Big Bad Black Holes

What would it be like in a universe where time flows forward and backward? Does this imply time travel? Could we have a choice or
would we be suprised when we got up in the morning?

Jm

JM, Seems to me I've read someplace that time travel in very limited time period can be accomplished. c.i.

c.i.:
That is what I read about wormholes. Given one could travel back and forth through the wormhole one could not go further back in time then when the wormhole was created. So if I created a wormhole time tunnel on Feb 15, 2003 at 12PM I would not be able to use that specific wormhole
to time travel back to Feb 15, 2003 11:59AM.

JM

Hi JM,

Although wormholes do exist (theoretically) as exact solutions to the relativistic equations of Albert Einstein, their actual existence would contradict the laws of thermodynamics.

There's a possibility that they *only* exist in theory (due to inaccuracies in current models), and do not exist in reality.

Here's some general info:

http://casa.colorado.edu/~ajsh/schww.html

rosborne,

Thanks for the link. More info, great! I can learn something new.
I'm going to try to reply to your question about science education first. Just got an e-mail from Michael Schermer's Skeptic Mag site.
Apparently a bunch of scientists are concerned about the same question you asked and wrote a public letter about it in honor of S.J. Gould.

JM

P.S. My only source about wormholes, Kip S. Thorne's "Black Holes & Time Warps" also noted that
even if we could use these wormholes they would consume an enormous amount of energy to create and keep open (we are talking Black Holes being harnessed for this, and he implies this when he thinks about "highly advanced civilizations" using wormholes for time/space travel), so practicality is definitely limited

Time and energy;
Are not "time" and "electromagnetic energy" the same thing?

Time basically travels @ the speed of light; we experience time as a function of phenomina changing within our sensory terms of referrence.

Time doesn't "go" forward, and backward; time "is" forward, and backward;
All time exists.

Therefore to go backward temporally, one must exceed the speed of light, to progess to a different "timeframe".

Eh?

New theories (maybe not so new) on 'black hole' construction allows for some black holes to have weak vectors where a craft could possibly perhaps theoretically drop below the even hoizon and....... then what?
Another universe? A worm hole within our own?

The article talks about a manned mission which would take long enough for several generations to live and die on the ship and those who are alive would have to be willing to die on arrival. Why not an unmanned vehicle?

The weak vector

littlek,

The math and theory I have seen predict destruction even of the atoms of any matter that crosses the event horizon of a black hole.
Earlier theories describe black holes as those stars that have cut themselves off from communication from the rest of the universe because of the inability of any information (light or electromagnetic radiation or matter) to flow past this horizon.

Due to laws of conservation it is my personal belief that black holes consist of "real" matter and that there is no singularity or multiple singularities that are mystically of infinite density and small size at various locations within the hole's horizon. I am not sure how navigation through even these real matter singularities would be effected. By definition we would not know where these would lye within the hole until we crossed its horizon and, since our spacecraft would be traveling at a significant percentage of the speed of light, our vehicle would have to possess excellent maneuvering capabilities. However, the necessary quick turns would add killer "G" forces to those tidal forces already trying to make spaghetti out of us. OK, we survive all this. It is my unromantic opinion that we end up not in another universe or time but merely on the other side of the star traveling at the same speed we crossed the horizon initially in God Knows what direction.

Yet in further research about the subject I have experienced other theories expounding on how black holes can give off radiation to the point of evaporation. Not too long ago our universe seemed to follow Newtonian Laws with some caveats. Then Einstein's theory's held sway with some but fewer observed exceptions. Short answer, I guess, is we just don't really know. So scientists will continue to ask questions with the hope of answers always over the next "horizon".

Thanks for the link.

JM
P.S. not to be nick picky but its "sector", a vector is something different in math

be picky, that's fine, some bell was going off when I was typing vector.....

In the case of "Big Rip", what become of black holes, I wonder?

http://www.space.com/scienceastronomy/big_rip_030306.html

"The question Caldwell and his colleagues posed is, what would happen if the rate of acceleration increased?

"Their answer is that the eventual, phenomenal pace would overwhelm the normal, trusted effects of gravity right down to the local level. Even the nuclear forces that bind things in the subatomic world will cease to be effective.

" 'The expansion becomes so fast that it literally rips apart all bound objects,' Caldwell explained in a telephone interview. "It rips apart clusters of galaxies. It rips apart stars. It rips apart planets and solar systems. And it eventually rips apart all matter.


- "A billion years before the end, all galaxies will have receded so far and so fast from our own as to be erased from the sky, as in no longer visible.

- "When the Milky Way begins to fly apart, there are 60 million years left.

- "Planets in our solar system will start to wing away from the Sun three months before the end of time.

- "When Earth explodes, the end is momentarily near."



----- But here is a caution:
" 'I think it's a logical possibility,' Loeb told SPACE.com. But he cautioned that altering the cosmological constant goes against current consensus." -----

A space craft just inside the event horizon of a black hole with a trillion solar mass, would likely have little change in anything than just outside the event horizon. The singularity would be a light year? away and as Satt suggested most of the mass would not yet have been captured by the singularity. If the space ship maneuvered to avoid collisions with other objects inside the event horizon, it might be centuries ship time (and eons outside observer time) before the space craft was captured by the singularity.
Since the dimensions of the singularity are zero it would be easy to miss the singularity by at least a tiny amount. A sling shot maneuver would result (a gravity assist maneuver) sending the crumpled remains of the craft back almost to the event horizon in a highly elipitical orbit.
A ten solar mass (or less) black hole is much more vicious. Any space craft we can imagine would be shredded shortly before it entered the event horizon, and the humans would likely die from tide effects before the space craft failed. Perhaps inside the small black hole is another dimension, but I don't picture much change (other than no escape is possible) inside the extremely large black hole. Do you experts agree? Neil

Hi Neil, nice to see you here on A2K

You are essentially correct with regard to supermassive black holes having an event horizon which is further from the singularity, and therefor, in a gravitational field which is far less distorted than near the singularity.

Given a singularity of sufficient mass, crossing the event horizon would be an almost undetectable event. But of couse, once you were on the other side of it, there would be no going back, no matter how hard you tried.

Less massive singularities generate event horizons which are much closer to the singularity, and could easily be in the gravitationally distorted destructive zone around the singularity. I don't think this gravitational gradient is called a tidal force however (though I could be wrong about this). I think gravitational tidal forces usually have an angular component to them (between two bodies in orbit).

You have mentioned sling shot maneuvers in the past, but I don't think your example above is quite right.

Sling shot maneuvers refer to the use of orbital motion along with gravitation, to add relative velocity to an object (usually a satelite). This is not the same as simply falling toward a gravity source and entering an orbit, even an eliptical one.

Hope that helps.

Best Regards,

neil

I am not exactly an authority on black holes but from my readings you seem correct about the inverse relationship between its "viciousness" around the event horizon and its mass.
However, regarding your statement:



Implicitly answers the problem of finding the singularity of a large black hole. Given the ship has passed beyond the horizon and reached its conceptual point of no return, this slingshot action would continue until (like a ball bouncing on Earth) the "ship" would "settle" upon the "singularity".

Unlike the mathematical concept of the singularity, I have always had a problem with the fact in real life of the singularity sharing the same parameters of its mathematical counterpart. After all, if this point has no dimensions how is one to pursue a successful search for it? I will not completely rule out this possibility, but intuitively one feels that this "mathematical point" describes something perhaps a little more complicated in the real universe, at least this one anyway. Perhaps others here might expound on this so as to enlighten me.

JM

Hi JM,



I don't think the ship would "settle" on the singularity because it would be in orbit around the singulariry and will only "settle" subject to whatever conditions of orbital decay are in its vicinity (and there may be virtually none).



I'm not sure I understand your question but...

The singularity is the source of the distortion as described by mathematics. It is not an object in the normal sense of things. The location of the singularity can be deduced, and predicted, by the conditions of space around it, but the singularity itself can not be interacted with, or even referenced as a physical object.

Does that help?

Best Regards,

A good source of info on Black Holes:

http://scienceworld.wolfram.com/physics/topics/Astrophysics.html

Regards,

So The cubic lightyear of volume inside the event horizon of a trillion solar mass blackhole might contain very little inside the event horizon other than 999 black holes with a mass averageing one billion solar mass each. In this situation there would be little to decay the orbits other than the rare collision of event horizons, so the orbiting of most of the 999 might persist for billions of years without the trillion cubic miles (a volume about the size of Earth's moon) surounding the singularity containing even 10% of the mass inside the event horizon? I guess you can tell I am confused by generalities. Neil

Even if I don't understand it, they're still beautiful to behold.

on the chance of appearing argumentative, Wilso;
while 'beauty' is, perhaps, defined by our 'connection' to phenomina, a black hole (never having been photographed) is one celectial object that hides its potential beauty behind the 'laws of physics; you cannot see it, it is total blackness.
To thoeretically 'see' a black hole, one would have to transpose the eminating electromagnetic radiation into some visible metaphore, thus 'seeing' a kind of 'ghost' coloured hole.

I'm sorry folks, but this "naive realist" has dutifully read all the links presented on this thread for our edification.

Lets face it, A black hole is merely a location in space and time where the total accelerations of gravity exceed 300,000 kilometers per second to the viewer.

IF there is, and there probably is, surrounded by the Milky Way, an area of sufficient mass to accelerate spacetime to greater than the speed of light at that location then we have a black hole.

Eventually, as one looks further and further away from our location, the energies and wave lengths of light will get dimmer and dimmer and longer and longer until they are no longer capable of transporting any information. Consequently we reside in another type of "black hole" . This type is due merely to the nature of light in a gravity (space time) field, the other merely due to the actions of gravity upon light in a gravity (space time) field. The average density of the field makes all the difference.

It doesn't take a rocket scientist (Ican will do just fine ) to know that if you can fly an airplane at 650 miles per hour and you have a head wind of 700 miles per hour you ain't gonna get there. You may get some place else twice as quick though, if you do it right. Same principle applies when swimming or canoeing in a river.

If light (electromagnetic radiation) propagates at 300,000 KMH and the total accelerations of gravity at that point are over (c) the speed of light you ain't gonna see anything from outside, ie a black hole.

We are limited in our observations by the speed of light, and there is no good reason to assume that outside our purview things are any different.
There is also no good reason to assume that outside our purview things are the same, but a fair THEORY could assume that, and go on from there.

If we are going to assume the existence of other than four dimensions, and assume that time (not space time) is a function of the speed of light then we may as well go whole hog and assume that something-somewhere thought "Let There Be Light" and go on from there.
The results of that theory have, IMO natch, left something to be desired.

Happy thoughts everyone. Keep in mind that Knowing, Thinking, and Believing may be very different things.