In a candid interview earlier this year, Elon Musk, CEO of SpaceX and Tesla, warned that Earth’s long-term habitability is finite and reiterated his push to make humanity a multiplanetary species.
Speaking to Jesse Waters in May, Musk framed the issue in astronomical terms: with Earth roughly 4.5 billion years old, he estimated the planet may have only about 10% of its remaining habitable lifetime before changes to the Sun make it inhospitable. "Eventually, all life on Earth will be destroyed by the expanding sun," Musk said, suggesting that in roughly 500 million years rising temperatures could threaten life globally.
Mars As 'Life Insurance' — Musk has described settlement of Mars as a form of civilization-level insurance. SpaceX continues developing technologies to support that goal and has stated an ambition to land humans on Mars as early as 2029, with an ultimate aim of creating a self-sustaining outpost.
Demographics and Near-Term Challenges
While Musk's timeline emphasizes solar evolution over geological timescales, his argument also touches on immediate terrestrial challenges that affect humanity's future prospects — notably demographic change.
United Nations World Population Prospects project the global population, now near 8 billion, could peak around 10.3 billion by the mid-2080s and then stabilize or decline. Growth will be uneven: some regions such as parts of sub-Saharan Africa are expected to grow rapidly, while others face stagnation or shrinkage.
Japan’s Demographic Shift — Japan offers a striking example of an aging society. For more than a decade, sales of adult diapers in Japan have exceeded sales of baby diapers, a visible indicator of falling birth rates reported by Fortune. In 2023 Japan recorded just 758,631 births, according to the Nippon Communications Foundation — the lowest tally on record — while the elderly population continues to grow, placing strain on healthcare systems and the workforce.
Why It Matters
Demographic trends influence economic capacity, labor supply, and the long-term human capital available for ambitious projects, including space exploration. Musk and others argue that persistently low fertility could pose risks to civilization’s resilience — an argument that helps explain the urgency behind efforts to expand humanity’s presence beyond Earth.
"Occupy Mars" and "Mars will be green with life someday," Musk recently posted on X, underscoring his continued public advocacy for Mars exploration.
Whether driven by astronomical concerns or near-term social trends, the discussion highlights two linked themes: the long-term vulnerability of life on Earth and the short-term demographic shifts that shape our capacity to respond. Both factor into the debate over how and why humanity should invest in off-world settlements.
