Lattimer, AST 248, Lecture 24 – p.1/16 ency in-flip (1420 MHz) and ce-based radios osmic background peeds

Communication by Radio Speed: velocity of light exceeds physical transportationCost s is small compared to space voyages or probes quantum limit; atmospheric absorption eliminated from spa OH lines (1600–1700 Mhz) • • 1. Economy: cost per photon proportional to energy and frequ 2. Freedom from interference: sum of galactic background, c 3. Cosmic guideposts: e.g., “cosmic waterhole” between H sp Advantages: Commonly used bands in the radio spectrum. What determines the choice of communication frequency? Lattimer, AST 248, Lecture 24 – p.2/16 Lattimer, AST 248, Lecture 24 – p.3/16 Green Bank Telescope Largest fully steerable dish

Radio Telescopes Grote Reber, first parabolic dish Wheaton, IL 1937 Lattimer, AST 248, Lecture 24 – p.4/16 VLA - Very Large Array Socorro, New Mexico

Radio Telescopes Arecibo Radio Telescope Largest single-aperture telescope Lattimer, AST 248, Lecture 24 – p.5/16

Communication by Radio Sources of interference. “Total” is the sum. ndpass, Lattimer, AST 248, Lecture 24 – p.6/16 lion million 0 MHz = 301 y in interstellar e bandpass admits aused by Doppler ndpass (channel width). . range − Bandpass Frequency

Communication by Radio medium. In window from 1000channels MHz of to .1 100,000 Hz MHz, width.shifts there Also due are must to 1 consider relative mil frequency velocities drift of c home and alien planets. An optimum receiver has bandpass equal to signal’s. Too larg Narrower signal of given power hasNumber higher of signal-to-noise. channels = Minimum bandpass width of about 0.1 Hz set by electron densit extraneous noise. Too small bandpass excludes some signal. The cosmic waterhole alone hasMHz. frequency With range 1 1721 MHz MHz bandpass, -number number 142 of of channels channels = = 301 301. million. With 1 Hz ba • • • Signal and Noise, Bandpass Need to select particular frequency (channel center) and ba Lattimer, AST 248, Lecture 24 – p.7/16 phisticated d SETI. ervatory in 1960 nd 1959, and later taken over their own signals. la Tesla (1856 - d in 1986 by ’s using the first civilizations would use , META II and BETA. pt was made to send a loped AC as an energy ntic radio s from Martians. Eridanii, two solar-like stars about 12 ǫ Ceti and τ

History of SETI delivery system. Both felt they were receiving radio signal communications. Tesla invented fluorescent lights and deve developed the idea of the cosmic waterhole hypothesis, that Early pioneers were Guglielmo Marconi (1874 - 1937) and Niko Giuseppe Cocconi and Philip Morrison began modern SETI arou Separately, Frank Drake began using the Green Bank Radio Obs In 1963, NASA funded a SETI program at Ohio State Univeristy, NASA developed a small SETI program in 1971, and developed so In 1979, Berkeley launched a SETI project SERENDIP, replace In 1980 the US Planetary Society wasProject founded Sentinal and was has started supporte at Harvard and MIT in early 1980 1943), Marconi made radio practical and sent first transatla the hydrgen spin-flip frequency of 1420 MHz as a guidepost for to search for radio signals from by the University itself. radio technologies to search for it. In 1974 a symbolic attem SERENDIP II. These were followed by SERENDIP III, IV and V. multi-channel analyzers. This was followed by project META message to other stars from Arecibo. light-years away (Project Ozma). • • • • • • • • Lattimer, AST 248, Lecture 24 – p.8/16 ellite TV dishes rving Program, in iameter. roject Phoenix at erkeley and the nd another site. als from multiple e. bservations using r more Gregorian radio his is being continued

History of SETI the SETI Institute. 1992. Since then work has continued with private funding as P into radio telescopes to run an all-sky survey for signals. T SETI Institute. It supports amultibeaming large and number DSP of technology simultaneous to o sort out individual sign Congress cancelled the NASA program, called Microwave Obse The SETI League was formed in 1994 and converted backyard sat SETI@HOME began at Berkeley in 1999. The first part of the Allen Telescope Array started in 2007 by B Broadcast of local communications on worldSignals where used aliens for liv communication between alien’s homeIntentional world signals a or beacons under Project Argus as a complement to Project Phoenix. directions and dishes. Full arraydishes, planned each to 6.1 consist m of diameter, 350 equivalnt o to a single dish 114 m d • • • • • • • Signal Categories Lattimer, AST 248, Lecture 24 – p.9/16 y basis.

Eavesdropping Eavesdropping: Detection of “stray” radioextraterrestrials. signals from Left: “Leakage” of radio waves from the surfaceRight: of Simulated the pattern Earth. of radiation that repeats on a dail Lattimer, AST 248, Lecture 24 – p.10/16 . ncy , eam e. es, i.e., ls. orth a

Decoding a Signal and what bandpass, we still need to decode the signal. Assuming we figure where in the sky to look, at whichLarge frequency number of ways to encode a signal: amplitude and freque There is an advantage in2-dimensional conveying patterns information of using black/white pictur bits. “A picture is w modulation, for example. Simplest choicecontaining is bits to of use information a which pulsed is b repeated at interva thousand words”, and we don’tTwo know prime what numbers the for words the mean dimensionsthat anyway is a an data obvious stream way containing to that show number of bits was a pictur • • • Lattimer, AST 248, Lecture 24 – p.11/16 e 5 atoms in the presents the composed of 1679 f each number. ative size of each 2.6 cm, the llion shown to the representation of 6, 7, 8 and 15, ir origin. as 73 columns of 23 ion) representing the uman. ng is unambiguous. ctural arrows and the cm=306 m). On each side are “architectural” 6 . 12 × 2430

Decoding the M13 Message bits arranged into 23 columns of 73 bits each. If it is decoded monomers deoxyribose sugar, phosphate and bases in DNA. planet. The Earth is displaced toward the human, showing the The radio message beamed to globular cluster in Hercules was The top rows show binary counting withNext an is error a bit single at block the containing end the o sequence of numbers: 1, Next are 12 groups of 5 numbers, each being the numbers ofThe thes next central vertical clump is a long number (about 4 bill His/her height is given as 14 units, indicated by the archite The total population of humans is indicated by the number 4Then bi comes a pictograph of the Solar System with the crudeBelow rel this is a pictograph of theThe radio center telescope. of the lowest rows contain the number 2430 which re bits each it appears jumbled. This indicates that the decodi representing the elements of life: H, C, N, O and P. number of nucleotides in DNA.the It double is helix surrounded structure by which a points graphical to a pictograph of anumber h 14 on the human’swavelength right-hand of side. the The radio length message. unit is 1 left of the human. telescope’s diameter ( arrows to show this is a diameter measurement. • • • • • • • • • • iguous. d could o the present. Lattimer, AST 248, Lecture 24 – p.12/16 length. ent, suggesting andom orbits. search on a e focus mirror ust absorption, ure out what d system. would have to be in roper motions. red over SETI. the direct line of site to see the signal. that a Search for Extraterrestrial Artifacts (SETA) is favo Proposed using lasers as long agoAlthough as lasers 1961. are monochromatic, makingfrequency it to difficult use, to pulsing fig them spreadsA the disadvantage signal is out that in lasers wave are highly directional; Earth Initially thought to be toostudies energy show expensive that and an limited infrared bywould laser d appear pulse tens coupled of with thousands apenetrate as larg for times thousands as of bright light as years. thePulses Sun could an carry information as bits. A system could automatically target aSoviets list, have correcting done for short p optical SETIHarvard-Smithsonian searches. has operated a piggybackconventional optical all-sky SETI survey, and is now buildingBerkeley a is dedicate also conducting optical SETI searches. Interstellar message probes could be cheaper and more effici Lagrangian points are favored parking placesDyson as spheres opposed or to swarms r would beSETA infrared projects luminous were and undertaken unamb as early as 1979 and continue t

Non-Radio SETI Strategies • • • • • • • • • • • • • Optical SETI Probe SETI • • Lattimer, AST 248, Lecture 24 – p.13/16 contact with hysical effects on l sightings of gs of an unidentified around a UFO. or

UFO's object living or inanimate objects. “occupants” in Nocturnal lights Daylight disks Radar-visual sightings Close Encounters of the First Kind—detailed visual sightin Close Encounters of the Second Kind—visual sightings plus p Close Encounters of the Third Kind—these also include visua Close Encounters of the Fourth Kind—where there is physical occupants • • • • • • • Classification Scheme (Hynek) Lattimer, AST 248, Lecture 24 – p.14/16 lien visitations. le as earthly , who probably nterstellar spacecraft, d in time. pacecraft civilizations underscores ions

Evidence a positronic robot, or a phaser spend more time examining the sky than any other groups phenomena does not signify that the remaining 10% are due to a difficulty in deciphering any extraterrestrial communicat Occupants visible to crowds of people. Examination of a device, such as an antigravity machine, an i Indisputable photographic or spectroscopic evidence of a s Enormous distances to other civilizations, both inLack space of an numerous UFO reports in ChinaLack and of India UFO reports by professional and amateur astronomers Government coverup? The fact that 90% of well-documented UFO cases are explainab Previous visits by extraterrestrials? Difficulty in interpreting writings and pictures of ancient • • • • • • • • • • What evidence would beviewpoint? sufficient from scientific Related Issues: d9 Lattimer, AST 248, Lecture 24 – p.15/16 spiracy have ws. Ironic, since rash was a secret e who would have ve been due to a dman (ufologist) ashed weather ame from testimonies, at the time. There is sky. A UP reporter o detect distant nuclear s, first reported as being Just a fe weeks later, a rancher found debris in a pasture near Kenneth Arnold, from a private plane near Mt. Ranier, spotte

Some Case Studies described these as “flying saucers”Arnold and didn’t it describe became them headline asmeteor ne discs swarm at penetrating all. atmosphere. Now thought to ha shiny objects having wings but no tails streaking across the claimed alien occupants were also recovered. All evidence c military balloon experiment from Project Mogul, designed t no evidence for alien recovery.remained How secret could for such 60 a years cover-uphad in con to spite take of part the in hundreds it? of peopl due to a flying disc,balloon. but Nothing quickly came retracted and of replaced this by for 31 a years, cr when Stantonnot Frie hard evidence. Declassified government records say the c explosions. This has been verified by the scientist in charge Roswell Army Air Field. Military personnel recovered debri 1947 - Washington State 1947 - Roswell, New Mexico d dly show Lattimer, AST 248, Lecture 24 – p.16/16 ge of the n England. s, and the patterns orted dating back the matted-down ca plains of Peru, ed, many have been he Egyptian pyramids. gns are getting more idence for this exists. ade only at night. st babies and goblins eping, and returned in g sophisticated to en well-documented that d the abuctees. n to the Mayan pyramids, rcles can be shown to be y beyond the means of es to sleep paralysis. No ially considering the vast Evidence offered consists of ancient drawings that suppose Despite a long history of attacks on farm animals by humans an Geometric patterns usually made in wheat fields, most often i Americans lead in this phenomenon, despite a small percenta

Some Case Studies shown to be deliberate hoaxes.complicated It each is year, suspicious hardly that the thetechnology pattern desi from of light-years aliens away, bringin and that the circles are m easily made using boards, ropes and other simple tools; inde Despite the speed with whichwheat, they said appear to and be the inconsistent condition with of trampling, nearly all ci the same state. Actually, such phenomena have often been rep artifacts or sophisticated surgeries have ever accompanie world’s population. Nearly all abuctees are taken while sle to ancient cultures, but therather culprits than then aliens. were Many witches, psychologists gho attribute the stori predators, aliens have often been implicated. But no real ev could easily be costumes. Another often-cited example are t Stonehenge and the stone heads of Easter Island. alien visitors or spacecraft, or ancient wonders apparentl which were certainly not beyond the means of thewhich Nazca is Indian insulting to thesuch ancient structures Egyptian were culture. well It within hassupplies their be of capabilities, slaves espec in the society. Similar arguments pertai ancient cultures. Examples are the giant drawings on the Naz Crop circles Cattle mutilation Abductions Ancient visitations