【Creative Cultivation Program】Where is Newton's apple?

Author: The Nutcracker Studio

The great scientist Isaac Newton discovered gravity from a falling apple, which is a classic science story known to everyone. If we judge it by the current idea of ​​"traffic is king", this story has many characteristics of high dissemination, such as being dramatic, touching, grand and down-to-earth. Because it is so famous, many people have heard of it in elementary school.

Did this incident really happen, or was it invented by later generations? Let's first look at how the popular version describes it.

Isaac Newton, who was in his early 20s and had just graduated from Cambridge University, returned to his hometown in East Midlands to avoid the plague in the city. One day, an apple fell from a tree and hit Newton on the head. He began to think about related physics problems and then realized the law of universal gravitation.

If we compare this story with the rigorous history of science, we will find many details that do not stand up to scrutiny.

One of the publication time

On July 5, 1687, Newton published his book "Mathematical Principles of Natural Philosophy". In this book, he first expounded the law of universal gravitation: every point of mass attracts every other point of mass by a force directed along the line of intersection of the two points. The force is proportional to the product of the two masses and inversely proportional to the square of the distance between them.

Newton was 44 years old that year, and more than 20 years had passed since the apple hit him on the head. Of course, it takes a certain amount of time from inspiring inspiration to finally obtaining research results, but more than 20 years is too long.

Secondhand manuscript

Newton's scientific manuscripts over the years have been well preserved, and future generations can study his manuscripts to explore his scientific research process. In Newton's research manuscripts from his youth, there is no content related to "gravity". If Newton began to study issues related to universal gravitation in his 20s, why is there no record? Did he just think about all the issues about gravity in his mind, and persisted in thinking about them for more than 20 years? This is also very unreasonable.

So, how did the story of an apple hitting the head spread? Let's trace back to the source and find the first person to tell this story. The earliest version that can be verified is in 1726 (when Newton was 83 years old), when Newton's niece Catherine Barton and nephew-in-law John Candut began to tell the story to the world. Candut wrote in his manuscript:

In 1666 he again left Cambridge and returned to his mother in Lincolnshire. While walking contemplatively in a garden it occurred to him that gravity (which causes an apple to fall from a tree) was not confined to a limited distance around the Earth, but extended much farther than was usually supposed. Why not, he said to himself, be as high as the Moon - if so, that would surely have an effect on her motion - perhaps keep her in her orbit, and he began to calculate what the effect of such an assumption would be.

(This paragraph is translated from Wikipedia)

In 1727, Voltaire wrote in his Essay on Epic Poetry, “Sir Isaac Newton, walking in his garden, first conceived his system of gravity, and then saw an apple fall from a tree.”

In his Reminiscences of the Life of Sir Isaac Newton, the writer John Stukeley recorded that once when he and Newton were having afternoon tea and chatting, Newton mentioned that it was the falling of an apple that inspired him to think about gravity. Of course, this was just a retelling, and John Stukeley himself did not see the apple fall.

The famous astronomer Sir Harold Spencer Jones said in 1944 that the story of the apple falling on the head was probably true, but he later reversed his statement, saying one cannot be sure either way.

In summary, the story of Newton's inspiration from the falling apple came out very late, nearly 40 years later than the law of gravity itself. At that time, Newton himself was already in his twilight years. If this story is true and really happened to Newton in his 20s, why was it not disclosed until he was old, and there is no trace of it happening?

Because it is so unreasonable, the current mainstream view is that this story was fabricated by Newton's relatives and friends in his later years. After hearing it, Newton himself acquiesced to the spread of this story. After all, it is interesting and can increase his own legendary status.

This special apple has indeed helped spread the scientific principle itself with its dramatic effect. Many people have indeed remembered the scientific name "universal gravitation" because of this apple. But then again, one of the elements of the scientific spirit is "truth-seeking", so today, we have to take a serious attitude to explore an apple from hundreds of years ago. I think Newton himself would not object to our fussing.

Everything is for the truth.

This article is produced by Science Popularization China-Starry Sky Project. Please indicate the source when reprinting.