| Energy equals mass times the speed of
light squared. This is the famous equation of Albert Einstein. It{{U}} (51)
{{/U}}to the category of the theory of relativity, and it equates energy
with mass. All things are made up of atoms. When{{U}} (52) {{/U}}of an atom travels at almost the speed of light{{U}} (53) {{/U}}we put more energy into it to increase the speed, it begins to in crease in mass. The energy that makes it travel fast cannot make it travel{{U}} (54) {{/U}}the speed of light—nothing{{U}} (55) {{/U}}light can travel that fast- so the energy goes into the thing{{U}} (56) {{/U}}and increases its mass. Energy{{U}} (57) {{/U}}into mass. Why is the theory called the theory of relativity? A thing that is relative depends upon{{U}} (58) {{/U}}else to identify it or to define it. In relativity theory we identify or define mass, time, and length{{U}} (59) {{/U}}to the speed of light. When something is at rest, it looks{{U}} (60) {{/U}}in length. However, when it travels at almost the speed of light, it becomes{{U}} (61) {{/U}}. Time also changes. However, the change in time is{{U}} (62) {{/U}}to the change in length. The length of a thing becomes short{{U}} (63) {{/U}}time becomes long. If you want to{{U}} (64) {{/U}}young, relative to a friend, take a trip in a spaceship that travels at{{U}} (65) {{/U}}the speed of light. And, although time and heartbeat seem ordinary to you in the spaceship, when you return, look at your friend; Relative to you, he or she is old. |