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xkcd.com: A webcomic of romance and math humor.

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Earth Sized Planets

It probably has an icy mantle over the real silicate geology, but I'm hoping something weird happened to burn off most of the water like with Io.

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Gravitational Square Wave

Depending on the energy deposition I can manage, it might also be a fun prank on the rest of the Earth.

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Siege Engine

They initially thought the containment structure alone would be sufficient, but for good measure they decided to include the Elephant's Foot inside.

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Forms of Water

The 'light' refers to bremsstrahlung.

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Vulnerability

Other numbers are largely unaffected, but anyone using '4' for their certificate key is urged to upgrade to '5'.

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Fusion Device

I don't see why people have trouble doing this at room temperature. Using hot rivets would honestly have been MORE work.

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Momentum Demonstration

"I'm doing really well on the Hertzsprung-Russell academic diagram, which has spectral class on one axis and Rate My Professors rating on the other."

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Planet Database

Atmospheric transmission spectroscopy has revealed that the sunsets from the observatory are really pretty.

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Rejected Space Mission Profiles

Although NASA agreed that Voyager 2 'seemed lonely' they decided against launching a companion orbiter mission after further measurements indicated that the spacecraft actually preferred the peace and quiet.

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Dogcatcher

People out here catching strays out here catching strays

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Juice

I need to push some updates to the remote sensing instruments, which are there to measure the surface and definitely not do anything else.

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Spectrum Allocation

Rumor has it that they're finally auctioning off the zeppelin navigation bands, but everyone is worried that the scary boat captains will express interest.

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Accelerator Energies

Fans at Daytona always get extra excited when officials decide to introduce some antimatter cars circling the track in the opposite direction.

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Ground Effect

Runners looking for aerodynamic advantage typically wear sneakers because some fancy dress shoes can create wingtip vortices.

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Jupiter Icy Moons Explorer

"I did briefly visit Venus in August 2025, but I figured out the mistake on my own because it didn't have any moons."

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Slab Graveyard

It's ok if you want to close close your eyes for the slab graveyard, so you can still have fun riding the mantle plume back up afterward!

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Voyager Instruments

Convincing him to turn off the stupid laser show and useless sound system was such a huge ordeal that no one has wanted to do it again.

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Stargazing 5

The sun and the moon appear the same size in the sky, even though in real life the sun is more than twice as big. Some call this lucky alignment coincidence; others say it's proof that sometimes things can be the same size.

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Tyrannosaurus

Many of the smaller dinosaurs seem to have largely preyed on housecats.

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Summer

You should probably get back to shore before spring hits.

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Aerospace Flowchart

Someday, we will find the problem that goes with this solution.

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OH Scale

To access distant parts of the project, I ended up building a regular-scale passenger train inside each rail.

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Fault Taunting

One of the first things they teach you is to NEVER play with the geology toy over a mantle hotspot.

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Semaphore

The speed of light in air is 50% faster than in fiber, but it's a challenge to get the arms to move fast enough to realize the latency advantage.

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Asteroid Mission

Lander, this is Houston. There's been a request that you turn clipping back on and instead set the mass to 1kg. The theorists believe that will be pretty funny.

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Handedness

A 'left-handed specialist' is a physicist who studies the weak interaction.

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Geology Class

The rise of AI review bombing tools threatens to take away a crucial source of experience for geology undergraduates.

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Launchpad

It does come at the cost of some launchpad expansions and increased fuel requirements, but that all comes out of the facility's budget.

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Trade

"You legs may have a comparative advantage at running, but we arms have a competitive advantage at swinging hammers, so unless you accept that we're the dominant limbs and stop hogging the oxygen, that running advantage won't be around for long."

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Highway Signs

Highway engineers like Planck units because, like the speed of light, the energy capacity of a typical car's gas tank is 1.