# Climbing out of a Black Hole?

1. Feb 9, 2008

### keithh

By way of explanation, I am on a learning curve as far as relativity is concerned, but then this might be true for everybody. Some of my questions might appear off the wall, but I am not interested in learning about this subject by rote, hence the questions. This thread is an extension of questions that began in another thread entitled the Schwarzschild Metric.

By way of an introduction, a black hole is said to form if you get a certain amount of mass [M] inside the Schwarzschild radius [Rs] given by the equation:

$$Rs \ = \ 2GM/c^2 \ = \ c^2/2g$$

From which we can also determine the gravity [g] at [Rs] by:

$$g \ = \ GM/Rs^2$$

However, to form a black hole requires enough concentrated mass so that its gravity can overcome all the other atomic forces of matter. The physics of stars suggests this mass must be of the order of 2-3 solar masses to form the smallest (natural) black holes. To-date, the largest black hole prediction that I have seen is associated with the M87 galaxy in the Virgo constellation, which has been estimated to contain ~3 billion solar masses. The following table provides a frame of reference of the mass, Schwarzschild radius and gravity [g] at the event horizon of various sized black holes:

$$M=3.83, \ Rs=1*10^4, \ g= 4.47*10^{12}$$
$$M=3*10^9,\ Rs=1*10^{12},\ g= 4.47*10^3$$
$$M=1.5*10^12, \ Rs=1*10^5, \ g= 9.82$$

The first line corresponds to a small black hole formed by the collapse of a single star. The second line corresponds to a galactic black hole, e.g. M87, having consumed about 3 billion stars. The last line relates to a conceptual black hole that would approximate Earth’s gravity at its event horizon. This black hole would have to contain 1.5 million billion suns and have a Schwarzschild radius of a ½ light-year.

The implication of Newtonian physics suggests that somebody outside this super massive black hole could lower a rope and climb down through the event horizon as the ‘force’ of gravity is comparable to that on Earth.

So what prevents that somebody from climbing back up the rope?
If time slows to stop at the event horizon, do they ever reach the horizon?

General relativity suggests that time slows as you approach any mass [M] and would appear to stop, both for the distant observer and the onboard observer at the event horizon – see thread on Schwarzschild Metric. However, general relativity also implies this is not an effect of the force of gravity but rather the curvature of spacetime due to the presence of mass. In the case of a black hole, this mass has now disappeared behind the event horizon, apparently collapsing to a singularity of infinite density or something reduced to the quantum Planck scale.

Could this suggest that the underlying structure of matter is a waveform?

A photon is said to be a wave that has the attribute of kinetic mass. An electron is said to be a particle that has both Compton & deBroglie wavelengths. By way of analogy:

What happens to wave energy in an inference pattern?

Would welcome any free-thinking ideas grounded in good physics.
Thanks

Last edited: Feb 9, 2008
2. Feb 9, 2008

### pervect

Staff Emeritus
No.

If you freely fall through a black hole, you will experience only finite tidal forces. However, it is not possible to lower anything through the event horizon of a black hole on a rope. The amount of acceleration required to "hold station" becomes infinite near the event horizon.

Note that as a consquence of this argument, there are infinite tidal forces for someone attempting to hold station near the event horizon of a black hole, even though the tidal forces for someone freely falling through the event horizon are finite.

A somewhat idealized and highly technical analysis of the physics of lowering objects through event horizons can be found at

http://gregegan.customer.netspace.net.au/SCIENCE/Rindler/RindlerHorizon.html#UNREELING

The specific even horizon here is the so-called "Rindler horizon". It is very similar to the event horizon of a very large black hole, but it simpler to deal with mathematically.

3. Feb 10, 2008

### keithh

The question about Climbing out of a Black Hole? was meant to be rhetorical, so I was not really looking for a confirmation of the answer – No. In part, this was why I made reference to an earlier discussion on the implications of the Schwarzschild Metric.

Clearly, your footnote about pervects is intended to ridicule anybody who apparently transgresses the rule about overly speculative posts. However, your link to the discussion of the Rindler Horizon, which was helpful, suggests this was considered an acceptable issue to discuss within the Usenet group sci.physics.research. While I have only quickly read the paper, if this outcome was obvious to you, then I must bow to your genius.

However, I accept that my question about the underlying structure of matter was a speculative enquiry and maybe I should simply accept that matter collapses to a singularity within a black hole without question.

So while I understand the need for the rules of forum, I cannot help feel that there is an undertone that implies people need to first fully understand the standard texts before raising such questions in this forum. If so, I am saddened, as I felt that one of the goals of the forum was to assist people along their own personal learning curve. In part, one of the reasons for joining the physics forum was to get answers, "grounded in good physics", to counter much of the speculative information I was reading about general relativity via the WEB.

4. Feb 10, 2008

### Staff: Mentor

Pervect's response in the other thread is a good one. Basically, there is a right and a wrong way to learn. We recently closed a couple of threads about a perpetual motion crackpot who'se "personal learning curve" has led him to spend 20 years investigating a dead end. He's lost his job and his family. If he had instead followed the standard learning curve, he could have gotten himself an engineering or physics degree and learned the real reasons why his device doesn't work, rather than wasting time and energy on misdirected idle speculation. It's tragic.

5. Feb 10, 2008

### pervect

Staff Emeritus
Wrong. I chose this handle a long, long time ago. While it seems like a bit of a silly choice now, I'm sticking with it. I put in some explanatory notes as to where it came from, a novel by Asprin in my .signature to give people some idea of where it came from.

I don't ridicule people who transgress the rule about overly speculative posts, I just take appropriate administrative actions (such as locking the threads, giving infraction points, and other measures) to enforce our PF guidielines.

People with "overly speculative" ideas have a right to their opinions, no matter how misguided I think they are. But that place is not here at Physics Forums. We have rules here, and they will be enforced, by me, and by the rest of the staff.

I'm taking one of those administrative actions here, now, and locking this thread.