How Well Do You Know Your Moon?

Phil Plait, who writes the wonderful Bad Astronomy blog over on Slate, noticed something interesting in a recent episode of The Simpsons:

Photo by 20th Century Fox Film Corp.
Photo by 20th Century Fox Film Corp.

To the untrained eye, nothing about this cartoon image is likely to seem unusual. But if you spend a lot of time looking at the sky, and you have the additional context that this scene occurred in the evening, then the Moon is actually quite revealing.

(For those of you thinking “it’s just a cartoon, don’t expect it to be accurate”, I realise that. But if you decide to treat it as though it must be accurate then it can be interesting to think about so bear with me.)

To understand why that is and how we know, we have to have a think about how we look at the Moon.

The Moon orbits the Earth in a plane that’s pretty well aligned with the plane of the solar system. This means if you drawn a line in the sky tracing the path of the Moon, you’ll also find the Sun and the planets roughly on that line. This is why we experience solar and lunar eclipses, which happen when the Sun and Moon are lined up particularly well with the Earth. Because the line is where eclipses happen, it’s called the ecliptic by astronomers.

Earth’s axis is tilted by 23.5° relative to this plane, but if you’re not too close to the equator (for example, if you’re in New Zealand or the USA) then you can say that if you projected the equator into the sky it would be in roughly the same position as the ecliptic. If you’re in the southern hemisphere, that means it’s to the north, and if you’re in the northern hemisphere, it’s to your south.

So, if you’re looking at the Moon from New Zealand, you must be looking roughly to the north. If you’re looking at it from the USA, you must be looking roughly to the south. This also means the Sun and Moon, moving east to west across the sky as the Earth spins, appear to move right to left from the southern hemisphere and left to right from the northern hemisphere.

When we look at the Moon, we’re seeing the same thing no matter where we are on Earth except for one thing: which way is “down”. The “bottom” of the Moon in the part that’s closest to the horizon. If you travel to the other hemisphere, and you’re familiar enough with the Moon, you may notice that it appears upside down. That’s because the direction of “down” has swapped – from roughly north to roughly south (or vice versa if you’ve travelled from north to south). If you want to see what the Moon looks like from the other half of the world, you have to bend over backwards (or lie on the ground). This is also why the Moon will appear to have rotated if you compare it when it’s rising to when it’s setting.

One more thing: the Moon orbits us in the same direction as we’re spinning, which means it moves across the sky slightly slower than the Sun. Each day, the Moon rises roughly 50 minutes later than the day before, so that over its 28 day cycle of phases this sums to 24 hours.


Now, getting back to that image from the Simpsons episode. That scene was apparently in the evening, and the Moon is low on the horizon. That means the Moon must either be about to set or have just risen. If it had just risen after sunset, then it was recently full (because a full moon rises at sunset and the moon rises later each day), which means its phase would be a waning gibbous. Waning refers to the fact that it is on its way from being full to being new, and a gibbous is the shape made by a circle with a crescent cut out from it.

In the picture, the Moon is obviously a crescent, so it can’t have just risen. If it’s just about to set after sunset, then is must just have been a new moon (because a new moon sets at sunset and the moon rises later each day), which means its phase would be a waxing crescent. Waxing refers to the fact that it is on its way from being new to being full, and the crescent refers to its curved shape.

Another thing we know about the Moon is that its lit side always faces the Sun. For example, the lit side of a full moon points right back at us, because from its perspective the Sun shines on it from behind us. If the Sun has just set, and the Moon is just about to set as well, then the lit side of the Moon must be facing the Sun. As the Sun sets in the west, this means the lit side of the Moon should also be facing west if it is a waxing crescent.

In the picture from the Simpsons, which we’ve established should be a waxing crescent, the lit side of the Moon is facing to the left. But remember, if you look at the Moon from the northern hemisphere you must be looking to your south, so west should be on your right. So if the waxing crescent moon is lit on its left, then you must be looking north to see it, which means you’re in the southern hemisphere.


Unfortunately, a lot of pop culture doesn’t get the Moon and its phases right. I know it’s such a tiny thing, and typically when they don’t get it quite right I can’t say I mind too much (although I often can’t help but notice), but I really love it when they put in that extra bit of effort to get it correct.

Almost all video games with day/night cycles where you can see the sky have the Moon orbit in 24 hours. Some of them include phases, although technically if your Moon always rises at sunset then it should always be full. I can forgive video games fairly easily though, I’m probably the only person who cares and I understand it could take significant development time to get proper lunar phases in. The only example I can think of that gets it right is Kerbal Space Program, where accurate celestial mechanics is an important part of the game.

Some books have issues with the Moon as well. Last year I was reading the book Ship of Theseus, and one scene describes the protagonist seeing the crescent moon rise as it gets dark. But crescent moons never rise as the Sun sets, light simply doesn’t work that way.

Movies often have trouble with it as well. The worst offender I’ve seen is the final scene from the movie Cloud Atlas:

Final scene from the movie Cloud Atlas
Final scene from the movie Cloud Atlas

Remembering that the lit side of a moon points towards its sun, and this applies even with multiple moons, that image implies some very strange things about the nature of light.

I’d love to see more media put more effort into getting this right. I know that one author who paid particular attention to this detail was J.R.R. Tolkien, who tried hard to get the phases of the Moon consistent with his dates when writing The Lord of the Rings and apparently did a pretty good job of it too.

My favourite example of well-documented in-depth world building doesn’t involve the Moon but I’d like to share it here anyway. My brother Jeremy (who’s currently working as a concept artist at Weta Workshop, a job he got soon after leaving Uni) worked on creating a deep and internally consistent fictional history to earn his masters degree in 2013. He ended up creating a fake National Geographic article from 1932 recounting the reporter’s visit to the settlement of Elkwood. The article only scratched the surface of all the thought he put into the work, if you want to see what he came up with you can read both the article and his exegesis explaining his research methods here: Creating Elkwood: building an alternate history

When fictional worlds are deep and internally consistent they become that much more enriched. If you know of any that have represented lunar cycles particularly well (or particularly poorly) let me know in the comments.

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Irradiation of Food and Compulsory Labelling

Queensland Fruit Fly | Photo by James Niland
Queensland Fruit Fly | Photo by James Niland

Biosecurity is a big issue for New Zealand. Being a group of islands fairly isolated from all other landmasses and having quite a unique native ecosystem (many native birds with no native mammalian predators and few native land mammals), we have a lot to lose from introduced species. There are also biological threats to industry that we have to try really hard to keep out of the country, such as Queensland fruit fly. There’s good reason why the Ministry for Primary Industries (MPI, formerly MAF) reacted so strongly when one of these flies was found in Whangarei in April 2014. If enough of these flies made it into New Zealand to self perpetuate, they could cause massive damage to New Zealand’s $5 billion horticulture industry.

In order to kill off any biosecurity risks, including disease-causing organisms and foodborne pests, various treatments (also known as “phytosanitary actions” when used on plant products) can be used when importing products into New Zealand. Different products that can be imported each have an Import Health Standard (IHS) that documents the process of importing them.

For fruit and vegetables being imported, they need to come with a phytosanitary certificate from their country of origin, to say that either they have been inspected by someone from MPI and they couldn’t find any pests, they come from a certified pest free area, or they have been treated to kill any pests. A sample of the products is also inspected by MPI when arriving in New Zealand, and if any pests are found then the products will have to be treated if they are to enter New Zealand.

The treatment used depends on a few things, such as what pest was found that they’re trying to kill. For example, assuming I’m interpreting the IHS correctly, if Thrips palmi is found in a shipment of capsicum from Australia it would be fumigated with methyl bromide at 32 g/m3 for 2 hours. Whereas if Conogethes punctiferalis were found, then the capsicum would be irradiated with a minimum dose of 250 Gy (Grays; 1 Gray is equivalent to 1 Joule of energy absorbed per kg of food).

EDIT 2015/02/01:

The previous paragraph is incorrect. Those treatments are the ones that should appear on the phytosanitary certificate, having been performed in the country of origin. The treatments done if a pest is found when they arrive in New Zealand are determined in the Approved Biosecurity Treatments Standard. So for fresh fruit and vegetables (page 37), if insects except for fruit flies (not slugs and spiders) are found then they have to be fumigated with methyl bromide at a particular rate and temperature for a particular duration (presumably depending on the pest and the produce). Looking at this standard, it seems human food doesn’t get irradiated if pests are found when it arrives in New Zealand. According to MPI’s list of treatment providers (direct PDF download), there is only one facility in New Zealand able to provide food irradiation, which is in Wellington.


Methyl bromide is an insecticide, and it’s also recognised as an ozone-depleting substance. Because of this, its use is tightly controlled. It’s only allowed to be used for a few specific purposes, one of which is quarantine, and New Zealand has to provide statistical data to the Ozone Secretariat on the annual amount of methyl bromide that we use. It’s nasty stuff – even skin contact with high enough concentration of the gas can cause severe blistering – but after being used to fumigate food it apparently dissipates fairly rapidly. There are some objects that MPI won’t fumigate with methyl bromide for various reasons, which are described in their info sheet I linked to above.

Irradiation is quite different. Using either Cobalt 60, x-rays, or an electron beam food is blasted with a specific amount of ionising radiation. Cobalt 60 is a radioactive source of this radiation, but as it emits gamma rays instead of neutrons it doesn’t make anything else around it radioactive. Both x-rays and electron beams are created by non-radioactive sources and can be switched on and off.

When food is irradiated, the process kills any organisms that are living in the food, including disease-causing organisms and pests. The food does not become radioactive, instead it will just be slightly warmed from the energy it absorbs. Also, the radiation will trigger some chemical changes, but these occur only in amounts comparable to heat treatments. In this way it’s quite similar to the process of pasteurisation used to make milk safe to drink.

In 2010, following an extensive literature search, the European Food Safety Authority (EFSA) published their Scientific Opinion on the Chemical Safety of Irradiation of Food. They found that the new evidence published since their previous decision in 2003 wasn’t enough to change their opinion that “there is not an immediate cause for concern” regarding the safety of irradiated food.

Irradiated Food symbol | FSANZ
Irradiated Food symbol | FSANZ

The strongest negative evidence they found seemed to be a case in which cats ate a diet consisting largely or entirely of highly irradiated (25.7 to 53.6 kGy, i.e. 100 to 200 times as much as in the capsicum example from earlier) cat food and subsequently suffered from leukoencephalomyelopathy (LEM). This evidence doesn’t necessarily have any relevance to humans though; in another report dogs ate the same pet food and didn’t exhibit LEM. Also, as the incident was only linked to one specific lot of one specific brand of pet food it’s unclear if irradiation was the culprit at all.

Even though irradiated food appears to be entirely safe to eat and not significantly different from food that hasn’t been irradiated, it is currently compulsory to label irradiated food in New Zealand under the Australia New Zealand Food Standards Code Standard 1.5.3.

MPI’s Food Smart website has an informative page on food irradiation. It’s quite clear on several important points (you can read their full answers on the page):

Does irradiation change food?

At the approved doses, changes to the nutritional value of the food caused by irradiation are insignificant and do not pose any public health and safety concerns.

Some treated foods may taste slightly different, just as pasteurized milk tastes slightly different from unpasteurized milk. There are no other significant changes to these foods.

Does irradiation make food radioactive?

No.

Is it safe to eat irradiated food?

Yes. Irradiation of food does not make the food unsafe to eat.

The World Health Organisation, the Food and Drug Administration in the US and the American Medical Association all agree that irradiated food products are safe to eat.

The FDA’s page on food irradition has an informative “Debunking Irradiation Myths” inset:

Irradiation does not make foods radioactive, compromise nutritional quality, or noticeably change the taste, texture, or appearance of food. In fact, any changes made by irradiation are so minimal that it is not easy to tell if a food has been irradiated.

FDA

It also states that:

FDA has evaluated the safety of irradiated food for more than thirty years and has found the process to be safe. The World Health Organization (WHO), the Centers for Disease Control and Prevention (CDC) and the U.S. Department of Agriculture (USDA) have also endorsed the safety of irradiated food.

FDA


Earlier this week, the Herald published an article by Sue Kedgley on irradiated food. In my opinion that article is a load of unscientific scaremongering. Here are a few excerpts that appear clearly intended to be more emotive than informative:

But irradiated food is anything but fresh. It’s been exposed to radiation doses that are between three and 15 million times the strength of x-rays. The Brisbane radiation facility uses Cobalt 60 to irradiate food, a radioactive material that is manufactured in Canadian nuclear reactors, and shipped to Australia in special unbreakable steel canisters.

I visited the Brisbane irradiation facility in 2004. Boxes of food travel by conveyor belt into an irradiation “chamber”. The irradiation process breaks down the molecular structure of food; destroys vitamins in food, and creates free radicals and other “radiolytic compounds” that have never been found in nature, and whose effect on human health is not known.

Also of concern is the fact that in 2008 the Australian Government was forced to ban irradiated cat food after more than 80 cats died or became seriously ill after eating irradiated cat food.

This begs the question – if cats can die, or become ill from eating irradiated cat food, what could be the cumulative effect on humans of eating significant quantities of irradiated food? There’s no benefit to New Zealand consumers, and only risks to our growers, from imported irradiated produce.

Her comment that irradiation “breaks down the molecular structure of food [and] destroys vitamins in food” is quite at odds with the evidence that the nutritional content of irradiated foods are not changed significantly. This statement is entirely blown out of proportion, it’s like describing a papercut as having “ripped my flesh apart”.

She also doesn’t mention any of the details regarding the cat food incident, such as that their diet consisted largely or wholly of food irradiated 100-200 times as much as human food generally is, that the same food seemed to have no negative effects when eaten by dogs, or that the incident was only linked to one specific lot of one brand of cat food. How it relates to humans consuming irradiated food, if it has any implications on that at all, is not clear but her reaction is just scaremongering.

Her article appears to have been prompted by a couple of changes to the regulations that are being considered:

FSANZ is currently assessing Application A1092 seeking permission to irradiate twelve specific fruits and vegetables. A call for submissions on our assessment is expected to be released in the second half of 2014.

Food Standards Australia New Zealand | Food irradiation

FSANZ plans to start work on recommendation 34 (that the requirement for mandatory labelling of irradiated food be reviewed) later this year.

Food Standards Australia New Zealand | Labelling review

Here’s a link to Application A1092. That page specifies the 12 fruits and vegetables involved as apple, apricot, cherry, nectarine, peach, plum, honeydew, rockmelon, strawberry, table grape, zucchini, and scallopini (squash).

Ms Kedgley describes these potential changes as:

the Government is about to approve the importation of irradiated apples, peaches, apricots and nine other fruit and vegetables from fruit fly-infested Queensland.

If they succeed, retailers will be able to sneak irradiated produce into the food chain, and it will be sold, unlabelled, as if it was “fresh”.

Surely consumers have a right to know whether the apples they are buying are fresh, or have been imported from Queensland and exposed to high doses of radiation to sterilise them and kill off potential fruit fly lava?

Red apple
Red apple | Photo by Abhijit Tembhekar

Looking at the IHS for fresh fruit and vegetables (direct PDF download), you can see that honeydew, rockmelon, strawberry, grape, zucchini, and scallopini are already included, they just aren’t yet allowed to be treated via irradiation. As far as I can tell the others – apple, apricot, cherry, nectarine, peach, and plum – can’t currently be imported from Australia.

Given that the entire function of irradiating food is to kill unwanted organisms such as Queensland fruit fly larva, I think it seems disingenuous of Ms Kedgley to repeatedly refer to it as though allowing these products in will bring Queensland fruit fly to New Zealand. The reason why we can’t currently import these products is because of that fly, but allowing them to be treated by irradiation would let us safely import them.

On the issue of labelling, this seems to be a very similar issue to compulsory labelling of genetically modified foods and foods containing genetically modified ingredients (this is currently mostly compulsory in New Zealand). In that case, as with food irradiation, opposition generally seems to be driven by idealogical issues with the technology used or misinformed beliefs that it’s somehow unsafe, even though it’s entirely safe. It’s effectively a lose/lose situation – if labelling isn’t mandatory then “What are they trying to hide?” but if it is mandatory then “They wouldn’t have to put it on the label if it wasn’t bad for you”.

If you want to oppose the addition of those 6 new fruits to the list of foods that can be imported from Australia on the basis of supporting New Zealand farmers then okay, that’s a different argument altogether that has nothing to do with irradiation. There doesn’t seem to be much reason to oppose this on grounds that irradiated food may be unsafe to eat though.

Foods are not allowed to be irradiated unless they have been through a pre-market safety assessment process conducted by FSANZ

http://www.foodsmart.govt.nz/elibrary/food_irradiation_.htm

Given that irradiated food doesn’t appear to be unsafe, is there really any reason to keep labelling of irradiated food compulsory? If anything, isn’t compulsory labelling most likely to make people think that means it’s bad or unsafe when it isn’t? If it’s all about allowing consumers to make informed decisions, that would be rather counterproductive.


I’m lucky enough to know someone who’s a food scientist. Claire Suen has an MSc in Food Science from the University of Auckland, and I contacted her to ask for her thoughts on the process of food irradiation. Here are some of the things she had to say in response to some of the common arguments opposing food irradiation:

[Irradiation] changes the nature of food: carcinogenic, loss of nutrients etc.

So does cooking, burning toast, deep frying, etc. Irradiation causes minute changes to the food and some loss of nutrients such as vitamins, but these have all been thoroughly researched and the results are readily available. In short, no significant changes to the food have been found.

Regarding the lost of nutrients, I usually point out to people that this is negligible considering the nature of the food.

FSANZ have published some comprehensive risk assessment reports in the past, and using the latest report on tomato as an example:

Nevertheless, even assuming an upper estimate of vitamin A and C loss of 15% following irradiation from all fresh tomatoes, capsicums and tropical fruits (with existing irradiation permissions), estimated mean dietary intakes of these vitamins would decrease by 2% or less and remain above Estimated Average Requirements following irradiation at doses up to 1 kGy, with dietary intake typically derived from a wide range of foods.

The impact of cooking and storage time on nutrients in food is far more severe than the effects of irradiation.

Here’s a link to that FSANZ report on Irradiation of Tomatoes & Capsicums (direct DOC download)

There are better alternatives

Irradiated food saves cost for the manufacturers/importers/supermarkets because it eliminates otherwise costly alternatives.

Methyl bromide for example, is not 100% effective against insect eggs and larva, particularly if they are buried inside the fruit or seed. Storage pest such as beetles and weevils are extremely difficult to control and often need a combination of methods such as heat treatment, and fumigation. For herbs and spices, irradiation can be used to control pathogens such as salmonella and E. coli. No other method is as effective. But because consumers in NZ are against it, we have to use methods such as steam sterilisation and heat treatment, which impacts on the flavour and quality of the product. Consumers sometimes do not understand the amount of work MPI and the importers have to do to make sure foreign organisms do not get in the country. All it will take is a slack importer, a missed check, or an incomplete fumigation. What of the products that have to be destroyed due to microorganism contamination, or spoilage? If they had been irradiated, this wastage wouldn’t happen.

We don’t need irradiation since we can just buy local products

Unfortunately NZ is a small country and we have limited produce. I’m not saying we can’t get by without EVER importing anything, but, it seems to me that these people don’t realise just what the consequences are. Sure, we don’t have to import apples, or nectarines, but what about the tropical fruits not grown locally? Or spices? Let’s not eat fresh mango again, or curries, since pepper used to be worth its weight in gold because it’s not grown in Europe. We can’t get away from importing and by not using irradiation, NZ business have to use more costly, and less effective alternatives, which means all these cost are passed ultimately onto the consumers. I understand people’s concern that this will hurt local producers, but that is a question of economy and has nothing to do with the safety of irradiated food.

Now coming to the question of labelling

Unfortunately, it’s a no-win situation. If we label then consumers will think something is wrong with it, if we don’t label it’s as if we are hiding something. There is simply no way to beat that logic. In my opinion, if we don’t label products which have been heat treated, or fumigated, then we shouldn’t need to label for irradiation. But because consumer backlash is so strong, I wouldn’t want to give haters a chance to play the “Ah ha you are hiding something” or “give me my freedom of choice” card.

I say let’s put irradiated fruits on the shelves and label it as such so I can chose to buy it because it will be cheaper and better!

I think that last point says it all really. As a food scientist, Claire is quite familiar with the topic of food irradiation, and she would choose to preferentially buy irradiated food because she understands the process to be safe, effective, and not detrimental to the food.