Gravity — The God Of Attraction
Understand gravity= Understand everything
Apple didn’t speak to Newton; it was gravity that was whispering from within the apple. The force is so weak that you and I won’t even notice it. Gravity chose Newton, as he was a curious child who would spend more time understanding nature than in making friends. Gravity made the apple fall on the exact spot over his head from where the idea had to begin. The genius of Newton was that he knew how to communicate with the weakest force of nature. His conversation with gravity took the form of his laws of gravitation. Newton observed the gravitational force between two objects depends on the mass of the objects and the inverse of the square of the distance between the objects.
Not only this, with the help of imagination and laws of gravitation, Newton linked them to come to the conclusion that rock when thrown in the air returns back to earth is only because the earth’s gravitation is stronger than Sun(acting on the rock as Sun is far away in comparison to earth). He further imagined, if you keep throwing a rock with higher speeds, the rock will go farther and farther, before landing; with persistence and increasing the speed of the rock, you’ll reach a somewhat magical speed where the rock keeps its height over the ground exactly constant and would never land, finally orbiting Earth in a somewhat circular path — that’s what the moon does. His curiosity was stronger than the force of gravity that he was able to calculate the magic speed to be 7.9 km/sec.
Thanks to Newton, Albert Einstein had started to develop a love for gravity and postulated theories like the existence of black holes. The seeds of Newton’s apple tree dispersed everywhere. Wherever these seeds were planted, these seeds furthered his ideas. They were planted in Cambridge University and reached the mind of scientists like Stephen Hawking who would later work primarily in the field of general relativity and particularly on the physics of black holes.
Before Newton
Before even the idea had started to take place. It all started in Italy, when the leading scientist of the era, Galileo Galilee, standing on the Tower Of Pisa noticed that gravitational force acts the same on all the objects. It was a novel discovery and had totally changed the thinking pattern, which was dominated by the Aristotelian way of thinking — that heavier objects move faster due to the effect of gravity.
After Newton, came the ideas of Albert Einstein, who had taken the concept of gravity even further. Einstein showed mathematically that gravity is not really a force that of attraction between all objects with mass, as Newton thought. According to Dr. Einstein, there is a relation between matter and space. And he tried to link gravity with the matter. He said matter creates gravity, and in turn, gravity is responsible for deforming or warping space and time(which is otherwise flat). These ideas about space-time and gravity became known as Einstein’s theory of general relativity.
What is gravity in simple words?
Gravity is the bending of spacetime.
Perceiving gravity and gravitational waves
Whenever the term gravity comes to my mind, I think it to be carried in the manner the famous painter Vincent van Gogh depicted subtleness of some unknown force in his famous painting “Starry Night”. Maybe he knew something about this unknown force but couldn’t explain it in words, maybe he was perceiving the universe in its entire form. Nobody knows what do the waves in the painting depict, some astronomers believe that the genius painter was depicting nebulae, while others said they were galaxies. For now, just imagine gravity acting in a manner depicted in the world-famous painting.
Difference between weight and mass
Mass — quantity of matter in a body.
Weight — the force exerted on a body by a gravitational field.
You don’t have a weight, it’s the gravity that makes it possible whenever you shudder and hesitatingly place your feet on the weighing machine. You don’t believe me, is that what you’re thinking? Don’t worry, I’ll make you believe me. If your weighing machine says you’re 80kg — just don’t believe it. It’s showing your weight on earth. On Venus, your weight would be 72.5kg. On Uranus, it’ll be 71.1kg. You’re not satisfied, right? Okay, I understand. On Mercury, it’s 30.1 kg. You’re enjoying it, I know. Just wait we’ll get you a one-digit number. Your weight on Pluto would be 5.3kg.
Next time someone asks about your weight, you know what and how to answer the question properly. Now you won’t have to hesitate anymore.
In case someone still persists asking the same question, then just say my weight is 11200000000000 kg on a neutron star. I bet, there won’t be another question from the other side unless the person is a scientist.
Gravity is the weakest of all the forces
Take an example of the electric force between an electron and a proton — its value comes out to be one quintillion times stronger than the gravitational attraction between them.
Is gravity equally distributed on earth?
— No, gravity isn’t equally distributed on the surface of our planet.
Gravity is slightly stronger over places with more mass underground than over places with less mass. NASA uses two spacecraft in the form of GRACE( Gravity Recovery and Climate Experiment) mission to measure these variations in Earth’s gravity. What GRACE does is, detect minute changes in gravity over a period of time.
GRACE also monitors changes in sea level and can detect changes in Earth’s crust due to the effect of earthquakes.
Bentley’s Paradox —if all the stars are drawn to each other by gravitation, they should collapse into a single point.
Effects Of Gravity On A Rocket
Till now people from 37 countries have traveled in space with the help of rockets: more than 553 people have reached Earth orbit; more than 556 have reached the altitude of space, 562 people have reached the altitude of space, nearly 6,000 satellites circling our tiny planet
Rockets are the only manmade thing that managed to escape the gravity of our planet. To get out of the earth, the rockets have to attain escape velocity. If atmospheric resistance could be disregarded, escape velocity would be about 11.2 km (6.96 miles) per second. Rockets are cunning machines, they use a parabolic path around the earth which uses the gravity of the earth to ascent.
In case you want to experience the effects of gravitational changes with ascent, then the right place would be to hop on in a zero-gravity flight.
Black holes
The real god of attraction is a black hole. A black hole is a region of spacetime where gravity is so strong that nothing — no particles or even electromagnetic radiation such as light — can escape from it. Because strong gravity pulls all of the light into the middle of the black hole, and no light can get out, that’s the reason people can’t see black holes. They are invisible. Space telescopes with special tools can help find black holes. The special tools can see how stars that are very close to black holes act differently than other stars.
Scientists predict the smallest of black holes are as small as an atom — though tiny their mass would be equivalent to the mass of a mountain. The largest black holes are so gigantic that they are called supermassive black holes. These black holes could have masses of more than 1 million suns together. Scientists have found strong evidence which points at the presence of a supermassive black hole at the center of every large galaxy. Not only this, but our own galaxy milky way has a supermassive black hole called Sagittarius A at the center of it. The mass of Sagittarius A is equivalent to 4 million suns and would easily fit inside more than a million Earths.
A Recent Discovery
Gravitational Waves— LIGO
In 2015, scientists detected gravitational waves for the very first time. They used a very sensitive instrument called LIGO (Laser Interferometer Gravitational-Wave Observatory).
Gravitational waves are invisible but incredibly fast. They travel at the speed of light (186,000 miles per second). Gravitational waves squeeze and stretch anything in their path as they penetrate.
Einstein predicted that massive objects, like black holes, have effects on the spacetime fabric. He further predicted that these massive bodies when accelerating would be changing the spacetime in such a manner that these would be producing ripples similar to waves. These ripples are called gravitational waves. experiments especially at Laser Interferometer Gravitational Wave Observatory(LIGO) detected these gravitation waves
The discovery of gravitational waves has confirmed his predictions.
He had theorised that when two massive objects like black holes collide they give rise to gravitational waves. These waves can travel through objects without causing any change.
Earth also emits gravitational waves as it orbits the sun, but the energy loss is minute to notice.
The detectors observed gravitational waves developed as a result of the collision of two black holes more than 1.3 billion light-years away.
Gravity and Magnetism
Mixing up magnetism and gravity is a common confusion. Gravity is a consequence of space-time curvature caused by mass whereas magnetism is produced by moving charged particles or some materials. The Earth’s gravity and the Earth’s magnetic field are independent of each other. Though both the forces have some of the common features like forces acting at a distance, they are totally different. For example — the force of gravity always attracts and involves interaction between the Earth’s mass and any other body that happens to be nearby (the effect extends far beyond the Earth to our Moon and far beyond). In simple words, mass is the source of gravity.
On the other hand, magnetic forces occur only between certain specific materials (usually iron and certain iron alloys).
Gravitons
The three forces of nature, namely, electromagnetism, strong interactive force, weak interactive force are there because of their elementary particles. For example, photons are the particles responsible for electromagnetism; gluons for strong interaction; W and Z bosons for weak interaction. It is predicted a similar elementary particle for gravity, that has no mass because gravity is a long-range force and this particle might be travelling at the speed of light. This particle they named as the graviton. Gravitons are believed to have their own energy, which creates extra warping of space. They are believed to be massless otherwise they would have been experimentally proved. We need particle collider as heavy as a planet like Jupiter to detect just one.
Gravity explained
Wave/particle duality explains everything that is within the universe, even light and gravity in terms of particles. The particles we are going to mention have spins. The spin of a particle gives us the information — what the particle looks like from different directions. All the known particles in the entire universe can be divided into two types — particles of spin 1/2 (these compose the matter in the entire universe), and particles of spin 0,1, and 2 (these produce the forces between matter particles). These particles are very difficult to understand as they behave differently with every spin. In the words of Stephen Hawking, “the particle of spin 0 is like a dot — it looks the same from every direction; the particle of spin 1 is similar to an arrow — it looks different from different directions — only after 360 degree revolution, this particle again starts to look the same; a particle of spin 2 is similar to a double-headed arrow — it looks the same if one turns it round half a revolution or 180 degrees. And the force of gravity is believed to be carried by a particle of the spin 2 called the graviton.”
Gravity and extra-dimensions
Scientists predict that the effects of gravity would be different in different dimensions(in case they exist), and some problems associated with it. For instance, within three dimensions the gravitational force drops to 1/4 when the distance is doubled; in four dimensions it would be 1/8; in five dimensions 1/16, and in six dimensions 1/32, and so on. In turn, the orbits of the planets would be unstable. Our beloved planet, earth would increase its distance from sun or fall in it — we’ll either freeze or get burnt. Similarly, the effect of gravity with distance in other dimensions(more than three space dimensions) is the absence of stability of our Sun — it’ll be transformed into a black hole.
Why gravity is the weakest of all the four forces?
The best explanation of the nature of gravity is given by basically two theories, namely String Theory and Quantum gravity theory.
String Theory
According to string theory, our universe has ten dimensions. String theory has its own way of interpreting gravity — it states that gravity is weak because, unlike other forces, it seeps in and out of the extra dimensions — so we experience only a small portion of the force of gravity.
Quantum gravity
Quantum gravity (QG) is a field of theoretical physics that tries to describe gravity in accordance with the principles of quantum mechanics, and the regions where these quantum effects cannot be ignored, eg, in the vicinity of black holes or similar compact astrophysical objects, and where the effects of gravity are strong, such as neutron stars. Moreover, the effects of quantum gravity are negligible and can only come to life when measured at a quantum level, probably, at the Planck length scale. Why Planck length scale? — It is believed that at the Planck scale, all the fundamental forces become unified. But scientists couldn’t predict the mechanism of unification.
Predictions
“I want to know how God created this world, I want to know his thoughts, rest are just the details.” — Albert Einstein
The classical model describes the interactions between the entire range of subatomic particles that we know along with three of the four fundamental forces: electromagnetism and the strong and weak nuclear forces, but fails as it doesn’t include gravity. Gravity is regarded as the basis for all the theories that could be unified under just one single term. Scientists are working upon a theory that would eventually connect all the forces and particles.
We still don’t know everything about gravity, including the exact manner it interacts with the other fundamental forces. But one thing we do know is that the force of curiosity is much stronger than gravity. And when both gravity and curiosity acts in the same direction they give rise to information, a lot of information. Though a weak force but the gravity of the idea was so strong and whichever mind it penetrated, the mind couldn’t come out of its grip. From enthralling adventures like skydiving and Bungee jumping, to the complex theories like string theory and quantum theory, all of them took birth out of gravity. Gravity was the first force that bound humans together and would continue to do so….
