Conclusion: The astronomer's model is wrong, and life as we know it exists only on planet Earth.
Why? Astronomers to date have not detected even one planet outside our solar system.
So, because astronomers have not yet detected a planet outside our solar system, it does not exist. But, remember, an absence of evidence that something exists does not prove that something does not exist.
Answer choice (C) states: "Detecting planets outside our solar system requires more sophisticated instruments than are currently available."
This helps weaken Clay Moltz's conclusion because it supports the fact that an absence of evidence that something exists does not prove that something does not exist since we are now being told that the instruments needed to detect planets outside our solar system are not currently available.
So, we cannot detect them because we do not have the right instruments as opposed to because they do not exist.
Hope that helps! Please let us know if you have any other questions.
