The center of an atom is held together by powerful forces. This gives them a huge amount of stored energy. This type of energy is called nuclear energy. This energy can be released and used to do work. This happens in nuclear power plants where they split apart the nucleus of an atom. This splitting apart is called nuclear fission. Another type of nuclear energy happens in the Sun. Here the atoms nuclei are not split apart. Instead, the nuclei of the atoms are fused, or joined together. This process is called nuclear fusion. Some of the suns energy travels to Earth. This energy from nuclear fusion warms the planet and provides the energy for photosynthesis.

What are the 2 processes called to form nuclear energy?

Captured Moments by Will Shetterly I remember Papa's stopbox, a teal blue Tiempo Capturado that Mama brought home for his birthday. It was huge and inefficient, and she should never have spent so many pesos on a toy, but Papa would not let her return it. He used it to preserve baby tomatoes, cucumbers, and strawberries in translucent cubes that he stored in the pantry for spring-time meals in the middle of winter. Mama kept her mink jacket, a family hand-me-down, safe from time in a stopbox, and lent the capturador to my uncle for his stamp collection. Sometimes they would let us little ones to seal a treasured toy or a last piece of birthday cake until we begged them for its release, usually a few hours after enclosing it. When my father died, a year after my mother, my sisters and I cleaned out their apartment. We found our baby shoes protected in stopboxes. I took mine home, where they sat above my computer while I worked on my first play. One night when I did not believe love had ever existed for anyone, I used my own capturador, a sleek titanium Sanyo Tardar Ahora, to undo the stopbox. Bringing my face close to the shoes, I breathed deeply of air that my parents had trapped while closing up that symbol of their love for me. The instant would have been improved had my baby shoes been cleaned before they were encased. But as soon as I coughed, I laughed, and I did not try to kill myself that night.

What made the speaker cough?

Fossils can be used to match up rock layers. As organisms change over time, they look different. Older fossils will look different than younger fossils. Some organisms only survived for a short time before going extinct. Knowing what organisms looked like at certain times also helps date rock layers. Some fossils are better than others for this use. The fossils that are very distinct at certain times of Earths history are called index fossils. Index fossils are commonly used to match rock layers. You can see how this works in Figure 2.30. If two rock layers have the same index fossils, then they're probably about the same age.
How are index fossils used?