Science Myths


tt_icon_170In keeping with my previous post on the International Year of Astronomy, this week’s 5-minute  Science Teaching Tips podcast is about our perception and the size of the moon.  What coin would just barely cover the full moon? You may be surprised. TI director (and recovering astrophysicist) Linda Shore explains how our brains distort the actual size of the moon. Listen to the full podcast — When the Moon Hits Your Eye.

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Satellite composite image of Western Hemisphere from NASA

Satellite composite image of Western Hemisphere from NASA

Ooh ooh ooh, Bad Astronomy posted (a while ago) a fabulous list of Ten Things You Didn’t Know about the Earth. If you dig my science myths, check this one out. Such gems as “The earth is smoother than a billiard ball,” “Destroying the earth is hard,” and “Mt. Everest isn’t the biggest mountain.”

See also his earlier Ten Things You Didn’t Know about the Milky Way.

Just got this from Bob Park’s What’s New column. Looks like Gingko has failed a double-blind study to see if it really improves memory. I’ve been taking it for a while, in hopes that it would defuzz my neuronal connections (I’m not that old, but my memory took a real hit ever since I was on crazy antimalarial drugs in Peace Corps 10 years ago).

This reminds me of when a friend told me that there’s no reason why Airborne would improve your immune system. I was really angry at him for telling me this. Airborne definitely seems to keep my colds from getting too severe. If that’s due to a placebo effect, then hearing scientific reasoning that it shouldn’t work will destroy my placebo effect. Especially since my belief structures are particularly sensitive to scientific evidence.

Here is what Bob Parks wrote. I’m a bit perturbed by what he writes at the end, that all these other remedies have failed double-blind tests. It sounds to me as if he expected this to happen, because herbal remedies are by their very nature “unscientific” or something. I don’t see why some of these “natural” remedies couldn’t have something to them. After all, we take Zinc to help our immune system. That’s just a mineral. What makes a mineral less “woo woo” than a plant (like Echinacea)?

3. GINKGO BILOBA: A TIP ON WHERE YOU CAN CUT EXPENSES.
Annual sales of the herbal remedy Ginkgo biloba in the US are at $249
million. It is alleged to prevent memory loss. It doesn’t. In its
first large trial, half of 3,069 volunteers 75 and older were given of
Ginkgo biloba daily, while the other half were given a placebo. They were
assessed for signs of dementia every six months for 6 years. Neither the
patients nor the doctors doing the assessment knew which group patients
were in. The group getting the placebo actually did slightly better,
although the difference was not statistically significant. France is
planning an even larger study. Ginkgo has a lot of company. One after
another, the most popular herbal supplements, ephedra, Echinacea, St.
John’s Wort, have failed in double-blind, placebo controlled studies.

Molten glass - Mark Interrante - from NY Times

Molten glass - Mark Interrante - from NY Times

This is an addendum to my earlier (and popular) post about whether or not glass is a liquid.  If you haven’t read the previous post, the crux of the myth is that many of us are taught in science class that glass is a veeerry slow flowing liquid, and that’s why old windows are thicker on the bottom than the top.  News flash — actually you can find old windows that are thicker on the top than the bottom because it’s just an artifact of how glass windows were poured back in ye olde days.  But that doesn’t mean that glass is a simple thing.

A few months ago there was a great article in the New York Times Science section called “The Nature of Glass remains Anything But Clear“.  This very nice article about glass talks about how — even if it’s not a liquid — it’s a pretty complicated thing. “The arrangement of atoms and molecules in glass is actually indistinguishable from a liquid,” it says Solids tend to have atoms arranged in nice little tinker-toy stacks, whereas atoms in liquids aren’t so organized, more like someone threw the tinker toys across the floor in a rage, which is why they can flow.  The atoms in glass are more jumbled than organized.  So how come glass is so strikingly hard if its atoms don’t have a rigid order?

From the article:

“When cooled, a liquid either freezes, as water does into ice, or it does not freeze and forms a glass instead. In freezing… the molecules line up next to and on top of one another in a simple, neat crystal pattern. When a liquid solidifies into a glass, this organized stacking is nowhere to be found. Instead the molecules just move slower and slower and slower, until they are effectively not moving at all, trapped in a strange state between liquid and solid. .. This glass transition does not occur at a single, well-defined temperature; the slower the cooling, the lower the transition temperature. … By contrast, water, cooled quickly or cooled slowly, consistently crystalizes to the same ice structure at 32 degrees Fahrenheit.”

The reason glass forms is still a hot topic, with many competing theories.

There have been several posts around the blogosphere of late regarding a report from journalist Steven Goddard that the arctic sea ice isn’t melting as quickly as we thought. In particular he was calling into question the validity of the data reported from the National Snow and Ice Data Center (NSIDC) in Boulder, Colorado — I’ve included that graph below.

However, his analysis was not well-founded, and he’s since admitted his mistake. The Island of Doubt has posted a nice summary of what was wrong with his arguments. They write:

Goddard’s article is rife with scientific errors and evidence of his lack of familiarity with the science. His main argument, that the ice area up there is 30% larger than last year, not just 10%, is the product of the fact that Goddard based his story on his own analysis of images from the NSIDC and other sources. That analysis… consisted entirely of counting white pixels…. It turns out that Goddard got confused because he didn’t take into account map-projection distortion differences between competing images.

Once that little problem is dispensed with, it turns out that there is no discrepancy, the arctic is melting faster than normal, and may yet break last year’s record. Or not. Even if Goddard had been right, though, that says nothing about long-term trends. The point is, as Goddard proved, if you’re going to argue that an entire field of scientists got it wrong, you really should know something about the subject.

To Goddard’s credit, though, he admitted his mistake.

Sadly, the story has already started to make its way around the internet. So, just like myths like polar bear fur being a fiber optic (it’s not), or cats which grow wings (they don’t) it may be hard to get this one to go away. Why is it so much easier to spread rumors that something false is true than to fix the problem by telling people that something they think is true is actually false?  It’s made worse by the fact that some folks want to have fodder to fuel denialist claims, so they don’t have a lot of reason to correct erroneous information.

Deltoid also blogs about Goddard’s article here.

In an attempt to combat the media’s relentless pursuit of anxiety-producing headlines, the NY Times Science Page (July 29) just published a list of ten things you don’t have to worry about while you’re on vacation. While most of these are not guaranteed to be completely safe and worry-free, the latest results are promising. In redux:

1 – Hot Dogs – Saturated fat seems to be less of a worry than carbohydrates, says the latest in a series of studies
2 – A/C – Leaving your windows open at 65 mph creates air drag that cancels out the fuel savings from turning off the A/C
3 – Eating regionally – In terms of the carbon footprint, food is shipped more efficiently internationally than within a country and thus apples from New Zealand may have a smaller carbon footprint than those from Washington (though I bet that buying from your local farmers’ market is still your best bet)
4 – Cancer from cellphones – There’s no known mechanism for the radiation from cellphones to cause cancer, and there are no consistent links between phone use and cancer.
5 – Plastic bags – They use less energy to make, ship, and recycle and take up less space in landfills than paper bags.
6 – Toxic plastic bottles – Bisphenol-a (BPA) seems to have no evidence of harm in humans, at least in the low doses found in polycarbonate bottles.
7 – Sharks – Just one person died from a shark attack last year! [LINK TO PREVIOUS POST]
8 – Arctic Ice – While we do need to worry about long-term ice loss in the Arctic, the record ice losses predicted for this summer haven’t come to pass. (Although I’m not quite sure the NYT has this one write, and here’s a blog post about the melting ice and what we do have to worry about)
9 – The universe’s missing matter — You’re not to blame for losing it, and the universe isn’t likely to collapse anytime soon.
10 – Wormholes – Not likely. Neither is the destruction of the universe by a black hole created by the LHC.

REVISED 9/11/08

I just recently got an email from my father that showed to me once again that the apple doesn’t fall far from the tree. I guess geekgirl is truly the progeny of geekdad. (He’s a retired physical chemist, BTW). He saw an interesting article in Science about how we calculate fuel efficiency in quite a misleading fashion. We calculate miles per gallon, which tells us if we’ve got a gallon of gas in the tank then we can go X number of miles. But, says Richard Larrick of Duke University, this ratio should instead be turned on its head. If we want to go, say, 1000 miles, how many gallons will it take us? After all, the amount of gas consumed by a car does not decrease linearly as the mpg of the car increases. My Honda Civic (40 mpg) will take me twice as far on the same amount of gas as, say, a Ford Explorer (20 mpg). And if I want to drive 1000 miles, my Honda Civic will take me there on half the amount of gas that it would take the Explorer. Great, that all makes sense. But now if I start looking at making improvements to the mileage of either car, there’s where the “mpg” measure is misleading. It turns out that adding 10 mpg to the low-mileage car will save you a lot more gas and money than a 10 mpg improvement in the high-mileage car.

So he went and graphed it (gotta love geek dad) by just dividing 1000 miles by the miles per gallon and multiplying by $4 per gallon. The 1000 miles part isn’t important for the argument, it just scales up the final answer.

You can see that improving the efficiency of a 10 mpg car to 20 mpg has a much larger effect in the cost (and the # of gallons used) than does improving the efficiency of a 40 mpg car to a 50 mpg car. I’m not feeling so bad about not getting a hybrid car now.

The essential message is that we can’t do calculations like 1/x – 1/y in our heads. In Science Magazine’s podcast, Larrick says:

And, to kind of understand why MPG tricks people it’s useful to do a little bit of math. And so, you could think about a problem that a, a family might face of deciding whether to get rid of an SUV that gets 10 miles per gallon, or a sedan that gets 25 miles per gallon. And let’s say that they’re both driven about the same distance, roughly like 100 miles a week, and with the SUV they need another big car, so they’re thinking about a minivan that gets 20 miles per gallon. And with the sedan they’re thinking about replacing it with, let’s say a hybrid sedan that might get 50 miles per gallon. Well people are very attracted to the idea of replacing a car that gets 25 miles per gallon with one that gets 50 – that’s a big jump of 25 miles per gallon. And, getting rid of the SUV that gets 10 miles per gallon to a car that gets 20 miles per gallon – that just
isn’t as big of a jump, it doesn’t look as impressive….

So, let’s just think about how many gallons the SUV uses – the car that gets 10
miles per gallon. So, if we’re driving a hundred miles, that’s going to use 10 gallons to
go the hundred miles. If we replace that with the minivan that gets 20 miles per gallon,
we’re only going to use 5 gallons to drive the same hundred miles – we’ve now saved 5
gallons just by replacing the SUV with the minivan, going from 10 MPGs to 20 MPGs.
Let’s do the same calculation for the other car that could be replaced – which was the
sedan, that does get 25 miles per gallon – replace it with a small hybrid that gets 50 miles
per gallon. Well, at 25 miles per gallon that car’s only using 4 gallons to go a hundred
miles, and the hybrid’s only going to be using 2 gallons to go a hundred miles. That’s
just a 2-gallon savings. The big savings comes from getting rid of the most inefficient
car, the SUV that gets 10 miles per gallon with one that’s more efficient – the one that
gets 20 miles per gallon.

Or, as my dad says, in more abstract language:

The dependence of the cost (or gallons consumed) is not a linear function of mpg with a constant negative slope, rather it is a reciprocal function of mpg with a decreasing negative slope as mpg increases.

The cost is not a linear function of the mpg as most people think and base car buying decisions on. Instead, as the simple calculation shows, it is a curved function. What is clear from the graph is that small gains in mpg for a low mpg vehicle have a relatively large effect on the cost to drive 1000 miles. The effect becomes much less important as the mileage of vehicle improves. Bottom line, you save much more money if you ditch the SUV getting 15 mpg for a car getting 25 mpg (savings $107 for a 10 mpg increase) than if you change from a vehicle getting 25 mpg to one getting 45 mpg (savings only $71 for a 20 mpg increase!). Our dependence on
foreign oil would be greatly reduced if we were to focus on improving the mpg of the very low mileage vehicles on the road.

I also learned recently that European’s rank their vehicles according to how many liters of gas are required to drive 1000 km rather than rating them according to kilometers per liter (or mpg as in the U.S.). The European’s ranking is a more realistic way to compare vehicles and we should adopt it in the U.S..

You can see more on this at the Everyday Scientist, who says:

The real problem with MPG is that the same change in the MPG correspond to a huge change in fuel used at the low MPG end, and almost no change if a car already has a high MPG rating. Going from 20-25 MPG saves more gas that going from 35-50 MPG; going from 12-14 MPG saves more than either. This isn’t intuitive, and you really need to calculate the savings per mile in order to make a rational decision.

The take-away message is that we can’t do calculations like (1/a – 1/b) in our heads.

Richard Larrick tells us more about his research on the topic:

So, our actual research posed a series of questions about if you wanted to replace one vehicle with another one, which change is going to be most beneficial, in terms of reducing – and we, we couched it largely in environmental terms – the gas that’s used and therefore the effect on the environment. And people rate, for example, a change from 42 to 48 as being more beneficial then a change from 16 to 20 miles per gallon. And, without working through that math I hope that it’s obvious now that that 4 MPG improvement on 16 really reduces the amount of gas used quite a bit, and 42 to 48 doesn’t make, it’s still beneficial, but it isn’t nearly as large a change.

Interviewer – Robert Frederick
Right, they’re thinking it as a linear scale.

Interviewee – Richard Larrick
Exactly. And it really is a curvilinear relationship where the steep drops, in gallons that are actually used, occur among the MPG in the teens, and it gets flatter and flatter as you approach the kind of high end of what we see now – which is about 50 MPGs. So, the small MPG steps, on inefficient cars, have a big impact on reducing the amount of gas that’s burned.

UPDATE 11/24/08 – I just heard from Rick Larrick, who saw this post and wanted to share his websites with us:

I just ran across your sciencegeekgirl blog.  Great stuff.

And thanks for the mention of our Science article.  I’m definitely trying to get the word out, and, to be completely honest, really want to see the EPA, consumer reports, or both change to GPM.  That has become my mission!

I wanted to let you know about two webpages I’ve been running where I keep updates on the GPM argument:

http://faculty.fuqua.duke.edu/~larrick/bio/Reshighlights.htm

http://www.mpgillusion.blogspot.com/

Thanks again for the mention.  Best, Rick

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