181

New Theories / Re: Do a Finite Amount of Infinitesimals Sum to a Finite Amount?

« on: 04/10/2022 14:32:15 »

Completely off topic: Eternal Student it's a great pleasure to see your return, I really missed your mathematical exactitudes. I appreciate their was a lack of suitable material for you to intervene.

182

Physics, Astronomy & Cosmology / Re: How can I start learning quantum physics alone?

« on: 30/09/2022 11:23:11 »

Yahya, I commend your interest in expanding your physics knowledge. A lot of contributors post on topics they have no understanding of with the absolute certainty that is only available to the truly ignorant. Unless one understands conventional physics there is no hope of any coherent new concepts being developed. Quantum theory is a particularly difficult subject-much of it is counterintuitive. I have no more than a basic knowledge of physics and would not attempt to explain quantum theory to anyone. Relativity is another counterintuitive theory and here I might just be able to explain the basics of special relativity but not so with general relativity. A quote attributed to a physicist( I can't remember who it was ) was "if you think you understand quantum theory you haven't been paying attention", or words to that effect. I hope this does not discourage you.

183

Plant Sciences, Zoology & Evolution / Re: Could a chicken fly?

« on: 22/09/2022 19:02:27 »

I have seen dead chickens fly at several hundred kilometres/hour. Bird strike tests on turbofan engines. This proves "chickens can fly"!

184

Marine Science / Re: jar of water hypothetical question

« on: 20/09/2022 11:56:00 »

According to a quick google search the bulk modulus of water is 2.2Gn/m². I don't have the time or motivation to do a calculation for 200ft -0 at the moment. I'm sure some other member will oblige.

185

New Theories / Re: Lifting One Weight Higher Than Another Drops

« on: 07/09/2022 10:56:20 »

In the realm of science, hypotheses and theories can be falsified but not proven. In mathematics a proof is possible and I think only in mathematics can a proof be possible. Emmy Noether's work is a mathematical argument and hence open to proof-qed.

186

Just Chat! / Re: Alancalverd is making me jealous!

« on: 19/08/2022 18:59:31 »

I am sure you do have fun-more power to you.

187

Complementary Medicine / Re: Hoodia - sleeping problems

« on: 13/07/2022 21:49:23 »

Benzodiazepines and other drugs which are gaba allosteric modulators are what most medics will prescribe for insomnia. I cannot stress enough how dangerous these substances are. They all produce addiction with withdrawal symptoms that can be life threatening. The general consensus is that heroin addiction is "a walk in the park" compared to benzodiazepine/z drug addiction. There is also mounting evidence of these substances causing early onset dementia. I suffer from regular insomnia, I know what it's like but it's no where near as bad as the "cure".

188

Just Chat! / Re: It's too quiet: I'm seeking a recommendation for a thread to read.

« on: 12/07/2022 14:44:35 »

Eternal student, I hope your family are ok. Covid seems to be very erratic in terms of symptoms and severity of illness, even for the vaccinated. I assume I had it(big assumption) as I did not bother doing an antigen test this time. What led to this assumption is that I got a collection of signs and symptoms very similar to the vaccine (Pfizer) side effects, which I have never got from viral infections before. It was however very mild overall. Wishing a quick recovery for all.

189

Just Chat! / Re: It's too quiet: I'm seeking a recommendation for a thread to read.

« on: 11/07/2022 13:32:47 »

Eternal student, i'm sure our resident philosopher alancalverd,  has plenty of conundrums and paradoxes to stimulate your analytic skills. Hope he doesn't blacklist me for this suggestion!!

190

Physics, Astronomy & Cosmology / Re: Why can't i understand the andromeda paradox?

« on: 08/07/2022 12:43:11 »

Eternal student, all is clear this morning though I don't feel 100% yet. It's simply two participants(halc won't allow observers-he's correct) in different frames disagreeing on the timing of an event. My malfunctioning engineering brain viewed the two frames as being sufficiently similar as to consider them equivalent. A higher speed of one participant would give a greater slope to your green line. The wording in the wiki article(penrose's version) still 'hurts' my brain. Many thanks again.

191

Physics, Astronomy & Cosmology / Re: Why can't i understand the andromeda paradox?

« on: 05/07/2022 16:24:22 »

Thank you, eternal student, for your detailed reply. I can follow your reasoning explicitly, however I can't grasp the concept, if that makes any sense. Bottom line: I think I have covid too. I had sudden onset low back pain and brain is not in gear and i'm making mistakes in everything I do. I will return in a few days(hopefully).ps i'm fully "vaxxed" as the conspiracy theorists would call it.

192

Physics, Astronomy & Cosmology / Re: Is the inverse square law only approximately correct in general relativity?

« on: 21/06/2022 18:34:27 »

I don't want to sound overly contentious but I see a dimensional conflict in your integration result: how can area be equal to a linear expression ie 4πr? I am quite familiar with cylindrical and spherical coordinates but I can never remember the expressions and I would have to look them up any time I need them, especially the spherical.

193

Physics, Astronomy & Cosmology / Re: Is the inverse square law only approximately correct in general relativity?

« on: 21/06/2022 14:48:47 »

One small addendum, not directed at previous contributors but more for general readers. I get the impression that a common misunderstanding is that the inverse square law always holds in non-extreme(ie non relativistic) scenarios. This is not so: the inverse square law applies only to point sources(or sources that can be interpreted as point sources), an infinite line source will have a 1/r decrement and an infinite surface source will be constant at all distances. Real world sources of line and surface types will require additional calculations to determine field strength.

194

Physics, Astronomy & Cosmology / Re: Does The Gravity Of A Black Hole Travel Faster Than The Speed Of Light ?

« on: 14/06/2022 19:47:17 »

Pardon me for butting in but the easiest way to understand a black hole is in terms of escape velocity. As gravity gets stronger and stronger the escape velocity increases. When it reaches or exceeds c, the speed of light in vacuo, nothing including light can escape. I realise most of you understand this explicitly, this is for the op, neilep.

195

Plant Sciences, Zoology & Evolution / Re: What are your favourite Plant Pictures?

« on: 14/06/2022 11:33:15 »

Datura innoxia, the downy thorn apple. Difficult to grow successfully in my climate(Ireland) due to blight attack. This is my wife's hand near the flower, not mine.

downy thornapple.jpg (52.13 kB . 480x640 - viewed 8747 times)

196

General Science / Re: What is the actual Brayton Cycle efficiency?

« on: 09/06/2022 19:40:50 »

Nobody seems to be rushing to help. It's 50 years since I studied this stuff but there is a problem with your efficiency expression: the efficiency will be the net shaft work after the compressor work is subtracted from the turbine work all divided by the heat supplied. Your expression only has temperatures. Now if net shaft work is zero and you are employing a propulsion nozzle after the turbine then it's more complicated. I am in error, of course the net work can be expressed in terms of temperature values; on looking it up in my small tech library I find efficiency= T1-T2+T3-T4/T3-T2.

197

Physics, Astronomy & Cosmology / Re: What is the mechanism of Hawking radiation?

« on: 09/06/2022 16:15:41 »

Yes indeed I do enjoy any diversions that lead to improved understanding of any area of maths or science. The cancellation of infinities in quantum theory would be very hard for me to accept as rigorous maths. However I do understand that a theory which is not realistic in simple terms can be very useful if it explains observations and makes predictions that can be verified.

198

Chemistry / Re: Help with quoted enthalpy values, please.

« on: 04/06/2022 15:54:20 »

If your reaction produces two products the total delta h will be the sum of the individual delta h of each product multiplied by the molar concentration of each final product. Often delta h values are not easily determined by direct experimental method and are computed by known values associated with the initial reactants. Google the born-haber cycle.

199

Chemistry / Re: Help with quoted enthalpy values, please.

« on: 04/06/2022 13:30:02 »

It's 50 years since I studied this stuff and I really should not be hazarding a "guess" especially since physical chemistry was my worst performing subject. The enthalpy is for the formation of the product, 2 moles at 50kj each. You cannot ascribe it to the reactants without going through the full cycle of initial activation energy to produce the reactive species that participate in forming the new molecule. A lot of ionic reactions derive much of their net  negative enthalpy from lattice energy of the formed product.(I shouldn't have said anything-i'm sure I have confused you as much as myself)

200

Physics, Astronomy & Cosmology / Re: What is charge?

« on: 31/05/2022 15:08:56 »

Yea, that's pretty much as expected, thank you(s).