The chilling premise of the upcoming science fiction blockbuster Project Hail Mary—a mysteriously dimming sun threatening all life on Earth—might feel like pure Hollywood fantasy. However, scientists have now revealed the terrifyingly real consequences we would face if our star's light began to fade.
The film, based on Andy Weir's novel and set for release in March 2026, follows a lone scientist, played by Ryan Gosling, on a desperate mission to uncover why the sun is losing its power. The plot hinges on a prediction that the sun's brightness will fall by one per cent in a single year and five per cent over two decades.
The Terrifying Science Behind a Dimming Sun
Currently, the sun delivers a steady stream of energy to our planet—approximately 1,365 Watts per square metre, a figure scientists call the solar constant. This energy is vital, with about 70% being absorbed to warm our atmosphere and surface. The delicate balance between energy gained and lost keeps our planet habitable.
Professor Lucie Green, a solar expert from University College London, explains that while the sun's output does naturally vary, the changes are minimal. "The Sun does naturally vary in brightness, but not by very much!" she told the Daily Mail. These fluctuations, linked to the 11-year sunspot cycle, are barely noticeable on Earth.
However, history shows that even small changes can have dramatic effects. Between 1645 and 1715, a period known as the Maunder Minimum where solar activity dropped by just 0.22 per cent, the Earth experienced the Little Ice Age. Temperatures in Northern Europe fell by up to 2°C (3.6°F), leading to crop failures and the collapse of Norse colonies in Greenland.
Catastrophic Consequences for Humanity
If the Project Hail Mary scenario came true, the consequences would be swift and devastating. As Earth began losing more heat to space than it gained from the sun, global temperatures would plummet.
The cascade of disaster would begin quickly:
- A drop of just 0.6°C (1.1°F) would cause crops to fail across Europe due to a lack of warm weather.
- By the time temperatures fell by 2°C (3.6°F), widespread famine could kill billions of people.
- A recent study suggests that global cooling of 1.8°C (3.25°F) alone could cause a 11 per cent drop in the production of key crops like maize and wheat, potentially killing 5.3 billion people in just two years.
Professor David Stevenson, a planetary scientist from Caltech, starkly noted that while extinguishing all life would take time, "extinguishing humans could happen fast, especially since humans are not rational creatures for the most part."
The Path to a New Ice Age and Human Extinction
In the film, Ryan Gosling's character warns that the dimming would trigger an "instant ice age." Scientists confirm this is not an exaggeration. According to research from the University of Arizona, the last Ice Age, 20,000 years ago, was only 6°C (10.8°F) colder than today. Glaciers covered half of North America, Europe, and parts of Asia at that time.
Dr Becky Smethurst, an astrophysicist at the University of Oxford, states that a one per cent drop in solar energy would be enough to "trigger a new Ice Age on Earth, with the polar ice caps expanding further towards the equator." She adds that while humans might survive using modern technology, perhaps by living underground, ecosystems would collapse and farming would fail.
If the sun were to go out completely, the end would be swift and absolute. Within a week, surface temperatures would fall below -18°C (0°F). Within a year, they would plunge to -73°C (-100°F). All plant life would die without light for photosynthesis, eliminating our oxygen supply. Dr Alexander James of UCL concludes, "I don’t see how the majority of life as we know it would be able to survive without our Sun."
Could This Really Happen?
Thankfully, scientists offer a strong dose of reassurance. The scenario depicted in Project Hail Mary is scientifically implausible. The sun is too massive and stable to cool so rapidly.
Professor Michael Lockwood, a space environment physicist from the University of Reading, provides a compelling comparison: "About half of the Sun's mass is in the radiative and convection zones outside the core... This enormous mass acts like a heat sink." He calculates that even if the sun's core stopped producing energy entirely, "the power emitted by the Sun would only have dropped by about one per cent a million years later." He firmly states that anything faster "is nonsense."
While we can eagerly anticipate the on-screen drama of Project Hail Mary, we can rest easy knowing that the stability of our sun is not in question. Sending Ryan Gosling on a space mission to save us, for now, remains firmly in the realm of fiction.
