Time or money

It was about 20 years ago.


Engineering electronics students at Warwick university were attending the lecture physical electronics by proffesor Parker.


There was on the green board some equation relating temperature and what happens inside a semiconductor.


The electrons have some kinetic energy so that the temperature is such and such. But the proffesor paused and asked all the students where is this energy coming from so that a semiconductor can be at room temperature for example.


About 10 minutes passed, everyone replied yet no one got the answer correct.


Proffesor Parker had to give the answer.


The sun.





And now on the title of this post.


Energy must be a first notion, cannot be defined. Perhaps like time.


Other first notions can be in geometry, a point, a line. They are prime notions. They can't be defined. But there are axioms that help us understand them. Axioms are sentences taken to be true. For example, from 2 points in space one and only one line passes through.


Getting back to the sun. If some amount of energy is sent in one second to earth, about the same energy much be sent in the next second etc.


We don't know what energy is. But power is defined as energy per unit time. Or in mathematical terms Power is the first derivative of Energy with respect to time. Or the slope at any point if we plot the graph: energy versus time.


Rearranging Energy is Power times Time, E = P x time or E=Pt


The sun generously gives to earth in a sunny day 1000 Watts per square meter. Or 1000Joules of energy per second per square meter.


Every square meter gets 1000 more Joules every second.


Every square meter becomes richer by 1000Joules more every second.


Time is money.


Money is energy. Perhaps this is why this blog os called euroelectron.


The energy from the sun is free.