Help Please, Black Holes

Hello Everyone,

First of all I am new here but I am need of some help and I hope you all can help me.

I have been given this question to answer for my class and I am stuck. Please help if you can.

"Assume you have a very accurate device to measure the mass of a black hole. Now you send a space probe into a black hole - as you will recall that time for the probe will slow as it approaches the event horizon so that we as observers will actually never "see" it cross the event horizon - the lights on the probe will get dimmer and dimmer (and redder and redder) but will not go out. If this is so will your accurate mass measuring instrument detect an increase in the mass of the black hole. If yes why?, If no then the black hole will never increase in mass why?"

After turning in my answer to this question I was basically told I was did not answer the question in the right way and was given this explantion to find an answer.

"Maybe I did not explain my question well however the aim of the question was not how or if the mass of a block hole can be measured. I wanted to know if you understood what happens when and IF something crosses the event horizon. Lets put it another way - assume something does fall into a black hole then as you state in your answer the mass of the black hole will increase - the effect of this increase in mass will be felt by the space in the vicinity of the black hole as increased gravity. This means that the rest of space will GAIN some information about the black hole - however another argument is that NOTHING escapes from a black hole not even information about its mass. So we have a problem by revealing information about itself through its effect (gravity) on the surrounding space the black hole is actually LOSING something - ie something is escaping from the black hole - but nothing can escape from a black hole - right? Your task is actually to reconcile these two very "opposing" arguments with your understanding of the subject of relativity and cosmology"

Now I thought I was asked to measure a Black Hole if I could. Well I did answer that but I am now lost at this point and was hoping you could help me.

Any info or help would be great. Thanks in advance for your help.

Becky

Hi Becky,

I think the answer your teacher is interested in is this.

The addition of some mass to the black hole does change the curvature of space in the area outside of the black hole, thus affecting the apparent gravitational force in that area. However, no NEW information about the black hole itself is generated by this process. There is no information that actually crosses the event horizen from within the black hole itself.

The only new "apparent nformation" is the actual amount of new mass that has entered the black hole from outside. This apparant information is contained in the apparent increase in gravitational force due to the increased spacial curvature caused by the additional mass.

Hope this helps.

z

Z

Thanks somuch that helps out alot. Atleast now I understand more of what he is looking for and can form an essay answer of 1000 words much better.

If anyone has any other thoughts and idea's I would love to hear them. The more I get the better I will be able to finish this as this is my last question before I have one last final project then I am done.

Thanks Again for your help

Becky

Becky,

I thought of another way to look at this problem.

As the probe approaches the event horizon, the signals received by the observer far away are red shifted. Also, the probe appears to be slowing down and never reaching the event horizen due to gravitational time dilation of the emitted signal (gravitational red shift). So it appears to the observer that the probe never crosses the event horizon.

However, this is just an appearance due to the fact that the signals from the probe are being emitted from within an intense gravitational well. The probe itself does cross the event horizon and add its mass to the black hole. If this were not true, large black holes could not form within the lifetime of the universe, since no additional mass would be able to cross the event horizon (from the point of view of the far away observer) once the initial black hole had formed.

The signals from the probe are essentially frozen in time (from the point of view of the far away observer), as the probe crosses the event horizon. Thus, the only information that can be obtained once the probe has crossed the event horizon is a change in the gravitational field of the black hole, due to the increased spacial curvature from the additional mass.

z

Hi Z

Is there any way I could email you and discuss this that way. I think it would be easier.

Now to your answer

I understand that nothing can get out of a black hole, and that the probe could not be seen entering the event horizon, but one of the things I am stuck on is the effects of the event horizon other then nothing gets past it. why does the light get redder and not go out. Is this because thats how our eyes would precieve it, or is it because the space time contortion or the Space time continuum.

Becky

Hi Becky,

Sorry, I refuse to post my email address on the web. Too much spam can come from it among other things.


As an electomagnetic signal emitting body approaches the event horizon of a black hole, the signal perceived by the far away observer is red-shifted. This can be explained in various ways. According to general relativity, it is because of the warping of the space/time continuum due to the presence of the large mass of the black hole.

Another explanation is that in order to overcome the gravitational attaction of the black hole, the signal loses energy to the gravitational field and thus becomes red-shifted.

At the point of the event horizon of the black hole, any signal emitted has an infinite red shift (from the point of view of the far away observer). Space/time is curved to such an extent that the signal can not reach the observer. Or, in other words, all of its energy is used up in overcoming the gravitational field of the black hole.

No signal can cross the event horizon from the inside to the outside.

z

Z

Can you PM me with it. That way no one will see it but me.

Becky,

I am onot a registered user, so I can't use that feature.

z

Hi Z,

I thought you could still use that feature.

This class I am taking is for a Diploma in Astronomy through the Astronomy Foundation. These questions have been tough but I have learned alot from them. I am hoping to be done soon. I do apperate your help what you said made alot of sense. I do want to thank you for your help.


Becky

Hi,

Being a kid, I was ceasing birds, but never catch any.
One day my Grandma' told me that the solution is, to pour salt on the bird tail, then she will aloud me to catch her.

Followed by days of thinking.

Regards

Becky if light gets dimmer the closer its emission is
to a black hole this means that Einstein's theory
predicts Energyless photons or energyless light
with an infinite wave size.

Sorry to tell you but this means black holes don't
really exist. Although there is still an extreme of
gravity that we are observing.

The technical term for gravitational redshift of light
is named after Einstein: the Einstein shift.
His GTR predicts infinite redshift to light at the event
horizon of every black hole.

This energyless light prediction is also the theory
predicting its own downfall(I got that from Hawking!)
Black holes are the very failure of GR that must be
dealt with.

Hope this is interesting!!! It should be.

Hi stargazer, Nick and others,

It might just be that what the teacher was looking for was that the information of all things associated with a black hole is stored on its surface as you already seem to know... that two dimensional object that is an event horizon. Even though you can't see it and it makes no sense the information is there on the surface. It cannot "go away". As for information leaking from a black hole.... it does. Stephen Hawking has showed that recently and the Black Hole will eventually "evaporate" that includes all the information.

It really depends on just how much information this teacher wants to know.
Try these references...
New Scientist - 22 January 2005
Black Holes and Quark confinement - Ed Witten
String Theory has given tremendous "insight" into the process and has convinced many... but there are competing theories too.

What we see is "probably" a black hole is a D-Brane where the information of the interior is encoded on the surface of the Black Hole as a "Hologram" in 2D form. The information inside a black hole then becomes "equal" to the surface area of the event horizon. String Theory has "proven" this is a mathematically consistent point. A great triumph for String Theory (It discovered something not previously known... he he he! ... that's "good"). This may seem impossible but think of how a conventional 2D Holograms store 3D information on a surface. The surface is "written" by the excitations of a string that develops and fills the surface area of the black hole. As the black hole "evaporates" the surface area of the black hole "shrinks", and in the same way as real holograms we can make with lasers, the information gets less and less as the size of the hologram is reduced until it vanishes away entirely....
Ed Witten's Home Page
Geometric Langlands Program
Hunting of the Snark - Lewis Carroll

Cheers

Hi Nick,

If energy becomes energyless, its infinite wavelength would exceed the boundries of a finite universe, so the wave could not fully develop. And with frequency equal to zero, the wavelength would occur less often than the universe itself, even if the universe only happened once. Maybe the size of the universe sets the practical limit of the Red Shift from black holes. If they are constrained to infinite wavelength then the black hole makes itself extinct. It would need to change phase into something else.

In the last 20 years I’ve read many theories about what exactly is / what happens in our SUN, and seams that the arguments continues. Worse is happening about the Earth nucleus, the arguments continue.
The Atom…no comments!
Then reading very confident theories about Black Holes, I have been wandering. …

The weak parts of the chain are Philosophy and Logic.

As much as The Black Holes are theoretical objects, any interaction with it will depends of the definition and initial condition we thought about it.

As much we do not know what is an Atom, in the name of the God, how can somebody can figure out what is a “Black Hole”

This shows our incapacity of thinking one real step forward, Yes it is much easier to talk, and create theories about things that can not be checked out.

Regards,

I asked and still no answer that I can come back to class with and sound like at least I understand just a little.

Please help me with some book I can read.

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