sethoflagos

Yes, it's not long out of the nest. Difficult ID until you're familiar with them. They're so very different to the adult form.

This one is a bit younger, but has still lost the yellow gape. The OP bird maybe barely fledged. Assuming it's N America or Europe

I had no issues with your post. Guess I must have missed something.

For me it has to be David Attenborough. I find his series as fascinating and awe-inspiring now as I did as a child. For YouTube, the group of channels put out by the profs and associates at Nottingham University seem very well curated and pitched at an accessible level. Professor Poliakoff on the Periodic Videos chemistry channel is particularly entertaining. Associated channels are Sixty Symbols (physics) and Numberphile (maths).

The articles themselves can often be problematic, but publications given in the references at the bottom of the page can be more helpful.

At time of writing, I was thinking of 'the ether'. We may be on a surer footing with space-time (when we get around to understanding what space and time really are). It helps keep a foot on the ground perhaps. These days I find myself drawn more to an instrumental point of view even outside of the work environment. 'Shut up and calculate' is maybe the ultimate Ockham.

Quite. We might even extend this to a system of mutually consistent interacting theories forming a coherent body of understanding. Yes, but here's the rub. If some critical property of the territory is unmeasurable, then the idea runs into falsifiability problems. Duhem-Quine extend this by questioning whether or not the territory itself is merely an abstraction created by the body of understanding of which the proposed theory is a part. An unstated assumption if you like. Perhaps this goes too far, but since Duhem was a sound thermodynamicist, I think he's worth a mention.

'True' in the limited sense that certain measurable inputs may lead to certain predictable and measurable outputs without known contradiction. Perhaps that is enough. It says very little about the muddle in the middle though. One only needs to consider the many interpretations of QM. Is one of them true in an absolute sense? For the sake of our sanity, it may be as well to think so. But don't bet the house on it.

Indeed. If the common thread of these 'rip' sounds is that they are the combination of many small pressure discontinuities (as I think they are) then their acoustic spectrum will include a large high frequency component anyway.

Wouldn't 'tiny parts' have tiny vibrational wavelengths? Have you noticed how tearing paper, undoing Velcro, and electrical arcs all sound remarkably similar?

I'm struggling a little to recollect beer mediated musings from 30-odd years ago, so please bear with me. Am I correct in understanding your last point as CPT symmetry reversal is not a physically realisable phase change in contrast to say electroweak symmetry breaking or recombination?

Probably the wrong word to choose. 'Pointlike' may be better. Suggesting that an instantaneous 'now' of zero duration doesn't exist. So a unit of Planck time, say, wouldn't have any clearly definable start or endpoint.

More of a dual-universe speculation. Perhaps one way out of the t=0 conundrum is to drop the idea of absolute time at these scales in favour of a sequence of time intervals, one of which happens to span t=0. A form of quantisation if you will. The surface of that cell should have no associated infinities, but half of the boundary surface is time-reversed and that (the point you raise) would need to be addressed. It's probably complete tosh, but the idea of two universes being spawned in opposite time directions has a pleasing symmetry to me.

How would we know? From what I understand of CPT symmetry (not much), an antimatter biased big bang expanding in the reverse time direction (from our perspective) would behave no differently to the universe we're in now, I think.

Not what the OP was asking. I don't live in the US. Sub-saharan diets typically don't include added sugar except for rare treats so your issue is less of an issue for the rest of us.

You're right, it's a question of degree. I seem to remember seeing the LD50 of carrots set at 40 kg. A bit much to eat at one sitting perhaps, but a caution to be wary of some extreme carrot concentrate. But the previously mentioned botulinum toxin is at an entirely different level. And cumulative poisons with no known positive biological function like lead and arsenic really have no clearly definable upper safe limit.

Sugar is simply not in the same league. It just happens to be something many of us choose to consume to great excess despite knowing that it will harm us. I managed to wean myself off sweets in childhood to the extent that even artificial sweeteners can make me feel quite nauseous. Yet the moment my weight drops below 70 kg (bout of malaria) I experience an intense craving for sweet tea. Quite a shock the first time it happened. But I learned that when my body really needs some glucose fast, it will tell me in no uncertain terms. So I don't buy that sugar is intrinsically 'deadly': quite the opposite. The real problem lies elsewhere.

I've downloaded it and will be very interested to see how it performs. I don't actually need much help in identifying a diederik cuckoo visually, but if the app picks up the die-die-diederik call I'll be impressed. I'll be even more impressed if it spots the very convincing local kestrel call the diederik makes when mobbed by the species it parasitises.

Fine distinction. I suspect such nuances would be lost on his target demographic. Maybe he was simply pointing out that sensationalist headlines can distort our perspectives. Some people need to be told that. He does undeniably important work in science communication so I don't really see the purpose of this thread. So what if he and his audience don't have much time for old white philosophers: it isn't as if an adult film starlet had spanked him with a rolled up copy of Scientific American or something.

Isn't this another way of phrasing Tyson's concluding sentence What point am I missing?

Just to be clear, I'm leaving discussion of resonance effects etc to others. They're two separate topics. In context, a shock wave signifies a pressure discontinuity - a step change in pressure level rather than the piecewise continuous waveforms of normal sounds. It indicates that something somewhere has moved faster than the speed of sound in air. It is characteristic of brittle fracture. No, that isn't it. When paper is wet, the fibre-fibre bonds are almost totally replaced by fibre-water bonds and water-water bonds. When torn it is the weak water-water bonds that dislocate leaving the fibres pretty well intact. Here there is no brittle fracture and hence no shock waves. The pieces come apart through viscous shear and what little energy is released is in the form of heat rather than sound. This is the opposite end of the spectrum to brittle fracture. Between these two extremes are various degrees of 'ductility' of which two common types are plastic deformation and viscoelastic deformation. They are a rather diverse bunch of mechanisms and are each separate topics in their own right. I'm not familiar with the product. I'd guess it could be somewhere in the viscoelastic regime but specialist adhesives would be more up @exchemist's street than mine.

Okay... Small steps. As the moisture content of paper rises from bone dry to something oto 30% by weight, the 'tearing' sound gradually diminishes to practically zero. Why do you think that is?

Define 'kind of'. What makes you think there is a vacuum under the tape? What do you understand by the term 'shock'? If it's 'silent', then what sound are you asking about?

Fracture mechanics can become very involved very quickly, but if we limit our scope to simple brittle fracture... Both fracture propagation speed and elastic recoil shock of a fractured solid are functions of the speed of sound in that material and typically many times the speed of sound in air. Therefore a space opens up faster than that information can be passed to the surrounding air resulting in a substantial vacuum. Eventually the pressure wave information gets passed on and the air rushes in at its own sonic speed to fill the void. When the void is filled the air it is brought to a halt with extreme rapidity and releases it's kinetic energy primarily as acoustic shock waves (variously known as 'surge' or 'water hammer'). This is the process that produces the loud 'crack' of a bullwhip. Now rather than one big whip imagine several thousand cellulose fibre 'whips' doing the same thing per second at a microscopic scale. That's the sound (at least a major component of it) of paper tearing.

Like a customised self-gravitating body ~100+ km diameter built from carefully redirected small asteroids to put it into a path of ejection from the solar system? Internal thermal energy may be a viable long term energy source (or nuclear). Deep subterranean accommodation caverns should give reasonable protection from small collisions. Not sure I'd pick the lifestyle choice myself...