echanics has been defined as the “science of forces, equilibria and motions of bodies”. The fundamental laws of mechanics were first enunciated by Newton in the 17th century. In the early part of the 20th

century, the theory of relativity and quantum mechanics were formulated to extend the classical laws to the larger cosmos, and the minute world of atoms and electrons, respectively. Mechanics lies at the heart of mechanical engineering. Here its principles, allied with other sciences such as thermodynamics and materials, have been applied to transform nature’s raw materials into useful products and devices. In the last twenty years, three discernible technological trends have greatly influenced the direction of mechanical engineering research beyond its more traditional concerns with machines and production. The first is increasing use of computers to model complex physical processes. The second is 'engineering in the small', and the third is the growing convergence of engineering and the biological sciences. Amidst these developments, the well established science of mechanics may seem like ‘old science’ to some people. But the reality is that the world at all levels is ultimately governed by the inviolable principles of mechanics, and much of what we design and build are underpinned by the laws of mechanics.

With the rapid growth in computing power, many complex problems in mechanical engineering that were previously not amenable to analyses, such as stress analysis for complex components, can now be modeled and solved routinely. Increasingly, computer modeling has replaced expensive experimentation in product design, and experiments are reserved for confirmation of the final prototype. Computers are also now being applied to model the behaviour of solid and fluid materials down to the molecular and atomic levels (see Figure 1). These are used to engineer materials with desired mechanical and other properties, and to improve processing of materials, as in metal cutting and molding. The ability to model these complex physical processes on computers down to the nanoscale level is matched only by our ability today to manipulate atoms and probe surfaces with recently invented devices such as the scanning tunnelling and atomic force microscopes. Further, we can handle individual biological cells with laser tweezers and create microscopic electro-mechanical devices and systems (MEMS), such as micro-scanners and embedded systems, using the same silicon-based technology that is used to create micro-processors that run at several gigahertz with access to several terabytes of storage. Moreover, to bridge the divide between the nano world of atoms and molecules with the macroscopic world that we are accustomed to, researchers have also been developing multi-scale models to couple the mechanics of the two worlds.