diff --git a/2021-07-21.md b/2021-07-21.md
index 7ead9f3ee..2904d5aae 100644
--- a/2021-07-21.md
+++ b/2021-07-21.md
@@ -1,2 +1,3 @@
 - [[richard feynman]]
-- [[michelson interferometer]]
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+- [[michelson interferometer]]
+- [[aether]]
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diff --git a/michelson interferometer.md b/michelson interferometer.md
index e69de29bb..e59f825b9 100644
--- a/michelson interferometer.md	
+++ b/michelson interferometer.md	
@@ -0,0 +1,3 @@
+- a [[tool]]
+	- [[go]] https://en.wikipedia.org/wiki/Michelson_interferometer
+	- [[reighleyc]] https://twitter.com/reighleyc/status/1417920314814521344
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