Most of our discoveries about the universe have come through collecting and studying electromagnetic radiations. For many centuries, visible light waves were the only kind of radiation we could detect, and we could not do much with them until Galileo constructed his telescopes. But the electromagnetic spectrum holds much more information than that contained in the light waves visible to our eyes. The full spectrum ranges from very long radio waves, microwaves and the infrared, through the rainbow’s hues, to ultraviolet, X-rays, and highly energetic gamma rays. Our ability to understand what is happening throughout the universe depends upon our ability to invent, build and utilize instruments able to gather in these waves, remove spurious background noise, then to amplify, analyze and make sense of the minute differences so revealed. The past few decades have opened many electromagnetic inspection windows, and the next will undoubtedly open many more. Thus, what follows in this chapter will certainly need to be updated as we learn more, but the chapter’s major premises will likely remain valid, for they are supported by many millions of solidly based observations.
Let us begin this explanation of what has been discovered about the universe by describing just a little of what everyone can readily see. We will then use the laws of physics and the “causality principle” to extrapolate backwards in time; this reveals how things must have been in the past to cause them to be as we see them today.
- What We See In The Sky
- The Expanding Universe
- What Happened After The Big Bang
- The Life Of A Typical Star
- The Earth
- What Started It All?