sethoflagos

1 hour ago, J.C.MacSwell said:

Ram pumps work. They can elevate water above that of the velocity head, just not all the water contributing kinetic energy.

If velocity head was the maximum pressure harnessable by a water streams momentum, water hammer wouldn't be much of an issue.

Yes, I'm well aware of how ram pumps work.

But there was no ram pump in the system described, and therefore no means of channeling the input kinetic energy preferentially into the vertical output stream.

The 'logic' seems to be that running water out of a sealed header tank creates a partial vacuum (true so far) that can be used to suck up water from a lower elevation than the discharge.

13 minutes ago, exchemist said:

This all crap, by the look of it. 

Seconded. Just another PM dream.

As for the ram pump idea, if the incoming velocity head was higher than the required lift, the flow would climb the bank of it's own accord.

2 hours ago, TheVat said:

In third world countries, especially in the hot and humid conditions of those in the tropics, aflatoxin is a serious public health problem, both in agricultural storage of nuts and grains, and in its infiltration of residences.

I'm sure some supermarkets must stock it, but I don't recall seeing peanut butter in Nigeria. It's very much a US product.

Here, processed peanuts yield peanut oil and the dry product kuli-kuli which is mixed with various peppers to yield our signature barbeque spice mix suya.

Peanut oil and suya pepper have a pretty well indefinite unrefrigerated shelf life even in our climate.  

3 hours ago, JohnDBarrow said:

I think of Homo sapiens sapiens as being three subspecies: Caucasoid, Negroid and Mongoloid.

And yet despite being one of the master race, you ended up in your sixties shuffling round Walmart wondering who's fault it was you were still at the bottom of the heap.

Oh dear, how sad.

Time for you to head back to your cold lonely pond and crawl beneath your stone I think.

4 hours ago, StringJunky said:

I've never considered 'Bush Man' to be derogatory term and wasn't aware it was such until now. Sad.

This has been tested in South African courts. In what I consider to show a remarkably conciliatory attitude, the San and associated peoples stated that they didn't object to the term 'Bushman' providing it was framed in a positive context.

Obviously our racist little troll falls way short of that requirement.

10 hours ago, JohnDBarrow said:

I want nothing but a utopian world to come back to in any possible future lifetimes on this planet.

I SO want your dream to be realised as a dung beetle in elephant country.

A nice little lesson in humility though I'm sure it would be lost on you.

51 minutes ago, JohnDBarrow said:

I want to see an African bushman type society no more. It's time for those people to throw away their spears and ride in modern air-conditioned automobiles 

Why do you pick on Africans? Their impact on climate change has been negligible in comparison to those accustomed to riding in modern air-conditioned automobiles.

1 hour ago, JohnDBarrow said:

Since when did I ever advocate the murder of innocent persons?  Not making a baby in the first place is not the same as killing a living person. 

So how do you propose persuading 2 billion women of child-bearing age that your material and spiritual comforts require the vast majority of them to forego parenthood for the next fifty years? Friendly and reasonable discussion?

9 minutes ago, exchemist said:

You can still see some wisps of what may be down on the head of the bird in the video.

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.

4 hours ago, exchemist said:

Looks to me like a juvenile, from the yellow interior of the beak and its behaviour. That makes it harder to identify, as distinctive markings may not be fully developed. But I’m not a bird expert.

This one is a bit younger, but has still lost the yellow gape. The OP bird maybe barely fledged.

7 hours ago, zapatos said:

Where and when was the bird photographed?

Assuming it's N America or Europe 

12 minutes ago, dimreepr said:

My apologies @sethoflagos, it was intended as a joke but I was drunk at the time. 

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.

59 minutes ago, exchemist said:

I don’t see how any reproducible phenomenon of nature can fail to be due to something physically and objectively real in nature. You can’t make a model without something for it to be a model of, surely?

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).

55 minutes ago, TheVat said:

Duhem-Quine, as @sethoflagos mentions, reminds us that most truths are predicated on a bundle of other proven hypotheses...

I think Duhem Quine allows that background assumptions can be teased out and made explicit.  They don't have to remain unstated.  It is just saying that it is always possible that some background assumption was overlooked and therefore a perfect falsification is not possible in the real world.  

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.

1 hour ago, exchemist said:

Yes, scientific theories are models, the map and not the territory, and sometimes we have multiple maps that show different aspects of the territory, or which are sometimes not easy to interpret.

Quite. We might even extend this to a system of mutually consistent interacting theories forming a coherent body of understanding. 

1 hour ago, exchemist said:

But that does not mean there is no territory, or that we can make up our own ideas about it.

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.

39 minutes ago, Eise said:

I completely agree with @TheVat. The idea of 'truth' makes no sense if we do nor relate to an objective reality. Our scientific theories are about something. And they can be wrong, or true, in their (limited) domain.

'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.

22 hours ago, swansont said:

I wonder how much of that is from the limits of human hearing. They might be very different above ~20 kHz, but we’d never know just by listening.

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.

4 hours ago, Xtydelll said:

When materials break, like tearing paper or unwinding duct tape, here's what happens:

Energy Release: When you tear or unwind, the bonds holding the material together are broken. This breaking releases energy suddenly.

Vibrations: This energy makes the tiny parts of the material (like fibers in paper or adhesive molecules in tape) move rapidly back and forth. These rapid movements are vibrations...

Wouldn't 'tiny parts' have tiny vibrational wavelengths?

Have you noticed how tearing paper, undoing Velcro, and electrical arcs all sound remarkably similar?

1 hour ago, Mordred said:

There was an older multiverse model that has matter in one universe with antimatter and time reversal in the other universe. It long ago fell out of any research interest. ( due to better understanding of anti-matter in that the time reversal is a mathematical treatment for symmetry purposes and not actuality)

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?

39 minutes ago, geordief said:

I didn't know there was absolute time at any scale.

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.

1 hour ago, geordief said:

Would that be into multiverse theories?

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.

5 hours ago, geordief said:

What happens if we plug t-10{-43}secs into the equations?

Do we come out the "other side"?

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.

23 minutes ago, Moontanman said:

Shouldn't the danger a chemical represents be tied to the likelihood of actually being exposed to it?

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.

Just now, zapatos said:

I'm no chemist, but I would think nothing (or everything) is intrinsically 'deadly'. Doesn't the 'deadliness' come from level of exposure? In a small enough dose nothing will kill us, and in a large enough dose everything will kill 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. 

31 minutes ago, Moontanman said:

So some deadly esoteric chemical we're unlikely to ever come in contact with is more dangerous than the common but deadly chemical that is in nearly everything we eat? 

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.