Yeah, anything that was on another plane was scrubbed long ago

If you've ever saw a professional make pizza bases by throwing them in the air, spinning, it's more or less like that.

More specifically, gravity is attractive in all directions. When the gas cloud the solar system firmed out of started spinning along a specific axis (because of how it was contracting), there was an outward force (the centrifugal force) counteracting gravity in one plane, but nothing perpendicular to that plane. So all the matter started falling into the centre, except where it couldn't, because the centrifugal force kept it in orbit around the forming sun. Repeat the process on smaller scale for planets, and that's why most of them rotate the same way too.

By parallel, I assume you mean on the same plane. You are kind of right, on diagrams they are exactly on the same plane because well you are looking at a 2D representation. In reality, they are not exactly on the same plane. That said, there are pretty close to it, compared to the Sun's equator, Mercury is only at 3 degrees of inclination, same with Venus, the Earth is at 7 degrees, Mars and Saturn at 5, Jupiter, Uranus and Neptune at 6. So they are all pretty close to be perfectly on the same plane. Why?

Well first of all the solar system started as a big cloud of particles. All of them were moving around in random direction. You know a figure skating spins? Well it show phenomenon, if you spin and you bring back your limb toward the center of your body, you will spin faster. Same thing happened to the solar system. As gravity brought the cloud of particle together, it started to spin faster.

Particles started to hit each other, which created a favored direction of spin. Aka most stuff was spinning in one direction, so everything else go bumped into, leaving just one main direction of spinning. You can see that happening in this demonstration video at around 2:30min.

Now you have a ball of particle spinning in one direction. The second analogy I will use is when you are spinning a pizza dough. I won't go into the physics detail of why this is happening, but basically the fact that the dough is spinning will stretch it around the axis of rotation. Same happened with the cloud of particles that was our early solar system. It stretch around the axis of rotation, bringing all the particles into roughly the same plane where all the particles eventually came together with gravity into the different planets.

I assume by "parallel" you mean like their orbits are all on the same plane. This is no accident or coincidence, it is a result of how they formed. The solar system and the sun itself formed from the collapse of a giant cloud of dust and gas, and that cloud had some amount of rotational momentum. Such momentum is conserved and like how a spinning skater will speed up as their mass is pulled in closer, the bits of the massive cloud of dust collected into planets and formed sustained orbits. Those orbits will all be on the same plane because that is the net result of the conserved momentum.

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They all orbit the sun in the same plane because the sun and the planets all formed from the same gas cloud. That gas cloud that they formed from had a particular angular momentum associated with it (i.e. on average, all the particles were spinning around in a particular direction). When the gas cloud collapsed to form the solar system, the sun and all the planets ended up spinning in that same direction because angular momentum is always conserved.

I remember reading that it didn't start out that way, but all of the collisions between orbiting bodies eventually caused a net rotation where there are fewer collisions and the whole system is the most stable.

They orbit around the same thing, the Sun, but don't fly parallel. They all have the same orbit central point, however.

Diagrams use this as a way to line them all up at one fictional point in time, for the sake of showing at-a-glance measurements between planets, to a certain scale.

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I'm annoyed that you didn't say "3-6-2-5-1"

It's never the notes that you're playing that sounds good, it's the notes you ain't.

This is a great answer!

To take it a bit further, “Do” is a single note as you said. “Do Re Mi Fa So La Si Do” refers to the difference between the notes (eg jump two, jump two, jump one). And that pattern of differences is called a key.

You can start anywhere you want though and decide that note is “Do”. If you start on C and play that pattern, you are in the key of C. If you start on a D and play the same pattern, you are in the key of D.

One thing I will add is that even songs that use the same notes can sound very different based on where the song starts.

C Major and A Minor use the same notes, yet sound very different. To illustrate:

1. My Girl - The Temptations, is in C Major.
2. Midna's Lament - Twilight Princess, is in A Minor

My Girl sounds happy, while Midna's Lament sounds melancholy.

I'm late to the game but bringing my band geek knowledge to try and ELI5.

The white and black things you press on a piano are called keys, but that's not what it means when we talk about the KEY of a song. If you made a song using all of the strings on a guitar or all of the keys on a keyboard together randomly, it would not sound like MUSIC, it would just be noise.

If you make up a song and sing it to yourself, you could then go over to a piano and pick out what the notes are, and write them down. There will be a KEY that is most natural for that collection of notes. For instance, if the notes you wrote include a lot of B flats and E flats, your song's natural KEY is the B Flat Major Scale, which goes B flat, C, D, E flat, F, G, A, B flat. (When you are learning any instrument including voice, you will learn all the major and minor scales.)

So a song is just a series of notes with a set relationship between them. You could transpose the song you just wrote (change the notes, keep the relationship between notes the same) into any KEY, although it might change the mood of the song. Changing the key is useful for singers if the song in its original key has some high or low notes they can't hit. But if you want to play music with more than one person/instrument, you all need to be playing in the same KEY.

There are a lot more notes than c d e f g a b, they all have sharps (bit higher) and flats (bit lower)

When a song is in a key, we mean that it has a specific note as its base, and the other notes follow that notes scale.

A scale is a sequence of note distances, so no matter what note you play, the next note in a scale will always be the same distance. Think of it as a staircase that has a sound for each of its steps and when climbed up it always follows the same sound pattern.

A C major scale is played with all of the white tiles of the piano, from C to the next C. A song in C major will use those notes. Another scale, like G major, will need to use one black tile in order to keep the same pattern.

Basically, a scale is a pattern of sounds, and the key is just which note is being used as the first note in the pattern.

>How can songs be in a certain key?

In western music we have 12 notes in total: Do, Do# (Re♭), Re, Re#(Mi♭), Mi, Fa, Fa#(Sol♭), Sol, Sol#(La♭), La, La#(Si♭), Si

A key is basically a predefined set of these notes that we have to play on so we can stay in that key. The more music theory you know the better you'll be able to break this rule and even change keys at the middle of a song.

>How are there like keys and majors and like C minor chords and whatnot?

Keys are not just made up randomly, they follow certain patterns such as how many tones or semitones are between each note. This pattern will decide if it is a major or minor key.

We already established that a key is just a set of notes from the full spectrum of notes available. A chord is basically the same thing on a smaller scale, they are a set of notes you take from the key you are playing on. Same as in a key, how many tones and semitones divide the notes from your chord will also determine if it is major or minor chord.

>Does that just mean the voice sounds like a music note?

Yes. For example, a human voice and a piano may both emit the same note (same frequency), but you can distinguish them because they both have different timbres.

>Are songs not just "buttons" pressed in a certain order with certain delays (and pedals and whatnot)?

If we are oversimplifying it, yes. However, if we want our song to sound good then we need to follow certain rules. If you know enough theory it is possible to create a nice simple song on paper before actually hearing it.

Every answer can be elaborated way more than this but I tried to keep it in a ELI5 as much as possible.

I spent six months of private study in my late 30s learning this. My husband assures me that most people have an intuitive understanding of what it means.

Thanks to all those responding to this question.

Keys are the name we call certain groups of the ‘buttons’. If a song uses only or mostly buttons from one of the key groups, then we say it is in that key.

I'm going to take a different approach, starting with chords, and moving to key.

You're right, chords are multiple notes heard at the same time. The study of how those notes interact is called Harmony. Chords can be simple, or really complex. But they generally we can separate them into two types: notes that sound good together are called consonant, and notes that sound like they are fighting or are unpleasant together are called dissonant. That's right, the word harmony doesn't mean pleasant, harmonies can be pleasant or unpleasant (consonant or dissonant).

Now, in a piece of music not all chords are equal. In the vast majority of the music you are exposed to is called "Tonal" music. This means that there is a note or chord which feels like home. Music is like writing a story; if there isn't a final ending to the story, it just feels wrong. As you said, you are aware of do re mi fa sol la ti do. That's a great example. If you were to sing or play those notes, and stop on ti, it can be painfully incomplete. I like to demonstrate this in class. I'll play those notes and stop before the final Do, and the whole class squirms, or tells me "Finish it!" I've even had students run up to the piano and play it themself.

You can think it like grammar and punctuation. Sentences can end in a question mark, or a period. One feels incomplete, the other feels complete. In tonal music, there are all sorts of ways to point to the chord or note which is "home." It's all about tension and resolution. It's a lot like writing a book. You introduce your main character (establish the key), go on some adventures (different chords, chords with tension), and finally conclude the story (returning to the home key).

Take note: this is a description of tonal, western music. India for instance, has a long history of its own classical music, that uses different expectations and tools.

Doesn’t work, because then you’d have a father and a son who share the same first name but have different last names.

Seen these first handful of comments and ain't a lot of ELI5ing here yet, so here goes.

Here is a random number pattern example: There is no real difference between me saying 1-3-5-6 and me saying 2-4-6-7 (both start with a number, jump two, jump two, and then jump one)

The gaps between both sequences are the same. I'm counting the same sequence of gaps, regardless of whatever number I start with. That's what keys are.

Also, yes chords are groups of "numbers" we'll call them still, but now we are saying all at once instead of in a sequence. If "1-3-5" sounds good played at once, then "2-4-6" will too. The distances between the numbers are what's important, not the numbers themselves.

Imagine starting the count at 1 is A, starting at 2 is B etc etc.

Helps that the list of common Japanese names is fairly short.

Then when you learn Japanese and realize it's mostly mixing and matching a few common things like season, weather, common descriptive adjectives, and child/girl/boy at end, it becomes really easy to recognize.

What if the second Kim is a junior?

I think because he (Yuki) reversed his name so it was in the western fashion, as other Japanese drivers have in the past.

This may be less to do with F1 being familiar with Japan, and more to do with Japan being familiar with F1 and other western influences