Saved Groups Lecture 2 – SETI: A Human Perspective

What is the Fermi Paradox?

The apparent contradiction between the high estimated probability of extraterrestrial civilisations existing and the complete lack of evidence for them.

What are the two conditions that make the Fermi Paradox a true paradox?

Intelligent life is not rare, AND it is capable of colonising the Universe.

What are two 'obvious ways out' of the Fermi Paradox?

1) Intelligent life is rare, or 2) The resources needed to sustain it are in short supply.

What human-caused and natural events could limit the lifetime of a civilisation?

Human-caused: nuclear war, climate destruction. Natural: asteroid/comet impacts, supernovae, supervolcano eruptions.

What are the two methods used to study the origins of life?

1) Hypothesis-driven - recreating possible scenarios in the laboratory. 2) Discovery science - seeking examples in nature that provide clues.

Why is understanding life's origins on Earth important for astrobiology?

It allows us to compare conditions on Earth with conditions elsewhere and estimate the probability of life existing beyond Earth.

Why is Earth's fossil record insufficient to fully explain how life began?

There are no fossil records for the first 0.5-1 billion years of life on Earth.

When did the Earth and Solar System form, and when did simple cells first appear?

Earth formed ~4.6 billion years ago. Simple cells (prokaryotes) appeared ~3.6 billion years ago.

When did simple animals first appear, and when did modern humans appear?

Simple animals ~600 million years ago. Modern humans only ~300,000 years ago.

What is radiometric dating used for?

Measuring the ages of rocks and fossils.

What is the Copernican Revolution's significance for astrobiology?

It changed the human perspective by showing that planets are other worlds, raising the possibility of life elsewhere.

What are the steps of the scientific method?

Ask questions → background research → construct hypothesis → test with experiment → analyse results → draw conclusion → report results.

When does a hypothesis become a law?

When it survives testing by a large number of different methods.

What is 'Cosmic Loneliness'?

The feeling arising from awareness of the Universe's enormity and the huge distances between stars.

What is the 'Golden Age of Astrobiology'?

A current era where new ideas and technologies are helping scientists from many disciplines work together to answer fundamental questions about life in the Universe.

What does SETI stand for?

Search for Extraterrestrial Intelligence.