Decline in Student Entrollments in Academic Subjects

 This fabulous graph of enrollments in the most popular HSC subjects over time was published in the Sydney Morning Herald today:

 

In the newspaper article, concerns were raised about the declining number of physics students, and the fact that only 22% of these students were female.

What I see in this graph is a general downward trend in enrollments of most of these subjects. You'd be particularly concerned about your future employment prospects if you teach Ancient History, for example.

What I don't see in this graph are any dramatic increases in enrollments, so, where have all the students gone?

Are overall student numbers declining (and hence enrollments in individual subjects are declining)?

Or, are there other less popular subjects with massive increases in student enrollment?

If we are concerned about the lack of females in Physics (22% female) why are we not equally concerned about the lack of males in Biology (36% male)? Or the poor showing of males in English Extension 1 (33%) and 2 (29%). 

We are still seeing student numbers divided along gender lines. So here are some "not-at-all-surprising" stats ...

• 5% of students in "Dance" are male
• 5% of students in "Textiles and Design" are male
• 8% of students in "Human Services" are male
• 10% of students in "Community and Family Studies" are male
• 5% of students in "Construction" are female
• 5% of students in "Electrotechnology" are female
  
• 6% of students in "Automotive" are female
• 9% of students in "Engineering Studies" are female
• 10% of students in "Software Design and Development" are female 

 And if I went back 30 or 40 years, I'm guessing the percentages would not be so very different.

What have we achieved in education in 4 decades?

Shapes of Melting Ice

 What shape is submerged ice as it melts?

That depends on temperature apparently ..

 Which suggests that we can infer water temperature in nature by observing the shape of its melting ice.

Scott Weady, Joshua Tong, Alexandra Zidovska, and Leif Ristroph (2022); Anomalous Convective Flows Carve Pinnacles and Scallops in Melting Ice. Phys. Rev. Lett 128(4)  https://doi.org/10.1103/PhysRevLett.128.044502

Building Height and Earthquakes

• High-frequency, low amplitude waves affect short buildings
  
• Low-frequency, high-amplitude seismic waves affect tall buildings
  
• Middle height buildings are affected by 2-3 second-long seismic waves
• (Mexican earthquake damage 1985)

Tonight's the Night

On Friday 21 August 2015 Mt. Stromlo Observatory will be leading Australia in attempting to break two Guinness World Records - Most People Stargazing at a Single Site (Canberra) and Most People Stargazing Across Multiple Sites in a Country (Australia).
Go to http://www.anu.edu.au/events/mt-stromlo-observatory-world-record-night for more information.

Not in Canberra?
No problems.
There are more than 40 sites registered to take part in the attempt to break the World Record for Most People Stargazing Across Multiple Sites in a Country.
Go to http://rsaa.anu.edu.au/world-record-stargazing to learn more.

Haven't got a telescope? Bring binoculars along instead (they will still count for stargazing!).

UPDATE 23/8/2015
1,869 people braved the cold weather in Canberra to set a new Stargazing record surpassing the previous record of 649 by more than 1,000 people!

A second world record was being attempted for the most people stargazing at multiple sites around Australia, and while estimates of around 10,000 people have been suggested which would beat the previous record of 3,007, we are still waiting for exact numbers and confirmation.

Why Study Science?

Listen to four of the world’s most eminent physicists discuss and deliberate on the biggest challenges facing the science community today.

• Professor Steven Chu was the co-recipient of the 1997 Nobel Prize for Physics. He has devoted his recent scientific career to the search for new solutions to our energy and climate challenges. 
• Professor Schmidt was jointly awarded the 2011 Nobel Prize in Physics for the discovery of the accelerating Universe.
• Professor Lawrence Krauss is theoretical physicist and the author of several bestselling books, including The Physics of Star Trek and A Universe from Nothing. He is an advocate of scientific scepticism, science education and the science of morality.
• Professor Lisa Randall studies theoretical particle physics and cosmology at Harvard University. Her research connects theoretical insights to puzzles in our current understanding of the properties and interactions of matter.

The podcast is about 1.5 hours, but you can select parts of it to listen to.

There is a very nice discussion of what is meant by "good science", there is also some very interesting discussion on "accidental discovery", "experiment to "prove" or "disprove" theory, and the importance of acknowledging that science is not an "absolute" but rather about belief in the "truth" of a scientific theory based on statistical probabilities.

https://soundcloud.com/experience_anu/when_does_science_matter

Drawing the Line of Best Fit

You've got a table of experimental data.
You've plotted the data on a graph.
Now, how do you draw a line of best fit?
Why should you draw a line of best?

AUS-e-TUTE has just added new resources that answers these questions and helps you draw the line of best for your data by giving you a tool to use which makes the whole process as easy as clicking a button!

Visit http://www.ausetute.com.au and click on the Line of Best Fit link.

Chemistry in Eclipses

The 14th November 2012 excites students of physics and those interested in astronomy. This is the date of a total eclipse of the sun. The area of totality will pass over northern Australia, from east of Darwin in the Northern Territory to the Cape York Peninsula of Far North Queensland, turning morning into darkness. The rest of Australia will see a partial eclipse.

But why would chemists get excited about a solar eclipse?

The story begins more than 200 years ago ...

Gaps in the Solar Spectrum?

In 1802 an English Chemist, William Hyde Wollaston, was the first person to record the appearance of a number of dark lines in the emission spectrum of light from the sun.

In 1814, German physicist Joseph von Fraunhofer began measuring the wavelengths of over 570 of these lines.

Fingerprinting the Sun

Robert Gustave Kirchhoff and Robert Bunsen, developed a better prism-based spectroscope and observed that the spectral lines emitted by a gas occurred at the same wavelength as the absorption lines observed when incandescent light from Bunsen's burner shone through the same gas heated at the same temperature.

Then Kirchhoff,  proposed the laws of spectroscopy which bear his name:

1. A hot solid object produces light with a continuous spectrum
2. A hot tenuous gas produces light with spectral lines at discrete wavelengths (an emission spectrum)
3. A hot solid object surrounded by a cooler tenuous gas produces light with an almost continuous spectrum with gaps at discrete wavelengths (an absorption spectrum)

A star, like the sun, will create an absorption line spectrum because the continuous spectrum emitted by the dense, opaque gas that makes up most of the star passes through the cooler, transparent atmosphere of the star.

In 1859, Kirchhoff  demonstrated that all pure substances display their own characteristic spectrum, so it is possible to use the spectrum of elements to identify elements in a mixture, just like each person's fingerprints are unique and can be used to identify them. He proposed  that the lines in the solar spectrum are caused by the absorption of light by elements in the solar atmosphere and set out to identify the elements present in our sun.

New Element Discovered

On the 18th August 1868 there was a total solar eclipse. In India, French astronomer Pierre Janssen observed this eclipse using a spectroscope. He recorded a bright yellow line with a wavelength of 587.49 nm in the spectrum of the solar prominences. The same result was also recorded by British astronomer Norman Lockyer. This line could not be due to sodium, because although sodium produces a bright yellow line (actually more than 1), the wavelength of sodium's 'line' is about 589.3 nm. Lockyer proposed that this line was due to a new element which he called helium after the greek word 'helios' meaning 'sun'.

About 10 years later, Scottish chemist William Ramsay isolated helium on earth ...... but that's another story.

References:

http://eclipse.aaq.org.au/

http://www.csiro.au/en/Outcomes/Understanding-the-Universe/Tracking-spacecraft/History-of-total-solar-eclipses.aspx

Further Reading:

Emission Spectra 

Suggested Study Questions:

1. speed of light (m/s) = frequency (s^-1) x wavelength (m)
   If the speed of light is 3 x 10⁸ ms^-1 calculate:
• find the frequency of the 'yellow line' in sodium's spectrum
• find the frequency of the yellow line for the new element found in the solar spectrum
2.  speed of light (m/s) = frequency (s^-1) x wavelength (m)
   If the speed of light is 3 x 10⁸ ms^-1 calculate:
• wavelength of blue light with a frequency of 6.9 x 10¹⁴ s^-1
• wavelength of red light with a frequency of 4.6 x 10¹⁴ s^-1
  
3. The energy of light emitted, E, is Planck's constant,h, multiplied by the speed of light divided by the wavelength of light emitted. Write a mathematical equation to represent this.
4. Use your equation above to calculate
   • energy of the blue light in question 2 above
   • energy of the red light in question 2 above
5. Complete the following generalizations:
   • The longer the wavelength of light, the ___________ energy it has
   • The shorter the frequency of light, the _________ energy it has.
6. Compare the wavelength of the 'yellow line' in sodium's spectrum and the yellow line for the 'new element'. Which element has
   • the longest wavelength
   • the shortest frequency
   • the most energy
7. Describe the difference in the spectrum of light from the sun as seen in a spectroscope compared to the spectrum of light from a fluorescent light as seen in a spectroscope.
8. Explain the differences between the two spectrum in question 7 above.

Nobel Prize for Work on Graphene

The 2010 Nobel Prize in Physics has been awarded to Andre Geim and Konstantin Novoselov for their "groundbreaking experiments regarding the two-dimensional material graphene".

Graphene is an allotrope of carbon, it is the thinnest and strongest material known. It conducts electricity as well as copper and outperforms all other materials as a conductor of heat. It is almost completely transparent, yet it is so dense that not even helium, the smallest known gas atom, can pass through it.

Geim and Novoselov extracted graphene from a piece of graphite such as is found in "lead" pencils. Using a piece of adhesive tape they obtained a flake of carbon that was just one atom thick, which is the allotrope known as graphene.

Reference:
http://static.nobelprize.org/nobel_prizes/physics/laureates/2010/info_publ_phy_10_en.pdf

Further Reading
Allotropes
Elements

Study Questions:

1. What is meant by the term allotrope?
2. Name two other naturally occurring allotropes of carbon.
3. Draw a table listing the physical properties of both of these allotropes and graphene.
4. Discuss the similarities and differences between these allotropes.
5. Draw a possible structure for graphene.
6. Describe the similarities and differences between the structure for graphene that you have drawn and the structures for the other two allotropes in your table.
7. Using your structure for graphene, explain the similarities and differences between the physical properties of graphene and the other two allotropes.
   

Magic Numbers

Scientists who study the nuclei of atoms apply the "magic" moniker to elements with a certain number of protons or combinations of protons and neutrons. At the magic numbers of 2, 8, 20, 28, 50, 82 and 126 the protons and neutrons are tightly bound together, giving many "magic" elements a high degree of nuclear stability.

Rutgers scientists have been studying an isotope of tin that is "doubly magic", it contains 50 protons and 82 neutrons. Unlike other magic nuclei that are stable, this isotope of tin is very unstable with a half-life of 40 seconds.

The scientists believe that this isotope of tin may be formed in supernova explosions or collisions of neutron stars, and could be part of the process that forms heavier elements.

Reference:
K. L. Jones, A. S. Adekola, D. W. Bardayan, J. C. Blackmon, K. Y. Chae, K. A. Chipps, J. A. Cizewski, L. Erikson, C. Harlin, R. Hatarik, R. Kapler, R. L. Kozub, J. F. Liang, R. Livesay, Z. Ma, B. H. Moazen, C. D. Nesaraja, F. M. Nunes, S. D. Pain, N. P. Patterson, D. Shapira, J. F. Shriner, M. S. Smith, T. P. Swan, J. S. Thomas. The magic nature of ¹³²Sn explored through the single-particle states of ¹³³Sn. Nature, 2010; 465 (7297): 454 DOI: 10.1038/nature09048

Further Reading
Isotopes
Nuclear Decay
Half-life

Study Questions

1. Explain what is meant by the term isotope.
2. What is the atomic number for the tin isotope described in the article above?
3. What is the mass number for the tin isotope described in the article above?
4. What are the names of the elements that have a nucleus containing the following "magic" numbers of protons:
   
• 2
• 8
• 20
• 28
• 50
• 82
5. Explain what is meant by the term half-life.
6. The half-life of the tin isotope described above is 40 seconds.
   
   • If the original sample had a mass of 0.1g, what mass of tin isotope would be present in the sample after 2 minutes?
   • What percentage of the mass of the original sample would be present after 80 seconds?
   
   

Topological Insulators

In an electrical conductor, negatively charged electrons can hop between atoms and move freely in their interior or on the surface. These free electrons are responsible for the generation of electric current. For most metals, electrons in the interior carry most of the current, while surface electrons are only weakly mobile. Some materials, such as glass, have structures that impede electron flow and are called insulators.

A topological insulator is a substance that acts as an insulator in its interior while permitting the movement of charges on its boundary. This can occur when a perpendicular magnetic field is applied, this is known as the quantum Hall effect.
Princeton scientists have discovered a new type of typological insulator, an antimony crystal, which does not require the application of a magnetic field.

Reference:
Jungpil Seo, Pedram Roushan, Haim Beidenkopf, Y. S. Hor, R. J. Cava, Ali Yazdani. Transmission of topological surface states through surface barriers. Nature, 2010; 466 (7304): 343 DOI: 10.1038/nature09189

Study Questions

1. What is required in order for a material to be considered an electrical conductor.
2. Give three examples of good electrical conductors.
3. Give three examples of electrical insulators.
4. In general, what type of substances conduct electricity?
5. In general, what type of substances do not conduct electricity?
6. If electrons are negatively charged, why are atoms considered to be neutral?
7. Why do you think electrons are more free to move within the interior of a material compared to its surface?
   

Art Meets Science

Scientists have been using state-of-the-art gas-chromatography-mass-spectroscopy (GC-MS) to study the organic chemistry of old master paintings in the UK National Gallery's collection. GC-MS has been used to study the characterisation and composition of paint binding media, additions to paint media such as resins, and the composition of old varnishes.

Paint binding media include drying oils such as linseed oil, walnut oil and poppy seed oil. Analysis can show whether the oil was pre-treated by heat-bodying, or thickening, before use by the painter. Added resins can be identified and the state of degradation of the binder assessed. Paintings in other media such as egg tempera can be identified, as well as complex combinations of media.

One such painting studied was The Virgin and Child with an Angel, originally attributed to the Renaissance painter-goldsmith Francesco Francia and dated ~1490. The authenticity of the painting was queried in 1954 when another version of the same painting appeared on the market. In 2009, GC-MS was used to test the paint media and varnish, with the conclusion that the painting in the UK collection was a fake painted in the 19th century.

If you happen to be in the UK during July, you can get to see the results of this research for yourself:
http://www.nationalgallery.org.uk/about-us/press-and-media/close-examination

Now, if you happen to be in Australia, you have only a few days left to get yourself to Federation Square in Melbourne to see Rafael Lozano-Hemmer's amazing "Solar Equation" installation. This incredible piece of physics-meets-art is a simulation of the Sun, 100 million times smaller than the real thing, and compresses the entire 11 year solar cycle including solar flares and sunspots into a few short minutes of visual excitement.
http://www.fedsquare.com/index.cfm?pageID=373

Element 114

About 10 years ago, scientists in Dubna, Russia, reported the observation of element 114. Scientists at Berkeley, USA, and GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt Germany have also reported observations of element 114.

In the most recent GSI experiment using the 120 meter long GSI particle accelerator, the scientists fired calcium ions onto a plutonium coated foil. The nuclei undergo fusion to form the nucleus of the new element. The atoms of element 114 were then separated from the other products of the reaction and identified on the basis of the radiation emitted during their decay. Two different isotopes of element 114 were identified with mass numbers 288 and 289. The measured half-lives are of the order of one second.

Russian reports on the creation of elements up to atomic number 118 are yet to be confirmed.

Reference:
Helmholtz Association of German Research Centres (2010, June 22). Chemical element 114: One of heaviest elements created. ScienceDaily. Retrieved June 23, 2010, from http://www.sciencedaily.com­ /releases/2010/06/100622102347.htm

Study Questions

1. What is the atomic number of the element 114?
2. What are the atomic numbers of calcium and plutonium?
3. Define the term atomic number.
4. Write an equation to represent the fusion of calcium and plutonium.
5. What is meant by the term isotope?
6. For each of the isotopes of element 114 in the article above, give the atomic number, mass number, number of protons, number of neutrons, and number of electrons in an atom of each isotope.
7. Write a nuclear equation for the decay of each isotope of element 114 assuming it undergoes beta decay.
8. Write a nuclear decay equation for the decay of each isotope of element 114 assuming it undergoes alpha decay.
9. What is meant by the term half life?
   
10. If the half-life an isotope of element 114 is assumed to be 1 second, what percentage of the original isotope will be present after 10 seconds?
    

Brownian Motion Machine

In 1912, Marian Smoluchowski proposed a prototype for an engine at the molecular scale which he thought could convert Brownian motion into work. It consisted of a series of vanes mounted on an axis and set into motion by molecular bombardment. An asymmetrical cog ensuring that the axis could only rotate in one direction so that the device could perform work such as lifting a weight.

In 1963, Richard Feynman demonstrated that the second law of thermodynamics would prevent the device from working in a system that was in a state of thermal equilibrium.

Scientists from the University of Twente, the University of Patras in Greece and the Foundation for Fundamental Research on Matter (FOM) have now demonstrated the first working Brownian Motion engine. Using a granular gas, a solid suspended in air that is constantly vibrated, a constant supply of energy is required to maintain the granular gaseous state so that the system is never at thermal equilibrium. Once the vanes of the engine start rotating, they induce a rotating motion in the gas known as a convection roll, which reinforces the movement of the device and allows for virtually continuous rotation.

Reference:
Peter Eshuis, Ko van der Weele, Detlef Lohse and Devaraj van der Meer. Experimental Realization of a Rotational Ratchet in a Granular Gas. Phys. Rev. Lett., 104, 248001 (2010) DOI: 10.1103/PhysRevLett.104.248001

Study Questions:

1. What is brownian motion?
2. What are the three laws of thermodynamics?
3. What is meant by term thermal equilibrium?
   
4. Why would the second law of thermodynamics prevent this device from working in a system that was at thermal equilibrium?
5. List the ways in which a granular gas is similar to compound in the gaseous state.
6. List the ways in which a granular gas is different to a compound in the gaseous state.
   

Heavy Fermions

Scientists are interested in studying heavy fermion behaviour because it could lead to the design of new materials for high temperature super-conductors.

Cornell University Scientists imaging the electronic properties of a material composed of uranium, ruthenium and silicon, have found that the effects of heavy fermions begin to appear as the material is cooled below 55K, and, an even more unusual electronic phase transition occurs below 17.5K.

This phase transition was studied using spectroscopic imaging scanning tunneling microscopy (SI-STM) which measures the wavelength of electrons on the surface of the material in relation to their energy. From the wavelength and energy measurements scientists calculated the effective electron mass and found that these electrons were either very heavy, or, that they were acting like very heavy electrons because they were being slowed down. This suggests that these electrons are interacting with the uranium atoms, that is, acting as particles rather than acting as a wave.

Reference:
A. R. Schmidt, M. H. Hamidian, P. Wahl, F. Meier, A. V. Balatsky, J. D. Garrett, T. J. Williams, G. M. Luke & J. C. Davis. Imaging the Fano lattice to 'hidden order' transition in URu₂Si₂. Nature, 2010; DOI: 10.1038/nature09073

Study Questions

1/ What is a fermion?

2/ What is a super-conductor?

3/ What could high temperature superconductors be used for?

4/ What is the atomic symbol for:

• uranium
• ruthenium
• silicon

5/ To which group of the Periodic Table do each of the following elements belong?

• uranium
• ruthenium
• silicon

6/ Convert the following temperatures in Kelvin to ^oC.

• 55K
• 17.5K

7/ What is the relationship between mass, energy and wavelength that would allow Scientists to calculate the effective mass of an electron?

8/ Why would electrons appear to be heavier if they are slowed down?

Iron and Superconductors

About 100 years ago, scientists discovered materials that could conduct electrons without losing energy to resistance, but, these "superconductors" had to be very cold. The electron-electron repulsion in these low-temperature superconductors was so weak that electrons could overcome it, pair up and move freely.

In 1986, scientists discovered new materials that became superconductors at temperatures above 100K. These high-temperature superconductors were made of layers of copper alloys sandwiched between layers of nonconducting material that were doped with trace amounts of material that could contribute a few extra electrons to the mix. If these materials were not doped with insulating material they did not conduct electricity as the electrons locked themselves at a distance from their neighbours. This locked pattern was named the "Mott localization".

In 2008 a second class of high-temperature superconductors was discovered. These pnictides are iron-based superconductors which are also layered and need to be doped. However, undoped pnictides are not Mott insulators.

Early in 2010, scientists replaced arsenic atoms in one of the intervening layers of a pnictide with slightly smaller phosphorous atoms. This brought the iron atoms a little closer together and further away from the Mott tipping point.

Rice University researchers are now using iron oxychalcogenides which are layered materials like pnictides, but with greater distance between the iron atoms, and this greater distance is enough to push the system into a Mott insulating state.

A better understanding of the behaviour of high-temperature superconductors is essential to future improvements in electric generators, MRI scanners, high-speed trains and other devices.

Reference:
Jian-Xin Zhu, Rong Yu, Hangdong Wang, Liang L. Zhao, M. D. Jones, Jianhui Dai, Elihu Abrahams, E. Morosan, Minghu Fang, and Qimiao Si. Band Narrowing and Mott Localization in Iron Oxychalcogenides La₂O₂Fe₂O(Se,S)₂. Physical Review Letters, 2010; 104 (21): 216405 DOI: 10.1103/PhysRevLett.104.216405

Graphane and Quantum Dots

Graphene is a honeycomb-like form of carbon that is just one atom thick. Graphane is produced when hydrogen atoms are added to both sides of the graphene matrix, making graphane an insulator.

Rice University scientists have discovered that the strategic extraction of hydrogen atoms from a two-dimensional sheet of graphane opens up hexagonal spaces of pure graphene that look and act like quantum dots. Quantum dots interact with light and magnetic fields in unique ways and can be used for chemical sensors, solar cells, medical imaging and nanoscale circuitry.

Reference:
Abhishek K. Singh, Evgeni S. Penev, Boris I. Yakobson. Vacancy Clusters in Graphane as Quantum Dots. ACS Nano, 2010; : 100513111745088 DOI: 10.1021/nn1006072

Scientists See in the Dark

Conventional night vision goggles use a photocathode, a cathode ray tube-like vacuum tube made of thick glass, to convert infrared light photons into electrons which are then accelerated under high voltage and driven into a phosphorous screen producing greenish images of objects invisible to the naked eye in the darkness.

University of Florida scientists have produced an imaging device that replaces the photocathode with several layers of organic semiconductor thin film materials. The photodetector is connected in series with an LED. Infrared light photons are converted into electrons in the photodetector which are then injected into the LED which generates visible light. This imaging device would be light-weight and inexpensive to produce since it could be made using the same equipment currently used to produce laptop screens and flat-screen TVs. This new night-vision technology could be used on mobile phones, car windshields, even standard glasses.

Do Young Kim, Dong Woo Song, Neetu Chopra, Pieter De Somer, Franky So. Organic Infrared Upconversion Device. Advanced Materials, 2010; DOI: 10.1002/adma.200903312