Exam 19: Life in the Universe

Suppose it turns out that one in 1 million stars has a planet that at some point in its history is home to an advanced civilization. Then the total number of civilizations that have arisen in our galaxy would be closest to .

Which of the following are the best candidates to search for planets that might harbor extraterrestrial life?

If there are other civilizations at present in the Milky Way Galaxy, which statement is almost undoubtedly true?

According to current science, why didn't oxygen begin to accumulate in the atmosphere for more than a billion years after life appeared on the Earth?

What evidence suggests that life arises relatively easily?

According to fossil evidence, how far back in time did life on Earth exist?

Why don't we expect to find life on planets orbiting high- mass stars?

Which of the following gases, which we can detect (if present)in infrared spectra, would be a strong indicator of life on another planet?

The Voyager I and II spacecraft visited the Jovian planets in the 1980s. When will they reach the distances of the nearest stars?

The figure above shows the geological times scale. The Earth's atmosphere has been oxygen rich for

What is the evidence that suggests planetary systems are common in the universe?

How do scientists study the history of life on Earth?

Briefly summarize current knowledge about the term flife in the equation Number of Civilizations = NHP × flife × fcivilization × fnow.

The Kepler mission has searched for Earth- like planets by looking for the dip in the brightness of a star as a (potential)planet transits across it. Why will this technique actually miss the vast majority of planets around the stars it observes?

The requirement of liquid water is the most severe constraint on the development of life.

Which of the following best describes the current status of the debate over evidence for life in the Martian meteorite ALH84001?

Which of the following is not considered a potential solution to the question of why we lack any evidence of a galactic civilization?

Which of the following places is not generally considered a potential home for life in our solar system?

In the Drake equation (Number of Civilizations = NHP × flife × fciv × fnow), what do we mean by fnow?

At about what fraction of the speed of light do today's spacecraft travel?