Light Year
A light year is a unit of distance used in astronomy to measure how far light travels in one year. Light moves extremely fast—about 299,792 kilometers per second—so in one year, it travels roughly 9.46 trillion kilometers (or about 5.88 trillion miles). Light years help scientists express the huge distances between stars and galaxies. For example, the nearest star to Earth, Proxima Centauri, is about 4.24 light years away. The term “light year” can be confusing because it sounds like a measure of time, but it actually measures distance.
Planck Length
The Planck length is the smallest meaningful unit of length in physics, representing a fundamental scale at which classical ideas about gravity and space-time break down and quantum effects dominate.
It is defined as approximately 1.616 × 10⁻³⁵ meters.
The Planck length is derived from fundamental constants: the speed of light, Planck’s constant, and the gravitational constant.
It sets a theoretical limit below which the very concepts of space and distance may lose conventional meaning.
Used mainly in theories of quantum gravity and string theory.
Key facts:
1 Planck length ≈ 1.616 × 10⁻³⁵ m
Smallest scale in quantum physics and cosmology
Represents a scale where quantum effects of gravity become significant
The Planck length is crucial for understanding the fabric of the universe at its most fundamental level.
No conversions available for length.