Question 1

At present,what is the primary way that the search for extraterrestrial intelligence (SETI)is carried out?

Accepted Answer

The primary way that the search for extraterrestrial intelligence (SETI) is carried out is by using radio telescopes to search for signals from extraterrestrial civilizations. This is because radio waves can travel large distances through space without being significantly affected, making them a good way to communicate across vast distances. Other methods, such as analyzing images of stars or searching for planets around distant stars, may also be used to search for signs of extraterrestrial life, but they are not currently the primary methods used by SETI researchers.

Question 2

Which of the following is not key evidence in support of the idea that all life today shares a common ancestor?

Accepted Answer

The fact that we have identified fossils of the first life forms does not necessarily support the idea that all life today shares a common ancestor. Fossils provide evidence of past life but do not necessarily relate to the common ancestry of all life today.

Question 3

Einstein's theory of relativity tells us that travelers who make a high-speed trip to a distant star and back will

Accepted Answer

According to Einstein's theory of relativity, time appears to pass more slowly for objects in motion relative to those at rest. This means that travelers who make a high-speed trip to a distant star and back would experience time dilation and therefore age less than people who stay behind on Earth.

Question 4

Suppose that Jupiter had never existed,and there was no planet in our solar system between Mars and Saturn.How would we expect this to have affected Earth?

Accepted Answer

Jupiter's gravitational pull helps to shield the inner planets from comet impacts by either deflecting them away from the inner solar system or absorbing them itself. Without Jupiter, Earth would likely have experienced a larger number of comet impacts, which could have affected the development of life on Earth. A and B are incorrect because Jupiter's absence would not have affected Earth's stability or orbit, and D is incorrect because the presence of water on Earth is not directly related to the absence of Jupiter.

Question 5

We are not yet capable of detecting life on planets around other stars.But as our technology develops,our first real chance of detecting such life will probably come from

Accepted Answer

Examining spectral lines from the atmospheres of distant planets can provide information on the chemical composition of the atmosphere, which can reveal the presence of life, such as the presence of oxygen, methane, or other biological markers. This method has already been used to study the atmospheres of some exoplanets and will likely be one of the primary methods for detecting life on distant planets in the future. Options A, C, and D may provide useful information about the planets, but they may not necessarily reveal the presence of life.

Question 6

We have sent several spacecraft on trajectories that will ultimately take them into interstellar space (Pioneer 10 and 11,Voyager 1 and 2,New Horizons).How long will it take these spacecraft to travel as far as the nearest stars?

Accepted Answer

The nearest star to our solar system is Proxima Centauri, which is about 4.24 light-years away. Even at their current speeds, it would take tens of thousands of years for the spacecraft to reach that distance, let alone actually travel to the star itself.

Question 7

When we analyze whether a world is a possible home to life,the key thing we look for is

Accepted Answer

The most important factor in determining if a world is a possible home to life is the past or present existence of liquid water. Water is essential for life as we know it, so the presence of liquid water is a strong indicator that a planet may host life. The other options listed may also be important in certain contexts, but none are as universally important as the presence of liquid water.

Question 8

In general,how does the size and location of a star's habitable zone depend on the star's mass?

Accepted Answer

The size and location of a star's habitable zone depends on the star's mass. The smaller the star, the smaller and the closer-in the habitable zone, because the smaller star gives off less heat and light. Therefore, planets would need to be closer to the star to receive enough heat to maintain liquid water on their surface, making the habitable zone smaller and closer-in.

Question 9

Which of the following best describes the predominant scientific view of the origin of life on Earth?

Accepted Answer

While the origin of life on Earth is still a subject of ongoing research and debate among scientists, the predominant scientific view is that life probably arose naturally under the conditions present on the early Earth. While we may never know precisely how life began, current evidence supports the idea that chemical reactions and natural processes led to the emergence of the first living organisms. Option A is unlikely because there is no evidence to suggest that life migrated from another world. Option C is unlikely because the emergence of life, while still mysterious, is not thought to be miraculous or impossible. Option D is incorrect because while there are many theories about the origin of life, there is no consensus on the precise steps by which life arose.

Question 10

The Sun's habitable zone

Accepted Answer

The habitable zone is the range of distances from a star where liquid water can exist on the surface of a planet, which is a key ingredient for the development of life as we know it. The habitable zone around the Sun extends from someplace a little beyond the orbit of Venus to someplace near the orbit of Mars.

Question 11

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

Accepted Answer

High-mass stars have a short lifetime compared to low-mass stars. Their lifespan is usually less than a billion years, which may not be enough time for life to evolve and thrive on any neighboring planets. Therefore, we do not expect to find life on planets orbiting high-mass stars.

Question 12

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

Accepted Answer

fnow refers to the fraction of planets with civilizations at the present time. It is not about the theoretical possibility of civilization development, the current communication activity of civilizations, or our awareness of all species ever to exist.

Question 13

Why are fossils of early life on Earth more rare than fossils of plants and animals from the past few hundred million years?

Accepted Answer

Early organisms lacked skeletons and hard structures that are most likely to be fossilized, making their fossils rarer than those of organisms with such structures.

Question 14

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

Accepted Answer

Oxygen released by early life forms was quickly absorbed by chemical reactions with surface rocks, preventing it from accumulating in the atmosphere until these reactions slowed down.

Question 15

The "rare Earth hypothesis" holds that Earth-like planets will prove to be quite rare.Which of the following statements best sums up the current status of the debate over this hypothesis?

Accepted Answer

The debate over the rare Earth hypothesis is currently ongoing, and there are arguments and counterarguments that suggest Earth-like planets may be rare or common. Therefore, we do not have enough data to settle the debate definitively. Option A and B are incorrect because the debate is not settled as of now. Option D is a fictional statement and not relevant to the current status of the debate.

Question 16

Why is Europa considered a good candidate for the possible existence of life?

Accepted Answer

Strong evidence suggests that Europa has a deep, subsurface ocean of liquid water, which is considered a key ingredient for the potential existence of life. Furthermore, recent research suggests that the ocean may be geologically active and could have hydrothermal vents that may harbor life forms.

Answer: B
 The Galileo spacecraft found strange seasonal changes on Europa's surface that look like they could be due to life. For instance, certain regions showed unusual changes in coloration and morphology that appeared to be related to the presence of organic compounds. However, this evidence is still inconclusive and requires further investigation.

Answer: C 
 Europa is located within our Sun's habitable zone, meaning it is at a distance from our star where conditions may be suitable for the existence of liquid water and, thus, life. However, this does not necessarily mean that life exists on Europa, as other factors such as its composition and history must also be taken into account.

Answer: D
 Europa does not have a thick atmosphere with a surface pressure greater than Earth. In fact, its atmosphere is very thin and composed mostly of molecular oxygen, with trace amounts of other gases such as carbon dioxide and sulfur dioxide. Therefore, this option is not a good choice for explaining why Europa is considered a good candidate for the possible existence of life.

Question 17

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

Accepted Answer

While there is evidence in the ALH84001 meteorite that some scientists find intriguing, most scientists do not believe it conclusively demonstrates past life on Mars. Furthermore, there is still some debate over whether the meteorite is even from Mars or not. Therefore, the best choice is D: most scientists find the evidence intriguing, but suspect that it can be explained without requiring past life on Mars.

Question 18

Looking for an Earth-size planet around a nearby star (besides the Sun)is like looking for a pinhead located

Accepted Answer

Finding an Earth-size planet around a nearby star is akin to spotting a pinhead thousands of kilometers away due to the vast distances involved in space. Even the nearest stars are several light-years away, making direct observation of such small objects incredibly challenging with current technology.

Question 19

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

Accepted Answer

The answer of If there are other civilizations at present...

Question 20

Which of the following best describes natural selection?

Accepted Answer

Natural selection is the process by which organisms with advantageous traits are more likely to survive and pass on those traits to their offspring. This can improve the fitness of that population over generations.

Quiz 24: Life in the Universe

At present,what is the primary way that the search for extraterrestrial intelligence (SETI) is carried out?