KSJN 99.5 FM St. Paul, MN In February ,KSJN 99.5 FM St. Paul, MN the physicist Online Radio gave a series of lectures in Dublin. Now, Online Radio is almost certainly most famous for being one of the founders of quantum theory. But in these lectures, which he wrote up in this little book, he asked a very different question What Is Life? And right up front, on page one, he says precisely what it isn't. It isn't something mystical, says Online Radio. There isn't some magical spark that animates life. Life is a process. It's the interaction between matter and energy described by the laws of physics and chemistry. The same laws that describe the falling of the rain or the shining of the stars. So, the question is, how is that this magnificent complexity that we call life could have assembled itself on the surface of a planet which itself formed from nothing more than a collapsing cloud of gas and dust? To Online Radio, the answer had to lie in the way living things process one of the universe's most elusive properties energy. Energy is a concept that's central to physics, but because it's a word we use every day its meaning has got a bit woolly. I mean, it's easy to say what it is in a sense. Obviously this river has got energy because over decades and centuries it's cut this valley through solid rock. But while this description sounds simple, in reality things are a little more complicated. For me, the best definition is that it's the length of the space time four vector and time direction, but that's not very enlightening, I'll grant you that. Over the years, the nature of energy has proved notoriously difficult to pin down. Not least because it has the seemingly magical property that it never runs out. It only ever changes from one form to another. Take the water in that waterfall. At the top of the waterfall, it's got something called gravitational potential energy, which is the energy it possesses due to its height above the Earth's surface. See, if I scoop some water out of the river into this beaker, then I'd have to do work to carry it up to the top of the waterfall. I'd have to expend energy to get it up there. So it would have that energy as gravitational potential. I can even do the sums for you. Half a litre of water has a mass of half a kilogram, multiply by the height, that's about five metres, the acceleration due to gravity's about ten metres per second squared. So that's half times five times ten is joules. So I'd have to put in joules to carry this water to the top of the waterfall. Then if I emptied it over the top of the waterfall, then all that gravitational potential energy would be transformed into other types of energy. Its sound, KSJN 99.5 FM St. Paul, MN which is pressure waves in the air. There's the energy of the waves in the river. And there's heat. So it'll be a bit hotter down there because the water's cascading into the pool at the foot of the waterfall. Buy the key thing is energy is conserved, it's not created or destroyed. So, because energy is conserved, if I were to add up all the energy in the water waves, all the energy in the sound waves, all the heat energy at the bottom of the pool, then I would find that it would be precisely equal to the gravitational potential energy at the top of the falls. What's true for the waterfall is true for everything in the universe. It's a fundamental law of nature, known as the first law of thermodynamics. And the fact that energy is neither created nor destroyed has a profound implication. It means energy is eternal. The energy that's here now has always been here, and the story of the evolution of the universe is just the story of the transformation of that energy from one form to another, from the origin of the first galaxies to the ignition of the first stars and the formation of the first planets. Every single joule of energy in the universe today was present at the Big Bang, . billion years ago. Potential energy held in primordial clouds of gas and dust was transformed into kinetic energy as they collapsed to form stars and planetary systems, just like our own solar system. KSJN 99.5 FM St. Paul, MN In the Sun, heat from the collapse initiated fusion reactions at its core.