Stephen Hawking’s warnings about humanity’s prospects have re-entered the spotlight after new research into the far-future death of the cosmos concluded the universe could go dark far “sooner” than earlier estimates, and media recirculated the physicist’s 2017 claim that Earth could become uninhabitable within a few centuries if population and energy use keep rising unchecked. The two strands are distinct—one about the physical fate of the universe on unimaginable timescales, the other about choices facing people on Earth this millennium—but together they have revived attention to Hawking’s blunt formulations about risk and time. In a video address to the Tencent WE Summit in Beijing on 5 November 2017, Hawking said exponential growth “cannot continue into the next millennium,” adding: “By the year 2600, the world’s population would be standing shoulder to shoulder, and the electricity consumption would make the Earth glow red-hot.” He called that scenario “untenable” and urged investment in projects such as Breakthrough Starshot to push toward interstellar capability as a long-term hedge.
The Beijing appearance was one of several occasions in which Hawking compressed broad scientific concern—climate change, resource strain, pandemics and the possibility of nuclear conflict—into a single image meant to land with the public. He had been voicing versions of the same message for years, oscillating between thousand-year horizons and, later, a much tighter time frame for moving beyond Earth. In 2016 he told the BBC’s Radio Times that the chance of a global catastrophe would compound over the “next thousand years,” but that human dispersal into space would mitigate extinction risk. Months later, in 2017, he argued that humans should plan to “find a new planet to live on within 100 years,” framing the next century as a period in which Earth would require “great care” while spacefaring capability remained limited. The rhetorical shift was deliberate: a communication strategy to force urgency rather than a dated, literal countdown.
The resurfacing this week of Hawking’s 2017 “red-hot Earth” line—picked up by outlets summarising his remarks as an “end of the world” prediction—coincided with peer-reviewed work that tightens estimates for the universe’s ‘heat death’ by incorporating a subtle effect often associated with Hawking’s own name: Hawking-like radiation. A Dutch team calculated in May that when this form of radiation is included not just for black holes but for long-lived stellar remnants, the final fading of the cosmos could occur around 10^78 years from now—astronomically sooner than older back-of-the-envelope numbers that stretched to 10^1100 years. The revision does not alter human timescales; it replaces one number incomprehensibly beyond human experience with another that is still incomprehensibly beyond human experience. But the phrase “sooner than expected” attached to the study helped pull Hawking’s Earth-bound warnings back into circulation, even though he was not making predictions about cosmological endgames in 2017.
Hawking’s Beijing remarks were anchored in a specific, dramatic illustration of exponential growth. He pointed out that population growth at rates common in the late 20th century would, if sustained, lead to absurd crowding within centuries, and that the energy required to support such a population—when converted into waste heat—would raise planetary temperatures to catastrophic levels. The scenario was tied to a slide of a flaming Earth he used to underline the point. The line traveled because it distilled a tangle of variables—energy mix, efficiency gains, demographic transitions—into an easily grasped image. It also attached to a concrete call: support for Breakthrough Starshot, a privately funded effort he backed to test whether wafer-thin, laser-pushed “starchips” could, one day, cross interstellar distances.
Critics at the time said the “standing shoulder to shoulder” illustration took a rhetorical shortcut through contested forecasts. Some demographers noted that global fertility had already fallen sharply and that the world’s population growth was decelerating, with projections showing flattening or eventual decline later this century in many regions. Energy economists pointed out that total energy demand could decouple from GDP growth if efficiency and low-carbon technologies scaled fast enough, changing the waste-heat calculation Hawking popularised. Supporters countered that the argument did not depend on exact rates; it was a warning that physical limits bind exponential curves, and that the window to avoid climate and resource shocks is measured in decades, not millennia. Hawking himself had made both points across different platforms: temper Earth-side risks as much as possible and accelerate off-world options to diversify the species’ footprint.
The physicist’s repertoire of risks was broader than the single “fireball” image suggests. He repeatedly cited nuclear war, engineered pandemics and poorly aligned artificial intelligence as non-trivial threats that could make the 21st and 22nd centuries unusually precarious. That list evolved as the public conversation shifted. In 2015–2017 he lent his name to open letters on AI safety, warned about climate feedbacks that could “turn our planet into Venus,” and spoke with unusual directness about the political incentives that keep emissions high. The specific calendar dates in his interviews varied, but the through-line was steady: the probability of a civilisation-ending event in any given year may be small, but integrated over centuries it becomes significant; the way to keep the cumulative risk tolerable is to shrink the annual hazards and spread the existential eggs across more than one basket.
Media outlets that revived Hawking’s 2017 talk this month paired it with a second “sooner than we thought” headline unrelated to human timelines: the recalculated schedule for the universe’s final darkness. In those studies, physicists estimate how long degenerate stellar remnants—white dwarfs—take to evaporate via quantum effects analogous to Hawking radiation. The new work argues that when such effects are accounted for, the longest-lived embers of the cosmos wink out far earlier than older estimates suggested. Scientific American and CBS/AFP made the same point in plainer language: the end is “much sooner,” but still so distant that it has no bearing on planetary policy. The result is a journalistic collision of scales, with a human-centred warning squeezed into the same frame as a revision in a number with 78 zeros.
Hawking’s name is attached to both conversations for different reasons. The heat-death work leans on a phenomenon—Hawking radiation—he discovered in 1974, in which black holes slowly lose mass by emitting particles from quantum fluctuations just outside the event horizon. The 2025 papers generalise a related idea to the very long tail of cosmic evolution, suggesting that even objects that are not black holes ultimately decay away through similar processes. Meanwhile, the Earth-side warning reprises his role as a public scientist willing to make bald statements to drag remote-seeming risks into the present tense. Where the first is an impersonal calculation, the second is a challenge: what shape will human systems take by 2100, 2200 or 2600, and who chooses it? (Phys.org)
On the historical record, Hawking alternated between pragmatic caution and provocation. In 2016 he said space colonies were unlikely “for at least the next 100 years,” urging people to treat Earth with “great care” in the meantime. A year later, he collapsed his outer time horizon for leaving Earth to a single century, not because he believed fusion drives and terraforming were imminent, but because he wanted audiences to internalise the idea that the margin for error had narrowed. He was acutely aware that physics alone would not determine the outcome; politics, technology, culture and luck would. “In a world that is in chaos politically, socially and environmentally,” he had written a decade earlier in a public prompt, “how can the human race sustain another 100 years?” The point of the question was not the number; it was to force an answer.
As the 2017 clip re-circulated, coverage again linked Hawking’s “fireball” line to Breakthrough Starshot, a programme he fronted with investor Yuri Milner and others to test light-sail propulsion at laboratory scale. The pitch then was to aim ultimately at Proxima Centauri, 4.2 light-years away, sending gram-scale probes at a fraction of light speed to sample an exoplanetary system in a single human lifetime. The underlying logic had two parts: build basic competence for moving data across interstellar distances, and pair that long bet with near-term emissions cuts and adaptation on Earth. The first was inspirational and speculative; the second was immediate and technically mature.
The durability of Hawking’s end-of-Earth image also reflects the way audiences process risk. A projection that civilisation could be tested severely within 500 years does not map onto normal political cycles, but it touches something recognisable in debates over coastlines, heatwaves, migration and food systems already under stress. By translating compound abstract threats into a single heat-waste picture, he gave editors an accessible hook and policymakers a reminder that arithmetic is unforgiving. The criticism that his “shoulder to shoulder” thought experiment oversimplified population dynamics is fair; the counter-criticism, that a world of ten or eleven billion will thrive only if it dramatically retools its energy and land use, is also fair. Hawking’s trick was to force those two realities into the same sentence.
Against that backdrop, the fresh “sooner than thought” cosmology headlines risk being misread as updates to his Earth warnings. They are not. The Radboud-led calculations, amplified by general-audience explainers, adjust a number for the universe’s end state without changing the human calendar. What they share with Hawking’s 2017 line is rhetorical punch. In both cases, the underlying message is scale: our species’ window to manage self-inflicted risks is tiny against cosmic time, but large enough to matter to billions now alive and to those who will inherit whatever energy, climate and biosphere choices we make this century.
Hawking’s legacy in this area is not a date; it is a set of priorities. Reduce greenhouse-gas emissions quickly to limit warming. Manage technologies with dual-use potential—pathogen engineering, AI, cyberweapons—with governance commensurate to their reach. Build redundancy in food, energy and information systems to buffer against shocks. Expand scientific literacy so that public debates can handle exponential processes without stalling in caricature. And, over the long haul, treat space not as a fantasy escape hatch but as an additional layer of resilience and discovery once the basics at home are stabilised. His apocalyptic metaphors were the noisy part; the core was pragmatic.
The renewed interest in his warnings reflects a media habit of clustering disparate “end-times” stories under a single banner. But the documentation is clear. In Beijing in 2017, pressing for urgency, he said exponential growth of population and energy use could make Earth uninhabitable by 2600 and argued that the arc of technological capability should bend toward both Earth stewardship and, eventually, interstellar reach. In May 2025, physicists published calculations suggesting the universe’s embers go out at 10^78 years rather than far, far later. One speaks to policy choices this century and next; the other to physics in a future effectively beyond imagination. The only common thread is the reminder Hawking returned to repeatedly: time is not on our side if we treat risks as abstract. The calendar that matters is the one inside which emissions either fall or rise, cities either adapt or fail, and institutions either plan for compounding shocks or pretend the curves are linear.
If Hawking’s phrasing feels “alarming,” that was the point. He was a theorist who spent a lifetime working at scales most people never consider, translating them back into human terms with a comedian’s sense of when to shock. The shock survives because it compresses what is scientifically routine—exponential growth, energy conservation, radiative forcing—into a story about the lives of people who will live and die under policies chosen in the present. In that sense, nothing about the “end of the world” is coming sooner than he thought; the urgency was always in the near-term decisions he wanted the public to face. The cosmological coda only underlines the contrast: the universe can wait 10^78 years. People cannot wait another electoral cycle to decide how hot the only home we have will run.