# Black Holes and Frequency Distortion

**URL:** <https://boards.straightdope.com/t/black-holes-and-frequency-distortion/287020>\
**Category:** Factual Questions\
**Created:** [January 28, 2005, 12:35am UTC](https://boards.straightdope.com/t/black-holes-and-frequency-distortion/287020 "2005-01-28T00:35:20Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![ricksummon](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ricksummon/32/3333_2.png) [@ricksummon](https://boards.straightdope.com/u/ricksummon)\
**Post date:** [January 28, 2005, 12:35am UTC](https://boards.straightdope.com/t/black-holes-and-frequency-distortion/287020/1 "2005-01-28T00:35:20Z")

</div>

A person who falls into a black hole and passes the event horizon cannot send any messages out of the hole; however, nothing stops someone from sending messages _in_ that the falling person can receive. My question is: How do you calculate the redshift or blueshift of an electromagnetic wave as received by the falling person? (Assume a Schwarzchild black hole with the wave and person traveling along a straight radial path.)