# Distance of event horizon from surface of black hole. **URL:** \ **Category:** Factual Questions\ **Created:** [August 2, 2017, 4:07am UTC](https://boards.straightdope.com/t/distance-of-event-horizon-from-surface-of-black-hole/792606 "2017-08-02T04:07:08Z")\ **Posts on this page:** 2\ **Page:** 2
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [August 3, 2017, 6:45pm UTC](https://boards.straightdope.com/t/distance-of-event-horizon-from-surface-of-black-hole/792606/21 "2017-08-03T18:45:33Z")
> [@DPRK](#): > > …they both observe a redshift. Wouldn’t the person near the event horizon see a blue shift as particles are accelerated into the gravity well? ---
**Author:** ![k9bfriender](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/k9bfriender/32/3283_2.png) [@k9bfriender](https://boards.straightdope.com/u/k9bfriender)\ **Post date:** [August 3, 2017, 7:19pm UTC](https://boards.straightdope.com/t/distance-of-event-horizon-from-surface-of-black-hole/792606/22 "2017-08-03T19:19:03Z")
> [@Whack-a-Mole](#): > > Wouldn’t the person near the event horizon see a blue shift as particles are accelerated into the gravity well? Not if you are in freefall. You would be accelerating away from them faster than they are catching up. They would get red shifted. If you were hovering right over the event horizon (and don’t mind an arbitrarily large number o G’s, along with a magical engine that can put out an arbitrary number of G’s for no fuel), you would notice that light coming in is blue shifted, but it would be blue shifted by the same amount as if you were in free space and accelerating at the same number of G’s that it takes to hover over the event horizon. [Previous page](https://boards.straightdope.com/t/distance-of-event-horizon-from-surface-of-black-hole/792606.md?page=1)