1. In the PHYS181 course at McGill University,the students in PHYS181 were asked to doone final but equally important assignmentabout the things they learned and foundcool throughout the Fall 2011 semester.This is my assignment

2. 1) HISTORY OF THE UNIVERSE2) LIFE OF A STAR3) LIGHT & MATTER4) FIRE RAINBOWS5) PHYSICS OF FLYING6) NUCLEAR POWER7) TIDES8) SURFACE TENSION (i.e., milk and colors!) 3. In 1917, the Dutch astronomer Willde Sitter pointed out to Einstein thathis field equations allow for anevolving and expanding universethrough time. Einstein initiallyrejects this idea. He preferred astatic universe and cooked up a newterm for his field equations (knownas the cosmological constant) thatwould keep things still. But in1929, a turning point came whenHubble discovered that more distantstars were moving away from us.This discovery led to the conclusionthat there must have been somekind of start to the universe-- the BigBang. 4. SOME BEHIND THE SCENES HISTORY~500 BC Pythagoras believed Earth was in motion~300 BC Aristotle proposed model of geocentric universe~300-210 BC Aristarchus of Samus is considered the first person to propose scientific heliocentric model of the universe and to have deduced the correct order of the planets from the Sun~200 AD Ptolemy spoke about circular motions of celestial bodies1543: Copernicus reinforces model of heliocentric universe and accounts for rotation of Earth about its axis to explain the movement of the stars1500s-1800s: constant improvement in the understanding of the mechanics of the universe by some of Historys greatest minds such as Galilei, Brahe, Kepler, Newton, E. DarwinXX-XXI c.: improvements in technologies allowed for closer examination and further study of universe and space at near exponential rates 5. The way we determine distances to stars and other galaxies: parallax d = B/2cos B=distance between two observation points (called baseline B) =angle from one observation point to another to BXX c.: allowed for mapping of galaxy with Harlow-Shapley inverse- square law (1916) with Cepheids M = k/d^2 M=magnitude of light from cepheid k=constant, fixed for cepheid of fixed period d=distance to cepheidEdwin Hubble opened doors for a view of a larger universe Hubbles Law proved expanding universe by showing empirical relationship betweenvelocity of stars moving away from us and their distance 6. frigg.physastro.mnsu.edu/~eskridge/astr101/kauf26_16.JPG T h e f 7. A star is formed in a nebula, whichcondenses into a protostar (densityincreases). Fusion begins and you geta main sequence star (fusion; burnshydrogen). Finally, when there is nomore hydrogen to burn, the starbecomes a red giant (burns helium).After that, there is a variable stagewhere the star starts to inflate andthrow off the extra mass to form aplanetary nebula, while the stuff thatwas the core turns into a white dwarf,eventually becoming a black dwarf,which doesnt give off anymore light. 8. Lagoon Nebulahttp://www.jacanaent.com/Astronomy/!Pages/nebulae.htm 9. In the formation of the star, growth stops when inward force of gravitymatches outward pressure of hot gasses if the initial mass of the protostar is too small, the elements that make itup will never undergo nuclear fusion; this star becomes a brown dwarf for larger-mass stars, as they grow, at some point nuclear fusionoccurs, first combining all the hydrogen into helium stars that burn hydrogen are known as main sequence stars although large stars have more fuel to burn, they need to burn it fasterto maintain equilibrium under the larger influence of gravity, resulting ina shorter lifetime relative to smaller stars a medium-sized star lives only about 50 million years 10. In the Hertzsprung-Russell diagram, a star is represented by a dot. The diagram tells us twothings about the star: its luminosity and its temperature.Hertzsprung-Russell Diagram http://www.le.ac.uk/ph/faulkes/web/images/hrcolour.jpg 11. Light is an electromagnetic wave; andthese electromagnetic waves are createdby electric dipoles. They are related toreflection, transmission and absorption.However, which of these three occurs, andto what degree, depends on thewavelength of the light and the type ofmaterial. If visible light is mostly reflectedor absorbed, the material is opaque and ifvisible light is mostly transmitted, it istransparent. 12. Reflection: when light hits a surface and is reemitted // at the point of collision with the surface of a material, the wave is forced to have a node // the wave will reflect and in its reflection, the wave will be reversed in amplitude relative to the incident wave 2 types of reflection: specular // diffuseSpecular reflection : angle of incidence = reflected angle (i = r)Absorption: when light energy is converted into another form of energy (typically, heat) upon incidence with an opaque mediumTransmission: when light passes through a medium without being absorbed (part of it may or may not be reflected)REFRACTION the speed of light is a constant (c = 3.0*108m/s ), but when light hits some surface, the wavelengths become more compressed because the speed slows // light in a medium such as glass or water moves more slowly than it does in vacuum: speed of wavefronts in vacuum: v=c speed of wavefronts in medium: v=c/n (with n as the refractive index) 13. Like any other rainbow, a fire rainbow is generatedby the refraction of light. This particular type ofrainbow however, refracts in ice crystals of cirrusclouds. It shows an extensive range of colors thatis parallel to the horizon. 14. http://www.aaapoe.net/specialsites/FireRainbow/060619-rainbow-fire_big.jpg 15. Meteorologists and physicists refer to the fire rainbow as a circumhorizonarc, a circumhorizontal arc, lower symmetric 46 degree plate arc or justCHM. This is an extremely rare and consequently, super awesomephenomenon that requires very particular atmospheric conditions. First ofall, clouds have to be cirrus, the Sun needs to be at an elevation angle of58 degrees or more and there have to be just enough ice crystals in thesky. Refraction occurs when light hits a medium, and its transmission intothis medium slows the wavefronts of light which bend towards thenormal Longer wavelength light (red) bends less than shorter wavelength light(blue), which gives rise to a rainbowWhen sunrays enter horizontally oriented crystals of flat hexagon shape,there is a refraction of light at 90 degrees which makes the colors clearlyvisible and well separated. An array of such crystals that refract light in thisway, gives rise to a fire rainbow. source: http://www.buzzle.com/articles/fire-rainbow.html 16. The physics of flying of airplanes is exactlythe same as the physics of flying for birds.The first thing planes need to do is to stay upin the air; they need to constantly fightagainst gravity by creating lift. This happensbecause they need to push air down. Thesecond thing that airplanes consume energyfor is fighting air resistance. This is theassociated force of energy/distance which isdrag. 17. Im sorry for stealing this from your lovelypresentation, but this photo is so much cooler thanthe other ones on Google Images. http://upload.wikimedia.org/wikipedia/commons/f/fe/Airplane_vortex_edit.jpg 18. newtons second law we saw it in the form of F = ma F = MA = (mv) / t ma = constant massmv/t = changing massthe wings basically grab air in a cross sectional area thats a circle with a diameter of the length of the wingspan of the planeit moves forward taking more air until it grabs a cylindrical volume and dumps it downBirds fly in a V formation because theyre taking advantage of the spirals of air at the tips of their wings // they use this upward moving air at the edge to get a little bit extra lift from the bird in front of them // the bird at the front doesnt get the advantage so the birds behind the bird at the front are taking advantage of the vortex of air created by the bird in front of themwhen planes land they put the flaps down in order to increase the surface area of the wings in order to push down even more on the air as a function of time 19. There are two forms of nuclear power: fission,the division of an atom, and fusion. Both ofthese give energy. In one case youre doingthe opposite of the other. The key point is thatfission gives energy if you have a very bigatom (like uranium); when you take this atom,breaking it apart into two smaller atoms givesyou energy. When you take small atoms andyou squash them together, you fuse them intoone bigger atom. This process is calledfusion it also releases energy. 20. E. Rutherford did research in we only know how to harness nuclear decay processes where energy from fission in a nuclei could transmute from one reasonable way version to another the energy from fusion isE. Fermi conducted experiments released in bombs (H-bombs), where hetookuranium, but it has not been harnessed in bombarded it with neutrons // initially, he thought what he got, a controllable way decay products, were a heavierthis is a potential root to element gaining huge amounts of energy Otto Hahn, L. Meitner and F. from the output relative to whatStrassman noticed Fermis work we put inandthey reproduced the completely sustainable form ofexperimentsenergy because all the raw what they found was that whenmaterialsrequiredarethey bombarded the U-235 withpredominantly just hydrogenneutrons, they realized that nuclear atomsfission was taking place 21. Damn Nature, you scary in 1972, a site in Oklo, Gabon was L. Szilard predicteddiscovered where there has been apossibility of a chainnatural chain reaction of uraniumreaction: deposits that had occurred nearlyyou dont just divide one2 billion years agoatom, but the division of one was moderated by naturally occurringatom kicks out a bunch of waterneutrons and those neutronsdivide other atoms, where the the reaction took place a fewneutrons then divide otherhundred thousand years // averagedatoms and so forth. this could100kW of powerlead to some kind of sustainedthis is no longer possible becausecycle that would just keepgetting biggerthe concentration of u-235 in naturally a nuclear chain reaction hasoccurring uranium is now much loweroccurred naturally // in this case(only 0.72%).sea water was the moderator // billions of years ago, thiswith a high enough concentrationconcentration was greater than theof uranium then you get the chain required 3% for a chain reactionreaction process on its own: 22. http://www.youtube.com/watch?v=uStoBFtjy8U&feature=player_embedded 23. The moon is responsible for a large fractionof the tides by causing the motion of thewater. The other source of this is the Sun.There is a complicated pattern in tides thatdepends on the position of the moon and theposition of the sun relative to the moon. Tidesare due to the fact that the gravitational pullon the earth is not uniform. A distribution ofmass will always have some parts that feel astronger pull, because they are closer to theattracting object, and other parts that feel aweaker pull because they are farther away. 24. As the moon goes around the earth, itpulls on the water making it want toresist the force on the moon. Thistransfers angular momentum to speedthe moon up in its orbit. As the moonspeeds up in its orbit, it recedes fromthe Earth little by little, but this forcehas a counteracting force on the Earthcausing its rotation to slow steadily. Asthe tides are being pulled the waterdoesnt flow freely, which slows theearth a bit as a function of time,speeding up the orbit of the moon. 25. Tides make for extremely efficient sources of energy energy is stored in a tide pool (basin) in the form of gravitational potential energy can be retrieved twice per tide cycle (once during the ebb, as water leaves the tide pool; again during flood/flow, as water re-enters tide pool) Amount of energy that can be extracted from barrage in La Rance, France:power = PEgrav. / T PEgrav = mghpower / A = mgh / A . 6h = 2gh^2 / 6*3600 secondsAt La Rance: 2h=8m, A=22.5km^2=2.3*10^7m^2. we estimatethe max power available:power / A ~ 20W/m^2 power ~ 4.6*10^8W = 460Mwpower / 2 = 230MW T = 6hm=mass of extra water displaced in the tidepoolg=acceleration due to gravity (9.8m/s^2) h=distance from low tide to the center of mass water in tidepool m = A(2h)A(2h)=volume of displaced watersource for table: David MacKay. Sustainable Energy- without the hot air. Chapter 14, Tide. 87. 2009. 26. Surface tension occurs at the surface of many liquidmaterials, due to the bondage of certain moleculesto each other. These molecules are bonded bycohesive forces that account for this kind of film atthe surface of the material. Certain bugs have akind of wax coating on their legs with a surfacetension that is higher than that of water. This thencauses the water to bond to itself, and instead ofwetting and drowning the insect, it stays separatefrom it and allows the bug to stay afloat. 27. This is alsowhy water andoil areimmiscible I now knowwhat myvacation plansare thiswinter itshow Jesus didit 28. http://www.youtube.com/watch?feature=endscreen&NR=1&v=22r1zWOYiRM