Newton's Laws And Other Apple Dropping Epiphanies
Newton's laws, according to my personal observations, are some of the most well known and familiar physics topics to the vast majority of people. I often meet people who, upon me introducing my love for astrophysics, automatically think "Newton!" and they aren't wrong, despite the thousands of other fantastic intricacies physics has to offer. So I thought, why not spotlight such a popular topic? Chances are those who impulsively think Newton represents all of physics only know the surface of what he did and his laws truly mean. Soon you'll begin to understand how much he did to advance science, and maybe even begin to believe he is the greatest physicist of all time. So, why don't we go ahead and knock this one right in the head? Pun very much intended.
Newton's early life
Have you ever wondered what past geniuse's lifestyles were like or even tried to copy them to see how the effects of their habits might change you? No, just me? Well, Newton certainly had a childhood I wouldn't want to recreate. Just two months before he was born his father died. His birth was on Christmas day, 1642. His mother remarried three years later, but left him in the care of his grandmother. During his early adolescence he recieved a basic education, but when he turned twelve he was sent to King's School in Grantham, England. He lived with a pharmascist where he would invent little trinkets like windmills powered my mice in the labratory. When he became older and it was apparent farming wasn't for him he entered school at Trinity college in Cambridge. He had to leave after earning his bachelors degree because of the plague outbreak. While he was home waiting for the disease to take its' course he started working on his laws. During this break he performed multiple basic experiments to test his gravity hypotheses. Once he went back to school he was able to test more thoroughly his ideas and when his talent was recognized he was offered a position as mathematics professor which he held for 27 years, starting at 27 years old. He also invented a new calculus, so yeah, he was a pretty cool guy. He actually might be the greatest scientist to have ever lived.
What did all those experiments lead to today?
Newton, like all scientists had his bat of failures, but his work on gravity has lasted the weathering of time and still is applied a lot in today's experiments, theories, and technologies. So what exactly do his laws mean? What do they do? Why are they important now? Well, let's start at the beginning, Copernicus. Copernicus explained the heliocentric universe long before Newton explained gravity's role in planetary motion. A heliocentric universe is exactly what it sounds like, the sun is in the center of the solar system and all the planets, are orbiting around it. This got Copernicus in a lot of trouble then, but most of us are grateful for him now, including me. Copernicus' ideas influenced Newton's thinking and perception of the universe, so we have him to thank as well.
It takes a bit of critical thinking to understand what I'm going to explain next. So, in order to determine the speed of earth's rotation we need to determine the distance it travels in a set amount of time. When you divide distance by time, you get speed. Let's try it with earth. Now, we can't be exact because the planets aren't all orbiting in perfect circles, but they are very close so we can make pretty good approximations by using some common known mathematical terms, pi and AU's. So one AU (astronomical unit) is 150 million miles (1.5*10^8) , and pi is obviously practically three. 2Ï€*radius= circumference. Now find how many seconds are in a year which is easy to determine from a calculator. This puts us at 3*10^7 in scientific notation. Okay, now we have all the components so put it together, and you get... 2*3(1.5*10^8)/(3*10^7)= 30 kilometers per second! That's how fast we are going around the sun, RIGHT NOW. Right where you are sitting, the earth is moving at top speeds. Anyway, you're probably thinking what does this have to do with Newton? All this math we did was more of a Kepler thing, but that's a topic for another day. Kepler's math, derived from Copernicus, paved the way for Newton. Newton, by studying Kepler, found that gravity is a radical force between objects proportional to 1/d^2. And that's where it all ties in. And proportions 100% come into play with inertia. Which is what Newton's first law is all about. Inertia is the property of matter where an object stays at rest until acted upon by an external force and/or remains in motion at the same velocity forever with no deacceleration or acceleration until acted upon by an external force. If you threw an apple in space it would never slow down and would keep moving forever and ever, unless it was obligerated by an similarly inertia induced asteroid of course. This is because space is a vaccum. There is no friction or air resistance. There's nothing to stop the apple. On earth, if I rolled an apple across a table it would stop because of friction. You know, the stuff that is created when you rub your socks on the carpet and then shock yourself. If the wind is blowing in the opposite direction of your rolled apple, it will slow down the speed of the apple as the force of air resistance acts upon it. You know that regular daily occurence where you throw a bowling ball and piece of paper off your roof? The paper falls slower right? Yes, but only due to air resistance. It's harder for air to affect something with the atomic makeup of a bowling ball than it is to mess with a piece of paper's destination, but when put in an airless vaccum the paper and bowling ball would hit the ground at the same time. This is because gravity is constant with a speed of 9.8 m/s. There's a cool video showing this experiment being performed. Link below.
Newton's second law states "force is equal to the change in momentum (mV) per change in time. For a constant mass, force equals mass times acceleration." You're probably familiar with f=ma as it is one of the most popular equations next to E=mc^2, but what does it mean? Well, it means that a smaller object with a great acceleration will have a greater force than an object with a larger mass but same acceleration. There are many forces that can act on any one object but adding up those forces is what causes what we call, acceleration. Vector diagrams were created to make this a simple concept and easier to calculate. Here's a photo of one that is balanced (no acceleration because forces= 0)
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Newtons 3rd law, and most popular law, states "for every action there is an equal and opposite re-action" This, as cliche as it is, is the most exciting law to me because it's so fun to think about and play around with. Stand up, how much do you weigh in kilograms? Let's use 64 kilograms as our example weight. Now, multiple your weight in Kg by gravity's constant of 9.8. That's how much you weigh in Newton's. Huge number right? So our 64 Kg is 627.2 N. That means 627.2 Newtons are pushing up this metaphorical person and how ever many newtons you calculated are pushing up on you. Makes sense intuitively right? If the force you are exerting on the floor didn't make the floor exert your same force back you'd fall through the carpet! This also explains why people float in space. Pretty awesome stuff.
Now that we know how all the laws work we can pull this back into orbit with planetary motion and gravity. We know we are moving at 30 km/sec but why? Why do we orbit instead of going in a straight line? Short answer, gravity. Long answer, gravity and magnetic attraction. You see, we're orbiting the sun. The sun is trying to pull us into her fiery depths, luckily we are far enough away to lessen the force and we exert force of our own hence Newton's third law. The earth has an elliptical orbit which is why we have perihelions and aphelions meaning it's not a perfect circle. In the simplest terms, the sun with the help of inertia is keeping us turning in a circle because it's pulling us towards it. We have our own force so we won't let it pull us into it, we just let it keep us running in circles. The forces in play during orbit also affect the tides of water on earth but we'll talk about that some other time. All in all, inertia keeps us in line. And we never have to worry about not orbiting correctly because when the sun dies, we die.
Newton had some amazing, beautiful, elegant ideas that we use and believe to this day. His accomplishments have never gone unnoticed and his laws continue to teach us every day. All that popularity he gets he truly deserves, and hopefully this article unfolded some unknown truths to accentuate more of him. All in all I ask you to make like Newton and keep learning about the universe even when there's a plague about, you never know what it could potentially lead to, and clear skies my friends.
Links: https://www.youtube.com/watch?v=E43-CfukEgs