These days you can just about crush an individual ant with a missile fired from the other side of the planet, but it wasn't always like that. Accuracy used to be much worse, especially on the Soviet side. At the time the Tsar Bomba was developed, you might be lucky to get your bomb within a mile or two of your target. Even bombers were frequently way off target.

Then consider that a lot of the targets are hardened military targets, not cities. Destroying cities was always either incidental (they contained or were near military/political targets) or a last resort (convince the enemy not to attack by threatening his population in retaliation). Primary targets were (still are!) things like airbases, missile silos, and command centers. Many of these are hardened targets. A more normal-sized nuke going off a mile or two away from the intended ground zero will still wreck a city, but a missile silo can take it. If you want to be sure of getting targets like that, you either need to be a lot more accurate or you need much more powerful bombs. Accuracy wasn't possible at the time, thus huge bombs.

If you look at the evolution of nuclear arsenals, it was a race to bigger and bigger bombs until sometime in the 60s, at which point accuracy started improving greatly and the bombs got smaller again. For example, the US fielded lots of 9 megaton bombs in the 60s, but now the typical weapon in the US arsenal is under one megaton.

I guess it will get you on a list of nuclear history enthusiasts. Apart from that, this sort of thinking is really just mild paranoia. While I recognise that the NSA monitoring is a big deal, I don't think that it can be extended to mean that ordinary people accessing sites like this will become targets.

So, don't worry, and go ahead and access the site, and also read the guy's blog - it's very interesting.

Not sure I would agree with that - a single 800kt detonation over Manhattan looks pretty bad to me and a realistic attack would probably have had many tens of warheads used.

Here is a rather jolly 1980's BBC documentary that spends a lot of time looking at the effects of a single 1Mt warhead on London:

https://www.youtube.com/watch?v=vejorfkdgwU

Of course, it does finish by noting that a real attack would have multiple ground and air bursts.

[NB UK("pretty bad") == NonUK("utterly appalling")]

And yet if you are just 30 miles from the target the first time you are going to notice is when you turn on the TV.

Mind you, although the Soviets did have 25Mt warheads on ICBMs they were targeted on key bunkers - Cheyenne Mountain, Raven Rock Mountain etc.

The area of severe damage and less instant fatality is maybe twice as wide.

Outside of that there's another ring of significant damage, but the probability of survival increases (as long as you're not near a window when the shockwave hits.)

The map also doesn't show fall out or the effects of a possible firestorms.

It's an option you can select - you can also set wind speed and direction (drag the windsock icon about). You also need to make sure it is a ground burst as an air burst won't produce much fallout.

No—no it's not. See "What would happen if an 800-kiloton nuclear warhead detonated above midtown Manhattan?" (http://thebulletin.org/what-would-happen-if-800-kiloton-nucl...). Notice this:

No survivors. Within tens of minutes, everything within approximately five to seven miles of Midtown Manhattan would be engulfed by a gigantic firestorm

Furthermore:

The fire would extinguish all life and destroy almost everything else. Tens of miles downwind of the area of immediate destruction, radioactive fallout would begin to arrive within a few hours of the detonation.

Manhattan has a daytime population of more than two million people.