Higgs Boson

I have been writing this blog for about seven months now and a few of my friends have started sending me requests for topics they would like to learn about or think would be interesting for others to read. I do not always address them right away, either because I do not know much about the topic and need to do some research, or because I get distracted by other topics (like vacation with my daughter).

Early in July, when the first news on the Higgs boson came out, a friend of mine sent me an email asking me to address this topic in a blog entry. This was one of those cases where I did not know enough to start right away, but I am fascinated with the topic, so I wanted to look into it.

In order to understand what this particle is and why we care about it, you first need to understand something about the basic foundations and motivation for physics.

Physics is the study of the universe. Physicists are trying, in a myriad of ways, to understand how the universe works. Why does the sun come up in the morning? Why is the sky blue? Why do things fall to the ground when I drop them? What causes rainbows? What are we made of?

And some more esoteric questions: What are atoms made of? Why do photons travel at the speed of light? Why do some particles have mass but others do not – i.e. why do some particles fall when we drop them, but others do not? What keeps all the atoms in our bodies together? Why is our universe exactly the way it is?

Physicists have been working on this topic for a very long time and they keep discovering more and more. In the 19th century, we still thought that atoms were the smallest things in the universe, but now we know that they are made up of protons, neutrons and electrons. And more than that, we have discovered that protons and neutrons are made up of even smaller particles, which we call quarks.

There are a number of theories, or models, of how the universe is put together. Each of these theories attempts to explain the fundamental particles and forces that build our universe.

One of these models is called the Standard Model. This model explains which particles are most fundamental – are not made up of other, smaller particles. It also explains what causes the fundamental forces that hold us together. We are most familiar with gravity, which keeps us on the Earth, and the electromagnetic force – this is what holds our magnets on our refrigerator (along with lots of other more useful things). There are also the strong and weak forces – these forces act on smaller atomic scales. They are essential to our very existence (like holding our atoms together!) but are forces many of us do not think about on a daily basis.

The interesting thing about these forces is that they are not contact forces. If I drop a penny off of a building, it will fall to the ground even though nothing is touching it. Gravity does not need physical contact to work. The same for electromagnetism – if you take a strong refrigerator magnet and pull it off of the refrigerator a little bit so it is not touching and then you let go, it will pop right back onto the refrigerator.

How these forces work is one of the most important questions in Physics. The Standard Model does a great job of explaining how three of these forces work – the strong, weak and electromagnetic forces. We have identified particles, called bosons, that carry energy between objects and cause these forces.

That’s great, right? Three out of four isn’t bad is it? But gravity, the big, important force that affects all of our lives does not seem to fit into the model well using just particles that we have already discovered. We can explain how things work at very small scales (where mass is small and gravity is not a big deal) and we can explain how gravity works on very large scales, but we have a hard time putting everything together and really explaining what causes gravity.

Gravity is a force that depends on our mass. The more massive two objects are, the stronger the force of gravity between them. This is where the Higgs boson comes in. The theory is, that this is an particle that gives objects mass. It creates a ‘field’ – energy that permeates space. Objects (like us, or more specifically the tiny particles that make up our bodies) interact with this field in different ways. How they interact defines how much mass they have.

This is a bit abstract. Let’s think about something that we can all relate to a little better. My daughter loves to play with car keys and her favorite teddy bear. What would happen if she was playing near a big, strong magnet? Fortunately, her teddy bear would be unaffected, but sadly, the car keys would probably go flying out of her hand toward the magnet (unless she had a really good grip on them!). We know this – different types of objects interact with magnetic fields in different ways.

So the Higgs boson is a particle that causes different particles to have different mass. Okay, this does not sound any crazier than the other stuff I have said. But this is all just a theory.

We have never seen this particle. We do not know if it exists. That is one of the reasons for big experiments, like the Large Hadron Collider (shown above) at CERN. Physicists are trying to create situations where they can create and detect particles like the Higgs Boson. It takes a LOT of energy to do this and since we do not know exactly what this particle is like, it is difficult to try to measure it. In fact, up until recently (and even now), there are a number of physicists who think this theory is wrong. They believe that there are other, better explanations for how the universe works. We will not know for sure unless we find the Higgs boson…or we do not find it.

On July 4, 2012, scientists who work at the Large Hadron Collider announced to the public that they think they found the Higgs boson. There is still more work to be done, but they are seeing evidence in their experiments of a particle that acts just the way they think the Higgs boson would act.

This is VERY exciting! If this particle exists, then maybe the theory is correct and we really can explain how the universe works! Well, I am sure there are more details to be discovered, but this is great progress in understanding the world we live in. This is a great accomplishment.

I think Stephen Hawking’s reaction to this event is interesting, though (BBC News):

“This is an important result and should earn Peter Higgs the Nobel Prize,” he told BBC News. “But it is a pity in a way because the great advances in physics have come from experiments that gave results we didn’t expect.”

I think many physicists study the universe as much to discover new mysteries as to solve them. (Or maybe Stephen Hawking is just upset about losing a bet).

References: I found most of the information on the Higgs boson and standard model on the CERN webpage.

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Curiosity

A few weeks ago, when the first news on the Higgs boson came out, a friend of mine sent me an email requesting that I write a blog entry explaining what it’s all about (that blog entry will be coming next week on Laser Mom). He said that understanding this part of physics was hard for him as an engineer since he did not have much background in modern physics. He also asked,  “Why do we care about what gives us our mass?”

His question made me think about research in general. Of course, as scientists and engineers, we all write proposals to get funding, and papers for scientific journals, and give conference talks, and spend quite a bit of time explaining why what we do is useful and will save the world and make us all rich someday. But really, why do we really do our research? I think that most us can honestly say (hopefully!) that we do it because it’s really cool. It’s fun. Why do we want to find out what gives us our mass? Because we can. We are curious and want to understand how things work and what new things we can accomplish.

One of the things that I have done in the recent past for research is to shine laser beams into glass or polymers (i.e. plastic) and see what happens. It turns out you can use the energy in the laser beam to change the properties of the materials for practical engineering reasons – creating small feature sizes so that we can have better, faster, smaller computers and to write optical waveguides so that we can send information (internet) easier and faster from place to place. But I did not really study this just for practical reasons – it’s just fun! (The practical reasons are, of course, important to get funding to get paid to do what I love.)

I have to wonder if the first scientists to write optical wires in glass with high power lasers were not thinking (at least a little bit), “This laser is so cool. I wonder what would happen if we focused it down into that piece of glass? Will the glass vaporize? Let’s try it!” (I believe Davis et al. were the first to publish on this topic.)

Perhaps they were much more organized and focused in their pursuits, but I have to admit that most of the interesting things I have accomplished in the lab have started out with, “I wonder what would happen if…”

My one year old daughter is a natural experimentalist. She loves to try out new things and do things just to see what happens. If I drop this, what will happen? What if I pull on this handle? What will happen if I pull myself off of this landing (Ow!)? It is amazing to see how quickly she learns new things just by exploring and trying everything that comes to mind.

We have all (hopefully) mastered the basics of gravity at this point, but our curiosity and desire to try out new things is what makes us good scientists. Shining a laser beam into a light sensitive polymer and watching what happens just fascinates me. There are so many interesting things going on, from basic light propagation in glass/plastic to chemical reactions in the material.

Then there are a the cool things you do when you put two laser beams together – using different colored laser beams of different shapes to activate different chemicals in a material and making super tiny little dots in the material. There were three papers in Science a few years ago (May 15 2009 issue) discussing different ways of combining optics and chemistry to create features that were smaller than anything you could do before with these lasers (By the way, you can get all three of those papers for free if you sign up on the Science website.)

Oh sure, there are lots of good practical applications of shining lasers into materials (faster internet and computers?) and those are probably the things I will tell you if you ask me to give a talk on this research and certainly what I will tell you if I need to write a grant proposal.

But why do I really work with lasers, shine them into materials, use them for microscopy? Why are the scientists at CERN looking for the Higgs Boson?

I think the Mars rover’s name covers it: Curiosity.  Anyone who watched the video of Curiosity’s landing (YouTube – watch between minutes 5 and 6) can see the excitement and joy that scientists and engineers get when they have successfully completed a mission, discovered a new particle, built a new gadget or made measurements that no one before them has ever been able to do.

As scientists and engineers, we are a curious folk. Sometimes we get so wrapped up in funding, papers, etc. that we forget why we do what we do. That’s one of the reasons I am excited to go to an optics conference this fall. Conferences are a great opportunity to explore and enjoy that curiosity. We can go to talks outside our field, talk to other scientists we have never met, and get outside our normal routine. This setting always re-energizes me and gives me lots of new ideas of things I would like to explore when I get back to the lab.

Of course, with an infant at home, I do not really need to go anywhere. Babies are natural experimentalists and seeing her intense concentration in trying something new and her joy at discovering new things reminds me every day why science is so cool. We are all born curious, and hopefully we keep that curiosity as we grow older though we each tend to focus it in different directions.