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This track is an example of simulated data modelled for the CMS detector on the Large Hadron Collider (LHC) at CERN (Source: CERN)

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Two BIG physics problems

Tuesday 16th February 2016 12:19 pm

Why are the Higgs field and dark energy so weak? Find the answer and you could earn yourself a Nobel Prize, says Dr Karl.

Around the year 1900, the astronomers had a big problem — “what powered the Sun?”

They knew how much energy the Sun emitted, and they knew how big the Sun was. But even if the Sun were powered by something loaded with energy (such as coal), it should have burnt out after a few million years.

And yet the geologists were saying that the Earth was at least 10 or 20 million years old — and almost certainly, much older.

The answer to that problem came with discovery of radioactivity a few years later.

Very reasonably, you might say, “Well, this is nice theoretical knowledge, but what has it ever done for me?” Lots. On average, each Australian citizen can expect to have one radio-diagnostic procedure, as well as a few X-rays, at least once in their life. That radio-diagnostic procedure, and the X-ray, exist because we figured out that it was radioactivity that powered the Sun.

So let’s whiz forward a century and look at two of the biggest problems in physics today. These problems are that both the Higgs field and dark energy are much, much smaller than we would expect.

First, the Higgs field. It creates the property we call ‘mass’. Your body is made of atoms. In turn, these atoms are made of particles called electrons and quarks. Here’s the weird bit — inherently, these electrons and quarks have no mass. But when they interact with the Higgs field, they get mass. A Nobel Prize was won for proving this.

The Higgs field permeates all of space — and it’s loaded with energy. Each cubic metre of the Higgs field (and therefore, of space) carries the amount of energy emitted by the Sun in 1,000 years. That’s a huge amount of energy. But our theories tell us that the Higgs field should be much stronger — about 10,000 trillion times stronger. (If you want to read up more, look up the hierarchy problem. )

But if we have a big problem with the Higgs field being too weak, we have an enormous problem with dark energy being too weak.

Dark energy is too weak by a factor of a trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion times. That is much, much bigger than the ratio in size between an atom, and the entire known universe, which is about 10 trillion trillion trillion times.

So what is dark energy? It was discovered in 1998, when astronomers found that the expansion of the universe was actually speeding up. And what was forcing this speeding up of the expansion? Dark energy. Like the Higgs field, this discovery got a Nobel Prize for the astronomers.

But if you go into quantum field theory, and look at the cosmological constant, the energy in the vacuum and dark energy (and so on), you find that dark energy is too weak by a factor of 1 followed by 120 zeros — a truly humungous number. As the particle physicist, Harry Cliff said: “Whenever you hear the word ‘dark’ in physics, you should get very suspicious, because it probably means we don’t know what we’re talking about.”

It could be that there’s something very fundamental to both the Higgs field and dark energy that we don’t understand. Or, maybe we are just putting together our pieces of knowledge and understanding in a very wrong way. And there could be a dozen other explanations.

Now there’s an old saying in science, “It’s not the answer that gets you the Nobel Prize, it’s the question”.

Once you’ve got the question, you just apply the necessary basics (such as coffee, pizza, time, money and brainpower) and do the science for as long as it takes.

With these two big problems, we don’t have the answers — yet. But further down the line (today, tomorrow, or another century from now), the answers will not only generate a few Nobel Prizes, they’ll give us essential gadgets and useful processes.

And just as was the case with radio-diagnostic procedures and X-rays before they were invented, we currently have no idea of what these new gizmos will be.

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This blog first appeared on Dr Karl's Great Moments in Science

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