In plants, a tropism refers to the growth of a plant in response to an external stimulus. Plants can grow either towards or away from stimuli. The curving of plants is frequently due to differential growth, where different sides of a stem or root grow at different rates.n plants, a tropism refers to the growth of a plant in response to an external stimulus. Plants can grow either towards or away from stimuli. The curving of plants is frequently due to differential growth, where different sides of a stem or root grow at different rates.
There is an exact numerical answer to this question. By definition, 1 light year is exactly 9,460,730,472,580,800 meters. By definition, 1 mile is exactly 1,609.344 meters. So, 1 light year is exactly 5,878,625,373,183 and 849/1397 miles, by definition. Written May 20 â¢ View Upvotes.
up vote 5 down vote. We don't directly measure distances to anything light years away by timing light. Light year is just a unit of distance like a mile or kilometer. We know how fast light goes in 1 second, we know how many seconds in a year and so we know how many meters (or miles) are in a light year.