Eratosthenes by EmmaCeccarelli https://padlet.com/emma_ceccarelli/1a58szcx61fk Circumference of the Earth en-us 2018-09-19 14:19:10 UTC 2023-06-15 14:01:29 UTC hello@padlet.com https://padlet-assets.s3.amazonaws.com/icons/Brightnessdown.png Who was he? emma_ceccarelli https://padlet.com/emma_ceccarelli/1a58szcx61fk/wish/285571277 Eratosthenes was a talented mathematician, geographer and astronomer.
He invented the armillary sphere which was a mechanical device used by early astronomers to demonstrate and predict the apparent movements of the stars in the sky.
He measured the circumference of the Earth
by noting the angles of shadows in two cities on the Summer Solstice, and by performing the right calculations using his knowledge of geometry and the distance between the cities, Eratosthenes was able to make a nearly exact calculation of the circumference of Earth.]]> 2018-09-25 15:01:31 UTC https://padlet.com/emma_ceccarelli/1a58szcx61fk/wish/285571277 How did he calculate the circumference of Earth? emma_ceccarelli https://padlet.com/emma_ceccarelli/1a58szcx61fk/wish/285571925 Eratosthenes lived in the city of Alexandria, in northern Egypt. He knew that on a certain day each year, the Summer Solstice, in the town of Syene in southern Egypt, there was no shadow at the bottom of a well. He realized that this meant the Sun was directly overhead in Syene at noon on that day each year.
Eratosthenes knew that the Sun was never directly overhead in his home city of Alexandria, even on the Summer Solstice,  but he realized that he could determine how far away from directly overhead the Sun was in Alexandria by measuring the angle formed by a shadow from a vertical object. He measured the length of the shadow of a tall tower in Alexandria, and used simple geometry to calculate the angle between the shadow and the vertical tower.


 

]]> 2018-09-25 15:02:13 UTC https://padlet.com/emma_ceccarelli/1a58szcx61fk/wish/285571925 emma_ceccarelli https://padlet.com/emma_ceccarelli/1a58szcx61fk/wish/285575226 Next, Eratosthenes used a bit more geometry to reason that the shadow's angle would be the same as the angle between Alexandria and Syene as measured from the Earth's center. Conveniently, 7.2 degrees is 1/50th of a full circle (50 x 7.2° = 360°). Eratosthenes understood that if he could determine the distance between Alexandria and Syene, he would merely have to multiply that distance by 50 to find the circumference of Earth! 
Eratosthenes's only tools were sticks, eyes, feet and brains]]> 2018-09-25 15:05:52 UTC https://padlet.com/emma_ceccarelli/1a58szcx61fk/wish/285575226 L' esperimento emma_ceccarelli https://padlet.com/emma_ceccarelli/1a58szcx61fk/wish/285596341 Grazie alle nostre insegnanti ci siamo recati alla spiaggia Lido di lghero il giorno dopo del solstizio (24 Settembre) per calcolare la circonferenza della terra .]]> 2018-09-25 15:30:16 UTC https://padlet.com/emma_ceccarelli/1a58szcx61fk/wish/285596341 Che strumenti abbiamo utilizzato? emma_ceccarelli https://padlet.com/emma_ceccarelli/1a58szcx61fk/wish/285598418 Abbiamo utilizzato un' asta lunga 100 cm, il metro, la calcolatrice scientifica e delle app per stabilire la copertura del cielo (1%), la direzione (Nord= Tramontana) e l'intensità (24 km/h ) del vento, la temperatura dell' aria (27°C),
e infine l'umidità (61%)]]> 2018-09-25 15:32:37 UTC https://padlet.com/emma_ceccarelli/1a58szcx61fk/wish/285598418 emma_ceccarelli https://padlet.com/emma_ceccarelli/1a58szcx61fk/wish/285609733 2018-09-25 15:46:02 UTC https://padlet.com/emma_ceccarelli/1a58szcx61fk/wish/285609733 Cosa abbiamo fatto? emma_ceccarelli https://padlet.com/emma_ceccarelli/1a58szcx61fk/wish/285610610 Abbiamo iniziato col appoggiare l'asta sulla sabbia nell'orario compreso dalle 12.00 e le 13.00, successivamente abbiamo misurato l'ombra che gettava (120 cm) avendo quindi il cateto maggiore (l' ombra) e il cateto minore (l'asta) di un triangolo rettangolo, abbiamo trovato l'ipotenusa applicando il teorema di Pitagora (146,45 cm) , successivamente abbiamo trovato l' angolo =40°, conoscendo la distanza tra l'Equatore e Alghero abbiamo stabilito la proporzione
d:α=C:360,
C=(d⋅360):α,
abbiamo trovato così la circonfernza della terra (intorno ai 4000000000 cm= 40000 km)

]]> 2018-09-25 15:47:00 UTC https://padlet.com/emma_ceccarelli/1a58szcx61fk/wish/285610610 emma_ceccarelli https://padlet.com/emma_ceccarelli/1a58szcx61fk/wish/285628038 2018-09-25 16:09:55 UTC https://padlet.com/emma_ceccarelli/1a58szcx61fk/wish/285628038 emma_ceccarelli https://padlet.com/emma_ceccarelli/1a58szcx61fk/wish/285728335 2018-09-25 18:39:24 UTC https://padlet.com/emma_ceccarelli/1a58szcx61fk/wish/285728335 emma_ceccarelli https://padlet.com/emma_ceccarelli/1a58szcx61fk/wish/285728724 2018-09-25 18:40:09 UTC https://padlet.com/emma_ceccarelli/1a58szcx61fk/wish/285728724 emma_ceccarelli https://padlet.com/emma_ceccarelli/1a58szcx61fk/wish/285729154 2018-09-25 18:41:04 UTC https://padlet.com/emma_ceccarelli/1a58szcx61fk/wish/285729154 La Nebulosa Aquila emma_ceccarelli https://padlet.com/emma_ceccarelli/1a58szcx61fk/wish/299447457 La Nebulosa Aquila (M16) è un giovane ammasso stellare dell’età di circa 2 milioni di anni, circondato dalle nubi di polveri e gas incandescente in cui si è formato.

]]> 2018-11-01 16:09:49 UTC https://padlet.com/emma_ceccarelli/1a58szcx61fk/wish/299447457 emma_ceccarelli https://padlet.com/emma_ceccarelli/1a58szcx61fk/wish/299450640 Questa immagine della regione, curata in ogni dettaglio, riprende icone cosmiche, sculture rese famose dalle osservazioni del telescopio Hubble, che ha immortalato primi piani del complesso di formazione stellare: i Pilastri della Creazione, dense, polverose colonne lunghe diversi anni luce, qui visibili vicino al centro, al cui interno stanno nascendo nuove stelle.]]> 2018-11-01 16:14:42 UTC https://padlet.com/emma_ceccarelli/1a58szcx61fk/wish/299450640 Collocazione emma_ceccarelli https://padlet.com/emma_ceccarelli/1a58szcx61fk/wish/299452224 La Nebulosa Aquila si trova a circa 7.000 anni luce di distanza, in direzione della Coda del Serpente.]]> 2018-11-01 16:17:07 UTC https://padlet.com/emma_ceccarelli/1a58szcx61fk/wish/299452224 emma_ceccarelli https://padlet.com/emma_ceccarelli/1a58szcx61fk/wish/299456295 2018-11-01 16:24:08 UTC https://padlet.com/emma_ceccarelli/1a58szcx61fk/wish/299456295 More about it... emma_ceccarelli https://padlet.com/emma_ceccarelli/1a58szcx61fk/wish/299461398 The Eagle Nebula suddenly burst upon the world’s collective consciousness in 1995, when the Hubble Space Telescope focused its attention on a dark nebula in the center of the Eagle.

The dark protrusions of dense gas were found to be the site of new star and solar system formation, and the resulting photograph became known as the Pillars of Creation and gave most people their first view of new stars and solar systems at the dawn of their creation.]]> 2018-11-01 16:33:03 UTC https://padlet.com/emma_ceccarelli/1a58szcx61fk/wish/299461398 emma_ceccarelli https://padlet.com/emma_ceccarelli/1a58szcx61fk/wish/299462420 Similar areas, such as the Stellar Spire on the left side of the Eagle, are also forming new stars, through a combination of processes. The cold, mostly hydrogen, gas of the nebula has already fueled the formation of a series of young, hot stars. As the gas continues to collapse under its own gravity into the dark forms we see, new stars and solar systems are formed and continue to grow as they attract more and more gas to them. However, the intense light pressure from the new stars that have formed and their solar winds are eroding away the dense, cold gas pockets, diminishing new star formation and dispersing the nebulae.]]> 2018-11-01 16:35:01 UTC https://padlet.com/emma_ceccarelli/1a58szcx61fk/wish/299462420 Ten Things to Know About Our Sun emma_ceccarelli https://padlet.com/emma_ceccarelli/1a58szcx61fk/wish/303136637 1
If the Sun were as tall as a typical front door, Earth would be about the size of a nickel.
2
The Sun is the center of our solar system and makes up 99.8 percent of the mass of the entire solar system.
3
At the equator, the Sun spins once about every 25 days, but at its poles the Sun rotates once on its axis every 35 Earth days.
4
As a star, the Sun is a ball of gas (92.1 percent hydrogen and 7.8 percent helium) held together by its own gravity.

]]> 2018-11-12 08:01:06 UTC https://padlet.com/emma_ceccarelli/1a58szcx61fk/wish/303136637 5 emma_ceccarelli https://padlet.com/emma_ceccarelli/1a58szcx61fk/wish/303137355 The Sun does not have any rings.
6
Many spacecraft constantly observe the Sun, helping us keep an eye on space weather that can affect satellites and astronauts.
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Without the Sun's intense energy, there would be no life on Earth.
8
The Sun's core is about 27 million degrees Fahrenheit (15 million degrees Celsius).
9
MOONLESS

But orbited by eight planets, at least five dwarf planets, tens of thousands of asteroids, and up to three trillion comets and icy bodies.
10
The Sun’s visible surface sometimes has dark sunspots, which are areas of intense magnetic activity that can lead to solar explosions.

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