September 27th - Wednesday - Science - Forbes - B1
We’ve covered topics, in the first seven weeks, designed to help us understand the things that came together to make life possible on Earth - and, perhaps, elsewhere in the galaxy and universe. Some of the main points up through today.
- One way we (Hubble) concluded that the universe began in a BIG BANG, 14 billion years ago, was by graphing the data comparing the speed with which galaxies are moving apart versus the distance away from us. Running this backwards in time it seems that everything was together at the same place and at the same time, about, 14 billion years ago.
- Our Earth has all the elements necessary for life. But, after the Big Bang, these elements did not exist! Instead, most of the universe was Hydrogen. (and still is!) Stars are large balls of hydrogen - pulled together because of gravity - that fuse (combine) hydrogen into larger elements like Carbon, Helium, Lithium, and Oxygen. When a star explodes - at the end of its life - all the elements on the period table are made.
- When Earth formed, along with our Solar System, pervious generations of stars had made enough heavy elements so complicated chemistry could take place here, and on other planets in our system.
- Chemistry is the study of how atoms combine to form compounds and molecules. Nuclear reactions are different from chemical reactions. In chemical reactions the atoms are rearranged. In nuclear reactions some mass is lost as it is converted directly into energy. (Also, the element is transmuted, or changed, because the number of protons changes.) In biology we, mainly, concern ourselves with chemical reactions. However, we also have to know about nuclear reactions because the sun (which powers photosynthesis) is powered by nuclear reactions. Also, nuclear reactions (radioactive decay) helps us determine the age of some fossils and rocks. We even use radioactive elements in medicine (cancer treatment and diagnosing disease),generating electricity (nuclear power plants), and it is because of radioactive decay that our Earth maintains heat inside and helps life evolve and thrive by recycling materials through the process of plate tectonics.