I told him. I told him already when he had made Funny Folks No. 1. And that's a year ago. But Ferran Requejo just loves to talk about things he knows almost zilch about. (Not that he's much better when he talks about his field of expertise.) Now he's come out with this rubbish.
Says Requejo: "First H.S. Leavitt calculated, from the so-called Cepheids, the brightness (from the duration of one complete pulsation, 1908)."
Wrong. Leavitt observed that some stars had a variable brightness, and that this variation followed regular periods. She established that brighter Cepheids had a longer period. And that this correlation offered predictable results. Obviously, she could only observe the brightness of the Cepheids, but she was well aware that she was dealing with their luminosity. What else!
Requejo continues: "Thereafter, E. Hertzsprung (1913) and H. Shapley (1918) managed to translate the values of brightness of Leavitt in terms of luminosity."
No. The only thing that was left to be done was calibration: to find a few Cepheids close enough to measure their distances by parallax. Once that was achieved, the period logs of all Cepheids could be used to determine their distances relative to Earth. And that's how Hertzsprung and Shapley started measuring the universe. Leavitt's method is still in use today. She let us see beyond the narrow limits of parallax and discover other galaxies.
Henrietta Swan Leavitt gave us the "standard candle", mankind failed to give her the Nobel Prize.
What she does not deserve is to be remembered in such an obscure text, that even linguistically is so flawed it reveals the author's underlying ignorance. See the "from... from" mess in the first sentence quoted, and others you might discover yourselves if you read Catalan. (Hint: What's that with the "amount of light energy per square meter and per second" and the following sentences?)
Just stop it, Requejo. Nobody needs your "analogies" or "metaphors". You only use them to present yourself as a well read and well educated person. But since they regularly go awry, they simply show that you ain't. And what you really are.
I've said it before, you're a snake-oil seller.