Students have already been introduced to LHC, via newspaper articles, and the standard model, via study guides based on www.particleadventure.org. These study guides focus on identification of particles and methods of studying them. The students are 9th graders. This presentation will be divided into 3 class periods; one for the first part--what particle physicists do; one for the second part--the LHC; one for the 3rd part--topics of interest.
Open 2 minute CERN tour video,
They study the identity and interactions of the particles that make up all matter and that control the forces that act on the matter. (Briefly review particles and what is known about them)
Dark matter may be made from exotic particles; Higgs boson may provide particle’s mass; why do we need 3 generations of particles?; super symmetry may help explain gravity; string theory also theorized to help answer questions.
From Kevin McFarland’s (Univ. of Rochester) presentation” What do you mean you don't work at the LHC?" A report from the other frontiers of particle physics,” 5/31/2008, KITP Teacher’s Conference, Santa Barbara, CA Point our placement of topics to students
www.scholarpedia.org/article/Dark_energy “ Observers' view of the accelerating universe. The apparent brightness of supernovae gives a measure of the distance away and time taken for the light to reach us (horizontal axis), while the redshift of their spectra measures the expansion factor or change in average distance between galaxies or any points in space (vertical axis). Points shown in white are supernovae data that led to the 1998 discovery of the accelerating universe: they clearly lie on a curve in the blue region that requires a recent period of acceleration.”
From Kevin McFarland (University of Rochester) KITP presentation 5/31/2008
From Kevin McFarland (University of Rochester) KITP presentation 5/31/2008 ** is hyperlink to antimatter machine video clip. Must have Real Time to view
From Kevin McFarland (University of Rochester) KITP presentation 5/31/2008
From Kevin McFarland (University of Rochester) KITP presentation 5/31/2008
Explain meaning of uncertainty principle; Explain meaning of symbols.
End of day 1: Assign worksheets on scientific notation and metric system.
Go to 2nd animation. Looking lengthwide down accelerator. Translate 7TeV into Reveryday terms so that students will understand amount of energy.
27 km is about 17 miles. Ask students what a vacuum is and introduce them to ways vacuums are quantified
Ask students if they know formula for hydrogen gas. Translate MJ into something students are familiar with. Write our .ooooooo40 m and introduce students to metric notation
Luminosity has specific meanings for different areas of science. Ask students if they have heard of the term and in what context.
The cross section for the LHC is circular, not oval as pictured. Point out that each dot represents a proton
Have students write items in scientific notation on board.
Point out British spelling of ton. How far is 3000 meters--more than 30 football fields.
Superconductivity means that the flow is ~frictionless. Explain Kelvin measurements and the concept of absolute zero
Notice how bunch of protons are focused for the collision.
TOTEM and LHCf are not shown.
Calorimeters measure temperature, or heat energy. When a particle strikes an object and is absorbed by it, the colliding objects heat up. This is expected due to energy conservation.
Beauty quarks have had their name changed.
Trace the points where the proton’s speed is increased. How is this done?
Collecting and analyzing the data is an enormous job. Some detectors dump uninteresting data,
End of 2nd day of presentation. Have students work scientific notation and metric problems.
Point out that Feynman diagrams are useful in communication between scientists. Students aren’t expected to understand them. Essentially, collisionb between gluons and between quarks should produce the Higgs particle. Have students pick out symbols and try to identify the particle represented by the symbol.
Higgs are not expected to be found directly. Scientists will be looking for evidence of products of Higgs particle decay.
James Wells (University of Michigan) KITP presentation 5/31/2008
James Wells (University of Michigan) KITP presentation 5/31/2008
Cosmic rays have been traveling since the big bang. Different colors represent different temperatures.
Where did all the dark matter go?
Explain formula --symbols and what they stand for--to students. Students should become comfortable with seeing mathematical symbos representing operations and letter symbols representing physical quantities and constants.
Explain what a light year is and express things near to us in light years.
But, lifetime of particle in experiment (detector) is a few nanoseconds. Dark matter should have longer life time.
Physicists get paid to think!
Large hadron collider
1LARGE HADRON COLLIDERWhat’s the big deal anyway?Dr. Gail Van EkerenGill St.Bernards SchoolSecondary SchoolFreshman Physics Course
2LHC - the aim of the collider:To smash protons moving at 99.999999%of the speed of light into each other andso recreate conditions a fraction of asecond after the big bang. The LHCexperiments try and work out whathappened. See short introductoryvideo:http://lhc-machine-outreach.web.cern.ch/lhc%2Dmachine%2Doutreach/lhc-video-links.htm
3OVERVIEW OFPRESENTATION• 1. What do particle physicists do?• 2. What are the structure and functionof the parts of the LHC?• 3. What are some LHC topics ofinterest to physicists?
4WHAT DO PARTICLE PHYSICISTSDO?• 1. Review of Standard Model• 2. Unanswered questions• 3. Frontiers of particle physics– a. Cosmic Frontier– b. Intensity Frontier– c. Energy Frontier
5WHAT DO PARTICLE PHYSICISTSDO?"Particle physics is the unbelievable in pursuit ofthe unimaginable. To pinpoint the smallestfragments of the universe you have to buildthe biggest machine in the world. To recreatethe first millionths of a second of creation youhave to focus energy on an awesome scale.”The Guardian• lhc-machine-outreach.web.cern.ch/lhc-machine-outreach/
6WHAT DO PARTICLE PHYSICISTS DO?Review of Standard Modelwww-d0.fnal.gov/Run2Physics/WWW/results/final/NP/N07B/standardmodel.jpg
7WHAT DO PARTICLE PHYSICISTS DO?Some unanswered questionsPeople have long asked,• "What is the world made of?”• "What holds it together?”Physicists hope to fill in their answers tothese questions through the analysis ofdata from LHC experiments
8WHAT DO PARTICLE PHYSICISTS DO?Some unanswered questions• Why do we observe matter and almost no antimatterif we believe there is a symmetry between the two inthe universe?• What is this "dark matter" that we cant see that hasvisible gravitational effects in the cosmos?• Why cant the Standard Model predict a particlesmass?• Are quarks and leptons actually fundamental, ormade up of even more fundamental particles?• Why are there exactly three generations of quarksand leptons?• How does gravity fit into all of this?www.particleadventure.org/frameless/beyond_start.html
9WHAT DO PARTICLE PHYSICISTS DO?Frontiers of Particle PhysicsKevin McFarland’s (Univ. of Rochester) presentdo you mean you dont work at the LHC?" A repother frontiers of particle physics,” 5/31/2008
10WHAT DO PARTICLEPHYSICISTS DO?Frontiers• The Energy Frontier,using high-energy collidersto discover new particles and directly probe thearchitecture of the fundamental forces.• The Intensity Frontier, using intense particlebeams to uncover properties of neutrinos andobserve rare processes that will tell us about newphysics beyond the Standard Model.• The Cosmic Frontier, using undergroundexperiments and telescopes, both ground and spacebased, to reveal the natures of dark matter and darkenergy and using high-energy particles from space toprobe new phenomena.US Particle Physics: Scientific Opportunities A Strategic Plan for the Next Ten Years Report of the Particle Physics Project Prioritization Panel , 29 May 2008 p.7
11WHAT DO PARTICLE PHYSICISTS DO?Cosmic Frontierswww.scholarpedia.org/article/Dark_energy
14WHAT DO PARTICLE PHYSICISTS DO?Intensity FrontiersKevin McFarland(University of Rochester)KITP presentation
15WHAT DO PARTICLE PHYSICISTS DO?Intensity FrontiersKevin McFarland(University ofRochester) KITPpresentation
16WHAT DO PARTICLE PHYSICISTS DO?Intensity FrontiersWHAT ARE QUANTUM FLUCTUATIONS?• Quantum fluctuation = the temporary change in theamount of energy in a point in space,• Due to Werner Heisenbergs uncertainty principle.∆ Ε∆t = h/2π• Conservation of energy can appear to be violated, butonly for small times.• Allows creation of particle-antiparticle pairs of virtualparticles.en.wikipedia.org/wiki/Quantum_fluctuation
17WHAT DO PARTICLE PHYSICISTS DO?Energy Frontiers• Instead of creating many particles in “particlefactories,” physicists collide two streams of particlesat a time, each with extremely high energy• The energy of the collisions in the LHC increase byone order of magnitude the energies in previousstudies
18THE STRUCTURE AND FUNCTION OF THEPARTS OF THE LHCOverviewThe Large Hadron Collider (LHC) is located in a circulartunnel 27 km (17 miles) in circumference. The tunnelis buried around 100 m (about the size of a footballfield) underground.It straddlesthe Swissand Frenchborders onthe outskirtsof Geneva..lhc-machine-outreach.web.cern.ch/lhc-machine-outreach/nobelprize.org
19THE STRUCTURE AND FUNCTION OF THEPARTS OF THE LHCOverviewThe LHC is designed to collide two counter rotating beams ofprotons. Proton-proton collisions are foreseen at an energy of 7TeV per beam.• The beams move around the LHC ring inside a continuousvacuum guided by magnets.• The magnets are superconducting and are cooled by a hugecryogenics system. The cables conduct current withoutresistance in their superconducting state.• The beams will be stored at high energy for hours. During thistime collisions take place inside the four main LHC experiments.lhc-machine-outreach.web.cern.ch/lhc-machine-outreach/Animation of collision:http://www-visualmedia.fnal.gov/VMS_Site/gallery/v_animations.html
20THE STRUCTURE AND FUNCTION OF THEPARTS OF THE LHCOverviewLets see what happens to the protons!“The beams are made up of bunches containing billions of protons.Traveling at a whisker below the speed of light they will be injected,accelerated, and kept circulating for hours, guided by thousands ofpowerful superconducting magnets.For most of the ring, the beams travel in two separate vacuum pipes,but at four points they collide inthe hearts of the main experiments, known by their acronyms: ALICE,ATLAS, CMS, and LHCb. The experiments’ detectors will watchcarefully as the energy of colliding protons transforms ﬂeetingly into aplethora of exotic particles.” www.symmetrymagazine.org/cms/?pid=1000095
21THE STRUCTURE AND FUNCTION OF THEPARTS OF THE LHCThe “Racetrack”• Circular with 27 km circumferenceLinear track-run out of “real estate”• 40,000 leak tight pipe junctions• Vacuum: 10-10Torr or 3 million molecules/cm3(sea level-760 Torr)Protons must avoid collisions with other gasmolecules
22THE STRUCTURE AND FUNCTION OF THEPARTS OF THE LHCThe Proton Beam• Sources of protons-bottles of hydrogen gas• 2808 bunches of protons in routine beam• Stored energy of 350 MJ• Beams are focused by magnets into a 40-µm-cross-section• Pt 6 of LHC has beam dumping system• Collimation system keeps beam from meltingmetal
23THE STRUCTURE AND FUNCTION OF THEPARTS OF THE LHCThe Proton BeamWhy is luminosity important?Luminosity determines theprobability of collision“Among the responsibilities of Princeton’steam are the measurement and deliveryof the luminosity to CMS.”Princeton Physics News, vol.2 issue 2,Fall 2006
24THE STRUCTURE AND FUNCTION OF THEPARTS OF THE LHCThe Proton BeamWhat is luminosity?“Luminosity is the number of particles perunit area per unit time times the opacityof the target” en.wikipedia.org/wiki/Luminosity#In_scattering_theory_and_accelerator_physicsCross section of a sample particle beamis pictured. Assume targets arecompletely opaque, with an opacity of 1.
25THE STRUCTURE AND FUNCTION OF THEPARTS OF THE LHCThe Proton BeamWhat is luminosity?L = f n N1N2 whereAf is the revolution frequency (c/27 km)n is the number of bunches in one beam in thestorage ring. (2808 bunches)Ni is the number of particles in each bunch(billions)A is the cross section of the beam (40 µm)
26THE STRUCTURE AND FUNCTION OF THEPARTS OF THE LHCThe Proton BeamWhat is luminosity?• maximum luminosity for LHC: 1034/cm2s• proton cross section: ~20x10-25cm2• 20 collisions in each bunch crossing• 1 bunch crossing every 25 ns• ~1 250 000 000 collisions each second
27THE STRUCTURE AND FUNCTION OF THEPARTS OF THE LHCThe Proton BeamWhat is collimation?Collimation is the use oflenses (magnets in thiscase) to cause the protonbeams to travel parallel toeach other. The bottomdiagram illustratescollimated light.Diagram: http://en.wikipedia.org/wiki/Collimated_light
28THE STRUCTURE AND FUNCTION OF THEPARTS OF THE LHCMagnetsThe finalmegamagnet ofthe LHC wasceremoniallylowered intoplace through aspecial shaft onApril 26, 2007.news.nationalgeographic.com/news/2007/04/images/070430-collider-magnet_big.jpg
29THE STRUCTURE AND FUNCTION OF THEPARTS OF THE LHCMagnets“To help identify the explosion ofparticles produced when protonsare smashed together, particledetectors typically include apowerful magnet. LHCb is noexception. The experiment’senormous magnet consists of twocoils, both weighing 27 tonnes,mounted inside a 1,450 tonnesteel frame. Each coil isconstructed from 10 ‘pancakes’,wound from almost 3,000 metresof aluminium cable.” lhcb-public.web.cern.ch/.../Magnet-en.htmlpublic/Objects/Detecto r/Magnet1.jp g
30THE STRUCTURE AND FUNCTION OF THEPARTS OF THE LHCMagnetsSome Magnet Facts• 58 different kind of magnets• ~93 000 magnets• Superconducting magnets sit in 1.9 Kbath of superfluid helium at atmosphericpressureNot your everydayordinary magnets!www.print.org.nzchemistry.about.com
31THE STRUCTURE AND FUNCTION OF THEPARTS OF THE LHCMagnetsSome Magnet FactsDipole magnets:– cause protons to follow circular path– produce magnetic field 100 000 times earth’s magnetic field– Main budget item– 1232 dipole magnets– 14.3 meters long; 35 tons each
32THE STRUCTURE AND FUNCTION OF THEPARTS OF THE LHCMagnetsSome Magnet Facts• Other magnets– focus proton beam-see diagram– cause resulting particles to curvelhc-machine-outreach.web.cern.ch/lhc-machine-outreach/collisions.htm
33THE STRUCTURE AND FUNCTION OF THEPARTS OF THE LHCDetectors6 areas aroundcircumference thatwill collect andanalyze data•ATLAS•CMS•ALICE•LHCb•TOTEM (minor study)•LHCf (minor study)hepoutreach.syr.edu/.../accel_overvi ew.html
34THE STRUCTURE AND FUNCTION OF THEPARTS OF THE LHCDetectorsA Toroidal LHC ApparatuS (ATLAS)• 46 meters long, 25 meters high, 25 meters wide• Core: Inner tracker detects and analyzes momentumof particles• Outside: Calorimeters analyze energy by absorbingparticles; only muons go through calorimeter• Outside calorimeter: Muon Spectrometer; chargedparticle sensors can detect changes in magnetic field;momentum of muons can be determined• http://atlas.ch/multimedia/html-nc/feature_episode1.html
35THE STRUCTURE AND FUNCTION OF THEPARTS OF THE LHCDetectorsCompact Muon Solenoid (CMS)• Large detector like ATLAS• Inside a large solenoid with magneticfield 100 000 times that of earth
36THE STRUCTURE AND FUNCTION OF THEPARTS OF THE LHCDetectorsA Large Ion Collider Experiment (ALICE)• Collides iron ions to study conditions rightafter big bang• Expect to see ions break apart into quarksand gluons• Time Projection Chamber (TPC) exams andreconstructs particle trajectories• Also has muon spectrometer
37THE STRUCTURE AND FUNCTION OF THEPARTS OF THE LHCDetectorsLarge Hadron Collider beauty (LHCb)• Searches for beauty quarks as evidence ofantimatter• Series of small detectors stretch 20 meters inlength around collision point• Detectors move easily in tiny precise ways tocatch unstable, short-lived beauty quarks
38THE STRUCTURE AND FUNCTION OF THEPARTS OF THE LHCDetectorsTOTal Elastic and diffractive cross sectionMeasurement (TOTEM)Studies luminosity and proton sizeLarge Hadron Collider forward (LHCf)Simulates cosmic rays in controlledenvironment so scientists can develop waysto study naturally-occurring cosmic rays
39THE STRUCTURE AND FUNCTION OF THEPARTS OF THE LHCAccelerators
40THE STRUCTURE AND FUNCTION OF THEPARTS OF THE LHCComputinglcg-computing-fabric.web.cern.ch/LCG-Computing-Fabric/fabric_presentations/overview_docs/tier_model_lhc.BMP
41THE STRUCTURE AND FUNCTION OF THEPARTS OF THE LHCComputing• LHC will produce ~ 15 petabytes (15 millionGigabytes) of data annually.• Data will be accessed and analyzed by thousands ofscientists around the world.“The mission of the LHC Computing Grid (LCG) is tobuild and maintain a data storage and analysisinfrastructure for the entire high energy physicscommunity that will use LHC”Lcg.web.cern.ch/LCG
42TOPICS OF INTERESTHiggs ParticleHIGGS SEEN AT LHC!www.fnal.gov/pub/presspass/press_releases/cdms-result-2008.htmlAlan Walker/AFP/Getty ImagesPeter Higgs, theman for whom theHiggs bosonparticle wasnamed tours theLHC
43TOPICS OF INTERESTHiggs ParticleWhat role does the Higgs Particle Play?Higgs particleinteracts withparticles, thusslowing themdown. Thisresults in energyconverted intomass.Raman Sundrum (Johns Hopkins Univ,KITPTeachers Conference, 5/31/2008
44THE HIGGS MECHANISM1.To understand the Higgs mechanism, imagine thata room full of physicists quietly chattering is likespace filled only with the Higgs field....2. a well known scientist walks in, creating adisturbance as he moves across the room, andattracting a cluster of admirers with each step ...3. this increases his resistance to movement, in otherwords, he acquires mass, just like a particle movingthrough the Higgs field ...4. if a rumour crosses the room ...5. it creates the same kind of clustering, but this timeamong the scientists themselves. In this analogy,these clusters are the Higgs particles.www.pparc.ac.uk/ps/bbs/bbs_mass_hm.asp12345
45TOPICS OF INTERESTHiggs ParticleWhat do we already know about the HiggsParticle (experimentally)?• Precision measurements of electroweak observables exclude aStandard Model Higgs boson mass of 170 GeV/c2 at the 95%confidence level as of August 2008 (incorporating an updatedmeasurement of the top quark and W boson masses)www.physorg.com/news137076565.html,via Wikipedia• The non-observation of clear signals leads to an experimentallower bound for the Standard Model Higgs boson mass of 114GeV/c2 at 95% confidence level.• A small number of events were recorded by experiments at LEPcollider at CERN that could be interpreted as resulting fromHiggs bosons, but the evidence is inconclusive.• Searches for Higgs Bosons (pdf), from W.-M. Yao et al. (2006). "Review of Particle Physics". J Phys. G 33:
46TOPICS OF INTERESTHiggs ParticleHow will Higgs Particle be made at LHC?Feynmandiagrams• Gluonfusionb. Vectorbosonfusionc. Assocprodwith Wd. Assocprod
47TOPICS OF INTERESTHiggs ParticleHow will Higgs Particle be detected at LHC?Products depend on Higgs’ mass.MASS DECAYPRODUCTS>2 top quarks Z bosonsBelow 2 top quarks Bottom quarksMedium range ??Light 2 photonswww.hep.lu.se/atlas//thesis/egede/thesis-node14.html
48TOPICS OF INTERESTDark MatterJames Wells (University of Michigan)KITP presentation 5/31/2008
49TOPICS OF INTERESTDark MatterA PALE BLUE DOTwww.phys.lsu.eduOn October 13, 1994, thefamous astronomer CarlSagan was delivering a publiclecture at his own university ofCornell. During that lecture, hepresented this photo:www.bigskyastroclub.org/pale_blue_dot.htmlEarth islocatedbetweenwhitearrows.
50TOPICS OF INTERESTDark MatterA PALE BLUE DOTwww.phys.lsu.eduThe previous photowas taken byVoyager 1 in 1990as it sailed awayfrom Earth, morethan 4 billion miles inthe distance… Quiteby accident the earthwas captured in oneof the sun’s rays.This picture isanenlargement.Earth can beseen as a tinyblue dot.His speech isincluded at theend of thepresentation.www.bigskyastroclub.org/pale_blue_dot.html
51TOPICS OF INTERESTDark MatterWMAP• The Wilkinson Microwave Anisotropy Probe (WMAP)mission reveals conditions as they existed in the earlyuniverse by measuring the properties of the cosmicmicrowave background radiation over the full sky.• This microwave radiation was released approximately380,000 years after the birth of the universe. WMAPcreates a picture of the microwave radiation usingdifferences in temperature measured from oppositedirections• map.gsfc.nasa.gov/mission/index.html
53TOPICS OF INTERESTDark MatterWMAP-composition of the universeWMAP measures the compositionof the universe. The top chartshows a pie chart of the relativeconstituents today. A similar chart(bottom) shows the composition at380,000 years old (13.7 billionyears ago) when the light WMAPobserves emanated.map.gsfc.nasa.gov/news/index.htmlCredit: NASA/WMAPScience Team
54TOPICS OF INTERESTDark MatterWhat happened to the dark matter?James Wells (University ofMichigan) KITP presentation5/31/2008
55TOPICS OF INTERESTDark MatterVera Rubin• Vera Rubin is an astronomer who has done pioneering work ongalaxy rotation rates. Her discovery of what is known as "flatrotation curves" is the most direct and robust evidence of darkmatter.• Studied outer regions of galaxies because most astronomerswere studying inner regions and she wanted to balance careerand family, so chose seemingly less competitive area.• Throughout education she worked with great physicistsincluding Richard Feynman and George Gamow:– Vassar College AB 1948– Cornell University MA 1951– Georgetown University PhD 1954– Princeton University-would not accept her into astronomy program.Began accepting women in 1975
57TOPICS OF INTERESTDark MatterExisting EvidenceCluster smashup is dark matter proof•Recent Hubble image is ofanother “bullet cluster.”•5.6-billion light yearsaway; further away andolder than earlierdiscovered bullet cluster•Composite image fromoptical and x-raytelescopesImage from Hubble Space Telescope courtesy of NASA, ESA, CXC,M. Bradac (University of California, Santa Barbara), and S. Allen(Stanford University)From National Geographic News,Aug. 27, 2008
58TOPICS OF INTERESTDark MatterExisting EvidenceCluster smashup is dark matter proof•Ordinary matter (pink) slowsdown during collision•Most of cluster’s mass (blue)keeps up speed, passingthrough the visible matter,creating clumps that are movingaway from collision•Astronomers think clumps aredark matter.Image from Hubble Space Telescope courtesy of NASA, ESA, CXC, M. Bradac(University of California, Santa Barbara), and S. Allen (Stanford University)From National Geographic News,Aug. 27, 2008
59TOPICS OF INTERESTDark MatterJames Wells (University of Michigan) KITPpresentation 5/31/2008
60TOPICS OF INTERESTDark MatterOther Confirming Experiments• We could infer dark matter’s existence through the use of thePlanck Surveyor, a satellite which, among other things, plans tolook for gravitational lensing.• The Gamma-ray Large Area Space Telescope (GLAST) will:“Search for signs of new laws of physics and what composesthe mysterious Dark Matter.”• We could also directly detect dark matter using Xenon. TheLarge Underground Xenon Detector is an experiment whereXenon is placed in a cave deep underground, awaiting darkmatter interactions.• www.patrickgage.com/text/article/556/carnegie-mellon-2008-buhl-lecture-dark-matter
63“Pale blue dot”speech by Carl Sagan"We succeeded in taking that picture [from deep space], and, ifyou look at it, you see a dot. Thats here. Thats home. Thatsus. On it, everyone you ever heard of, every human being whoever lived, lived out their lives. The aggregate of all our joys andsufferings, thousands of confident religions, ideologies andeconomic doctrines, every hunter and forager, every hero andcoward, every creator and destroyer of civilizations, every kingand peasant, every young couple in love, every hopeful child,every mother and father, every inventor and explorer, everyteacher of morals, every corrupt politician, every superstar,every supreme leader, every saint and sinner in the history ofour species, lived there on a mote of dust, suspended in asunbeam.www.bigskyastroclub.org/pale_blue_dot.html
64“Pale blue dot”speech by Carl SaganThe earth is a very small stage in a vast cosmicarena. Think of the rivers of blood spilled by all thosegenerals and emperors so that in glory and in triumphthey could become the momentary masters of afraction of a dot. Think of the endless cruelties visitedby the inhabitants of one corner of the dot onscarcely distinguishable inhabitants of some othercorner of the dot. How frequent theirmisunderstandings, how eager they are to kill oneanother, how fervent their hatreds. Our posturings,our imagined self-importance, the delusion that wehave some privileged position in the universe, arechallenged by this point of pale light. www.bigskyastroclub.org/pale_blue_dot.html
65“Pale blue dot”speech by Carl SaganOur planet is a lonely speck in the great envelopingcosmic dark. In our obscurity -- in all this vastness --there is no hint that help will come from elsewhere tosave us from ourselves. It is up to us. Its been saidthat astronomy is a humbling, and I might add, acharacter-building experience. To my mind, there isperhaps no better demonstration of the folly of humanconceits than this distant image of our tiny world. Tome, it underscores our responsibility to deal morekindly and compassionately with one another and topreserve and cherish that pale blue dot, the onlyhome weve ever known."www.bigskyastroclub.org/pale_blue_dot.html