<p>It was never thought to be the case.  A fuller quote:</p>
<blockquote>
<p>So, by this analogy a black hole is a kind of bottomless pit.</p>
<p>What would happen if you fell in? Assuming you could survive the gravitational tides and the intense radiation flux, it is just barely possible that by plunging into a black hole you might emerge in another part of space-time.</p>
<p>Somewhere else in space some-when else in time.</p>
<p>In this view, space is filled with a network of wormholes something like the wormholes in an apple. Although by no means is this point demonstrated it is merely an exciting suggestion.</p>
</blockquote>
<p>Notice the expressions &quot;just barely possible&quot; and &quot;by no means is this point demonstrated&quot;.  This was a bit of speculation (by Sagan and probably with Kip Thorne) based off the observation that Einstein-Rosen bridges are solutions to the gravitational equations, and one end of a wormhole would look much like a black hole. But Sagan knew that there was (and is) no known process that could actually form a wormhole.</p>
<p>In 2023 our understanding of wormholes has developed.  A stable wormhole that allows for travel seems to require exotic matter, such as negative mass.  This seems to rule them out as an astrophysical objects.  Quantum theory may provide a possible way form them to exist.  However, while we have observed black holes, we haven't observed white holes (that should form the &quot;other&quot; end of the worm hole).  Again this points to them being a theoretical, not physical real solutions.</p>

CC BY-SA 4.0
2023-01-23T15:10:30.173Z
With negative mass, would it cause peaks in spacetime, so that everything drifts away from white holes?
Thomas Weller
CC BY-SA 4.0
2023-01-23T17:30:27.273Z
Yes, a "white hole" is a region of spacetime which nothing can enter, analogous to a black hole, which is a region of spacetime which nothing can leave. Negative mass would be very very weird - for example if you apply a force to it, it would move in the opposite direction. Gravitationaly it would move towards positive mass, but positive mass would move away from it.
James K
CC BY-SA 4.0
2023-01-27T21:44:10.530Z
"our understanding of wormholes has developed. A stable wormhole [...] seems to require exotic matter" - I'm pretty sure Sagan wasn't talking about a bidirectional traversable wormhole, but about something like a Kerr manifold, which doesn't need exotic matter. It's still implausible because of the infinite blueshift at the inner horizon, which I think was known in 1980 and could be the "intense radiation flux" he mentioned. Also, I'm not sure we have direct evidence against white holes given how similar they are to black holes on the outside.
benrg
CC BY-SA 4.0
2023-01-27T21:44:48.587Z
@ThomasWeller Negative mass doesn't cause peaks in spacetime: see [this answer](/a/47406).
benrg
CC BY-SA 4.0
2023-01-22T07:52:16.997Z
2023-01-22T15:16:09.467Z
2023-01-22T15:16:09.467Z
James K
<p>The September 2009 YouTube music video <a href="https://youtu.be/zSgiXGELjbc" rel="noreferrer">Carl Sagan - 'A Glorious Dawn' ft Stephen Hawking (Symphony of Science)</a> at about <code>00:30</code> depicts a clip from (what I think is) Carl Sagan's 13-part PBS television show <a href="https://en.wikipedia.org/wiki/Cosmos:_A_Personal_Voyage" rel="noreferrer">Cosmos: A Personal Voyage</a> where he says (removed from context):</p>
<blockquote>
<p>Space is filled, with a network of wormholes... you might emerge somewhere else in space, or <em>somewhenelse</em> in time.</p>
</blockquote>
<p><strong>Question:</strong> In 2023, is space still thought to be &quot;filled with a network of wormholes&quot;?</p>

CC BY-SA 4.0
2023-01-23T16:03:53.340Z
I can't help reading this title as "...filled with a network of wombles". Huge if true.
psmears
CC BY-SA 4.0
2023-01-23T22:49:05.900Z
What are your own thoughts? Where is your research?
Robbie Goodwin
<cosmology><wormhole>
In 2023, is space still thought to be "filled with a network of wormholes"?
uhoh
# In 2023, is space still thought to be "filled with a network of wormholes"?

(Asked by: username_0 on 2023-01-22)

The September 2009 YouTube music video [Carl Sagan - 'A Glorious Dawn' ft Stephen Hawking (Symphony of Science)](https://youtu.be/zSgiXGELjbc) at about `00:30` depicts a clip from (what I think is) Carl Sagan's 13-part PBS television show [Cosmos: A Personal Voyage](https://en.wikipedia.org/wiki/Cosmos:_A_Personal_Voyage) where he says (removed from context):

> Space is filled, with a network of wormholes... you might emerge somewhere else in space, or *somewhenelse* in time.

**Question:** In 2023, is space still thought to be "filled with a network of wormholes"?

**Tags:** cosmology, wormhole
> **Comments:**
> **username_1**: I can't help reading this title as "...filled with a network of wombles". Huge if true.  
> **username_2**: What are your own thoughts? Where is your research?  

---

## 1 answers

### Answer by username_3 on 2023-01-22. Score: 18 | Accepted answer

It was never thought to be the case. A fuller quote:

> So, by this analogy a black hole is a kind of bottomless pit.
>
> What would happen if you fell in? Assuming you could survive the gravitational tides and the intense radiation flux, it is just barely possible that by plunging into a black hole you might emerge in another part of space-time.
>
> Somewhere else in space some-when else in time.
>
> In this view, space is filled with a network of wormholes something like the wormholes in an apple. Although by no means is this point demonstrated it is merely an exciting suggestion.

Notice the expressions "just barely possible" and "by no means is this point demonstrated". This was a bit of speculation (by Sagan and probably with Kip Thorne) based off the observation that Einstein-Rosen bridges are solutions to the gravitational equations, and one end of a wormhole would look much like a black hole. But Sagan knew that there was (and is) no known process that could actually form a wormhole.

In 2023 our understanding of wormholes has developed. A stable wormhole that allows for travel seems to require exotic matter, such as negative mass. This seems to rule them out as an astrophysical objects. Quantum theory may provide a possible way form them to exist. However, while we have observed black holes, we haven't observed white holes (that should form the "other" end of the worm hole). Again this points to them being a theoretical, not physical real solutions.

> **Comments:**
> **username_4**: With negative mass, would it cause peaks in spacetime, so that everything drifts away from white holes?  
> **username_3**: Yes, a "white hole" is a region of spacetime which nothing can enter, analogous to a black hole, which is a region of spacetime which nothing can leave. Negative mass would be very very weird - for example if you apply a force to it, it would move in the opposite direction. Gravitationaly it would move towards positive mass, but positive mass would move away from it.  
> **username_5**: "our understanding of wormholes has developed. A stable wormhole [...] seems to require exotic matter" - I'm pretty sure Sagan wasn't talking about a bidirectional traversable wormhole, but about something like a Kerr manifold, which doesn't need exotic matter. It's still implausible because of the infinite blueshift at the inner horizon, which I think was known in 1980 and could be the "intense radiation flux" he mentioned. Also, I'm not sure we have direct evidence against white holes given how similar they are to black holes on the outside.  
> **username_5**: @ThomasWeller Negative mass doesn't cause peaks in spacetime: see [this answer](/a/47406).  

---

