The Higgs Field is Ugly.
Despite physicists’ tendency to wax eloquently about the beauty and harmony they uncover in their particle accelerators, if you really press them they’ll admit that the Higgs Field is an ugly piece of physics stuck on to our universe for no apparent reason.
Well, maybe for one reason.
But you’re not going to like it.
The Higgs field isn’t even the ugliest piece of physics out there. Far, far uglier is an even more recent discovery, something known as vacuum energy.
But let’s start with the Higgs. It’s ugly enough to get your revulsion meter running.
The Higgs field, we’re now fairly certain, permeates all space. Its tiny, tiny value ensures that matter particles like electrons and quarks interact with it, giving them mass. They don’t interact too much, though, otherwise they’d appear much more massive than they do. The problem is, the Higgs has no business being so small. When we add up all the factors that go into the Higgs field, we find that it ought to be huge, about 1016 times (that’s a 1 followed by 16 zeroes, or about ten million billion times) larger than it is.
So why is the value of the Higgs field so low? You’re not going to like the answer. Keep reading.
In 1999 cosmologists made a shocking discovery. The universe, known for many years to be expanding, is not merely getting bigger. It is accelerating. The acceleration is caused by something that physicists had assumed was zero. We now know that it isn’t zero, but instead is extremely tiny. It’s called the vacuum energy.
Like the measured value for the Higgs field, the measured value for the vacuum energy is too small. Way too small. In fact, the difference between theory and experiment in regards to the vacuum energy has been called “the worst prediction in the history of physics.”
The vacuum energy is smaller than the predicted value by a factor of something like 10120. This is a number so large that it literally defies explanation. Remember that 10120 is already ten times larger than 10119, which is ten times larger than 10118, and so on. Then consider that the total number of particles in the observable universe is something like 1080, which is 1040 times smaller than 10120, and you start to get just a glimmer of just how big that number is – and just how big a problem physicists face.
In a crazy turn of events, though, these two problems, the Higgs problem and the much larger vacuum energy problem, have found a potential solution in two quite separate fields: string theory and cosmology.
In the late 1990s, string theory, the idea that all elementary particles are made of tiny strings, seemed on the verge of a breakthrough. The various forms of string theory looked to be converging, and hopes were high that a single “theory of everything” was just around the corner.
Then disaster struck. String theorists kept finding more and more new versions of string theory. They kept finding more and more ways for strings to form a universe. They kept finding more and more ways that the extra dimensions and other parameters of string theory could fit together mathematically in a coherent description of the world.
No one knows for sure, but it seems likely today that there are at least (ready for this?) 10500 distinct, consistent ways that strings can make a universe. Every one of these 10500 (the number is so big that even 10120 is utterly dwarfed by it) has different laws of physics; in particular different values for the Higgs field and different values for the vacuum energy.
OK, big deal. We only have one universe, right? So who cares if there are 10500 different ways to put a universe together? We live not in 10500 universes, but just the one. Don’t we?
That’s where cosmology comes in. The Big Bang is by now a well-established event in the history of the universe, but the Big Bang all couldn’t explain some very puzzling observations about the early universe. It took an idea called inflation to make the Big Bang universe work. Briefly, inflation is the idea that at the moment of the Big Bang the universe grew by an enormous amount, far faster than the speed of light ordinarily would allow. Inflation explained why the universe looks the way it does today.
But the causes of inflation remained murky. Some researchers realized that if inflation could start once, it could start again. In fact, the real problem wasn’t starting inflation. It was stopping it.
In an inflationary universe, the end of inflation could never be a global phenomenon, but only a local one. In other words, the end of inflation in our piece of the universe would not have spelled the end of inflation in the rest of the universe. Inflation would keep going, on and on, possibly forever. Each time it stopped, a new bubble universe would be created. And (here it comes) each of those bubbles would have its own unique laws of physics.
So where does that leave us? Scientists argue and sputter about what is science, whether these ideas are measurable, testable, have anything to do with our reality. But as spectators we can take the longer view. Many, many different lines of reasoning are now pointing us in the same direction: we are but a single instance in a vast and ancient multiverse.
Tragically, it is entirely possible that we will never be able to prove this idea.
I told you you weren’t going to like it.
I am a realist. I believe there really is a reality out there, whether or not we can always collect evidence related to that reality. As an observer of science but not a scientist, I find it quite likely that we live in a multiverse in which our observable piece is but one tiny bubble, a single instance in a far grander collection of separate universes. It is also likely that these other bubbles have separate values for things like the Higgs field. There are probably many factors that go into determining the Higgs field, and those factors themselves can be scrambled around as new universes come into being.
The Higgs, then, is ugly because it’s parochial. The question, “Why does the Higgs have the value it does?” becomes equivalent to asking why the Earth orbits 93 million miles from the Sun. Sure, there is a proximate answer to that question, having to do with this asteroid nudging that asteroid, this planetoid glomming on to that one, and so on. But such details aren’t very interesting. The ultimate answer, the answer we were really looking for when we asked why in the first place, is that the Earth orbits as it does because while many orbits were possible, in most of those we would not be here to ask.
Similarly, there may be no interesting physics reason explaining why the Higgs field has the value it does. Certainly, the proximate explanation will discuss things like fields, particles, and their interactions, but the ultimate answer will be that the Higgs (and the vacuum energy, and probably many other constants of the universe) have the values they do because we intelligent beings can find ourselves only in that tiny fraction of bubbles in which the laws of physics allow for us. And despite our very best efforts, we may never be able to prove that this is true.
Like I said, ugly.