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I understand that Einstein was able to draw remarkable conclusions and was set on the path of General relativity when he realized that a falling observer not feeling his own weight.

But is it believed that Einstein was actually the first person to realize specifically this weightlessness idea? I do think in those days when (perhaps) the only people who experienced weightless for a significant period of time died from it. It was only after planes and parachutes (and I don't know how many parachute jumps had been made before Einstein thought about this) that people could have really experienced weightlessness. Elevators I guess dropped enough that a momentary reduction in weight could be felt. But even elevators were fairly rare.

(An aside is, I am pretty sure trains and the need for accurate/synchronized clocks played a role in general relativity although not sure if scientists like Heaviside were inspired by trains and clocks.)

But did not Newton understand 200 years before Einstein that an object in orbit was actually falling and someone inside such an object would not feel his own weight? Or was he basically uninterested in what a hypothetical human "aboard" such a satellite -- he just cared about the orbit of the object itself.

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    $\begingroup$ Not only did Newton not think of it, but even Jules Verne in From the Earth to the Moon (1865) did not describe the phenomenon correctly. He thought that the weightlessness will result only at the "neutral point" where the gravities of the Earth and the Moon balance. I do not know who was first, but Tsiolkovsky, inspired by Jules Verne, gave a correct account in his technical and science fiction writings of 1890s, see Pearson. $\endgroup$
    – Conifold
    Nov 29, 2022 at 8:35
  • $\begingroup$ @Conifold: I sure admire Tsiolkovsky. A great man who produced under adverse circumstances. Also, seemed to be thinking about space flight almost too early, years before the Wright brothers flew in the atmosphere. I think he deserves more recognition. $\endgroup$
    – releseabe
    Jan 13, 2023 at 21:06

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It was only after planes and parachutes (and I don't know how many parachute jumps had been made before Einstein thought about this) that people could have really experienced weightlessness.

Your sense of history is a little off if you don't know that balloons and airships were before airplanes.

As it happens, someone who was sort of a relative of mine made their first solo flight at the age of nine, which might still be the world record, and that was years before the Wright brothers.

On 19 September, 1789, a duck, a sheep and a rooster made the first balloon flight by living animals. The first manned balloon flight flight was on 21 November 1789.

Louis-Sébastien Lenormand (May 25, 1757 – April 4, 18371) was a French chemist, physicist, inventor, monk, and a pioneer in parachuting.

He is considered as the first man to make a witnessed descent with a parachute and is also credited with coining the term parachute, from the Latin prefix para meaning "against", an imperative form of parare = to avoid, avert, defend, resist, guard, shield or shroud, from paro = to parry, and the French word chute for "fall", hence the word "parachute" literally means an aeronautic device "against a fall". After making a jump from a tree with the help of a pair of modified umbrellas, Lenormand refined his contraption and on December 26, 17831 jumped from the tower of the Montpellier observatory in front of a crowd that included Joseph Montgolfier, using a 14-foot parachute with a rigid wooden frame.

https://en.wikipedia.org/wiki/Louis-S%C3%A9bastien_Lenormand

André-Jacques Garnerin (31 January 1769 – 18 August 1823) was a French balloonist and the inventor of the frameless parachute. He was appointed Official Aeronaut of France.

Garnerin began experiments with early parachutes based on umbrella-shaped devices and carried out the first frameless parachute descent (in the gondola) with a silk parachute on 22 October 1797 at Parc Monceau, Paris (1st Brumaire, Year VI of the Republican calendar).2 Garnerin's first parachute was made of white canvas[citation needed] with a diameter of approximately 23 feet (7 m).3 The umbrella was closed before he ascended, with a pole running down its center and a rope running through a tube in the pole, which connected it to the balloon.2 Garnerin rode in a basket attached to the bottom of the parachute; at a height of approximately 3,000 feet (1,000 m) he severed the rope that connected his parachute to the balloon.2 The balloon continued skyward while Garnerin, with his basket and parachute, fell.2 The basket swung violently during descent,[Note 1] then bumped and scraped when it landed, but Garnerin emerged uninjured.2

His student Jeanne Geneviève Labrosse, who later became his wife, was both a balloonist and the first female parachutist. Labrosse first flew on 10 November 1798, one of the earliest women to fly in a balloon, and on 12 October 1799, Labrosse was the first woman to parachute, from an altitude of 900 meters.[11]

https://en.wikipedia.org/wiki/Andr%C3%A9-Jacques_Garnerin

So people were making parcute jumps for more than a century before Einstein. And some of htem might have experienced weightlessness for some time before opening their paracutes.

A number of people have survived falling from heights of tens or hundreds of feet. Thus the sport of making high jumps or dives into water began.

Cliff diving has been documented as far back as 1770 when Kahekili II, king of Maui, engaged in a practice called "lele kawa", which in English means jumping feet first into water from great heights without making a splash.[6] The king's warriors were forced to participate to prove that they were courageous and loyal to the king. The practice later developed into a competition under king Kamehameha I, and divers were judged on their style and amount of splash upon entering the water.

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

On May 19, 1885 Robert Odlum was the first person to jump off the Brooklyn Bridge, and was fatally injured. Steve Brody claimed to have survived jumping off the Brooklyn Bridge onJuly 23, 1886, and the first confirmed survivor of a jump off the Brooklyn Bridge was Larry Donvan.

Lawrence "Larry"4 M. Donovan, born Lawrence Degnan5 or possibly Duignan2 (18623 – August 7, 18885) was a newspaper typesetter who became famous for leaping from bridges, first around the northeastern United States, and later in England. Inspired by the first successful Brooklyn Bridge jump by Steve Brodie, Donovan sought fame and fortune by leaping off that bridge, the Niagara Falls Suspension Bridge, and Bristol's 250 foot Clifton Suspension Bridge. Slightly injured on a couple of occasions and frequently incarcerated following his attempts, he struggled to capitalise on his fame, making money only through bets and brief periods working as an emcee or exhibiting himself in novelty shows. In August 1888, disillusioned and desperately poor, he accepted a spontaneous two-pound wager to jump from London's Hungerford Bridge late at night, but drowned in the attempt.

https://en.wikipedia.org/wiki/Larry_Donovan_(bridge_jumper)

So some 19th century persons could talk about what it felt to be in free fall for several seconds.

I note that Jules Verne in From the Earth to the Moon was not the only 19th century writer of stories of space flight, and maybe some of them depicted weightlessness more accurately.

The First Men in the Moon is a scientific romance by the English author H. G. Wells, originally serialised in The Strand Magazine from December 1900 to August 1901 and published in hardcover in 1901,4 who called it one of his "fantastic stories".5

On the way to the Moon, they experience weightlessness, which Bedford finds "exceedingly restful".[7]

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

"The Brick Moon" is a novella by American writer Edward Everett Hale, published serially in The Atlantic Monthly starting in 1869. It is a work of speculative fiction containing the first known depiction of the launch of an artificial satellite.

"The Brick Moon" was first released serially in three parts in The Atlantic Monthly in 1869.2 A fourth part, entitled "Life on the Brick Moon", was also published in The Atlantic Monthly in 1870.5 It was collected as the title work in Hale's anthology The Brick Moon and Other Stories in 1899.3

And I believe that Hale described weightlessness on the Brick Moon in orbit.

Somnium (Latin for "The Dream") — full title: Somnium, seu opus posthumum De astronomia lunari — is a novel written in Latin in 1608 by Johannes Kepler, and first published in 1634 by Kepler's son, Ludwig Kepler.

Kepler describes acceleration and deceleration on the journey to the moon and might also describe weightlessness.

Someone would have to read these, and many other space travel stories written before Relativity to see which ones might say that weightlessness in space travel is similar to the weightlessness feld when falling freely in a gravitational field.

edia.org/wiki/Louis-S%C3%A9bastien_Lenormand

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  • $\begingroup$ "December 26, 17831" is still a long way off ... $\endgroup$ Dec 3, 2022 at 2:29
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It is not clear what group of people you are discussing, scientists or "general public". People well educated in science certainly understood this (Jules Verne did not belong to this category). And speaking of the everyday experience, many people did experience weightlessness, namely when submerged in water. Human body has about the same density as water.

Einstein has nothing to do with this, since all this is explained by classical mechanics.

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  • $\begingroup$ u say this but einstein, a pretty smart guy, sounded like it was a big revelation. $\endgroup$
    – releseabe
    Nov 29, 2022 at 14:05
  • $\begingroup$ @releseabe: My understanding is that Einstein was interested in how being weightless away from gravitational effects (e.g. in outer space, appropriately distant from any planet, moon, star, etc.) was different from being weightless when in free fall in a gravitational field. In particular, when falling directly towards the center of a massive body (so, for example, excluding being in orbit about the body), two objects falling together will tend to approach each other, whereas in outer space they'll remain the same distance apart. (continued) $\endgroup$ Nov 29, 2022 at 18:28
  • $\begingroup$ It wasn't the fact that falling induces weightlessness -- surely any physicist would have known this -- but rather how the two situations are different, and also whether there are any "local" differences (i.e. differences that remain when you let the the regions being investigated approach a point). At least, this is my not-particularly-knowledgeable understanding of the issue. $\endgroup$ Nov 29, 2022 at 18:29
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Galileo recognized that falling objects don't exert a weight upon other falling bodies:

Note that it is necessary to distinguish between heavy bodies in motion and the same bodies at rest. A large stone placed in a balance not only acquires additional weight by having another stone placed upon it, but even by the addition of a handful of hemp its weight is augmented six to ten ounces according to the quantity of hemp. But if you tie the hemp to the stone and allow them to fall freely from some height, do you believe that the hemp will press down upon the stone and thus accelerate its motion or do you think the motion will be retarded by a partial upward pressure? One always feels the pressure upon his shoulders when he prevents the motion of a load resting upon him; but if one descends just as rapidly as the load would fall how can it gravitate or press upon him? Do you not see that this would be the same as trying to strike a man with a lance when he is running away from you with a speed which is equal to, or even greater, than that with which you are following him? You must therefore conclude that, during free and natural fall, the small stone does not press upon the larger and consequently does not increase its weight as it does when at rest.

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