One of the challenges for a person trying to explain physics to the non-expert — and for non-experts themselves — is that scientific language and concepts are often frustratingly confusing. Often two words are used for the same thing, sometimes words are used that are fundamentally misleading, and often a single word is used for two very different but related concepts. You’d think we’d clear this stuff up, but no one has organized a committee dedicated to streamlining and refining our terminology.
A deeply unfortunate case, the subject of today’s post, is the word “mass”. Mass was confusing before Einstein, and then Einstein came along and (accidentally) left the word mass with two different definitions… both of which you’ll see in first-year university textbooks. (Indeed, this confusion even extended to physicists more broadly, causing the famous particle physicist Lev Okun to make this issue into a cause celebre…) And it all has to do with how you interpret E = mc² — the only equation everybody knows — which relates the energy stored in an object to the mass of the object times the square of the universal speed limit c, also known as “the speed of light”.
Here are the two possible interpretations of this equation. Modern particle physicists (including me) only use the first interpretation. The purpose of this post is to alert you to this fact, and to point you to an article where I explain more carefully why we do it this way. Continue reading
Yes, it was funny, as I hope you enjoyed in my post from Saturday; but really, when we step back and look at it, something is dreadfully wrong and quite sad. Somehow TIME magazine, fairly reputable on the whole, in the process of reporting the nomination of a particle (the Higgs Boson; here’s my FAQ about it and here’s my layperson’s explanation of why it is important) as a Person (?) of the Year, explained the nature of this particle with a disastrous paragraph of five astoundingly erroneous sentences. Treating this as a “teaching moment” (yes, always the professor — can’t help myself) I want to go through those sentences carefully and fix them, not to string up or further embarrass the journalist but to be useful to my readers. So that’s coming in a moment.
But first, a lament.
Who’s at fault here, and how did this happen? There’s plenty of blame to go around; some lies with the journalist, who would have been wise to run his prose past a science journalist buddy; some lies with the editors, who didn’t do basic fact checking, even of the non-science issues; some lies with a public that (broadly) doesn’t generally care enough about science for editors to make it a priority to have accurate reporting on the subject. But there’s a history here. How did it happen that we ended up a technological society, relying heavily on the discoveries of modern physics and other sciences over the last century, and yet we have a public that is at once confused by, suspicious of, bored by, and unfamiliar with science? I think a lot of the blame also lies with scientists, who collectively over generations have failed to communicate both what we do and why it’s important — and why it’s important for journalists not to misrepresent it. Continue reading
Posted in Higgs, LHC Background Info, Particle Physics, Physics, Public Outreach, Science and Modern Society
Tagged atlas, cms, DarkMatter, DoingScience, Einstein, energy, Higgs, LHC, mass, press, proton, PublicPerception, relativity, top_quarks
One of the questions I get most often from my readers is this:
- Since gravity pulls on things proportional to their mass, and since the Higgs field is responsible for giving everything its mass, there obviously must be a deep connection between the Higgs and gravity… right?
It’s a very reasonable guess, but — it turns out to be completely wrong. The problem is that this statement combines a 17th century notion of gravity, long ago revised, with an overly simplified version of a late-20th century notion of where masses of various particles comes from. I’ve finally produced the Higgs FAQ version 2.0, intended for non-experts with little background in the subject, and as part of that, I’ve answered this question. But since the question is so common, I thought I’d also put the answer in a post of its own.
As preface, let me bring out my professorial training and correct the question above with a red pen:
- Since gravity pulls on things proportional to their
mass to a combination of their energy and momentum, and since the Higgs field is responsible of giving everything not everything, just the known elementary particles excepting the Higgs particle itself its mass, there obviously must be a deep connection between the Higgs and gravity… right? wrong.
Now let me explain these corrections one by one. Continue reading
Apologies to those who’ve been asking questions: I’ve been away from the website for a few days (family matters) and have not been able to keep up with comments. I will try to catch up over the coming day or two.
But I do have two pieces of good news.
First, I gave a public lecture over the weekend, on-line, called “The Quest for the Higgs”, which I believe many of my readers will find at the right level. Because of some technical difficulties with the sound recording, I didn’t immediately recommend that you listen; but those problems are now fixed and the sound is pretty good. The audio is to be found here at BlogTalkRadio, through the Virtually Speaking Science series; on that website, there’s a link to the slides accompanying the talk, or you can just click here to get them. [Note the slides are under copyright; please ask permission before reproducing or using ideas you find therein.]
Second, the long-awaited final article in the series on Particles and Fields (with a little math) has arrived.
- Ball on a Spring (Classical)
- Ball on a Spring (Quantum)
- Waves (Classical Form)
- Waves (Classical Equation of Motion)
- Waves (Quantum)
- Particles are Quanta (new!)
As a bonus, you can then find out what the key technical difference is between bosons and fermions (the consequences of this difference are described, without technicalities, here.)
Next month: a series of articles on How the Higgs Field Works.
Posted in Higgs, LHC Background Info, Particle Physics, Physics, Public Outreach
Tagged energy, fields, Higgs, LHC, particle physics, particles, relativity, waves
If you’ve just gotten back from vacation, perhaps after days or weeks seeking the perfect wave, well, what a treat awaits! So much reading to do, about such interesting things. I’m writing a set of articles, intended for the reader who has once-upon-a-time seen beginning physics (what we in the U.S. would call “freshman physics”, or even a good “advanced placement physics” course pre-university) with the goal of explaining what fields and particles are. Five of the seven or eight articles are done; four appeared over the last two weeks, and now there’s a new one:
- Ball on a Spring (Classical)
- Ball on a Spring (Quantum)
- Waves (Classical Form)
- Waves (Classical Equation of Motion)
- Waves (Quantum) — the new one.
After this: an article on Fields, and then one on Particles, and maybe one more with some follow-up information. And then, with this set complete, I’ll move on to another series of articles, about how the Higgs field works…
One of my current goals is to explain how the Higgs field works to anyone who’s learned a bit of physics at the beginning-university or advanced pre-university level. As a step toward the goal, I am creating a set of pages that explain how fields work, why quantum mechanics implies that sufficiently simple fields have particles, and which aspect of a field’s behavior determines the masses of its particles. You will find that knowing a little physics and a little math is helpful.
[I'm afraid that most of you who never had a beginning physics class at all will have to be patient. It's an even greater challenge for me to explain the Higgs field to someone who's allergic to math, or hasn't had much math yet; I'm hoping my current efforts will help me see how surmount that challenge. But meanwhile you might like to read my Higgs FAQ and my popular article on Why the Higgs Particle Matters.]
The first step is to remember how a ball on a spring works — one of the first things one learns in any physics class — and then learn a little bit about how quantum mechanics changes the answer — one of the first things one learns in a quantum mechanics class. This is where the concept of a “quantum” first makes its appearance in physics. Those articles are now ready for you to look at. The next step [waves, both without and with quantum mechanics] will follow over the coming week.
Note: I’ve included, for the first time on this website, some animated gifs among the figures. These should animate when you click on them.
I know they need improvement; over the next day I’ll be trying to make them faster to load and run. Please be patient and let them load; but do let me know if you can’t make them work at all, and if so, what browser and hardware you’re using. Update: they should be much faster now.
Posted in Higgs, LHC Background Info, Particle Physics, Physics
Tagged amplitude, energy, fields, frequency, oscillation, particle physics, particles, spring, waves
One of the strange but crucial features of our world is that every type of atom except hydrogen contains neutrons in its nucleus, even though neutrons, on their own, decay (to a proton, electron and anti-neutrino) within about 15 minutes on average. At first glance this seems puzzling. At second glance too. How can stable matter be made from unstable ingredients?
The reason this is possible has everything to do with Einstein’s special relativity, and the way mass and energy are intertwined there. A crucial role is played by the energy that is most important for binding things together, which I’ve called “interaction energy”.
I’ve now written an article explaining why neutrons inside of nuclei can be stable, giving the example of the deuteron (one proton bound to one neutron) which is the nucleus of “heavy hydrogen”, or “deuterium”. If you understand this example, you’ll basically understand the point for other nuclei as well.
[For those of you in the New York City area: I'll be joined by the wonderfully talented singer-songwriter-pianist Andrea Wittgens in giving a physics/music joint performance/presentation at the storied Cornelia Street Cafe, Sunday May 13th at 6 p.m., as part of their Entertaining Science series. It's entitled Rhapsody for Piano and Universe, and intended for the general public. The place is pretty small, so get reservations in advance.]
I have written a lot about energy, but I’ve put off introducing the most important type of energy again and again. It’s the most important, because it is this type of energy that is responsible for all the structure in the universe, from galaxy clusters down to protons and everything in between. It is the most challenging to write about because it is not particularly intuitive. All the types of energy we intuitively understand, such as the energy of motion, are positive, but this type of energy, crucially, can be negative. On this website I’ll call it “interaction energy” (not the technical term, but my own, chosen to avoid misconceptions that might otherwise arise) because it is associated with the interactions among fields — including their little ripples that we call “particles”. If you’ve taken physics you’ve heard of “potential” energy; what you learned within that concept is a subset of what is included under interaction energy.
I’ve been wanting to address this for a while, because many of you have asked penetrating and central questions about the basic structure of matter, such as:
- Why is the neutron stable inside of atomic nuclei, given that on its own it is unstable?
- Why is the proton arguably heavier than the quarks and gluons that make it up?
And there are other equally important questions that no readers have yet stumbled upon but that I ought to address. Before I can answer any of those questions, however, I have to first describe interaction energy and the role that it plays in structure.
So — without further ado, here’s the article. This was an especially hard article to write and it may well be confusing in places — so I very much welcome your feedback, in order that I can try to make it clearer, if necessary, in later versions.