astronomy.bigb

= Astronomy
{wiki}

<Ciro Santilli> likes to learn astronomy a bit like he learns geography: go down some lists of "stuff that seems most relevant in some criteria to us!", possibly at different size scales e.g.:
* <stars nearest to the Sun>
* <brightest natural objects in the sky>
* <galaxies nearest the Milky Way>
* <black holes nearest to the Sun>

= Amateur astronomy
{parent=Astronomy}
{wiki}

= Good targets for amateur astronomy
{parent=Amateur astronomy}

Looking at most <astronomical object> through a <telescope> is boring because you only see a white ball or point every time. Such targets would likely only be interesting with <spectroscopy> analysis.

There are however some objects that you can see the structure of even with an <amateur telescope>, and that makes them very exciting.

Some good ones:
* <The Moon>, notably crater detail.
* <Saturn>. Clearly visible to the naked eye, but looks like a ball. But under an amateur telescope, you can clearly see that there is a disk. Clearly discerning that the disk is a ring, i.e. seeing the gap, is a bit harder though.
* <Jupiter>. Clearly visible to the naked eye, it is quite huge. The four <Galilean moons>, being <Earth>-sized, are incredibly clearly visible, tested on <Celestron NexStar 4SE> 25mm/9mm eyepiece. Colored gas clouds are hard though, you will likely just see it bright white. https://www.reddit.com/r/telescopes/comments/35xrbb/how_can_i_see_the_color_of_jupiter_with_my/
* a <double star>. As mentioned at https://www.relativelyinteresting.com/10-astronomical-targets-new-telescope/ https://en.wikipedia.org/wiki/Albireo[Albireo] are incredibly separated. Also it is is easy to find manually being in a major well known constellation. It is no wonder it is not quite even known if they are gravitationally bound or not!
* <Andromeda Galaxy>. This is when things start getting hard. You can see a faint cloud, but it is not super clear that it has a center.

  One important understanding is that <it is not possible to see stars outside of the Milky Way by naked eye>.

  It is at this point that you start to learn that pictures of faint objects require longer term exposure and averaging of the images taken. For this you need:
  * a digital camera attached to the scope
  * a computerized scope that slowly moves to track the point of interest
  * image processing software that does the averaging
  Just looking through the scope to immediately see something is not enough.

  <video Andromeda Galaxy with only a Camera, Lens, & Tripod by Nebula Photos (2020)> gives a good notion of expectation adjustment.

Bibliography:
* https://www.relativelyinteresting.com/10-astronomical-targets-new-telescope/

= Astronomer
{parent=Astronomy}
{wiki}

= Antony Hewish 
{c}
{parent=Astronomer}
{tag=1974 Nobel Prize in Physics}
{wiki}

\Image[https://upload.wikimedia.org/wikipedia/en/4/49/Antony_Hewish.jpeg]

\Video[https://www.youtube.com/watch?v=P5Vlu5K_IWM]
{title=Antony Hewish - Working on Martin Ryle's telescope by Web of Stories}

= Astronomical measurement unit
{parent=Astronomy}
{tag=Unit of measurement}

= Astronomical unit
{parent=Astronomical measurement unit}
{title2=AU}
{title2=distance to the Sun}
{wiki}

= Apparent magnitude
{parent=Astronomical measurement unit}
{wiki}

= Brightest natural objects in the sky
{parent=Apparent magnitude}
{wiki=List_of_brightest_natural_objects_in_the_sky}

https://en.wikipedia.org/wiki/List_of_brightest_natural_objects_in_the_sky

= Star outside the Milky Way
{parent=Brightest natural objects in the sky}

<It is not possible to see stars outside of the Milky Way by naked eye>.

With <telescopes> however, it is possible. https://www.quora.com/Can-we-distinguish-individual-stars-in-other-galaxies-or-would-it-be-equivalent-to-say-we-know-there-are-other-forests-of-stars-galaxies-but-we-cant-tell-the-individual-trees-stars-What-is-the-farthest-individual/answer/Jerzy-Micha%C5%82-Pawlak contains an amazing answer that mentions two special cases of the furthest ones:
* <#gravitational lensing> observation
* a star that is far but visible because its light is reflected by a nearby #nebulae

But what we can definitely see are <#globular clusters> of galaxies. E.g. the article https://en.wikipedia.org/wiki/Messier_87 basically gauges the size of galaxies by the number of <#globular clusters> that they contain.

= It is not possible to see stars outside of the Milky Way by naked eye
{parent=Brightest natural objects in the sky}

We can't see individual stars outside of the <Milky Way>:
* https://physics.stackexchange.com/questions/26023/do-all-the-individual-stars-that-we-can-see-in-the-night-sky-belong-to-milky-way
* https://earthsky.org/tonight/can-we-see-stars-outside-our-milky-way-galaxy/
Any single star outside of the Milky Way cannot be seen.

The <Large Magellanic Cloud> stands out as the brightest thing we can see from outside the <Milky Way> by far!

= Proper motion
{parent=Astronomical measurement unit}
{wiki}

Some stars are so close that we can actually see their angles move with time due to the relative motion between them and the <Sun>, e.g. <Proxima Centauri>!

= Astrophysics
{parent=Astronomy}
{wiki}

A fancy name for <astronomy> ;-)

= Cosmic ray
{parent=Astrophysics}
{tag=1936 Nobel Prize in Physics}
{wiki}

\Video[https://www.youtube.com/watch?v=PCB8nv4fatc]
{title=CosmicPI: Detecting Cosmic Rays with a <Raspberry Pi> by <Marco Reps> (2021)}

= Particle discovered with cosmic rays
{parent=Cosmic ray}

* <positron>, later confirmed with <gamma ray> experiments by <Carl David Anderson>
* <muon>
* <pion>
* <kaon>

= Mountain used for cosmic ray experiments
{parent=Cosmic ray}

* https://en.wikipedia.org/wiki/Mount_Wilson_(California)[Mount Wilson]
* https://en.wikipedia.org/wiki/Pic_du_Midi_de_Bigorre[Pic du Midi]
* https://en.wikipedia.org/wiki/Chacaltaya[Chacaltaya]

= Ultra-high-energy cosmic ray
{parent=Cosmic ray}
{wiki}

Sometimes it feels like this could be how we finally make experiments to see what the <theory of everything> looks like, a bit like the first high energy experiments were from less exotic <cosmic rays>.

= Greisen-Zatsepin-Kuzmin limit
{c}
{parent=Ultra-high-energy cosmic ray}
{wiki=Greisen–Zatsepin–Kuzmin_limit}

= Oh-My-God particle
{parent=Ultra-high-energy cosmic ray}
{wiki}

= Age of the universe
{parent=Astronomy}
{wiki}

<Surely You're Joking, Mr. Feynman> chapter An Offer You Must Refuse (a play on words on <The Godfather (1972)>) has an interesting historical mention from the early 1950s while at <Caltech>:
> The next day, I had the greatest luck in making a decision. God must have set it up to help me decide. I was walking to my office, and a guy came running up to me and said, "Hey, Feynman! Did you hear what happened? Baade found that there are two different populations of stars! All the measurements we had been making of the distances to the galaxies had been based on Cephid variables of one type, but there's another type, so the universe is twice, or three, or even four times as old as we thought!"

  I knew the problem. In those days, the <age of Earth>[earth appeared to be older] than the universe. The earth was four and a half billion, and the universe was only a couple, or three billion years old. It was a great puzzle. And this discovery resolved all that: The universe was now demonstrably older than was previously thought. And I got this information right away - the guy came running up to me to tell me all this.

= Big Bang
{c}
{parent=Age of the universe}
{wiki}

= Cosmic microwave background
{parent=Big Bang}
{tag=1978 Nobel Prize in Physics}
{wiki}

= CMB
{c}
{synonym}
{title2}

If you point a <light> detector to any empty area of the sky, you will still get some light.

The existence of this is quite mind blowing, since "there is nothing there emitting that light".

To make sense of how it is possible to see this light, you can think of the universe as the <expanding raisin bread model>, but it expands faster than light (thus the existence of the <cosmological event horizon>), so we are still receiving light form the middle, not the borders.

<CMB> is basically perfectly <black-body radiation> at 2.725 48 <Kelvin>[K], but it has small variations with variations of the order of 200 microKelvin: <cosmic microwave background anisotropy>.

= Cosmic microwave background anisotropy
{parent=Cosmic microwave background}
{tag=2006 Nobel Prize in Physics}

There is a slight variation in temperature of <CMB> across the sky of the order of 200 microKelvin. It is small to the ~2.7 K average temperature, but it can be measured.

If the <initial conditions> of the <Big Bang> and the <laws of physics> were perfectly symmetric, then we could expect the <universe> to just be one perfectly uniform boring soup.

But instead some asymetry made all the fun weird things we see today happen eventually, like <galaxies> and <life>.

And the <cosmic microwave background> serves as a way for us to look back in time to the early conditions of the universe, as it was set in stone as soon as the universe became transparent to this <light> during <recombination (cosmology)>.

Or if you want to get poetic, it is the closest we can ever get to listening to the original word of <God> when he setup the <initial conditions> of the universe.

The ansiotropies of CMB is the ultimate astronomical compass we will ever have, as it is the thing with the least <proper motion>.

\Image[https://upload.wikimedia.org/wikipedia/commons/3/3c/Ilc_9yr_moll4096.png]
{title=<Cosmic microwave background anisotropy> measured by the <Wilkinson Microwave Anisotropy Probe>}
{disambiguate=ansiotropy}

= Wilkinson Microwave Anisotropy Probe
{c}
{parent=Cosmic microwave background anisotropy}
{title2=2001-2010}
{title2=WMAP}
{wiki}

\Image[https://upload.wikimedia.org/wikipedia/commons/3/3c/Ilc_9yr_moll4096.png]
{title=<Cosmic microwave background anisotropy> measured by the <Wilkinson Microwave Anisotropy Probe>}

= Epoch
{disambiguate=astronomy}
{parent=Big Bang}

If looking through these don't make you think of the <Book of Genesis> then nothing will.

= Recombination
{disambiguate=cosmology}
{parent=Epoch (astronomy)}
{wiki}

= Expansion of the universe
{parent=Big Bang}
{wiki}

= Hubble's law
{c}
{parent=Expansion of the universe}
{wiki}

= Cosmological event horizon
{parent=Expansion of the universe}
{wiki}

<expansion of the universe>

= Expanding raisin bread model
{parent=Expansion of the universe}

\Image[https://upload.wikimedia.org/wikipedia/commons/thumb/a/ac/Raisinbread.gif/250px-Raisinbread.gif]

= Inflation
{disambiguate=cosmology}
{parent=Expansion of the universe}
{wiki}

= Astronomical object
{parent=Astronomy}
{wiki}

= Galaxy
{parent=Astronomical object}
{wiki}

= Quasar
{parent=Galaxy}
{wiki}

= Messier object
{c}
{parent=Astronomical object}
{title2=1774}
{wiki}

What an awesome list the dude compiled. Contains many of the features we care the most about of the sky, since of course, <apparent magnitude> is a big determinant of that.

= Planetary system
{parent=Astronomical object}
{wiki}

= Planet
{parent=Astronomical object}
{wiki}

= Star
{parent=Astronomical object}
{wiki}

= Double star
{parent=Star}
{wiki}

= Binary star
{parent=Double star}
{wiki}

= Star system
{parent=Star}
{wiki}

= Polaris
{c}
{parent=Star system}
{title2=433 ly}
{title2=1.8m}
{wiki}

= North Star
{c}
{synonym}
{title2}

= Stellar classification
{parent=Star}
{wiki}

= Neutron star
{parent=Stellar classification}
{wiki}

Neutron stars are cool. What weird objects!

= Neutron star merger
{parent=Neutron star}
{wiki}

\Video[https://www.youtube.com/watch?v=xIthgcx-axs]
{title=Neutron star merger visualized by Max Planck Institute for Gravitational Physics}

= Pulsar
{parent=Neutron star}
{wiki}

This is one of those things that when astronomers first saw them they went "oh fuck we've found <extraterrestrial life>".

= Binary pulsar
{parent=Pulsar}
{tag=Binary star}
{wiki}

= Jocelyn Bell Burnell
{c}
{parent=Pulsar}
{wiki}

\Video[https://www.youtube.com/watch?v=NDW9zKqvPJI]
{title=I Changed Astronomy Forever. He Won the Nobel Prize for It by New York Times Opinion}
{description=Many good footage and recreations from <Mullard Radio Astronomy Observatory>}

= Magnetar
{c}
{parent=Pulsar}
{wiki}

\Video[https://www.youtube.com/watch?v=jRPjgKs-aw4]
{title=<Magnetars>: <Neutron Stars> but Scarier! by Learning Curve}

= List of magnetars
{parent=Magnetar}

= SGR 1806-20
{parent=List of magnetars}
{wiki}

= Main sequence
{parent=Stellar classification}
{wiki}

= Supernova
{parent=Stellar classification}
{wiki}

= Black hole
{parent=Stellar classification}
{wiki}

= Micro black hole
{parent=Black hole}
{wiki}

= Black holes nearest to the Sun
{parent=Black hole}
{wiki=List_of_nearest_known_black_holes}

Interesting to note that there are quite a few nearer than <Sagittarius A>, as of 2022 we know of one at 1.5 <kly>: https://universemagazine.com/en/discovered-the-closest-black-hole-to-the-sun/

It is interesting that a few months earlier there seemed to be no known specific black holes in the <Milky Way>: https://www.nasa.gov/feature/goddard/2022/hubble-determines-mass-of-isolated-black-hole-roaming-our-milky-way-galaxy although their count is estimated to be in the hundreds of millions.

For comparison, remember that the <Milky Way> is 185 <kly> in diameter x 2 <kly> thick.

= Constellation
{c}
{parent=Astronomy}
{wiki}

= IAU designated constellations
{c}
{parent=Constellation}
{wiki}

Cover up the entire sky in a compatible way with the traditional constellations. They are also very square, the boundaries consisting only of vertical and horizontal lines on the sphere.

= Asterism
{disambiguate=astronomy}
{parent=Constellation}
{wiki}

Basically a mini-<Constellation>.

= Big Dipper
{c}
{parent=Asterism (astronomy)}
{wiki}

= Space exploration
{parent=Astronomy}
{wiki}

= Space exploration organization
{parent=Space exploration}
{wiki}

= NASA
{c}
{parent=Space exploration organization}
{wiki}

= Radio astronomy
{parent=Astronomy}
{wiki}

<Radio astronomy> is cool because it revealed:
* some very interesting new types of <astronomical objects> that were not as noticeable in the <visible spectrum> notably:
  * <quasars>: quasars are extremely #redshifted[], which means by <Hubble's law> that they are very far from <Earth>, so the fact that we could see them at all meant they must have produced immense amounts of light
  * <pulsars>: scientists thought they had found <extraterrestrial life> when they saw these regularly pulsating signal sources!
* <cosmic microwave background> which is a major evidence for the <Big Bang>
* radio wavelengths penetrate <Earth's atmosphere> better than the <visible spectrum> making it easier to make ground-based observations
The <1974 Nobel Prize in Physics> was awarded for pioneering <radio astronomy> from the late 40s onwards done at the <University of Cambridge> which was an epicenter of early research in that area, leading to the creation of the <Mullard Radio Astronomy Observatory> in 1958.

= Radio telescope
{parent=Radio astronomy}
{wiki}

= Mullard Radio Astronomy Observatory
{c}
{parent=Radio telescope}
{title2=1958}
{wiki}

\Video[https://www.youtube.com/watch?v=NgbKUZEABO8]
{title=New Radio Telescope For Cambridge University (1963) by <British Pathé>}

\Video[https://www.youtube.com/watch?v=5Yiv1-vBSdg]
{title=Space Age Latin Lesson (1968) by <British Pathé>}

= Telescope
{parent=Astronomy}
{wiki}

= Amateur telescope
{parent=Telescope}
{tag=Amateur astronomy}

= Amateur telescope vendor
{parent=Amateur telescope}

= Celestron
{c}
{parent=Amateur telescope vendor}
{wiki}

https://www.celestron.com/

= Celestron NexStar
{c}
{parent=Celestron}

\Video[https://www.youtube.com/watch?v=QDXyBIRooRA]
{title=Celestron NexStar SE Tutorial by Astronomia UK (2022)}
{description=Meh! ;-)}

= Celestron NexStar 4SE
{c}
{parent=Celestron NexStar}

Alignment is impossible to get right! Tried 3 star, 2 named stars, and neither worked well.

* https://www.reddit.com/r/Astronomy/comments/20bot0/what_can_i_expect_to_see_with_a_celestron_4se/

= Universe
{parent=Astronomy}
{wiki}

= Virgo Supercluster
{parent=Universe}

Composed mostly of the <Virgo cluster> and the <Local group>.

= Virgo cluster
{c}
{parent=Virgo Supercluster}
{wiki}

= Galaxy in the Virgo cluster
{parent=Virgo cluster}

Some major ones:
* <Messier 49>
* <Messier 86>
* <Messier 87>
https://noirlab.edu/public/images/noao-m49/?nocache=true also lists: M58, M59, M60, M61, M84, M85, M86, M87, M88, M89, M90, M91, M98, M99, and M100 so lots of large and easily observable galaxies in the area.

= Messier 49
{c}
{parent=Galaxy in the Virgo cluster}
{tag=Messier object}
{title2=M49}
{title2=56 Mly}
{title2=8.4 m}
{wiki}

= Messier 86
{c}
{parent=Galaxy in the Virgo cluster}
{tag=Messier object}
{title2=M86}
{title2=52 Mly}
{title2=8.9 m}
{wiki}

= Messier 87
{c}
{parent=Galaxy in the Virgo cluster}
{tag=Messier object}
{title2=M87}
{title2=53 Mly}
{title2=8.6 m}
{wiki}

= Local group
{c}
{parent=Virgo Supercluster}
{wiki}

The basically composed of only the <Andromeda Galaxy> and the <Milky Way>. Every other galaxy is a satellite of those two.

\Image[https://upload.wikimedia.org/wikipedia/commons/1/1c/Local_Group_and_nearest_galaxies.jpg]

= Galaxy in the Local Group
{parent=Local group}

= Andromeda Galaxy
{c}
{parent=Galaxy in the Local Group}
{tag=Messier object}
{title2=2.5 Mly}
{title2=3.44 m}
{wiki}

= Messier 31
{c}
{synonym}
{title2}

First proper <galaxies nearest the Milky Way>[nearest galaxy to the Milky Way]. Everything in the middle in the <Local group> is either a satellite of the Milky Way or Andromeda.

Many Andromeda satellite galaxies are simply numbered Andromeda II, Andromeda III and so on.

As described on Wikipedia, the observational history of Andromeda is fascinating. Little by little, people noticed that it had a different nature to many other objects observed on the sky, and the hypothesis that there are other galaxies like ours grew in force.

Part of our fascination with Andromeda is due to how similar in size and shape and close it is to the Milky Way.

It is clearly the only thing so large and so close.

Andromeda is, without a doubt, our sister galaxy.

One can't help but wonder if there is some <alien> looking back at us when we are looking at them through our <telescope>.

Andromeda is also the furthest object from <Earth> that can be seen with the naked eye.https://www.relativelyinteresting.com/10-astronomical-targets-new-telescope/{ref} Not surprising, as it literally shines with the strength of a trillion suns!

\Image[https://web.archive.org/web/20220713191240im_/https://cdn.spacetelescope.org/archives/images/thumb700x/heic1502a.jpg]
{title=Highest resolution image of Andromeda as of 2015, taken by Hubble}
{description=Source also says it was the highest resolution image every released by the Hubble. This goes to show how fascinated people are by Andromeda. And there is good reason for it.}
{source=https://esahubble.org/images/heic1502a/}

\Video[https://www.youtube.com/watch?v=3mWSp3YnuLI]
{title=Andromeda Shun from <Saint Seiya> performing his Nebula Chain attack}
{description=The original <Japanese (language)> music actually says "Nebula Chain" in English. The <Andromeda Galaxy> is shown on the back, the chain appears to go all the way to it and back towards the evil guys' head. Not very <relativistic>, but so be it.}

\Video[https://youtu.be/pXcRKoxTPVg?t=973]
{title=<Andromeda Galaxy> with only a Camera, Lens, & Tripod by Nebula Photos (2020)}
{description=Good job! Gives a good idea of the low end approach.}

= Milky Way
{c}
{parent=Local group}
{title2=185 x 2 kly}
{wiki}

\Image[https://web.archive.org/web/20201010121906im_/http://upload.wikimedia.org/wikipedia/commons/thumb/1/1d/Milky_Way_Arms.svg/614px-Milky_Way_Arms.svg.png]
{title=Arms of the <Milky Way>}
{source=https://en.wikipedia.org/wiki/File:Milky_Way_Arms.svg}

= Galaxies nearest the Milky Way
{parent=Milky Way}
{wiki=List_of_nearest_galaxies}

The first proper galaxy near the <Milky Way> is the <Andromeda Galaxy>. Everything else in the middle is a satellite of either of of those.

= Milky Way satellite galaxy
{c}
{parent=Milky Way}

= Large Magellanic Cloud
{c}
{parent=Milky Way satellite galaxy}
{title2=14 kly}
{title2=0.9 m}
{wiki}

One of the <brightest natural objects in the sky>, and by far the brightest not in the <Milky Way>! This is partly because it is relatively close to us.

= Sagittarius A
{c}
{parent=Milky Way}
{wiki}

= Sagittarius A*
{id=sagittarius-a-star}
{c}
{parent=Sagittarius A}
{tag=Black hole}
{title2=Black hole in center of Milky Way}
{title2=27 kly}
{wiki}

= Zone of Avoidance
{parent=Milky Way}
{title2=ZOA}
{wiki=List_of_nearest_galaxies}

= Arm of the Milky Way
{c}
{parent=Milky Way}
{wiki}

= Orion Arm
{c}
{parent=Arm of the Milky Way}
{title2=3500 x 10000 ly}
{wiki}

= Alpha Centauri
{c}
{parent=Orion Arm}
{tag=Star system}
{title2=0.01 m}
{wiki}

= Proxima Centauri
{c}
{parent=Alpha Centauri}
{tag=Stars nearest to the Sun}
{title2=4 ly}
{title2=11 m}
{wiki}

= Nearest star to the Sun
{synonym}
{title2}

It is so close that we can notice its <proper motion>, and its distance to us will vary significantly across a few tens of thousands of years!

= Sirius
{c}
{parent=Orion Arm}
{tag=Star system}
{title2=9 ly}
{title2=-1.5 m}
{wiki}

This is quite close! But as mentioned at: <stars nearest to the Sun>, there are several others nearby. Notably <Sirius> at 9 <ly>, the brightest star in the sky as of 2020.

= Solar System
{c}
{parent=Orion Arm}
{wiki}

= Model of the solar system
{parent=Solar System}
{wiki}

= Geocentric model
{parent=Model of the solar system}
{wiki}

= Copernican heliocentrism
{c}
{parent=Model of the solar system}
{wiki}

= Sun
{c}
{parent=Solar System}
{tag=Star}
{wiki}

= Stars nearest to the Sun
{parent=Sun}

\Image[https://upload.wikimedia.org/wikipedia/commons/5/53/Nearest_stars_rotating_red-green.gif]

\Image[https://upload.wikimedia.org/wikipedia/commons/e/e9/Near-stars-past-future-en.svg]
{title=Distance of <stars nearest to the Sun> as function of time}

https://upload.wikimedia.org/wikipedia/commons/e/e9/Near-stars-past-future-en.svg

Some notable ones:
* <Proxima Centauri>, the nearest one, at 4 <ly>. It is part of the <Alpha Centauri> <star system>, which contains two other stars at very similar distances as well, and their relative distances to earth will change positions in a few tens of thousands of years.
* <Sirius>, the brightest star in the sky at 9 <ly>

= Planet in the Solar System
{parent=Solar System}
{wiki}

= Mercury
{disambiguate=planet}
{c}
{parent=Planet in the Solar System}
{wiki}

= Venus
{c}
{parent=Planet in the Solar System}
{wiki}

= Earth
{c}
{parent=Planet in the Solar System}
{wiki}

= Atmosphere of Earth
{parent=Earth}
{wiki}

= Earth's atmosphere
{synonym}

\Include[continent]{parent=earth}

= Moon
{c}
{parent=Earth}
{wiki}

= The Moon
{c}
{synonym}

= Giant-impact hypothesis
{parent=Moon}
{wiki}

= Earth science
{c}
{parent=Earth}
{wiki}

= Geologic time scale
{c}
{parent=Earth science}
{wiki}

Good list: https://en.wikipedia.org/wiki/Geologic_time_scale#Terminology

= Age of Earth
{parent=Geologic time scale}
{title2=4.5 Bya}
{wiki}

= Extinction event
{parent=Geologic time scale}
{wiki}

= Cretaceous-Paleogene extinction event
{c}
{parent=Extinction event}
{title2=66 Mya}
{title2=Chicxulub crater meteor}
{wiki=Cretaceous–Paleogene extinction event}

= K-Pg extinction event
{c}
{synonym}
{title2}

= Permian-Triassic extinction event
{c}
{parent=Extinction event}
{title2=252 Mya}
{title2=Siberian Traps volcanoes}
{wiki=Permian–Triassic extinction event}

= P-T extinction event
{c}
{synonym}
{title2}

As usual, blame the <Russians>.

= Great Oxidation Event
{c}
{parent=Extinction event}
{title2=2.5 Bya}
{wiki}

<archean>/<proterozoic> barrier.

= Geologic time scale hierarchy
{parent=Geologic time scale}

= Eon
{parent=Geologic time scale hierarchy}
{wiki}

= Phanerozoic
{parent=Eon}
{title2=541 Mya-today}
{title2=visible life}
{wiki}

The term "visible life" refers to multicellular from before people knew there was life in the <proterozoic>.

= Cenozoic
{parent=Phanerozoic}
{tag=Era}
{title2=65 Bya - today}
{title2=new life}
{title2=K-Pg Extinction - today}
{wiki}

= Paleolithic
{c}
{parent=Cenozoic}
{title2=3.3 Mya - 12 kya}
{title2=tools}
{wiki}

This period is similar to the <Quaternary>, but it also includes tool usage by close relatives of <humans> which were not humans yet.

It ends together with the <pleistocene>.

= Quaternary
{c}
{parent=Cenozoic}
{title2=2.5 Mya - today}
{title2=humans}
{wiki}

= Holocene
{parent=Quaternary}
{title2=12 kya - agriculture - today}
{wiki}

= Pleistocene
{parent=Quaternary}
{title2=2.5 Mya - 12 kya}
{title2=humans emerge - agriculture}
{wiki}

Agriculture is not the official definition of the age. But it is good enough. Likely related to the official end of glaciations thing.

= Mesozoic
{parent=Phanerozoic}
{tag=Era}
{title2=252 Bya - 65 Mya}
{title2=middle life}
{title2=P-T Extinction to K-Pg Extinction}
{title2=dinosaurs}
{wiki}

= Paleozoic
{parent=Phanerozoic}
{tag=Era}
{title2=541 Mya - 252 Mya}
{title2=old life}
{title2=Cambrian explosion to P-T Extinction}
{wiki}

End: <Permian-Triassic extinction event>.

= Proterozoic
{parent=Eon}
{title2=2.5 Bya - 541 Mya}
{title2=old life}
{title2=oxygen to Cambrian explosion}
{wiki}

= Archean
{parent=Eon}
{title2=4-2.5 Bya}
{title2=ancient life}
{wiki}

= Hadean
{parent=Eon}
{title2=4.5-4 Bya}
{title2=Hell}
{title2=no life}
{wiki}

No life, earth too hot, until formation of water.

= Era
{parent=Geologic time scale hierarchy}
{wiki}

= Period
{disambiguate=geology}
{parent=Geologic time scale hierarchy}
{wiki}

= Atmospheric science
{parent=Earth science}
{wiki}

= Climatology
{parent=Atmospheric science}
{wiki}

= Climate change
{parent=Climatology}
{wiki}

= Global warming
{parent=Climate change}

= Meteorology
{parent=Atmospheric science}
{wiki}

= Rain
{parent=Meteorology}
{wiki}

= Earth's magnetic field
{parent=Earth science}
{wiki}

= Geology
{parent=Earth science}
{wiki}

= Mineralogy
{parent=Earth science}
{wiki}

= Mineral
{parent=Mineralogy}
{wiki}

= Rock
{disambiguate=geology}
{parent=Mineral}
{wiki}

= Rock
{synonym}

= Sedimentary rock
{parent=Rock (geology)}
{wiki}

= List of rocks
{parent=Rock (geology)}

= Limestone
{parent=List of rocks}
{tag=Sedimentary rock}
{wiki}

Made up mostly of <calcium carbonate>.

= Mine
{parent=Mineralogy}
{wiki}

= Mining
{parent=Mine}
{wiki}

= List of mines
{parent=Mine}
{wiki}

= Jáchymov
{parent=List of mines}
{tag=Czech Republic}
{wiki}

= Joachimsthal
{synonym}
{title2}

"Joachimsthal" is the <German> for it. Note how it is just near the modern frontier between <Germany> and the <Czech Republic>.

It is from <ore> of this mine that <Uranium> and <Radium> were discovered.

https://en.wikipedia.org/w/index.php?title=Uranium&oldid=1243907294#Pre-discovery_use[]:
> In the early 19th century, the world's only known sources of <uranium ore> were these mines.

Apparently the region was a <silver> mining center:
> Starting in the late Middle Ages, <pitchblende> was extracted from the Habsburg silver mines in Joachimsthal, Bohemia (now Jáchymov in the Czech Republic), and was used as a coloring agent in the local glassmaking industry

= Falun mine
{parent=List of mines}
{tag=Sweden}
{wiki}

A hugely important <copper> mine in Sweden.

<Selenium> was initially discovered from ore from this mine.

\Image[https://upload.wikimedia.org/wikipedia/commons/6/66/Stora_st%C3%B6ten_panorama_2010.jpg]

\Image[https://upload.wikimedia.org/wikipedia/commons/d/d2/Falu_gruva.jpg]

\Video[https://www.youtube.com/watch?v=4aOyLYHIiD4]
{title=Mining Area of the Great Copper Mountain in Falun, Sweden by World Heritage Journeys}

\Video[https://www.youtube.com/watch?v=RUmEScYs6cg]
{title=Falun mine tour by Focus by Sohaib}
{description=Not English, but we can see the tour images at least.}

= Ore
{parent=Mineralogy}
{wiki}

= Mars
{c}
{parent=Planet in the Solar System}
{wiki}

= Mars exploration
{c}
{parent=Mars}

= Mars sample-return mission
{c}
{parent=Mars exploration}
{tag=Space exploration}
{wiki}

Not done yet as of 2020! Will be done one day for sure.

= Human mission to Mars
{parent=Mars exploration}
{wiki}

= Jupiter
{c}
{parent=Planet in the Solar System}
{wiki}

= Galilean moons
{c}
{parent=Jupiter}
{title2=1610}
{wiki}

Can you imagine when those guys started to see moons in other planets? They must have <shat bricks>. What better evidence can you have that the <geocentric model> could be wrong?

\Image[https://upload.wikimedia.org/wikipedia/commons/4/4f/Moons_of_solar_system_v7.jpg]
{height=800}

= Saturn
{c}
{parent=Planet in the Solar System}
{title2=antiquity}
{title2=rings 1655}
{wiki}

= Uranus
{c}
{parent=Planet in the Solar System}
{title2=1781}
{wiki}

The first planet not known since antiquity.

= Neptune
{c}
{parent=Planet in the Solar System}
{title2=1846}
{wiki}

Quite cool how it was discoverd by the perturbation of <Uranus>' orbit.

= Dwarf planet in the solar system
{c}
{parent=Planet in the Solar System}

= Pluto
{c}
{parent=Dwarf planet in the solar system}
{title2=1930}
{wiki}