Galaxies would stop moving away from us

How the world will really end

Galaxy collision

Even if one assumes that humanity will not destroy itself at some point - the end is sure to come. Astrophysics tells us when and how definitely all life will end.

The first major event of astronomical importance to affect Earth is the collision of our home galaxy Milky Way with the neighboring galaxy Andromeda. NASA predicts that the two galaxies will collide head-on in about four billion years. The relative speed is around minus 400,000 kilometers per hour. Andromeda is racing towards our galaxy at this speed.

Astronomers were able to determine these data precisely by taking measurements with the Hubble telescope. According to the prediction, the meeting will look like this: First, both galaxies will cross each other. The result is a large elliptical galaxy that swings around a common center of mass like a floating drop of water.

Even if that sounds destructive, only about a hundred of the many billions of stars in the Milky Way collide with objects from Andromeda. A very small number. So there is a high probability that nothing will happen to our solar system. A six in the lottery would be a lot more likely.

New night sky

On earth, however, people will see a new night sky. This then presumably consists of the new mixed galaxy (called "Milk Dromeda" by some). It is possible that the sun is drawn into a binary star system and the earth even orbits two suns.

That doesn't necessarily mean the end of the earth either. The only real danger is that Earth could get too close to another star or black hole. This would make planetary orbits unstable and, in the worst case, the earth could plunge into the sun. But this is also unlikely.

The end of the sun

The really crucial future of the earth lies in the stars. More precisely, in the future of stars like the sun. The sun gives us light and warmth - basic requirements for life on earth. But at some point the sun will also seal the end of life on earth.

In about five to seven billion years it will transform in spectacular ways. Their diameter increases, the luminosity increases. The planets closest to the Sun Mercury, Venus and Earth are destroyed.

The sun is a gigantic nuclear fusion reactor. It consists mainly of hydrogen. Inside, the pressure and temperature are so high that hydrogen atoms fuse together to form helium atoms. A tremendous amount of energy is released in the process.

After its hydrogen supply is exhausted, the sun puffs up. It will temporarily shine even more intensely: As a "red giant", a giant star, its luminosity will be twice as great at the age of around ten billion years as it is today.

However, it will no longer appear yellow, but red because it will be much cooler - hence the name "Red Giant". In the center of the sun, all hydrogen has been used up at this stage. What remains is a ball of helium.

As the sun expands, its corona will swallow the planets Mercury and Venus. The earth is not expected to be completely absorbed by the sun. Still, the conditions will make life on earth impossible. It will be more than 1000 degrees on the earth's surface. The earth is transforming into a desert planet, the surface of which will eventually consist of liquid rock.

Due to the decreasing mass of the sun, the attraction to the earth also disappears. So it escapes the sun a bit at first. However, life on earth will come to an end before that. Not only the high temperatures, but also the changed UV spectrum of the sun destroys every kind of life on earth.

How do you know? The sun was formed around five billion years ago. The Milky Way is eleven to twelve billion years old, the universe thirteen billion years. Other stars in the Milky Way are ten to eleven billion years old, six to seven billion more than our sun.

It is observed that stars with a mass similar to that of the Sun practically explode one after the other. This is the fate that threatens our sun as well - in five to seven billion years.

It's getting dark

Even if humanity escapes the death of the blue planet, colonizes another planet and survives - the end of the universe will not survive even the most technologically advanced civilization. Because the cosmos is expanding faster and faster.

In about 10¹³ years (that's a ten with thirteen zeros) the oldest stars known today will be burned out, because their fuel is also limited. In 10¹⁴ years normal star formation will come to an end.

That means: The universe is getting dark. Only burnt-out star remains are left: white dwarfs, neutron stars, black holes and the celestial bodies that cannot support fusion: brown dwarfs and planets. There are no more energy sources (such as the sun).

A civilization would then have to produce its own energy. Just heating up an artificial habitat to the ambient temperature (around minus 270 degrees Celsius) would consume unimaginable amounts of energy.

The end of the universe

But the real end of the universe takes place at the atomic level. We look 10³⁶ years into the future - a ten with 36 zeros. In this unimaginably distant future, matter will begin to dissolve: Physicists believe that the protons will then decay.

Matter consists of atoms, while atomic nuclei consist of protons and neutrons. Without protons there are therefore no atoms, no molecules, no cells and also no life. Matter as we know it no longer exists. The universe will be in a completely alien state. Only electrons, positrons and long-wave photons form the components of the universe.

Some theories predict that the universe will then contract again and there will be a new big bang. Others speak of an everlasting expansion. No matter what the future will look like, life in the universe will be impossible in ten to the hundredth of a year.