Resources

View of a small region of the Sun which is cooler and less luminous than the rest

Artist's interpretation of the x-ray burst of a neutron star which is the dead core of a massive star

The dark gap between the accretion disc and the black hole represents the stable orbits that matter have before plummeting into the black hole. A spinning black hole allows matter to orbit closer to the black hole than in any other case.

Mass and volume. Confusing? Discover the answers related to these fundamental concepts in an enjoyable way with the help of this interactive exhibit. Weigh eight different materials with identical mass. What do you observe about their volume?

The eye is sensitive to the rays of the visible spectrum, to be sure, but it is also sensitive to those that are invisible, and in particular to ultraviolet rays. Ultraviolet radiation (UVA, UVB, UVC) has a great many beneficial biological effects (photoprotective pigmentation, vitamin D synthesis) but it also presents a danger to the eye and the skin. Using a spectrophotometer we can measure the percentage of visible rays and UV rays that passes through a sample, and see whether the material blocks the rays or not, and if so, which type.

Some materials have the permanent property of producing a magnetic field around them. This is due to the permanent orientation of mini-magnets which make up their structure. Such materials as iron, nickel and cobalt have a magnetic sensitivity, others, such as aluminium, copper, and graphite, do not. In the presence of a magnet, materials sensitive to magnetism are themselves converted into magnets.

Some materials have the permanent property of producing a magnetic field around them. This is due to the permanent orientation of mini-magnets which make up their structure. Such materials as iron, nickel and cobalt have a magnetic sensitivity, others, such as aluminium, copper, and graphite, do not. In the presence of a magnet, materials sensitive to magnetism are themselves converted into magnets.

Some materials have the property of producing a magnetic field around them (magnets), others will only display this property when an electric current runs through them (electromagnets). These materials repel or attract each other, so they can be used to convert electric energy into motion proportional to current.

Some materials have the property of producing a magnetic field around them (magnets), others will only display this property when an electric current runs through them (electromagnets). These materials repel or attract each other, so they can be used to convert electric energy into motion proportional to current.

Materials behave differently when an electric current passes through them. Some allow the current to pass through easily (copper), others are more resistant (lead or titanium) but are still conductors. Finally, some materials such as wood or glass stop the current: they are insulators. Many everyday applications are based on these three categories.

Liquid crystals have the form of a fluid material midway between a crystalline and liquid state. Their molecules change directions when an electric current runs through them. This property can be used to block light or to let it through. Here, liquid crystals are sandwiched between two sheets of glass. When there is no current, the glass is opaque. When a current is applied, the liquid crystals all move in the same direction and let the light through so that the glass become transparent. This procedure has applications in the manufacture of windows for cars and buildings.

By integrating microcapsules containing a dye into a fabric’s fibres, it can be made to change color as a function of the temperature. When heated to a certain temperature, the dye breaks down and become colorless thereby letting the color of the fibres through. The reaction is reversible: when the temperature drops, the dye re-forms and gives the fabric its initial color back.

Shape-memory alloys are materials that have the property of changing crystalline structure under the action of heat so that after deformation they recover a previously “memorised” shape at a predefined temperature. Shape-memory materials have applications in a variety fields including aeronautics (components for wiring), and medicine (blood vessel prostheses, valves, clamps, etc.).

Shape-memory alloys are materials that have the property of changing crystalline structure under the action of heat so that after deformation they recover a previously “memorised” shape at a predefined temperature. Shape-memory materials have applications in a variety fields including aeronautics (components for wiring), and medicine (blood vessel prostheses, valves, clamps, etc.).

The past century has been an age of miniaturisation made possible by progress in the design of components, the discovery of semiconductors and the emergence of microelectronics and nanotechnology. The average size of electronic circuits has decreased by 30% every two years over the past few decades. A transistor that measured a few microns in 1970 measures less than hundred nanometres today. Anticipating the limits of silicon technology, molecular electronics is opening up new prospects with the manufacture of nano-objects