Foundation Physics is the fundamental understanding of our

Foundation Physics is the fundamental understanding of our Universe • Observation • Exploration • Experimentation • Interpretation 12/26/2021 Phys 217/217 H 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 v as small as a proton which is made up of quarks and gluons v as massive as a black hole with a mass of a billion suns v a biological system v as small as an electron or neutrino with no seen structure 12/26/2021 Physics 217/217 H 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 12/26/2021 Phys 217/217 H 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 -17 m and the other to the edge of the Universe are intimately connected both in physics and experimental techniques. 12/26/2021 Quarknet 06 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? 12/26/2021 Quarknet 06 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) 12/26/2021 Quarknet 06 6

Physical Laws ØPhysics is the same everywhere in the Universe ØPhysics has not changed over the age of the Universe ØEnergy Conservation (Physics is invariant to time) ØMomentum conservation (Physics is the same under space transformation) ØConservation of charge ØConservation of baryon number (protons have a lifetime > 1034 years) ØSymmetry Laws 12/26/2021 Quarknet 06 7

Fundamental building blocks 12/26/2021 Quarknet 06 8

History of the Universe 10, 000, 001 10, 000, 000 Matter Anti-matter 12/26/2021 Quarknet 06 9

Matter and Force Particles Leptons Electric Charge Tau -1 0 Tau Neutrino Muon -1 0 Muon Neutrino 0 Electron Neutrino Electron -1 Quarks Electric Charge Bottom Strange Down -1/3 2/3 Top -1/3 2/3 Charm -1/3 2/3 Up each quark: R, B, G 3 colours Strong Gluons (8) Electromagnetic Photon Quarks Mesons Baryons Nuclei Atoms Light Chemistry Electronics Weak Gravitational Graviton ? Solar system Galaxies Black holes Bosons (W, Z) Neutron decay Beta radioactivity Neutrino interactions Burning of the sun The particle drawings are simple artistic representations 12/26/2021 Quarknet 06 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 12/26/2021 Quarknet 06 11

How do we collect information We need v. The object of interest v. Transmission of information v. A detector to gather the information v. Data analysis v. Interpretation of the data ØInformation can only be carried by particles ØInformation can be affected in transmission ØThe detector has specific characteristics and biases ØData analysis can be biased ØInterpretations have to include all relevant knowledge ØThe simplest interpretation is usually favored. ØTheories are developed which incorporate experimental results and in general are predictive of new phenomena 12/26/2021 Physics 217/217 H 12

Techniques Detector Probe source We can use a probe and see what happens to the probe ØRutherford scattering found the nucleus ØUsing our eyes to look at objects ØUsing light from distant stars to probe the Universe between the distant star and earth. ØUsing lasers for physical and biological systems 12/26/2021 Physics 217/217 H 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. v Objects in the Universe outside of earth v. Nuclear physics v. Use of lasers 12/26/2021 Physics 217/217 H 14

Techniques E = mc 2 We can create new systems v. High energy collisions make new particles v. Florescent biological markers to track biological activity 12/26/2021 Physics 217/217 H 15

Difficulties Correcting the data for experimental biases v Light from a distant star is affected by gravitational forces and the medium such as dust that it passes through. v All detectors are not perfect and corrections need to be made Errors occur v in the transmission of the information v. In the detector v. In the amount of data collected v. Subtraction of backgrounds to obtain the signal 12/26/2021 Physics 217/217 H 16

Interpretation Conclusions are drawn as to the meaning of the data and the physics it reveals It is very important to understand v What assumptions have been made v. Is the analysis unbiased v The dependence on other experimental results v Does the data warrant the conclusions. v What do the conclusions predict 12/26/2021 Physics 217/217 H 17

Technology and devices Forefront physics is also the forefront of technology v. New devices to measure more precisely v. New devices to increase data by many factors of 10 v. 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 v. Lasers v. Medical imaging v. The World Wide Web 12/26/2021 Physics 217/217 H 18

Solar System http: //janus. astro. umd. edu/javadir/orbits/ssv. html http: //www. nineplanets. org/overview. html 12/26/2021 Phys 217/217 H Structure of the Universe 19

Planet orbits 12/26/2021 Phys 217/217 H Structure of the Universe 20

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. 12/26/2021 Phys 217/217 H 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 parsecs. Astronomical Unit (AU): the average separation of the earth and the sun (1. 496 x 10^13 cm). 12/26/2021 Phys 217/217 H 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 M 87 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). 12/26/2021 Phys 217/217 H Structure of the Universe 23

Spiral Galaxy 12/26/2021 Phys 217/217 H Structure of the Universe 24

Typical Spiral Galaxy 12/26/2021 Phys 217/217 H 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 12/26/2021 Phys 217/217 H Structure of the Universe 26

Milky Way Spectra 12/26/2021 Phys 217/217 H Structure of the Universe 27

Sloan digital sky survey 12/26/2021 Phys 217/217 H Structure of the Universe 28

Galaxies and voids This false-color optical map, covering about 4300 square degrees, or 10 percent of the sky, shows percent ofin the sky, shows the distribution in space of some 2 million the distribution space of some 2 million galaxies. The image suggests that galaxies dot the surface of giant interconnected bubbles surrounding immense voids of empty space 12/26/2021 Phys 217/217 H 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 12/26/2021 Phys 217/217 H Structure of the Universe 30

Voids • Voids are the dominant feature and have a typical diameter of ~ 30 Mpc. • 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 124 Mpc. 12/26/2021 Phys 217/217 H Structure of the Universe 31

Composition of the Universe Our current view of the division of energy in the Universe at the present time 12/26/2021 Phys 217/217 H Structure of the Universe 32

Extra solar planets http: //planetquest. jpl. nasa. gov 12/26/2021 Phys 217/217 H 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 12/26/2021 Phys 217/217 H Structure of the Universe 34

Velocity versus distance light v 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 v. The red shift is used to determine velocities HYDROGEN SPECTRUM 12/26/2021 v/c = ((z+1)2 -1)/((z + 1)2 +1) Z = Δλ/λ Phys 217/217 H Structure of the Universe 35

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