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Earth Formation Site

Title text: It's not far from the sign marking the exact latitude and longitude of the Earth's core.

Explanation

This explanation may be incomplete or incorrect: Created by TWO 4,450,002,024-YEAR-OLD PRESIDENTIAL CANDIDATES - Please this edit this comment when editing this page. Do NOT delete this historical tag too soon.

In this comic, Cueball stands in front of a sign that declares itself to be an historical location, the formation of the Earth. The humor of the comic is twofold:

1. the amusing illogic of the assertion
2. the impossibly precise date

#1: The amusing illogic of the assertion

First, the Earth formed at its center, not its surface, so an “Earth formed here” sign on its surface is factually incorrect.

One may argue that technically the sign is above the right spot, just as every location on Earth is above the right spot. However, the sign refers to “this location,” not to a spot underground.

If an omniscient observer wanted to mark the spot in space where the Earth started forming, an historical marker on the surface of the Earth wouldn’t suffice. That’s due to the Sun's 225-million year long orbit around the center of the Milky Way galaxy and the movement of the galaxy itself through space relative to other objects. From this galactic perspective, the Earth’s formation did not occur anywhere on or inside Earth.

#2: The impossibly precise date

Secondly, specifying a single year of formation BCE (Before the Common Era) is an amusingly precise choice. It takes tens or hundreds of millions of years for a planet to form. Picking a year would require some specific definition of when a gradually-coalescing mass of proto-planet dust and gas could be considered a planet, as well as the ability to determine when that mass met the definition.

Note: The date shown for the formation of the Earth, 4.45 billion years ago, also differs from the commonly accepted date, 4.54 (±0.05) billion years. The difference lies in the transposition of two digits, potentially a mistake.

Satire of historical markers

This comic satirizes US historical markers by channeling their standard tone, structure, and inaccuracies. Typically, these signs are placed at precise locations where historical, religious, and even mythological events are believed to have happened — such as where battles have been fought, or where famous people resided or accomplished something.

Title Text

The title text refers to the 'exact latitude and longitude of the Earth's core,’ Of course, since the lat-long geographic coordinate system is used for locating places on the surface on the Earth, the center of the Earth does not have latitude and longitude.

Also, a historical marker referring to the earth’s core could be placed anywhere, and its specific location in the real world wouldn’t mean anything; as above, every spot on Earth is above the right spot.

Examples of similar historical marker signs:

• Kenya Equator latitude
• Arctic Circle latitude
• Prime Meridian longitudes
• Highest Point
• Lowest Point

Analysis and trivia

The comic and its title text are actually inverse jokes of each other: The historical marker in the comic assigns an attribute of the Earth’s center (the site of formation) to a spot on its surface, while the title text assigns an attribute of surface locations (latitude and longitude) to the Earth’s center.

The topic of what precisely makes a planet — related to the 2006 redefinition of a planet and the subsequent demotion of Pluto from the ninth planet from to the sun to a dwarf planet — has been covered before in 473: Still Raw and referenced in other XKCD comics.

Transcript

This transcript is incomplete. Please help editing it! Thanks.

[Cueball is standing in front of a sign in a field of grass. Rocks and plants are scattered across the ground. The sign reads:]

HISTORICAL MARKER

EARTH

FORMATION SITE

--- 4,450,000,000 BCE ---

At this location in the year 4,450,000,000 BCE, a cloud of dust and gas gravitationally collapsed to form the Earth.

Is this out of date? Clicking here will fix that.

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