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Marco A. Lopez-Sanchez

@marcoalopez.fediscience.org.ap.brid.gy

An Earth scientist who's interested in the physical properties of rocks and minerals working at the Andalusian Earth Sciences Institute (IACT-CSIC) in Granada […] 🌉 bridged from ⁂ https://fediscience.org/@marcoalopez, follow @ap.brid.gy to interact

55 Posts17 Follower10 Folgt
Thiago Ferrer Morini@tferrer.journa.host.ap.brid.gy · 2mo ago

Esto significa... que no sabemos nada. La proyección de la televisión pública SVT pronostica 175 votos para el bloque de centroizquierda (S, V, MP, C) y 174 para las derechas (M, SD, KD, L), con una diferencia de 20.000 votos (de cerca de seis millones) entre ambos

Benito Fuentes@metbeni.bsky.social · 3mo ago

🟥 ROJO Un posible plan B sería acudir a zonas altas (montañas) pues la nubosidad será baja. Pero esto no garantiza nada, pues el sol estará muy cerca del horizonte y, posiblemente, escondido tras la capa de estratocúmulos.

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Vicky Veritas@vickyveritas.bsky.social · 3mo ago

28 days until #MinCup26! Thanks, Kerstin! ⚒️ sci-fi 🧪 🖖🏼 scifi Geosciences #WomenInSTEM geology 🔭🪐

Kerstin Neuhaus@microtopico.bsky.social · 3mo ago

This is amber. It looks like a rock, but does not count as one. If you would like to learn more about rocks and minerals: in four weeks, it's time again for this year's #Mineral Cup, where we search the mineral of the year 2026. Find out more: www.mineralcup.org #MinCup #MinCup26 #Minerals ⚒️

Amber necklaces, two large and several small pieces of amber.
Benito Fuentes@metbeni.bsky.social · 5mo ago

Arriba, una previsión ficticia para el 18-ago-2050 emitida por la televisión francesa en 2014, advirtiendo sobre el futuro que nos aguarda ⌚️📈 Abajo, la previsión meteorológica para el 22-jun-2026.

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John D. Cook@johndcook.mathstodon.xyz.ap.brid.gy · 5mo ago

Another Gaussian approximation https://www.johndcook.com/blog/2026/05/31/another-gaussian-approximation/

Another Gaussian approximation

The function (1 + cos(_x_))/2 gives a fair approximation to the Gaussian density exp(− _x_ ²) You can make the approximation much better by raising it to a power. The function ((1 + cos(_x_))/2)4 gives a good lower bound and ((1 + cos(_x_))/2)3.5597 gives a good upper bound. More on that here. There are other ways of improving the cosine approximation to the Gaussian. Yesterday I came across one I hadn’t seen before, adding a sin(_x_) term to _x_. (1 + cos(sin(_x_) + _x_))/2 This function matches the first few terms of the power series for exp(− _x_ ²) and has an error on the order of _x_ 6/240. You can’t see the difference between the two functions in a plot for −4 ≤ _x_ ≤ 4. *** There’s a tension between the previous two statements. If the error in on the order of _x_ 6/240 then we’d expect the error to be huge at _x_ = 4. We have 46/240 = 17.07 and yet exp(−4²) − ((1 + cos(4 + sin(4)))/2) = −0.002579, i.e. the error is between 3 and 4 orders of magnitude smaller than we might expect. We have an alternating series, so the truncation error should be roughly equal to the first term after the truncation, right? No, the alternating series theorem doesn’t apply because the absolute values of the terms in the series are not decreasing yet for _x_ = 4. The terms have to decrease eventually because the series has infinite radius of convergence, but they’re not decreasing at the 6th term; the terms will get much larger in absolute value before they get smaller. The basic alternating series theorem gives only an upper bound on truncation error, but there are extensions that also give a lower bound. I wrote about these extensions a few weeks ago. But these extentions don’t apply here because the terms have not started decreasing in absolute value.

johndcook.com

Antonio Martínez Ron@aberron.bsky.social · 7mo ago

"El editor de la revista debe excluir a Barbacid de publicar nuevas contribuciones en un plazo no inferior a un par de años y el CNIO debería clarificar la continuidad de su relación contractual" Isidro F. Aguillo — Responsable del Laboratorio de Cibermetría del CSIC