|When do you think the world will end?
The sun will eventually become a red giant; it may
or may not envelop the Earth - if it does, the
Earth will be vaporized. Long before it does,
however, the heat from the luminous sun will cook
the planet until it is sterile, eventually melting
it. This will happen in about four billion years.
Long before that, however, the sun will become
bright enough that while it does not melt the
planet, it will cause climatic effects that will
make life impossible.We do not know how the
climate will respond to such increased solar
input, so we do not know how much the climate can
take before the sun cooks us. Our climatological
models aren't that good. Most climatologists seem
to think that it will be a few billion years.
The question of when the world will end is one
that can be answered on many levels.Since I am a
geologist, I am going to interpret your question
to mean, "When will the actual planet Earth cease
to be a planet?" There are two major methods by
which our planet can be destroyed; Evolution of
the sun into a red giant star or impact with a
giant extra-terrestrial body.
The sun is a star
that is in the middle of its life. In about 6
billion years the sun will have exhausted its
hydrogen in its core and will cease to create
helium by fusion. This will cause the sun to cool
enough that it will collapse under its own
gravity. As the sun collapses, the atoms inside
of the sun will be pulled closer together and will
collide with each other more frequently, creating
more heat and raising the temperature once again.
Eventually it will become hot enough to fuse
heavier elements together. Fusion of heavier
elements will release enough energy that the sun
will become a red giant. When the sun becomes a
red giant its radius can expand to be ~100 times
larger than it currently is. This will engulf
Earth with temperatures much higher than the
melting point of the rocks Earth is made of
destroying the planet.
Early in Earth's history
(about 4.5 billion years ago), a smaller (~70% the
current mass) Earth was struck by a Mars-sized
impactor (bolide). The impactor struck the Earth
at an angle and delivered enough energy that it
melted the planet and itself actually vaporizing
some of the rocks that make up the crust. The
energy from the angled impact spun some of the
amalgamated body off the Earth which collected,
coalesced, and cooled to form the Earth's moon.
An impact of this size would definitely rework the
planet effectively ending this Earth.
not worry about either of these events. The
probability of a giant impact is incredibly low
and 6 billion years is a really long-time. There
are plenty of other ways that human presence on
this planet can end like global warming and other
environmental catastrophes, but the planet will
In about 5 billion years, when the Sun becomes a
red giant, and gets asbig as the orbit of Mars!
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