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Renate Loll, Institute for Theoretical Physics, Utrecht University: Physics as a Journey Through Scales from the very large to the very small Lecture for Master Class students, Utrecht, 29 Oct 2010 Things to take away from this lecture The universe stretches over a vast range of length scales each scale is associated with particular physical phenomena. Different parts of physical theory try to describe what happens at different length scales, and formulate physical laws. “Reductionism” has been a very fruitful way of explaining the physical world - understanding the “big” from the “small”. “Fundamental Physics” deals with the very small (quantum physics of elementary particles) and the extremely small (quantum physics of space and time). Let’s get started by increasing your “scale awareness”. The easiest way of measuring extreme length scales is in terms of “powers of ten”: for example, 6 10 m = 1000000 m = 1000 km 102 m = 100 m 100 m = 1 m 10-1 m = 0.1 m -3 10 m = 0.001 m = 1 mm 10-8 m = 0.00000001 m etc. Physical scales (in meters, measured in powers of ten) visible universe 10-35 1026 1021 physics of particle accelerators: quarks, gluons spiral galaxy 10-19 107 10-10 atom Earth 100 us Our journey from the very large to the extremely small begins ... 1026 meters = 100 yottameters The Observable Universe 1025 meters = 10 yottameters Largest Structures in the Universe 1024 meters = 1 yottameter Clusters of Galaxies 1023 meters = 100 zettameters The Virgo Cluster 1022 meters = 10 zettameters The Local Group 1021 meters = 1 zettameter The Milky Way 1020 meters = 100 exameters Our Spiral Arm 1019 meters = 10 exameters The Stars of the Orion Arm 1018 meters = 1 exameter Stars within 50 Light Years 1017 meters = 100 petameters The Nearest Stars 1016 meters = 10 petameters The Oort Cloud 1015 meters = 1 petameter Sol 1014 meters = 100 terameters Our Sun and a few Rocks 1013 meters = 10 terameters The Solar System 1012 meters = 1 terameter Within the Orbit of Jupiter 1011 meters = 100 gigameters Venus, Earth and Mars 1010 meters = 10 gigameters Four Days in July 109 meters = 1 gigameter Earth and Moon 108 meters = 100 megameters Earth 107 meters = 10 megameters North and Central America 106 meters = 1 megameter California 105 meters = 100 kilometers The San Francisco Bay Area 104 meters = 10 kilometers San Francisco 103 meters = 1 kilometer Golden Gate Park 102 meters = 100 meters Japanese Tea Garden 101 meters = 10 meters A Pond with Lily Pads 100 meters = 1 meter The One-Meter Square 100 meters = 1 meter The One-Meter Square 10-1 meters = 10 centimeters A Lily and a Bee 10-2 meters = 1 centimeters A Bee’s Head 10-3 meters = 1 millimeter A Bee’s Eye 10-4 meters = 100 micrometers Pollen 10-5 meters = 10 micrometers Bacterium 10-6 meters = 1 micrometer Virus on a Bacterium 10-7 meters = 100 nanometers A Virus 10-8 meters = 10 nanometers DNA within a Virus 10-9 meters = 1 nanometer The Structure of DNA 10-10 meters = 100 picometers Carbon’s Outer Shell 10-11 meters = 10 picometers The Inner Electron Cloud 10-12 meters = 1 picometer Within the Electron Cloud 10-13 meters = 100 femtometers The Nucleus 10-14 meters = 10 femtometers The Carbon Nucleus 10-15 meters = 1 femtometer A Proton 10-16 meters = 100 attometers Inside the Proton 10-17 meters = 10 attometers Quarks and Gluons 10-18 meters = 1 attometer Within the Reach of the new Particle Accelerator LHC Another 16(!) orders of magnitude below: 10-35 meters - The Planck Scale What is in the empty space between the elementary particles? Physical scales (in meters, measured in powers of ten) visible universe 10-35 1026 what happens at the Planck scale ! GN ! !Pl = c3 ? 1021 physics of particle accelerators: quarks, gluons spiral galaxy 10-19 107 10-10 atom Earth 100 us What we still want to understand: • high-energy theorists are not just interested in the behaviour of matter and particles, but also in the structure of the “empty” space in between • modern quantum field theory gives us a very different picture of empty space (the so-called “vacuum”) • one big challenge is still how to combine the classical theory of general relativity with the quantum nature of the other three fundamental interactions (electro-magnetic, weak and strong). • such a theory of quantum gravity will describe the structure of the vacuum at the very smallest scale, the Planck scale The End Lecture for Master Class students, Utrecht, 29 Oct 2010