The Sun provides Earth with light and heat that are essential for life as we know it. But what would happen if the Sun suddenly disappeared? How long could life on Earth persist without our nearest star?
How does the Sun support life on Earth?
The Sun is the source of nearly all energy on Earth. Here are some of the key ways the Sun enables life:
- Light – Sunlight powers photosynthesis in plants and phytoplankton, which provide the foundation for ecosystems and atmospheric oxygen.
- Heat – Solar radiation warms the planet’s surface and atmosphere to livable temperatures.
- Energy source – Solar energy drives winds, ocean currents, the water cycle, and weather.
- Vitamin D – Sun exposure enables vitamin D production in many organisms.
- Protection – The Sun’s magnetic field shields Earth from cosmic radiation.
Without the Sun, these critical functions would be lost, and life as we know it could not exist on Earth long-term.
What would happen immediately after the Sun vanished?
If the Sun instantly disappeared, the first change on Earth would be darkness. With no sunlight, vision-reliant organisms would be rendered blind. Photosynthetic life like plants and phytoplankton would shut down immediately with no light for photosynthesis.
Within minutes, Earth’s surface would start rapidly cooling due to the loss of incoming solar radiation. In the deepest parts of the oceans, the temperature change might not be felt for years, but the outermost layers would cool quickly.
Weather and winds driven by solar heating would die down rapidly. Huge storms and catastrophic winds could occur as atmospheric circulation patterns are disrupted by the abrupt temperature changes.
Eventually, the sky would appear dark, though some light from stars would still be visible. But the phases of the Moon would look the same, since the Moon reflects sunlight.
Surface temperature changes
Without the warming effect of the Sun, Earth’s average surface temperature would plummet. Some estimates for the drop in global average surface temperature without the Sun are:
- 5°C drop in the first week
- 20°C drop in one year
- Over 100°C drop in a decade
This extreme cooling would make most of Earth uninhabitable for current ecosystems.
How long could life survive without the Sun?
Most plant and phytoplankton species would perish within weeks without sunlight. The loss of these photosynthetic organisms would disrupt the base of the food chain.
Herbivores and omnivores relying directly or indirectly on plants for food would soon follow. Top predators would last longer with other animal species to hunt, but eventually die off as the biosphere becomes depleted.
However, some life could persist longer in niche environments independent of sunlight and photosynthesis. Here are a few organisms that could survive:
Underground and deep sea organisms
- Fungi – Certain fungi can survive without sunlight.
- Worms and burrowing animals – Could persist underground.
- Tube worms and other deep sea creatures near hydrothermal vents – Can harness chemical energy rather than sunlight.
- Bacteria and archaea – Some can derive energy from minerals and chemical reactions.
These organisms could survive for years underground and in the deep oceans, though likely not indefinitely.
Extremophiles
Some microorganisms can withstand extreme cold, such as:
- Psychrophiles – bacteria that can live in icy environments.
- Tardigrades – Microscopic water bears can survive freezing.
These types of “extremophiles” could persist longer than other organisms in the freezing temperatures.
Conclusion
Most experts estimate complex life could only survive for a few months globally without sunlight. Some microbes could persist longer by harnessing geothermal energy or existing in frozen states. But without a steady external energy source, even these lifeforms could not survive indefinitely. The complete loss of the Sun would eventually result in the extinction of all life on Earth over the course of years to decades.
How would losing the Sun affect Earth itself?
Without the Sun’s energy input, some drastic changes would occur to Earth itself:
Freezing oceans
- The surfaces and shallower waters of the oceans would start freezing within weeks.
- After a few months, ocean freezing would spread downwards.
- Around 1-3 years without the Sun, the oceans could be completely frozen over 1-2 km deep.
This freezing would devastate ocean life, and the ice coverage would dramatically change coastlines.
Atmospheric changes
- Most of the atmosphere would condense and freeze without the Sun’s warmth.
- Nitrogen and oxygen would form “snow” and deposit onto the surface.
- The air pressure at sea level could eventually reach only 1% of current levels.
- Toxic gases like methane and ammonia, no longer cycled by life forms, could accumulate in the remaining atmosphere.
Earth would become a cold, dry world largely devoid of air and liquid water.
Orbital changes
- Without the Sun’s gravity, Earth’s orbit would no longer be stable.
- It would likely start veering off into space or falling towards the center of the galaxy.
- Earth’s tilt and rotation would also become irregular without the Sun’s stabilizing influence.
What would happen if the Sun instantly reappeared?
If the Sun instantly switched back on after an extended blackout period, could life and a habitable Earth recover?
For blackout periods of a few months, recovery would be relatively swift. Ecosystems could restart, and ocean and air temperatures would bounce back over following months.
But after years to decades without the Sun, recovering Earth’s habitability becomes more questionable. Problems include:
- With oceans frozen over a kilometer deep, thawing would take thousands of years.
- Carbon dioxide levels may not return to normal for millions of years due to loss of photosynthesis.
- Toxic gases accumulated in the atmosphere could require eons to be fixed by biodiversity.
- Most existing species have perished, requiring evolution to produce complex new life.
Astrophysicists theorize the Sun formed around 4.6 billion years ago, and has enough hydrogen fuel to continue burning for a total of 10 billion years. So while Sun-like stars can endure, planets and life dependent on them are fragile. Losing the Sun, even temporarily, would irrevocably damage Earth’s habitable environment developed over billions of years.
Conclusion
The complete loss of the Sun would unleash an extinction catastrophe on Earth. Most plant and animal species would perish within weeks to months, and the planet would go into a severe deep freeze. Some microbes could endure below frozen oceans for years, but all life requires energy, so no organisms could survive indefinitely cut off from sunlight.
While Earth itself would endure as a frozen body, its habitable environment allowing complex biospheres would be irreparably lost within years without the steady energy output from the Sun. Appreciating the vital role the Sun plays in making our planet livable for any duration helps underscore why habitable worlds seem to be exceptionally rare across the universe.