## Tuesday, 30 January 2018

### Maths at the Movies: Interstellar plus SPECIAL GUEST

This week we watch Interstellar.

We are very excited to be joined by the expertise of

Whereas Thomas and Ben are just about good enough understand their own mathematical fields Cat has a wide range of disciplines under her belt spanning both physics and movie effects. We couldn't ask for a better guest!

If you're interested in watching Interstellar you can follow the Amazon below.

Subscribe via iTunes.

Follow us on twitter @PodcastMathsAt, as well as @ThomasEWoolley, @benmparker and @cat_harris_fx

## Our Friday Factoid: Once in a blue moon is one tenth of donkey's years!

### This month sees a blue supermoon occurring at the same time as a lunar eclipse. But how rare are these things compared to others? The Maths at (mathsat.co.uk team investigate)

We all know the phrase “Once in a blue moon”, but how long is this period? We compare this periods with other well known periods to enable better mathematical precision on these matters.

A blue moon
Traditionally, a blue moon occurs when there are 13 moons in a year or, in a more recent definition when there are 2 moons in a calendar month…. Whichever moon we designate as the blue moon, this occurs once ever 2.7145 years, or once every 991.47 days.

Donkey’s years
Once in Donkey’s years is a common expresison, from the fact that donkey’s ears are  very long thing. The Guineess world record for the oldest donkey ever is 54 years, but 25-30 years is more common. Thus "Once in Donkey’s years" is around once in 27.5 years, or once every 10044 days.

A super moon
This means that a full moon is closer in its orbit than at other times. Not that rare at all- and occurs about 25% of all moons. This term is not well defined, so this happens around once every 109 days.

A "once in a lifetime" experience clearly depends on how long someone lives, but from official UK statistics a newborn boy will expect to live 79.2 years and a girl 82.9 years. Thus a man will have the advantage of experiencing a once in a lifetime event slightly more often at once every 28927.8 days, and a woman once every 30279.23 days. You may be lucky and experience it more often!

Total Lunar Eclipses
Eclipses occur very frequently, but total eclipses only rarely. Of course, they’re not visible everywhere on Earth, but somewhere. Encyclopedia Brittanica lists these as 66 per century, or once every 1.512 years or every 553 days.

A fortnight
A fortnight is something Brits use to confuse Americans, like rubbers and irony, and is defined in British law as the frequency of rural buses, and is once every 14 days.

Super Blue Total Lunar Eclipses
OK, for all these to occur together, these are quite rare. Forbes estimates this as once every 265 years, or around once every 10 Donkey’s Years, or once every 96791.25 days. The last one was on December 30, 1982. However, just by chance, there’s another one coming along next year. Like buses- none come for a fortnight, then two come at once.

Super Blue Total Donkey Lunar Eclipses
Now you’re just being silly. This won't happen in a month of Sundays. This is mathematics- are you paying attention, as it will be on the test?

A month of Sundays.
This is a way of saying never, colloquially. Every  days.

Biannually
This means once every six months, or once ever 182.75 days.

Biennially
Who invents these things? This means once every two years, not to be confused with the above, or once every 731 days.

Time immemorial
Defined in English Law to be since before the reign of King Richard 1st, 1189, or longer ago than anyone can remember. There’s over 828 years or around 302,600 days.

Conclusion: "Once in a blue moon" is a well defined phrase. A blue moon happens 10 times in donkey years, or about once every 71 fortnights, or about 30 times in a lifetime. It never happens in a month of Sundays, but has happened around 305 times since time immemorial.

For these and other interesting mathematical facts, listen to Dr Thomas Woolley and Dr Ben Parker, as well as the mysterious Liz, on the popular Maths podcast “Maths at:”, available at mathsat.co.uk, iTunes, and wherever you get your podcasts.

### Watch along with MATM: Interstellar and SPECIAL GUEST!

Next Friday we will be critiquing the maths and physics of Interstellar.

What's more, because this is the 10th episode (and because Ben and Thomas aren't physicists) we will be joined by a SPECIAL GUEST.

Not only is she a Cambridge physics graduate, but she now works in film digital effects. Who could ask for more?

Why not watch along with us? You can buy a digital version of the film through Amazon by clicking on the image below.

## Friday, 19 January 2018

### Maths at the Movies: The Oxford Murders

This week we discuss we discuss The Oxford Murders:
• Thomas laughs at the word bra;
• Liz wants a prime number named after her;
• Ben just wants his coffee bringing to him;
• And we all think about mathematically defining pasta shapes.
Yup, it's a case of a bad movie, with very little to talk about. At least it made for a fun recording!

If you're interested in watch The Oxford Murders, then you're weird, but you can buy the DVD from Amazon below.

Subscribe via
iTunes.

## (Thomas is very sorry for choosing it).

However, should you want to waste 104 minutes of your life you can buy the DVD from Amazon by following the link below.

Such a waste of talented people!
Such a waste of mathematical logic!

We didn't read it... but the book might be better?

## Wednesday, 10 January 2018

### Answer to the Moneyball problem

Listen here!

What is the probability that the next person you meet will have an above average number of ears?

Although most people have two ears, there are those with only one. Thus, the average number of ears is just below two.

However, since people with only one ear are quite rare this means you are most likely to meet a person with two ears next, meaning that the probability is nearly 1! We can't say it is exactly 1, because the next person you meet, although unlikely, may have a damaged ear.

Of course, if you live with a person with only one ear then your probability is significantly lower, because you'll likely bump into that person next.

Listen to our Flatland podcast to hear more about this problem and learn why clarifying the averages we talk about have important consequences regarding the interpretation of the question.

## Friday, 5 January 2018

### Maths at the Movies: Flatland

This week we take a walk in the lower dimensions as we talk about Flatland: The Movie.
• How much is your life worth?
• Could 2D animals exist?
• Did George Orwell rip this story off by adding a third dimension?
All of these questions and more are interrupted in our Flatland: The Movie podcast.

If you're interested in watching Flatland: The Movie  you can follow the Amazon link below.

Subscribe via iTunes.

## Tuesday, 2 January 2018

### Puzzle from Moneyball

Ben provided the following puzzle during our Moneyball podcast.

What is the probability that the next person you meet will have an above average number of ears?

Don't worry he gave a set of multiple choice answers, so, is the answer:
• 0?
• nearly 0?
• 1/2?
• nearly 1?
• 1?
• π?
As a hint it isn't π.

## Monday, 1 January 2018

### One the first day of Christmas my true love gave to me...

Yes, Christmas maybe over, but the puzzles still remain! During our Christmas episode Thomas provided the following puzzle.

In the song "12 days of Christmas" how many presents do you get over all?

Note the lyrics are given below, but the main idea is that you are adding up consecutive triangular numbers. Namely, on the first day you get 1 present. On the second day you get 3 = 2+1 more presents, making 4 overall. On the third day you get 6 = 3 + 2 + 1 more presents, meaning 10 overall. Thus, in total, how many presents do you get?

You can find the answer during Maths At: Christmas

We also gave you a bonus question that built on this ideas.

In the song "12 days of Christmas" how many legs are there in total?

As we discussed in the podcast there are many possible solutions to this question based on different assumptions. Do the milk maids have stools? Has a swan lost a leg and swimming in a circle?

Many possibilities! We will reveal our solution next time.

For those who want a consistent set of lyrics we used the following list:

First day:
A Partridge in a Pear Tree

Second day:
2 Turtle Doves
and a Partridge in a Pear Tree

Third day:
3 French Hens
2 Turtle Doves
and a Partridge in a Pear Tree

Fourth day:
4 Calling Birds
3 French Hens
2 Turtle Doves
and a Partridge in a Pear Tree

Fifth day:
5 Golden Rings
4 Calling Birds
3 French Hens
2 Turtle Doves
and a Partridge in a Pear Tree

Sixth day:
6 Geese a Laying
5 Golden Rings
4 Calling Birds
3 French Hens
2 Turtle Doves
and a Partridge in a Pear Tree

Seventh day:
7 Swans a Swimming
6 Geese a Laying
5 Golden Rings
4 Calling Birds
3 French Hens
2 Turtle Doves
and a Partridge in a Pear Tree

Eighth day:
8 Maids a Milking
7 Swans a Swimming
6 Geese a Laying
5 Golden Rings
4 Calling Birds
3 French Hens
2 Turtle Doves
and a Partridge in a Pear Tree

Ninth day:
8 Maids a Milking
7 Swans a Swimming
6 Geese a Laying
5 Golden Rings
4 Calling Birds
3 French Hens
2 Turtle Doves
and a Partridge in a Pear Tree

Tenth day:
10 Lords a Leaping
8 Maids a Milking
7 Swans a Swimming
6 Geese a Laying
5 Golden Rings
4 Calling Birds
3 French Hens
2 Turtle Doves
and a Partridge in a Pear Tree

Eleventh day:
11 Pipers Piping
10 Lords a Leaping
8 Maids a Milking
7 Swans a Swimming
6 Geese a Laying
5 Golden Rings
4 Calling Birds
3 French Hens
2 Turtle Doves
and a Partridge in a Pear Tree

Twelfth day:
12 Drummers Drumming
11 Pipers Piping
10 Lords a Leaping
8 Maids a Milking
7 Swans a Swimming
6 Geese a Laying
5 Golden Rings
4 Calling Birds
3 French Hens
2 Turtle Doves
and a Partridge in a Pear Tree

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