Plus Blog

February 21, 2011

There's a new special episode of one of our favourite maths podcasts — Math/Maths, produced by Peter Rowlett and Samuel Hansen. Peter talks to Ruby Childs, a recent maths graduate who is interested in what makes people like mathematics for an essay she is writing. She's particularly interested in why people chose to study maths further. You can listen to the podcast, read a relevant blog post by Peter and you can also send your own answers to Ruby via Twitter or via a contact form on her tumblr blog.

The more people answer, the more interesting her essay will be!

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February 11, 2011

If you're in London on Tuesday the 15th of February, then why not take a journey into other worlds with John D. Barrow at the Royal Institution?

Barrow will tell a story that revolves around a single extraordinary fact: that Albert Einstein's famous theory of relativity describes a series of entire universes. Not many solutions to Einstein's tantalising universe equations have ever been found, but those that have are all remarkable. Some describe universes that expand in size, while others contract. Some rotate like a top, while others are chaotically unpredictable. Some are perfectly smooth, while others are lumpy. Some permit time travel into the past. Only a few allow life to evolve within them; the rest, if they exist, remain unknown and unknowable to conscious minds.

You'll encounter universes where the laws of physics can change from time to time and from one region to another, universes that have extra hidden dimensions of space and time, universes that are eternal, universes that live inside black holes, universes that end without warning, colliding universes, inflationary universes, and universes that come into being from something else – or from nothing at all.

Gradually, we are introduced to the latest and the best descriptions of the Universe as we understand it today, together with the concept of the multiverse – the universe of all possible universes – that modern theories of physics lead us to contemplate.

The event will start at 7pm. Tickets £10 standard, £7 concessions, £5 Ri Members Tickets purchased on the door will incur a £2 booking fee. For more information visit the Royal Institution website.

And you can read more about the universe, gymnastics, elephants and much more from Barrow on Plus!

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February 3, 2011

Here's a fact: take the year you were born in (only the last two digits, as in '85), add your age and then (probably) add 1. The answer is ... 111!

Birthday cake

This seems to have been making the rounds lately. Some people marvel at the fact that the answer is always 111 no matter how old you are and others think that 2011 is the only year in which a calculation like this will work. Looks like mathematical magic!

But there's a rational explanation. If you take the full year you were born in (as in 1985) and add your age, then it's clear that this takes you (more or less) to the year we're in now. After all your age is exactly the amount of time that's passed since you were born. The only qualification is that if you haven't yet had your 2011 birthday, you need to add an extra 1, because your official age is still the same as it was in 2010.

Here's an example: if you were born in July 1985, then you're 25 years old, and have been since July 2010. Expressing this using numbers gives 1985+25=2010 and therefore 1985+25+1=2011.

Now the difference to the calculation above is just that you leave out the first two digits in the year. This is the same as subtracting 1900 from your birth year and also from the answer 2011. So you get (1985-1900)+25+1=(2011-1900)=111.

So there's no mystery at all. The result just says that if you add your age to the year you were born (and then add 1 if you haven't had your birthday yet), you end up in the current year. That's pretty obvious, so it's surprising how many people seem to be stumped by it. After all we're all used to working out someone's age from their birth year, or vice versa, and we do this by subtracting the age or the birth year from the current year 2011. The calculation above is just the reverse of that. Maybe people find the calculation puzzling because once you reverse it in this way and leave off the first two digits of the year, the numbers lose their meaning as years or ages and just become abstract numbers. Then they also lose their temporal coherence, so there's no reason to suspect that the answer should always be 111.

So what if we were in another year, not 2011? If that year was 2000 or after, then the answer (as long as you were born before 2000) would be 100 plus the last two digits of the current year, as it is for 2011. If it was before 2000, then the answer would simply be the last two digits of the current year. You can work out for yourself what the answer is for someone born after 2000.

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February 2, 2011
bird

Quantum mechanics is usually associated with weird and counterintuitive phenomena we can't observe in real life. But it turns out that quantum processes can occur in living organisms, too, and with very concrete consequences. Some species of birds, for example, use quantum mechanics to navigate. Last year we talked to physicists Simon Benjamin and Erik Gauger for our article Flying home with quantum physics, and we found out that studying these little creatures' quantum compass may help us achieve the holy grail of computer science: building a quantum computer.

Now you can read all the technical details as Benjamin, Gauger and their colleagues has just published their research in Physical Review Letters. Their research has also been featured in New Scientist.

You can hear Benjamin and Gauger discuss their work in our podcast, and learn how birds have harnessed quantum physics in the accompanying article.

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January 21, 2011
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Negative numbers are easy to imagine if you think of the number line as a giant thermometer which includes sub-zero temperatures. This makes addition and subtraction easy, as you just move up or down the number line by the according amount.

But what about those tricky multiplication rules? Why does positive times negative give negative, and negative times negative give positive? Here the number line can help us too.

Suppose you're standing at the point 0, facing in the positive direction of the number line. You take two steps backwards and you do this 4 times. You end up at the point -8, showing that -2 steps times 4 is -8, ie (-2)x4=-8.

Now suppose you're back at 0, this time facing in the negative direction. You take 2 steps forwards and you do this 4 times. You also end up at point -8, showing that 2 steps times -4 is -8, ie 2x(-4)=-8.

Again, go back to 0, looking in the negative direction. Take 2 steps backwards and do this 4 times. You end up at the point 8. Stepping backwards gives you a -2. Facing in the negative direction gives you a -4. Putting all this together gives (-2)x(-4)=8.

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January 21, 2011

Straight Statistics is a campaign set up by journalists and statisticians to improve the use of statistics by government, the media, companies and everyone else who uses stats. On the Straight Statistics website you can find all sorts of interesting articles responding to stats as they come up in the news — whether it's lucky house numbers, the impact of bird flu, or your chance to reach your 100th birthday.

Have a look at www.straightstatistics.org/.

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