what is Gravity???
Answers
Question:
What is Gravity?
Answer:
Gʀᴀᴠɪᴛʏ ɪs ᴀ ғᴏʀᴄᴇ ᴏғ ᴀᴛᴛʀᴀᴄᴛɪᴏɴ ᴛʜᴀᴛ ᴇxɪsᴛs ʙᴇᴛᴡᴇᴇɴ ᴀɴʏ ᴛᴡᴏ ᴍᴀssᴇs, ᴀɴʏ ᴛᴡᴏ ʙᴏᴅɪᴇs, ᴀɴʏ ᴛᴡᴏ ᴘᴀʀᴛɪᴄʟᴇs. Gʀᴀᴠɪᴛʏ ɪs ɴᴏᴛ ᴊᴜsᴛ ᴛʜᴇ ᴀᴛᴛʀᴀᴄᴛɪᴏɴ ʙᴇᴛᴡᴇᴇɴ ᴏʙᴊᴇᴄᴛs ᴀɴᴅ ᴛʜᴇ Eᴀʀᴛʜ. Iᴛ ɪs ᴀɴ ᴀᴛᴛʀᴀᴄᴛɪᴏɴ ᴛʜᴀᴛ ᴇxɪsᴛs ʙᴇᴛᴡᴇᴇɴ ᴀʟʟ ᴏʙᴊᴇᴄᴛs, ᴇᴠᴇʀʏᴡʜᴇʀᴇ ɪɴ ᴛʜᴇ ᴜɴɪᴠᴇʀsᴇ.
Example:
Tʜᴇ ғᴏʀᴄᴇ ᴛʜᴀᴛ ʜᴏʟᴅs ᴛʜᴇ ɢᴀsᴇs ɪɴ ᴛʜᴇ sᴜɴ. Tʜᴇ ғᴏʀᴄᴇ ᴛʜᴀᴛ ᴄᴀᴜsᴇs ᴀ ʙᴀʟʟ ʏᴏᴜ ᴛʜʀᴏᴡ ɪɴ ᴛʜᴇ ᴀɪʀ ᴛᴏ ᴄᴏᴍᴇ ᴅᴏᴡɴ ᴀɢᴀɪɴ. Tʜᴇ ғᴏʀᴄᴇ ᴛʜᴀᴛ ᴄᴀᴜsᴇs ᴀ ᴄᴀʀ ᴛᴏ ᴄᴏᴀsᴛ ᴅᴏᴡɴʜɪʟʟ ᴇᴠᴇɴ ᴡʜᴇɴ ʏᴏᴜ ᴀʀᴇɴ'ᴛ sᴛᴇᴘᴘɪɴɢ ᴏɴ ᴛʜᴇ ɢᴀs. Tʜᴇ ғᴏʀᴄᴇ ᴛʜᴀᴛ ᴄᴀᴜsᴇs ᴀ ɢʟᴀss ʏᴏᴜ ᴅʀᴏᴘ ᴛᴏ ғᴀʟʟ ᴛᴏ ᴛʜᴇ ғʟᴏᴏʀ.
ʜᴏᴘᴇ ᴛʜɪs ʜᴇʟᴘs
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Gravity is one of the four fundamental forces in the universe, alongside electromagnetism and the strong and weak nuclear forces. Despite being all-pervasive and important for keeping our feet from flying off the Earth, gravity remains, in large part, a puzzle to scientists.
Ancient scholars trying to describe the world came up with their own explanations for why things fall toward the ground. The Greek philosopher Aristotle maintained that objects have a natural tendency to move toward the center of the universe, which he believed to be the middle of the Earth, according to physicist Richard Fitzpatrick from the University of Texas.
But later luminaries dislodged our planet from its primary position in the cosmos. The Polish polymath Nicolas Copernicus realized that the paths of the planets in the sky make much more sense if the sun is the center of the solar system. The British mathematician and physicist Isaac Newton extended Copernicus’ insights and reasoned that, as the sun tugs on the planets, all objects exert a force of attraction on one another.
Fg = G (m1 ∙ m2) / r2
Where F is the force of gravity, m1 and m2 are the masses of two objects and r is the distance between them. G, the gravitational constant, is a fundamental constant whose value has to be discovered through experiment.
Newton's Law of Universal Gravitation says that the force of gravity is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.
Newton's Law of Universal Gravitation says that the force of gravity is directly proportional to the product of their masses and inversely proportional to the square of the distance between them. (Image credit:marekuliasz Shutterstock)
Gravity is powerful, but not that powerful
Gravity is the weakest of the fundamental forces. A bar magnet will electromagnetically pull a paper clip upward, overcoming the gravitational force of the entire Earth on the piece of office equipment. Physicists have calculated that gravity is 10^40 (that’s the number 1 followed by 40 zeros) times weaker than electromagnetism, according to PBS’s Nova.
While gravity's effects can clearly be seen on the scale of things like planets, stars and galaxies, the force of gravity between everyday objects is extremely difficult to measure. In 1798, British physicist Henry Cavendish conducted one of the world’s first high precision experiments to try to precisely determine the value of G, the gravitational constant, as reported in the Proceedings of the National Academy of Science's Front Matter.
Cavendish built what’s known as a torsion balance, attaching two small lead balls to the ends of a beam suspended horizontally by a thin wire. Near each of the small balls, he placed a large, spherical lead weight. The small lead balls were gravitationally attracted to the heavy lead weights, causing the wire to twist just a tiny bit and allowing him to calculate G.
Remarkably, Cavendish’s estimation for G was only 1% off from its modern-day accepted value of 6.674 × 10^−11 m^3/kg^1 * s^2. Most other universal constants are known to far higher precision but because gravity is so weak, scientists must design incredibly sensitive equipment to try to measure its effects. Thus far, a more precise value of G has eluded their instrumentation.
The German-American physicist Albert Einstein brought about the next revolution in our understanding of gravity. His theory of general relativity showed that gravity arises from the curvature of space-time, meaning that even rays of light, which must follow this curvature, are bent by extremely massive objects.
Einstein’s theories were used to speculate about the existence of black holes — celestial entities with so much mass that not even light can escape from their surfaces. In the vicinity of a black hole, Newton’s law of universal gravitation no longer accurately describes how objects move, but rather Einstein’s tensor field equations take precedence.
Astronomers have since discovered real-life black holes out in space, even managing to snap a detailed photo of the colossal one that lives at the center of our galaxy. Other telescopes have seen black holes’ effects all over the universe.
The application of Newton’s gravitational law to extremely light objects, like people, cells and atoms, remains a bit of an unstudied frontier, according to Minute Physics. Researchers assume that such entities attract one another using the same gravitational rules as planets and stars, but because gravity is so weak, it is difficult to know for sure.
Perhaps, atoms attract one another gravitationally at a rate of one over their distance cubed instead of squared — our current instruments have no way of telling. Novel hidden aspects of reality might be accessible if only we could measure such minute gravitational forces.