Newton's laws have not had examples in real life that would nullify his laws, — god must be atheist

What do you make of the 1919 eclipse that confirmed Einstein and disproved Newton?

https://en.wikipedia.org/wiki/Eddington_experiment

What do you make of the 1919 eclipse that confirmed Einstein and disproved Newton? — fishfry

Newton's laws have been showed to work in special cases of the law that explained the 1918 experiment.

Newton's Laws were not refuted, but expanded with adding some special conditions under which N's laws were not useful.

Same thing as to say, (conceptual example follows) "Primes are consecutive non-zero positive integers", if you can only count to three. Once you learn about the numeral four, and the concept of four, you have to rework your claim, while your oginal claim is still true up to no. 3.

So your reworked claim will become, "All non-zero positive odd integers are prime", if you can only count to 8. Then you come to learn about "9", and you need to revise your claim again. Your third claim will not contradict your second claim if you only consider integers to 8.

Thank you everyone for your responses. I would only like to know how Newton knew his laws are true. What were the experiments he performed? — Fernando Rios

Maybe this way: how do you know you're you?

Thank you everyone for your responses. I would only like to know how Newton knew his laws are true. What were the experiments he performed? — Fernando Rios

Newton didn’t do any experiments with regard to his laws of motion and gravity*. He believed that Kepler’s laws of a heliocentric model of the solar system, with its elliptical orbits, were true because of their predictive power and that they were formulated due to an analysis of Tycho Brahe’s comprehensive and accurate data of celestial observations. He also believed that Galileo was right about motion being relative and that objects fell at the same rate regardless of mass (overturning the contemporary prevalent view of Aristotelian motion).

With Kepler's planetary laws and his invention of differential calculus, Newton devised his universal law of gravity and with the experimental results of Galileo (my example prior being a modern interpretation of such an experiment) he devised his three laws of motion. Personally I don’t care whether Newton thought himself to be right, or Brahe, Kepler, and Galileo either. Because, as with most geniuses, they were insufferable arseholes who thought everything they did was true and correct. Honestly, each and every one of these people were know-it-all pricks who were about as welcome at parties as a fart in a crowded lift (elevator to my colonial cousins). But then again, I would’ve liked to party with Brahe as he seemed to be a larger-than-life character. He had a tin nose due to losing his own nose in a duel! He also made Kepler practically beg for his observational data (like I said, an arsehole!)

Why everyone else thought Newton’s Laws were true was because the laws themselves had great predictive power and his genius was (besides coming up with calculus) that his laws explained how the celestial and terrestrial bodies move all due to being bound by gravity. The idea that celestial and terrestrial movement were the same thing wasn’t even considered beforehand and the simplified elegance of this probably gave reason why Newton himself thought his laws true. Newton didn’t know why gravity (he didn’t even know precisely what the gravitational constant was) and so he credited God with this feat. It wasn’t until Einstein came along that a naturalistic account for gravity was given. Newton also admitted to a certain artifice to his calculations as he was acutely aware that messing about with numbers didn't prove anything empirical.

Incidentally due to Newton’s thin skin towards criticism and his dislike for other academics (especially Robert Hooke.Newton’s quote about standing on the shoulders of giants was a sarcastic dig at Hooke’s diminutive size) he sat on his calculations and it wasn’t until he was befriended by the astronomer Edmund Halley that he decided to tell of his findings. Even if Newton thought his laws were true, it seemed that he wasn’t that bothered if other people thought them true also.


*Newton was a theoretician about motion and gravity but it’s not to say he didn’t dabble with experiments himself. When formulating his theory of colour, he stuck a bodkin in his eye to see how this changed his perception of colour. Also in his later years, he dabbled in alchemy.

What's wrong with you? — Tzeentch

:kiss:

Absolute nonsense. Like I said, you need revise your conception of truth in line with fallibilism.

Newton's laws have not had examples in real life that would nullify his laws, but CONCEPTUALLY they may happen — god must be atheist

It actually has happened. General Relativity shows that the force of gravity, as conceptualized by Newton's laws does not exist. That was one of the main issues that troubled Einstein: What is this "long invisible arm" that extends out of masses and reaches out to other masses?

Through the formulation off GR he showed that space and time are inseparable, that space-time curves around a mass, and that this curved space-time affects the movement of objects.

Newton would say the satellite orbiting earth is kept in orbit because the force of Earth's gravity is balanced by the satellite's centrifugal force.
Einstein would say the satellite is experiencing no force, it is simply moving through curved space-time.

Newton's laws are no laws at all. They are a mathematical representation of what Newton observed. Same with Einstein's theory of relativity. They are models approximating the real laws of the universe.

The actual, real laws of the universe are unknown to man, and although the perpetually evolving models and theories keep inching closer, there are still many important observations that can not be reconciliated with the latest theories.

to the OP, by asking the question of how can Newton's laws be proven to be true, there is an implication that they are true, and they are not. No present physics theory is true, and you can't prove the truth of something that is not true.

You're wrong. It's not true that the statement, "Force equals mass times acceleration", is untrue.

You're wrong. It's not true that the statement, "Force equals mass times acceleration", is untrue. — S

You got me there.

You can't. If by prove you mean the same sort of "proof" required in math. In sciences you try to see whether or not something is the case. In math where "proof" is generally used, you try to prove whether or not something MUST be the case. You can't prove whether or not Newton's laws must be the case but you can prove whether or not they are the case with good accuracy (through experiment)

Didn't you read past the opening post? He clarified that by "prove", he means show to be the case. And we're obviously talking about science, not maths. This can and has been done with regards to Newton's three laws of motion, for example.

In summary, Newton's laws boil down to f=ma. An enormous quantity of physical science has been developed by applying this simple mathematical law to different physical situations.

Newton's Three Laws of Motion.

The correct answer isn't, "You can't". It's, "They have been".

In summary, Newton's laws boil down to f=ma.

f = ma is essentially a definition. A very clarifying definition to be sure, but it's not a fact or a theorem. It's a definition. That is my understanding.

Thank you everyone for your responses. I would only like to know how Newton knew his laws are true. What were the experiments he performed? — Fernando Rios

Newton's laws of motion aren't true, they can't be proven logically or experimentally, they are a framework, useful to some extent.

Newton's 2nd law is a definition of the concept of Force. Newton defines Force as the product of mass and acceleration: if some object of mass m accelerates at the rate a, it is said by definition that there is a force F = m*a acting on it. It would be more accurate and less confusing to call it a definition rather than a 'law'.

From this definition it follows that if an object doesn't accelerate, that is if it is at rest or in uniform motion in a straight line, then there is no force acting on it: this is Newton's 1st 'law', merely a consequence of the above definition. Newton stated it first because he took it from Descartes:

Descartes’ first two laws of nature: the first states “that each thing, as far as is in its power, always remains in the same state; and that consequently, when it is once moved, it always continues to move”, while the second holds that “all movement is, of itself, along straight lines” (these two would later be incorporated into Newton’s first law of motion)

These two Descartes 'laws' were also a framework, not statements which could be proven logically or experimentally. It's not hard to imagine why he formulated these laws. Most things do not move along straight lines and do not always continue to move, but for instance when we let a solid ball roll on a flat surface it seems to keep moving in a straight line unless its course is stopped or changed by an obstacle or by the wind or by some other thing, so there is the desire to see uniform motion in a straight line as the state of natural motion, the simplicity and beauty of it is attractive. Descartes believed that the universe was created and preserved by God, so he looked at the universe through that lens.

It would be equally valid to come up with ugly 'laws' of nature instead, saying that the natural motion of things is chaotic, that things do not remain in the same state, and then only in rare circumstances do these chaotic motions combine to create a temporary uniform motion in a straight line. That's a different framework, a different way to look at the world, equally valid. But Descartes wanted to see simplicity and beauty as the basis of the universe, as signs of God's perfection, rather than chaos. Same goes with Newton.


Once Newton's 1st and second laws are taken as a basis, then by definition when an object stops moving uniformly in a straight line there is a force acting on it, of magnitude m*a. We can't know what force is acting on an object without measuring its acceleration, because Force is not defined independently from F = m*a, and that's precisely why F = m*a is the definition of Force in Newton's framework. When students are told to calculate the acceleration of an object knowing the force that is acting on it, this is stupid because in practice in order to calculate the magnitude of the force acting on it we had to measure its acceleration in the first place.

So what's the point of these two laws? Well we could do away with them, but here's an example to show how they can be a practical tool. Let's say you carry out a specific experiment on some object (let's call it object 1), and each time you repeat the experiment you measure that the object always accelerates at the same rate. Then you take some other object (object 2) and carry out the experiment on it, and you measure that it accelerates at half the rate of the other object, every time. Then you take a third object (object 3) and you measure that it accelerates 3 times faster than the first object, and 6 times faster than the second one.

One useful way to look at this is to say that there is a constant force applied on these objects, and that the different acceleration is due to the objects having a different resistance to acceleration. For instance you can say that object 2 resists acceleration twice more than object 1, and 6 times more than object 3. This resistance to acceleration is what is called 'mass'. If you define object 1 as the reference (mass m1 = 1), then you define object 2 as having mass m2 = 2, and object 3 as having mass m3 = 1/3.

And that's where F = m*a becomes useful, because as it turns out in many experiments these objects will have the same relative acceleration. For instance if you carry out another experiment with object 1 and measure its acceleration, you can predict how fast the other two objects will accelerate before carrying out the experiment with them, you can predict that object 2 will accelerate twice less and object 3 three times more. It doesn't work for all experiments, but it works often enough that Newton's framework is useful. Although in my view it would be less confusing to do away with Newton's laws completely, because you don't need the concept of force nor even of mass to make the same predictions.


Newton's 3rd 'law' can be seen as a definition of Mass. Mass is a relational quantity, to say that an object has mass m2 = 2kg is the same as saying that in many experiments it accelerates twice less than a reference object that is defined to have a mass m1 = 1kg. So the ratio of their masses is by definition the inverse ratio of their accelerations: m2/m1 = a1/a2, or m1*a1 = m2*a2. In experiments where they interact with one another (through an elastic collision for instance), they accelerate in opposite directions, so a1 and a2 have opposite signs, so m1*a1 = -m2*a2, which is Newton's 3rd 'law'.


Newton's laws are basically definitions of the concepts of force and mass. Mass is defined as relative resistance to acceleration, force is defined as mass times acceleration, and in that framework when objects don't move uniformly in straight lines we say a force is acting on them. The reason this framework works to some extent, is that in many different situations different objects have the same relative acceleration. Which leads to the concept of mass, which leads to the concept of force.

Examples of experiments that have led to this framework are observations of collisions, experiments with pendulums, with springs, observations of celestial bodies, more generally observations of motion, ...

The OP was "I would like to know how you can prove these laws". I explained that the answer depended on what you mean by proof. No where was this:

He clarified that by "prove", he means show to be the case. — S

Said.

Thank you for confirming that you didn't get as far as even the fourth post from the opening post. There's only like five or so sentences between the opening post and his clarification.

"show they are true" can also be interpreted both ways..... Either empirical or axiomatic proof. I was saying that you can't prove newton's laws axiomatically in the same way you can prove that the sum of angles in a triangle is always 180.

"show they are true" can also be interpreted both ways..... Either empirical or axiomatic proof. I was saying that you can't prove newton's laws axiomatically in the same way you can prove that the sum of angles in a triangle is always 180. — khaled

No, it can't really be interpreted both ways when the context is clearly science, not maths.