bernulli

6 ms·

1.
by bernulli 4y ago
Maybe ;-) I do know that this course is still offered widely across the US, but maybe not within CS, and maybe not as a mandatory course. But, bottom line: if you're interested, it's very likely you can take it - you may have to c
2.
by bernulli 4y ago
Sounds like a vanilla numerical math course?
3.
by bernulli 4y ago
It really is a tragedy of the commons with a changing demographic, where DINK are more prevalent that, say, 50 years ago, where most tried to contribute to raising the next generation. But the amount of entitlement still baffles me - where
4.
by bernulli 4y ago
But you still benefit even from the mere _existence_ of human beings younger than you are (e.g. service, manufacturing, research, medical, etc.). If you think you don't, think about the fraction of people you will interact with in 20 o
5.
by bernulli 4y ago
There's a simple word for people with that attitude: freeloader. It's pretty easy to understand: > I can not image the extra amount of work that get places on people that do not have children... What you're forgetting is t
6.
by bernulli 4y ago
Just a few words from the other side of the table: I have the highest respect for students sitting there who juggle college, family, sometimes job, after having worked for a while already. It’s wonderful to have someone listening because of
7.
by bernulli 4y ago
Nitnitpick: and we know it isn’t and the corrosive propellants will contaminate surfaces: https://apps.dtic.mil/dtic/tr/fulltext/u2/a588174.pdf
8.
by bernulli 4y ago
Absolutely! I’m sure they analyzed for that, but backflow to the opposite direction of the nozzle is quite unintuitive but normal in rarefied flow, with propellant deposition next to the nozzle possible and documented [1]. Just because you
9.
by bernulli 4y ago
Thank you! I don’t think I understand the resolution then, could you explain a bit more? Say, I request data along a 100km line, every 10m. Do I get the same numbers if it’s in the same mesh cell with a sudden change when it’s crossed, or d
10.
by bernulli 4y ago
Hi meteo-jeff, this looks really cool! I have two questions: 1) How does the spatial resolution come into this? Is it constant data all across the 2kmx2km (?) parcel with an abrupt change, or is it interpolated in some way? Can I query the
11.
by bernulli 4y ago
Hi Otras, a few things to wrap this up for me, and thank you for your civil answer to a not so civil comment. 1st: I should have made this a 'yes and' rather than a 'no but' comment. It's a well written article with
12.
by bernulli 4y ago
Not in the countries you refer to, and not in gliders in many European countries. Not 'everywhere' then.
13.
by bernulli 4y ago
That we can calculate the distance to a lightning to great accuracy (my example in the very first sentence) by accounting for a finite speed of sound only and assuming an infinite speed of light? Yeah, I'm pretty serious that we can ne
14.
by bernulli 4y ago
> The noise is always pointing behind the aircraft or any moving object due to lag. I don't know what a pointing noise is. > Light also encodes the direction to an objects past location, even though light is always moving faste
15.
by bernulli 4y ago
You're the one bringing up the finite speed of light that has zero relevance to the problem at hand.
16.
by bernulli 4y ago
Seems to cut either way.
17.
by bernulli 4y ago
The title is "How far behind a plane is its noise?" It's not. It's ahead of the aircraft.
18.
by bernulli 4y ago
> " These statements exhibit a fundamental misunderstanding of the phenomenon. It's not that the sound outpaces the aircraft. It's that light from the aircraft (reflected or transmitted, e.g., by landing / navigationa
19.
by bernulli 4y ago
It's just completely unrelated to why the aircraft passes you before you hear it.
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by bernulli 4y ago
Thank you.
21.
by bernulli 4y ago
For all practical purposes it's really completely unrelated to the speed of light. Nothing would change in the argument if light travelled instantaneously. Sure, the numbers would change by O(1e-6s), but I'll admit that I wouldn&#
22.
by bernulli 4y ago
Because an aircraft does not make a sudden noise? At least where I'm from aircraft don't sound like discrete booms. I'm not sure I understand your question. > But when the aircraft is closer to you, the attenuation is lowe
23.
by bernulli 4y ago
> "Of course you hear the siren or crazy man or anything, before it passes you if the component of the velocity vector pointing to you is slower than the speed of sound." So, only in aircraft it is different? Magical aircraft p
24.
by bernulli 4y ago
Thanks for chiming in! My point is that your one instant in time is completely arbitrary. You do not know where the position is, and you do not know when the sound was emanated . I.e., you cannot calculate anything. Your math would wor
25.
by bernulli 4y ago
Well yeah, if the plane is faster than its sound (and flying towards you), the plane will reach you earlier than the sound does. The plane does not get attenuated by flying farther, and your seeing threshold is helped by the sun or the ligh
26.
by bernulli 4y ago
Air properties are actually super relevant, the speed of sound distribution (slower with increasing altitude) can have lensing effects for sonic booms.
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by bernulli 4y ago
Sorry, I thought the first answer was so short it seemed rude, which is not what I intended.
28.
by bernulli 4y ago
Haha, yes, you found the one case (which is unrelated to the article) in which sound weakening is not a function of time, as the distance to you stays constant.
29.
by bernulli 4y ago
> "Even if the sound travelled faster than sound [sic] you would still see the airplane passing over you before the sound emitted from the airplane when it passed over you reaches you." Absolutely not. It depends on the Mach
30.
by bernulli 4y ago
> "Why does it have to be a sudden sound? The effect the article describes is the same as eg thunder" Well yeah, that's a sudden sound . My point precisely. So why don't you hear from your observation point the airpl

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