21

Physics, Astronomy & Cosmology / Re: What do strange quarks do?

« on: 13/09/2018 11:54:33 »

the neutron lifetime puzzle

I wondered why I kept seeing different figures for neutron lifetime.

Not the 9 second difference between beam and bottle experiments.

But the larger difference between half-life and mean lifetime...

22

Technology / Re: How do astronauts clean their teeth in space?

« on: 09/09/2018 11:35:30 »

Chris Hadfield set out to inform (and entertain):

23

Physics, Astronomy & Cosmology / Re: What do strange quarks do?

« on: 09/09/2018 07:23:37 »

At one level, science avoids questions like "what are they for?" and "what do they do?".

Science can detect some patterns, like there a 3 "generations" of quarks (purple) and 3 "generations of leptons (in green):

Standard_Model_of_Elementary_Particles.png (93.91 kB . 375x359 - viewed 1245 times)

We are most familiar with the stable members: up & down quark and the electron. These are the left-most particles.
Sensitive detectors can identify neutrinos (which are always oscillating); practical applications of these is currently limited to peering inside the Sun and exploding supernovae. We can also detect muons from cosmic rays, but practical applications are limited to peering inside pyramids.

The rightmost particles are unstable, and quickly decay into the stable particles to the left.
See: https://en.wikipedia.org/wiki/Generation_(particle_physics)
https://en.wikipedia.org/wiki/Standard_Model

The other quarks have very high energies, and can only be created for an instant in our most powerful particle accelerators. These emulate the extreme energies that existed for a moment during the Big Bang, when these heavy particles would have been stable (for a moment).

So, while they don't do much today, they would have played an important part during the Big Bang.

Maybe some advanced civilisation may be able to create and utilise these other quarks, but we can't today.

Some physicists think that these more exotic quarks may be stable under the extreme pressures at the center of a neutron star, preventing the neutron star from collapsing into a black hole. That's why it's important for LIGO to "weigh" colliding neutron stars.

Some physicists speculate that there may be other generations at even higher energies than the 3 we know, but these would exist at such high energies that we can't produce them today.

24

Physics, Astronomy & Cosmology / Re: How do you steer a rocket following take-off?

« on: 08/09/2018 09:45:17 »

The optimum course is a compromise:
- the atmosphere is a real drag, so you want to go vertically to get above it as quickly as possible.
- attaining a stable orbit means that you need to be traveling horizontally at about 7.5km/second (for the ISS).
- so, in practise, they do more vertically at first, and then more horizontally later.

This has to be modified for air-launched space probes, which are already above most of the atmosphere when they are launched (eg at 50,000 feet), and already travelling horizontally. But they need a lot more altitude to reach space, and a lot more horizontal velocity to reach orbit.

Rocket motors are often mounted on gimbals, allowing the engine direction to be steered, which changes the direction of the whole spaceship.

Edit: Error pointed out by Chris...

25

Cells, Microbes & Viruses / Re: What kind of cyber security should we use in a clinical diagnostics lab?

« on: 02/09/2018 22:29:29 »

If you need to transfer some test results to a medical practitioner, do you send them as an unencrypted email, or is there some government-sponsored health record where you can upload the test results as an encrypted transfer, and the medical practitioner can download the results as an encrypted transfer?
You could also install a "firewall" between your lab network and the public internet. This can block some threats, and take records that highlight when you have been hacked from the public internet.

A lot of threats come from inside your network - how do you screen your staff?
- How would you prevent members of the public from accessing your systems if they were left alone in your clinic (logging off when leaving the room might help).

26

General Science / Re: Does a particle approaching the speed of light gain mass?

« on: 01/09/2018 23:26:34 »

I have heard particle accelerators use particles and let them travel very close to the speed of light (c).
0,9999...% to (c) I once have seen.

The Large Hadron Collider (LHC) is currently the world's most powerful particle accelerator.
It can accelerate protons up to  99.999999% of c, or about 11 km/h slower than the speed of light (c).

One way physicists measure the mass of a particle is in units of GeV/c².
A proton at rest has a mass of 0.938 GeV/c².
When up to speed in the LHC, the proton has a mass of around 6500 GeV/c².
See: https://en.wikipedia.org/wiki/Large_Hadron_Collider#Design

Just hypothetical. What would happen if one of these particle travel at (c). Would the particle have an infinite amount of mass?

Yes, it is just hypothetical, because we can never accelerate a massive particle to the speed of light in a vacuum, with a finite amount of energy, or in a finite amount of time.

There is one context where we can "bend the rules": Light travels slower in a material like water.
A nuclear reactor emits subatomic particles at almost the speed of light (in a vacuum), which is faster than the speed of light in water.
This results in Cherenkov radiation, the blue glow seen around water-cooled nuclear reactors.
See: https://en.wikipedia.org/wiki/Cherenkov_radiation

27

Physics, Astronomy & Cosmology / Re: How to find the velocity?

« on: 01/09/2018 11:33:29 »

A totally different approach, which needs a lot less calculus:
When I see the (x,y) position of an object described as (x=a*sin(ωt), y=a*cos(ωt) ), I deduce that we are seeing an object which is in a circular orbit around the origin = (0,0).

Now, a circular orbit is:
(1) not moving towards the origin
(2) and it's not moving away from the origin
(3) And the velocity is not moving in the same direction as the line from the origin to the point, which is the same as (2)
(4) in fact, the velocity is moving at right-angles (perpendicular) to the line from the origin to the point. This is what continually bends the path around in a circle.

Whether a qualitative answer like this will make the examiner happy is another story!

28

General Science / Re: Does using 93 octane petrol rather than 95 octane make a difference?

« on: 01/09/2018 02:15:25 »

Does it make a difference

It depends what difference you are looking for....
The one most people are concerned about is "how far can I travel on $10 of petrol?", and this is an economic question.
- I have seen some people try to evaluate this, and the results in that test were that you could travel slightly farther on $10 of the higher octane fuel.
- But this depends on pricing policy by the petrol company, which I am sure will vary from country to country.

On the other hand, if your criterion is minimising net CO₂ output, "green" petrol tends to have a lower octane rating due to mixing in 10%-20% ethanol.
- If you live in a country like Brazil, where there is a national programme of turning sugar cane into ethanol for fuel, then your net CO₂ emissions will be lower with the ethanol fuel than with the 100% fossil-sourced petrol.

29

General Science / Re: What are the common methods to quantify accuracy and precision?

« on: 23/08/2018 10:56:50 »

What are the common methods to quantify accuracy and precision?

In assessing these parameters, it is important to get input from the affected parties - they may view the required accuracy and precision very differently from you (and each other).

This lets you view the system you are optimising as part of a larger system, and not treat it in total isolation. The worst possible outcome is to spend lots of effort on improving one part of the system, but it doesn't help the overall system.

Without knowing anything about the system you are working on, I suggest that your assessment should include input from:
- Those people who use the output of this system
- Those operators who control the process
- Those providers who provide inputs to the system
- Someone who knows about the costs and delays in running the system (costs & delays are usually larger when the system doesn't meet the required performance)
- Often, when you get these groups together, all of them find out things that they didn't know about the system. This allows you to refine the requirements for your study.

30

Physics, Astronomy & Cosmology / Re: What would a cold neutron star look like?

« on: 14/08/2018 23:20:42 »

create geometries very unlike such oxides at standard conditions

I agree that there will be crystal structures and molecules that would never be stable on Earth.

One unique thing that we don't have to worry about on Earth is that the gravitational potential energy on the surface of a neutron star is greater than the strength of mere chemical bonds. So elements would be sorted vertically by density. Chemical bonds would only be possible between atoms of very similar density.

The lightest element is hydrogen, and so it would be in the outer layer. Under these pressures hydrogen would probably form a metallic state, possibly superconducting?

A more speculative distorting factor is that the tidal forces and time dilation effects on the surface of a neutron star may be enough to distort the form of the electron's wave equation so that it takes on different forms than we have on Earth. What this would do to the interaction between light and matter is beyond me!

31

Technology / Re: How will the Parker Solar probe (sun grazer) communicate its data?

« on: 12/08/2018 22:00:19 »

Although the Parker Solar Probe comes very close to the Sun (at perihelion), it spends most of its time far from the Sun (aphelion is at the same distance as Venus).

So for the week or two when it is closest to the Sun, electromagnetic interference from the Sun will prevent radiotelescopes on Earth from receiving data from the space probe. It must be oriented so that the heat shield protects it from the Sun.

Just as Venus is often invisible from Earth because it is behind the Sun (but far from the Sun), the Parker probe will often be out of communication with the Earth, so it has to be very autonomous.

However, for most of its orbit, it will be separated far enough from the Sun in the sky that radiotelescopes on Earth can communicate with it to download the scientific data and upload new instructions. The probe has a 0.6m steerable parabolic dish. The only direction it can't point is within 14° of the Sun's center, as that direction is obstructed by the solar shield.

See: http://parkersolarprobe.jhuapl.edu/index.php#spacecraft
https://directory.eoportal.org/web/eoportal/satellite-missions/p/psp
https://en.wikipedia.org/wiki/Parker_Solar_Probe

32

Chemistry / Re: How to calculate the maximum charge of an atom or a molecule?

« on: 10/08/2018 13:07:57 »

How to calculate the maximum charge of an atom or a molecule?

I think there may be several concepts mixed up here...

Charge of an Atom (Dissolved Ions/Ionic Solids):
It will help if you look at a periodic table while reading this, for example the one here:
https://en.wikipedia.org/wiki/Electronegativity#Electronegativities_of_the_elements
- The intense red elements (eg Fluorene, F near top right) will strongly grab an electron off another atom
- The lightest yellow elements (eg Cesium, Cs near bottom left) will easily donate an electron to any other nearby atom
- Most elements are somewhere in-between
- If you put together elements that are far apart on the electronegativity scale, they will completely transfer an electron (or more) between the atoms, and both atoms will become charged ions.
- The grey noble elements on the top right (eg Helium, He) do not easily donate electrons or take on extra electrons.
- The number of electrons an atom is likely to accept or give away is determined by the distance to the nearest noble gas, which has a full outer shell of electrons.

If we take as an an example table salt, which is mostly Sodium Chloride
- Sodium is in group 1, and easily gives up one electron (the nearest noble gas is Neon, distance = -1)
- Chlorine is in group 17, and easily takes on one extra electron (the nearest noble gas is Argon, distance = +1)
- At room temperature salt forms solid crystals of Sodium Chloride Na⁺Cl^-
- When dissolved in water, they separate to form Na⁺ and Cl^- ions, and it conducts electricity
- When molten, the Na⁺ and Cl^- ions can move, and it conducts electricity

Most metallic atoms easily lose an electron (or two; sometimes 3), forming a positive ion:
- Atoms in the left-hand column (Group 1) easily give up 1 electron. Common examples are Sodium (Na) and Potassium (K)
- Atoms in the next column to the right (Group 2) easily give up 2 electrons. Common examples are Calcium (Ca) and Magnesium (Mg)
- Under some chemical conditions, atoms in Group 13 can give up 3 electrons, eg Aluminium (Al)
- Some of the atoms in between (like Iron, Fe) can give up 2 or 3 electrons, depending on the chemical conditions.

Many non-metallic atoms easily take on an extra electron (sometimes 2 or 3).
- Atoms in Group 17 (eg Chlorine & Iodine) easily take on 1 extra electron
- Atoms in Group 16 (eg Oxygen & Sulphur) easily take on 2 electrons
- Under some chemical conditions, atoms in Group 15 will take on 3 electrons

When dissolved in water, these individual atoms with an electric charge form ions, and will conduct electricity.

Charge of a Molecule:Some molecules containing the atoms mentioned above can form chemical groups which a charge, for example sulphuric acid (H₂SO₄) contains sulphur, and when dissolved in water, the SO₄ ion has a charge of -2.

In a pure element (eg pure Sodium or pure chlorine), all the atoms have the same electronegativity, so they can't give up or take on an extra electron, so they are electrically neutral.

Most stable, complex molecules (like organic molecules) are formed of a mix of elements which share electrons, ie they never completely giving them to another atom, nor completely take them away from the other element.
See: https://en.wikipedia.org/wiki/Covalent_bond

These covalent molecules are overall close to electrically neutral, although there are organic acids that can give up a hydrogen ion to take on an overall negative charge. And some parts of the molecule might have a slightly more positive or negative charge, which can help proteins fold into the right shape.

Ionised Atoms: Above I talked about atoms which easily give up or take on a few electrons, becoming more like the noble elements in Group 18.
- However, if you expose the atoms to extreme temperatures (eg in the Sun's corona), you can rip off extra electrons.
- Similarly, if you subject atoms to an extreme electrical discharge, you can make them give up or take on a larger or smaller number of electrons.
But these unusual charges don't persist at room temperature in our homes.

If you subject a molecule to extreme temperatures or extreme electrical discharge, it will usually tear the molecule apart, right down to ionised atoms.

Mass Spectrometer:This scientific instrument subjects molecules to a controlled electrical discharge, which applies a small charge to the whole molecule, or breaks down the molecule into some smaller components, each with an electrical charge.
It is able to provide an indication of the chemical composition of an unknown substance by measuring the charge to weight ratio of the pieces.
See: https://en.wikipedia.org/wiki/Mass_spectrometry

Oops! overlap with chiralSPO!

33

General Science / Re: How does this wire work in the pylon?

« on: 08/08/2018 11:12:42 »

Yes, electricity networks use their pylons to carry optical fibers for their own network control.

It costs almost the same to install 1, 5 or 10 optical fibers. By installing 5 or 10, these can then be sold or leased to telecommunications companies (or those who want to compete with the established telecommunications companies).

Electricity companies have already negotiated a "right of way" over land, roads, waterways, etc.
- They reuse this "right of way" to carry the optical fiber
- This is much cheaper than someone who wants to install their own optical fiber, and will have to negotiate with all of those existing land owners (some of whom are their competitors), and get permission to dig up their farm or street (potentially damaging water pipes, gas pipes, electricity supply and other telecommunication cables).

34

Plant Sciences, Zoology & Evolution / Re: Why is natural selection so much slower than human-led selection?

« on: 06/08/2018 12:16:56 »

Associating the word prediction and the word lottery like you do can thus be misleading.

Another way of looking at it is that a species with a lot of genetic diversity has bought a lot of tickets in the future, which often looks like a lottery to us.
That genetic diversity increases the chance that they will hold a winning ticket (or at least a minor prize).

mind may produce randomness the way mutations do

In the young mind, neurons are connected randomly to other neurons.
However, as each critical phase of development occurs, connections that don't produce a significant correlation get pruned, leaving a much smaller set of neural connections.

Effectively, a process of "survival of the fittest" determines which neural connections will be retained and which will be lost, based on the environmental exposure leading up to this pruning phase.
If I understand the mechanism, this pruned set of connections then provides the neural inputs to the pruning of the next level of neurons, at the next stage of development.

By this mechanism, an infant becomes adjusted to their environment, even if that environment is quite different from the environment in which their parents grew up.

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

35

New Theories / Re: Super Nova ?

« on: 05/08/2018 11:55:48 »

If you want to hear some impressive science knowledge, answering questions without notice, listen to:
- http://www.abc.net.au/triplej/dr-karl/
- http://www.capetalk.co.za/podcasts/115/the-naked-scientist/78148/naked-scientist-dr-chris-smith

I have the luxury of checking my vague recollections on Wikipedia before I post them.

36

New Theories / Re: Super Nova ?

« on: 05/08/2018 04:11:26 »

I didn't have time to watch both videos all the way through, but:
- The first video is about Betelgeuse, a red supergiant star that will probably go supernova in the next million years (and may even have gone supernova already - but we don't know it yet!). Because it's only 700 light-years from Earth, it would be brighter than the full Moon. A much closer supernova could damage life on Earth.
- The second video is about supermassive black holes at the center of galaxies; it is not about supernovae. The nearest supermassive black hole is about 25,000 light years away, and is fairly quiet at present, so this is likely to pose less of a risk in the near future than Betelgeuse (or pollution, which is even closer).

Astronomers are always on the watch for new supernovas, as it tells much about:
- What sorts of stars can go supernova, and at what stage of their lives (this has only recently become feasible to model on our very largest supercomputers, at immense cost)
- Understanding why there are far fewer visible supernovas in our galaxy than theory predicts
- What is the brightness of different types of supernova
- Imaging a supernova using neutrinos
- Refining the distance to distant galaxies
- Measuring Dark Energy
- Supernovas can be discovered by amateur astronomers, giving them their 15 minutes of fame.
- Close supernovas are visible to the naked eye, which is of interest to the general public

Some specialist telescopes scan the night sky on a daily basis, looking for supernovas in other galaxies.
https://en.wikipedia.org/wiki/All_Sky_Automated_Survey_for_SuperNovae

37

Physics, Astronomy & Cosmology / Re: How fast would the earth spin if the moon was closer?

« on: 03/08/2018 23:20:09 »

Using the Moon to dig a 1,000km-deep trench around the Earth would also cause the Moon to break up...

38

Plant Sciences, Zoology & Evolution / Re: Why is natural selection so much slower than human-led selection?

« on: 02/08/2018 22:23:28 »

Why is natural selection so much slower than human-led selection?

Natural selection is a somewhat random process, which means that a beneficial mutation spreads very slowly through a wild population (or may get snuffed out in the first generation).

There is discussion at present about a "gene drive" which will cause a human-made mutation spread exponentially through a wild population. It ensures that more than 50% of the progeny have the gene drive (ie it doesn't obey Mendel's "laws" of inheritance).

Since this could have major impacts on the world's ecology, the inventors have requested a vigorous debate before anyone releases this in the field.

So to prevent the spread of malaria, it is possible to have a gene drive that wipes out all mosquitoes, but this would have unknowable impacts on bird, fish, amphibian and bat populations, plant fertilisation, etc etc.
- Alternatively, it is possible to have a gene drive which leaves behind healthy, blood-sucking mosquitoes, but which carry a gene variant that stops the malaria parasite from infecting them (a gene taken from a mosquito species that does not spread malaria).

Whether members of the public would accept being bitten by a genetically-engineered mosquito is another question; they may be afraid of being exiled as a mutant super-hero....

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

39

Physiology & Medicine / Is Toxo-enhanced business acumen all in the mind?

« on: 01/08/2018 23:14:36 »

This week's Naked Scientists podcast covered a paper suggesting that exposure to the Toxoplasmosis parasite is associated with a more entrepreneurial outlook on life, and an increased likelihood to undertake business studies.
https://www.businessinsider.com.au/parasite-in-cat-poop-linked-to-entrepreneurial-behavior-2018-7?r=US&IR=T

Previous studies have shown that "Toxo" infection is associated with more risk-taking behavior (eg increased motor vehicle accidents).
- Is it possible that the association shown in self-reported surveys represents risk-taking behavior in a survey?
- Can we get some more objective measures of whether Toxo is associated with greater success, or is it all in the mind?

For example, in the study that showed a link between Toxo exposure and motor-vehicle accidents, did the Toxo-enhanced drivers rate themselves as better drivers than the non-Toxo drivers who had fewer accidents?
See: https://en.wikipedia.org/wiki/Toxoplasmosis#Mental_health

PS: The story should probably have mentioned the usual warning against pregnant women carrying out the cat tray, as Toxo can kill or maim the unborn baby.
See: https://en.wikipedia.org/wiki/Toxoplasmosis#Pregnancy_precautions

40

New Theories / Re: I have refuted the atomic model

« on: 30/07/2018 10:48:37 »

Only if (electrons) are robots and instructed with some kind of intelligence.

Another hypothesis is that all electrons are almost identical and mindless.
- They "fill up" the available energy levels in an atom by falling into the lowest available energy level (like a grain of sand in an hourglass)
- The preferred number of electrons is determined by the charge on the nucleus
- There is an equation that defines how many electrons can go into each level in an atom
- The Schrödinger equation which describes these levels is very compact: It easily fits on one line.
- It takes a very complex equation to describe intelligent behavior, so I suggest that electrons are not behaving intelligently

See: https://en.wikipedia.org/wiki/Schr%C3%B6dinger_equation