Sorry, I’ve been traveling. <ref blows whistle, lose possession of ball>
Archive for July, 2014
For most of history, the daily passage of time was denoted by the Sun. Solar Noon occurs when the Sun stands at its highest elevation (also known as its altitude) above the local horizon when it transits the north-south meridian. The trouble is, the passage apparent solar time doesn’t exactly match what we call solar mean time, or the 24 hour rotation of the Earth. In fact, this discrepancy can add up to as much as more than 16 minutes ahead of solar noon in late October and November and over 12 minutes behind it in February. This is worth bringing up this week because this factor, known as “The Equation of Time” — think “equation” in the sense that sundial owners must factor it in to make solar mean and apparent time “equal” — reache[d] its shallow minimum for 2014 this Saturday at 7:00 UT/3:00 AM EDT with a value of -6.54 minutes.
The filaments are created when pulses from a 10 Hz Ti:sapphire laser collapse the air into a narrow filament, increasing the refractive index of air in the center of the beam. The filaments heat the air as they travel, causing it to expand, and leave behind an air density depression (or hole) with a lower refractive index than the surrounding air.
I saw, via twitter, so links to a story that seems to be a repeat from a few months ago: about a bra (dubbed SHE) that delivers a jolt to would-be attackers.
The problem with a majority of them: they claim the shock is 3,800 kV (kilovolts). That’s curious jargon, to use that number and that prefix — why not just say 3.8 MV (megavolts)? I suspect from that alone that this is a transcription error somewhere, and the original was 3,800 Volts, which is 3.8 kV, and someone combined them. It’s even possibly an error of notation, because some folks use commas and periods in the opposite sense in their display of numbers. Maybe someone got confused.
But really, the true clue that this is wrong is the physics. The dielectric
constant strength of a material tells you how much of a potential difference you can apply before it fails as an insulator. For things like neoprene or polyethylene, i.e. rubber or plastic, which are good insulators, the value is around 20 MV/m and we have almost 1/5 of that. In other words, you’d need about 20 cm of the material at an absolute minimum, which gives new meaning to the term “padded bra”. Since nobody with engineering sense would fail to have a safety margin — conditions will be less than ideal, materials wear and crack, etc. — it’s larger, perhaps double (or more). So, in a word, no.
But scale that down to 3.8 kV and the thickness is now of order a millimeter, which is reasonable. Within the context of the discussion.
4. Stemming Tide of Elderly Men
Ask a child to draw a scientist and they likely draw an old man with crazy white hair. STEM has a persistent image problem where girls don’t see themselves reflected in that image.
[T]he container ship Tokio Express was hit by a wave described by its captain as a “once in a 100-year phenomenon”, tilting the ship 60 degrees one way, then 40 degrees back.
As a result, 62 containers were lost overboard about 20 miles off Land’s End – and one of them was filled with nearly 4.8m pieces of Lego, bound for New York.
No-one knows exactly what happened next, or even what was in the other 61 containers, but shortly after that some of those Lego pieces began washing up in both the north and south coasts of Cornwall. They’re still coming in today.
McCallum wondered if he could borrow the technology from the whipped cream can and create a similar delivery mechanism for cake batter, in which an accelerant releases air bubbles inside the batter, allowing the cake to rise without the need for baking soda and baking powder.
To his surprise, it worked.
Arbitrary serving size, too — if you want one cupcake, you make one cupcake. Microwave in 30 sec. With that ease, though, I’m not sure “portion control” is as much of a feature as they tout.
Every now and then there’s a kerfuffle about people treating other people badly. These things need to be talked about, but I wish we could do a better job of it. You might guess that this is prompted by the recent Feynman posts and responses/comments, and you’d be right. Before that it was “not all men”, and before that, Bora. But I’m not going to go into specifics about any of those, I’m going to tell you why such discussion is off the table for me. Even (perhaps especially) in the light of declarations that others must speak up — that silence is assent, and similar assertions.
I used to be active on various discussion boards other than the one that hosts this blog, and I’d go and visit when physics discussions at SFN were slow. I was reading a thread where someone (a crackpot, if I may) was proposing an alternative to relativity, which was almost certainly wrong, and there were posters making note of that in no uncertain terms. I noticed a problem, though — one of the equations the crackpot was using was actually correct — I think it was the gravitational time dilation formula gh/c^2, which is the approximation you get when you can assume g is constant — and I made a post pointing this out: I said that there were a lot of questionable claims being made, but this equation was not one of them. Adjust criticism accordingly. No problem, right?
Not so much. At that point, a number of other posters set upon me, accusing me of defending the crackpot, and concluding that I must therefore be a crackpot. There was one who went so far as to say that no real physicist would ever use an approximate formula (!), because we had computers and could run code using an exact formula. Actual examples, including physics papers using similar approximations were not enough to dissuade these folks from their positions. I had been branded a crackpot and once that had happened, no facts mattered. At that point I was was wrong by fiat so anything I had to say was dismissed, and my support for the entirety of the crackpot’s position was assumed. After that, the only dialog directed at me was sarcastic. I was a leper.
It was not a pleasant experience, and this in a relatively mild atmosphere. It gave me some perspective in moderating discussions involving those who are not enamored of the scientific mainstream — look at the facts, and do not assume more is there than is written, and don’t attack the person. Snark is a signal that any serious consideration is over, so one has to be sure all reasonable discourse has been exhausted. It can happen, and I’m guilty of that from time to time, but it’s after going over the same ground three or four times and making no progress. (Sometimes a claim is so outlandish that ridicule is the only response — but those are exceptions, not the norm.)
I’ll use, as an example, the use of the term I’m not particularly fond of: “fanboy” (or worse, fanboi). I usually see these in discussions about Apple products (as an observer — I rarely participate), aimed at someone who likes Apple products. A: I like X about my iPhone. B: Fanboi! To me, it’s a signal that the party isn’t willing to discuss any merits of the argument. It’s dismissive and no better or more productive than an eight-year-old engaging in name-calling. In the Feynman discussions, I have not checked to see if it was deserved or not (probably yes, but I don’t know), but to my mind any useful conversation is over once someone has dropped the fanboy flag or other blatant sarcasm on the pitch. It’s a big Do Not Enter sign.
Another danger about snark is it’s an invitation for others to jump in. It’s a sort of mob mentality, I think. Scientists having discussions generally keep to the issues and don’t typically degenerate into mockery, but something happens once that first window gets broken. People in the mob probably don’t recognize they are in one, at least at the time.
Pointing out an error in an evolution paper does not make you a creationist, pointing out a mistake in a global warming paper does not make you a denialist, just as pointing out an error in a critique of crackpottery did not make me a crackpot. Correcting the facts is what we should be expecting in discussions, so the “if you’re not with us you’re against us” mentality absolutely does not fit. We, as scientists, recognize the dangers of that in formal science, and go to great lengths to point out to science detractors that we are not promoting dogma. That attitude needs to be more pervasive in discussions about the culture that surrounds science.
I have opinions on matters, and perhaps something to add to a discussion. But the entirely predictable response that gets played out gives me pause about participating. Perhaps that’s an unfixable part of the internet. But it may also be true that some of what many agree are social issues in STEM that don’t seem to be getting better very quickly are being hampered because some people feel shut out of the discussions as they become polarized so quickly. Think about that: people you want to reach are possibly being shut out of the conversation because of the fear that they will be verbally pummeled and shunned at the slightest inkling that they don’t agree with you, because they see how others are treated. You will not hear their voice, and if they feel that they are being attacked, they will not listen to yours.
I want the broader social situation to improve. These conversations need to happen, so we must do a better job of encouraging the conversations. I can disagree with details of something you say without disagreeing with your conclusion. Finding fault with some fact you’ve quoted does not automatically mean I agree with your opponent — I want you argument to be stronger, unassailable, and I’ve found a chink in it. I’m trying to help you. But having been burned by this before, under milder circumstances, I have no wish to jump in to a much hotter fire.
These conversations need to happen. We must do a better job of encouraging the conversations.
Swinging the arms clearly saves energy for runners, and helps to minimise the amount that we rotate the body while swinging our legs, which led Arellano and Kram to wonder whether the metabolic benefits of arm swinging outweigh the cost of carrying the limbs.