Michael Sheringham's piece on "Archiving" was immensely rich and suggestive in its exploration of the city as a repository of memories, as "layer upon layer of compacted material detail". I was particularly struck by his idea that as well as the written history of a city, there is a unique and personal history experienced by each inhabitant - the Tube station where you met your lover on the first date, the street where a grandparent used to live, the anonymous office block where you used to work. The city's street corners are dense with histories both written and unwritten. The city, says Sheringham, is "a memory machine."

It reminded me of Calvino's beautiful fantasy, Invisible Cities, in which he says that a city’s past is written into its fabric like the lines on a labourer’s hand, “in the corners of the streets, the gratings of the windows, the banisters of the steps, the antennae of the lightning rods, the poles of the flags, every segment marked in turn with scratches, indentations, scrolls.”

You can read my review of Restless Cities on the Guardian's website.

Twitter is also very useful. I've made contact with many people who share my fascination with the subject I'm researching for my next book - the history and future of cities. I've listed nearly a hundred of these people here. I recommend them - they're well worth following.

It looks like some people have found my tweets useful too: the other day the cultural news website Flavorwire included me on a list of the "10 Book Types You Should Follow on Twitter". Quite an honour when you think it includes people like Sarah Weinman (@sarahw), Ron Charles(@roncharles), the Washington Post’s fiction editor, as well as book website The Millions (@The_Millions).

Oh, and by the way - I have my own list of book people to follow on Twitter here. So what are you waiting for?

I have to say I was initially sceptical, not to say cynical, about the whole idea. As Will Wiles (@WillWiles) said, it seemed a bit too much like "panhandling". Science fiction author Tim Maughan (@timmaughan) was similarly negative about the idea. 

But having thought about this and listened to Deanna's side of things I see that it certainly can work. Although, as she says, it clearly works best if you are talking to a community that is open to this approach. I'm not sure it would work for the kind of cultural history books I write, for example.

Tim Maly (@doingitwrong), co-founder of Capybara Games, pointed out the advantages of this way of funding books and other artistic projects. As he said, if it works for Robin Sloan (@robinsloan) at Kickstarter, why shouldn't it work for other authors?

Anyway, it's an interesting debate and Tim Maly has collated the various comments from people and written a fascinating blog on the issues it raises which is well worth reading.

Michelle Pauli (@michellepauli) at the Guardian has also written a rather more sceptical piece highlighting the ethical problems involved. For example, she points out that "as [Deanna Zandt] is writing about social networking it might be relevant to the reader to know if, for example, the MD of Facebook has contributed a large sum to the writing of her book".

One nagging fear I have about crowdfunding is that if it catches on then publishers may stop paying advances altogether. Authors are already having to make do with much lower advances. And today I see in The Bookseller that an agent has struck a deal where there is no advance and the profits are split between author and publisher.

Perhaps the new age of the eBook will change things, allowing authors to reach untapped audiences and making writing more rewarding. I hope so. If not then crowdfunding books may well be the only option for some authors.

"This copy is the first one which left the printer. It was sent to me by Prof Einstein the moment he had received it, and shortly before I went to France with the army. Hans Mühsam, Berlin, at present at the French Front, April 1917."

The idea of Mühsam taking this copy of Einstein's book with him to the hell of the trenches in the First World War is deeply moving. It speaks volumes about the power of scientific ideas.

You can see the title page of Einstein's book here and read my review here.

It's based on research I'm doing for my next book which explores the past, present and future of cities. Here's a taster:

"For the first time in history, more than half the world's population live in cities: by 2030, three out of five people will be city dwellers. But the British are bucking this trend. The 2001 census revealed an "exodus from the cities". Since 1981, Greater London and the six former metropolitan counties of Greater Manchester, Merseyside, South Yorkshire, Tyne and Wear, West Midlands and West Yorkshire have lost some 2.25 million people in net migration exchanges with the rest of the UK; in recent years this trend has accelerated. This is not sustainable. British people need to be cured of the insidious fantasy of leaving the city and owning a house in the country: their romantic dream will become a nightmare for people elsewhere on the planet."

There's also a great piece by science fiction author Paul McAuley on the technological changes that could make cities carbon neutral:

"From the air, the ideal green city should resemble Mayan ruins poking out of a lush forest. Under the canopy, there'll be densely populated but diverse and vibrant streets humming with every kind of human life. Utopian? You bet."

Read my article here and Paul's here.

"Some physicists suggest that when billions of pounds have been spent on the kit to probe such ideas, there is little need to invent new ones about time travel and self-sabotage. History shows, however, it is unwise to dismiss too quickly ideas that are initially seen as science fiction. Peter Smith, a science historian and author of Doomsday Men, which looks at the links between science and popular culture, points out that what started as science fiction has often become the inspiration for big discoveries."

Read the rest here.

The launch was monitored by the West’s spy satellites. But it was an unexceptional moment in the history of the arms race and soon forgotten. Only after the Berlin Wall had been breached, and the ice of the cold war began to thaw, did military analysts realize the significance of these otherwise unexceptional rocket launches. They were the first operational test of what the Western press later described as ‘Russia’s doomsday machine’.

In my book Doomsday Men, I showed how popular culture played a vital role in inspiring the dream of the superweapon, a dream that in the nuclear age turned into the nightmare of mutually assured destruction, or MAD.

More than any other weapon, it was Leo Szilard’s chilling notion of the cobalt bomb (first described on American radio in 1950) that came to symbolize the threat of global nuclear destruction. The C-bomb consisted of one or more massive hydrogen bombs jacketed with cobalt. It was the ultimate weapon, a doomsday device which could spread radioactive fallout across the entire planet.

As throughout the history of superweapons, fiction and film played a key role in exploring the horrific implications of the C-bomb and how it could be used to create a doomsday machine, most famously in Peter George’s best-selling thriller Red Alert (1958) and Stanley Kubrick’s cold-war classic (based on George’s novel) Dr Strangelove or: How I Learned to Stop Worrying and Love the Bomb (1964).

As Ambassador DeSadeski explains in Dr Strangelove: ‘If you take, say, fifty H-bombs in the hundred megaton range and jacket them with cobalt thorium G, when they are exploded they will produce a doomsday shroud. A lethal cloud of radioactivity which will encircle the earth for ninety-three years!’

Twenty years after Kubrick’s film depicted the world being destroyed by a Soviet doomsday machine, the real one became operational. Nicknamed by its commanders ‘The Dead Hand’, it was a sophisticated system of sensors, communication networks and command bunkers, reinforced to withstand nuclear strikes. At its heart was a computer. As soon as the Soviet leadership detected possible incoming missiles, it activated the system, known by its code name ‘Perimetr’. Part of the secret codes needed to launch a Soviet nuclear strike were released and the computerized process set in motion. Then, like a spider at the centre of its web, the computer would watch and wait for evidence of an attack.

As I said in my book, the way it worked was strikingly similar to the doomsday machine described by Dr Strangelove. He explained that the computer was ‘linked to a vast interlocking network of data-input sensors which are stationed throughout the country and orbited in satellites. These sensors monitor heat, ground shock, sound, atmospheric pressure and radioactivity.’

Much about the Dead Hand system is still shrouded in secrecy. Russian arms expert Bruce Blair revealed the first details in 1993. Recently declassified interviews with former Soviet officials have cast fresh light on the system. They show that there were doubts about its reliability. Some even questioned whether it was ever fully deployed. However, these interviews also reveal the shocking possibility that the Dead Hand system may have been fully automatic.

Previously it was thought that once the computer detected signs of an attack, it required human approval before any counter attack could be launched. A Soviet officer buried deep underground in a command post would have had the unenviable task of authorising the Dead Hand to complete its lethal task. But these interviews raise the possibility that the Dead Hand had eliminated the need for any human control. It may be that the Dead Hand could launch the entire Soviet nuclear arsenal as soon as its sensors indicated that an attack had occurred. That idea is truly terrifying.

A machine would be responsible for unleashing nuclear weapons with a total destructive power as much as 50,000 times greater than the bomb that destroyed Hiroshima. Even without Szilard's C-bomb, who knows what would be left alive after such a nuclear holocaust.

Intriguingly, Nicholas Thompson, writing in Wired today, argues that Perimetr was actually designed ‘to keep an overeager Soviet military or civilian leader from launching prematurely during a crisis’. In other words, it was an insurance policy meant to reassure the Kremlin’s hawks that their country could hit back, even after a sneak attack by submarine launched missiles, which would have given the Soviet leadership barely thirteen minutes advance warning of a devastating attack.

As far as anyone knows, the Dead Hand remains operational. What is truly worrying, even today, is the secrecy that continues to surround the whole subject. Thompson has found that neither George Schultz nor former CIA director James Woolsey had heard of the Dead Hand system. Former Soviet era officials will still not discuss it. One who dared to talk died in mysterious circumstances. Such secrecy is, as Dr Strangelove realised, disastrous: ‘Yes, but the...whole point of the doomsday machine...is lost...if you keep it a secret! Why didn’t you tell the world, eh?’

The doomsday machine is supposed to be the ultimate deterrent. But if no one knows that the deterrent exists... Well, you've all seen the final scenes of Dr Strangelove.

Their new book shows that, as well as a 24-hour clock, organisms contain a circannual clock with a periodicity of a year. These two studies provide a remarkable glimpse into the working of nature's inbuilt timing mechanisms. You can read my review of Seasons of Life here.

Unfortunately, I had to admit that I have no connection whatsoever with snails. I don't even eat them. She took it well though.

You can read the interview here.

"I suppose the story of the Doomsday Men has been a constant background to my life. Most of the time I have successfully pushed it to the back of my mind because it seemed too frightening and too impossible to be true. But reading the Doomsday Men has forced me to confront it and understand. Recently the threat of weapons of mass destruction has been overshadowed by natural plagues, global warming and economic crisis, but it is still there. It can still happen."

You can read the rest here and also watch Peter Watkins's The War Game (1965) .