’s what it takes to reduce the risk of large AI training runs.” The U.S. and China are the relevant examples here because both their military and civilian infrastructures are racing towards developing AI. These are the countries, in Yudkowsky’s scenario, most likely to air strike a data center in the heart of their rival. To be clear, either country conducting that kind of airstrike would start a war, full stop. Tensions are already high between China and the U.S. and both are armed with nuclear weapons. China can’t float a balloon above the U.S. without the Pentagon shooting it down, it’s hard to imagine it responding to an airstrike on a data center in San Antonio with anything less than the full force of its military. China, likewise, likely wouldn’t suffer an incursion and bombing in its airspace. Yudkowsky made clear that nuclear threats are on the table and that the world’s great powers should not stop short of a full nuclear exchange to prevent the rise of AI. China and the U.S. entering into a full nuclear exchange would kill billions of people and permanently alter the climate of the planet, starving billions more. He is, in his moral calculus, willing to kill potentially billions of people and possibly doom the planet for a generation to prevent The Terminator from happening.

It's not often that astronomy goes well with the book of Genesis. But this is a theory that evokes the line, "But of the tree of the knowledge, thou shalt not eat of it: for in the day that thou eatest thereof thou shalt surely die." In this theory, knowledge doesn't just kill you — it kills the entire universe. Indeed, one physicist speculates that continuous observation of the universe might put it into a state that will destroy us all.

The Curse of the Big Bang

Dark energy, the mysterious entity that dominates the energy of the cosmos and appears to be accelerating the expansion of the universe, presents a cosmic conundrum for scientists. In short, cosmologists have no idea what dark energy really is. So they are concocting all sorts of possible models, and exploring the observational consequences of those models, in hopes of finding some clue as to what dark energy is and how it works. Now, new research suggests that we may have already found evidence of an evolving, dynamic kind of dark energy, in the form of the radiation emitted when the first stars appeared in the universe. Billions of years ago, the universe was much darker than it is today. It took time for the first stars and galaxies to coalesce and appear, and when they did, they completely transformed the cosmos. Prior to the formation of the first stars, the universe was dominated by a thin fog of neutral hydrogen and helium gas. That gas had formed during the momentous epoch known as recombination, a stage that occurred when our universe was 380,000 years old and had cooled to the point where the hot plasma could become neutral — when electrons could finally bind to nuclei to form the first atoms. When the first stars ignited, however, their intense radiation ripped through the neutral gas, turning it back into a plasma state. And so cosmologists named the appearance of the first stars the "Cosmic Dawn" and the subsequent dramatic phase change of the universe the "Epoch of Reionization." These events occurred around a few hundred million years after the Big Bang. We do not yet have any direct measurements or maps of the cosmological epoch when the first stars and galaxies formed, or of the Epoch of Reionization. The main challenge is that these events occurred an extremely long time ago, so the light from those first stars is incredibly weak. An open window But there is another window into the Epoch of Reionization. Neutral hydrogen emits radiation at an extremely specific wavelength: 21 centimeters (8.3 inches). This is not a strong signal at all, but there was a whole lot of neutral hydrogen back in the day. But that radiation was emitted billions of years ago, and in the intervening ages, the universe has expanded to be about 10 times its previous size. That expansion has stretched the wavelength of that 21-cm radiation, and today, it's now detectable in radio wavelengths. In 2018, a team of astronomers claimed to have detected the 21-cm signal emitted when the universe was only 230 million years old. But the signal from that radiation was more than twice as strong as theoretical calculations had suggested. Assuming that the observation is valid (which is still a matter of debate, as the result has yet to be replicated by another team), it suggests that something in our understanding of early cosmic history is off. Most recently, Lu Yin, an astrophysicist at the Asia Pacific Center for Theoretical Physics in South Korea, has suggested a new possibility to explain the strange result. Dynamics in the dark Click here for more Space.com videos... RELATED STORIES —How the 'Cosmic Dawn' broke and the first stars formed —Black holes may be the source of mysterious dark energy —Astronomers capture radio signal from ancient galaxy at record-breaking distance Yin's work, published to the preprint database arXiv, explored a model called interacting Chevallier-Polarski-Linder dark energy, or ICPL. In this model, dark energy is not a fixed constant of the cosmos but a dynamical entity that can change and evolve in time, resulting in changes in the acceleration rate of expansion. But that ability to evolve immediately opens up a question: What controls the way dark energy can change? In response, this model allows for dark energy to interact with dark matter; their behavior is linked, keeping both of them in check as the universe expands. There are more cosmological observations than the 21-cm signal. So, to start, Yin tuned the ICPL model to fit other observations, especially ones focusing on the recent expansion history of the universe. With a tuned model in hand, Yin then simulated the evolution of the early universe. Yin found that this ICPL model caused stars and galaxies to appear earlier than in standard cosmological models, which made the ICPL model better at accounting for the strange observed 21-cm signal compared with traditional cosmological models. This is an intriguing result, but not a slam dunk. The 21-cm observations are still in dispute, and there are other possible explanations for the strange signal. Still, this shows how scientists can approach observations like this and continue to push into the frontiers of understanding dark energy and dark matter.

Temperature is a measure of how much the atoms vibrate and move (e.g. kinetic energy). 0 Kelvin is defined as the point where the atoms do not vibrate any more at all, so you can not really have sub-kelvin temperatures, as it is not possible to move less than standing totally still. If you somehow discover that atoms at what we now believe is absolute zero actually move a little, your new temperature is just defined as the new 0 Kelvin.

A second consideration is that negative degrees Kelvin allows for heat flow that reduces entropy, a pretty important violation of physics, as that allows for infinite energy, perpetual motion machines, etc.

A team of researchers has cooled matter to within a billionth of a degree of absolute zero, colder than even the deepest depths of space ,  far away from any stars. Interstellar space never gets this cold due to the fact that it is evenly filled with the cosmic microwave background (CMB), a form of radiation left over from an event that occurred shortly after the Big Bang when the universe was in its infancy. The chilled matter is even colder than the coldest known region of space, the Boomerang Nebula, located 3,000 light-years from Earth, which has a temperature of just one degree above absolute zero. The experiment, run at the University of Kyoto in Japan and used fermions, which is what particle physicists call any particle that makes up matter, including electrons, protons and neutrons. The team cooled their fermions — atoms of the element ytterbium — to around a billionth of a degree above absolute zero, the hypothetical temperature at which all atomic movement would cease. Sponsored Links Play this game for 1 minute and see why everyone is addicted. Raid Shadow Legends "Unless an alien civilization is doing experiments like these right now, anytime this experiment is running at Kyoto University it is making the coldest fermions in the universe," Rice University researcher Kaden Hazzard, who took part in the study, said in a statement. Related: Did this newfound particle form the universe's dark matter? Click here for more Space.com videos... CLOSE The team used lasers to cool the matter by restricting the motion of 300,000 atoms within an optical lattice. The experiment simulates a model of quantum physics first proposed in 1963 by theoretical physicist, John Hubbard. The so-called Hubbard model allows atoms to demonstrate unusual quantum properties including collective behavior between electrons like superconduction ( the ability to conduct electricity without energy loss). "The payoff of getting this cold is that the physics really changes," Hazzard said. "The physics starts to become more quantum mechanical, and it lets you see new phenomena." The 'fossil' radiation that keeps space warm Interstellar space can never get this cold because of the presence of the CMB. This evenly spread and uniform radiation was created by an event during the initial rapid expansion of the universe shortly after the Big Bang, the so-called last scattering. During the last scattering, electrons started to bond with protons, forming the first atoms of the lightest existing element  hydrogen. As a result of this atom formation, the universe rapidly lost its loose electrons. And because electrons scatter photons, the universe had been opaque to light before the last scattering. With electrons bound up with protons in these first hydrogen atoms, photons could suddenly travel freely, making the universe transparent to light. The last scattering also marked the last moment at which fermions like protons and photons had the same temperature. As a result of the last scattering, photons filled the universe at a specific temperature of 2.73 Kelvin, which equals minus 454.76 degrees Fahrenheit (minus 270.42 degrees Celsius) which is just 2.73 degrees above absolute zero — 0 Kelvin or minus 459.67 degrees F (minus 273.15 degrees C). Boomerang nebula – coldest place in the universe The Boomerang nebula is the coldest place in the universe (Image credit: ESA/NASA) RELATED STORIES: — The history of the universe: Big Bang to now in 10 easy steps — What happened before the Big Bang? — Dark matter from 12 billion years ago detected for the 1st time There is one region in the known universe, the Boomerang Nebula, a cloud of gas that surrounds a dying star in the constellation of Centaurus, which is even colder than the rest of the universe — around 1 Kelvin or minus 457.6 ⁰F (minus 272⁰ C). Astronomers believe the Boomerang Nebula is being cooled by cold, expanding gas spat out by the dying star at the nebula's center. But even the Boomerang Nebula can't compete with the temperatures of the ytterbium atom in the latest experiment. The team behind this experiment is currently working on developing the first tools capable of measuring the behavior that arises a billionth of a degree above absolute zero. "These systems are pretty exotic and special, but the hope is that by studying and understanding them, we can identify the key ingredients that need to be there in real materials," Hazzard concluded.

Particle physics is the study of the elementary constituents of matter and radiation, and the interactions between them. A major experimental method in particle physics involves the use of particle accelerators such as the RHIC and LHC to bring beams of particles to near the speed of light and then collide them together. This focuses a large amount of energy in a very small region and breaks the particles down into their components, which are then detected. As particle accelerators have become larger, the energy densities achieved have become more extreme, prompting some concern about their safety. These safety concerns have focused on three possibilities: the formation of ‘true vacuum’, the transformation of the earth into ‘strange matter’, and the destruction of the earth through the creation of a black hole. 4.1 True vacuum and strange matter formation The type of vacuum that exists in our universe might not be the lowest possible vacuum energy state. In this case, the vacuum could decay to the lowest energy state, either spontaneously, or if triggered by a sufficient disturbance. This would produce a bubble of ‘true vacuum’ expanding outwards at the speed of light, converting the universe into different state apparently inhospitable for any kind of life (Turner and Wilczek 1982). Our ordinary matter is composed of electrons and two types of quarks: up quarks and down quarks. Strange matter also contains a third type of quark: the ‘strange’ quark. It has been hypothesized that strange matter might be more stable than 11 normal matter, and able to convert atomic nuclei into more strange matter (Witten 1984). It has also been hypothesized that particle accelerators could produce small negatively charged clumps of strange matter, known as strangelets. If both these hypotheses were correct and the strangelet also had a high enough chance of interacting with normal matter, it would grow inside the Earth, attracting nuclei at an ever higher rate until the entire planet was converted to strange matter — destroying all life in the process. Unfortunately strange matter is complex and little understood, giving models with widely divergent predictions about its stability, charge and other properties (Jaffe, Busza et al. 2000). One way of bounding the risk from these sources is the cosmic ray argument: the same kind of high-energy particle collisions occur all the time in Earth’s atmosphere, on the surface on the Moon and elsewhere in the universe. The fact that the Moon or observable stars have not been destroyed despite a vast number of past collisions (many at much higher energies than can be achieved in human experiments) suggest that the threat is negligible. This argument was first used against the possibility of vacuum decay (Hut and Rees 1983) but is quite general. An influential analysis of the risk from strange matter was carried out in (Dar, De Rujula et al. 1999) and formed a key part of the safety report for the RHIC. This analysis took into account the issue that any dangerous remnants from cosmic rays striking matter at rest would be moving at high relative velocity (and hence much less likely to interact) while head-on collisions in accelerators could produce remnants moving much at much slower speeds. They used the rate of collisions of cosmic rays in free space to estimate strangelet production. These strangelets would then be slowed by galactic magnetic fields and eventually be absorbed during star formation. When combined with estimates of the supernova rate, this can be used to bound the probability of producing a dangerous strangelet in a particle accelerator. The resulting probability estimate was < 2 ! 10-9 per year of RHIC operation.8 While using empirical bounds and experimentally tested physics reduces the probability of a theory error, the paper needs around 30 steps to reach its conclusion. For example, even if there was just a 10-4 chance of a calculation or modelling error per step this would give a total P(¬A)!"!0.3%. This would easily overshadow the risk estimate. Indeed, even if just one step had a 10-4 chance of error, this would overshadow the estimate. A subtle complication in the cosmic ray argument was noted in (Tegmark and Bostrom 2005). The Earth’s survival so far is not sufficient as evidence for safety, since we do not know if we live in a universe with ‘safe’ natural laws or a universe where planetary implosions or vacuum decay do occur but we have just been exceedingly lucky so far. While this latter possibility might sound very unlikely, all observers in such a universe would find themselves to be in the rare cases where 8 (Kent 2004) points out some mistakes in stating the risk probabilities in different versions of the paper, as well as for the Brookhaven report. Even if these are purely typesetting mistakes, it shows that the probability of erroneous risk estimates is nonzero. 12 their planets and stars had survived, and would thus have much the same evidence as we do. Tegmark and Bostrom had thus found that in ignoring these anthropic effects, the previous model had been overly narrow. They corrected for this anthropic bias and, using analysis from (Jaffe, Busza et al. 2000), concluded that the risk from accelerators was less than 10-12 per year. This is an example of a demonstrated flaw in an important physics risk argument (one that was pivotal in the safety assessment of the RHIC). Moreover, it is significant that the RHIC had been running for five years on the strength of a flawed safety report, before Tegmark and Bostrom noticed and fixed this gap in the argument. Although this flaw was corrected immediately after being found, we should also note that the correction is dependent on both anthropic reasoning and on a complex model of the planetary formation rate (Lineweaver, Fenner et al. 2004). If either of these, or the basic Brookhaven analysis is flawed, the risk estimate is flawed. 4.2 Black hole formation The Large Hadron Collider experiment at CERN was designed to explore the validity and limitations of the Standard Model of particle physics by colliding beams of high energy protons. This will be the most energetic particle collision experiment ever done, which has made it the focus of a recent flurry of concerns. Due to the perceived strength of the previous arguments on vacuum decay and strangelet production, most of the concern about the LHC has focused on black hole production. None of the theory papers we have found appears to have considered the black holes to be a safety hazard, mainly because they all presuppose that any black holes would immediately evaporate due to Hawking radiation. However, it was suggested by (Dimopoulos and Landsberg 2001) that if black holes form, particle accelerators could be used to test the theory of Hawking radiation. Thus critics also began questioning whether we could simply assume that black holes would evaporate harmlessly. A new risk analysis of LHC black-hole production (Giddings and Mangano 2008) provides a good example of how risks can be more effectively bounded through multiple sub-arguments. While never attempting to give a probability of disaster (rather concluding "there is no risk of any significance whatsoever from such black holes") it uses a multiple bounds argument. It first shows that rapid black hole decay is a robust consequence of several different physical theories (A1). Second it discusses the likely incompatibility between non-evaporating black holes and mechanisms for neutralising black holes: in order for cosmic ray–produced stable black holes to be innocuous but accelerator-produced black holes to be dangerous, they have to be able to shed excess charge rapidly (A2). Our current understanding of physics suggests both that black holes decay and that even if they didn’t, they would be unable to discharge themselves. Only if this understanding is flawed will the next section come into play. 13 The third part, which is the bulk of the paper, models how multidimensional and ordinary black holes would interact with matter. This leads to the conclusion that if the size scale of multidimensional gravity is smaller than about 20 nm, then the time required for the black hole to consume the Earth would be larger than the natural lifetime of the planet. For scenarios where rapid Earth accretion is possible, the accretion time inside white dwarves and neutron stars would also be very short, yet production and capture of black holes from impinging cosmic rays would be so high that the lifespan of the stars would be far shorter than the observed lifespan (and would contradict white dwarf cooling rates) (A3). While each of these arguments have weaknesses the force of the total argument (A1,A2,A3) is significantly stronger by the combination of them. Essentially the paper acts as three sequential arguments, each partly filling in the grey area (see figure 1) left by the previous. If the theories surrounding black hole decay fail, the argument about discharge comes into play, and if against all expectation black holes are stable and neutral the third argument shows that astrophysics constrains them to a low accretion rate.

An example par excellence of a Q = 0 event is a vacuum phase transition or a comparable quantum field collapse. Such an event would not only extinguish humanity but also completely and permanently destroy the terrestrial biosphere. Coleman and De Luccia first mentioned the possibility that such a disaster might be caused by the operation of high-energy particle colliders used in physics research.(40) This possibility has since been widely discussed,(10,41−46) and has motivated objections to the operation of high-energy particle colliders, including most recently the Large Hadron Collider.(46,47) Three specific threats are relevant: (1) triggering vacuum phase transition through creation of an expanding bubble of “new” vacuum state, (2) accidental production of charged strangelets, which could transform all Earth’s mass into strange matter, and (3) accidental production of a mini black hole falling into Earth’s center and subsequently destroying our planet. Although smacking of science fiction, this idea has been seriously considered even by high-level 1504 Cirkovi ´ c, Sandberg, and Bostrom ´ administrators of modern particle-accelerator laboratories.(48) This is not only an eschatological issue for humanity: a vacuum phase transition would also destroy the habitability of the universe for any other observers in our future light cone. Even if the chance of such a disaster is remote, its catastrophic impact would be so enormous that it deserves close scrutiny. Hut and Rees, in an important pioneering study of the problem of high-energy physics risks, suggested that concerns about particle colliders can be reasonably dismissed because high-energy particle collisions occurring in nature, such as those between cosmic-rays and the Earth’s atmosphere or the solid mass of the Moon, are still orders of magnitude higher than those achievable in human laboratories in the near future.(10) With plausible general assumptions on the scaling of the relevant reaction crosssections with energy, Hut and Rees concluded that the fact that the Earth (and the Moon) have survived cosmic-ray bombardment for about 4.5 Gyr implies that we are safe for the foreseeable future. For example, if the probability of a high-energy physics disaster in nature is 10−50 per year, then a doubling or even 10-fold increase of the risk through deliberate human activities is arguably trivial. The Hut-Rees argument should provide us no comfort, however, as it fails to correct for anthropic bias. A vacuum phase transition is an event for which Q = 0. Probability estimates based on observations of the Earth’s and Moon’s existence are thus completely unreliable. Moreover, the unreliability of these estimates applies to both naturally occurring and humaninduced vacuum phase transitions. (Hut and Rees also conclude, completely justifiably, that the number of potentially risky events in any conceivable human accelerator is much smaller than in the cosmicray interactions in nature.) Unfortunately, the same error is repeated in the recent Large Hadron Collider (LHC) safety study, where the duration of the solar system thus far is invoked as part of the arguments for accelerator safety.(46)

Sir Martin Rees, Britain’s dapper astronomer royal, issues a dark warning in his new book, "On the Future." While assessing various threats facing our species, he turns his attention to particle-accelerator experiments designed to probe the laws of nature. “Some physicists raised the possibility that these experiments might do something far worse — destroy the Earth or even the entire universe,” he writes. In one current or future scenario that Rees describes, the particles crashing about inside an accelerator could unleash bits of “strange matter” that shrink Earth into a ball 300 feet across. In another, the experiments could create a microscopic black hole that would inexorably gnaw away at our planet from the inside. In the most extreme scenario Rees describes, a physics mishap could cause space itself to decay into a new form that wipes out everything from here to the farthest star. These doomsday events are unlikely, Rees concedes, but "given the stakes, they should not be ignored.” Is he right to sound the alarm? How serious are the risks, really? With help from leading scientists, NBC News MACH examines the evidence. A long tradition of worry Rees follows in a long tradition of experts cautioning that modern technology could lead us to disaster. During the 1945 test of the first atomic bomb, physicist Arthur Compton worried that the blast might ignite Earth’s atmosphere. When the Apollo 11 astronauts returned from the moon in 1969, NASA placed them in quarantine in case they were carrying a deadly space disease. More relevant to Rees’ thesis, a retired nuclear safety officer named Walter Wagner filed a lawsuit in 2008 to block operations of the Large Hadron Collider (LHC), the particle accelerator on the Swiss-French border. He cited concerns similar to those listed by Rees. The U.S. 9th Circuit Court threw out the case, ruling that “speculative fear of future harm does not constitute an injury.” A team of physicists had already evaluated the possibility of a disastrous mishap in 2003, and they returned to the issue in 2008. Both times they found the risks inconsequential. “The LHC is safe, for sure,” says Arnaud Marsollier, a spokesman for CERN, the consortium that runs the collider. “There are, every day, cosmic rays [subatomic particles from outer space] with energies far higher than what we will ever be able to produce with a collider. We just do in the lab something that happens in nature all the time, including above our heads in the atmosphere.” A strange way to go Marsollier means that as a reassurance, but it leads to a related fear: If we humans are incapable of destroying ourselves, could a natural physics disaster do the job instead? In 1984 two physicists inadvertently stoked such anxieties when they published a theory that ordinary matter could turn into a new substance they dubbed "strange matter," if subjected to enough energy and pressure. Depending on its properties, strange matter might transform everything it touched, eliminating the world as we know it. Andreas Bauswein, a physicist at the Heidelberg Institute for Theoretical Studies in Germany, is sufficiently intrigued by the idea of strange matter that he is actively hunting for it. Even if he finds convincing evidence, though, he doesn’t think strange matter would pose much of a threat. “Earth has existed for billions of years being exposed to highly energetic particles from cosmic rays,” he says. Bauswein thinks the most likely place to find strange matter isn’t on this world but on ultra-dense stellar corpses known as neutron stars. Conditions on such objects might be extreme enough to turn them into “strange stars.” If two strange stars then happened to collide, Bauswein says, the resulting explosion would have a distinctive appearance. Related SCIENCE Why some scientists say physics has gone off the rails The Einstein Telescope, a gravitational wave observatory that might be built in the 2020s, could reveal whether there’s any basis for the strange theory. “It would precisely provide the sensitivity to say whether a merger involved strange matter or not,” Bauswein says. Fortunately, there are no potential strange stars anywhere close to Earth, so we should be nicely out of harm’s way. Verdict: Strange matter is not going to kill us, but it might elucidate the essential nature of matter. The big suck Death by black hole seems more likely than death by strange matter, since it’s well established that black holes are real. The nearest known black hole lies less than 3,000 light-years from Earth, hardly farther than some of the stars you see at night. Microscopic black holes of the sort Rees describes are another matter. For now, they’re only a matter of conjecture. Starting in 2001, Brown University physicist Greg Landsberg theorized that the LHC might create such micro-black holes. Perverse as it sounds, he was actually hoping for that to happen. “The original thought was that such a black hole will very quickly evaporate,” he says. The result would be a distinctive blast of particles that could provide unique information about gravity and how it relates to the other natural forces. To Landsberg’s disappointment, the LHC has found no signs of micro-black holes. “Most likely, the models that predicted them being within the LHC reach are simply not realized in nature,” he says. But then he adds a caveat: It’s also conceivable that the micro-black holes are there, but we don’t understand how to detect them. Recommended CLIMATE IN CRISIS Heat, flooding and smoke: The U.S. is in the midst of a summer of extremes SCIENCE NEWS A weekend of misery ahead for millions in the U.S. as record heat takes hold The idea that unseen micro-black holes could be floating around may seem unsettling, but Landsberg, too, brushes aside any concerns. “If there was a chance that such a collision would create a black hole that lives long enough to accrete matter around it, we would see an abundance of black holes in the universe far exceeding what we observe,” he says. Verdict: The only way you’d ever get swallowed up by a black hole would be if you made a long trip on an interstellar spacecraft. Caught in a cosmic breakdown Strange matter and black holes are nothing compared to a collapse of the vacuum, which would destroy not only our planet but the laws of physics as we know them — the ultimate doomsday. Katie Mack, a physicist at North Carolina State University, has described it as “a quick, clean and efficient way of wiping out the universe.” The idea goes like this: Empty space isn’t truly empty but is full of energy associated with the fields and particles that define the universe. If this energy exists in an unstable state (known as a “false vacuum”), Mack explains, then it could abruptly change into a different form. Vacuum collapse would be like a lake icing over on a winter night. The transformation would begin in one spot and spread until everything was frozen — only in the case of the false vacuum, the thing spreading would not be ice but a new type of space embodying new laws of physics. Once the vacuum began to collapse at some location, the theory goes, the disturbance would travel outward in all directions, destroying everything it touches. As with strange stars and black holes, any breakdown in the vacuum is probably out of human control. “There's no mechanism we're aware of by which a particle experiment could reach the extreme energies where anything like that could happen,” Mack says, since cosmic rays a billion times as powerful as anything at the LHC clearly haven't shredded the universe. Offering some further vague comfort, she notes that “vacuum decay is highly uncertain, as in, we don't know yet if it’s even possible.” Rees raises the same idea in his book, citing such uncertainties as reason to proceed with caution in our physics experiments. But if the primary risks come from nature itself — as the physics insiders almost uniformly conclude — then the only way to size them up is by studying them. In that vein, Mack hopes research at the LHC and its successors will lead to important insights about how the vacuum works and whether it truly could collapse."To me vacuum decay is the most interesting way to go," she says. One thing for certain: If it does happen, you won't have time to fret about it. Vacuum decay would move at the speed of light, so it would arrive without warning. The moment you see it is also the moment you die.

SCIENTISTS have discovered black holes are easier to create than previously thought, meaning the Large Hadron Collider’s (LHC) super-sized successor will be powerful enough to spawn one. By SEAN MARTIN 06:05, Sun, Jul 16, 2017 | UPDATED: 21:55, Sun, Jul 16, 2017 0BOOKMARK What is the Large Hadron Collider? The existing LHC is already a whopping 27 kilometres in length but the next one will range from 80 to 100 kilometres, it has been revealed. The LHC 2.0, or Future Circular Collider (FCC), will revolutionise the world of physics when it is up and running, and build on the work of its predecessor. It will produce the power of 10 MILLION lightning strikes - enough energy to create a devastating black hole. Researchers have discovered that it actually takes 2.4 times less energy to create a black hole, and with a more powerful particle collider, some fear that one could be accidentally made in the lab. A black hole requires less energy than previously thought When particles smash into one another, their gravitational pull is trapped, meaning researchers could make one at the LHC 2.0. If enough energy is contained between those particles, it can collapse that could create two black holes that quickly merge into one.

Time travel into the future is not only possible but commonplace in the OA Universe (relativistic travel, nanostasis, etc.). Unfortunately, this is a one-way journey. Here is one answer why we don't have time travel into the past in the OA universe.

Why Time Travel Would Destroy the Universe

In the movies, time travelers typically step inside a machine and—poof—disappear. They then reappear instantaneously among cowboys, knights or dinosaurs. What these films show is basically time teleportation. Scientists don’t think this conception is likely in the real world, but they also don’t relegate time travel to the crackpot realm. In fact, the laws of physics might allow chronological hopping, but the devil is in the details. Time traveling to the near future is easy: you’re doing it right now at a rate of one second per second, and physicists say that rate can change. According to Einstein’s special theory of relativity, time’s flow depends on how fast you’re moving. The quicker you travel, the slower seconds pass. And according to Einstein’s general theory of relativity, gravity also affects clocks: the more forceful the gravity nearby, the slower time goes. ADVERTISEMENT “Near massive bodies—near the surface of neutron stars or even at the surface of the Earth, although it’s a tiny effect—time runs slower than it does far away,” says Dave Goldberg, a cosmologist at Drexel University. If a person were to hang out near the edge of a black hole, where gravity is prodigious, Goldberg says, only a few hours might pass for them while 1,000 years went by for someone on Earth. If the person who was near the black hole returned to this planet, they would have effectively traveled to the future. “That is a real effect,” he says. “That is completely uncontroversial.” Going backward in time gets thorny, though (thornier than getting ripped to shreds inside a black hole). Scientists have come up with a few ways it might be possible, and they have been aware of time travel paradoxes in general relativity for decades. Fabio Costa, a physicist at the Nordic Institute for Theoretical Physics, notes that an early solution with time travel began with a scenario written in the 1920s. That idea involved massive long cylinder that spun fast in the manner of straw rolled between your palms and that twisted spacetime along with it. The understanding that this object could act as a time machine allowing one to travel to the past only happened in the 1970s, a few decades after scientists had discovered a phenomenon called “closed timelike curves.” “A closed timelike curve describes the trajectory of a hypothetical observer that, while always traveling forward in time from their own perspective, at some point finds themselves at the same place and time where they started, creating a loop,” Costa says. “This is possible in a region of spacetime that, warped by gravity, loops into itself.” “Einstein read [about closed timelike curves] and was very disturbed by this idea,” he adds. The phenomenon nevertheless spurred later research. ADVERTISEMENT Science began to take time travel seriously in the 1980s. In 1990, for instance, Russian physicist Igor Novikov and American physicist Kip Thorne collaborated on a research paper about closed time-like curves. “They started to study not only how one could try to build a time machine but also how it would work,” Costa says. Just as importantly, though, they investigated the problems with time travel. What if, for instance, you tossed a billiard ball into a time machine, and it traveled to the past and then collided with its past self in a way that meant its present self could never enter the time machine? “That looks like a paradox,” Costa says. Since the 1990s, he says, there’s been on-and-off interest in the topic yet no big breakthrough. The field isn’t very active today, in part because every proposed model of a time machine has problems. “It has some attractive features, possibly some potential, but then when one starts to sort of unravel the details, there ends up being some kind of a roadblock,” says Gaurav Khanna of the University of Rhode Island. newsletter promo Sign up for Scientific American’s free newsletters. Sign Up For instance, most time travel models require negative mass—and hence negative energy because, as Albert Einstein revealed when he discovered E = mc2, mass and energy are one and the same. In theory, at least, just as an electric charge can be positive or negative, so can mass—though no one’s ever found an example of negative mass. Why does time travel depend on such exotic matter? In many cases, it is needed to hold open a wormhole—a tunnel in spacetime predicted by general relativity that connects one point in the cosmos to another. Without negative mass, gravity would cause this tunnel to collapse. “You can think of it as counteracting the positive mass or energy that wants to traverse the wormhole,” Goldberg says. ADVERTISEMENT Khanna and Goldberg concur that it’s unlikely matter with negative mass even exists, although Khanna notes that some quantum phenomena show promise, for instance, for negative energy on very small scales. But that would be “nowhere close to the scale that would be needed” for a realistic time machine, he says. These challenges explain why Khanna initially discouraged Caroline Mallary, then his graduate student at the University of Massachusetts Dartmouth, from doing a time travel project. Mallary and Khanna went forward anyway and came up with a theoretical time machine that didn’t require negative mass. In its simplistic form, Mallary’s idea involves two parallel cars, each made of regular matter. If you leave one parked and zoom the other with extreme acceleration, a closed timelike curve will form between them. Easy, right? But while Mallary’s model gets rid of the need for negative matter, it adds another hurdle: it requires infinite density inside the cars for them to affect spacetime in a way that would be useful for time travel. Infinite density can be found inside a black hole, where gravity is so intense that it squishes matter into a mind-bogglingly small space called a singularity. In the model, each of the cars needs to contain such a singularity. “One of the reasons that there's not a lot of active research on this sort of thing is because of these constraints,” Mallary says. Other researchers have created models of time travel that involve a wormhole, or a tunnel in spacetime from one point in the cosmos to another. “It's sort of a shortcut through the universe,” Goldberg says. Imagine accelerating one end of the wormhole to near the speed of light and then sending it back to where it came from. “Those two sides are no longer synced,” he says. “One is in the past; one is in the future.” Walk between them, and you’re time traveling. You could accomplish something similar by moving one end of the wormhole near a big gravitational field—such as a black hole—while keeping the other end near a smaller gravitational force. In that way, time would slow down on the big gravity side, essentially allowing a particle or some other chunk of mass to reside in the past relative to the other side of the wormhole. ADVERTISEMENT Making a wormhole requires pesky negative mass and energy, however. A wormhole created from normal mass would collapse because of gravity. “Most designs tend to have some similar sorts of issues,” Goldberg says. They’re theoretically possible, but there’s currently no feasible way to make them, kind of like a good-tasting pizza with no calories. And maybe the problem is not just that we don’t know how to make time travel machines but also that it’s not possible to do so except on microscopic scales—a belief held by the late physicist Stephen Hawking. He proposed the chronology protection conjecture: The universe doesn’t allow time travel because it doesn’t allow alterations to the past. “It seems there is a chronology protection agency, which prevents the appearance of closed timelike curves and so makes the universe safe for historians,” Hawking wrote in a 1992 paper in Physical Review D. Part of his reasoning involved the paradoxes time travel would create such as the aforementioned situation with a billiard ball and its more famous counterpart, the grandfather paradox: If you go back in time and kill your grandfather before he has children, you can’t be born, and therefore you can’t time travel, and therefore you couldn’t have killed your grandfather. And yet there you are. Those complications are what interests Massachusetts Institute of Technology philosopher Agustin Rayo, however, because the paradoxes don’t just call causality and chronology into question. They also make free will seem suspect. If physics says you can go back in time, then why can’t you kill your grandfather? “What stops you?” he says. Are you not free? Rayo suspects that time travel is consistent with free will, though. “What’s past is past,” he says. “So if, in fact, my grandfather survived long enough to have children, traveling back in time isn’t going to change that. Why will I fail if I try? I don’t know because I don’t have enough information about the past. What I do know is that I’ll fail somehow.” ADVERTISEMENT If you went to kill your grandfather, in other words, you’d perhaps slip on a banana en route or miss the bus. “It's not like you would find some special force compelling you not to do it,” Costa says. “You would fail to do it for perfectly mundane reasons.” In 2020 Costa worked with Germain Tobar, then his undergraduate student at the University of Queensland in Australia, on the math that would underlie a similar idea: that time travel is possible without paradoxes and with freedom of choice. Goldberg agrees with them in a way. “I definitely fall into the category of [thinking that] if there is time travel, it will be constructed in such a way that it produces one self-consistent view of history,” he says. “Because that seems to be the way that all the rest of our physical laws are constructed.” No one knows what the future of time travel to the past will hold. And so far, no time travelers have come to tell us about it.