"fifteen hundred years ago everybody knew the earth was the center of the universe. five hundred years ago, everybody knew the earth was flat, and fifteen minutes ago, you knew that humans were alone on this planet. imagine what you’ll know tomorrow.” that's a statement of agent kay in from men in black. agent kay's statement illustrates that theories are a) always true. b) constantly changing. c) describe what happens in the natural world. d) are proven by evidence collected by scientists.

Which of the following represents an upside-down image?

This is the number of complete movements of a wave per second.

You have two photos of a person walking. one shows the person at the corner of third and main streets, the other shows the person at the corner of tenth and main streets. there are lampposts at every corner in this town, and the first picture shows it to be 10: 32: 00 exactly. the second picture shows it to be 10: 49: 30. you know three facts: (1) all of the clocks are synchronized; (2) there are exactly 12 equal-sized blocks per kilometer in this town; and (3) the streets that cross main in this area are numbered consecutively, with no interruptions. what is the person’s average speed in kilometers per hour?