Two scary "what would happen if..." that could hit Earth
What would happen if the Sun went out? Even without being astronomy experts, most of us
know that that big yellow thing shining in the sky is pretty important to our existence. And that
without it, things down here on Earth would be rather cold and dark. However, we were curious to
understand what might happen if our giant source of heat and light suddenly vanished from the sky.
Without neglecting to ask a final question about the consequences of a cosmic braking...
There are 28 billion Sun-like stars in the Milky Way, but it is obviously the
latter that we Earthlings like to give all our attention to.
Its gravitational force, after all, holds the Solar System together, and the enormous amount
of energy it radiates enables life on Earth. From our point of view is no small merit...
Its presence also influences us in many other ways, as it is responsible for the climate
and the flow of the seasons, ocean currents, and the beautiful phenomenon of auroras. But,
like everything in the universe, sooner or later the Sun too will come to an end.
It is estimated that the Sun will be permanently extinguished in about 5 billion years,
but our planet, along with Mercury and Venus, will probably be vaporized well before that,
when the Sun will become a red giant in 4 billion years. But we won't have to worry about that. As
the Sun's brightness increases by 10 percent every billion years, environmental conditions on Earth
will become unlivable long before that deadline. But this I have just described to you is the
sequence of events that will lead to its natural death. Let's instead invent a thought experiment,
and try to imagine that the Sun would suddenly go out, like a light bulb -- right at this moment!
What would happen? After how long would we notice it?
At the speed of 300,000 km per second, light takes about 8.3 minutes to cover the distance between
the Sun and Earth, which is about 149.6 million kilometers. So from the moment the sun disappears,
it will be a little more than 8 minutes before we know visually what has really happened.
Initially, nothing would happen here on Earth. For about eight minutes and twenty seconds,
everything would be normal: during this time, the last rays of light would reach the Earth's
surface. Then, in the illuminated hemisphere would suddenly fall the darkest night ever seen.
After a little more than a second, the Moon would also go out, and then gradually, in order of
distance, all the other planets would disappear, no longer reached by the light of the Sun...
Within minutes of the Sun going out,
temperatures would drop 4-5 degrees in the areas that were illuminated at that time.
This will be a frightening situation, as very soon we will realize that the night will be
eternal and that there will never again be any morning to brighten the eastern horizon...
Cities, however, will not go dark immediately, as power plants and atomic power plants will continue
to operate, as long as fuel supplies last. Meanwhile, strange behaviors would begin to
be observed in animals whose life cycles depend on alternating day and night.
Photosynthesis would stop. Most plants would die within a few weeks, and the animals that feed on
them, humans among them, would begin to starve. We could make it for a few months with the
available supplies, but beyond that, it would be a famine for most life forms.
With plants dying, it may seem that we may soon run out of oxygen as well. But this
will not be immediate, since the atmosphere has reserves that can last for at least a millennium.
Normally, Earth's average temperature is about 15° C, but with the sun vanished into obscurity,
after a week the average across the globe will drop to the freezing level,
and after a year we will be at -40° C, about the same as on Mars.
Meanwhile, another unpleasantness will have occurred. You all know that if a
planet manages to revolve around its star quietly for billions of years,
it is because it compensates for the gravitational force, which would tend
to make it plummet toward the star, with the speed with which it moves along its orbit.
Well, can you imagine what might happen if the gravitational force suddenly failed? That's
right--the planet would instantaneously go off on a tangent and drift off into
space with rectilinear motion, conserving its previous orbital velocity by inertia.
Lo and behold, this would happen to the Earth, and we would find ourselves as if aboard a spaceship
that began moving toward unknown destinations at a speed of 30 kilometers per second! And that, too,
since gravitational effects also propagate at the speed of light, would happen exactly
8.3 minutes after the Sun disappeared! The gravitational field would disappear,
and all the planets in the solar system--first Mercury, then Venus, then Earth, and so on in
order of distance--until Neptune, would be shot off at a tangent. Each one for itself!
What about the moon? Well, our natural satellite would follow, circling us as always.
Meanwhile, the oceans would get colder and colder, until they would freeze over, turning Earth into
a world of ice. But just like deep lakes in winter, only the surface would freeze, leaving
a liquid ocean below. If any humans survived this extreme transformation, their only refuge would
be near the geothermal vents on the ocean floor. Humans would have to move to places where they
could get heat from the center of the earth, such as natural hot springs.
After a month, the average temperature would be -120°C,
and the surface of our planet would become impassable for any living thing.
But wait a minute--not all the heat on our planet depends on the Sun!
Under the Earth's crust, in fact, lies a sea of uranium and thorium that heats the planet and
is partly responsible for earthquakes, volcanic eruptions, and the formation of the sea floor.
Not to mention the heat generated by the enormous pressure that the
innermost layers of rock are subjected to... Some of this heat also reaches the earth's crust,
particularly in geothermal areas, areas where geothermal energy can make its way. These are
volcanoes, fumaroles, hot springs, hydrothermal springs, and geysers: near these areas,
life would endure a little longer. To survive, humans would have to create
settlements near these areas, with underground or thermally insulated buildings supplied with energy
by nuclear power plants. Anyone not in these areas would certainly be dead within a year.
Of course, no small problem would remain: how to feed ourselves? We could grow a few
vegetables with artificial lighting, but it would become complex to find solutions to feed
many individuals well and for a long time. Probably, barring exceptional inventions,
our species would only be able to get by for a few years.
Would this then be the end of life on Earth? Perhaps not. But as we are about to see, only tiny
living things will be given a chance to survive. Three years after the disappearance of the Sun,
the oceans would appear totally frozen: water would be solidified miles deep.
But ice has a lower density than water and is an excellent thermal insulator,
so these layers of ice would float on a layer of water, protected from freezing. This would allow
water to remain in a liquid state, in the ocean depths of our planet, for millions of years yet
What's more, the seafloor would continue to be warmed by heat from inside the Earth: deep inside.
Underwater ecosystems such as hydrothermal vents, and underwater "chimneys" from which
geothermally heated water emerges, would thus be preserved. And so, organisms that do not depend
on the Sun to survive, capable of converting heat, methane, and sulfur into energy, would
continue to thrive as if nothing had happened. There are hundreds of microbial species capable
of getting by even under extreme conditions. And surely from these surviving strains,
evolution would be able to select in a few million years more complex creatures...The
new Earthlings! The rightful representatives of planet Earth in the millions of years to come.
"Hey, guys, just a moment before we continue... BE sure to join the Insane Curiosity Channel...
Click on the bell, you will help us to make products of ever-higher quality!"
Of course, the instantaneous disappearance of a star is not
exactly one of the most probable events in the rich casuistry of cosmic catastrophes,
but that does not detract from the fact that even imagining the impossible can be of help
in understanding how thin the thread that binds the survival of humans to
their supposed security that everything "must continue the same way forever."
An illusory security that also relates to another famous thought experiment... that of asking:
What would happen if the Earth stopped rotating?
Have you ever thought about the possible consequences for life on the planet if the
Earth suddenly stopped rotating around its axis and came to a complete halt?
Well. Before we start talking about the disasters you are already surely imagining,
it is only fair to point out that right now the Earth is spinning on itself with an angular
velocity of 15° per hour, which corresponds at the equator to a speed of about 1670 km per hour.
And we did not specify "at the equator" for nothing--the speed at which a point on the
surface moves does in fact vary with latitude. At mid-latitudes, the linear speed is 1180 km/h,
while the speed at the poles is zero! That said, the most serious effect of
a sudden stop in the rotation would be to be jolted from west to east at a speed inversely
proportional to the value of one's latitude. In practice in New York, we would find ourselves
projected eastward at over 1090 kilometers per hour, with virtually no chance of salvation.
And not just people of course but all things--from small ones to things as big as mountains. What
could escape such braking? Really nothing ... but assuming you were near the poles where the
rotational speed is zero, you might temporarily survive waiting for subsequent events. In fact,
the braking would also affect the atmosphere and the seas, causing supersonic windstorms
in the skies that would sweep across the planet's surface and giant tsunami waves
in the seas that would obliterate everything in their path, reaching even the polar latitudes.
Nothing would stand a chance, not even birds or planes not adhering to the ground.
Finally, the air, traveling at a speed beyond the speed of sound, would create an unprecedented
erosive force (capable of smoothing hills and mountains in a very short time),
and the dust and rocks involved in this whirlwind would be so fast as to cause sparks and whirlwinds
of fire. The only way to avoid this catastrophe would be to find ourselves exactly in the center
of one of the two poles and watch the final storm disrupt the entire planet. Actually,
even there we would not be safe as there would be many more consequences after a short time.
At the end of the storm we talked about earlier, the masses of water-no longer
subject to centrifugal force-would not return to their place, but would level
off more evenly following only the force of gravity; they would especially try to
pour out in the direction of the poles. All the seas and oceans would find themselves arranged
at the North and South Poles, thinning out almost completely from the equatorial belt
and making way for a single, large, and very long continent-like ring around the planet.
The length of day and night hours would also change dramatically. The day would last a
whopping six months and the same for the night. As a result, the habits of all living things (should
there be any left alive) would be compromised, leaving room only and exclusively for total chaos.
Although the Earth is not "tidally locked" relative to our star (in fact, we imagined that
it would stop spinning, and not always show the same face to the Sun-more dangerous than ever),
the day and night hemispheres would find themselves facing truly arduous
temperatures to sustain life, and taking turns every 6 months would not be of such great help.
Exacerbating the situation would be the fact that since air would
no longer circulate - lacking the Earth's rotation - it would not be possible to have
even slight breezes from the shaded zone. It would be a mere alternation of two seasons,
half a year long: one scorching beyond imagining, and the other with cold and extreme temperatures.
Should we find a way to survive all this misfortune, perhaps by relocating to spaceships
and then returning to our home planet after the fact, we would still have to face the
final problem, the one that would put an "end" to everything we consider life: radiation.
Earth's rotation, along with the swirling of the core-which appears to be solid but is more
fluid than previously thought-is in fact one of the primary aspects for the proper
functioning of our magnetic field, which protects us from the powerful solar winds,
full of charged particles, ultraviolet rays, and deadly cosmic rays.
On balance, however, in reality, there is not really a real possibility that this
can be realized. The Earth is slowing down its rotation, due to the Moon and its "gravitational
friction," but it is a really long process, which confirms that we can sleep easy dreams:
for another ten billion years or so our planet will rotate without any problem, and we will
not have to worry about it (also because in a billion years our biggest problem will become
the Sun and its increase in brightness). By then perhaps mankind will have even
forgotten its place of origin and will rule the stars, but if not, it will mean that,
much more simply, there will be no mankind left to worry about such happenings.