1

Physics, Astronomy & Cosmology / Re: How are physical units defined?

« on: Yesterday at 22:35:48 »

Pedant mode: Heisenberg described the inherent indeterminacy of a phenomenon, not the uncertainty of its measurement.

It is possible to weight the odds in Heisenberg uncertainty, by using squeezed quantum states. You reduce the uncertainty in one dimension (which you care about), and accept that it will be less uncertain in another domension (that you don't care about).
- So if you were measuring a distance accurately (eg the length of the standard meter, or the length of a gravitational wave detector), you may care more about uncertainty in distance more than you care about uncertainty in photon momentum.
- Both LIGO and VIRGO use squeezed quantum states to improve sensitivity in detection of gravitational wave events.
- They both use real reflected photons to make the measurement
See: https://en.wikipedia.org/wiki/Squeezed_states_of_light

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Physiology & Medicine / Re: Why do medics persist in talking of "blood thinners"?

« on: Yesterday at 22:19:36 »

Perhaps if you describe the process of blood clotting as "blood thickening" (and eventually becoming solid)...
...then you might describe something that inhibits blood clotting as "blood thinning".

Many of our medical terms have been around for centuries, and are not technically accurate, but everyone uses them, and they are generally understood - and that is the purpose of communication.

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Physics, Astronomy & Cosmology / Re: How are physical units defined?

« on: Yesterday at 08:22:11 »

in wave mechanics there is always a classical uncertainty when measuring frequencies or counting wavefronts

As I recall, one earlier definition of the meter specified:

The metre is the length equal to 1,650,763.73 wavelengths in vacuum of the radiation corresponding to the transition between the levels 2p10 and 5d5 of the krypton 86 atom.

https://en.wikipedia.org/wiki/History_of_the_metre#Krypton_standard

So it's not like they are limited to measuring an integer number of wavelengths (here they measured 2 decimal places of a wavelength)...

There are fundamental limits to measurement due to Heisenberg uncertainty, but you can usually overcome these limits by taking the measurement over a very long time period, which allows reduced uncertainty in position or momentum.

You have to be very patient when making fundamental physical measurements...

4

Physiology & Medicine / Re: Why has no Warp Speed Pill been invented to Stop Periods?

« on: Yesterday at 08:10:53 »

Warp Speed...I am amazed people are so forgettable  even after the media has drummed into their skulls over the past 3 years.

"Warp Speed" goes back at least as far as Star Trek in the 1960s.
- But the contraceptive pill made more of an impact on the general public in the 1960s

"Operation Warp Speed" is a rather more recent usage of the term.

5

Physiology & Medicine / Re: Why has no Warp Speed Pill been invented to Stop Periods?

« on: 06/08/2022 10:32:04 »

Warp Speed Pill

Why call it "Warp Speed"?

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Physics, Astronomy & Cosmology / Re: What images do you most want to see from JWST?

« on: 06/08/2022 02:04:11 »

There is a theory that seeing too much of a black hole and its functioning may cause insanity.

Source, please?

There is very little of a black hole you can see from outside the event horizon
- And not a very long time that you can observe a black hole from within the event horizon.
- But I imagine that watching an accretion disk could be rather hypnotic
      - provided you didn't get too close, and get toasted by X-Rays
      - or join it and get turned into X-Rays

7

Physiology & Medicine / Re: Is Processed Food Healthy ?

« on: 06/08/2022 01:54:17 »

Is Processed Food Healthy ?

It depends entirely on what sort of processing you are talking about.

Some researchers gave volunteers goat steaks to chew on.
- raw, they were unable to extract much useful nutrition - they couldn't even break up the meat into pieces small enough to swallow
- I imagine that chewing on a whole goat would be even less effective!
- Ground-up meat is able to be digested more easily
- Cooked, they were able to chew the food quite effectively

So, cutting, grinding and cooking are ways to gain far more nutrition out of both meat and plant products.

Similarly, fermentation is able to extract nutrition from food sources where humans would not be so successful (think bread, beer, chocolate, kimchi, etc). It add flavours, preserves the food and discourages colonization by pathogenic bacteria.

8

Plant Sciences, Zoology & Evolution / Re: Evolutionary DNA Leaps in Chromosome counts?

« on: 06/08/2022 01:42:49 »

Chromosomes can merge (reducing the count of chromosomes) or split (increasing the number of chromosomes).
- Recent research has found that use of CRISPR can chop up a chromosome, leaving a "spare" bit floating around in a cell nucleus
- Neither of these processes need be immediately fatal to a cell, since you still have the same number of genes
- The problem comes when the cell divides - does each "daughter" cell still have a full set of genes?
- And in the next generation of organism - do they still have a full set of genes?

The centromere is a structure in the center of each chromosome that plays a vital role in duplicating DNA into each daughter cell.
- A split-off portion of a chromosome may lack a centromere, inhibiting gene replication (or sometimes, a new centromere may appear)
- Two joined chromosomes may have two centromeres, which leads to chromosome breakage
- So most cases of chromosome splitting or joining are bad for the individual organism (often leading to cancer) and the descendents (who will suffer high rates of genetic disease and infertility with the parent species)
- But in rare cases, a descendent will receive two copies of the same mutation, allowing speciation
- Gene sequencing can identify cases where chromosomes have split or joined, since biologists can compare which genes occur on which chromosome.
See: https://en.wikipedia.org/wiki/Centromere

The leap from 46 or 44 Chromosomes to a working group of 48 chromosomes in the new species to be Gorillas

The human genome appears to be the result of the fusion of two chromosomes that remained separate in other primates (ie humans went from 48 to 46, while gorillas & chimpanzees remained at 48).
- So "progress" (new species) do not always come from splitting chromosomes (fission).
- New species can come from fusion, too.
https://www.mun.ca/biology/scarr/Human_Ape_chromosomes.htm

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Physics, Astronomy & Cosmology / Re: What images do you most want to see from JWST?

« on: 04/08/2022 22:54:04 »

I would like to see stars circling the supermassive black hole at the center of our galaxy.
- At infra-red wavelengths, it should be possible to see more stars than we can see with ground-based telescopes
- and see how active the accretion disk is now
- By watching nearby stars move over a period of years, we should be able to predict when the accretion disk might fire up again.

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Physiology & Medicine / Re: Why has no Warp Speed Pill been invented to Stop Periods?

« on: 04/08/2022 22:08:56 »

did you really not understand the NPC comment?

My initial guess was "Not Politically Correct".

Thanks for expanding it.

11

Physiology & Medicine / Re: Why does nobody seem to care that covid can cause erectile dysfunction?

« on: 03/08/2022 22:39:08 »

the risks of vaccines to ...period regularity

Today's Naked Scientists podcast has a story about this (5 minutes).
- But these researchers used a Twitter survey for people to recall their experiences after vaccination.
- This does carry the risk of self-selection bias

https://www.thenakedscientists.com/articles/interviews/did-covid-19-vaccines-affect-womens-periods

12

The Environment / Re: What's causing cool and North winds in northern MN?

« on: 03/08/2022 22:20:16 »

Weather is a chaotic system (in the mathematical sense). Local weather can have arbitrarily large deviations from the average at that location.

But the total amount of solar radiation striking the Earth is roughly constant, so if it's colder-than-average where you are, it is warmer-than-average somewhere else. That's why climate scientists measure global average temperature when looking at the global impacts of CO₂ emissions.

I was amused when Donald Trump trumpeted record cold temperatures in the USA as proof that global warming was a hoax.
- But the cause of cold air over the USA was a bubble of hot air moving into the arctic past Greenland, recording the highest ever temperatures recorded there.
- Regardless of the fanfare, the upward trend of increasing temperatures is proceeding apace.

13

General Science / Re: Can you use capillary action to clean water or reduce salinity

« on: 03/08/2022 22:09:48 »

TDS meters are very inaccurate

I saw a very cheap TDS meter (Total Dissolved Solids) at my local hardware store, claiming 2% accuracy or ±1ppm from 1ppm to 1000ppm.
- That sounds a lot more accurate than human taste-buds
- And less liable to become a self-fulfilling prophecy

If you want to improve on taste-buds, and have a Digital Volt-meter, you can set it to Ohms range
- Now that really does have some accuracy problems:
- For sampling both glasses, you need to have the probes:
       - The same distance apart
       - The same angle
       - The same depth in the water

Frankly, the TDS meter sounds like the only reasonable way to go...

When you report your results, please also report on:
- How much water originally went into the first glass in the evening
- How much was left in the original glass in the morning
- How much made it to the other glass
- And hence, how much was lost (to wetting the paper towel, or evaporation)
- Whether the water height in the second glass was higher than the height remaining in the first glass (a level photo would be good...)

14

Physiology & Medicine / Re: Why does nobody seem to care that covid can cause erectile dysfunction?

« on: 03/08/2022 09:53:18 »

Perhaps ED should have been part of the vaccination campaign - but staid officials from government departments don't want to be talking about reproductive health on national television.

On womens' health, the anti-vaxxers made a lot of noise about the risks of vaccines to pregnancy and period regularity, but they ignored:
- The considerable risks of COVID infection to pregnancy
- The normal variability of periods: I saw one study that used anonymized data from period tracking APP, which showed vaccination caused an average 1 day change in period - in the presence of a "normal" variability that was much larger (even after they excluded women with irregular and missing periods)

15

The Environment / Re: Is global warming man-made?

« on: 02/08/2022 22:05:01 »

the amplitude of the seasonal variation exceeds the year-on-year cumulative change

Sure, and the daily variation in temperature exceeds the year-on-year cumulative change.
- And if you measure the temperature across the arrival of a cold front, the hourly variation in temperature exceeds the year-on-year cumulative change.

There are conceivable (but not yet understood) slight links between temperature and phase of the sunspot cycle.
- So, in my book, any temperature measurement averaged over a period of < 10 years is talking about weather, not climate.

16

Physics, Astronomy & Cosmology / Re: How are physical units defined?

« on: 02/08/2022 10:23:14 »

we just assume that distances are somehow axiomatic

A lot of people (most people?) are confused when they first run into concepts from Special Relativity whereby observers in different frames of reference will will come up with a different distance and time between the same same two events.

17

Just Chat! / Re: What is on your bucket list?

« on: 01/08/2022 23:00:46 »

I ticked one item off my bucket list earlier this year - I went to see the Aurora (the Australis version).
An overnight plane flight to around latitude 60° South, zig-zagging above the cloud-tops to give everyone good views of the aurora.

18

General Science / Re: Can you use capillary action to clean water or reduce salinity

« on: 01/08/2022 22:55:29 »

say for instance the salinity was reduced by 20% in the second cup.
Then the 2nd cup could be used as the starting cup up for a third cup to reduce salinity by another 20%

You can interpret this the right way or the wrong way.

Wrong way: If each paper towel reduces the concentration of salt by 20%, then after 5 paper towels, the concentration of salt would be 0%

Right Way: If each paper towel reduces the concentration of salt by 20%, then there is 80% of the salt left.
After 5 paper towels, there is 0.8⁵ salt left, or 33% of the original concentration.

19

General Science / Re: Can you use capillary action to clean water or reduce salinity

« on: 01/08/2022 11:49:47 »

If capillary action made water run uphill...

That's what trees do - a fine capilliary in the trunk raises the water quite high, and transpiration does the rest...

But it uses solar power to drive the water cycle.

20

General Science / Re: Can you use capillary action to clean water or reduce salinity

« on: 31/07/2022 22:28:51 »

Having just failed a COVID test

So you are saying that you failed, but the test method was a success...
- Get well soon!

PS: In Australia, demand for PCR capacity has dropped, so some laboratories are now routinely checking for COVID, Influenza (A & B) & RSV; several respiratory viruses circulating in our winter.