:Why does the earth orbit around the sun? -Earth’s (almost) eternal solar orbit
Since the dawn of time,
humans have pondered the question – why does the Earth revolve around the Sun? The answer lies in
the powerful force of gravity, which binds the Sun and the planets together in our Solar System.
The Earth is held in orbit by the Sun’s gravity. The Sun’s gravitational force is strongest at its
center, therefore, planets that are closest to the Sun will be pulled in tighter. This is why
the Earth’s orbit is elliptical, meaning it is closer to the sun at certain points
and farther away at others. As far as we know, this dance will last as long as the sun dies.
Nowadays, it is not hard for us to believe in such things: everything seems quite normal and
trivial to us. But if we go back, we soon realize how difficult it for humankind was to reach this
self-consciousness level. Back then, scientific concepts weren’t as trivial as you think.
Follow me in this video to get to know more about the forces that keep the Earth, the moon,
and other planets around the sun. Spoiler alert: the same laws apply to exoplanets
and exomoons.
Historical context The concept of heliocentrism,
that is, the idea that the Earth revolves around the Sun and not the other way around, has been
around since the time of the Ancient Greeks. The Ancient Greeks believed in a geocentric universe,
where the Earth was at the center of the universe and was the stationary point
around which all the planets and stars revolved. It was not until the time of Nicolaus Copernicus,
however, that heliocentrism began to gain traction. Copernicus was an astronomer
and mathematician who published a book in 1543 called De Revolutionibus Orbium Coelestium (On
the Revolutions of the Celestial Spheres) outlining his heliocentric model of the universe.
His model attempted to explain the observed motion of the planets by
postulating that the planets rotate around the Sun and do not revolve around the Earth.
In addition to Copernicus, two other influential figures in the development of heliocentrism were
Galileo Galilei and Johannes Kepler. Galileo studied Copernicus' model and was one of the
first to observe that Venus went through phases like the Moon, which confirmed the heliocentric
model. He also observed the moons of Jupiter and used the idea of heliocentrism to explain them.
Kepler was a mathematician and astronomer who discovered the three laws of planetary motion,
which described the motion of planets around the Sun in mathematically precise terms.
The concept of heliocentrism was met with much resistance from the Church,
which held to the geocentric view of the universe. This eventually led to Galileo’s trial
for heresy and ultimately to the acceptance of the heliocentric view of the universe.
Today, heliocentrism is accepted as a scientific fact and we have
sophisticated tools like telescopes and satellites to observe planets and stars
more accurately, allowing us to further understand the heliocentric model and
its implications.
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Observational evidence
The evidence for heliocentrism became stronger when Johannes Kepler, a German astronomer,
noticed that the orbits of planets around the Sun were elliptical.
His contribution to the scientific world has been immense. He was the first to propose that galaxies
were composed of stars and that stars moved in patterns! His work on the nature of light
and the laws of geometry are still used today. He also developed the first modern telescope.
But what really throws some astronomers for a loop is Kepler’s three laws of planetary motion.
The First Law: Every planet orbits the sun in an ellipse, with the sun at one of two foci. This
one is so predictable that it’s almost boring. The Second Law: A line between the sun and a
planet sweeps out equal areas at equal times. This one is a little more interesting: the faster a
planet is moving, the further away from the sun it gets. That’s why the Solar System’s outer planets
take longer to orbit than its inner planets. The Third Law: The square of a planet’s orbital
period is proportional to the cube of its average distance from the sun.
This one is the most interesting because it allows astronomers to predict the
orbits of planets, moons, and asteroids! But, here’s the thing: Kepler’s third law
is sometimes referred to as “Kepler’s Fun Law”. This is because astronomers often play a game
called “Kepler’s Fun”. The object of the game is to use the equation to calculate how long it would
take a planet to orbit the sun if it were twice as far away. It’s a great way to pass the time and a
useful tool for teaching kids about the universe. For those looking for more than just a game,
Kepler’s laws can provide useful insights into the nature of the universe and how it
works. But for now, let’s just enjoy the game of “Kepler’s Fun”. It’s a great way to explore
the Solar System, and have fun doing it! Perhaps the observational evidence that
contributed the most to the fall of geocentrism came from Galileo Galilei.
The famous scientist and professor conducted several experiments in 1609 and 1610 to observe
the moons of Jupiter, and prove that the Earth was not the only body revolving around a bigger
object. His observation demonstrated that the planets revolve around the Sun,
and from this evidence, he concluded that the Sun, not the Earth, was the center of the Solar System.
This observation by Galileo helped to solidify the heliocentric model of the Solar System.
It also demonstrated that the universe was more complex and that our understanding of
it needed to be updated to include heliocentrism. So we know that the planet Earth revolves around
the Sun, as well as all the other planets in the solar system. But will it ever stop doing so?
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STABILITY OF THE ORBITS
The revolving of the Earth and other planets around the Sun keeps the Solar
System in a stable state. Without the Earth’s orbit, life as we know it would not exist.
It is the gravitational pull of the Sun that helps keep the planets in their orbits, providing us
with the warmth and light necessary for life. As long as the Sun remains active, it is highly
unlikely that the Earth and other planets will ever stop orbiting around it. The Sun has been
around for 4.5 billion years and is expected to remain in its current state for at least another
5 billion years. So, the planets will continue to rotate around the Sun for a very long time.
The orbits of the planets do not remain the same over time, however. Although the
orbits remain stable, they can drift slowly over time due to gravitational influences from other
objects in the Solar System. The most notable example is the eccentricity of Mercury’s orbit,
which slowly increases over centuries due to the gravitational pull of other planets.
There are also external forces that can alter the orbits of the planets. In some cases,
asteroids or comets can pass close enough to the planet to alter its
orbit. Even the slightest change to an orbit can have drastic consequences,
such as a planet drifting away from the Sun or crashing into another planet.
In conclusion, although the orbit of a planet can change over time, it will remain in a stable state
as long as the Sun remains active.
========================= EXOPLANETS AND EXOMOONS
But what about exoplanetary systems and exomoons? Even though they are much further away from us,
they still follow the same laws of physics and orbital dynamics. This means that many of the
principles that we understand to be true for our Solar System also apply to exoplanetary systems.
In particular, exoplanetary systems exhibit the same stability as the Solar System.
Like the Earth, exoplanets are held in orbit by the gravity of their sun. This powerful force
binds the exoplanetary system together and keeps the planets in a stable state, preventing them
from drifting away or crashing into each other. The same laws of physics that govern the behavior
of the planets in our Solar System help to keep the exoplanets in orbit, providing the same level
of stability for those distant universes. The eccentricity of exoplanetary orbits may
also be affected by interactions with other objects in the system. This can cause the
orbits of exoplanets to drift over time, just like the orbit of Mercury in our Solar System.
The external forces of passing asteroids or comets can also potentially alter the
orbits of exoplanets, although this is much less likely as they are much further away from the sun.
We don’t really know much about exomoons, because we never really observed one.
Nevertheless, we are sure they exist. I mean, they MUST exist. It would be really weird if
they didn’t. Finding an exomoon is another level of difficulty. They are even smaller
and harder to detect than exoplanets. It would be similar to trying to detect a tiny grain of
sand near a headlight miles away. Nevertheless, Columbia University astronomers may have detected
the first-ever exomoon. Alex Teachey and David Kipping combed through Kepler data for hundreds
of exoplanet detections, and one record stuck out. The data indicated that the star Kepler 1625
(8,000 light years away) had dimmed once (from Kepler 1625b, a Jupiter-sized planet passing by),
suggesting the presence of an exoplanet. But curiously, it had also dimmed again within
a day—for a similar amount of time. It couldn’t be the same planet; there
wouldn’t have been enough time for the planet to loop around in a matter of hours, because
a single orbit should be around 287 days. And it probably wasn’t a second planet, because another
planet traveling at the same speed as Kepler 1625b would share its orbit and likely collide with it;
while a planet in a different orbit would travel faster or slower than Kepler 1625b.
Then, finally, could this be an object trailing just behind the planet? Maybe this was an exomoon!
This video published by Esa shows what they actually saw! This might be the
first convincing evidence for an exomoon! https://www.youtube.com/watch?v=dduClMGMU-U
In conclusion, the stability of exoplanetary systems is largely reliant on the same forces
that keep our Solar System in equilibrium. This is the strength of physics: provided the
conditions are the same, the laws stay the same everywhere in the universe.
The power of the star’s gravity controls the orbit of the exoplanets, providing stability to
their systems. Although the orbits may drift over time, the same laws of physics apply,
ensuring that the exoplanets remain in a stable state for a very long time.
========= It is an incredible thought to realize that
the Earth’s orbit and the Sun’s gravity combine to keep us safe and secure in our own Solar System.
So, the next time you look up in the sky, remember that it is the Sun’s force of
gravity that is keeping the Earth in its orbit, allowing us to exist and thrive.