Expert: Steve Nelson - 4/23/2009

Question
Hello sir, I was wondering if you could clarify something for me.

I know that in physics energy means the ability to do work or cause change. But when you apply that definition to string theory, to me it doesnt make sense. String theory says everything is made of tiny vibrating strings of energy. How is that possible? Strings of ability to do work and cause change? And also, the big bang theory says the universe was compressed into a singularity and it was only made of pure energy. It was made of ability to do work and cause change?

Could it be that energy is made of something? I hope you can help clarify this for me.

Thank you.

Answer
The problem here is that you've latched onto a somewhat simplistic definition of energy.  Energy is a physical thing, equivalent to an amount of mass...E=mc^2 (the most famous equation in physics).  It's not just an ability, it's an actual physical thing which is quantifiable.  It's not just an ability to do work or cause change, though it does have that as one capability to do both those things...in specific amounts of work.  Work IS a form of energy.  Heat is a form of energy.  Light is a form of energy.  So any little unit of energy is a physical thing, just like bits of matter.