Some regularly recurring End of Time or Doomsday scenarios in brief.

The revenge of Mother Earth

James Lovelock (1919 -) described the Gaia hypothesis, in which he states that the Earth itself acts as a kind of superorganism.

He speaks as a planetary doctor whose patient, the living earth, is complaining of fever, caused by the plague of humanity. He sees the deteriorating health condition of the earth as our biggest concern, because our lifes depend on it.
Among others with Daisies World, he makes it clear that living organisms not only adapt to their environment, but also affect the environment to their advantage.
He wrote also: Gaia a New Look at Life on Earth, and The Revenge of Gaia.
Mother Earth who its hurted and maimed, would be able to take revenge on humanity by eradicating mankind on long term.
Many cultures see the planet as well as Mother Earth.

I actually find it a charming idea. It reminds to being one with nature, talk to trees... The mess we make will probably have an effect on the whole system.
The Earth has the advantage of time, she's not looking at 100,000 years. So, who knows?
I will definitely never come to know.


All in a row

A constellation is a related positioning of stars.
The precession (of the equinoxes) is the spinning motion that the earth makes relative to its own axis. It takes just under 26,000 years and ensures that the sky every 72 years shifts a degree in the arch of heaven. Compare it with a spinning top that does not stay in place and fluctuates somewhat, the axis moves in a circular motion on the floor.
A (big) conjunction means that all (or more) planets (and moons) are in a row (or perpendicular to each other).

In theory, the gravitational fields can then amplify each other. As a result, stronger tides on Earth are possible.
Some believe that it is possible that such strong gravitational fields can interfere with the magnetic field of the Earth, leading to catastrophes such as earthquakes, tsunamis, shifting of the poles. If it would have been possible that all our planets are exactly one line with the sun.

On May 5, 2000 were Earth, Sun, Moon, Mercury, Venus, Mars, Jupiter and Saturn in one line.
(Source: http://www.etsu.edu/physics/etsuobs/starprty/22099dgl/planalign.htm)
When the world is probably perished.
The book “The Jupiter effect“ was a bestseller in 1974. It explained how on March 10, 1982 the world would end because all the planets would be align. Ditto.



Pole shift

A pole shift should be a sudden and catastrophic shift of the poles.
No geographical flip over which turns the earth upside down, but the direction of the earth's magnetism is reversed. That's happened in the past more than once.
The magnetic field of the earth is probably caused by currents in the molten metal deep into the core of our planet. Those currents are also affected by the magnetic field themselves, which causes complex interactions may occur. As a result, the magnetic field varies continuously. The exact position of the magnetic pole is shifting continuously. A polarity reversal can be within a relatively short time.

Recent computer simulations showed a reversal that lasted about 1,200 years, but the average is probably around 7,000 years. A flash in the cosmos, but no further catastrophe on a human time scale.
During the reversal is probably the magnetic field weaker than normal, and are we maybe more vulnerable to solar storms.