| Will there ever be a time in the future where the
sun will be harmful to humans, and if so, when
will it be?
|Question Date: 2017-09-28|
Well yes. The sun is about 5 billion years old.
That is 5,000,000,000 years old! It’s pretty old …
even older than your mom and dad together!! Ha ha.
So, the sun has hydrogen and the sun uses the
hydrogen as its fuel. The reaction is:
Hydrogen = Helium plus lots of energy and light
Now, the sun only has enough fuel to “burn” for
another 3 or 4 billion years. So 3 or 4
billion years from now the SUN will run out of
hydrogen. This will make the sun swell up and
become a RED GIANT star. It will be so big
that the sun will swallow the EARTH and our planet
will be toast…
So, if there are any life forms on the planet
about 3 billion years from now they will have to
migrate to another planet perhaps in another star
NOTE: Do not worry, 3 billion years is a
lot, lot of time.
In terms of the sun's life cycle, no, it will
never be harmful to humans because humans will
likely not exist still when the sun reaches a
state that will undermine Earth's current
habitable condition. But let's go through that
life cycle anyway.
According to the nebular hypothesis, the
most widely accepted model to explain the
formation and evolution of the solar system, our
solar system began as a giant cloud of molecular
dust and gas. Approximately 4.567 billion years
ago, that cloud collapsed and pockets of denser
material began to collect, begin rotating, and
heat up. The ball in the center became a
collapsing protostar (the beginnings of the
sun we have today) and the remaining debris
flattened into a disk around the protostar (making
up the planets around the sun today). In just a
few million years, the protostar settled into
the star we see today.
For the past 4.5+ billion years, the sun has
been undergoing nuclear fusion reactions in
its interior, where hydrogen and helium atoms fuse
together. This process will not last forever, and
that brings us back to your question about the
future of the sun.
As the sun continues to convert hydrogen into
helium atoms, the core becomes smaller and denser.
This means its gravitational force becomes
stronger and its brightness becomes brighter.
In about 1.1 billion years from today the sun
will be about 10% brighter than today (and hotter
as well), and the result will be wet
greenhouse conditions on Earth that are similar to
conditions that pushed Venus into runaway heating.
In approximately 3.5 billion years, the sun
will be about 40% brighter than today (and again
even warmer). This will lead to the ice caps
melting, the oceans boiling, and all water on
Earth will turn to vapor and be lost to space.
Essentially Earth will likely turn into a
similar state as Venus.
Finally, in about 5.5 billion years, the sun
will burn up the last of the hydrogen and grow
into a Red Giant. It will grow so large
that it will possibly encompass the orbit of
Earth. At this point the sun only has about 150
million years of life left. It will go through
a series of expansions, explosions, and
compactions as it burns up all the helium then
loses mass by ejecting its outer envelope. It will
eventually cool to a white dwarf. The white
dwarf will survive for trillions of years before
Outside of its life cycle, the sun can
affect humans today through solar flares and
coronal mass ejections. Solar flares are
gigantic explosions that release radiation, and
coronal mass ejections are huge explosions that
release gas and magnetized plasma. Earth's
atmosphere protects humans from both events.
However, they can affect Earth's magnetic field
and disrupt technology that humans rely on, such
as damaging communications satellites above
Earth's atmosphere, damaging electrical grids and
causing black outs, and disrupting high-frequency
radio communications. Though those effects are not
directly harmful, they could impact humans
The sun is already harmful to humans if you are
out in it for too long and get sunburned.
Also, as the sun ages, it becomes larger and
brighter, and it will eventually make the earth
unlivable. This will probably happen in a
billion years or so. It is all but certain
that human beings like us will be extinct by then,
but if we are the ancestors to any species alive
then, those species will either have to escape the
earth or be destroyed along with the rest of life
when this happens.
This is an interesting question. The sun can
already be harmful to humans in a variety of ways
under conditions of extensive exposure.
I'm sure you know many people who have been
sunburned from being out in the sun for too long
without sunscreen. Furthermore, depending
on how long they were out and how easily they burn
(which is often correlated with the amount of
melanin, a skin pigment, people have), they
may have been burned pretty badly! Sunburns are
one example of ways the sun can be
damaging/harmful to people. Sunburns are
caused by damage to skin cells that is caused by
prolonged exposure to the UV radiation the sun
perpetually emits. Wearing sunscreen, or even
having naturally larger amounts of melanin can
help mitigate the damage, but even that has its
limits (that's why they tell you to re-apply
The sun can also be harmful to people who have
spent too long by causing heat stroke, or
overheating. People can become faint, feel unwell,
or even vomit if they have been too hot for too
There are also indirect, or longer term ways
prolonged or consistent exposure can be harmful to
people. People who have been exposed to the sun
consistently for extended periods of time without
proper skin protection are more likely to age more
quickly (think of older, leathery-skinned people).
We don't often think of aging as "harmful," and it
is certainly a natural process that all living
organisms experience, but I think the
acceleration of aging can be harmful in a sense.
Nevertheless, the sun is also directly and
indirectly imperative for our livelihood.
Without the sun, we would freeze and not have
plants/vegetables to eat, or animals in the food
chain. The vast majority of life as we know it
would not exist (plants and many bacteria carry
out photosynthesis to generate energy).
So where does that leave us? I think, as
with many things, the lesson is that we must
take things in moderation, including exposure
to the sun. Too much of anything can often be
harmful. I hope that helps!
Click Here to return to the search form.
Copyright © 2017 The Regents of the University of California,
All Rights Reserved.