TOEFL iBT Listening Practice Test 03 Solution & Transcription


Audio Discussion

Narrator: Listen to part of a discussion in a general science class.


Okay. This is a general science course, and as such, the first thing I want you to understand is the scientific method. In your book, the definition of the scientific method is “an organized approach to explaining observed facts, with a model of nature that must be tested, and then modified or discarded if it fails to pass the tests.” So let’s take that apart and talk about it What are observed facts? Anyone?

Student 1: I’ll try.

Professor Okay.

Student 1: Isn’t a fact supposed to be a statement that everyone agrees on?

Professor: So you would say that a fact is objectively true.

Student 1: Yeah. That’s what I mean.


Okay. That sounds good, but what about this … we consider it a fact that the Sun rises each morning and the Earth rotates. But facts like that are not always agreed upon. Look, when we say that the Sun rises each morning, we assume that it is the same Sun day after day- an idea that might not have been accepted by ancient Egyptians, whose mythology taught them that the Sun died with every sunsetand was reborn with every sunrise. Now. let’s consider the case of the Earths rotation ,Well, for most of human history, the Earth was assumed to be stationary at the center of the universe. So, as you can see our interpretations of facts often are based on beliefs about the world that others might not share. Still facts are the raw material that scientific models seek to explain, so it’s important that scientists agree on the facts. How can we do that? 

How about  this… a fact has to be verified, I mean, thafs where the testing comes in. so we have to be able to test a model, but we have to be able to test a fact, too, right?

Now you’re on the right track. In the context of science, a fact must therefore be something that anyone can verify for himself or herself, at least in principle. So. even though the interpretation may be different, some interpretation of the Sun is there every morning, and that can be venfied. Then, a model is proposed to explain the facts. And a model is…

Student 3: … an explanation of the facts.


Right. One the facts have been observed, a model can be proposed to explain them and not only explain what is obvious but also make predictions that can be tested through further observations or experiments Lefs go back to Ptolemy’s model of the universe, which assumed that the Eartti was the center of everything Okay, that was a useful model because it predicted future locations of the Sun, Moon and planets in the sky. However, although the Ptolemaic model remained .n use for nearly 1500 years.’ eventually it became clear that its predictions didn’t quite match actual observations-a key reason why the Earth-centered model of the universe finally was discarded.

Student: So models are discarded when they don’t match the observations.


Exactly. And new models are proposed to explain the tads in a better Of more inclusive way. does a model achieve the status of a theory?

Student 1: Well, I get sometimes me model doesn’t lail. you know, it gets repealed by man, experiments and the, uh. the uh … pre- um. predictions are verified.


So, when a prediction is verified. repeated, then we start lo assume that the model tea valid representation of nature, and when mat happens with many experiments and a number of different researchers, then the model achieves the status of a scientific theory.

Student 2: But ..

Professor: Yes? Jeny?

Student 2: Well, the problem is that theories get discarded, too, don t they? 


Absolutely. Because it isn’t really possible to prove that a theory is true beyond all shadow of a doubt. And that’s good because doubt is a cornerstone of science. Even a well-researched and presented theory should undergo continuous challenges from the scientific community, with further observations and experiments.

Student 3:

I’m sorry. Did we mention the term hypothesisi? Does that fit in with a model or a theory?


Glad you brought that up. A proposed model is often called a hypothesis, and that just means that the scientist is making an educated guess that the model’s predictions will bear up under testing.

Student 3: So a hypothesis is a proposed model.


Right. But let’s put this all together, shall we? Step 1 is observation, the collection of data, that is, observations. Step 2 is hypothesis or a model to explain the facts and to make predictions. Step 3 is additional observations and experiments. And here’s the important part, when the predictions fail, then we recognize that the model is flawed, and we have to revise or discard it, but when the predictions are verified on a consistent basis, then we consider the possibility that we have a true representation of nature and we elevate the model to the status of a theory.

Student: So step 4 is the theory?


Right. But, even then, the theory must undergo step 5… that’s further observations, experiments, and challenges. Okay so far? … Okay. Now for a reality check. In the real world of science, discoveries are rarely made by a process as … as mechanical as the idealized scientific method outlined in your textbook … the one that we just summarized. For example, anyone recognize the name Johannes Kepler?

Student 2: Sure. Didn’t he propose the laws of planetary motion?


He did, in about 1600. But instead of verifying new predictions on the basis of his model, he tested the model against observations that had been made previously. And … and … like most scientific discoveries, Kepler’s work involved intuition, collaboration with others, moments of insight, and luck. And eventually, other scientists made a lot of observations to, uh … verify the planetary positions predicted by his model.

Student 1: Student 2r.

So the Then

Student 2: Go ahead.

Student 1: So the scientific method in the book that’s not really the way it happens a lot of the time?

Okay, let’s put it this way … the scientific method is a process that we need to keep in mind as we do the work of scientists, but we should also understand that it’s an idealized process for making objective judgments about whether a proposed model of nature is dose to the truth. And we should also keep in mind that in the work of scientists, other factors are also brought to bear on those ideal steps in the process.