1

Physics, Astronomy & Cosmology / Re: How long could humanity survive if the sun went out?

« on: 16/04/2021 09:26:51 »

if the sun went out?

Are you implying that it goes out with a bang or a whimper?

If it went out with a bang (supernova), even a nuclear submarine would not protect you - the oceans would boil (and the prompt neutrinos would get you too).
- Fortunately, with what we know, the Sun will not go out with a bang

If the Sun  goes out with a whimper (eg red giant, then white dwarf), we will have plenty of warning to go elsewhere before the oceans boil dry (billions of years - assuming we last the next 1,000 years!).

If the Sun gets snatched away from us (eg nearby passage of a stellar-mass black hole flinging us out of the Solar System), the earthquakes would destroy most things on land, but the nuclear submarine option might keep you going for a few months...

This is the way the world ends
This is the way the world ends
This is the way the world ends
Not with a bang but a whimper.

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General Science / Re: Does ginger help with travel sickness?

« on: 08/04/2021 10:51:44 »

Travel sickness is as much in the mind, eyes and ears as it is in the gut.
- The placebo effect has a powerful impact on the mind
- So almost anything can improve travel sickness, if you believe it will.
See: https://en.wikipedia.org/wiki/Placebo

Dealing with the eyes, I know people who get carsick in the rear seat, but not in the front seat.
- In the front seat, they can see the road ahead, and expect the turns coming up.
- And it's also a matter of control - if they are controlling the steering wheel, they don't feel carsick

Another technique, available to military pilots: Turn up the oxygen to 100%.

When preparing for an ocean trip, we were advised: We have seasick tablets - we have herbal tablets, and we have the ones that work!
- But it's best to take them an hour or so before you start the trip..

3

General Science / Re: What are your opinions of Yuri Gagarin, first cosmonaut?

« on: 07/04/2021 21:44:39 »

do you really believe in a cold war the respective governments would spend such ammounts (on Moon landings) rather than having an extra 1000 planes 5000 tanks and 100000 troops.

The Cold War was a psychological war, as much as anything.
- The enemy's population can't see an extra 5,000 tanks, but the periodic beeping transmission of Sputnik 1 circling over the USA caused a severe psychological shock in the US public.
- Sputnik 1 also caused a shock to the US military. They knew that a rocket which could deliver a small payload into a circular orbit was capable of delivering a much larger payload to any destination on Earth.
- There was little military advantage to having a rocket that was large enough to deliver astronauts to the Moon. It is impossible to hide, takes a long time to fuel, and is very exposed. But it had massive psychological power (what do they say about small politicians and big rockets?...)
- Because the Cold War was about convincing your population that they were socially, politically and technologically superior to the the "other side".

things might have gone differently if the Soviets had succeeded in landing on the Moon.

That is the premise of a TV series called "For All Mankind", which assumes that:
1) The Russians beat the USA to the Moon by a couple of weeks
2) The Space Race never stopped.

They have tried to make the costumes and the sets realistic for the time, and include relevant news broadcasts from the era.
I am watching it on Apple TV, but it may be available on various platforms in different countries...

See: https://en.wikipedia.org/wiki/For_All_Mankind_(TV_series)

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Cells, Microbes & Viruses / Re: Affordable microscope?

« on: 05/04/2021 22:15:15 »

These days, you can get quite cheap and portable microscope attachments which:
- Clip onto the camera of your mobile phone, to provide an optical close-up lens
- Plug into the USB port of your computer. These sometimes have built-in illumination of the subject
- Both of these allow you to take photos and videos, without an expensive camera attachment required by "traditional" desktop microscopes.

Holding the device steady, at the right distance from the subject is a real challenge. Look for one with a built-in spacer (which doesn't block the light).

5

Physics, Astronomy & Cosmology / Re: Is time travel possible?

« on: 05/04/2021 11:47:57 »

Is time travel possible?

Yes, of course it's possible! I do it all the time.

At present, I am traveling into the future at 1 second per second.

If I had a tame black hole, or a fusion rocket, I could travel into the future a bit slower.
- If it were possible for me to get out of the local galaxy cluster, I could travel into the future slightly faster (relative to someone on Earth)

The challenge is to travel anything but 1 second per second into the future!

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COVID-19 / Re: How many Oxford vaccine trial volunteers were in the placebo group?

« on: 04/04/2021 22:53:42 »

How many Oxford vaccine trial volunteers were in the placebo group?

As I understand it, the usual practice is to have a 50:50 split of "treatment" (the real medicine) and "placebo" (imitation medicine).

The Astra-Zeneca trial was conducted in several countries, and the trials varied in:
- The incidence of COVID-19 varied over time, and between countries
- Dosing (the UK trial accidentally had half-strength for the initial dose)
- Age (the UK trial tended to have younger participants)
- Delay between doses (the UK trial was put on hold, so some of the participants received their second doses a lot later than the planned 3 weeks gap)
- The later trial in Africa was small in size, and faced several new variants.

So, even if you had the raw number of how many people in the placebo arm went to hospital, you would still need to untangle all the other variables.

7

Guest Book / Re: Mods...May i have a lil of your Attention, Please?

« on: 04/04/2021 10:02:36 »

I recognize one of those usernames - a blatant attempt to advertise.
- If I see someone posting a blatant advertisement in their first post, I delete the post and permanently ban the username. These people have no intention of following the forum rules.
- If I see someone posting an ad after making a few useful contributions, I send them a warning. Repeated infractions following a pattern result in a ban.
- I notice some other moderators ban the user, but leave the post there, just rewording it so that the advertised organization is turned into "spam".
- Sometimes I have to change the username to remove the advertisement (mods have the power to rename a user). So the post may remain, but the username is gone.

8

Physics, Astronomy & Cosmology / Re: What causes nuclear power plant meltdowns?

« on: 03/04/2021 23:07:01 »

to shut down the fusion-station, you'd cut off the current by simply pulling out the plug.

It has been argued that controlled nuclear fusion (if/when we ever get it to work) would be safer than fission reactors.
- Partly because the amount of fuel in a fusion reactor at any one time might be 1 gram, rather than 700 tons for a fission reactor.
- But the fuel in a fusion reactor is incredibly hot, and with an uncontrolled shutdown could burn a hole in the wall, requiring tricky repairs before the reactor could be restarted
- most fusion reactor designs use Deuterium+Tritium fuel; this reaction does produce high-energy neutrons, and the walls would become radioactive

an ultra-fast unstoppable chain-reaction which spreads in microseconds through the whole pile of Uranium

As you correctly suggest, this is a description of a fission bomb.

simmering and festering in a slower but lethal radiation-emitting "melt-down"

Unlike your implication, in a fission power reactor:
- The chain reaction is stoppable, using control rods
- A melt-down is not inevitable, provided the fuel temperature is kept below the design limits

Fortunately, most nuclear power reactors are operated properly, most of the time.
- It's the exceptions that produce headlines and exclusion zones...

9

Geek Speak / Re: In simple terms, for idiots, what are bitcoins?

« on: 02/04/2021 09:41:57 »

Isn't promoting BitCoin, indirectly promoting Illegal & Unlawful activities?🤔

Some governments view it that way, and ban Bitcoins (if they can find them).
- I would say that criminals promote untraceable transactions, which is why they always like cash. Does governments printing cash promote Illegal & Unlawful activities?
- Bitcoin promotes speculation, and in most countries, speculation on currency, the stock market and/or horse races is legal.

Are BitCoins more Trustworthy & Stable in comparison to the USD?🤔

No.
- The US Federal Reserve will take some actions to protect the $US from volatility.
- No-one will protect you from Bitcoin volatility.

What If the BitCoin bubble pops out overnight...will the Governments of the World protect & safeguard & repay for the Economical & Financial Loss of their Citizens?

As above, Bitcoin promotes speculation, and no-one will protect you from Bitcoin volatility.

10

Physics, Astronomy & Cosmology / Re: What causes nuclear power plant meltdowns?

« on: 01/04/2021 22:13:55 »

The human error in the case of Fukushima...

There were a few errors that contributed to this...
- No big earthquakes had been recorded in this area for hundreds of years, so obviously, no more would occur for hundreds of years (the opposite is true; when a fault-line is "stuck" for hundreds of years, it is building up pressure for a really big one!)
- Ignoring geologists who pointed to sediments well inland, suggesting that there were very big earthquakes in this region, hundreds of years ago.
- Locating the emergency generators in the basement (where they got flooded), instead of on higher floors (where they could have provided power to keep the coolant circulating in the reactor core).

Isn't 20/20 hindsight wonderful!

In the end, around 16,000 people were killed by the Earthquake and Tsunami.
- It is estimated that less than 10 people may be killed by the reactor meltdown - and these deaths will occur over the next 40 years.
See: https://en.wikipedia.org/wiki/2011_T%C5%8Dhoku_earthquake_and_tsunami

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Geology, Palaeontology & Archaeology / Re: What rules does the energy released from an earthquake follow?

« on: 31/03/2021 10:47:04 »

Does the energy released from an earthquake follow the Inverse Square Rule

The Inverse Square Rule applies to energy radiated equally in all directions in a 3-dimesnional volume, from a point source.

Most Earthquakes consist of a slip along a fault line, so the source is 2-dimensional, rather than a point.
- And the earthquake waves don't radiate equally in all directions.
- But if the Earthquake is far away (so it looks like a point from where you are), the strength of the earthquake shock does reduce with distance.

There are some special cases:
- If your home is built on loose and/or wet sediment, this can accentuate shaking and cause more damage to buildings, or liquify and swallow buildings.
- If you are located diametrically opposite the earthquake location on the Earth, the liquid core absorbs the "sideways" earthquake waves, leaving a bit of a shadow on the other side.
- Much of the damage from Earthquakes comes from Tsunamis. Because the ocean is a thin 2-dimensional skin on the Earth, the Earthquake energy spreads out like 1/distance, not like 1/distance². This means that tsunamis can spread disaster further than the earthquake waves.

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Physics, Astronomy & Cosmology / Re: Do Certain Astronomical Phenomenons Affect US?

« on: 31/03/2021 10:32:01 »

the Effects of the Moon on Mentally Unstable Individuals.

This is the origin of the word "Lunatic" = "person made mad by the Moon (Luna)"

In traditional societies (no artificial lights indoors, no outside street lighting), a full or near-full Moon allows more outdoor activities after sunset.
- If someone were marginally sleep-deprived, a few hours of extra activity by Moonlight might push them into severe sleep deprivation, and perhaps bizarre behavior (if they had a predisposition).

But in modern societies, with indoor lighting at the click of a switch, and brightly-lit cities, the Moon is almost lost in the glare.
- We have cities that are open 24 hours per day, and streaming media sites with 10000 hours of content every day.
- Many people are chronically sleep-deprived
- So I think that there may be many lunatics in our cities, and not just on a full Moon!

For some history and etymology of Lunatic, listen (16 minutes):
https://www.wnycstudios.org/podcasts/science-diction/articles/lunacy-mind-control-from-the-sky

13

Physiology & Medicine / Re: How much use is pulse oximetry?

« on: 29/03/2021 21:27:37 »

When I was looking at the pulse oximetry devices available on display, I saw another device which did pulse oximetry, but also claimed to be able to detect atherosclerosis.
- The implication on the box was that it analyzed the pattern of the pulse of blood reaching your finger to determine the stiffness of the arteries between the heart and finger.
- The aorta acts as a shock absorber between the heart and the rest of the circulatory system
- Furring of the arteries in your arm would conceivably change the waveform too.

But because it was almost 4 times the price, I didn't bother with this one.

14

Physiology & Medicine / Re: How much use is pulse oximetry?

« on: 29/03/2021 10:57:30 »

Is it giving consistent readings?

I've only tried it on myself 3 times in a day, and got a range of 95-98%.

This averages in the recommended range - nothing to worry about!

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COVID-19 / Re: How is vaccine effectiveness calculated?

« on: 27/03/2021 10:24:14 »

his is called 90% effective

Clinical trials are designed to measure "efficacy": The chance that it does what it claims, under ideal conditions.

Once rollout starts, conditions are not so ideal. The chance that it does what it claims, under normal conditions is called effectiveness.

Similar concepts, similar words, but measured under somewhat different conditions.

But if it had been 50:50, that would not be 50% effective, it would be 0% effective.

Yes, that is correct.

It is also possible for the treatment arm in a Clinical Trial to be affected more severely than the patients in the placebo arm.
- When such conditions occur, the oversight committee recommends premature termination of the trial, to prevent more illness in the treatment arm.
- But such actions are only taken after enough adverse events are recorded - enough to give (say) 95% confidence that the new treatment is worse than no treatment (or the previous best treatment).

if the vaccine test on a large group results in 90% of the entire number of those contracting the virus being in the half that have not received the vaccine, this is called 90% effective

The number of adverse outcomes in each arm of the trial can almost be quoted from the raw figures in the trial
- If 90% of adverse outcomes were in the placebo arm, that is a good endorsement of a medication.

However, there is a bit of statistical manipulation of the figures before they quote an efficacy figure.
- Perhaps after some medical analysis and discussion about whether these adverse events were caused by the medication or external factors.
- Eg if there were 2 deaths in the treatment arm, and one was caused by getting hit by a truck, the manufacturer might argue that this was not caused by the medicine... Eliminating this patient from the count would make a big difference to their efficacy score!

A large clinical trial might cost $100 million.
- This is why pharmaceutical companies and regulators employ professional statisticians when designing and interpreting the results of clinical trials
- So they can obtain meaningful results from the trial (the "power" of the trial)
- And can estimate the probability that the result was obtained by mere chance
- Often, the conclusions would be stated as Efficacy=92% (with a range of 85% to 97% at p=.05)
- Where the p=0.05 says there is a 5% chance that the result might be outside this stated range.
- If you want a more accurate result (smaller range of uncertainty) you need more patients, it will cost more money and take longer to gain approval

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

But beware:

There are three kinds of lies: lies, damned lies, and statistics.

In the past, pharmaceutical companies have been accused of withholding publication of unfavorable results.
- That is harder to do in a pandemic, where the WHO maintains a list of all clinical trials, and everyone is looking for the results of every trial!
- Ideally, clinical trial results would be published in a peer-reviewed journal with all of the statistical details present and visible to readers. Some of the vaccine manufacturers have been accused of publishing results via press releases which are utterly devoid of the statistical facts behind them. Some of this behavior may be driven by stock-exchange rules?
- Astra-Zeneca has been accused of "marketing spin" in combining the results of several vaccine trials in ways that are not statistically rigorous.

16

COVID-19 / Re: Does protein S deficiency put you at risk of severe COVID?

« on: 27/03/2021 09:40:47 »

protein S deficiency

This is a human protein that is involved in regulating the clotting process.
- There are a number of ways it could have low levels, including genetic causes or developing an auto-immune condition where antibodies attack it and disable it.

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

new vaccine from Pfizer and others on trial work by modifying (attacking) the S protein of the Covid 19 virus.

These are independent uses of the letter "S".
- In this case, "S" stands for SARS-COV2 "Spike" protein: the part of the virus that allows it to enter cells.
- By disabling the S protein, the virus can't infect cells, and protects the vaccinated person against COVID-19 disease.

Do these 'S' proteins have anything to do with one another?

Recently, several countries put the Astra-Zeneca vaccine on hold, while trying to track down cases of cerebral (brain) thrombosis (clots).
- The conclusion was that the vaccine did not increase the rate of clotting in the general population (in fact, it reduced it, compared to non-vaccinated people).
- COVID-19 is known to cause abnormal clotting in some people
- The conclusion was that it is safer to vaccinate people than to let them catch COVID-19

Researchers are still monitoring a small group of people who may be more susceptible than the general population - mainly women under 55 who already have low platelet levels - a condition similar to heparin-induced thrombocytopenia
- A small study in preprint suggested that these events can cause headaches starting around 4 days after vaccination (by which time the symptoms on day 1 & 2 have dissipated). Treatment with an anticlotting agent is recommended (but not heparin or warfarin - others are available).
See: https://en.wikipedia.org/wiki/Heparin-induced_thrombocytopenia

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Physics, Astronomy & Cosmology / Re: Do Certain Astronomical Phenomenons Affect US?

« on: 27/03/2021 00:46:21 »

Does the Water in the glass or inside off of Us Rise??? (Does it Rise even like a say 0.001%)

The tidal effect of the Moon on Earth's surface gravity is around 1 in 10⁷. The Sun's effect is about half as big.

If you are standing on a set of bathroom scales (which is calibrated to measure force):
- They aren't sensitive enough to measure a change in force of 1 part in 10⁷. But even if they were sensitive enough...
- If I read the equations correctly (see link below), the tidal force on Earth's surface is proportional to GΔr/R³
      - Where R is the distance between the centers of Moon and Earth (for example), or 384,000 km
      - And Δr is how far you are from the center of the Earth (ie the Earth's radius, if you are standing on the ground, or 6370km)
      - G is Newton's Gravitational Constant

But the set of scales is attracted to the Moon by the same tidal forces as you are.
- If you are standing on scales, what matters is the change in tidal force between the center of the scales and the center of you (let's say this difference in height is 1 meter)
      - Let's say Δr_s is the distance of the center of the scales from the center of the Earth, or 6370km
      - Let's say Δr_h is the distance of the center of the human from the center of the Earth, or 6370.001km
      - The difference between these is G(Δr_s - Δr_h)/R³
      - Or about 1 part in 15 million of the normal gravitational acceleration due to the Moon, or about 10^-13 of Earth's surface gravity.

When you look at a cup full of water, the center of the water is about the same distance from the center of the Earth as the center of the cup. So the Tidal force on both are equal, and the water in the cup does not rise at all, relative to the cup.

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

18

Physiology & Medicine / Re: How much use is pulse oximetry?

« on: 27/03/2021 00:09:17 »

The breathing reflex is prompted by a rise of carbon dioxide levels in the blood.
- That's why nitrogen asphyxiation is so dangerous, as it doesn't lead to increase in carbon dioxide in the blood.

You don't want to breathe too deeply for too long. Hyperventilation can cause dizziness, loss of vision and fainting.
It's also hard work, so your body does not naturally breathe too much.
See: https://en.wikipedia.org/wiki/Hyperventilation

Scarring of lung tissue due to COVID-19 infection reduces oxygen flow across the alveoli, and reduces blood oxygen levels.
- But because this scarring occurs gradually over a period of days to weeks, your body adapts to the reduced oxygen levels, and you may not notice it around the house
- You are more likely to notice it if you exercise; normal levels of exercise may leave you unusually breathless
- A pulse oximeter will pick up the reduced oxygen levels, even if you don't feel breathless
- This slow adaptation to reduced oxygen is similar to the process when mountain climbers spend a week or two at Everest base camp to acclimatize

With an average SpO2 of 93%, it sounds like you should mention it to your doctor, next time you visit.
- It SpO2 stays consistently below 92% (but you still feel ok), make an immediate medical appointment - a chest X-Ray will reveal if you have the "ground glass" pattern indicative of COVID scarring, or other respiratory problems.
See: https://en.wikipedia.org/wiki/Ground-glass_opacity

19

Physics, Astronomy & Cosmology / Re: Centre of the universe?

« on: 24/03/2021 09:46:14 »

any stars that are 13.8 billion light years away from us won't have anything beyond them will they?

The 13.8 billion light years is an extrapolation. We can't actually see any individual stars (or individual galaxies) at that distance.
- With current technology, we can spot individual quasars (active galaxies) out to around 13.4 billion light years.
https://en.wikipedia.org/wiki/List_of_the_most_distant_astronomical_objects

Let's just back off to a galaxy that is 13 billion light years away.
- If any astronomer looks through a big telescope, they will be looking backwards in time.
- If an astronomer over there looks in our direction, they will see some old galaxies (one of which may have eventually merged into our Milky Way galaxy)
- If they then turn their telescope in the opposite direction, they will also see galaxies in that direction, too, out to around 13 billion light years
- We cannot see those galaxies from here, but someone suitably positioned can see them.

There is a reason we can't see all the way back to the Big Bang, and that is because the early universe was filled with ionized gas (plasma), which blocks electromagnetic radiation. We see the remnants of this glow (red-shifted by a factor of over 1,000) as the Cosmic Microwave Background Radiation, which comes from all over the sky.
https://en.wikipedia.org/wiki/Cosmic_microwave_background

20

Physics, Astronomy & Cosmology / Re: Where did all the suns hydrogen come from?

« on: 24/03/2021 09:28:55 »

if all the hydrogen was consumed (during a star's lifetime) where did the hydrogen that makes up our sun come from?

A lot of hydrogen exists in intergalactic space, and rains down onto the galaxy, fueling new star formation.

But even during their lifetimes, stars produce a continuous wind from from their outer surface, carrying some of their hydrogen back into space. For the Sun, this is called the Solar Wind.
- When a star gets old, and turns into a red giant, and large amounts of the star's outer atmosphere drift off into space.

stars become loaded with other elements that inhibit nuclear fusion.

The Sun is too small to go past the Helium-burning phase of a red giant.
- But larger stars go through successive stages of burning larger and larger atoms (which require sucessively higher and higher temperatures, due to the larger electrostatic repulsion between larger nuclei)
- The limit is when the core is mostly iron and nickel. No energy is gained by fusing these nuclei - in fact it consumes energy to fuse iron nuclei, resulting in a catastrophic collapse into a black hole. During this process, some of the star's outer envelope is blown off into space, including nuclei up to nickel (and a little beyond).

(the Sun's parent star) must have been many times the size of our sun in order to create the heavy elements such as Gold, Lead, Uranium.

It is now thought that most of these heavy elements are not created in supernovas, but in neutron star mergers, which spray large amounts of neutron-rich material into space (before collapsing into a black hole).

See the periodic table, showing the expected sources of different elements:
https://en.wikipedia.org/wiki/Stellar_nucleosynthesis#Key_reactions

Our sun is a second or third generation star,

Ironically, stars like the Sun were the first type of star discovered. Stars like the Sun are called "Population I stars"
- A later discovery of stars with much lower concentrations of "metals" (elements heavier than helium) were called "Population II stars"
- It is assumed that there was an even earlier group of stars with almost no elements heavier than helium. This hypothetical group is called "Population III stars"

So in fact, astronomers named the stars in exactly the opposite order than you might expect.
See: https://en.wikipedia.org/wiki/Stellar_population