Listening in the Dark

Transcription

1 Listening in the Dark The search for extraterrestrial intelligence Two possibilities exist: either we are alone in the Universe or we are not. Both are equally terrifying. Arthur C. Clarke

2 Why search for life? To prove whether life is unique To answer scientific questions about the nature of life We may be able to learn from other intelligent life To discover whether we are alone

3 How do we search? Methods for finding life:

4 How do we search? Methods for finding life: Listen for noise pollution Search for intentional communication Look for modification of the Universe Send a message

5 A feeble light in a vast sea Radio waves are a form of light. Thus, they propagate at the speed of light, but also get weaker the farther they travel. Starting brightness Time traveled Distance traveled Speed of light (299,792,458 m/s) Observed brightness Distance traveled

6 A feeble light in a vast sea In 1936, a TV broadcast of Adolf Hitler opening the Berlin Olympics became the first radio signal to leave the Earth. In 1937, that signal was 1 lightyear from Earth. In 2016, that signal is 80 lightyears from Earth, but it is 6,400 times weaker than in 1937.

7 SETI today The Allen Telescope Array is engaged in a search for radio signals of extraterrestrial intelligence. So far, it has found nothing.

8 A cosmic telegram A laser generates a beam of highly-focused light. Lasers require relatively little energy to be extremely bright in a single direction. Lasers are monochromatic, which means they contain light of only one color. Pros A strong signal would be easier to detect Would give exact source of message Message more likely to be unambiguous Cons ET would have to be directly contacting us We d need to know which color to look for

9 Go big or go home A Dyson sphere is a hypothetical structure that encompasses much or all of a star in order to harvest its energy. It s theorized that it may be common for advanced species to construct them. Pros Megastructures give a strong indication of the advanced nature of a species Cons Structures built with our current understanding of materials would block only a little of the star s light The signal of a megastructure is easily confused with a natural process

10 A glimmer in the dark A key human innovation was the development of artificial light. If other species have also developed it, light may still be visible from the nightside of a planet. Pros Would give us information about the behavior of an extraterrestrial species Cons Artificial light is likely extraordinarily dim in comparison to the star The light may not be in the visible spectrum

11 A message for the stars In 1977, NASA launched the Voyager 1 and Voyager 2 spacecraft. Their mission was to explore the outer Solar System for the first time. They also carried a message. Each message was designed to last for a billion years.

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13 Small group discussion You are sending a message to intelligent life in the Universe. You may only include images and sounds. What do you send?

14 Contents of the Golden Record To the makers of music all worlds, all times Sounds Greetings in 55 languages Sounds from nature Wind, birds, volcanos, a train, a kiss 90 minutes of world music Mozart, Chuck Berry, others An hour-long recording of brain waves Images (116) The visited planets Structure of DNA Human anatomy Snowflakes Jane Goodall and chimps Supermarket Taj Mahal Sunset This record represents our hope and our determination and our goodwill in a vast and awesome universe. Jimmy Carter

15 The universal language The principles of mathematics are believed to be constant across the Universe. They may offer a connection between species.

16 How would we know? Explicit contact from another lifeform would require the expression of knowledge unique to intelligent life.

17 Fibonacci sequence The Fibonacci sequence is the sequence of numbers generated by starting with 0 and 1 and adding pairs from there. 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144,...

18 The golden ratio The golden ratio Φ is a number found throughout mathematics and nature. Two numbers are said to be in the golden ratio if: Φ =

19 Pi The ratio of the circumference of a circle to its diameter is called π π =

20 The Kardashev scale The Kardashev scale is a hypothetical classification system for how advanced an intelligent species is. Type 1: The species is capable of harnessing all their host star s energy that strikes their planet. Type 2: The species is capable of harnessing all of their host star s energy Type 3: The species is capable of harnessing the energy of all the stars in their galaxy

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