In 1907, Albert Einstein presented the world with a startling truth about our universe. Gravity, he realized, isn't quite as strange and mysterious as it feels.
Rather, it's kind of the same thing as acceleration -- a force we're very used to thinking about on the regular. He called it the equivalence principle, and soon, this eye-opening concept would blossom into the mind-bending theory of general relativity. The rest, as they say, is history.
On Monday, however, engineers with the California Institute of Technology revealed a fascinating new plot point to the story of humanity's gravitational musings -- and it has to do with none other than the renaissance genius himself, Leonardo da Vinci.
As it turns out, not only was da Vinci painting stunning masterpieces in the late 15th and early 16th century like the Last Supper and the Mona Lisa, but was also conducting gravity experiments of his own. For years, he'd been scribbling down equations and drawings about the elusive force that anchors us to Earth, written in old Italian in notebooks such as the recently released Codex Arundel.
He even did it in his signature mirrored penmanship, the researchers say, which simply refers to da Vinci's tendency to write everything backward for secrecy.
What's especially striking about these inscriptions is how da Vinci seems to have been on the right track.
In his notes, he'd begun decoding the strange correlation between gravity and acceleration -- similar to what enamored Einstein about 400 years later. Da Vinci's ideas about gravity preceded even Isaac Newton's formal announcement of the universal law of gravitation in 1687 and Galileo Galilei's law of parabolic fall, which dictates how objects falling in a gravitational field behave, brought to light in 1604.
"The fact that he was grappling with this problem in this way -- in the early 1500s -- demonstrates just how far ahead his thinking was," Mory Gharib, a professor of aeronautics and medical engineering at Caltech and lead author of the paper published in the journal Leonardo, said in a statement.
Here's a quick thought experiment about how gravity and acceleration are related.
Imagine standing in a nonmoving elevator on Earth. OK, now imagine standing in an elevator in space that's accelerating upward with a force exactly equivalent to the force of gravity (9.8 meters/second^2).
If there weren't any windows on these elevators, how could you tell if you were in the space one or Earth one? You couldn't.
Well, how about this: What if you had to figure out if you were in a non-windowed elevator that wasn't moving in space and one on Earth that was falling so you experienced weightlessness? Still nope.
Weightlessness on Earth in the presence of gravity feels just like weightlessness in space in what we'd normally consider "zero-gravity." So, what in the world is gravity?
Well, at risk of simplification, it's just a fancy way to think about stuff interacting while accelerating in different directions.
One way to think about this is that if a ball were rolling horizontally toward the edge of the cliff, once it reaches the end of the cliff, it won't really be pulled down by some weird unseen force. It's just that there wouldn't be a cliff to hold the ball up anymore, so its trajectory, and therefore direction of acceleration, couldn't be purely horizontal anymore either. The ball would instead be accelerating on a vertical trajectory.
And according to a press release on the recent study, da Vinci was onto that last bit.
[...] His notes also suggest he started trying to mathematically describe the inner workings of the falling object over time in general, attempting to measure how downward objects increased in acceleration as seconds went by. This is related to gravitational theories put forth by Newton and Galileo, too.
Journal Reference:
Gharib, Morteza, Roh, Chris, Noca, Flavio. Leonardo da Vinci's Visualization of Gravity as a Form of Acceleration, Leonardo (DOI: 10.1162/leon_a_02322)
(Score: 0) by Anonymous Coward on Thursday February 16, @01:30PM
It's the stench man, the stench.
(Score: 3, Insightful) by JoeMerchant on Thursday February 16, @02:09PM (2 children)
Didn't Newton basically invent Calculus in order to mathematically describe things like the relationship of gravity, velocity and position?
Not that nobody had ever done such things before Newton, just that he didn't "stand on the shoulders" of those particular giants when working out his own things which happened to get into the enduring literature.
Україна досі не є частиною Росії Слава Україні🌻 https://news.stanford.edu/2023/02/17/will-russia-ukraine-war-end
(Score: 2) by driverless on Friday February 17, @08:39AM (1 child)
However in this case we're looking at Da Vinci's work with 20:20 hindsight, taking something he played with and then, with 22nd-century knowledge, saying that he could have discovered F if he'd just done A, then B, then C, then D, and then E. All I'm seeing is signs of a brilliant, curious mind that explored lots of things and then moved on.
Retroengineering modern technical knowledge into historic stuff has been a problem for a long time, google "Baghdad battery" for the poster-child example.
(Score: 2) by JoeMerchant on Friday February 17, @12:33PM
Yeah, I was particularly enjoying the explanation using an elevator, in outer space.
Україна досі не є частиною Росії Слава Україні🌻 https://news.stanford.edu/2023/02/17/will-russia-ukraine-war-end
(Score: 5, Interesting) by gznork26 on Thursday February 16, @02:24PM (2 children)
How long do I have?
Over a short time, the two experiences might be identical, but we're riding in a rotating gravity well. That accelerating elevator would be on a linear trajectory, but if there was time, the one standing on Terra could be revealed with a Foucault pendulum.
For extra credit, what would the path of that space elevator have to be in order to replicate the experience?
(Score: 2) by istartedi on Thursday February 16, @05:18PM (1 child)
I'm guessing the space elevator would just have to slowly rotate about the axis parallel to the direction in which it's accelerating. Another way to tell where you are is that you can't accelerate at 1g indefinitely. Eventually you get to some fraction of c, and then it gets harder and harder to keep it up, eventually requiring astronomical amounts of energy. A clever operator with the right power plant and control system might be able to wait for the occupant to sleep, then quickly snap around and decelerate. You just might think it was a bad dream, or the burrito you ate. The operator might also be able to conserve energy by "boiling the frog", gradually reducing acceleration and this might not be obvious until it dramatically influenced the trajectories of thrown objects, or the occupant weighed themselves.
Appended to the end of comments you post. Max: 120 chars.
(Score: 3, Insightful) by ChrisMaple on Saturday February 18, @05:47AM
It depends upon your frame of reference. Inside that accelerating elevator, the force you feel in the absence of gravity always has the same proportion to acceleration. In the elevator's frame of reference, that elevator can accelerate at 1 g forever, and the speed of light still appears the same in all directions. An observer in an inertial ("non-moving") frame of reference would think he's observing the effect you describe, and conclude (wrongly) that as the elevator approached the speed of light it wasn't accelerating as much.
The observed phenomena are relative to the frame of reference, that's why it's called relativity.
(Score: 4, Informative) by Immerman on Thursday February 16, @03:24PM
Not quite. Einstein said gravity is just things traveling in straight lines through curved space *without* accelerating.
What we experience as the force of gravity on Earth is not actually gravity, but instead the surface of the Earth constantly accelerating us upwards in opposition to the straight-line non-accelerating path we'd otherwise follow.
(Score: 2) by Rosco P. Coltrane on Thursday February 16, @04:43PM (4 children)
Gravity, just like acceleration, is not a force. For an article that purports to explain what relativity is about, that's kind of a bummer.
So yeah... Don't get your science from CNET.
(Score: 4, Informative) by StupendousMan on Thursday February 16, @05:40PM (3 children)
University astronomer here (and member of a physics department). My colleagues and I all treat gravity as a force, and we teach that it is a force. I'm not sure why you think gravity isn't a force; can you explain?
(Score: 2, Funny) by Rosco P. Coltrane on Thursday February 16, @05:54PM (2 children)
Why sure: let me Google that for you [googlethatforyou.com]
What university do you teach at, so I never send my kids to it?
(Score: 4, Funny) by khallow on Thursday February 16, @06:58PM (1 child)
Maybe you needed to do a different search that confirms your biases rather than refutes them?
(Score: -1, Flamebait) by Anonymous Coward on Thursday February 16, @10:51PM
What do you think he is, a Democrat?