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xkcd #3093: Drafting

Title text:

A 5% efficiency gain at the cost of a 99% efficiency loss

Transcript:

[A rocket with two boosters is launching going towards the top right corner. It has a two-stage core and two boosters, and they produce three flames from their exhaust and beneath these flames is a large exhaust plume fanning out behind the rocket most of the way towards the bottom of the panel. A smaller rocket is following the first rocket. It is very close to the first rocket, so most of the smaller rocket is inside the exhaust plume from the larger rocket. The smaller rocket does not have boosters, but still produces three smaller flames from its exhaust. Beneath these flames the smaller rocket also leaves a large but slimmer exhaust plume that exits the panel at the bottom left corner.]

[Caption below the panel:]
Aerospace tip: Although the technique reduces atmospheric drag for many types of vehicles, you should never try to improve rocket launch efficiency through drafting.

Source: https://xkcd.com/3093/

explainxkcd for #3093

xkcd #3092: Baker's Units

Title text:

169 is a baker's gross.

Transcript:

Transcript will show once it’s been added to explainxkcd.com

Source: https://xkcd.com/3092/

explainxkcd for #3092

Title text:

Applying renormalization to bullies successfully transformed Pete & Pete's Endless Mike into Finite Mike.

Transcript:

Cueball poking an atom. Megan looks at it with a hand on her chin]
Cueball: Hey, electron!
Cueball: Stop hitting yourself!
Cueball: Stop hitting yourself!
Megan: ...Wait.

[Caption below the panel:]
Renormalization actually started out as an effort to bully electrons.

Source: https://xkcd.com/3091/

explainxkcd for #3091

Title text:

Turning in other directions can be accomplished by using a magnetized centerboard and ocean currents, since a current flowing through a magnetic field induces a Laplace force.

Transcript:

[Four panels show a schematic sail boat, seen from above, to indicate how it can sail into the wind. In the first panel the boat is heading straight up in the panel. The sail is fixed at the bow and describes a slight curve going to the right of the boat and then curving to the left, ending close to the stern. The rudder can be seen behind the boat. Five arrows, pointing towards 4:30 on a clock face, are drawn at the top left part of the boat, indicating the direction of the wind. There is a frame above the drawing of the boat with text. And then the arrows are labeled, and small lines going to the sail and the hull of the boat connects with two more labels:]
How sailboats use physics to sail upwind:
Wind
Boat
Sail

[In the second panel the boat is drawn similar to panel 1, but the wind arrow have been changed to showing how the wind now blows past the sail on either side. This is done with two lines of three arrows that goes on either side of the sail, and the second and third arrow bends to follow the curve of the sail. Charged ions are shown across both sides of the sail with positive on the left side of the sail, (over the hull of the boat) and negative on the right side, over the sea to the right and behind the boat. The positive charges are small + signs in circles and the negative minus signs in circles. Above the drawing there is the following text:]
1. Wind passing over the sail strips away electrons via the triboelectric effect.

[In the third panel the boat has turned towards right and has been moved closer to the bottom of the panel (this could be to acomodate more text above though). The entire hull is now covered in positive charges. A large broad dashed vector is shown going in the direction of the wind. The arrow is not over the boat but on either side of it, with the arrow head ending right of the stern of the boat. Two thin arrows are shown above the end of the force vector. A short solid arrow, that points along the same direction as the large arrow. And then a dashed arrow is drawn perpendicular to the first of these thin arrows (pointing along 1:30 on a clock face. Above the drawing there is the following text:]
2. The positively charged boat is blown downwind; its movement in Earth's magnetic field produces a Lorentz force.

[In the fourth panel the boat has turned even more towards right and is back to the same height in the panel as the first two panels. The entire hull is still covered in positive charges. The broad dashed vector is still shown, but after starting in the wind direction it can be seen to turn slightly upwards before reaching the boat. And then when it comes out the other side of the boat it points in the direction of the bow of the boat, the arrow ending in front and a bit to the right of the boat. The two thin arrows from before are now shown to the left of the boat , with the short solid arrow pointing along the same direction as the start of the large arrow. And then a the dashed arrow drawn perpendicular to the first of these thin arrows pointing in the direction the boat is sailing. Above the drawing there is the following text:]
3. The Lorentz force acts perpendicular to the direction of motion, redirecting the boat upwind.

Source: https://xkcd.com/3090/

explainxkcd for #3090

Title text:

P.S. If you have time travel, come to my birthday party Saturday!

Transcript:

[Cueball approaches Ponytail, chiselling a rock on a shoreline next to a river with shallow rolling hills in the background]
Cueball: What are you doing?
Ponytail: This river empties onto a passive continental margin.

[Cueball and Ponytail stand talking, Ponytail holding several flat rocks, in an otherwise empty and frameless panel]
Ponytail: If I chisel notes onto these rocks and throw them into the sea, they might be incorporated into some shale cliff in the distant future.

[Silhouetted scene of Ponytail as she throws multiple rocks off frame to the right, Cueball watching from behind her]
[From off-panel, sound effect of a rock hitting water:] PLOP

[Two 'bug-eyed aliens', sitting in personal 'hover-saucers' look rightwards at an exposed rock-face. A pick and shovel are left stuck in the ground, and one of the 'saucers' sports a mechanical arm currently holding a loose fragment of rock]
[Panel label:] 100 million years later
[Text originating from the held rock fragment:] This bedrock inspected by No. 5

Source: https://xkcd.com/3088/

explainxkcd for #3088

Title text:

Reductio ad absurdum fails when reality is absurd.

Transcript:

At the left, a teacher is holding a pointer, pointing at a picture on the screen.]

[The picture shows a hydraulic lift, with a small fluid vessel on the left connected to a tube at the bottom, which connects to a large vessel on the right. On top of the large vessel is a weight labeled 1000 and a Cueball. The fluid in the large vessel is labeled with an upward arrow. Megan's hand is over the small vessel, with a downward arrow indicating that she's pressing on it.]

[Cueball, Hairbun, and Blondie are sitting at school desks going right to left.]

Cueball: No, that can't be right.

Cueball: If hydrostatic pressure worked that way, then you could use it to make machines that exert near-infinite force.

Cueball: And ancient people could have demolished entire mountains just by drilling small tunnels and filling them with water.

[Caption below comic:]

When I first learned about Pascal's law, I tried to disprove it by showing that it would lead to absurd consequences, but it turns out hydraulic presses and ruina montium are both real things.

Source: https://xkcd.com/3087/

explainxkcd for #3087

Title text:

Frankly, given their extreme gravitational fields and general instability, even 12-inch globes should probably be banned.

Transcript:

[A standard globe of the Earth is shown. It stands on a typical stand which holds it by two arms at the poles, so it can turn around like the Earth does. The Earth is turned so it shows Australia at the bottom and most of Asia, including the entire India to the left. Only the very tip of Alaska can bee seen of the Americas. Above the globe there is a double arrow that goes to two small lines that align with the edges of the globe (indicating the diameter). The arrow has been split in the middle and two lines of text is written in the gab. Above this text there is another line of text.]
Remember:
4 inches minimum

[Beneath the globe there are two small drawings. The left shows the Earth and to the left of the Earth there is a double arrow ending at two lines that indicated the diameter of the Earth going from top to bottom. The distance of this is written in inches to the left. From the Earth an arrow points to another drawing, this time the typical depiction of a black hole, with the "hat" shape. A warning sign is shown a the top right of the black hole with an exclamation mark inside.]
7/10"

[Caption Below the Panel:] The Earth's Schwarzschild radius is about 0.35 inches, which is why safety regulations require desktop globes to be at least 4 inches in diameter.

Source: https://xkcd.com/3086/

explainxkcd for #3086

Title text:

In addition to gravity, burritos interact through the strong, weak, and electromagnetic forces, which is believed to be a major contributor to their popularity.

Transcript:

[Cueball and Ponytail are standing in front of a pentacle with lit candles at the corners. A black sphere, the oracle, is floating above the middle of the pentacle.]
Ponytail: Dear oracle,
Ponytail: What is the nature of dark matter?
Oracle: It's about 20 pounds.

[Close up of oracle]
Off-panel: What?
Oracle: Dark matter is a particle. It weighs about 20 pounds.
Oracle: It only interacts through gravity.

[Same view as first panel]
Cueball: Only gravity, huh?
Cueball: So none of our experiments are really going to tell us any more about it, then.
Oracle: Afraid not.

[Same view as first and third panels, except Cueball lifted his forearm.]
Cueball: So what do we do?
Oracle: You should go out for burritos.
Ponytail: How will that help?
Oracle: Well
Oracle: Burritos are pretty good.

Source: https://xkcd.com/3085/

explainxkcd for #3085

Title text:

Unstoppable force-carrying particles can't interact with immovable matter by definition.

Transcript:

[An arrow pointing to the right and a trapezoid are labeled as 'Unstoppable Force' and 'Immovable Object' respectively.]
[The arrow is shown as entering the trapezoid from the left and the part of it in said trapezoid is coloured gray.]
[The arrow is shown as leaving the trapezoid to the right and is coloured black.]
[Caption below the panel:] I don't see why people find this scenario to be tricky.

Source: https://xkcd.com/3084/

explainxkcd for #3084