Continuing from yesterday’s post, I said that some religious people think that since there is matter in the universe that did not exist before the universe came into being, this must constitute a violation of scientific laws and thus requires some agency to create it. But they do not understand that energy comes in many different forms and that they all have to be included in the calculation. The fact is that despite all the matter that exists in the universe, the net energy of the universe is zero because the positive energy in the matter is canceled by the negative gravitational potential energy. So the appearance of an entire universe out of nothing need not violate the law of conservation of energy or any other law. Hence unless expressly forbidden by an as yet unknown law, there is nothing to prevent a vast, even possibly infinite, number of universes to have been created and exist simultaneously with ours, each with its own space-time and laws and matter distinct from ours.
This is known as the multiverse theory. In this scenario, given the large number of universes, it is not only likely, it is almost inevitable that one of those universes would happen to have the form of matter and the laws of science that eventually led to us. The so-called ‘fine-tuning’ argument that religious people sometimes invoke, that the properties of our universe seem to have just the right values to produce life like ours and thus suggests some deliberate design and hence a designer (which is, of course, our old buddy god) goes away, because those universes that did not have those properties would not have produced our kind of life forms. (There are other solutions to the fine-tuning problem that do not require multiverses.)
The problem is that we do not, at this time at least, know how to make contact with these other universes or have any direct evidence for their existence. But, as is usually the case with scientific theories, scientists are working on the problem.
[Cambridge University astrophysicist Martin] Rees, an early supporter of [Stanford physicist Andrei] Linde’s ideas, agrees that it may never be possible to observe other universes directly, but he argues that scientists may still be able to make a convincing case for their existence. To do that, he says, physicists will need a theory of the multiverse that makes new but testable predictions about properties of our own universe. If experiments confirmed such a theory’s predictions about the universe we can see, Rees believes, they would also make a strong case for the reality of those we cannot. String theory is still very much a work in progress, but it could form the basis for the sort of theory that Rees has in mind.
“If a theory did gain credibility by explaining previously unexplained features of the physical world, then we should take seriously its further predictions, even if those predictions aren’t directly testable,” he says. “Fifty years ago we all thought of the Big Bang as very speculative. Now the Big Bang from one millisecond onward is as well established as anything about the early history of Earth.”
The credibility of string theory and the multiverse may get a boost within the next year or two, once physicists start analyzing results from the Large Hadron Collider, the new, $8 billion particle accelerator built on the Swiss-French border. If string theory is right, the collider should produce a host of new particles. There is even a small chance that it may find evidence for the mysterious extra dimensions of string theory. “If you measure something which confirms certain elaborations of string theory, then you’ve got indirect evidence for the multiverse,” says Bernard Carr, a cosmologist at Queen Mary University of London.
Support for the multiverse might also come from some upcoming space missions. [Stanford physicist Leonard] Susskind says there is a chance that the European Space Agency’s Planck satellite, scheduled for launch early next year, could lend a hand. Some multiverse models predict that our universe must have a specific geometry that would bend the path of light rays in specific ways that might be detectable by Planck, which will analyze radiation left from the Big Bang. If Planck’s observations match the predictions, it would suggest the existence of the multiverse.
Physicist Sean Carroll explains the multiverse theory in this three-minute video.
The point is not that we have shown that the multiverse theory is true because we haven’t. The point is that there is no shortage of scientific explanations for why our universe exists and has the properties that it has. Like Laplace, what we can say is that we have no need for the God hypothesis. People might want to believe in a god to satisfy some emotional or psychological need, but we do not need such an external agency to explain our being. As Steven Weinberg said, “One of the great achievements of science has been, if not to make it impossible for intelligent people to be religious, then at least to make it possible for them not to be religious.”
Will religious people now give up on god as they realize that there really is no hope for finding something that only god or religion can explain? I hope so, but am not optimistic. Although religion has proved itself to be totally useless for anything except as a soothing or scary bedtime story for children and credulous and insecure adults, the desire to believe in a god is so strong in some religious people that they will find some other leaky boat to put their faith in, even as the waves of disbelief wash over them.