Why Time Runs at Different Speeds
Written by Studio AM.
Your result
- Words per minute
- Score
- Pace
Words per minute mean something only with the score beside them. They describe this passage on this read. With fewer than 3 right, try the next slower pace.
Choose a pace and select Start. The passage is paced and timed, then the questions check what you understood. How pace mode works
Reading time 0:00
Two clocks can begin together, take different journeys, and disagree when reunited. This is not a fault. In relativity, elapsed time depends on motion and gravity along a path. Special relativity describes motion. In a chosen reference frame, a moving clock ticks more slowly than clocks at rest in that frame. Travelers notice no dramatic change because daily speeds are tiny beside light speed. Particle experiments and precision clocks, however, measure the effect.
General relativity adds gravity. Near Earth, a stationary clock at a lower altitude runs more slowly than one at a higher altitude, after accounting for their motion. Precise clocks at modestly different heights can reveal a difference. The effect is not that gravity damages one clock; spacetime itself assigns different elapsed time to the paths. “Runs slowly” requires comparison. An observer moving with a clock finds that it ticks normally. Differences appear when paths or signals are compared in a defined frame. Claims about one “really” correct time hide this relation.
Satellite navigation must account for both effects. Orbiting clocks move rapidly but experience weaker gravity than surface clocks; the effects oppose. Engineers apply relativistic corrections so timing signals remain useful for position.
Relativity does not mean that time is arbitrary or that any sequence of events can be chosen. Its equations make precise predictions confirmed by evidence. The surprising lesson is that a universal shared rate was an assumption from limited experience. Clocks reveal time as something measured along a path through motion and gravity, with differences small in daily life but essential in precise systems.
The passage is hidden while you answer. It comes back with your result.
Questions
Choose an answer. The explanation appears after you answer.
-
Question 1 of 4
What is the main idea of the passage?
The answer is A: Relativity predicts that motion and gravity produce precise differences in elapsed time, confirmed by clocks and required in satellite navigation.
The passage explains both relativistic effects, comparison frames, evidence, GPS relevance, and limits.
-
Question 2 of 4
Why do satellite systems require corrections from both theories?
The answer is B: Orbital motion and weaker gravity change satellite clock rates differently from ground clocks.
The third paragraph says orbital motion and weaker gravity affect satellite clocks in opposing ways.
-
Question 3 of 4
What does “frame” mean in context?
The answer is C: a defined viewpoint and motion standard used to compare measurements
Rate comparisons require a chosen condition of rest or motion and defined signal relationship.
-
Question 4 of 4
Which practical system must account for relativistic clock effects?
The answer is D: satellite navigation
The third paragraph identifies satellite navigation as a system that applies relativistic corrections.
Score: none answered yet.