What is energy? And why do we need it?

Nothing can exist without energy. Nothing is possible without energy. Despite being invincible and intangible energy can be stored. Such a fundamental physical quantity has no rigorous definition. Science texts empirically define energy as the capacity to do work.

- BY PROF. KIRTHI TENNAKONE

Plowing a paddy field, driving a vehicle or reading a newspaper are examples of numerous types of work we do and all these activities require energy. Production of things we need and our engagement in activities we desire demand energy. The world we live in is lively because of the work humans and other living organisms do, consuming energy.

Any kind of work always entails a temporal change in an existing situation, suggesting a relationship between energy and time. For centuries, philosophers and physicists have suspected a deep connection of energy to time. And later, the reason for the existence of a quantity we observe as energy was noted to be consequential to the fact that the physical laws of nature in the present, in the past and in the future are the same! If not for this fact we would not be able to live at present guided by past and looking forward to a future.

Moving things, heat, light, electricity and certain chemical substances carry energy and are usable as means to run machines and work. Different forms of energy are interconvertible; total energy remains constant during transformation. In 1905, Albert Einstein showed that matter and energy are interconvertible. We see this happening in nuclear reactions, but nobody knows why matter and energy are distinct. Present-day scientific theories find it hard to explain why matter exists instead of a universe permeated with radiation. A great thing about science is you can talk about many different things and establish precise relationships between them without knowing what they are.