1

Just Chat! / Re: What are U listening to?

« on: 22/10/2021 15:58:31 »

Lancer, one of my faves
Clark Powell
Artist: Clorinspats

2

Chemistry / Re: How does one detect fake/diluted honey?

« on: 16/08/2021 19:09:40 »

Apparently, they do.
https://www.anton-paar.com/corp-en/products/applications/determination-of-honey-purity-and-quality-by-polarimetry/

3

Chemistry / How does one detect fake/diluted honey?

« on: 16/08/2021 18:58:24 »

You couldn't use the stuff we normally call "sugar" to make fake honey; it's sucrose and honey is largely glucose and fructose.

Depends how it’s done. When there is a poor nectar flow - we are about to enter one - beekeepers feed sucrose solution to tide the bees over. The bees will invert the sucrose, but you end up with a diluted flavour so you can’t (or rather shouldn’t) extract it for sale.
We also use an invert syrup with same glucose/fructose mix as honey so the bees don’t waste energy converting it, but same problem of saleability. Unscrupulous people could add the invert directly and I think this has been detected in imported honey.

But you could use golden syrup- which is a partially inverted sugar (and thus is much more similar to honey).

Honey police will get you 
Golden syrup contains high amount of 5-hydroxy methyl furfural (HMF). Honey is tested for HMF as it is a sign that the honey has been overheated in processing and adding golden syrup would push it above the legal limit.
Most amateur beekeepers don’t heat their honey in order to keep it as natural as possible.

Testing for fakes is interesting enough as a piece of analytical chemistry, but more than a little off topic.

That would be a very interesting topic. Particularly if you know a simple test to identify sucrose in honey.

Does polarimetry count as simple? I would expect that even a rudimentary polarimeter should be able to identify if significant amounts of sucrose had been added to a fructose/glucose mix…

https://en.wikipedia.org/wiki/Specific_rotation

4

General Science / Re: Where is Administration thenakedscientists.com ??

« on: 28/04/2021 11:07:29 »

Where is Administration thenakedscientists.com ??

Paradoxically, it depends on where you are.

If you look closely, you will see that Administration at this site is distributed in a thin shell about 6,350km from the center of the Earth.

According to Newton's shell theorem, if you are outside the altitude of the International Space Station, there will appear to be a large concentration of Administration at the center of the Earth.

Conversely, if you traveled to the center of the Earth, you would find yourself floating in a strange, Administration-free zone.

See: https://en.wikipedia.org/wiki/Shell_theorem

5

COVID-19 / Re: Side effect of COVID vaccines

« on: 14/04/2021 00:24:48 »

Yep, I had my second Pfizer vaccination 3 days ago. First one produced no symptoms, but yesterday was quite miserable and I decided I wasn't fit to fly. Shows that the system is working, but I think it would be worth warning folk that it can impair your performance a bit.

6

COVID-19 / Re: How are adverse reactions to vaccination monitored?

« on: 15/03/2021 11:38:54 »

The yellow card system seems to be well supportedbut as with any postmarket surveillance of a generally sound pharmaceutical, you are looking for the recurrence of undefined and possibly unrelated needles in a very large haystack.

Part of the problem is the word "after". I developed arthritis after receiving the Salk polio vaccine. But most of my cohort have some degree of arthritis and 60 years is a long time "after", so it would be difficult to justify an allegation of causality.  You can expect adverse reactions that occur within a week of any treatment to be quickly notified and investigated, but a month later the link becomes rather tenuous in the patient's mind and even a thorough diagnosis at postmortem is unlikely to trigger an investigation of the patient's recent history unless there is a significant local outbreak of something really unusual - full credit to Dr Li Wenliang for identifying COVID, given that he was an ophtlamologist, not a respiratory physician!

The problem also has a converse. If you vaccinate the oldest 30% of the population, you can expect a fair number to die within say a year of treatment, mostly of fairly common conditions.  Differentiating between random clusters (and there will always be clusters in a random distribution)  and actual correlated effects is difficult enough, and if someone identifies and publishes a cluster that appears to be correlated  with treatment, it is almost certain that others will be alerted to the possibility and begin filing yellow card reports on incidents that would have passed without comment previously, or would have been ignored in the death certificate in the presence of some other causative factor, so the natural occurrence rate is almost certainly underreported

7

That CAN'T be true! / Re: I don’t understand physics: does anyone understand physics these days?

« on: 30/12/2020 12:23:17 »

Paul Dirac gave a guest lecture at Princeton back in the day when people really did write on blackboards with chalk. At the end,  a distinguished professor said "I didn't understand the third line on the lefthand board."

Long silence, then the chairman said "Professor Dirac, do you have an answer?"

to which PD relied "It wasn't a question."

8

General Science / Re: Can you make a huge prism, and disperse light in different colors?

« on: 29/05/2019 20:15:39 »

The dispersion obtained from a CD (or similar) is due to diffraction. This can be verified by shining light with different spectral makeup on it and looking at the reflected patterns. If one has access to red and/or green laser pointers, one can easily see that a single laser point generates a whole diffraction pattern (multiple bright spots), and that the spacing of the diffraction pattern is different for red (typically 600-700 nm, depending on source) and green (typically 532 nm doubled Nd:YAG). One can also look at the "rainbows" produced from light from an incandescent source (continuous), and from fluorescent or LED lighting (a few narrow bands).

9

Physics, Astronomy & Cosmology / Re: Would particles orbit a falling body?

« on: 17/11/2018 19:47:12 »

No, at that close to the Earth, even a steel marble would be within the Roche limit.   Tidal forces generated by the Earth would exceed the gravitational attraction of the marble. For a steel marble you would have to be at least 708 km above the surface for this to not to be the case. 

For objects to orbit the marble, they would have to be within the marble's Hill sphere. A 0.5 cm radius steel marble would have to be ~1689 km above the surface of the Earth in order for its Hill sphere radius to be larger than it own radius, so this is the closest it could be to the Earth and hold anything in orbit around itself.

10

Physics, Astronomy & Cosmology / Re: What's a black hole made of?

« on: 09/10/2018 10:04:07 »

Light trapped by this monopole's singularity gravitational force also is without a wave dynamic, because of the monolithic nature of the monopoles gravity (no waves). So, with no Light waves...

This post seems to be suggesting that there can be no light waves within a black hole (ie no light and no photons)?

One tool used by physicists is the "light cone", a volume of space within which light could propagate in a given time.

And physicists are happy to draw light cones at any position outside a black hole's event horizon - and even extrapolate across the event horizon to predict what might happen inside the event horizon.

The results within the event horizon are weird to our eyes - for example, time and space axes appear to be interchanged.
- However, there is nothing that prevents light from propagating - providing it propagates towards the singularity at the center of the black hole
See: https://en.wikipedia.org/wiki/Light_cone#In_general_relativity

11

Physics, Astronomy & Cosmology / Re: Can we measure the one way speed of light?

« on: 10/06/2018 11:37:30 »

No.

ε₀ and μ₀ are measured in entirely separate, static experiments.

If the value of c depended on direction, at least one of these would have to be a vector so you would always get different values for either ε₀ or μ₀ depending on the polarity of the applied electric or magnetic field. You don't.

For anyone with a real interest in experimental physics it is worth noting that the relative values of ε_xyzand μ_xyz for some materials are indeed anisotropic tensors and the magnitude of c does indeed vary with the orientation of the material. The fact that the resulting birefringence effects are independent of the orientation of the material with respect to the fixed stars, phase of the moon, or anything else, strongly suggests that there is no aether or other universal frame of reference, so c₀ is independent of direction.

12

Physics, Astronomy & Cosmology / Re: Which is the Closest Star to Planet Earth ?

« on: 22/03/2018 00:21:21 »

@CliffordK I have to echo @Bill S comment.
That chart is fascinating. I knew some stars are getting closer, but didn’t realise they had comet like tracks. The dynamics of this system would be interesting to know.

They don't.   The graph shows distance vs. time. The shape shown for the the curves is an artifact of this.

Assume that the asterisks in the first line below is a star passing our solar system ( the asterisk in the second line) at some fixed speed in a straight line.  Thus each asterisk is the star's position relative to our sun at fixed time period apart.
**********************************
----------------*-----------------
A line joining any given asterisk on the top line with the asterisk on the bottom line gives the star's distance for that moment in time.
If you were to plot the individual lengths of these lines on a graph, you'd get a curve like the ones shown in the provided graph. You would be basically be plotting the graph the the function  sqrt(x^2+(vt)^2), where x is the distance of closest approach, v is the speed of the star relative to the Sun, and t is the time as measured from the moment of closest approach

13

Physics, Astronomy & Cosmology / Re: Which is the Closest Star to Planet Earth ?

« on: 21/03/2018 06:54:08 »

It looks like we need to kick our space program into high gear.  We have about 10,000 years to get to Barnard's Star, otherwise we may never have another chance.  20,000 years to get to Lalande 21185 before it is gone. 

The Centauri cluster of stars will be hanging around a little bit longer, but still, it might not hurt to try to get a rocket out there in 20,000 to 30,000 years. 

And, with our current rocket speeds, we may have to get an early start on some of the trips. 

14

Physics, Astronomy & Cosmology / Re: Why do clouds go red at sunset? Why not green, or some other colour?

« on: 28/02/2018 20:07:02 »

Excellent, context is always useful.
Although lead oxide is red I’m not sure that the tetraethyllead used in fuel produces a particulate which would reflect red, perhaps @chiralSPO  could help here. I suspect that the haze is from other pollutants and lead is an indirect cause. As you know particulates are removed from car exhaust by the catalytic converter, unfortunately lead deposits stop the catalyst working so they can’t be used in cars using leaded fuel, hence greater pollution.

I would bet that the red color from old cars is probaby due to NO_x emissions. NO₂ has a brownish-red hue, and it also reacts with volatile organics to form photochemical smog https://en.wikipedia.org/wiki/Smog#Photochemical_smog

15

General Science / Re: Why are some stains more stubborn / harder to remove than others?

« on: 18/02/2018 16:23:22 »

Stains are typically pigments.

Tomato colour is mostly lycopene. Lycopene is very, very red, and is non polar and therefore insoluble in the 'universal solvent' aka water, and so tends to soak in and stay in fabrics, but is soluble in solvents:

https://en.wikipedia.org/wiki/Lycopene#Staining_and_removal

It also has a nasty habit of diffusing into plastics where it can't be removed.

Red wine, coffee etc are different, it's the tannins that are widely present in plants that are the biggest problem. I'm not entirely sure what the chemical basis is, but googling around seems to imply that tannins actively bond to fabrics as they dry. Best to remove them while they're still wet, but the stain can often still be removed later by using acids or alkalines to break them down.

16

Chemistry / Re: Is homemade wine safe?

« on: 19/01/2018 01:24:12 »

From wine to recreational inhalants. Slippery slope. 

(major tangent, happy to split this off into another thread if people are interested):

Actually, I think alcohol is more similar (in terms of chemical, biochemical and metabolic profiles) to inhalants and anesthetics (other simple molecules, which have low binding affinities to several receptors) than to drugs like opiates or cocaine, or psychedelics (which are more complex molecules that specifically target and bind to one or two types of receptors)

This makes simple "solvent" drugs much more dangerous than their more complex counterparts for two major reasons:

(1) Much larger doses of non-specific drugs are required—doses of ethanol are measured in deciliters or ounces, while highly potent and specific drugs are usually counted in mg (sometimes even only µg). This will tax the metabolism substantially, and also makes straight-up chemical toxicity more problematic (nobody ever got liver poisoning from lsd). I believe that the intoxicating effects of both methyl alcohol and allyl alcohol are probably quite similar to those of ethanol, but both are metabolized to fantastically toxic compounds: methyl alcohol is metabolized to the highly toxic formaldehyde and formic acid, as alluded to in the OP, while allyl alcohol becomes highly electrophilic acrolein and acrylic acid.

(2) There is no antidote for a non-specific drug. If someone ODs on morphine, Naloxone can reverse it; if someone ODs on diazepam, flumazenil can reverse it. If someone ODs on ethanol (or toluene)... you basically just have to give life support and try to flush their system, and hope they recover. (This second point is somewhat of an oversimplification, but you get the idea...)

17

Physics, Astronomy & Cosmology / Did Thomas Harriot help Johannes Kepler

« on: 30/11/2017 12:48:41 »

Harriot developed his algebra via Vieta and his assistant Nathaniel Torporley. In the Harriot papers he was corresponding with Kepler via an intermediary Johannes Erikson who travelled between the two with written correspondence. How likely is it that Harriot's algebra got to Kepler?

18

Physiology & Medicine / Re: How does breathing into a paper bag stabilise breathing problems?

« on: 25/11/2017 12:25:04 »

The normal pH - acidity level - of the blood and body fluids is about 7.4; a contributor to this is carbonic acid (H₂CO₃) arising from the carbon dioxide (CO₂) released from respiring cells.

Some of this carbon dioxide is carried back to the lungs dissolved in blood plasma; a small amount binds to proteins in the blood; the bulk enters red blood cells where an enzyme called carbonic anhydrase catalyses the formation of carbonic acid, which dissociates to form bicarbonate (HCO₃^-) and hydrogen ions:

CO₂ + H₂O H₂CO₃ H⁺ + HCO₃^-

This bicarbonate exits the red blood cell and enters the blood plasma, which carries it to the lungs. There, the relatively low concentration of carbon dioxide shifts the above reaction equilibrium back towards the left, regenerating carbon dioxide, which diffuses into the alveoli and is exhaled. The high oxygen concentration also displaces carbon dioxide bound to haemoglobin, and this too moves into the alveoli.

Critically, the concentration of carbon dioxide in the lung dictates the rates at which carbon dioxide (as dissolved CO₂, CO₂ bound to haemoglobin, or CO₂ carried as bicarbonate) can leave the body. So if you hyperventilate then you will promote the loss of carbon dioxide from the body. Since, at rest, CO₂ is being produced in tissues at a relatively constant rate, this will lead to a net reduction in carbon dioxide and hence a loss of carbonic acid from the tissues. The reduction in carbonic acid will lead to a respiratory alkalosis (blood and tissues becoming more alkaline), which produces the strange symptoms we experience, of dizziness, and tingling in the peripheries.

Breathing in and out from a paper bag will help because the oxygen concentration in exhaled air is quite high, so there is no reduction in tissue oxygenation. However, the exhaled CO₂ is returned to the body, reducing the rate at which further CO₂ is lost and also encouraging some more to dissolve back into the blood and reverse the alkalosis.

19

Physics, Astronomy & Cosmology / Re: What does "time-like" mean in the following sentence?

« on: 27/10/2017 21:08:53 »

By Neutrino
"
    If two events are time-like separated, then an object can travel from the first event to the second event with a velocity v<c.

    Events separated by a time-like interval are always arranged in the same order in time. That is, if an observer O deduces that event A happens before B, then another observer O', moving relative to O, will also come to the same conclusion. There is a before and after. And there is a possibility that that event A will influence event B. (Cause and Effect.)

    In a space-like interval, an object can be present at both events only if it travels at a velocity v>c. Since no object with mass can travel at such a speed, the two events are not causally connected. Also, there is no particular order between A and B(in time) if they are space-like separated.

    On a spacetime diagram, for time-like events A and B, B will be within the light-cone of A and vice-versa. For space-like intervals, one event is outside the light-cone of the other.  "

And light propagate at 'c', which is a definition made by a ruler and a clock

20

Chemistry / Re: How can I remove iron oxide stains from quartz?

« on: 24/07/2017 10:34:42 »

That's because it is also called Ethanolic Acid.

Close.
It's like Christmas, there's noel.
Ethanoic acid.

Re "Acetic acid solidifies at quite a high temperature compared to hydrogen oxide. Therefore, it is the solids you want to save and not the liquid. "
No.

When you freeze vinegar the first crystals to form are ice (simply because there's about 20 times more water than acid) and not much use.
You keep the liquid, not the solid.
The phase diagram looks something like this
https://www.researchgate.net/figure/286266698_fig2_Fig-2-Phase-diagram-for-acetic-acid-and-water-5