diff --git a/macrovision.js b/macrovision.js
index dc52dcd6..d0d1f5c2 100644
--- a/macrovision.js
+++ b/macrovision.js
@@ -65,6 +65,15 @@ math.createUnit("earths", {
     definition: "12756km",
     prefixes: "long"
 });
+math.createUnit("lightsecond", {
+    definition: "299792458 meters",
+    prefixes: "long"
+});
+math.createUnit("lightseconds", {
+    definition: "299792458 meters",
+    prefixes: "long"
+});
+
 math.createUnit("parsec", {
     definition: "3.086e16 meters",
     prefixes: "long"
@@ -234,6 +243,7 @@ const unitChoices = {
             "humans",
             "stories",
             "earths",
+            "lightseconds",
             "solarradii",
             "AUs",
             "lightyears",