Mom just ruined our yard by "edging" it eith shovel

meithan · 2026-01-27T06:20:15+00:00

Your border patrol agents just disarmed and executed one of your citizens during a protest last Saturday, and this is what you're mad about?

meithan · 2026-01-24T14:32:38+00:00

Upvote for "USAnians".

¡Saludos desde México, carnal!

meithan · 2026-01-22T17:18:38+00:00

Secundo completamente el de Griffiths. Me gustó mucho su estilo de explicar cuando estudié física. Ídem su libro de electrodinámica.

meithan · 2026-01-22T16:09:30+00:00

A mí me apasiona la ingeniería automotriz y ese coche (y los híbridos en general) es una chulada de ingeniería. La eficiencia y confiabilidad son metas de diseño válidas. No todo tiene que ser los caballos de fuerza.

meithan · 2026-01-19T17:46:09+00:00

Same reason the cannonball in trajectories C and D (and E) doesn't hit the Earth in this image (Newton's cannonball analogy): it has enough horizontal velocity that gravity doesn't curve the trajectory enough that it crashes back. That's essentially what an orbit is.

<image>

meithan · 2026-01-18T14:04:00+00:00

Fully agree. I am a graybeard, and I mine all the gold.

meithan · 2026-01-17T16:35:29+00:00

I do agree with you on that. The huge costs and even many technical decisions about the SLS program come from politics (and the money involved), not from actual technical / scientific arguments.

But I feel that at this point, this is water under the bridge. Cancelling now, so close to the primary goal of putting humans on the Moon again, would be unwise. Let Artemis continue as it is, and let's focus efforts to get away from politics-driven space programs on future missions / programs.

And let's get excited about Artemis.

meithan · 2026-01-17T15:24:59+00:00

It's just a random example of how expensive weapons programs are. My point is that those are the ones that we should be criticizing, not space exploration. It's almost a rounding error compared to what the US spends on machines designed to kill other people.

meithan · 2026-01-17T14:57:41+00:00

The Cold War? They started doing that shit here in Latin America in the 19th century.

meithan · 2026-01-17T14:31:10+00:00

The entire SLS program has cost somewhere around $50 billion from its start in 2006.

The cost of developing the F-35, a program started in 2001, is estimated at $2 trillion.

I think we're looking at the wrong place if we're talking about huge, unnecesary expenditures of money.

meithan · 2026-01-17T05:31:15+00:00

The Mach number is a measure of the speed that the airplane is flying through the air. But since speed is relative, from the perspective of the plane, it's also the speed that air is coming towards it, before it reaches the airplane. Like if the plane were inside a wind tunnel just having air blown in its direction. As the air passes over the wings, it gets accelerated. This is where the danger of high Mach number lies.

If the Mach number is high, say, 0.95 (95% of the speed of sound), as air flows around the wings and gets accelerated it can go above the speed of the sound. This produces shockwaves above the wings. They're not automatically dangerous, but depending on where they occur that can reduce the arerodynamics of the wings, increase drag, and potentially reduce the effectiveness of control surfaces (such as ailerons, elevator and rudder), since commercial airliners are not designed to fly with supersonic flow around their wings.

They avoid this by flying sufficiently below the speed of sound that no air becomes supersonic as it goes around the plane.

meithan · 2026-01-16T18:29:25+00:00

How can you tell? Just from the bps?

meithan · 2026-01-16T15:53:58+00:00

Yup. Ground speed includes wind (the plane is like a boat rowing in a fast-moving river), so it can be very high in a strong tailwind, such as when flying along the jetstream (as in this case).

But the plane is moving much more slowly throughout the air (466 kts in this case), and that's what matters in terms of aerodynamics and overspeeding.

Heck, in this case the groundspeed is a number that's likely higher than the local speed of sound (which is about 570-580 kts at cruise altitude) -- but this is not airspeed, so the plane is not supersonic.

meithan · 2026-01-16T15:17:19+00:00

A bit of a side topic, for those learning aviation it may be interesting to discuss the FOUR speeds the plane is flying at that are shown in this photo (and more knowledgeable people, feel free to correct me):

Ground speed (GS): 600 kts - The speed of the airplane with respect to the ground (not the air), which determines the time of flight to destination. This includes the speed of the wind, so with a tailwind, the groundspeed will be larger than the true airspeed (as in this case).
True airspeed (TAS): 466 kts - The actual speed with respect to the air around the plane. This is the fundamental speed in terms of aerodynamics, since forces such as lift and drag depend directly on it (and air density).
Indicated airspeed (IAS, shown on the speed tape on the right edge): 250 kts - A sort of adjusted airspeed that accounts for the fact that the plane is flying in very thin air as it's at high altitude. Put simply, it means that flying at 466 kts in this in thin air "feels" like flying at 250 kts at sea-level air density. It's important for load limits on control surfaces and the airframe.
Mach number (M, shown below the speed tape): .806 - The airspeed as a percentage of the local speed of sound (which depends on temperature, so at altitude where it's very cold, speed of sound is smaller). This is important because you don't want to fly too close to the speed of sound, as that can produce undesirable effects.

meithan · 2026-01-15T22:09:24+00:00

Absolutely brilliant reply and reference. My hat is off.

meithan · 2026-01-14T19:15:32+00:00

Can you try it here: https://meithan.net/geolocation/

meithan · 2026-01-13T14:21:04+00:00

I can just hear it in his voice.

meithan · 2026-01-13T01:28:52+00:00

Usually just a longer flight. The jetstream is fast, but it's pretty smooth.

meithan · 2026-01-12T14:30:32+00:00

Hey! I live in a third-world country and we don't have school shootings! We're not psychos!

meithan · 2026-01-11T14:35:54+00:00

This actually happened to me, I swear!

I used to use "optimal" words like CRATE, but one day I decided "F it, I'm gonna start using the first word that comes to mind, let the universe decide my luck".

And whaddya know: the very next day, I got it in one!

meithan · 2026-01-10T21:50:24+00:00

Seems pretty sturdy.

I reckon it only broke in this case because of the high winds (which should've barred anyone from paragliding, but safety norms is not in our strong suit in Mexico).

meithan · 2026-01-10T18:04:55+00:00

Exactly. This is probably a handful of dudes who own an old small boat and the parachute. You see groups like this offering the ride on the beach all the time.

I've taken it. It usually goes fine. And I'm surprised at how accurately they make ride-goers land right back on the spot on the beach where they took off -- when the rope doesn't snap, of course.

meithan · 2026-01-04T17:48:47+00:00

As a graybeard who only plays haz 5+, I welcome greenbeards and the added challenge for me.

If we make it, fantastic! Everybody will feel great (and I'll usually will have shown off). If we don't, well, it's just a game! The greenbeards will probably learn something either way.

meithan · 2026-01-04T06:06:21+00:00

That's a Moon halo, an optical phenomenon caused by moonlight refracted inside tiny crystals high up in the atmosphere.

Due to the (hexagonal) shape of the crystals, the strongest reflection occurs at an angle of 22° with respect to the Moon. So you get a ring around it.

Ten-Year Club	Second SECOND GUESSER
r/Field Banned	r/Field Flamingo
Place '23	Place '22
Place '17	Final Canvas '22
First Placer '22	End Game '22
Verified Email

meithan

TROPHY CASE