1

Geology, Palaeontology & Archaeology / Re: Are there mountains/mountain ranges that existed, but no longer do?

« on: 10/06/2021 05:25:24 »

Yes. Look for any areas with granite.

Granite is thought to form as crustal rocks melted and slowly cooled, deep beneath mountain ranges.
- If granite is now on the surface, then the mountain range has eroded away.
See: https://en.wikipedia.org/wiki/Granite#Origin

2

Geek Speak / Re: What is the power of regression?

« on: 09/06/2021 23:27:56 »

Couldn't the evidence in a graph, be presented in "digital" format, ie as just tables of numbers? Is it because graphs make it easier to see the underlying mathematical processes.

Yes, humans are a very visual species.
- We have the unusual visual quirk that we can see things that don't change, which makes the whole "reading a book" possible.
- As I understand it, for most species, things that don't change do not generate an image.

Graphs work well in 2D.
- They can be extended to 3D on a page for some sets of data
- but I think 3D data would be explored more easily with virtual reality headsets
- I have seen one presentation (as a movie) that worked through data in more than 3 dimensions (I think  it may have been 8 dimensions?). But that was geometrical data, so it was (sort of) possible to see geometrical patterns emerge as the view switched between hyperplanes. I don't this would work nearly so well for data that was noisy in multiple dimensions, as you would only see part of the pattern and part of the noise.

The one I saw was a bit more colorful than this one:

As BC said, regression can find patterns in multi-dimensional data that we wouldn't be able to visualise.

3

Physics, Astronomy & Cosmology / Re: TV documentary about Arthur C. Clarke

« on: 08/06/2021 08:57:25 »

Arthur Clarke wasn't the first.

Alexander Graham Bell's lab produced one in 1880, the photophone:
https://en.wikipedia.org/wiki/Photophone

4

Physics, Astronomy & Cosmology / Re: What is a singularity?

« on: 06/06/2021 11:18:58 »

I don't think anybody steals anything; all of us borrow

A somewhat more metaphorical borrowing of "singularity" is in discussing Artificial Intelligence.

This is the hypothesis that AI systems could one day be smart enough to (successfully) reprogram themselves to make themselves "smarter". Then the smarter AI could work out how to make itself even smarter, leading to a runaway explosion of AI capabilities that humans could not possibly understand or control. This comes with the fear that such an AI may wipe out humans without a thought, just like a human might step on an ant without even noticing it.

We today are becoming more familiar with exponential growth in semiconductor chips and pandemics.
- But a true singularity grows far faster than exponential growth - a singularity reaches infinity in a finite time; unconstrained exponential growth reaches infinity, but it takes forever to get there...
- There are finite limits to the efficiency of computation, so a computer with a finite power supply can't really reach infinite computation speed
- But it is possible that an AI could become so powerful that we have no way of comprehending or measuring it; so, metaphorically, it may as well be infinite...

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

5

Physics, Astronomy & Cosmology / Re: What is a singularity?

« on: 05/06/2021 09:34:06 »

Singularity defines Infinites of What exactly?

The singularity can be anything - it depends on what you are measuring (and how).

- In simple theories of aerodynamics, air resistance approaches infinity as you approach the speed of sound.
     - So, in these theories, the speed of sound is a singularity
     - In fact, some guns can fire bullets faster than the speed of sound, so scientists knew it was not a true singularity
     - And eventually, they managed to break the speed of sound in a manned rocket
     - And Concorde became a (loss-making) commercial supersonic service, for quite a while

In special relativity, mass, energy and momentum approach infinity as you approach the speed of light.
     - Our most powerful particle accelerators can get to within a smidgeon of the speed of light, and these quantities do seem to approach infinity as you get closer to c
     - So, to the best of our knowledge, this is a true singularity (Einstein scores 100% again)
     - But a singularity we can never reach, even if we had the energy of a whole galaxy to play with

In current theories of quantum gravity, the energy of empty space approaches infinity near the event horizon of a black hole
     - In my simplistic understanding, these theories attempt to model the virtual gravitons around the black hole, typically in 11 dimensions. But gravitons have a (tiny) energy, and a (tiny) equivalent mass; but there are lots of them.
     - When you add up the gravitational effects of all these virtual gravitons, you end up with a patch of empty space that has infinite mass, which doesn't seem intuitive at all.
     - Physicists are convinced that this is not a true singularity, and there must be an improved theory that doesn't suffer from this fatal flaw.
 

6

The Environment / Re: Will there be another ice age?

« on: 04/06/2021 09:58:51 »

One of the drivers of ice ages is the Milankovitch cycle, which describes oscillations within the orbits of the planets, lasting 10,000 - 100,000 years. They suggest that there will probably be another ice age, some time.

But they are not the only factor. The distribution of the continents, and the collapse of ice sheets have been identified as contributing factors to Earth's climate.

Human activities have increased the temperature of the planet to a measurable degree, so we are:
- Accelerating any warming which would have happened anyway
- Slowing any cooling which would have happened anyway

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

7

Technology / Re: Does anyone know the efficiency of electric car acceleration?

« on: 31/05/2021 11:18:20 »

I can't think of any other case where doing exactly what is asked of you is considered cheating.

As I understand it, the standardised test was to check that tailpipe pollutants were below the regulated limits, so people in cities didn't suffer so many lung problems...
- To meet more recent NO_x pollution regulations, some diesel cars inject a urea solution into the exhaust stream to react with pollutants; this is commercially known as AdBlue.
- But its a pain to remember to top up the AdBlue tank
- And injection increases fuel consumption

To reduce AdBlue (and fuel) consumption, Volkswagen software only injected AdBlue while the car was running the standardised test in a virtual city (so it always passed).
- That meant it was pumping out excess pollutants all the time while driving around real cities
- Violating air pollution regulations, and presumably causing asthma and other lung irritation
- As well as fixing the software, there were some heavy fines imposed in various jurisdictions

What was asked was to reduce city air pollution from diesel engines.
- What they did was avoid polluting the standardised virtual city, while continuing to pollute the real cities
- In what way was that doing what was requested?

As I understand, it was only discovered when a university team decided to check tailpipe emissions in real life, not in the standardised test.

See: https://en.wikipedia.org/wiki/Diesel_exhaust_fluid
https://medium.com/swlh/the-lie-of-clean-diesel-f55b75031066

8

Technology / Re: Does anyone know the efficiency of electric car acceleration?

« on: 30/05/2021 22:42:35 »

So the best estimate of useable power at any time is the "max sustained" rating of the motors.

It is well known that electric vehicles have far higher torque at low speeds than fossil engines.
- So quite ordinary electric vehicles can beat a souped-up gas-guzzler across the intersection.
- But that depends on being at the head of the queue at the lights, and being in an unreasonable hurry to get to the end of the next queue

In City driving, more realistic would be the average driver behind a queue of cars at the lights - a few seconds after the lights change to green (and hopefully, before they turn back to red), there will be a gradual acceleration up to maybe 50 km/h (or 30mph), and a gradual deceleration back to stationary at the next queue.
- There is a well-defined "City" driving course used to compare pollutants from different vehicles
- It is so well standardised that Volkswagen infamously programmed their engine control system to recognise it and cheat...

What does the efficiency of acceleration actually mean?

I guess you could say that a certain amount of chemical energy (in a battery or fuel tank) gets turned into a certain amount of kinetic energy in accelerating to a velocity v (say, 50km/h).

But the kinetic energy equation also includes the mass m. What do you use as the mass?
- The mass of a 1 ton vehicle?
- A mass of m=100kg, representing the useful payload: an 80kg human and 20kg representing the week's shopping?
- Some people drive to the café for a coffee. Should the useful payload m = 250g of coffee?

9

Technology / Re: What is Cloud Computing and how does it work?

« on: 27/05/2021 23:10:56 »

What is the difference between private/private clouds compared to just running a standard LAN (local area network) within the company?

There are two distinct items here: The computer servers that make up the "cloud", and the communications network that passes data from where you are to wherever the cloud servers are located.
- The servers typically consist of many general-purpose CPUs =Central Processing Units, with large amounts of RAM=Random Access Memory, coupled with lots of disk space, and connection to a communications network (LAN and/or WAN).
       - The number of computers dedicated to one task can change dynamically, as the workload changes
       - Sometimes specialised processors are available which do things like run Artificial Intelligence models or high-powered number crunching or high-speed encryption.
- A "LAN"=Local Area Network is a communication network within a building. It may have traditional blue Ethernet cables, or, increasingly, use WiFi to connect to your phone or laptop. You use a LAN to reach a local cloud (eg in the same building, run by your company)
- A "WAN"=Wide Area Network is a communication network between buildings. It may have traditional telephone wires, optical fiber, or, increasingly, use 5G mobile to connect to your phone. You use a LAN to get to the edge of your building, and a WAN to reach a public cloud (eg in a Data Center in your city; it might be run by a cloud provider like Amazon or Google)
-Your company can rent space in a public cloud, and let the cloud provider look after the hardware, air conditioning and power supplies. Or it can buy its own hardware for a private cloud.
- But if you need fast responses ("real-time"), you will locate the servers closer to where you are, as there are delays inherent in passing over a LAN or WAN; these delays generally increase with distance.

If you want to get into cloud computing, you should do some general courses on software, and some specialised courses on cloud computing (each cloud computing vendor has their own unique software environment).

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

10

Physics, Astronomy & Cosmology / Re: What is the Quantum Mechanical explanation for the generation of an EM wave?

« on: 27/05/2021 22:30:17 »

Perhaps one way of looking at photon generation is:
- The electron is initially in a higher-energy orbital
- The electron ends up in a lower-energy orbital
- The difference in energy has to go somewhere, which is into a photon
- The energy of the photon is proportional to its frequency by the equation E=hf
- Where E is the Energy
- f is the frequency
- h is Plank's constant

It is only when you have something like a laser, with many in-phase photons that you can say that the electric and magnetic field intensity follows a sine-wave pattern.

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

11

Technology / Re: Fusion still in retreat?

« on: 26/05/2021 10:50:16 »

Fusion is already the primary power source on the planet.
- And it has been since before the first patent was filed on hydrogen fusion.
- Thanks to the Sun

12

COVID-19 / Re: Can we get herd immunity?

« on: 25/05/2021 22:44:50 »

the survivor population as a herd of immunes, i.e. a subspecies with inherent and hertiable immunity or tolerance

When smallpox was introduced to the (previously unexposed) Australian Aborigines, the death rate was reportedly around 90%. The succeeding generations were apparently better able to survive this pathogen.
- That is a high price to pay for a tolerant community
- But it won't work for COVID-19, since most of the fatalities are past childbearing age

The problem is that a human generation is 25-30 years
- while a COVID-19 generation is 1 week, with new mutations spawned every 2 weeks.
- So the virus can always adapt faster than we can

Vaccination is a way to achieve community protection, but without the heavy death toll.

13

Physics, Astronomy & Cosmology / Re: Would altering the moon's weight change its orbit?

« on: 25/05/2021 11:14:32 »

Why is the Moon moving away from the Earth.  Shouldn't it be getting closer, pulled towards the Earth by gravity?

If there were no gravity, the Moon would depart from the Earth on a straight-line path
- As Newton observed, objects will continue traveling in a straight line, unless acted on by an external force (gravity, in this case)

The definition of an orbit is that the tendency of an object to travel away in a straight line is balanced by the gravitational attraction that bends its path into an ellipse or a circle.
- The Moon has an elliptical orbit, ranging from 363,000km to 405,000km (and back) over the course of each month
- But its average distance is not changing over millennia.

...Unless you look extremely closely - 3.8cm per year means 38 meters in 1,000 years, which is almost nothing compared to 363,000km.

14

COVID-19 / Re: Can we get herd immunity?

« on: 25/05/2021 10:59:41 »

Would (calling it "population immunity" or "public immunity") have been accepted, as a concept,  and  so perhaps, have avoided  the lock-downs?

Calling herd immunity a different name would not have:
- Made the virus any less infectious
- Reduced the number of people who got infected (in the absence of a vaccine)
- Reduced the number of fatalities
- Reduced the need for social distancing, face masks or lockdowns.

What might have helped the UK is if, instead of seizing on "herd immunity" as an excuse to go about your normal business, they had:
- Observed that they would not get herd immunity until most people had been vaccinated
- Observed that getting a new vaccine approved would optimistically take 6-9 months, and at least 6 months to roll out to a significant fraction of the population
- And declared that, in the meantime, there would be border quarantine, contact tracing and compulsory mask-wearing
          That might have reduced lockdowns (but not prevented them)

Even New Zealand, with some of the most effective quarantine restrictions in the world, has had several short lockdowns, and they are thousands of kilometers from their nearest neighbours (most of whom also have low levels of COVID-19).

15

Physiology & Medicine / Re: How close are we to global Polio Eradication, 2021?

« on: 25/05/2021 10:47:39 »

WHO were getting close to polio eradication in and around Pakistan, when the CIA reportedly piggy-backed on a vaccination campaign to locate their latest nemesis through genetic sequencing.
- That produced major distrust of "Western" vaccines, and polio took off again.
See: https://en.wikipedia.org/wiki/Polio_eradication#Opposition_to_vaccination_efforts

16

COVID-19 / Re: Can we get herd immunity?

« on: 24/05/2021 23:23:24 »

Yes, we could get to herd immunity, if enough people are vaccinated (including children).

But you seem to be talking about elimination.
- Elimination is much harder, and it's only worthwhile if the disease causes an ongoing severe health burden, and doesn't have an animal reservoir.
- We know several other species can catch COVID-19 (including house cats and mink), so it will be harder to eliminate entirely.
- It is possible that when the children who caught it as a child get old, it won't be any worse than the common cold, and it will just become endemic (like several other coronaviruses which we group under "the common cold"). That means it doesn't pose an ongoing burden of disease.

17

General Science / Re: What does the following mean (Particle Physics question)?

« on: 24/05/2021 23:14:43 »

The thing about a brick, though, is that you can pick it up in your hand. Look at it.

Yes, a brick lasts longer than a Muon (or a person).
- A human body will typically decay in a decade or so (in a temperate climate).
- Give the brick a million years of erosion by water, wind and sand, and the brick will decay to clay.

The fact of entropy and decay does not make the brick (or the person, or the Muon) any less real

If you accelerate the Muon up to almost the speed of light, you can preserve them a lot longer (due to time dilation), so you can study them more easily...

18

Physics, Astronomy & Cosmology / Re: Can we communicate with civilisation in anti matter solar systems

« on: 19/05/2021 10:54:44 »

is the neutron its own antiparticle or does "spin" spoil things?

A neutron consists of 1 up quark (charge: +2/3) and two down quarks (charge: -1/3 each). Total charge: 0.

An anti-neutron consists of 1 up anti-quark (charge: -2/3) and two down anti-quarks (charge: +1/3 each). Total charge: 0.
- Or should that be "anti-up quark", which would be different from a "down quark"?

Whatever you call it, an anti-neutron is different from a neutron, and the two will annihilate on contact.
- It's the quarks that spoil things...

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

19

Physics, Astronomy & Cosmology / Re: Problems with PopSci articles in GR. Should we stop using one example?

« on: 17/05/2021 23:05:38 »

We propose that GR can produce more than one answer to the way in which the orbit is affected

I challenge this assertion: The equations of General Relativity take the state of the universe at one moment in time, and predict how it will look at the next moment in time
- Unlike quantum theory, it doesn't produce many different outcomes for the same initial state (Einstein was famously opposed to some of the implications of quantum theory)

This is ignoring "impossible" scenarios like "If the Sun suddenly disappeared...".
- If you do something undefined to the universe, then of course it will have undefined impacts on the universe!

20

Cells, Microbes & Viruses / Re: How does norovirus causes loss of taste?

« on: 16/05/2021 22:50:37 »

Norovirus causes severe gastrointestinal upset - extensive vomiting and diarrhea.
- Vomiting alone is enough to interfere with the sense of taste
- And any infection can put you off your food!
See: https://en.wikipedia.org/wiki/Norovirus#Signs_and_symptoms

Coronavirus also interferes with the sense of taste and smell.
- That is because it infects the nasal epithelium, which carries the smell detectors in the nose
-Smell is a large part of taste, so losing the sense of smell will also reduce your sense of taste.
See: https://en.wikipedia.org/wiki/Symptoms_of_COVID-19