Do you know that the planets and moons would cease to orbit their parent bodies without gravity and drift away in a straight line? Or, that the gravity is only strong over a short distance, but dark energy is thought to be distributed evenly, which prevents the gravity from pulling everything back together?
What do we know about gravity? In short, ‘Nothing’. We barely even think about it, at least until we stumble on the stairs or slip on the ice. Most ancient thinkers even didn’t consider gravity a force. In their words, it was simply the natural tendency of objects to sink towards the center of the Earth, while planets were subjected to unrelated laws.
But there’s more to it. It is one of the four well-known forces in physics. The others electromagnetism governs magnetism, light, electricity, and a pair of nuclear forces that operate across tiny distances within atomic nuclei. Yet, despite being all-pervasive and crucial for keeping our feet from flying off the Earth, gravity remains still a mystery to scientists.
Our knowledge about gravity has been evolving since the days of the famous ‘Issac Newton and his apple”- and it still is. Every time we discover something new about gravity, we tend to see the world around us in a new light.
Gravity- What Do We Know?
Gravity is defined as a force of attraction that exists between any two masses or any two particles. It simply doesn’t define the attraction between the objects and the Earth. It is an attraction that prevails between all objects and everywhere in the universe.
Sir Issac Newton (1642-1727) discovered that a force is essential to change the speed or the direction of the movement of an object. He also understood that the force called ‘gravity’ is what makes an apple fall from a tree or help humans live on the surface of our spinning planet without being flung off. What more, he also realized that gravity is a force that exists between all the objects.
Issac Newton’s law of gravity soon became a mathematical description of the way bodies on the surface of the Earth are observed to attract one another. The gravitational equation defines that the force of gravity is proportional to the product of the two masses (m1 and m2). It is also inversely proportional to the square of the distance (r) between their centers of mass.
Here G denotes the Gravitational Constant. G has a value of 6.6726*10-11m3kg-1s-2.
The effect of gravity extends from each object present in the space in all directions possible, and that too for an infinite distance. But, the strength of the gravitational force reduces quickly with the distance.
We, human beings are never aware of the sun’s gravity pulling, as the pull is so small at a distance between the Earth and the Sun. Neither are we aware of the pull the lunar gravity has on our bodies, but as per the physicists and science assignment help experts, the moon’s gravity is responsible for all the ocean tides on the Earth.
We would give you certain exemplary examples of the instances of gravity that would help you form a comprehensive idea-
- The force that holds all the gases in the Sun
- The force which leads a toddler to propel down the slide
- The force that leads a glass to fall on the floor when you drop
- The force which helps you walk on the surface of the Earth instead of floating away in the space
Rare And Intriguing Facts On Gravity
If you give it a close thought, the story of gravity is also the story of physics, with some of the biggest names of the field earning fame by defining the force that ruled their lives. However, even after more than 400 years of study, the enigmatic force still lies at the core of some of the world’s greatest mysteries.
After years of countless discoveries, we still don’t know everything about gravity. This includes the accurate way it fits in with the other vital forces of the Earth. But, here are some of the intriguing and rare facts that we all should know about the primary fundamental force on the Earth-
- Gravity is powerful, but not too powerful
As we said above, gravity is the weakest of all the fundamental forces on Earth. A bar magnet can electromagnetically pull a paper clip upward, defeating the gravitational force of the entire Earth. As per the PBS’s Nova, physicists have estimated that gravity is 10^40 times weaker than electromagnetism.
In 1798, the British physicist Henry Cavendish conducted one of the world’s first high precision experiments to precisely determine the value of gravitational constant or the G. (Proceedings of the National Academy of Science’s Front Matter) His estimation of G came out to be only 1% off from the modern-day accepted value of 6.674*10^-11m63/kg^1*s^2.
The next revolution in our knowledge of gravity was brought by the brilliant German-American physicist Albert Einstein. His theory of general relativity demonstrated that gravity arises from the curvature of space and time. This implies that even the rays of light, which should follow this curvature, are bent by extremely massive objects.
The theories of Einstein were used to speculate the existence of the black holes. In the vicinity of a black hole, Newton’s law of universal gravitation no longer explains how accurately the objects move, but rather Einstein’s tensor field equations take precedence in the case.
- Gravity remains a perpetual force of mystery since ages
Gravity is such a way that confuses every scientist in other ways, too. In fact, it is observed to be one of the trending discussions on the physics assignment help forum. The Standard Model of Particle Physics that explains the actions of almost all well-known particles and forces leaves out gravity. While light is carried out by a particle called a photon, physicists remain clueless if there remains an equivalent particle for gravity, which would be known as the graviton.
However, gravity has still been used to unearth monumental findings. In the 1960s and 70s, astronomers Kent Ford and Vera Rubin showed that stars at the edges of the galaxies were orbiting faster than it is possible. It was almost as if some unseen mass was tugging on them gravitationally, helping us know a light material now popularly known as the dark matter.
In the recent era, numerous scientists have also managed to capture another consequence of Einstein’s theory of relativity. It was observed that the gravitational waves emitted when massive objects like neutron stars and black holes rotated around one other. Since 2017, the LIGO (Laser Interferometer Gravitational-Wave Observatory) has opened up a new window to the universe through the popular detection of the exceedingly faint signal of such events.
- Gravity and weight- Not one and the same thing
Often we tend to say lazily that astronauts are in zero gravity when they remain afloat on the space station. But, that’s not completely true. The force of gravity on an astronaut is about 90 percent of the force that they would experience on the Earth. But, astronauts are weightless as the weight is the force the ground exerts back on them on the Earth.
Take an example. If you take a bathroom scale onto an elevator in a big fancy hotel and stand on it while the elevator goes up and down, you would see your weight fluctuating. Apart from that, you would also feel the elevator accelerating and decelerating, though the gravitational force remains the same. But in the orbit, astronauts move along with the space station. There exists nothing to push them against the side of the spaceship to make weight.
- Gravity creates waves that move at a lighter speed
Gravitational waves are predicted through general relativity. Like, if you have two stars or white dwarfs or black holes locked in the mutual orbit, they gradually get closer as gravitational waves tend to carry energy away. As a matter of fact, Earth also emits gravitational waves as it orbits the Sun, but the energy loss is too tiny to even notice.
About 40 years ago, we had indirect evidence for gravitational waves, but the LIGO confirmed this rare phenomenon in 2016. The detectors picked up a burst of gravitational waves produced by the collision of two black holes more than a billion light-years away.
As per eminent physicists and scientists worldwide, one noteworthy consequence of relativity is that nothing can travel faster than light in a vacuum. That applies to gravity, too. Thus, if anything drastic happened to the Sun, the gravitational effect would reach us roughly simultaneously as the light from the event.
- Massless particles known as ‘Gravitons’ carries the gravity
Particles are observed to interact with each other through other force-carrying particles in the standard model. Often students who seek assignment help tend to contemplate or ask us ‘How is that even possible?”
Let us give you an example. You know that photon carries the electromagnetic force. And, the gravitons are the hypothetical particles for quantum gravity. Also, we know how they should work from the general relativity.
So, like photons, gravitons are also massless. If they were observed to have mass, researches conducted till now would have observed something- however, this doesn’t eliminate the ridiculously tiny mass.
- The quantum gravity appears at imaginable smallest length
Gravity is incredibly weak. However, the closer the two objects are, it becomes stronger. Finally, it takes the strength of the other vital forces at a highly tiny distance, popularly known as the Planck Length. It is multiple times smaller than the nucleus of an atom.
This is where the effects of the quantum’s gravity become strong enough to measure; however, it’s too small for any experiment to probe. Some people have formulated remarkable theories that allow quantum gravity to show up at close to the millimetre scale. However, till now we haven’t seen those crucial effects.
Einstein’s theory in helping physicists solve innumerable problems in cosmology and astrophysics is not the final word on gravity. This is because no one has yet figured out how to reconcile general relativity with other remarkable physics and quantum physics theories that explain the inner working of the subatomic realm.
We all do hope that a complete theory may one day combine general relativity with quantum mechanics. If and when that occurs, we may once again see gravity in a new light or discover intriguing facts on gravity.