Can a Running Tap Water Basin Be an Analogy for a Black Hole Event Horizon?

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Discussion Overview

The discussion revolves around the analogy of a running tap water basin as a representation of a black hole event horizon. Participants explore the validity of this analogy, focusing on the behavior of water and light in relation to the concepts of event horizons in black holes.

Discussion Character

  • Exploratory
  • Debate/contested

Main Points Raised

  • One participant proposes that the event horizon of a black hole can be likened to water flowing in a basin, suggesting that light hovers around the event horizon similar to water not flowing into or out of the basin.
  • Another participant challenges this analogy, stating that water can indeed flow down the basin and questioning the spherical form described.
  • A different participant clarifies that light can enter a black hole, and only light emitted radially outward at the horizon is trapped, while other light crosses the horizon and reaches the singularity.
  • Another participant introduces the concept of an acoustic black hole as a different analogy that has garnered scientific interest.
  • The original poster seeks to understand the visual representation of an event horizon, comparing it to the water forming a border in the basin.
  • A later reply provides a definitive rejection of the analogy, stating simply that it does not hold.

Areas of Agreement / Disagreement

Participants express disagreement regarding the validity of the water basin analogy for a black hole event horizon, with multiple competing views on the nature of light and water in this context. The discussion remains unresolved.

Contextual Notes

Participants have differing interpretations of the behavior of water and light in relation to the proposed analogy, indicating a lack of consensus on the definitions and representations involved.

shounakbhatta
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Hello,

I am trying to draw an analogy, which just came with a flash in my mind. Please clarify me, if it is wrong. Kindly note that it is an analogy only.

An event horizon -- Where the light emitting is not strong enough to go inside the black hole also it cannot go outside the zone and keeps on hovering around.

If I open a tap water and the water gushing down the basin creates a spherical form. The water neither can flow inside the basin, nor it can go outside.

Is it this which can be thought of a black hole event horizon?

Please correct me if I am wrong.

Thanks.
 
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shounakbhatta said:
If I open a tap water and the water gushing down the basin creates a spherical form. The water neither can flow inside the basin, nor it can go outside.
I don't follow you there at all. Of course the water can flow down. Why would it not?

Also, it would not be a spherical form, it would be a circular form.
[/QUOTE]
 
Also, light readily enters a black hole. The only light that is trapped is light emitted at the horizon in the radial outgoing direction. All other light emitted at or in the horizon reaches the singularity (in the simplest BH). Further, all light heading toward the BH, crosses the horizon and reaches the singularity.
 
There is another analogy that has drawn significant scientific interest. It is called an acoustic black hole. IIRC one was created not long ago using an Bose-Einstein condensate.
 
My question was trying to understand how an event horizon looks like? My analogy of water flowing down is that the light which hovers around the 'event horizon' of a black hole, can that look like the water which forms a border on the basin?
 
The short answer is ... No.
 

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