The standard minimum cage size recommended by bird professionals is 12- by 18- by 18-inches for a single bird. This cage size is fine if your budgie is outside of the cage most of the time, but if you have a cage-confined budgie, it's going to be much too small to keep your bird happy and healthy.For two budgies, 39- by 20- by 32-inches is a recommended size.ousing your budgie is an important aspect of his care requirements. The size is one of the most important things to look at when setting up your little guy's cage.
Differences between Optical and Radio Astronomy. There are many differences between optical and radio astronomy. The three main differences are the design of the instruments, the resulting data that is found, and the different sources that are seen. Both optical and radio astronomy use telescopes; however, there is a big difference in the design between an optical telescope and a radio telescope. Optical astronomy is the study of the visible part of the electromagnetic spectrum, that is wavelengths of approximately 400 nm (purple) to 700 nm (red). Radio wavelengths are much longer; the radio spectrum ranges from approximately one millimeter to hundreds of meters.
Astronomy is a study of the stars, planets and other phenomenon in space. Since the first humans looked at the skies, there has been astronomy. Many people have been significant over the years, like Copernicus and Galileo, and many individuals have made special contributions to astronomy, but you can't say when astronomy began.