Lecture 2 – To the centre of the sun

From the 1993 lecture programme:

The Big Bang, happened 20 billion years ago. Over 100,000 years elapsed before the Universe was cool enough for atoms to survive; their seeds — the atomic nucleus — were cooked in stars, but the simplest examples were already formed within about 3 minutes of the Big Bang. Much of what we see happening around us day by day at home and at work involves atoms and molecules — the stuff of biology and chemistry. Moreover, the stars, such as the Sun, are nuclear physics in operation — their central heat is like the Universe when only a few minutes old.

The first signs of the atomic nucleus come with radioactivity. Everything is radioactive to a greater or lesser extent. You can hear radioactivity by means of Geiger counters; you can see its radiation by means of a cloud chamber, or by the dark trails when a speck of radium is dropped onto a photographic emulsion.

We can photograph nuclear collisions and nuclear transmutation by means of a cloud chamber and see how to “weigh” the nuclei of different elements by means of atomic billiards. Many nuclei are magnetic and send out radio signals. This “nuclear magnetic resonance” can be used to produce images of the brain at work.

By learning about atomic nuclei, how they behave, form and change, we begin to understand how the stars and, in particular, our Sun produce their power.






Frank Close



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