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The History Of Astronomy

The History Of Astronomy

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Who we are? Where do we come from and where are we going? How and why was the Universe born? These are some of the eternal questions associated with astronomy that continue to pique human imagination from ancient times to the present day. Astronomy is the science that has as its main purpose the determination of the positions, dimensions and movements of the celestial bodies. So in this video we are going to talk about something magnificent that will help us understand the humanity’s perception over the years about astronomy. Let’s analyze and get deep into the history of astronomy.
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Astronomy is the oldest of the natural sciences and powerfully associated with religious, cosmological, and astrological beliefs. The first astronomers were the ones who could distinguish the planets and the stars due to the fact that they were the first ones that made observations and predictions.
From the beginning humanity turned its eyes to the sky full of awe and questions. The sunrise and sunset of the Sun, the phases of the Moon, the alternation of seasons, the movement of other planets in the sky, the appearance of comets and the shocking phenomenon of eclipses, were the first evidence that there is something above that needs to be discovered. That is how astronomy started to develop. These incidents raised our curiosity and made us wonder what are they? Where do they come from? We do know today but imagine in those days… they were like Gods.
As early as the 6th century BCE, ancient Greek philosophers documented evidence that Earth was a sphere. They noted that the night sky looked different when seen from various locations on Earth, hinting at our planet’s curved surface. They also observed the round shadow of Earth on the Moon during lunar eclipses. These philosophers were even able to calculate the circumference of Earth quite accurately. They did this by measuring the length of the shadow cast by an object at exactly the same time, in two different locations. Taking into account the distance between those two locations and the difference in the lengths of the shadows, they calculated that Earth’s circumference was about 46,250 kilometres. That is very close to the real value of 40,075 kilometres!
In the year 185, Chinese astronomers became the first to document a supernova. Several supernova explosions have been observed since then, including a particularly bright one in the year 1054, which (at its peak) was four times brighter than planet Venus, one of the brightest objects in the night sky. Some supernovae are even bright enough to be visible during the day!
The notion that our own galaxy – the Milky Way – is but one of trillions of other galaxies in the universe only dates back about a century. Before then, nearby galaxies were thought to be cloudy regions of the Milky Way. The first documented observation of the neighbouring Andromeda Galaxy was in the year 964 by a Persian astronomer who described it as a “nebulous smear.” For centuries, it was simply known in star charts as the “Little Cloud.”
Before the 16th century, Earth was commonly thought to be at the centre of the solar system, with all other celestial objects revolving around it. This is known as the geocentric model. This theory, however, did not match some confusing observations made by astronomers, such as the path of planets that appeared to move backwards on their orbits.
In 1543, Polish astronomer Nicolaus Copernicus proposed a heliocentric model of the solar system in which the planets orbit the Sun. This model explained the unusual path of planets that astronomers had observed. The new theory was one of many revolutionary ideas about astronomy that emerged during the Renaissance period.
The work of astronomers Tycho Brahe and Johannes Kepler led to an accurate description of planetary motions and laid the foundation for Isaac Newton’s theory of gravitation. This progress dramatically improved humanity’s understanding of the universe.
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Credits: Ron Miller
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What Is Our Place In The Milky Way?

What Is Our Place In The Milky Way?

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What is our place in the Milky Way? And our place in the Universe? In ancient times, many people had the idea our planet Earth to be at the centre of the Universe, as stated by Aristotle and Ptolomeus in their ptolemaic – aristotelic concept of universe: according to this model, Earth is at the center of the universe and all the other celestial bodies orbit around it. Today lots of people think the same. But is this really the case? To answer this question, let’s try to to a travel in the universe, through space and time; we will start our travel from our planet to reach, in the end, the extreme boundaries of the universe.
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During the 1600s, Galileo Galilei, the famous Italian astronomer, was one of the first people, during modern age, to have some doubts about the geocentric model of universe: thanks to telescopic observations, he was able to demonstrate our Earth is not at the rotation centre of planets and the Sun, but really it is the Sun itself. Moreover, observing planet Jupiter, he discovered that the giant planet is the rotation center for its moons. So, Galileo became aware that the center of the Solar System was the Sun, not the Earth!

The Solar System is made by a star, the Sun, eight planets and different types of minor celestial bodies, like comets, asteroids and dwarf planets.
Well, the Earth isn’t at the center of the Solar System, maybe is the closest planet to our Sun? No it isn’t, because it is only the third planet from the Sun: the closest planet to our star is Mercury, followed by Venus and then Earth. The Earth moves around the Sun, our star, just like all the other celestial bodies in the Solar System do: this implies that the Sun, and not our planet, is the center of rotation of the Solar System! The Earth takes a year, 365 days, to travel its orbit, and its average distance from the Sun is 150 million kilometers, which is the measure unit of distances in the Solar System known as the astronomical unit and abbreviated AU. Why do we talk about average distance? Because the orbit traveled by the Earth around the Sun is not circular but elliptical, and this means that there will be an aphelion (i.e. the point of the Earth’s orbit farthest from the Sun, just over 1 AU away from it) and a perihelion (the point of Earth’s orbit closest to the Sun, just under 1 AU). An alternative way to define the astronomical unit passes through the light time, in particular we can say that the average distance Earth – Sun is equal to about 8 light minutes: this means that sunlight takes 8 minutes to arrive on Earth, so that the sunlight we see at a certain moment is not that of that moment but it is the sunlight which left from the Sun 8 minutes earlier! In other words: if the sun went out for example at 2.30 pm, we would only notice it at 2.38 pm! Or again: if you could travel aboard the Star Wars Millennium Falcon it would take you only 8 minutes to travel from the Sun to the Earth (when in reality it takes a few years). To give a more concrete idea of the dimensions of the Solar System: if the Sun were a sphere with a diameter of 14 cm, Pluto would be at 700 m from the Sun, like seven regular soccer fields!

The nearest celestial body to Earth is the Moon, our satellite: to reach it you should take three days off! It’s the same time taken by Apollo astronauts to cover the distance of nearly 400 thousand kilometers that separate Moon and Earth. But if you had Star Trek Enterprise, and travel at maximum curvature, you would only take less than 2 seconds to reach the Moon!

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Credits: Mark A. Garlick / markgarlick.com
Credits: Ron Miller
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#InsaneCuriosity #MilkyWay #Galaxies

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Io: Jupiter's Volcanic Moon!

Io: Jupiter's Volcanic Moon!

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From the discovery of the moon, to what makes it so volcanic, and more! Join us as we explore Io: Jupiter’s Volcanic Moon!
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8. The Discovery Of Io
In many ways, Io is one of the more popular moons of Jupiter. It’s been referenced many a time as we’ll note later. But how did we learn about this very special moon?
The first reported observation of Io was made by Galileo Galilei on 7 January 1610 using a 20x-power, refracting telescope at the University of Padua. However, in that observation, Galileo could not separate Io and Europa due to the low power of his telescope, so the two were recorded as a single point of light. Io and Europa were seen for the first time as separate bodies during Galileo’s observations of the Jovian system the following day, January 8th, 1610 ( this is used as the discovery date for Io by the IAU).
The discovery of Io and the other Galilean satellites of Jupiter was published in Galileo’s Sidereus Nuncius in March 1610. In his Mundus Jovialis, published in 1614, Simon Marius claimed to have discovered Io and the other moons of Jupiter in 1609, one week before Galileo’s discovery. Galileo doubted this claim and dismissed the work of Marius as plagiarism. Regardless, Marius’s first recorded observation came from 29 December 1609 in the Julian calendar, which equates to January 8th, 1610 in the Gregorian calendar, which Galileo used. Given that Galileo published his work before Marius, Galileo is credited with the discovery.
But the end of the “discovery” did not end there. Because for basically 250 years various astronomers tried to learn more about Io. But because of its place in space all they could usually see was a ball of light. It would take a while for them to start to parse out the details of the moon.
Improved telescope technology in the late 19th and 20th centuries allowed astronomers to resolve (that is, see as distinct objects) large-scale surface features on Io. In the 1890s, Edward E. Barnard was the first to observe variations in Io’s brightness between its equatorial and polar regions, correctly determining that this was due to differences in color and albedo between the two regions and not due to Io being egg-shaped, as proposed at the time by fellow astronomer William Pickering, or two separate objects, as initially proposed by Barnard. Later telescopic observations confirmed Io’s distinct reddish-brown polar regions and yellow-white equatorial band.
Telescopic observations in the mid-20th century began to hint at Io’s unusual nature. Spectroscopic observations suggested that Io’s surface was devoid of water ice (a substance found to be plentiful on the other Galilean satellites).
So as you can see, this wasn’t just a discovery of trying to find the moon, but to try and understand what it was and what it was like in regards to its very nature. Which would be further expanded upon in the future via attempts to explore the moon with probes and satellites.
7. The Exploration of Io Part 1
In the late 1960s, a concept known as the Planetary Grand Tour was developed in the United States by NASA and the Jet Propulsion Laboratory (JPL). It would allow a single spacecraft to travel past the asteroid belt and onto each of the outer planets, including Jupiter, if the mission was launched in 1976 or 1977. However, there was uncertainty over whether a spacecraft could survive passage through the asteroid belt, where micrometeoroids could cause it physical damage, or the intense Jovian magnetosphere, where charged particles could harm sensitive electronics.

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“If You happen to see any content that is yours, and we didn’t give credit in the right manner please let us know at: Lorenzovareseaziendale@gmail.com and we will correct it immediately”

“Some of our visual content is under a Attribution-ShareAlike license. ( in it’s different versions such as 1.0, 2.0, 3,0 and 4.0 – permitting comercial sharing with attribution given in each picture accordingly in the video.”

Credits: Ron Miller
Credits: Nasa/Shutterstock/Storyblocks/Elon Musk/SpaceX/Esa
Credits: Flickr
Credits: JPL/ university of arizona/ DLR/goddard/scientific visualization studio/SwRi/MSSS/UCLA/USGS
wellcome images
burkhard mùche
horst frank -commonswiki
volcanopele at english wikipedia
rick guidice/Robbie Shade/ Lunar and Planetary Institute/Mailset

#InsaneCuriosity #IoMoon #TheSolarSystem

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Callisto: Jupiter's Cratered Moon!

Callisto: Jupiter’s Cratered Moon!

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From its discovery, to its importance around Jupiter, and more! Join us as we explore Callisto, Jupiter’s Moon.
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9. Discovery and Naming Of Callisto
Callisto was discovered Jan. 7, 1610, by Italian scientist Galileo Galilei along with Jupiter’s three other largest moons: Ganymede, Europa and Io.
Artemis. Who was also the goddess of the moon for the record. The name was suggested by Simon Marius soon after Callisto’s discovery. Marius attributed the suggestion to Johannes Kepler.
However, the names of the Galilean satellites fell into disfavor for a considerable time, and were not revived in common use until the mid-20th century. In much of the earlier astronomical literature, Callisto is referred to by its Roman numeral designation, a system introduced by Galileo, as Jupiter IV or as “the fourth satellite of Jupiter”.
Now though it’s known as Callisto by most texts, including ones you’ll see in school in hear about when moons like these are discovered. The desire to keep things simple while also rooting much naming in mythology has been desired by astronomers in earlier decades.
8. Orbit and Rotation
Callisto is the outermost of the four Galilean moons of Jupiter. It orbits at a distance of approximately 1,170,000 miles (26.3 times the radius of Jupiter itself). This is significantly larger than the orbital radius of the next-closest Galilean satellite, Ganymede. As a result of this relatively distant orbit, Callisto does not participate in the mean-motion resonance—in which the three inner Galilean satellites are locked—and probably never has.
Like most other regular planetary moons, Callisto’s rotation is locked to be synchronous with its orbit. The length of Callisto’s day, simultaneously its orbital period, is about 16.7 Earth days. Its orbit is very slightly eccentric and inclined to the Jovian equator, with the eccentricity and inclination changing quasi-periodically due to solar and planetary gravitational perturbations on a timescale of centuries. These orbital variations cause the axial tilt (the angle between rotational and orbital axes) to vary between 0.4 and 1.6°.
The dynamical isolation of Callisto means that it has never been appreciably tidally heated, which has important consequences for its internal structure and evolution. Its distance from Jupiter also means that the charged-particle flux from Jupiter’s magnetosphere at its surface is relatively low—about 300 times lower than, for example, that at Europa. Hence, unlike the other Galilean moons, charged-particle irradiation has had a relatively minor effect on Callisto’s surface. The radiation level at Callisto’s surface is equivalent to a dose of aCallisto is named after one of Zeus’s many lovers in Greek mythology. Callisto was a nymph (or, according to some sources, the daughter of Lycaon) who was associated with the goddess of the hunt, bout 0.01 rem per day, which is over ten times higher than Earth’s average background radiation.
6. Surface Of The Moon
Callisto’s rocky, icy surface is the oldest and most heavily cratered in our solar system. The surface is about 4 billion years old and it’s been pummeled, likely by comets and asteroids. Because the impact craters are still visible, scientists think the moon has little geologic activity—there are no active volcanoes or tectonic shifting to erode the craters. Callisto looks like it’s sprinkled with bright white dots that scientists think are the peaks of the craters capped with water ice.
The moons of Jupiter have been something of a fascination for many astronomers and scientists. So when the Earth had the ability to look at the moons via satellites and probes they almost literally jumped at the chance. To the extent that Callisto has been visited many times of the last several decades.
The Pioneer 10 and Pioneer 11 Jupiter encounters in the early 1970s contributed little new information about Callisto in comparison with what was already known from Earth-based observations ironically enough.
The real breakthrough happened later with the Voyager 1 and Voyager 2 flybys in 1979. They imaged more than half of the Callistoan surface with a resolution of 1–2 km, and precisely measured its temperature, mass and shape. A second round of exploration lasted from 1994 to 2003, when the Galileo spacecraft had eight close encounters with Callisto, the last flyby during the C30 orbit in 2001 came as close as 138 km to the surface.

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