1

Physiology & Medicine / Re: Why have humans evolved into being less and less tolerant to raw meat?

« on: Yesterday at 12:13:25 »

My great-grandfather said of porridge: "If you eat that for a hundred years, you will live a long time". Or maybe it was pickled herring.

2

Just Chat! / Re: If Religion Wants To Survive...

« on: 29/03/2023 15:39:11 »

Religion provides the Choice of Celibacy, unhelpful?

...and the Sin of contraception. But buggering choirboys is OK if you are a celibate.

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General Science / Re: [Asking ChatGPT] Why would LED ligths in cargo ship is a good idea?

« on: 29/03/2023 15:24:26 »

ChatGPT is a system for cutting and pasting superficially relevant text published on the internet.Thank you for your enquiry. We look forward to wasting more of your time in future.

4

New Theories / Re: How close are we from building a virtual universe?

« on: 28/03/2023 17:54:41 »

We have built and continue to build a lot of Physics on the idea of particles existing.   Maybe they don't, it could all be waves and oscillations in some underlying field.

Not entirely true. We describe what we have observed in terms of particle and wave mathematics, but stating that x "is" y is the domain of philosophy and pointless vanity, not science.
My point is that we generally pursue our research whenever the observed universe doesn't behave exactly as our model predicts, so the answer to the original question is that we are as close to building a virtual universe as is necessary except for the following [insert unexplained phenomena here].

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New Theories / Re: Gravitoelectroweak Hypothesis?

« on: 28/03/2023 15:40:52 »

The test of a hypothesis is the accuracy of its predictions. I don't see any.

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General Science / Re: [Asking ChatGPT] Why would LED ligths in cargo ship is a good idea?

« on: 28/03/2023 11:45:58 »

The answer is simple. Music is made by animals, for communication. Noise is made by machines, because there's something wrong.

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Physiology & Medicine / Re: Can taking a pint of blood off the body reduce your blood pressure?

« on: 26/03/2023 16:47:25 »

Sadly, no. Blood pressure is the pressure required to maintain the required volume flow through a system of elastic vessels which can expand and contract in response to chemical and physical triggers. When substantial quantities of blood are lost, some (mostly peripheral) vessels constrict in order to maintain sufficient oxygen to the "more vital" areas.  Chemical intervention is required to reduce blood pressure to prevent further damage in the case of stroke.

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New Theories / Re: Global worming theory

« on: 24/03/2023 18:25:38 »

There may be a small spelling mistake in the title of this thread.   

Hence my comment about parasitic helminths. It's more fun than climate change, though worms do have a lot of impact on that too.

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Technology / Re: Can you explain this demonstration of a capacitor?

« on: 24/03/2023 05:55:11 »

Ideally,  in the absence of any external circuit, the experimenter's hand, or residual charge on the dielectric, Q would remain constant as the dielectric is an insulator. Energy is now stored as stress in the dielectric.

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Just Chat! / Re: Dissertation Help services for PhD and masters students

« on: 23/03/2023 16:51:23 »

Actually, AI won't help- at least in a scientific PhD.The whole point of a research degree is to discover or elucidate something that nobody else has seen or explained, so combing the internet for existing knowledge won't answer the question.

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Technology / Re: Can you explain this demonstration of a capacitor?

« on: 22/03/2023 23:10:51 »

Sadly, vhf's wiring diagram is correct, which is why the demonstration is so bad!  Also confused by the use of the word "electrometer" which although etymologically correct, is more usually associated with measuring charge or voltage rather than current.

If the current meter had been wired "above" the capacitor in the diagram, the moveable plate would have been at ground potential, the insulating block on which the capacitor is mounted would have been unnecessary, and the ghostly hand could have been conveniently grounded with an antistatic strap. Problem is that the a maximum common mode voltage of the electronic ammeter might then have been exceeded, so (guessing a bit at the dimensions of the capacitor) you'd need a battery-powered microammeter floating at around 1000 V to show the effect - not a common piece of kit.

Worth noting that the tuning capacitor of oldfashioned radios (the ones with knobs and analog dials)  is a variable-area device, and in almost all cases the moving vanes are grounded so that the frequency doesn't drift when you put your hand on the knob. But you wouldn't expect MIT physicists to lower themselves to a 100-year-old technical trick!

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Technology / Re: Can you explain this demonstration of a capacitor?

« on: 22/03/2023 15:11:21 »

 Is there any discernible pattern or explanation for the deflections shown on the ammeter during this part of the demonstration? 

Badly constructed equipment. The whole kit should be enclosed in a grounded Faraday cage with an extension rod to the adjusting knob. Precision electrostatics is not for amateurs.

It's a pity that they have assembled some very nice kit but not spent a few dollars on a simple dog cage to make it work properly!

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Technology / Re: Can you explain this demonstration of a capacitor?

« on: 22/03/2023 15:04:29 »

How did they tell the charge Q to stay on the plate?

If the plate is very large and the electrometer has a very high impedance, relatively little charge will flow when the plate is moved. Keithley electrometers are pretty good in that respect but you can do better in principle with a potentiometric system and electrostatic null detector. It's the way we used to measure charge in  ionisation chambers used for radiation measurement, but it all gets a bit complicated for modern undergraduates who would probably find it offensive because it takes actual skill, can't be done with a mobile phone, and is therefore noninclusive of clumsy idiots.

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Technology / Re: Can you explain this demonstration of a capacitor?

« on: 22/03/2023 07:59:13 »

The operator's hand is one plate of a very large capacitor, initially at earth potential (if he has bare feet) or at several kV (if he has walked over a carpet with rubber soled shoes). It's bound to have some effect on a nearby electrostatic system. Once he has touched the "grounded" equipment, his charge is equilibrated and he becomes part of the experiment.

I've not seen a Braun electroscope before - neat piece of kit! It looks as though it is connected to the insulated capacitor plate, so bringing the experimenter's hand close to it will definitely affect the charge on the insulated plate.

Crap demo!

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Just Chat! / Re: In every country on the planet, majority of rapes are not reported.

« on: 21/03/2023 14:22:46 »

If they aren't reported, how do you determine "majority"? And "every country"?

Many crimes are unreported. The victim may fear reprisal, or consider that the effort of reporting outweighs any likely benefit, but in the case of rape there is particular problem of proof which demands evidence of penetration (not always provable) without consent (always disputable), and of taint: a significant number that do get investigated turn out to be malicious accusations so the authorities are at least cautious if not skeptical.

"Facing the abuser" is prejudicial and unnecessary. However awful the alleged crime, in a civilised country you aren't guilty until proved, so you are really talking about facing the accused. Now that isn't always required - evidence can be given by video or even audio link. But where is the right of the accused to face his accuser, as guaranteed by Magna Carta?

"Hours into getting a conviction" should be read as "a few days in police stations and  court, in order to destroy someone's life and put him in prison for several years." Seems like a fair balance of effort and reward.

Beware of poorly formed questions and facile answers that may undermine the foundations of justice.

16

Technology / How did they make the first screw?

« on: 17/03/2023 17:56:27 »

So I'm cutting a screw thread on a lathe. The lead screw turns and moves the tool along the workpiece, and the gear ratio between the chuck and the lead screw determines the pitch of my product screw. An everyday occurrence in thousands of workshops all over the world.

But the lead screw needs to be at least as precise as the one I'm making.

So how did they make the first lead screw?

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Just Chat! / Re: Generally speaking, how would Brits respond if...

« on: 14/03/2023 17:29:11 »

Tens of thousands of people queued to walk past the Queen's coffin.
In a city of ten million that means well over 99% didn't bother.

Those that did queued for up to 2 days to do so, and the show was time limited: there simply wasn't any chance of the other 99% getting in. The procession from Balmoral to London and the funeral were major television events watched by almost everyone who wasn't at the roadside.

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Chemistry / Re: Can glucose be synthesized without organic inputs as sources?

« on: 12/03/2023 23:21:26 »

Of course, there are peop[le who believe that, one day, we may be able to create living things from inanimate materials.

It would be difficult and pointless, but it has already happened without human or divine intervention so it's clearly not impossible.

19

Just Chat! / Re: On Gender Reassignment...

« on: 11/03/2023 17:52:33 »

I'm all for people doing whatever they want as long as (a) it doesn't harm or disadvantage anyone else and (b) I don't have to pay for it. But (a) isn't satisfied when a male rapist or professional athlete says he is a woman.

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Physics, Astronomy & Cosmology / Re: Do you change the spectrum of radiation inside an oven if you change its shape?

« on: 11/03/2023 17:45:41 »

So Planck was wrong after all.