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Foundation Physics is the fundamental understanding of our Universe •Observation •Exploration •Experimentation •Interpretation 5/9/2017 Phys217/217H Structure of the Universe 1 Experimental Physics: Basic Research The world and the Universe which we inhabit is composed of objects that have mass and are made up of a collection of constituents which are bound together. To understand the Universe we do experiments by observing the physical characteristics of an object or a system. The system can be as small as a proton which is made up of quarks and gluons as massive as a black hole with a mass of a billion suns a biological system as small as an electron or neutrino with no seen structure 5/9/2017 Physics 217/217H 2 Forces Every change in a system is due to forces There are only four forces •Gravitation - very weak •Electromagnetic – Everyday force •Weak – Radioactive decay •Strong – inside the nucleus To understand the Universe we have to understand these forces To understand any object or system we have to use these forces as our tools for exploration. BECAUSE WE HAVE TO INTERACT WITH THE OBJECT 5/9/2017 Phys217/217H Structure of the Universe 3 Physics of the Universe The intellectual thrust of Particle physics, astrophysics and cosmology is to understand our Universe from t = 0 to 13.8 billion years We only have one Universe although some models include speculation about connections to other Universes Elementary Particle Physics – Fundamental building blocks and forces Cosmology – Understanding the history and evolution of the Universe, large scale structure and phenonoma. These two disciplines, one at distances of 10-17m and the other to the edge of the Universe are intimately connected both in physics and experimental techniques. 5/9/2017 Quarknet06 4 The questions What are the fundamental building blocks? What is Dark Energy? Are there extra dimensions? Are there new laws? Do all the forces become one? Why are there so many particles? What is dark matter? What are neutrinos telling us? How did the Universe come to be? Where did the antimatter go? What is gravity? What came before the big bang? Are there other Universes? 5/9/2017 Quarknet06 5 Overall Framework Physics is based on experimental observationswhich are incorporated into theoretical mathematical models which generally make testable extensions and predictions. An analogy I use is that we are completing a very large and detailed painting in which we know a lot detail but much remains to be filled in. Both high precision in small areas and major discoveries in the whole picture. Normally we use as our models and framework the simplest solution that fits all the experimental observations (no aliens) 5/9/2017 Quarknet06 6 Physical Laws Physics is the same everywhere in the Universe Physics has not changed over the age of the Universe Energy Conservation (Physics is invariant to time) Momentum conservation (Physics is the same under space transformation) Conservation of charge Conservation of baryon number (protons have a lifetime > 1034 years) Symmetry Laws 5/9/2017 Quarknet06 7 Fundamental building blocks 5/9/2017 Quarknet06 8 History of the Universe 10,000,000,001 10,000,000,000 Matter 5/9/2017 Anti-matter Quarknet06 9 Matter and Force Particles Leptons Strong Electric Charge Tau -1 0 Tau Neutrino Muon -1 0 Muon Neutrino 0 Electron Neutrino Electron -1 Quarks Strange Down each quark: -1/3 2/3 Top -1/3 2/3 Charm -1/3 2/3 Up R, B, Photon Quarks Mesons Baryons Nuclei Atoms Light Chemistry Electronics Weak Gravitational Electric Charge Bottom Gluons (8) Electromagnetic Bosons (W,Z) Graviton ? Neutron decay Beta radioactivity Neutrino interactions Burning of the sun Solar system Galaxies Black holes G 3 colours The particle drawings are simple artistic representations 5/9/2017 Quarknet06 10 Composition of the Universe Something is providing a gravitational force in galaxies. Something is expanding space Our current view of the division of energy in the Universe at the present time 5/9/2017 Quarknet06 11 How do we collect information We need The object of interest Transmission of information A detector to gather the information Data analysis Interpretation of the data Information can only be carried by particles Information can be affected in transmission The detector has specific characteristics and biases Data analysis can be biased Interpretations have to include all relevant knowledge The simplest interpretation is usually favored. Theories are developed which incorporate experimental results and in general are predictive of new phenomena 5/9/2017 Physics 217/217H 12 Techniques Detector Probe source We can use a probe and see what happens to the probe Rutherford scattering found the nucleus Using our eyes to look at objects Using light from distant stars to probe the Universe between the distant star and earth. Using lasers for physical and biological systems 5/9/2017 Physics 217/217H 13 Techniques We can observe energy emitted by an object either because excess energy has been put into the object as part of the experiment or because the object naturally has excess energy. Objects in the Universe outside of earth Nuclear physics Use of lasers 5/9/2017 Physics 217/217H 14 Techniques E = mc2 We can create new systems High energy collisions make new particles Florescent biological markers to track biological activity 5/9/2017 Physics 217/217H 15 Difficulties Correcting the data for experimental biases Light from a distant star is affected by gravitational forces and the medium such as dust that it passes through. All detectors are not perfect and corrections need to be made Errors occur in the transmission of the information In the detector In the amount of data collected Subtraction of backgrounds to obtain the signal 5/9/2017 Physics 217/217H 16 Interpretation Conclusions are drawn as to the meaning of the data and the physics it reveals It is very important to understand What assumptions have been made Is the analysis unbiased The dependence on other experimental results Does the data warrant the conclusions. What do the conclusions predict 5/9/2017 Physics 217/217H 17 Technology and devices Forefront physics is also the forefront of technology New devices to measure more precisely New devices to increase data by many factors of 10 New devices required to explore new physics Forefront technology either developed for basic research or for commercialization leads to widespread use of new technology in all branches of science, engineering and industry and new devices for everyday use Lasers Medical imaging The World Wide Web 5/9/2017 Physics 217/217H 18 Solar System http://janus.astro.umd.edu/javadir/orbits/ssv.html http://www.nineplanets.org/overview.html 5/9/2017 Phys217/217H Structure of the Universe 19 Planet orbits 5/9/2017 Phys217/217H Structure of the Universe 20 The Milky Way The Milky Way The Milky Way is a gravitationally bound collection of roughly a hundred billion stars. Our Sun is one of these stars and is located roughly 24,000 light years (or 8000 parsecs) from the center. 5/9/2017 Phys217/217H Structure of the Universe 21 Units of distance Light Year: the distance that light travels in one year (9.46 x 10^17 cm). Parsec (pc): 3.26 light years (or 3.086 x 10^18 cm).; also kiloparsec (kpc) = 1000 parsecs and megaparsec (Mpc) = 1,000,000 parsecs. Astronomical Unit (AU): the average separation of the earth and the sun (1.496 x 10^13 cm). 5/9/2017 Phys217/217H Structure of the Universe 22 Distances Some Representative Distances: The Solar System is about 80 Astronomical Units in diameter. The nearest star (other than the sun) is 4.3 light years away. Our Galaxy (the Milky Way) is about 100,000 light years in diameter. Diameter of local cluster of galaxies: about 1 Megaparsec. Distance to M87 in the Virgo cluster: 50 million light years. Distance to most distant object seen in the universe: about 18 billion light years (18 x 10^9 light years). 5/9/2017 Phys217/217H Structure of the Universe 23 Spiral Galaxy 5/9/2017 Phys217/217H Structure of the Universe 24 Typical Spiral Galaxy 5/9/2017 Phys217/217H Structure of the Universe 25 Size of the Milky Way Not shown is the halo which is a spherical region, centered on the nucleus, with a radius of about 50000 light years. This halo contains very old stars, produced early on when the galaxy was still forming. Most of these stars are in vast collections called globular clusters 5/9/2017 Phys217/217H Structure of the Universe 26 Milky Way Spectra 5/9/2017 Phys217/217H Structure of the Universe 27 Sloan digital sky survey 5/9/2017 Phys217/217H Structure of the Universe 28 Galaxies and voids This false-color optical map, covering about 4300 square degrees, or 10 percent of the sky, This false-color optical map, covering about 4300 square degrees, or 10 percent of the sky, shows the distribution in space of distribution in space of some 2 million galaxies. someshows 2 millionthe galaxies. The image suggests that galaxies dot the surface of giant interconnected bubbles surrounding immense voids of empty space 5/9/2017 Phys217/217H Structure of the Universe 29 The Universe within 1 billion Light Years Number of superclusters = 80 Number of galaxy groups = 160 000 Number of large galaxies = 3 million Number of dwarf galaxies = 30 million Number of stars = 500 million billion 5/9/2017 Phys217/217H Structure of the Universe 30 Voids • Voids are the dominant feature and have a typical diameter of ~ 30Mpc. • Voids are very underdense region, δρ/ρ~0.95 • Up to 40% of volume of the universe is occupied by voids • The largest void observed, Bootes void, has a diameter of about 124Mpc. 5/9/2017 Phys217/217H Structure of the Universe 31 Composition of the Universe Our current view of the division of energy in the Universe at the present time 5/9/2017 Phys217/217H Structure of the Universe 32 Extra solar planets http://planetquest.jpl.nasa.gov Kepler Spitzer Hubble The challenges. Planets don't produce any light of their own, except when young. Enormous distance from us. Lost in the blinding glare of their parent stars. Detection • Wobbling of parent star • Variation in light from parent star “Transit Method” • Frequency shift of light from planet as it’s velocity changes “Doppler” 5/9/2017 Phys217/217H Structure of the Universe 33 Red shift, looking back in time The Universe expanded very rapidly in a fraction of a second. Now imagine the Universe 13 billion years ago. All parts of the Universe were in the same state of the beginning of star formation and emitting light. As the light travels toward us at velocity c space is expanding so the distance the light has to travel increases so there is a point that emitted light 13 billion years which has just reached us. c s This light is red shifted because of the expansion of space c = fλ 5/9/2017 Phys217/217H Structure of the Universe 34 Velocity versus distance light v We observe that the light from distant objects is shifted to longer wavelengths, that is toward the red. This shift is due to the expansion of space since the light was emitted The red shift is used to determine velocities HYDROGEN SPECTRUM 5/9/2017 v/c = ((z+1)2 -1)/((z + 1)2 +1) Z = Δλ/λ Phys217/217H Structure of the Universe 35 5/9/2017 Phys217/217H Structure of the Universe 36 5/9/2017 Phys217/217H Structure of the Universe 37 5/9/2017 Phys217/217H Structure of the Universe 38 5/9/2017 Phys217/217H Structure of the Universe 39 5/9/2017 Phys217/217H Structure of the Universe 40 5/9/2017 Phys217/217H Structure of the Universe 41 5/9/2017 Phys217/217H Structure of the Universe 42 5/9/2017 Phys217/217H Structure of the Universe 43 5/9/2017 Phys217/217H Structure of the Universe 44 5/9/2017 Phys217/217H Structure of the Universe 45