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Just Chat! / Re: If I rapidly waved a fridge magnet past my heart, would it cause a heart attack?

« on: Today at 01:56:21 »

Geomagnetic storms can induce damaging high currents at low frequencies (<0.1 Hz) in long conductors like electrical transmission lines and oil pipelines.

These high currents originate from voltages induced between points on the Earth's surface thousands of km apart.
- However, your average human rarely stands with their feet more than 1 m apart
- And dry skin is a fairly good insulator for voltages up to around 30V
- In Western countries, most people have insulating soles on their shoes.
- So low-frequency electrical currents are unlikely to be to blame.
https://en.wikipedia.org/wiki/Geomagnetically_induced_current

To pick up an electromagnetic signal efficiently, you need an antenna on the same order of magnitude as the electromagnetic wavelength
- Since the human body has a dimensions around 1-2 m, but these wavelengths are >3 million km, one could assume that there is very little induction into the human body.
- It would need to be > 50mV to have any impact on the functioning of nerves and muscles.

Probably, a fridge magnet in contact with your body would induce greater voltages and currents in your body than a geomagnetic storm with much lower frequencies.
- However, a fridge magnet has alternating N/S poles (a Halbach array)
- One side has almost no magnetic field - no damage to humans
- On the other side, there is a much stronger field, but the alternating poles means that the field rapidly drops to zero with distance; it would not penetrate more than a couple of millimeters under your skin. Not enough to damage nerves, heart, or other muscles.
https://en.wikipedia.org/wiki/Refrigerator_magnet#Halbach_array_polarization

If humans had some subtle sensitivity to magnetic fields (as pigeons are believed to possess), then perhaps humans may be disturbed by a subconscious sense of vertigo, when the magnetic field changes orientation slightly?

There is an economic term "sunspot": It implies a correlation between sunspots (and implicitly solar storms) and economic activity.
- Despite multiple people searching for such a correlation, they have (so far) turned out to be spurious when examined with more data
- With several satellites watching the Sun continually, perhaps now we can get a better correlation between solar activity and sudden death - or will it also turn out to be a spurious correlation?
https://en.wikipedia.org/wiki/Sunspots_(economics)#Origin_of_terminology

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Question of the Week / Re: QOTW - 23-12-16: How do you trigger nuclear Armageddon in Jupiter?

« on: 09/12/2023 21:06:25 »

Jupiter's core is thought to have a temperature of about 20,000C, hotter than the surface of the Sun - so pretty much an Armageddon scenario already.
- This is believed to be a high temperature left over from the gravity of its formation
https://en.wikipedia.org/wiki/Jupiter#Physical_characteristics

But to make it a nuclear Armageddon, you would need to increase its mass by a factor of around 13.
This greatly increases the temperature & pressure in its core, producing conditions which start nuclear fusion of Deuterium in its core.
- This would turn it in to a brown dwarf star - too dim to see with visible light, but glowing more strongly in the infra-red spectrum
https://en.wikipedia.org/wiki/Brown_dwarf

If and when humans ever visit the vicinity of Jupiter:
- It is too long a journey to make with chemical rockets, so it would likely require nuclear rockets
- it is a bit too far from the Sun to generate sufficient energy by solar power, so it is likely that they would use nuclear power.
- Hopefully, by then it would be nuclear fusion, rather than nuclear fission...
- It is possible that humans would take their petty squabbles with them (so far from their origin), and that could result in a  nuclear Armageddon amongst the moons of Jupiter...
- The gravity of Jupiter is too high (2.5 times Earth gravity) that unmodified humans are unlikely to live there for very long, but robotic mining of the atmosphere is possible (eg extracting Helium-3 or Deuterium to fuel the nuclear rockets).
- Recovered elements would need to be exported using nuclear rockets. A squabble over mining operations could easily go nuclear!

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Question of the Week / QOTW - 23-12-16: How do you trigger nuclear Armageddon in Jupiter?

« on: 09/12/2023 20:42:36 »

...from one of our younger listeners...

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Physiology & Medicine / Re: Are there any naturally occurring proteins not encoded in DNA?

« on: 08/12/2023 19:49:46 »

From another viewpoint:
- Amino Acids are the building blocks of proteins.
- As a chemical family, there are a large number of amino acids
- But living creatures on Earth only use 21 amino acids out of this large family

So you could imagine large numbers of proteins in hypothetical living creatures on other planets
- Containing amino acids which are not coded by human DNA...

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Physics, Astronomy & Cosmology / Re: Why do the Earth's satellites orbit longer than the Moon's?

« on: 08/12/2023 19:36:52 »

Why do artificial satellites of the Earth rotate by inertia longer than artificial satellites of the Moon?

I agree that satellites orbit because they have inertia and a velocity relative to the parent body, which gives them angular momentum.

From a different viewpoint...
The Earth is surrounded by an atmosphere which extends beyond 100km (getting less dense the farther you go)
- This means that satellites in Low Earth Orbit (LEO) continually lose angular momentum, and their orbit decays
- The International Space Station at around 400km altitude would eventually burn up in the atmosphere if it did not get regular rocket boosts
- In contrast, the Moon has no atmosphere - any transient events like meteor impacts just result in a slightly less dense vacuum in the vicinity of the impact.
- So I expect that an artificial satellite at 150km altitude above the Moon would remain in orbit much longer than an artificial satellite at 150km above the Earth.

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Question of the Week / Re: QotW - 23.12.08 What are black holes made of?

« on: 08/12/2023 19:27:16 »

does a Single Photon start to get Stretched?

If you have a dense object like a neutron star or a white dwarf star, and fire a photon (or a laser beam) with a known wavelength outwards, someone at a great distance would measure it with a longer wavelength than when it was emitted.
- You could say "The photon wavelength was stretched"
- This is sometimes called "Einstein shift", since it was predicted by Einstein
- This was observed in 1954 with a white dwarf star

If you have a less dense object like the Earth, this gravitational redshift is much less
- However, it was measured in the 1959 Pound?Rebka experiment, using gamma rays

For black holes, photons released within the event horizon will never be seen outside it
- However, if you emitted a laser beam of known wavelength at (say) 10x the radius of the event horizon, a distant observer would see it significantly red-shifted
- However, if you emitted the laser beam at (say) 5x the radius of the event horizon, a distant observer would see it even more red-shifted
- So you could say "as you approach the event horizon of a black hole, a Single Photon (or laser beam) starts to get Stretched"...

See: https://en.wikipedia.org/wiki/Gravitational_redshift#Astronomical_observations

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Question of the Week / Re: QotW - 23.12.08 What are black holes made of?

« on: 03/12/2023 20:14:13 »

Mass and/or energy (any kind): but concentrated into such a small radius that the escape velocity exceeds the speed of light.

The most common way that black holes form today is when a massive star (>10 times the mass of the Sun) explodes as a supernova. The remnant left behind will be a black hole.

Less massive stars can form a dense neutron star; if two neutron stars later collide, they could also turn into a black hole.

The James Webb Space Telescope has revealed large active galaxies, soon after the Big Bang. These are believed to have supermassive black holes at the centre. Theoreticians are inventing new mechanisms that would allow these supermassive black holes to form in the hot, dense early universe, without first forming stars.

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COVID-19 / Re: What is "long covid" and what different types are there?

« on: 28/11/2023 09:39:29 »

Chronic Fatigue Syndrome is a well-known condition that can last for months after an infection of mononucleosis or some viruses.
- The causes are not well understood
- Some COVID patients seem to suffer something similar.
https://en.wikipedia.org/wiki/Chronic_fatigue_syndrome

COVID attacks cells via the ACE2 receptor on their surface. This receptor is involved in regulating blood pressure.
- This receptor appears on many cell types including lungs (the normal route of infection), lining of blood vessels, kidneys, and nerve-supporting cells.
- Loss of nerve-supporting cells can kill nerve cells, resulting in COVID's most distinctive symptom: Loss of taste and smell.
- If this spreads into the brain, it could be responsible for the death of brain cells - a study of patient MRIs before and after COVID showed a reduction in brain volume (faster than normal shrinkage). This could be responsible for the "brain fog" symptom which is often reported by long COVID sufferers.
- Since every organ depends on a flow of oxygen and glucose, inflammation of the blood vessels (and resulting blood clots) could damage every organ in the body (depending on where the blood clots occur), resulting in a wide array of medical conditions.

Probably, Long COVID symptoms will eventually be grouped into 5 or more clusters of symptoms - where one person may be suffering from 1 or more of these clusters.
https://en.wikipedia.org/wiki/Long_COVID

(Overlap with Paul)

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Plant Sciences, Zoology & Evolution / Re: Can Animals Appreciate Beauty ?

« on: 15/11/2023 20:34:20 »

Humans are very visually-oriented.

Other animals rely more on other senses.

I can imagine a dog appreciating a beautiful scent that would be lost on a human.

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Physics, Astronomy & Cosmology / Re: Are All The Planets Moving Away From The Sun Due To Sun Losing Mass ?

« on: 15/11/2023 09:13:18 »

In about 500 million-1 billion years (please correct  if inaccurate)

The estimate from Wikipedia is that the Sun will turn into a Red Giant in about 5 billion years.
https://en.wikipedia.org/wiki/Red_giant#The_Sun_as_a_red_giant

Either way, I will be gone by then...

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Physiology & Medicine / Re: How Does The Placebo Effect Work ?

« on: 14/11/2023 20:32:05 »

The mind does have considerable control over your body, and how you feel about your body (eg pain sensitivity).
- So telling your mind that someone you trust has prescribed this medication will probably make you feel better, even if it does nothing for an underlying biological problem.
- We saw this during the COVID pandemic, where a significant fraction of the US population believed that Ivermectin had protected them from COVID and/or cured them - because Donald Trump told them (with no clinical evidence at all, initially).

That's why the gold standard for clinical trials is to test a proposed medication/treatment against an identical-looking placebo.
- That tells you (and anyone funding your health) that paying for this medication is better than doing nothing (for free).
- Often, the placebo effect is bigger than the effect of the proposed medication! But the small effect of the medication is visible because you can "subtract out" the placebo effect.
- However, large studies have shown that Ivermectin is no better than placebo at treating COVID (with the possible exception of trials in some 2/3 world countries, where the proven de-worming effect of Ivermectin may have reduced the known immune-suppressing effects of parasitic worms, allowing a more robust immune response to COVID).

I have heard of a 2010 study that demonstrated that the placebo effect really makes people feel better, even if they know they are taking an inert substance!.
See: https://en.wikipedia.org/wiki/Placebo#Mechanisms

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New Theories / Re: How Jupiter magnetic fields is created?

« on: 11/11/2023 21:34:53 »

Re "there are at least two magnetic dipoles": The correct term is "quadrupole". 2, 4, 6, 8 or more poles are also possible.

Re "1. random activities as swirling mass of hydrogen deep within the planet": Chaotic motion of conducting fluids has been observed in the lab to create a magnetic field, which also has chaotic characteristics (including periods of oscillation).
https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.98.044502

The Earth's magnetic field is currently mainly a dipole, but during magnetic field reversals, it may pass through a quadrupole (or higher-order) phase.

Hydrogen's position on the periodic table places it near the metallic elements. There have been multiple experiments showing that hydrogen becomes metallic at very high pressures (such as occur in the centre of Jupiter).
https://en.wikipedia.org/wiki/Metallic_hydrogen#Experimental_pursuit

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Question of the Week / Re: QotW - 23.11.17 Why can't things travel faster than light?

« on: 11/11/2023 00:09:44 »

As Paul says, you can't accelerate an object to the speed of light (or beyond) using a finite amount of energy.

With Dark Energy, it is spacetime itself which is expanding. There is no known limit to how fast space-time can expand.
- So some distant objects which are visible to us today (relative speed < speed of light) will one GigaYear not be visible to us (relative speed > speed of light), and no photons will reach us from those objects.

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Technology / Re: Why Don't Smartphones Have Antennae?

« on: 10/11/2023 23:50:14 »

If you have an old 4G iPhone like mine, there is a metallic pattern in the case, visible from the outside, with gaps in-between. Mine has:
- One metal stripe along the top (above where you hold it)
- One metal stripe along the bottom (below where you hold it)
- A large metal area across the back and sides (where you hold it)
- These metal stripes (antennas) are linked to internal circuitry, which can pick up signals from 2 antennas (or, in more recent models, more than 2 antennas), for transmission and reception.

When the original iPhone was introduced, reception was horrible. It turns out that your hand covered the antennas, attenuating the signals.
- People complained that it was a design flaw, and wanted their money back
- Apple retorted that people were holding it all wrong
- But when you look at the Apple iPhone ads, all the advertising models were holding it wrong, too.

Lesson: Don't just test it in a lab, test it in the real world, too!

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Chemistry / Re: What acid mixture can dissolve plastic

« on: 10/11/2023 23:37:43 »

The best way to soften plastics, and then later have them harden again is to melt them.
- Mild heat leaves the polymer chains intact, but temporarily mobilises them.
- Only works for thermoplastics...

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That CAN'T be true! / Re: What is "four times less"?

« on: 02/11/2023 20:43:35 »

I think it is shorthand for "one quarter of"
- But understandable by people who are comfortable with the counting numbers, but uncomfortable with fractions...

I suspect that the quantity that is reduced to a quarter is the mechanical energy of scrubbing - perhaps this new product chemically reacts or dissolves the dirt, much better than (say) water.

It is possible that "one quarter of the energy expended in scrubbing" translates into "one quarter of the time spent scrubbing"
- However, I am sure that it does not mean that it removes dirt, three-quarters of which has not yet been generated

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Plant Sciences, Zoology & Evolution / Re: Can an arctic polar bear survive in Antartica?

« on: 30/10/2023 05:59:11 »

One won't survive very long.
But two or more have a chance of severely depleting the penguin and seal population...

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Technology / Re: Why is my sattellite receiver behaving oddly?

« on: 30/10/2023 05:54:54 »

Perhaps your satellite receiver had been preconfigured to use certain transponders?
- If a channel was shuffled to a different transponder, it would no longer be found.
- The blind scan checks all the transponders it can find.

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Physics, Astronomy & Cosmology / Re: Why isn't my salt water evaporating?

« on: 15/09/2023 09:09:02 »

May be hygroscopic salts in there - they absorb moisture from the atmosphere (which BC was alluding to).
https://en.wikipedia.org/wiki/Hygroscopy

In extreme cases, this becomes "deliquescence" - these compounds absorb water from the atmosphere, and dissolve in the extracted water.
https://en.wikipedia.org/wiki/Hygroscopy#Deliquescence

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Physics, Astronomy & Cosmology / Re: Does helium make all sounds higher pitched?

« on: 06/09/2023 22:10:18 »

a plastic saxophone

Some researchers are 3D-printing plastic violins. They model the structure on computers, so the sound is very much like a professional wood violin.

Unfortunately, you can't use a 3D-printer to turn  yourself into a professional violin player!
https://www.sciencefriday.com/segments/3d-printed-violin-song/