Today’s post is a special A to Z Challenge edition of Sciency Words, an ongoing series here on Planet Pailly where we take a look at some interesting science or science related term so we can all expand our scientific vocabularies together. In today’s post, G is for:
GRAVITY
We’ve all heard the story about how Isaac Newton discovered gravity.
But Newton’s discovery was not just that objects fall to the ground. Other people had noticed this before.
Newton’s real breakthrough was realizing that the same force which causes apples to fall also holds the Moon in its orbit around the Earth. Previously, it had been assumed that earthly physics here on the ground must be different from the celestial physics of the Moon, the planets, and the stars.
This is why Newton called his discovery the law of universal gravitation: because he believed his law must apply no matter where you are in the universe. Of course Newton didn’t know the planet Mercury was “breaking the law,” so to speak, nor did he know about black holes.
But I don’t want to get into Einstein and general relativity. Not today, at least. For today’s post, I just want to focus on the word gravity itself. Where did that word come from?
I used to think it was really cool how a scientific term like gravity had spread out and acquired additional shades of meaning in the English language. Think of a phrase like “the gravity of the situation,” where gravity means something like importance or seriousness.
But I’ve since learned that it actually happened the other way around. English originally borrowed gravity from French, and the word can be traced back to Latin. It originally meant something like dignified or serious. It could also mean weighty, in the sense of either metaphorical or literal weightiness.
But the idea of defining gravity as a physical force permeating the universe, causing objects to be attracted toward one another—that’s apparently an invention of Newton and his contemporaries. So now I think it’s really cool how science can take a word we already had and give it a whole new meaning.
Next time on Sciency Words: A to Z Challenge, we’ll talk about humans. Oh no, wait… that’s not my pick for the letter H. I have a much more interesting H-word to talk about; but humans will be involved.
Planet Pailly 
I didn’t know about Mercury.
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It’s a very interesting story. In Newton’s time, telescopes we’re sensitive enough to detect the anomaly, but by the 20th Century astronomers had noticed the problem and were having a really, really hard time explaining it.
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I’ve seen some persnickety physicists make a distinction between “gravity” and “gravitation”, asserting that the first word is for the other pre-scientific meanings you mentioned and the second for the fundamental attraction force between objects with mass. But it doesn’t seem like the wider culture is paying attention.
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I’ve heard that too. I think this is an issue of formal vs. informal discourse. If you’re writing a paper for publication in an astrophysical journal, you should probably stick to “gravitation,” but physicists I’ve met don’t seem to worry about it in more casual settings (like chatting with some nerdy Sci-Fi writer).
On the other hand, I did have a conversation once with a physicist about gravitational waves, and there was some confusion between us because I was using “gravity waves” and “gravitational waves” interchangeably. Turns out those are two completely different and unrelated phenomena.
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Of course, Newton was clever enough to realize that his universal law of gravitation was merely a descriptive model of something mysterious and unknown. He wasn’t happy about this and wrote:
“It is inconceivable that inanimate Matter should, without the Mediation of something else, which is not material, operate upon, and affect other matter without mutual Contact…That Gravity should be innate, inherent and essential to Matter, so that one body may act upon another at a distance thro’ a Vacuum, without the Mediation of any thing else, by and through which their Action and Force may be conveyed from one to another, is to me so great an Absurdity that I believe no Man who has in philosophical Matters a competent Faculty of thinking can ever fall into it. Gravity must be caused by an Agent acting constantly according to certain laws; but whether this Agent be material or immaterial, I have left to the Consideration of my readers.”
Post Einstein, we have some clue as to what is going on (the action of mass-energy on spacetime itself – an effect that propagates at the speed of light), but still no real grip on the physical mechanism at work.
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That’s another thing that I truly admire about Newton. He understood that his “laws” were modeling reality, they were not a reality in and of themselves. It’s an important distinction.
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That is interesting. I would have thought science before colloquialism as well.
G is for Gardasil—Is It Safe?
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Yeah, I was really surprised when I found out it was the other way around.
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It is always fascinating how the language evolves and give new meaning to old worlds.
Thanks for this great post 🙂
@JazzFeathers
The Old Shelter – 1940s Film Noir
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Yes, I love studying how words evolve over time. There are even words that have gone from meaning one thing to meaning the exact opposite. Language is crazy!
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What a great post. I’d have also guessed it went the other way, from the scientific use to the metaphorical one. It’s cool to trace things backward like that to find out where they came from.
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Yeah, it’s one of my favorite things: learning how words change over time. Sometimes in ways that really don’t make sense.
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Yeah. French is a great source of those kinds of words, and lots of English words. There’s a lot of metaphor built in. Nothing to do with science but just the other day, but, for inatance, I learned the origin of “dessert” is “to clear the table,” rather than anything to do with ice cream.
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The detection of the gravitational waves produced by the merger of two neutron stars –GW170817– has allowed scientists to fix at 70 km/s per megaparsec * the value of the increase in speed of the expansion of the universe in the 130 million light years that separate us from the origin of said merger.
As these calculations approach the speed of light throughout the age of the universe, we can do the inverse calculation to determine the average increase in the velocity of expansion so that the observable universe is of the age stated by the Big Bang Theory.
The result is 300.000 km/s /(13.799/3,26) Mpc =70,820 km/s Mpc. https://molwick.com/en/gravitation/072-gravitational-waves.html#big-bang
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I’m sorry to say I haven’t been keeping up with the latest news about gravitational waves. Too much other stuff on my plate right now. But it’s really exciting to hear about all the unknowns or best guesses that we’re now pinning down with hard data.
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