# Is it possible that black holes do not exist?

#### Passionflower

My first thought was that the very postulate of Rinder horizons is an affront against Einstein's "constancy of the speed of light", as a light source beyond the horizon would not be seen.
This comes up almost as often as the twin "paradox".

The speed of light is c when an observer makes a local measurement! If an observer makes a distance measurement or an average speed measurement between two locations the speed of light is not necessarily c. It is not c and anisotropic in case the observer undergoes proper or inertial acceleration.

We all agree that there are sufficient practical barriers to a Rindler horizon, correct (infinite fuel source, CMB annihilation, etc)?
I do not agree.
Even for travelers on a bullet train slowly accelerating from 0 to a top speed of 200 miles/hour in a timespan of one hour there is a Rindler horizon. Only after the acceleration stops the horizon will disappear.

Did you read question and answer nine of Ted Bunn's article?

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#### rjbeery

Yes, I realized this, thanks; there is acceleration involved, by definition. I was just going through my initial thought process aloud. It also did not occur to me that a Rindler horizon could exist for an arbitrary acceleration speed and time but that makes sense - if a receding light source was "just" observable, then even a slight acceleration could redshift it beyond detection. As I said, please let me think about it more before I comment on the subject further. I will also read Bunn's article, thanks.

If you get a chance, please comment on post 22, because I do not believe an event horizon expands before mass comes "in contact" with it. Maybe we need to strictly define phrases like this, but I am open to that.

#### George Jones

Staff Emeritus
Gold Member
If you get a chance, please comment on post 22, because I do not believe an event horizon expands before mass comes "in contact" with it.
Vaidya metric.

See the left diagram of Figure 5.7 on page 134 (pdf page 150) of

http://www.physics.uoguelph.ca/poisson/research/agr.pdf,

and the first full paragraph beneath this diagram for the reason that this happens.

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