Introduction to general relativity in a setting with comparatively strong gravitational fields. This has become possible thanks to precision observations of binary pulsars. In such a star system, two highly compact neutron stars orbit each other. At least one of them is a pulsar – an astronomical object that emits a tight beam of radiowaves. These beams strike the Earth at very regular intervals, similarly to the way that the rotating beam of a lighthouse means that an observer sees the lighthouse blink, and can be observed as a highly regular series of pulses. General relativity predicts specific deviations from the regularity of these
Electron-beam machining to about 200,000 km/s. Magnetic lenses are used to focus the electron beam to the surface of the work-piece. By means of electromagnetic deflection system the beam is positioned as needed, usually by means of a computer. Vacuums must be used to reduce contamination, and minimize electron collisions with air molecules. Because work must be done in a vacuum, EBM is best suited for small parts. The interaction of the electron beam with the work piece produces hazardous x-rays, and only highly trained personnel should use EBM equipment. Electron-beam machining Electron-beam machining (EBM) is a process where high-velocity electrons concentrated