Transcript Slide 1
Magnetic field points into screen From these observations alone, what definite conclusions can be made? a s are positively charged, bs negative. Positive charged particles headed toward the earth from space, would tend (at mid-latitudes) to reach the surface coming down from the A. North B. South C. East D. West E. split East and West The Fantastic Four ® ©1996 Marvel Comics 1900 Charles T. R. Wilson’s ionization chamber Electroscopes eventually discharge even when all known causes are removed, i.e., even when electroscopes are •sealed airtight •flushed with dry, dust-free filtered air •far removed from any samples of radioactivity •shielded with 2 inch thick blocks of lead! seemed to indicate an unknown radiation with greater penetrability than x-rays or radioactive a, b, or rays Speculating they might be extraterrestrial, Wilson ran underground tests at night in the Scottish railway, but observed no change in the discharging rate. 1909 Jesuit priest, Father Thomas Wulf , improved the ionization chamber with a design planned specifically for high altitude balloon flights. A taut wire pair replaced the gold leaf. This basic design has became the pocket dosimeter radiation lab workers carry to record their total exposure to ionizing radiation. 0 1911-12 Austrian physicist Victor Hess, of the Vienna University, and 2 assistants, carried Wulf ionization chambers up in a series of hydrogen balloon flights. • taking ~hour long readings at several altitudes • both ascending and descending • radiation more intense above 150 meters than at sea level • intensity doubled between 1000 m to 4000 m • increased continuously through 5000 meters Dubbed this “high” level radiation Höhenstrahlung Hess lands following a historic 5,300 meter flight. August 7, 1912 National Geographic photograph In 1936, Hess was awarded the Nobel prize for this discovery. Electroscopes became so robust, data could be collected remotely (for example retrieved from unmanned weather balloons) 1924 Walter Bothe and Geiger use multiple Geiger counters to establish the tracks followed by electron beams 1928-29 Bothe and Werner Kolhörster build Geiger telescopes and announce that cosmic “rays” contain charged particles 1927-28 Jacob Clay from Genoa to the Dutch colony of Java •ionization intensity drops ~6% •minimum at magnetic equator 1929 Bothe & Kolhörster •suggest Clay’s Lattitude Effect was due to •deflection by earth’s magnetic field •primaries are charged • inspired by the Norwegian mathematician Carl Størmer’s calculations explaining colleague Kristian Birkland’s theory of the aurora • Birkland experimented with electron beams and a phosphorous-painted globe of lodestone 1930-33 Arthur Compton (University of Chicago) conducts a worldwide sea- and mountain-level lattitude survey of cosmic ray intensities and confirms the Latitude Effect. The 4 curves correspond to 4 seasons. Physical Review 52 [1937]:p.808 1933-35 Thomas Johnson (of the Carnegie Institute) Bruno Rossi (Italy) independently mount Geiger counter telescope arrays to test for an east-west asymmetry predicted by Georges Lemaître (Belgian) Although cosmic rays do come “from all directions”, at high altitudes near the equator the intensity is higher coming from the West than from the East! 1939 Johnson speculates primaries may be protons! Although cosmic rays do come “from all directions”, at high altitudes near the equator the intensity is higher coming from the West than from the East! 1939 Johnson speculates primaries may be protons! Cosmic ray strikes a nucleus within a layer of photographic emulsion 50mm Definite evidence for the celestial generation of Cosmic Rays came from fortuitous timing of a few high altitude balloon studies during some spectacular solar flares. Unusual increase in cosmic ray intensity associated with an intense solar flare observed February 28, 1942 the same sunspot associated with this flare erupts again March 7, 1942 Similarly the June 4, 1946 solar prominence is followed by another eruption July 25, 1946 and the solar flare event of November 19, 1949 is also captured by airborne cosmic ray instruments each accompanied by a Sudden Ionospheric Disturbance which interrupts radio communications on earth What is the world’s most abundant element? CRUSTAL ABUNDANCE OF THE ELEMENTS (by % weight) O 46.6 Silicon Si 27.7 Aluminum Al 8.1 Iron Fe 5.0 Calcium Ca 3.6 Sodium Na 2.8 Potassium K 2.6 Magnesium Mg 2.1 Subtotal 98.5 Titanium Ti 0.4 Hydrogen H 0.1 Phosphorus P 0.1 Manganese Mn 0.1 Sulfur S 0.05 Carbon C 0.03 Total 99.3 Oxygen Average composition of clean, dry air at the Earth's surface Symb ol Molecul ar Weight Molecul ar fraction Fraction by mass Nitrogen Oxygen Argon Carbon dioxide Neon Helium Methane Krypton Nitrous oxide Hydrogen Ozone N2 O2 Ar CO2 28 32 40 44 78.09 % 20.95 % 0.93 % 320 ppm 75.5% 23.2 % 1.3 % 486 ppm Ne He CH4 Kr N2O H2 O3 20 4 16 84 44 2 48 18 ppm 5.2 ppm 2.9 ppm 1.1 ppm 0.5 ppm 0.5 ppm 0.01 ppm 12 ppm 0.7 ppm 1.6 ppm 3.2 ppm 0.8 ppm 0.03 ppm 0.02 ppm Water, moisture H2O 18 - Constituent - Source: Garrels, MacKenzie and Hunt: Chemical cycles. 1975 Distribution of Elements in the Human Body (by weight) Element Atomic no. Percentage Role oxygen 8 65.0 cellular respiration, component of water carbon 6 18.5 basis of organic molecules hydrogen 1 9.5 component of water & most o rganic molecules, electron carrier nitrogen 7 3.3 component of all proteins and nucleic acids calcium 20 1.5 component of bones and teeth, triggers muscle contraction phosphorus 15 1.0 component of nucleic acids, important in energy transfer potassium 19 0.4 min positive ion inside cells, important in nerve function sulfur 16 0.3 component of most proteins sodium 11 0.2 main positive ion outside cells, important in nerve function chlorine 17 0.2 main negative ion outside cells magnesium 12 0.1 essential component of many energy-transferring enzymes iron 26 trace essential component of hemoglobin in the blood copper 29 trace component of many enzymes molybdenum 42 trace component of many enzymes zinc 30 trace component of some enzymes iodine 53 trace component of thyroid hormone Solar system masses Sun 1.981030 kg Jupiter 1.901027 kg Earth 5.981024 kg Absorption “lines” • First discovered in spectrum of Sun (by an imaging scientist named Fraunhofer) • Called “lines” because they appear as dark lines superimposed on the rainbow of the visible spectrum Sun’s Fraunhofer absorption lines (wavelengths listed in Angstroms; 1 A = 0.1 nm) The Solar Spectrum Emission line spectra Insert various emission line spectra here Emission line images Green: oxygen; red: hydrogen (blue: X-rays) Planetary nebula NGC 6543 Orion Nebula The optical emission line spectrum of a young star The Nuclear pp cycle 4 protons 4He + 6 + 2e 26.7 MeV July 1969 Apollo 11 astronauts trap cosmic ray particles on exposed aluminum foil, returned to earth for analysis of its elemental & isotopic composition. With no atmosphere or magnetic field of its own, the moon’s surface is exposed to a constant barrage of particles. March 3, 1972 Pioneer 10 launched -on its flyby mission, studies Jupiter's magnetic field and radiation belts. December 1972 Apollo 17’s lunar surface cosmic ray experiment measured the flux of low energy particles in space (foil detectors brought back to Earth for analysis. October 26, 1973 IMP-8 launched. Continues today measuring cosmic rays, Earth’s magnetic field, and the near-Earth solar wind from a near-circular, 12-day orbit (half the distance to the moon). October 1975 to the present GOES (Geostationary Orbiting Environmental Satellite) An early warning system which monitors the Sun's surface for flares. 1977 The Voyager 1 and 2 spacecraft are launched. Each will explore acceleration processes of charged particles to cosmic ray energies. August 31, 1991 Yohkoh spacecraft launched - Japan/USA/England solar probe - studied high-energy radiation from solar flares. July 1992 SAMPEX (Solar Anomalous and Magnetospheric Particle Explorer) in polar orbit. By sampling interplanetary & magnetospheric particles, contributes to our understanding of nucleosynthesis and the acceleration of charged particles. July 1992 IMAX (Isotope Matter-Antimatter eXperiment) balloonborne superconducting magnetic spectrometer measured the galactic cosmic ray abundances of protons, anti-protons, hydrogen, and helium isotopes. August 25, 1997 Advanced Composition Explorer (ACE) was launched! Element Atomic Number (Z) Primary Solar System Cosmic Ray Composition Flux (relative number of atoms) (particles/m-2 sec) Hydrogen (H) 1 1.00 640 Helium (He) 2 6.8 10-2 94 2.6 10-9 1.5 Lithium, beryllium, boron Carbon, Nitrogen, Oxygen 1.2 10-3 Iron (Fe) All heavier atoms 26 6 3.4 10-5 0.24 1.9 10-6 0.13 Cosmic ray strikes a nucleus within a layer of photographic emulsion 50mm A 1019 eV Extensive Air Shower 100 billion particles at sea level 12 km 6 km 6 km 89% photons 10% electrons ~1% muons The Cosmic Ray Energy Spectrum Cosmic Ray Flux (1 particle per m2-sec) (1 particle per m2-year) (1 particle per km2-year) Energy (eV) Refrigerator cold CO2 bubble (887 mph) 0.02 eV Room temperature nitrogen N2 (1160 mph) 0.03 eV Atoms in sun’s MILLION DEGREE surface 0.50 eV Energy given to each single electron when accelerated by AA battery 1.5 eV Electrons accelerated by your television picture tube (traveling ~1/3 speed of light) 30,000 eV Fermi National Lab’s high energy protons 1,000,000,000,000 eV Recall: 1 joule = 6.2 x 1018 eV Superball bounced over your house 4 x 1017 eV Pitched baseball 4 x 1020 eV Slammed hockey puck 1 x 1021 eV The highest energy Cosmic Rays are SUBATOMIC particles carrying the energy of MACROSCOPIC objects! 4 x 1021 eV = 60 joules The Cosmic Ray Energy Spectrum FERMILAB’s protons Bounced Superball Pitched baseball Hockey Puck Energy (eV) Two possible sources of cosmic rays Colliding galaxies Active galactic nucleus GZK Cutoff 1966 - K. Greisen - G.T.Zatsepin & V.A.Kuz’min showed the recently discovered cosmic microwave background radiation (CMBR) effectively makes the universe opaque to sufficiently high energy cosmic particles. GZK Cutoff 1966 - K. Greisen - G.T.Zatsepin & V.A.Kuz’min p For example: p *+0 p ++ n and similar resonances yield attenuation lengths mere 10s of Mega parsecs for cosmic ray protons with E>1019 eV. Center of (our) Virgo supercluster is approximately 20 Mpc away All E>1019 eV primaries must originate within 100 Mpc of the earth AGASA Energy [eV] ICRC2001 news AGASA: 717 HiRes: 7 2 events above 1020eV