xanthraxoid t1_jaa741k wrote

Another possibility is that they're not "letting you in" to use you "as a body shield" but they're leaving a sensible amount of empty space "as a body shield" and you've just put your car in the middle of a potential collision zone.

LPT: leave a good healthy gap in front of you. Remember that "two second rule"?* Try counting it out some time, it's probably further than you think. 90+% of drivers I see are within a second, and an alarmly non-zero amount significantly closer than that!

And it's really not as patronising as it feels, either. Even if you're focussed on driving (and let's face it, it's very easy to have your attention divided or entirely displaced for short periods while driving) it'll take you about a second to respond to a sudden need to slow, so if you're within a second of the vehicle in front, there's a good chance you'll hit it even in the most favourable of circumstances.

I've had a couple of accidents where I've used up all of my two second gap and more - including one recently. Please take this seriously!

* Oh, and that's for dry roads. Double it for wet, triple it for salted, and multiply it by ten for ice/snow.


xanthraxoid t1_j9xyaxu wrote

I thought it also included usage of the word "[[cunt]]", which is generally considered to be at or near the strongest end of the swearing spectrum, but after trying to verify that, I was probably thinking of The Exorcist!


xanthraxoid t1_j9uyoii wrote

It's worth noting that these tests aren't completely comprehensive. Recall that the nominal shelf life of various Covid vaccines was extended a couple of times - the initial results were interpreted conservatively, but over time more evidence allowed a more confident prediction of a longer shelf life.

When it comes to a vaccine that's not expected to be useful more than ~6 months into the future (nobody's taking the flu jab in the spring, and next year they'll want the new one) there's not really much point in measuring how it lasts beyond that with any degree of rigour.

Providing the shelf life is expected to be good enough for "this year's flu season" (3 months?) they'll most likely just use that figure and move on to more valuable work.


xanthraxoid t1_j9ogqci wrote

My granddad died a few years back, and an uncle a year ago. I've found myself even more keen to spend time with all my relatives, particularly my gran who's in her nineties and losing her memory. Whenever I'm with her, I just bask in her presence, filled with a bittersweet certainty that these times are far more precious than I can know, and are palpably finite...

I'm making sure that I express love and appreciation for everyone in my life, especially family, and especially those who're getting on in years.

Hey, guys. Don't let any family feud or past awkwardness get in the way of this stuff - I promise that 99% of those disagreements are ultimately chaff that isn't worthy to get between you and your family or friends.


xanthraxoid t1_j8hw5p2 wrote

I think I'd take your statement on the fungibility of photons further to say that the "particle" is more illusory than the "wave".

I tend to think of seeing a particle as somewhat analogous to seeing an eddy in a flow of water*. The water (/electromagnetic field) is the "thing" and the eddy (/photon) is just an observable behaviour of that ground truth.

The wave behaviour of particles can matter for electrons, and atoms, and even surprisingly large molecules! As you look at larger and larger things, though, the downsides of treating them as particles become more and more irrelevant. One major reason for this is that the "wavelength" of a wavicle gets shorter in proportion to its momentum going up.

While a photon of visible light has a momentum in the region of 10^-27 Kg.m.s^-1 and a wavelength in the region of 10^-7 metres, Schrödinger's cat moseying along at walking pace has a momentum in the region of 1 Kg.m.s^-1 and a "wavelength" in the region of 10^-34 metres. That's about 1/1,000,000,000,000,000,000,000,000 the size of an atom - a little smaller than the size of the cat, and squirting a stream of cats through a 10^-34 metre slit would probably give you a somewhat messy version of the classic diffraction pattern (sorry, Tiddles!)

(Note, the numbers in that last paragraph are all essentially to zero significant figures and within the limits of my patience of counting zeros, but with those kinds of numbers, even a couple of orders of magnitude really doesn't make any difference :-P)

* A closer analogy would be waves in water, but eddies are easier to visualise as being distinct entities. To be fair, eddies can exhibit some properties (destroying / combining with each other / splitting) that can be entertainingly analogous to colliding subatomic particles, but probably not in ways that help my use of the analogy :-P


xanthraxoid t1_j6pdqy6 wrote

I'm no DARPA-ologist, but I would hypothesise that this spec is for an initial phase to develop / demonstrate the technology, to be potentially followed by a more demanding spec aimed at a potential deployable asset.

Also, bear in mind that by far the majority of aeroplanes don't have to take off from a carrier. While being able to take off from a carrier is definitely a useful feature, being able to take off from a 1500ft runway still opens up a lot of potential places to fly from - old WWII aerodromes, for example. If you have a friendly airport nearby, there's less need to rely on using a carrier (though you'll still have to arrange fuel supply and other support stuff)


xanthraxoid t1_j6okdru wrote

While movable flaps are certainly a factor in providing a radar return, smooth wings aren't the ideal from a radar perspective - hense the distinctive Tesla CyberTruck^TM appearance of the [F117](https://en.wikipedia.org/wiki/Stealth_aircraft#/media/File:F-117_Nighthawk_Front.jpg].

If you have a flat surface, it'll only return radar waves in one direction (which is unlikely to be where the receiver is) whereas a curved surface will scatter it in lots of directions, meaning some is likely to end up going back where it came from to be detected.

The worst case scenario is something that forms a retro-reflector, such as a corner reflector or the radar equivalent of a cat's eye so they're careful to avoid those.

As a thought experiment (or a real one if you feel like it) have a friend hold up a Christmas tree bauble and a similarly sized compact mirror in a dark field. Shine a torch at them, and see which you can see more easily.

The ball will have a sharp spot of reflected light on it, and the mirror will (almost certainly) not reflect back toward you and be seen.

Of course, if you happen to angle the mirror just right, then it'll reflect a whole bunch of light back at you, but of course they don't use mirrors, they use the radar equivalent of VantaBlack so even the reflection you do get is minimised, but the difference between the flat and curved surfaces remains.


xanthraxoid t1_j6nuokq wrote

AFAIK the largest vehicles made with the "UFO" design were of a scale similar to the one in the pictures. IIRC (I did read up on it a while back) the main problem was difficulty with stability and control, so they shelved the plans.

These days, with computer control, reacting to changes in dynamics hundreds of times per second would be perfectly feasible, though, so perhaps those challenges are ready to be taken on.

Some modern aircraft are deliberately designed to be inherently unstable and require constant active control from an onboard computer to remain pointy-end-first. The advantage is that when you do want to change direction, it can be done very quickly indeed. With that and thrust vectoring, you can also make a plane that will function in states where a more traditional design would turn into a billion dollar brick (see Relaxed Stability and Supermanoeuverability)

In terms of scaling it up to larger sizes, I expect they'd scale reasonably to a point, but as you get larger, the sheer volume of air you'd need to huff around starts to be an issue. The density of air doesn't go up as your aircraft size goes up, so it's not just a matter of doing the same thing but bigger.

The article linked to by OP was only talking about using these kinds of techniques for control surfaces, though, not for directly generating lift, so we're only talking about a pretty small fraction of the required oomph compared to the flying saucer.


xanthraxoid t1_j6mhqlg wrote

The figure for what constitutes a "short runway" is given as "1,5000ft" which is obviously a typo. I assume it was supposed to be 1,500 rather than 15,000 as the latter is a ~3 mile runway and probably not what would be considered "short" :-P

The idea of changing airflow around an aerodynamic surface using forced air isn't exactly new. There were experiments with "coanda effect wings" for propulsion as well as control at least as far back as the 1950s.

There are also devices (NOTAR) using the coanda effect as an alternative to the tail rotor on some helicopters.

Applying the concept more broadly seems like a fairly obvious possibility to consider. I'm sure there are plenty of engineering challenges ahead on that path, though, so it may turn out to be a dead end for some reason.

The most obvious potential challenge that occurs to me is the "fun" of keeping the various nozzles needed operating evenly, given that they're generally very long thin slits that need to be kept un-clogged. If you get a bit of dirt wedged in one, or bend the edge somehow, the airflow will be absent where the blockage is and faster in other places. Obviously, you'll want ways to avoid that happening altogether, but you have to assume it'll manage to happen anyway, so you'd want the avionics to be able to at detect / adapt to that kind of condition.

Fun stuff! :-D


xanthraxoid t1_j3hflwd wrote

> it would probably be similarly effective for personal protection.

Unlikely. The virus containing moisture particles are pretty large and easy to catch when you exhale them, but they rapidly dry out and become very small - small enough to make catching them much harder.

I would assume that a neck gaiter would be very much like a face mask on that front, though obviously much less effective because of not being designed / tested for the purpose.

More info here - I recommend having sci-hub to hand, too.


xanthraxoid t1_iyerj4h wrote

I use YouPipe on my phone, but I've never had any difficulty finding an online downloader by just googling "Youtube MP3 Download" or the like. Which one turns up might vary from time to time, but there's always one that works :-P

Others have also mentioned youtube-dl, which is probably the gold standard. It has a GUI (not sure if it's part of the default download - I got it via my linux distro) and has lots of options for audio only or video or whatever...


xanthraxoid t1_iyeqcki wrote

The story is total balls, sadly, but it's still amusing :-)

For a bit of historical context - nobility captured in battle (basically anyone in a suit of armour and on a horse) would have been kept for ransom and looked after very well (no removal of fingers!) and anyone else would have been slaughtered on sight. The archers would all have been yeomanry and in the latter category (no removal of fingers, or at least not then sent back without them...)


xanthraxoid t1_iyddcmb wrote

There are quite a few random things that get special additives to make them really bitter (e.g. Denatonium, a.k.a. "Bitrex")

It's put on button batteries (which are Bad News to swallow), used for special nail varnish to discourage nail biting, added to various toxic substances that people might otherwise be tempted to consume (such as "denatured alcohol" and antifreeze which is naturally quite sweet) and so on.

I'm not sure if this is what's used to discourage snorting of crushed pills (our noses don't "taste") and it's difficult to imagine something that would irritate your nose without also irritating any other mucous membrane (such as your entire digestive system from lips to lips)

I did a quick google and everything I found seemed to be focussed on making pills physically resistant to crushing, so maybe they haven't found anything that fits the bill here. I wonder if there's something they could use that would be inactivated by stomach acid quickly enough to not irritate your stomach, but you would definitely not want in your nose.

Of course, if you're addicted to something, then it would take some pretty persuasive deterrent to stop you getting your fix - smelling like shit probably wouldn't do it :-/