The Kremlin Cat

In recent times there have been Socks Clinton and then India Bush in the White House, and Humphrey, Sybil and Larry in Downing Street. From 7 May 2008 there was also a feline presence in the Kremlin. When Dmitry Medvedev took over from Vladimir Putin (who has a Labrador dog called Conni) as Russian president on that date, his wife Svetlana's cat Dorofei (Dorotheus) moved into the official residence.

Dorofei is a blue-eyed Siberian colourpoint, a breed now known as the Neva Masquerade, chosen by Svetlana — or some say he chose her — from a cat breeder in about 2004. It's reported that at one time the Medvedevs lived near Mikhail Gorbachev, former leader of the Soviet Union, who also had a cat, and the two felines got into a fight. According to Moscow's daily newspaper Moskowsky Komsomolets, the Siberian came off second best and had to be given antibiotics for a month to recover his health. More drastically, he was then neutered to discourage future fighting.

This information is from the online English version of Pravda.

President Obama meets Dorofei

On a trip to Gorki, outside Moscow, in July 2009 to meet Russian president Dmitry Medvedev for political discussions, President Obama and First Lady Michelle encountered Dorofei. The cat looks friendly, but we don't know whether the visitors approached any closer or said 'hello' to Dorofei. Meanwhile White House dog Bo remained at home.

Photo by Mikhail Klimentyev/AFP/Getty Images

Note: from May 2012 Medvedev was no longer president of Russia, but remained in government as prime minister.

Schrödinger's cat

It's not a real cat — but part of a paradox, a thought experiment, presented by the famous Austrian physicist Erwin Schrödinger in 1935, aimed at demonstrating how the ultra-small-scale world of quantum mechanics impinges on the large-scale human world.

A healthy cat is shut inside a steel chamber that is windowless and completely soundproof. In the chamber also are a radiation monitor and a minute quantity of a radioactive substance — so small that over the course of one hour there is a chance that one of its atoms will decay and emit a radioactive pulse. If that happens, the radiation monitor will detect it and will trigger a hammer, which will fall onto and smash a small glass flask containing a lethal gas. Just the tiniest amount of the gas inhaled by the cat will cause it to die instantly.

However, there is an exactly equal probability that none of the radioactive atoms will decay during the hour, and so the hammer will not be activated. We are not allowed to look inside the box, or to install any form of cameras or microphones — so if the system is left to itself for an hour, what can we know about the cat's fate? The answer is we cannot know anything without opening the box, when the cat will be either alive or dead. Until that time, there is a 50/50 probability of one state or the other.

According to the laws of quantum mechanics, the cat's state of being alive or being dead is tied to the decay or non-decay of one single atom — and that process is subject to quantum uncertainty. The cat, isolated from the outside world, can be said to be neither alive nor dead during the one-hour period; it exists in a potential cloud or 'superposition' of both possibilities at once. The idea behind the slightly gruesome scenario is to show that we cannot talk about subatomic particles being neither in one state nor another, unless we also consider larger things being in neither one state nor another. Quantum mechanics truly describes a bizarre world, quite at odds with our understanding of how things work in our everyday life!

Schrödinger's 'cat-in-a-box' idea has generated a number of jokes, such as:

• As every cat owner knows, the cat has three states: alive, dead and b----- furious.
• And of course; the cat always dies because the box in every diagram has no air-holes.
• Having dated physicists, this researcher can confirm they all own cats.