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subject to availability. Thank you, Professor, for doing this. Let me start with the most simple of all

questions. How are nuclear weapons different from conventional weapons? Nuclear weapons are different from conventional weapons in many ways. One of the things

that I like to say is that they really defy the kind of concept of both space and time.

And let me explain what I mean by that.

If you have a conventional weapon and you exploded over a city, wherever, that explosion is going

to have an impact in that local place, and it's going to have that impact in time.

And then you could come back and clean up the area and rebuild and so on.

Nuclear weapons are not like that.

A nuclear explosion in one place, in one location, and in one split moment of time can have both global effects,

and it can have impacts over actually even thousands of years

through the effects of radiation and the kind of radioactive isotopes that get deposited in the environment. But there are sort of a number of ways in which even a single nuclear weapon explosion can be incredibly dangerous and devastating.

And then there's a number of impacts in which a nuclear war, in which many nuclear

weapons are used, can be obviously quite clearly much more devastating.

So the thing that people know about nuclear weapons is the one nuclear weapon can be much more powerful than any kind of chemical explosion.

So, for example, the atomic bombings of Hiroshima and Nagasaki.

80 years ago.

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