“All speech, written or spoken, is a dead language, until it finds a willing and prepared hearer.” -Robert Louis Stevenson
It’s been another wonderful week in the Universe, and there’s been so much to share together. New this week on the main Starts With A Bang blog over at Medium, we’ve talked about:
- Are our students doomed to an inferior education? (For Ask Ethan),
- The greatest album covers as seen from behind (For our Weekend Diversion),
- A Star-Forming Spiral, M61 (For Messier Monday),
- The Astro Alphabet,
- How the Sun *really* shines, and
- Top 5 Signs of New Physics (For Throwback Thursday).
And you’ve come through with lots of excellent comments, and continue to make me happy that we keep the old ScienceBlogs site here open as a forum for all of you to have a say and interact with one another (and me) as you see fit. Some of your comments stand alone as simply interesting and informative, and others lend themselves to an even more detailed response from me. Here are — to me, at least — the best comments from the past week!
From Art on the topic of teaching literacy skills: It has been a very long time. Perhaps I’m not as smart as I once was. But for the life of me I can’t tell you what the letters: g, h, i, and n, o, p are supposed to represent. I finally figured out that L is for lick and V might be for vehicle but Y still evades me. In the old days Y was usually for yo-yo, or , more rarely, Yogi bear. I suppose the picture for N might be for ‘not going to make it’ but that strikes me as a bit grim for young children.
You have to recognize that English is an incredibly tough language for a number of reasons. Not only are words pronounced in vastly different ways, but we have many ways of expressing similar or identical concepts; the English vocabulary is astonishingly huge. And in different parts of an English-speaking country — not to mention different countries — there are strong preferences for various words that are uncommon in other regions.
In the USA, for example, how many children would recognize “b” as a bat? It’s a cricket bat, but cricket is a less common game than mumblety-peg is here in the USA; this phonics chart comes from the UK. You might look at “p” and think, “why are they showing a candle with a ‘p’ next to it,” but that’s because they call it a pillar there. “O” is a switch in the “off” position, “z” and “m” are clearly just the sounds being made, and “l” could be lick, but I’m pretty sure it’s either “lolly” or “lollipop” for the sucker the girl’s holding.
But for g, h, i, and n? If I had to guess — and I hope a trueborn Brit can verify or refute these — I’d say they were “gulf” (a synonym for sink or basin), the “hhhhhhhh” sound (the heavy breathing of an exhausted runner), the squeaking “iiiiiiii” sound that a mouse makes, and because that plane is clearly going down, I would guess “nosedive,” and simply assume the picture was chosen by someone who doesn’t know what part of the plane the “nose” actually is. (Sorry for the dissatisfying image!)
From Pavel on the subject of the Sun shining: AFAIK, the [dominant] source of Sun energy is the CNO cycle, i.e. [sequence] of proton captures and beta decays: C12 -> N13 -> C13 -> N14 -> O15 -> N15 -> C12 + He.
It is true that the CNO cycle — where hydrogen fuel is added progressively to carbon, nitrogen and oxygen, producing helium, energy and a carbon to start all over again — does, in fact, occur in the Sun, in addition to the proton-proton chain described at length in my article. Here’s what the CNO cycle looks like. (Start at carbon-12 and move clockwise.)
Like all nuclear physics reactions, the rate of this cycle is exponentially dependent on temperature, with proton capture by nitrogen-14 being the slowest, most difficult step. In order for these reactions to fully run in a cycle (i.e., for the nitrogen-14 + proton reaction to proceed to completion), it requires stellar temperatures of 15 million Kelvin, something just barely achieved in the very innermost core of the Sun, which is estimated to reach 15.7 million Kelvin. However, since the proton-proton chain occurs at much lower temperatures, the CNO reaction rate doesn’t proceed faster than proton-proton reactions until temperatures of about 17 million Kelvin, which corresponds to stars more than 130% the Sun’s mass, or approximately F5-class stars (and brighter).
In other words, the Sun does have a little bit of the CNO cycle going on inside it, but it only contributes less than 2% of the Sun’s total energy, as compared to more than 98% for the proton-proton chain. But if we had a significantly more massive star, the CNO cycle would dominate. That just isn’t the case for our Sun.
From Sinisa Lazarek, admonishing me for my apparently inconsistent position on the Top 5 Signs of New Physics: Ethan, you say “Now, we do not know how to make a working theory of quantum gravity. String theory is a possibility (and maybe the only viable game in town)” What about loop quantum gravity? I am no expert in either field, but you’ve been a vocal opponent of string theory for years now, why the change of heart? From calling it “Is String Theory an Unphysical Pile of Garbage?” to now saying that it might be the ONLY viable theory?? What’s up with that??
What’s up, indeed. Because I am a vocal opponent of string theory. At least, when it’s presented as a physical theory that’s relevant for an experimental signature that could even, in principle, be present in this Universe. But if you’re interested — from a theoretical viewpoint — in creating a framework in which all four of the fundamental forces (including gravity) are simply different manifestations of a single, overarching mathematical structure, that is the town in which string theory is (thus far) the only viable game.
If all you care about is how to calculate quantum effects to first order as far as gravitation is concerned, then perhaps loop quantum gravity may potentially offer some insight. But it was never intended to be a full theory of quantum gravity, merely a functional, effective approach. (Which it may yet turn out to be.) But neither it nor string theory is there, yet, and neither one has done anything other than a woefully unsatisfactory job of describing our physical Universe. So far.
My opinion about the “goodness” of a scientific theory is informed by its predictive power for our Universe. That doesn’t mean that I can’t recognize that ideas that have not yet progressed to the point of a scientific theory — and, let’s be honest, neither string theory nor loop quantum gravity are in the ballpark — don’t have the potential to someday get there. So there’s your nuance.
From Lotharloo on the same topic: Very very nice post! One question though, you say “In other words, unless we get hit by a big physics surprise, the LHC will become renowned for having found the Higgs Boson and nothing else fundamental, meaning that there’s no window into what lies beyond the Standard Model via traditional experimental particle physics.” Is it because the energy required for detecting the particles required by these five problems is so high that there is no chance of building a detector that can detect them?
For some of these problems, that’s certainly the case, but for others, it’s simply that the LHC isn’t really built for looking for these sorts of things. If there is new physics at the electroweak scale — if there’s extra CP violation in either the weak or the strong sectors — the LHC might be able to find that. Similarly, if dark matter is a particle with a large enough interaction cross-section and coupling to the Standard Model, the LHC’s got a shot.
But for all other cases, it’s a combination of the fact that either the energies requires won’t be reached by the LHC or the things that need to be detected can’t be detected by the LHC, or both.
Yes, heavy “see-saw” neutrinos are theoretically up at around 10^15 GeV in energy, some 100,000,000,000 times more energetic than what the LHC can probe. Quantum gravitational effects are some 10^90 times too weak to be seen by the LHC. But for something like detecting neutrinos, the LHC simply isn’t built for it. (Give us a half-a-light-year of lead and we’ll talk!)
It takes a combination of experimental apparatuses, specialized for different things, all working together to give us our picture of physics. The LHC might be touted as a “dream machine” because it pushes the energy frontier — and has given us the Higgs — but it’s not a solve all the problems with this one machine! Physicists hate it!
And a little bonus comment on a necro’d thread: Please share more information when you get from any where. any one have know about [Kepler] 186b.. please share your knowledge…
Lucky you. Kepler 186 is the name of an M-class star located 490 light-years away, and it has five known planets orbiting it. Kepler 186b is less than 6 million km from its parent star and slightly larger than Earth. Due to its size and proximity, it’s almost certainly tidally locked to its star, with daytime temperature almost double those on the planet Mercury.
But you probably were more interested in Kepler 186f, the potentially habitable one. Lucky for you, I was on TV talking about this just a few days ago!