Chapter 1 Questions


Question:

Modern cosmology depends upon the scientific method. But aren't there limits to the scientific method? Are there cosmology questions that cannot be answered by science?

Answer:

There are certainly questions that can be asked that presently cannot be answered. Some of these, such as what is the nature of the grand unified theory or quantum gravity, may be answerable. A more subtle question is whether such theories, if formulated, are truly testable. Optimists hope that the universe itself provides tests of these theories; that is, the consequences of these theories must be compatible with the universe as we observe it. For example, some formulations of the grand unified theory are in conflict with the experiments to measure the decay rate of the proton. A quantum gravity theory may also have falsifiable predictions. A limit may be reached where the various theories have differences only with consequences that we can't measure or observe, such as properties of the earliest moments of the big bang.

But what about questions like "What caused the big bang?" "What happened before the universe was created?" "Are there other universes, and if so what are their properties?" "Why do the laws of physics have the structure that they have?" While some questions are ill-posed (such as what happened before time was created), others are pretty darn good questions for which there doesn't seem to be a way to obtain an answer (aside from just making one up and believing it).
In any case science has progressed by assuming that more and more can be known.

Question:

Why is it that on a night when it is mostly cloudy the stars are often visible while the Moon (even when full) is not?

Answer:

Stars cover all of the sky, whereas the Moon can span at most about half a degree. If there are thin spots or breaks in the cloud cover you will see stars, but to see the Moon it must be clear at the specific spot in the sky where the Moon is located.

Moreover, one of the standard misconceptions is that the Moon should be up every night. The moon is up for about 12 hours at a time, and because of lunar phases these twelve hours move through the 24 hour cycle. Hence during many nights the Moon is visible for only a few hours or not at all.

Question:

How do we really know what the universe is doing? We haven't even been past the moon. Isn't it possible that there are conditions out there that we cannot even dream of?

Answer:

Certainly, one would expect that there are phenomena out there of which we haven't even dreamed. It may be that aspects of the universe exist that we cannot understand with our limited minds. But we have made remarkable progress proceeding on the assumption that we can learn things about the universe. Don't discount what we have accomplished so far simply because there may be an incredible amount left to learn. Think of the things we had to learn just to complete a trip to the Moon and how amazing that would have been to someone such as Aristotle.

Question:

Beyond explaining how the universe behaves and why it exists, what is the ultimate goal of cosmology? Is it to explain a higher force or a creator behind creation?

Answer:

I would say its goal is to explain as much as can be explained about the universe. We don't know how much can be explained, but we (as a species) can keep trying to understand everything.

Question:

What is the likelihood of the theory of general relativity being replaced or drastically modified as all former theories have been?

Answer:

Probably a better way to ask this is whether our current theories will be improved. We know that relativity has to be improved in the sense that we need a theory of quantum gravity to bring together the two great theories of the twentieth century. Presumably we will eventually develop such a theory and relativity will be "replaced," although it will continue to apply in regions where quantum effects are unimportant, in the same way as Newtonian gravity can be used where the gravitational field is weak and the speeds are much less than c.

Question:

Do you think that it is possible ever to determine absolute answers or will it always be educated guessing?

Answer:

It depends on what you mean by "absolute answers" and "educated guessing." The answers to multiple choice questions are regarded as absolute even though the student may be doing (un)educated guessing. More seriously, would you say we have an "absolute answer" regarding the size and shape of the Earth? That was once a matter of educated guessing.

Question:

Will it ever be possible to know, definitely, the true model of the universe? Will we have something like such a model in the next 20 years?

Answer:

There is a philosophical question here about the "true model" of the universe. (Can a "true model" of anything ever exist? Can a model of the universe ever be complete since the universe is, by definition, everything?) But in practical terms we can expect to have a good model of the universe, and soon, I believe. If we continue with telescope and spacecraft development we should be able to measure the fundamental parameters of the universe. This may not happen in the next 20 years, however, given how much effort is required to build such instruments.

Question:

Is it possible that all we know about cosmology is wrong?

Answer:

No. (Unless you wish to entertain a philosophical discussion about whether all empirical knowledge is "wrong".) It is certain that what we know about cosmology is incomplete, but much of what we do know, such as the nature of the solar system, the existence of other galaxies, and so forth, is certain. Exactly where one draws the line between "certain" and "still uncertain" depends to some extent the individual. I would hold that Hubble expansion (Chapter 10) and the cosmic background radiation (Chapter 12) are also "certain," but some might still have a few reservations.

Question:

Descarte proved his existence with cogito ergo sum. Yet how can one ever prove that one is not a brain in a vat, being fed electrical impulses? Can one prove in scientific terms the existence of objective reality (i.e. that it is not all an illusion)?

Answer:

Since it seems always possible (as Descarte discussed) to explain any observation by the action of some entity intentionally deceiving us, the "brain in the jar" hypothesis is not falsifiable. Descarte reasoned that even if he was being deceived, or even if he was deceiving himself into believing the external world existed, cogito ergo sum meant that at least he was there to be deceived.

Descarte went into a restaurant and sat down. The waiter asked him "Would you like to order a drink?" Descarte said "I think not." Suddenly he vanished.

Question:

Before this century a scientist was sometimes also a philosopher. What kind of role do you see for philosophers and philosophy for now and in the future regarding scientific discovery and theory?

Answer:

Philosophic studies help to develop the scientific method, so practitioners of science are practicing philosophers, if you will. At the edges of science there are issues that we are not certain are well-posed, or solvable. Scientists also remain guided by what must be regarded as philosophical principles when experimental data are lacking. (E.g., Mach's principle guided Einstein in his quest for a general theory of relativity. Although Einstein ultimately derived a theory that is not in agreement with Mach's Principle.)


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Copyright © 1998 John F. Hawley