Someone asked, Is the people flying on the plane younger than the people on the earth? Actually, this is a classic problem in Einstein's theory of relativity. One hundred years, scientists have conducted various test to research and demonstrates the theory of relativity. Now, You can use the iPhone to compute relativistic clock delay effect. According to the special relativity theory, time dilation effect, the speed more faster, the clock slower. According to the general relativity theory, gravitational redshift effects, more farther from the inner earth source (gravity), the clock more faster. Therefore, whether younger on the plane, and the speed of time, depending on your location, direction, speed, height, also depends on who you compare with. Assumptions on the equator (the geoid) placed a clock (equator clock), you are in flight or high speed movement also carry a clock (iPhone), you can use this App to calculate time speed to the equator clock, also statistic how young or old relative to the people living at the equator. [Function] 1, Manual input motion parameters, compute relativistic clock effect, including gravitational redshift and time dilation effect. 2, Use the iPhones GPS sensor, automatic computing relativistic clock effect. 3, Show your current location, direction, speed, and support show your location on the map. 4, Support store every results, and show in the history list. 5, Summary clock slow numerical statistics, and show it with a chart. 6, support for background running. 7, No IAP, No Ads. [Note]1, When using the App records relativistic effects, please set iPhone point to the moving direction.2, The automatic calculate function, need to open the GPS, may need to consume extra power.3, Continued use of GPS running in the background can dramatically decrease battery life.[Usage] Using the Apps function, you can answer the following questions: 1, the moving clock must be slow than the static one? 2, Whether the westward flying clock and the eastward one shows consistent?3, the clock on the ground is more slowly than in the air?