How Long Could We Survive if the Sun Disappeared Today?

And what would happen in the next hours, days and weeks?

The laws you would have to break

First of all, the Sun cannot just disappear without breaking numerous physical laws. That’s the problem of invoking magic — the instant you do it, all bets are off.

When you use your imagination to play with something that is not possible given the laws of physics, you also have to use your imagination to cherry pick what other laws of physics you wish to use, change or ignore.

For the gravity of the Sun to instantly disappear, the energy of the Sun would also need to instantly disappear, which would violate the laws of conservation of energy.

One rule of thumb is that you can’t expect the whole range of physics or human behavior to stay the same when one drastically important thing changes.

What other natural phenomena would be affected as a result of this and what other laws of physics would you have to break and what assumptions would you have to make?

But let’s speculate what would happen if the Sun magically vanished from the sky today. What would follow and how long could we expect to survive here on Earth?

Chaos in the solar system

If the Sun suddenly disappeared, Earth would keep on moving in a straight line tangent to the path it was originally moving when there was gravity from the Sun. You won’t feel a difference though because the gravity on Earth is still intact.

But all gravitationally bound objects in the sky (planets, moons, asteroids, comeths, rocks, spacedust and other celestial bodies) would begin to move away from their usual paths at roughly the same time.

Rogue planets could collide with thousands of other gigantic bodies, possibly leading to destruction and chaos, at least in a longer perspective.

Without our own moon the tilt of Earth’s axis would vary over time. This would lead to no seasons or even extreme seasons. The absence of the moon’s gravity would cause the tidal effect to vanish.

With no energy from the Sun the ocean streams will stop circulating. The winds will stop and hence the waves. With no Sun to power evaporation the rain will eventually stop, the clouds will disappear and rivers will stop flowing.

And the psychological effect of suddenly losing the parent star… This is like finding out that in a few days a gigantic asteroid will slam into Earth and wipe out all life. Can the consequences and people’s reactions be even remotely understood?

Sudden darkness will be observed on Earth already after a few minutes. The temperature would start to drop and that would make survival difficult and photosynthesis would stop immediately after the sunlight disappears.

All plants, animals and humans would be thrown into a spiraling death process, but how long would it take?

A possible timeline of the death process

T+0?(+15 deg C)

The Sun suddenly disappears from the sky and leaves no trace. Since gravitational waves, as shown in Einstein’s theory of general relativity in 1915, travel at the same speed as light waves it will take several minutes for us to notice the effects.

The average temperature on Earth is approximately +15 deg C.

T+8 minutes (+15 deg C)

The gravitational force field reaches Earth at the same time as the last light from the missing star. The instant lack of the Sun’s gravitational force will throw Earth into a straight line, tangential to the orbit.

Eternal night begins at the same time but the stars still shine, and electricity will continue to work and cities remain lit for as long as the power lasts. Even the planets will remain visible for a brief time since they are located further away.

If you’re on the side of the planet that’s facing away from the Sun (i.e. it’s nighttime), the moon would go dark too, as it would no longer have the Sun’s light to reflect.

The temperature starts to drop and photosynthesis stops immediately after the sunlight disappears. All plants will begin to die and 99% of all natural biodiversity on Earth will cease.

T+1 day (+10 deg C)

As soon as the Sun disappears the temperature will drop a few degrees (like it does every night). But our planet has stored enough heat in the atmosphere to keep us warm for a while. The temperature drop would be less severe and not as sudden as the shift to near darkness.

The stars still shine, and electricity will continue to work and cities remain lit for as long as the power lasts. But the light from all planets is gone from the sky.

By now the psychological effects have hit everyone. The Sun is gone and it won’t come back. Unless you are very young or demented you probably understand that this is the end of life. Panic and chaos are spreading much faster than the actual effects from the missing Sun.

T+1 week (-10 deg C)

Most small plants have died within a few days and the temperature keeps dropping. Trees, however, may survive for decades. The Earth itself would become sick with the sudden temperature change, and terrible blizzards would rage across the world.

Earth has a core of molten iron, and above that a mantle of molten rock. Some heat would filter through Earth’s crust, keeping it warmish for a time. But after a week the average temperature has dropped to around -10 deg C on average.

-10 deg C is a common temperature in some areas, especially during winter, but the 25 deg C temperature drop occurs everywhere on the planet and people will start to die already during the first days.

Some people could burn wood and coal for warmth and people in the northern hemisphere may be better prepared with warm clothes and other equipment.

There will be a lot of scrambling in the early days to grab stuff from the stores (natural refrigeration) and steal supplies to survive. After people settle down into compounds, the main source of work will be scavengers braving the cold to get more supplies.

All social functions have broken down within the first week.

T+1 month (-70 deg C)

The storms would eventually cease, maybe after the first month, and the weather would become much more stable across the globe. But almost all life on Earth is dead. The oceans are covered by a thin layer of ice.

Survivors must bury deep underground, or close to geothermal vents on the ocean floor. Humans may survive deep down in mines, in submarines or at the international space station. A few geothermal places like Iceland and Yellowstone may also be habitable for humans for a little longer.

T+1 year (-200 deg C)

Within a few months, the complete ocean’s surface has a thick ice layer, but it would take another thousand years for our seas to freeze solid. There’ll still be animals living in the water underneath, as ice acts as an insulator and Earth’s core will continue producing heat.

All creatures on the surface are dead except some large plants which may store energy in the form of polysaccharide Starch (complex mixture of amylose and amylopectin). The last survivor of the underground people is long gone as power broke down and all supplies went out.

T+ 10–20 years (-220 deg C)

Air turns into liquid, it will become cold enough for all the gasses in air to condense and form clouds. It rains, but instead of water there are gasses like Dihydrogen. Oxygen production has stopped with photosynthesis.

The atmosphere basically freezes and falls down to Earth, leaving our planet utterly exposed to the harmful radiation waves that roam through space. But there is no one left that can suffer from radiation damages.

In millions of years (-240 deg C)

There is still some sort of life on Earth. Microbes living in hydrothermal vents in deep oceans will do just fine. These microbes produce energy through Chemosynthesis — a process independent of Solar radiation.

The temperature stabilizes at -240 ℃ after millions of years.

Could we survive underground?

A few hundred survivors may perhaps move deep underground into existing mines. All sewage must be recycled, but the rain problem will disappear with the Sun.

Underground living could be comfortable, warm and safe, with minimal power consumption. The problem with power and air ventilation is possible to overcome in the short term.

To survive starvation, large food stores could be arranged down in the mine. Mushrooms may be cultivated easily enough, and begin to make up a large part of the diet as an economic food. But generating enough light to grow crops will be challenging. Without crops, most farm animals are useless.

So survivors would be eating mushrooms, and vitamin tablets, and eventually lab-grown yeasts and the like to make up for the dietary deficiencies. The most obvious and important deficiency is vitamin D, as they would no longer have the Sun.