Science Seen Time One author Colin Gillespie helps you understand the physics of your world.
The DNA of the Universe
The universe burst into existence some 13,799,000,000 years ago. Why did it become this universe? Why does it have quarks and electrons; and elements including carbon, hydrogen, nitrogen and oxygen; and gravity to grow galaxies; and planets orbiting vast numbers of stars; and all of the ingredients that lead to life?
Doing this required many physical parameters (such as the gravitational constant or the charge on the electron) to have the “right” values. A small change in even one of them could mean no life on Earth and no stars anywhere. In physics and cosmology this is known as the Goldilocks problem. We will come back to it.
Let’s look at the first question: Why this universe? Readers will know how recent physics now points to a single quantum or fleck of space as the exact origin of the universe. The mathematical successes of string theory suggest it was a tiny entity known as a Calabi-Yau manifold. To work, this manifold needs precisely six dimensions. If you can get your head around this you can envisage that they are “compactified” down to the incredibly tiny Planck scale. String theory is concerned with fundamental entities. It says that the geometry of the way their six dimensions fold determines the properties of all the particles of which matter and energy are made. Canadian economist Irwin Lipnowski calls this ‘the DNA of the universe’. It’s an apt tag.
String theory is at a loss to say how six of the nine space dimensions of the universe became compactified. Why do six compactify? Why not all nine? Why compactify at all? Why stop at Planck size? These and other questions have bedeviled physics since the days of Theodor Kaluza and Oskar Klein who first proposed compactification.
Time One offers a simple answer to all of them: Flecks never did compactify. There was once just one and it began that way. Thus this—a single manifold with its DNA—is the much-sought initial condition of the universe. All else is made of exact replicas.
Physicists have calculated that there may be as many as 10500 possible distinct ways for the universe’s DNA to fold. This number boggles the imagination. It is larger than the number of space quanta in the entire universe. That is, it’s a number that does not have any real existence. But this outlandish number should not preclude study. That would be like saying we should not study human genes because in theory they have about 102,000,000,000 different combinations! Relatively few code for viable humans.
A key concept for this problem is predictive power. With 10500 possibilities, string theory predicts everything conceivable (and lots that’s not, including crazy universes). So in effect, say critics, it predicts nothing.
The concept of predictive power feeds the modern disconnection between physics and philosophy that is responsible for the malaise in which physics finds itself of late. This disconnect sees physics as no more than calculations that predict the results of experiments. We would be better served by physics that is aligned (as it once was) with philosophy.
The concept that corresponds to a more philosophical approach is explanatory power; that is, explaining lots with few assumptions, also known as Occam’s Razor.
The difference between the results from these two competing concepts is like night and day. The universe’s DNA may (so far) predict nothing. But the hypothesis that it exists can explain longstanding puzzles.
This is where we get back to Goldilocks. The universe’s DNA does indeed give focus to the question: Why was our universe born with the one in 10500 fleck geometry that makes it just right to create and support us? If this was a lottery our chances were almost exactly zero. String theory confronts us with this issue.
Most physicists cringe at the idea of the origin of the universe. They see it as contaminated by religion. Thus it has become fashionable to allow religion to dictate the course of science. This fashion is a serious obstruction for the free progress of physics.
Just as the hydrogen atom offered the simplest gateway to quantum physics, the newborn universe offers the simplest gateway to Planck-scale physics. The economic benefits of Planck-scale physics may be huge. It’s time for leading physicists to get back in touch with natural philosophy. History gives us reason to believe that it could get their physics moving.