Do Black Holes Evaporate Despite Cosmic Microwave Background Radiation?

  • Context: Graduate 
  • Thread starter Thread starter Lapidus
  • Start date Start date
  • Tags Tags
    Black hole Hole
Click For Summary

Discussion Overview

The discussion revolves around the formation and evaporation of black holes, particularly in the context of the cosmic microwave background radiation. Participants explore concepts related to black hole formation, the nature of event horizons, and the implications of Hawking radiation.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • One participant questions how black holes can form if an outside observer never sees matter crossing the event horizon, suggesting a need for clarification on the formation process.
  • Another participant argues that while an outside observer may not see matter crossing the event horizon, a free-falling observer would experience this crossing normally, indicating different perspectives on the phenomenon.
  • Concerns are raised about whether larger black holes evaporate, with one participant suggesting that they do not evaporate currently because the cosmic microwave background radiation is hotter than them.
  • It is proposed that Hawking radiation is believed to be emitted by black holes, but its effects may not be observable at present.
  • A later reply asserts that larger black holes will radiate in the future when the universe cools sufficiently, implying a temporal aspect to black hole evaporation.

Areas of Agreement / Disagreement

Participants express differing views on the visibility of matter crossing the event horizon and the implications for black hole evaporation. There is no consensus on the relationship between black hole size and evaporation in the context of cosmic microwave background radiation.

Contextual Notes

Participants reference various assumptions about observer perspectives and the conditions under which black holes might evaporate, but these assumptions remain unresolved within the discussion.

Lapidus
Messages
344
Reaction score
12
An outside observer never sees stuff heading towards a black hole crossing the event horizon. How then do black holes form? If I would have watched region in spacetime where today exists a black hole for the last two billion years, how did the black come into existence?

Is it true that bigger black holes do not evaporate, since the cosmic microwave radiation is hotter than them? Why then then all the fuss about the information loss problem?

thank you
 
Physics news on Phys.org
Just because I never see it does not mean it never happens. I see the collapsing matter getting closer and closer to its Schwarzschild radius, redshifting itself into oblivion. Eventually there is mass m within a radius r=2m (almost), and for me there is no practical difference. Stars will orbit it like crazy, light will suffer an infinite amount of redshift trying to escape, and I myself had better not get too close!
 
An outside observer never sees stuff heading towards a black hole crossing the event horizon. How then do black holes form?

That's the view of a stationary distant observer...but a free falling observer does see stuff crossing the hypothetical event horizon in a "normal" everyday manner, no time delay for example, and the free falling observer also passes the event horizon without incident.
 
Last edited:
Lapidus said:
An outside observer never sees stuff heading towards a black hole crossing the event horizon. How then do black holes form? If I would have watched region in spacetime where today exists a black hole for the last two billion years, how did the black come into existence?

Is it true that bigger black holes do not evaporate, since the cosmic microwave radiation is hotter than them? Why then then all the fuss about the information loss problem?

thank you

Black holes are believed to radiate Hawking radiation.

The black hole came into existence because a star collapsed under its own gravity after the pressure from the nuclear reactions inside the star subsided.
 
Is it true that bigger black holes do not evaporate, since the cosmic microwave radiation is hotter than them?

yes. They will radiate in the future when the universe cools enough. Hawking radiation is not observable now.
 

Similar threads

  • · Replies 40 ·
2
Replies
40
Views
4K
  • · Replies 73 ·
3
Replies
73
Views
4K
  • · Replies 51 ·
2
Replies
51
Views
6K
  • · Replies 1 ·
Replies
1
Views
1K
  • · Replies 43 ·
2
Replies
43
Views
4K
  • · Replies 17 ·
Replies
17
Views
4K
  • · Replies 10 ·
Replies
10
Views
2K
  • · Replies 67 ·
3
Replies
67
Views
6K
  • · Replies 35 ·
2
Replies
35
Views
4K
  • · Replies 8 ·
Replies
8
Views
3K