Hubble's Deep Field Images

Image Credit: NASA, ESA, R. Bouwens and G. Illingworth (University of California, Santa Cruz) https://hubblesite.org/.../news-releases/2006/news-2006-12

For 10 days in 1995, the Hubble Space Telescope stared at a tiny patch of space near the Plough constellation. It built up a time exposure image showing thousands of galaxies, some so distant it takes 10 billion years for light to reach us from them, travelling at almost 300,000 km per second. In subsequent years, Hubble created further deep field images.
You can read more about the observation on the Hubblesite here.

Making Stiff Plastic, Elastic

Various plastic items. Created by Bing Image Creator.

Materials can be elastic, plastic or both. Plastic materials such as soft toffee, chewing gum or plasticine deform when stretched or compressed, but don't return to their original shape when the external force is removed. Elasticity is a property of a material that allows it to regain its original shape when subject to a force. So for instance rubber is elastic and similarly if you flex a steel ruler or stretch a spring, they regain their shape when the force is removed. When a force is applied to a material, it undergoes a strain, which in mechanics (a branch of physics that deals with energy and forces and their effect on bodies) is defined as the ratio of the extension of the material to its original length. The stress in the material is the tensile reaction due to the external force causing the stretching (effectively the material "pulls back" because of nuclear forces in the atoms). For many materials there's a proportional relationship between stress and strain up to a certain point. Eventually a point is reached however when a material no longer behaves elastically, called the elastic limit, beyond which it will deform plastically. If you've ever bent a piece of metal, you'll know that it'll spring back, but if you bend it too much, it'll stay bent. That's because the elastic limit was exceeded. Even glass is elastic and if you push on a glass window or shower door, you can see the glass flexing. However glass has very little plasticity and usually fractures suddenly when stresses are not much greater than the elastic limit.
This article on Phys.org discusses the issues with polymers and making them stiff and elastic. Currently they can be made elastic or stiff, but not both at the same time. Stiff technically means that there's very little strain for a given stress. So steel is stiff but rubber isn't. However a stiff and strong spring such as used in the suspension of a truck or train is still elastic, and can flex and return to its original shape if subject to large forces. That's not the case with plastic and if it's made stiff, it can't stretch elastically. So it behaves more like concrete when stretched, and fractures. A new technique for making polymers will hopefully improve the properties of polymers so they behave better when used for such things as prosthetics and medical implants.

The Sun's Vital Role: How It Powers Life and Energy on Earth

© Eugene Brennan

 

As you probably know, the Sun is a giant nuclear reactor, the cosmological equivalent of a hydrogen bomb. It’s our nearest star and it would take 600 years to cycle there at a leisurely pace of 12 miles per hour, 24/7. That’s if there was actually a road we could travel on! Even at a distance of 93 million miles, we feel its heat, and it lights our world and has a huge influence on planet Earth. Without the Sun, the Earth would eventually become a cold, frozen place as the temperature of the planet continued to fall to hundreds of degrees below zero. The Sun drives the climate and it creates the energy necessary for crops to grow. Without sunshine, the chemical process known as photosynthesis can’t take place, since plants need light energy to turn CO₂ and water into sugar and starch in their roots, stems and leaves. Without plants, animals can’t survive either, because herbivores eat plants and carnivores in turn eat the herbivores that eat the plants. The Sun was also responsible for providing the energy that is now locked into fossil fuels. Refined oil products and gas originated from dead marine organisms which over millions of years metamorphosed into crude oil. Those organisms, such as plankton, algae and other sea creatures relied on the energy of the Sun for life. Similarly coal originated from trees in ancient forests, pressed into a rock-like material by huge pressures from above. Our renewable energy sources today all derive their energy from the Sun. Solar panels convert sunshine directly into electricity. Wind, wave, tidal and hydro power wouldn’t be possible without the motion of air and sea caused by solar energy heating the ground surface and oceans and generating air currents.

Like most stars, the Sun formed when clouds of dust left over from the formation of the Universe coalesced under the influence of gravity into clumps. The process took millions of years and planets in our Solar System formed similarly. The swirling clumps slowly became more defined and spherical. Small clumps became planets, but the larger clump at the centre of the Solar System continued to become tighter and more compressed. Newton’s law of universal gravitation states that: 

 

“Every particle attracts every other particle in the universe with a force that is proportional to the product of their masses and inversely proportional to the square of the distance between their centres.”

 

The consequences are that the force of gravity is stronger if either or both particles have greater masses and are closer together.

In the case of the Sun, the sheer volume and weight (or more correctly mass in this context) of the clump at the centre of the Solar System meant that there was colossal gravity, and that gravity continued to pull everything together towards a common centre. As everything continued to get closer together, the “distance apart” in Newton’s law became smaller. The result was a runaway situation with distance getting smaller and gravity increasing because of the increasingly smaller distances between particles. Eventually atoms were squeezed into one another, ultimately sparking off a fusion reaction (something we've being artificially doing for decades in experiments on Earth in the quest for fusion power). The process didn’t continue however and eventually there was equilibrium between the heat of the thermonuclear reaction causing expansion and gravity pulling inwards.

Facts about the Sun

 

• It’s 93 million miles or 149 million km from Earth.

• The Sun is approximately 4.6 billion years old.

• It has a diameter of approximately 864,600 miles or 1,391,400 km.

• Eventually the Sun will become a red giant star, swallowing up the inner planets including Earth in 7.59 billion years time.

• Ultimately the Sun will become a white dwarf with 54% of its original mass.

 

Weight is something that changes depending where you are in the Universe. An astronaut weighs less on the Moon, but their mass is the same. Both mass and weight are measured in kg.

Many thanks to ChatGPT for making up the title!

References:

How does the Sun work? | High Altitude Observatory. (n.d.). https://www2.hao.ucar.edu/.../about-the.../how-does-sun-work
K.-P. Schröder, Robert Connon Smith, Distant future of the Sun and Earth revisited, Monthly Notices of the Royal Astronomical Society, Volume 386, Issue 1, 1 May 2008, Pages 155–163, https://doi.org/10.1111/j.1365-2966.2008.13022.x

Structural Colour and Iridescence

A green bottle. © Eugene Brennan

A species of green bottle I think. Sorry quality not the best. Normally the way colour works is that if an object is illuminated by light, pigment in the surface absorbs some wavelengths and reflects others. The Sun mostly produces broad spectrum white light, so a red rose looks red because it absorbs all the colours of the rainbow in white light and only reflects red. Some animals, insects and plants have evolved so they can produce structural colour on their body's surface which doesn't rely on pigments. Instead, the topography of the surface is such that tiny elements like ridges or other structures, having dimensions comparable to the wavelength of light, produce iridescent colours. Iridescence is a phenomenon that makes soap bubbles, oil spilled on a wet road, opals and the underside of CDs look colourful. It's caused by wave interference where waves of light combine and the peaks and troughs add or subtract from each other to reinforce certain wavelengths, making colours emerge from white light. Beetles, blue and green bottles, some butterflies and starlings are examples of animals that use iridescence. The theory is that it confuses predators or is used for communication.

Tomb Tools

Decorative panel from FitzEustace tomb in New Abbey Cemetery, Kicukken, Co. Kildare.

Tools depicted on the side panels that originally formed part of the FitzEustace tomb in New Abbey Cemetery: a claw hammer, nails, a ladder and is that a three-legged pot, or a shield? Maybe a vessel for melting lead in for making flashing for roofs? Or am I just biased and identifying them as such?

Edit: I did a reverse image look-up and it's possibly a collection of musical instruments (lyre and trumpets)
https://www.marcmaison.com/.../fireback-decorated-with...

Why Does Metal Feel Cold and Packing Material Feels Warm?

Image produced on request by Bing Image Creator.

 

When you touch a spoon or walk on ceramic tiles, they feel cold, yet expanded polystyrene packing feels warm as though it’s generating heat.

How come?

It’s because of the differing thermal conductivities of the two materials. Heat capacity also has a part to play.

So what are these physical properties?

A piece of metal, tile and polystyrene left in a room for a sufficiently long period will all have stabilised at a temperature equal to the ambient temperature in the room. However metal and to a lesser extent ceramic have a much higher thermal conductivity than expanded polystyrene. Thermal conductivity is a measure of the rate at which a material can transfer heat energy. 

 

Difference between heat and temperature

 

• Heat is the amount of thermal energy an object has. It's measured in joules. 2 kilos of a substance has double the thermal energy of 1 kilo of that substance at the same temperature. 

 

• Temperature is a measure of the amount of activity of the atoms in a substance. It's the movement of atoms: vibration, spin and translation (movement from one place to another) that gives rise to the temperature of an object. The greater the movement, the higher the temperature. If you've ever been splashed by grease when cooking or hit by a spark from a fire, they were at a temperature of several hundred degrees. However because the splash or spark were small, they didn't have a lot of heat energy and cooled down quickly, compared to having a larger amount of the material making contact with the skin. 

 

Back to the spoons

 

The temperature of the surface of your finger is likely to be over 30 degrees Celsius, however the temperature in a room would be typically 10 degrees or more less than this. Heat always flows from a region of high temperature to one of lower temperature. When you touch a spoon, heat flows from your warm finger to the spoon and the cooling effect is detected by temperature sensors in your skin. The cooling effect is quicker for materials such as metal with a high thermal conductivity because they transfer heat energy faster. The scenario is a little different when touching expanded polystyrene. Because a room will be colder than your finger, your finger is constantly cooling down as air moves around it. However if the room temperature is constant, equilibrium is eventually reached and the surface of your finger will eventually settle at a temperature cooler than that under the surface of the skin, assuming your body continues to provide heat. When you touch a piece of polystyrene, because it has a low thermal conductivity, heat flows into it at a very low rate. However if it covers the pad of your finger, the heat loss from your finger to the surrounding air will be reduced. That reduction is likely to be greater than the heat transfer to the polystyrene, so your finger will tend to warm up. So it’s not the polystyrene that’s generating heat, making it appear warm, but your finger heating up because it no longer cools as it loses heat to the surrounding air.

Thermal conductivity is measured in watts per meter-kelvin ( W/(m K) )

 

Joules and Kelvin

 

Temperature is measured in degree Celsius. The zero point on the scale is the freezing point of water and 100 degrees is the temperature water boils at. For scientific purposes, the Kelvin scale is used, and the only difference between it and the Celsius scale is that the zero point is shifted to absolute zero. Absolute zero is when all movement of atoms ceases. It has never been reached, but we have cooled substances to within tiny fractions of a degree above absolute zero. The divisions on the Celsius and Kelvin scales are the same, so a temperature change of 1 °C = 1 K. (Note that the ° symbol is not used with the unit’s symbol “K”.)

 

Why does it feel colder on damp days?

 

Higher thermal conductivity of water versus air explains why damp days feel colder than when air humidity is lower, even though the air temperature is the same. Winter temperature in continental climates is often much less than in Ireland, but because of the dry air, it never feels as cold. 

 

Heat capacity

 

This is another property of matter that can influence how we perceive cooling. It’s defined as the amount of heat required to change the temperature of a substance by 1 K. Water compared to other liquids has a huge heat capacity and requires lots of heat energy to raise its temperature. The specific heat capacity of a substance is the amount of heat energy required to raise 1 kg of that substance by 1 K. The SHC of water is approximately 4200 J/(kg K). (Expressed as 4200 joules per kilogram per degree kelvin.)

If you dip your finger into water, since water has a high SHC, it continues to drain heat energy, lowering the finger's temperature. A liquid with a lower SHC such as olive oil would rise in temperature faster, and if there was no mixing of the liquid, this would reduce the thermal gradient, slowing heat loss. So olive oil wouldn't feel as cold if you put your finger in it.

 

Resources

Thermal conductivities of various materials:
https://www.engineeringtoolbox.com/thermal-conductivity-d...

Specific heat capacities if different materials:

https://www.engineeringtoolbox.com/specific-heat-capacity...

Why is There a "Live" Wire in Our Electrical Supplies?

3-pin plug. © Eugene Brennan

If you've ever wired a plug, you'll know there are three cores in the flex that need to be connected to the terminals: brown - live, blue - neutral and green/yellow - earth. The same goes for the wiring to all socket outlets and ceiling roses. The brown wire is the dangerous one because it's normally at a voltage of approximately 230 V when power is connected. So if AC voltages switch direction and there's no inherent difference between live and neutral, why is live at 230 V and neutral at 0V (assuming earthing is done properly in a premises)? Why if I use a phase tester screwdriver or Fluke VoltAlert type tester do I get a glow when I check the live wire? The reason is because all supply transformers have one point in the secondary winding earthed to the bulk of the ground surface at one or more points. The neutral supply to our homes is supplied from that point in the transformer. Also neutral in our homes is tied to the earth terminal at the electrical panel and connected to an earth rod to pull the potential of earth and neutral as close as possible to zero volts. (Known as TN-C-S earthing). Because neutral and earth are held at zero volts, live is consequentially at 230 volts with respect to earth. That's why a phase tester screwdriver lights up because current flows from live to the tip of the screwdriver, through the neon tube and high ohmic value resistance down through your body to the ground you're standing on. It then makes its way trough the bulk of the ground back to the supply transformer which is earthed.

 

Why is a supply transformer earthed? 

 

For safety reasons and to cater for dangerous voltages on the secondary that supplies homes. If it wasn't, several dangerous scenarios could arise: For instance, if the insulation broke down in the transformer between primary (which is supplied at 10,000 V) and secondary, a lethal voltage could end up being delivered to a home. Another possibility is that very high voltage lines (e.g. the ones carried by the pylons at Silliot Hill) could fall on output lines from the transformer and a third scenario is a lightning strike on a line. By connecting one point of the winding of a transformer to ground, rather than having it floating, it makes the system safer.

 

110 V Safety Transformers 

 

Cordless power tools are more common nowadays, but previously these transformers were used for safety reasons to reduce 230 V to 110 V. Firstly, the lower 110 V lessens the risk of electrocution because current is what kills when it passes through the heart. Lower voltages, reduce the risk because they "push" less current though a circuit. Another safety feature of these transformers is that the centre tap of the secondary winding is earthed (unlike neutral in a home). This means that there are effectively two "lives", but each is only at half of 110 V or 55 V wrt to earth. This is a secondary safety feature, if for instance contact is made with a cut flex.

3D Magnetic Field Visualisation

Ferrofluid following magnetic field lines. Image attribution: Gregory F. Maxwell, CC BY-SA 3.0 via Wikimedia Commons

You probably performed the experiment in primary school where you place a sheet of paper over a bar magnet and sprinkle iron filings, give the sheet a tap, and the particles of iron arrange themselves along the magnetic field lines of the magnet. However the iron filings experiment only visualises a slice through the magnetic field. In fact, magnetic fields are three dimensional and the top photo is a 3D version of the experiment using ferrofluid, a colloidal liquid (like milk or emulsion paint) with a suspension of nanoscale ferromagnetic (influenced by magnetism e.g. iron) particles. The ferrofluid is placed on a sheet of glass above a neodymium magnet.

Iron filings on paper following magnetic field lines of a bar magnet. Image attribution: Newton Henry Black, public domain via Wikimedia Commons

 

How Motors Work

Single loop motor armature. Image author Lookang, CC BY-SA 3.0 via Wikimedia Commons

These are quite good graphics, (not the animation above) on the Georgia State University site showing the BIL force on a conductor in a magnetic field, and how a traditional DC motor works. The first practical electric motor dates from 1834.

If I is the current flowing through the armature (the thing that turns in a motor) in amps, B is the magnetic flux density in tesla (how concentrated the magnetic field is) and L is the length of the armature in metres, then the force on the armature coil in newtons is:

 

F =BIL

 

One side of the coil experiences a force F in one direction and the other side a force F in the other direction (because the current flows the other way). These two forces are known as a couple. A couple creates a torque (twisting force) and the magnitude of the torque in newton-metres (units Nm which you'll sometimes see on cordless drill specs) is:

 

T = FW

 

where W is the width of the armature.

The effect of the torque is to turn the armature which is made up of coils wound around a laminated soft iron core, mounted on a shaft.

The motor in the graphic has a single coil. Real world universal motors (which run on AC or DC) in a corded power drill, vacuum cleaner, food mixer etc have an armature with many loops of wire so the electromagnets (the grey things in the graphic) can keep exerting a force as the armature turns. A commutator switches power to the loops via graphite brushes while the armature is turning.

Motors in electric vehicles and cordless tools work on a different principle. They don't use brushes and rely on the interaction between varying magnetic fields in both a stator (a fixed coil located around the internal perimeter of the motor) and a rotor which turns.

What Came Before the Big Bang?

Image created on request by Bing Image Creator.

The general consensus is that space and time began with the Big Bang and everything expanded from a mathematical point. It wasn't as though there was a massive explosion and then everything expanded into a huge, pre-existing void. We couldn't identify a point in space today where the Big Bang occurred and put a plaque at it marking the event. In a sense it occurred everywhere. Before the Big Bang, there was no space, it was created, as was time. So there was also no "before" the Big Bang.

"Nothing was around before the Big Big(sic) Bang" according to Stephen Hawking in this interview where he discusses the concept of four dimensional "spacetime".

Cartoon created on request by Bing Image Creator. The Grammar Police were involved because BIC can't spell !

 

#scienceweek #ScienceWeek2024

Wave Interference

The red and green waves sum together to produce the red wave..Image author Wolfgang Christian and Francisco Esquembre CC BY SA4.0 International via Wikimedia Commons

The red wave is the sum of the green sine wave travelling right and the blue sine wave travelling left. When the peaks of the red and blue waves are coincident and they add, the result is constructive interference and when peaks coincides with troughs, they subtract, resulting in destructive interference. The waves can be sound, light, radio waves, waves in the sea, ripples in a pond, gravity etc. Wave interference is responsible for the phenomenon of iridescence (e.g. colours on spilled oil or petrol on a wet road), beat frequencies with sound waves (e.g. two tuning forks giving a tremolo effect and periodic rise and fall in sound level) and contouring of coasts when sea waves combine. Coastal features called tombolos where an island joins to the mainland by a sand bridge (e.g. Howth Head or Palm Beach in Australia, used as the film location for the fictitious Summer Bay in Home and Away) are caused by refraction (a type of interference of sea waves).

On "Can Scientists Save the World?" on BBC One Tonight

Illustration on request by Bing Image Creator

 

In a documentary on BBC One, there was a report about a cleantech company called Synjelion who have developed technology that sucks water and CO₂ out of the air and uses energy sourced from solar panels to power a process that produces jet fuel. It's basically a synthetic version of photosynthesis, except plants make sugar, starch and cellulose, using water, carbon dioxide and sunlight. All the wood that makes up a tree comes from carbon taken out of the atmosphere. Meanwhile we breathe out all the carbon in our food in the form of carbon dioxide.

Science Friday Podcast — Prime Numbers

Image by Bing Image Creator

If you remember back to studying maths at school, you might recall that prime numbers are numbers that only be divided equally by themselves and the number one. So 2, 3, 5, 7 and 11 are primes. 4 isn't because it can be divided by the factors 1, 2 and 4. Prime numbers are important for cryptography and security of data and discovering new ones is challenge. Finding increasingly large primes takes time, even for computers, because a number has to be checked with numbers smaller than it to make sure they don't divide in evenly, making the number non-prime. In this podcast, Ira talks with Jack Murtagh, math writer and columnist for Scientific American, about why prime numbers are so cool, and the quest to find the largest one.

Big Picture Science Podcast — Beyond the Periodic Table

Public domain image via Pixabay.

 

Directly after the Big Bang, there were no elements as we know them today. So no hydrogen, helium, copper, gold, mercury, chlorine or any of the other 94 or so naturally occurring elements. There were just sub-atomic particles such as quarks and electrons. A few millionths of a second after the Big Bang, these aggregated to form protons and neutrons. Hydrogen is the most common element in the universe, simply because there's a greater probability of a single electron and proton coming together to form a hydrogen atom. Other elements are more complex, consisting of various arrangements of protons, neutrons and electrons in their atoms. For instance, the total number of protons and neutrons in a gold atom's nucleus is 197 and there are an additional 118 electrons in its outer shells. It's much less likely for over 300 random particles to come together to make up that arrangement, that's why gold is so relatively rare.
In this episode of Big Picture Science, the team discuss the history of the periodic table and how we're making new elements, some useful and others purely for research purposes (The radioactive isotope Americium 241 is commonly used in smoke alarms, others are used for radiotherapy). Guests include Jennifer Pore – Research Scientist of Heavy Elements at Lawrence Berkeley National Laboratory and Mark Miodownik – professor of materials and society at University College London and the author of “It’s a Gas: The Sublime and Elusive Elements That Expand Our World.”

Woodchip Gasifier Genset

I'd like a small version of one of these for turning my garden waste to electricity. I haven't read the full details, but basically it heats or roasts wood chip to make gas which runs an engine and drives an electrical generator, producing heat as a by-product. Gasification was the process used from the 18th century up until the early 60s for making gas from coal, i.e. coal gas. This was stored in large tanks called gasometers. The process was superseded by gas production from naptha, a waste product of the petroleum industry and eventually in the 80s, we started using cleaner natural gas or methane from natural deposits such as the Kinsale Head gas field.

Gasifier gas driven engines were used in the UK for running cars and buses during WW2 when petrol was in short supply.

Reverend Nicholas Callan and the Induction Coil

Rev. Nicholas Callan. Public domain image via Wikimedia Commons: https://en.wikipedia.org/wiki/Nicholas_Callan...

Did you know that the induction coil is an Irish invention by Reverend Nicholas Callan (1799 - 1864), a physicist and Catholic priest at Maynooth University?

The device is a type of transformer, commonly used in vehicles in the form of an ignition coil for generating the tens of thousands of volts necessary to create a spark at the plugs. Induction coils with an output of hundreds of thousands of volts were used for early spark-gap transmitters. Connected to a tuned circuit and antenna, they could transmit radio waves at a certain frequency. The tuned circuit is the electrical analog of a bell. A spark discharge "rang" the bell by setting off electrical oscillations.. These transmitters would have been used for intercontinental and ship-to-shore communications in the era of the Titanic.

 

Electromagnetic Induction 

 

Electromagnetic induction is a phenomenon discovered by the English scientist Michael Faraday in 1831. If you move a magnet close to an electrical conductor, e.g. a looped piece of wire, the field of the magnet induces an electric current in the wire. It's the change in magnitude of the magnetic field that creates the current, rather than the fact that the magnet is moving. If the field is constant in magnitude, no current is induced. The magnitude of the voltage that creates the current is proportional to the rate of change of magnetic flux, in other words, the faster the magnetic field changes in size, the greater the voltage.

 

How Do Transformers Work?

 

All transformers and electrical generators work on the principle of electromagnetic induction.

The transformers such as those used in older power adapters and corded electronic equipment have a laminated core, made of a stack of wafer-thin, soft iron sections, insulated from each other. A primary coil wound around the core (hundreds of turns of wire) generates a fluctuating current when connected to an AC mains source. This in turn creates a fluctuating magnetic field and that field then induces an electric current in a secondary winding. A transformer simply increases voltage, or decreases it, like the room sized transformers we have at the sub-station in Kilcullen. The ratio of the number of turns of wire on the primary coil to those on the secondary coil, known as the turns ratio, determines the factor by which the output is increased or decreased. So if the input coil has 1000 turns and the secondary coil has 100 turns, that's a turns ratio of 10 and voltage is reduced by a factor of 10

 

Schematic of a transformer. Image author BillC at the English-language Wikipedia, CC BY-SA 3.0

 

What are Induction Coils?

 

Instead of being fed by AC, an induction coil works on DC. It has a primary coil with hundreds of turns of wire and a secondary with thousands of turns. The coil when energised also acts like an electromagnet. This isn't the case with a standard transformer because the iron core is in the form of a closed loop, with no external field. The DC source, e.g. a battery, is connected to the coil via a spring switch, called an interrupter, that can be opened and closed by the force of the electromagnet (the same mechanism is used on old doorbells). On connection of the supply, with the switch closed, the magnetic field in the core grows until the electromagnet suddenly opens the switch, disconnecting the input. The magnetic field rapidly collapses and it's this rapid collapse and change in field that induces a huge voltage in the secondary, much greater than the turns ratio could produce with an AC source. When current is disconnected by the switch, the force of the electromagnet drops to zero, causing the spring to close the switch again, reconnecting the circuit and the cycle repeats indefinitely, generating high voltage pulses at the rate of hundreds per second.

 

An induction coil. Image courtesy Hannes Grobe, CC BY 3.0 via Wikimedia Commons

 

More information on Rev. Nicholas Callan on the Maynooth University website here:

https://www.maynoothuniversity.ie/electronic-engineering/callan

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