# Thread: light emerging from the Sun (or a black hole)

1. Hi,

I hope you can help me solve this problem:

I read that light emerging from a black hole (or from the Sun) is (partially) cancelled by gravity.
How can that be possible since gravity cannot travel faster than the speed of light?

How can the force of gravity produced by the Sun, whatever its nature, can pursue, reach and weaken (or cancel ou) a photon travelling at C?

thank you !

2.

3. The way you're asking the question throws me off a bit. You're referring to the speed of light, but the speed is not as relevant as the curvature of space.

Think of a race car traveling along the race track. You'll notice that the track is banked; that is the outer edge is raised higher than the inner edge where the track curves around. If the roadway is properly banked, then you could hit the curve at speed without turning the steering wheel at all, because the bank would make you travel through the curve in a straight line.

Well this is a pretty good analogy for how heavily curved space-time can still effect even light which has no mass.
It isn't that the gravity is so strong, it even pulls on light. It's that the warping of space-time which gives us the effect of gravity demonstrates such and extreme curve of space that light will travel, at c, in a straight line and still curve back inside of the black hole.
Space-time itself is that curved.

It's curvy enough to make the big bad wolf whistle long and loud.

4. Originally Posted by Neverfly
the outer edge is raised higher than the inner edge where the track curves around. If the roadway is properly banked, then you could hit the curve at speed without turning the steering wheel at all, because the bank would make you travel through the curve in a straight line.

.
Thanks, Neverfly.
a photon emitted by the sun finds the the space "banked" and is deflected all right. But why should this curvature affect its frequency and shift it to the red?

5. Originally Posted by whizkid
Thanks, Neverfly.
a photon emitted by the sun finds the the space "banked" and is deflected all right. But why should this curvature affect its frequency and shift it to the red?
Oh, ok. I see the question. The answer is more complex.
The cause of the effect you're asking about is Gravitational Time Dilation.
This was observed in the experiment done here: Pound

6. [QUOTE=Neverfly;381600]
Originally Posted by whizkid

The cause of the effect you're asking about is Gravitational Time Dilation.
This was observed in the experiment done here: Pound
Yes, but but what accounts for the loss of energy? a rocket leaving the earth is slowed by Time dilation?

7. Originally Posted by whizkid
Yes, but but what accounts for the loss of energy? a rocket leaving the earth is slowed by Time dilation?
A photon moving radially outwards from the sun ( or any other body for that matter ) moves from a lower gravitational potential to a higher one ( the potential is negative and vanishes at infinity ). In order to do so it must perform "work", i.e. it must expand energy. This is what accounts for the difference in energy levels, since the speed of light doesn't change.

8. Originally Posted by whizkid
Yes, but but what accounts for the loss of energy? a rocket leaving the earth is slowed by Time dilation?
Again, the answer to your question is a bit complex and requires a good understanding of Special and General Relativity.
So there's a foundation of underlying knowledge you need.
I'm going to post a series of Wiki articles. Don't sweat that they are wikipedia - the articles are good.
Relativistic Doppler effect - Wikipedia, the free encyclopedia
Equivalence principle - Wikipedia, the free encyclopedia
Gravitational time dilation - Wikipedia, the free encyclopedia
Gravitational redshift - Wikipedia, the free encyclopedia

As you can see, it's a bit to go through... Now, I have no idea how you feel about mathematics. You may look at those articles and say, "No sweat."
But you may also see the math on those pages and say, "What the duck is this ship!?"
If it's the latter, don't worry about the math. Read the articles and grant yourself the trust to accept that there is not a bit of it that is beyond your understanding - even if you are not really experienced in working with the math or reading about such topics on a daily basis.

Markus Hanke and Speedfreek are very good at explaining these topics in terms that are coherent and easy to follow- Me... I'm not so good at it.
ETA: And as I was posting this, Markus Hanke popped up. You're in good hands.

9. Thank you both guys,
but there is something that escapes me.
May be I am wrong, but it seems to me that Physics has three different theories, explanations, of gravity:
a field of energy [ like the electric field ] that propagates at C,
a curved spacetime, and
string theory, which are utterly incompatible with one onother, and are used at one's convenience.

If matter curves spacetime , does it do that at C , or it modifies instantly the whole Universe?
If it doesn't , I suppose my first objection should apply in all 3 cases, whatever explanation one gives of the Nature of gravity

If you care to explain, please, shed some light on the strings: is there any real evidence of that stuff, and how do they work? do they vibrate and make the space ripple?

10. Originally Posted by whizkid
May be I am wrong, but it seems to me that Physics has three different theories, explanations, of gravity
Actually, there is only one currently accepted theory - General Relativity with its curved space-time. String theory is at this point in time a purely hypothetical model, however, it is interesting to note that General Relativity follows directly from String theory, so the latter, should it turn out to be a viable model, will be the more general theory.

If matter curves spacetime , does it do that at C ?
Static gravitational fields instantaneously, whereas changes in the gravitational field propagate at the speed of light.

11. Originally Posted by Markus Hanke

Static gravitational fields instantaneously, whereas.
Thanks, Markus,
that's rather hard to believe, there's nothing static in the universe ! Every body is moving very fast, and g-field are all a-changing, ever !
could you tell me why they cannot accept a simple concept similar to the electric, magnetic field...?
In principle I see no difference between a g-field and a curved space. Why is gravity more difficult to accept/explain than the other forces?
And what about Strings? do they curve space, or what?

12. Originally Posted by whizkid
that's rather hard to believe, there's nothing static in the universe !
Yes, gravitational fields can be static or not, just like any other field. For example our Earth has a gravitational field which is approximately static, since the total mass, angular momentum etc of our planet does not change, so the gravitational field does not change either, i.e. the gravitational acceleration for a given point in space will remain constant.

could you tell me why they cannot accept a simple concept similar to the electric, magnetic field...?
Because unlike EM fields, the gravitational field is self-coupling and therefore non-linear. Remember that all forms of energy are a source of the gravitational field, and that includes the gravitational field itself. Mathematically, EM fields are vector fields whereas the gravitational field is a tensor field.

Why is gravity more difficult to accept/explain than the other forces?
Actually that is not strictly true. For example, quantum chromodynamics ( QCD ) - which describes the strong force - is vastly more complicated to describe and understand than gravity. In fact, QCD is so complicated that we can only treat it numerically with approximation methods ( lattice QCD ).

And what about Strings? do they curve space, or what?
String theory is mathematically consistent only if and when the space-time background is curved; this is how GR is recovered directly from the theory.

13. I think there are obsticles in the pathway that slow the speed there is never nothing.

14. Originally Posted by ARiSe
I think there are obsticles in the pathway that slow the speed there is never nothing.
Gravitational redshift/time-dilation is not the same both ways.

Light coming from a source of gravity that is stronger than the gravity near the observer will be redshifted, so a clock near the Sun would be "running slow" in comparison to a clock on Earth.

Light coming from source of gravity that is weaker than the gravity near the observer will be blueshifted, so a clock on Earth would be "running fast" in comparison to a clock near the Sun.

15. Originally Posted by Markus Hanke
Remember that all forms of energy are a source of the gravitational field, and that includes the gravitational field itself. Mathematically, EM fields are vector fields whereas the gravitational field is a tensor field.

.
Could you , please, explain how a g-field can be a source of another g-field and what evidence is there?
If it were really so, oddly enough, the process would would escalate ad infinitum

Could anyone also expand on Strings? :
-why do they postulate Strings, in the first place, is there any evidence
-are they supposed to be in electrons and protons
-do they vibrate or just curve spacetime?
and, if they are supposed to vibrate, how can they do that ????

16. Originally Posted by whizkid
Could you , please, explain how a g-field can be a source of another g-field and what evidence is there?
If it were really so, oddly enough, the process would would escalate ad infinitum
Like I said already, the source of gravity is energy. Since the gravitational field itself contains energy, it is therefore also a source of itself, so to speak. More accurately, it is self-coupling. In a way that self-coupling continues ad infinitum, but each iteration gives smaller and smaller contributions, so it turns out that the overall system is well behaved and converges nicely to proper numbers, and not to infinity.
The evidence is simple - we have a complete mathematical description of gravitational fields, it is called the Einstein Field Equations. I had a while back opened a thread for these, if you are interested feel free to have a look :

Solving the Einstein Field Equations

These equations are highly non-linear, which is because they contain said self-coupling as well. If you solve these equations you get predictions which can be compared against experiment and observation ( as I have done in above thread with light deflection around the sun ), and as it turns out these predictions give the correct numbers. Refer also here for further details :

Modern Tests of Relativity

why do they postulate Strings, in the first place, is there any evidence
It is an attempt to formulate a model which can explain the origin and behaviour of elementary particles from a common, overarching principle. In short, the different particles correspond to different vibrational modes on a string. Currently this is purely hypothetical, there is not yet any evidence that Strings actually exist.

are they supposed to be in electrons and protons
All elementary particles are just different vibrational modes on Strings.

do they vibrate or just curve spacetime?
They vibrate, but in order to do so in just the right manner to give physical meaningful results, the underlying space-time must be curved.

and, if they are supposed to vibrate, how can they do that ????
I am not certain what you mean by that. Strings have tension and energy, much like a string on a violin or a piano, and can thus vibrate. Unlike the strings in musical instruments though this is not a mechanical but a quantum system, so the lowest possible energy state does not correspond to a static, non-vibrating String - in other words, Strings always vibrate in some manner.

17. Originally Posted by whizkid
Hi,

I hope you can help me solve this problem:

I read that light emerging from a black hole (or from the Sun) is (partially) cancelled by gravity.
How can that be possible since gravity cannot travel faster than the speed of light?

How can the force of gravity produced by the Sun, whatever its nature, can pursue, reach and weaken (or cancel ou) a photon travelling at C?

thank you !
First off whizkid let us not forget that man has no idea what is true with-in a black hole, space or time and so fourth and that for now man can only theorize such things.... So to try to explain the unexplainable is a very difficult thing if you are looking for 100% accurancy.... We can only watch things from here and guess what facts they hold based on sitings by someone other than yourself, which further warps the view from where we stand.... Not so much by the view but by the different perceptions.... Now i'm not saying that anything someone tells you isn't true.... I'm saying its probably only in part true due to an observational mistake or comprehension of the observation....

Now my obsevation of a black hole is that it is the end of star/sun which has slowly pulled its solar system and all mass into it instead of exploding.... Now I say this based on the facts that a black hole pulls everything into it "which may not be true".... And following a model of the perfect sun which I would picture as a white glowing sun/star and burning trillions of years until it burns out and condenses its matter and gravity.... Which would first glow white and slowly turn yellow and so fourth through the spectrum until it turns black in which it would become a dwarf star before it totally burned out to become a black hole.... Which in turn would explain why we have all of these types we can see from here on earth....

Now with a model such as I have explained it makes much easier to see how light is effected in many different ways here and everywhere in the universe and there are too many variables to draw to one single conclusion to your question.... And there may be a place in our universe where it falls 100% true but maybe not everywhere in universe.... There too are many elemental combinations and reactions to conclude a permanent theory that will hold water "so to speak".... And how many other elements and cominations are out there in space that we don't know of ????

18. Originally Posted by whizkid
Originally Posted by Neverfly
the outer edge is raised higher than the inner edge where the track curves around. If the roadway is properly banked, then you could hit the curve at speed without turning the steering wheel at all, because the bank would make you travel through the curve in a straight line.

.
Thanks, Neverfly.
a photon emitted by the sun finds the the space "banked" and is deflected all right. But why should this curvature affect its frequency and shift it to the red?
Well first off lets explain that light contains a tiny part of matter which it carries as it travels and this is how the star/sun slowly expels its matter "which takes a very long time" due to the light particles mass which is nearly nothing.... But not all particles are deflected off the curve only some are which as see by eyes as different effects.... Really pretty simple and an easy way to explain its results....

19. First off whizkid let us not forget that man has no idea what is true with-in a black hole,
Please note that this thread is about light propagating outwards from a black hole, i.e. we are not dealing with whatever happens beyond the event horizon. For the surrounds of a black hole we have a very accurate model of space-time, being the field equations of General Relativity.

20. Originally Posted by warthog213
Well first off lets explain that light contains a tiny part of matter which it carries as it travels and this is how the star/sun slowly expels its matter "which takes a very long time" due to the light particles mass which is nearly nothing.... But not all particles are deflected off the curve only some are which as see by eyes as different effects.... Really pretty simple and an easy way to explain its results....
Photons do not have any mass, only momentum.

21. Originally Posted by warthog213
First off whizkid let us not forget that man has no idea what is true with-in a black hole, space or time and so fourth and that for now man can only theorize such things.... So to try to explain the unexplainable is a very difficult thing if you are looking for 100% accurancy.... We can only watch things from here and guess what facts they hold based on sitings by someone other than yourself, which further warps the view from where we stand.... Not so much by the view but by the different perceptions.... Now i'm not saying that anything someone tells you isn't true.... I'm saying its probably only in part true due to an observational mistake or comprehension of the observation....

Now my obsevation of a black hole is that it is the end of star/sun which has slowly pulled its solar system and all mass into it instead of exploding.... Now I say this based on the facts that a black hole pulls everything into it "which may not be true".... And following a model of the perfect sun which I would picture as a white glowing sun/star and burning trillions of years until it burns out and condenses its matter and gravity.... Which would first glow white and slowly turn yellow and so fourth through the spectrum until it turns black in which it would become a dwarf star before it totally burned out to become a black hole.... Which in turn would explain why we have all of these types we can see from here on earth....

Now with a model such as I have explained it makes much easier to see how light is effected in many different ways here and everywhere in the universe and there are too many variables to draw to one single conclusion to your question.... And there may be a place in our universe where it falls 100% true but maybe not everywhere in universe.... There too are many elemental combinations and reactions to conclude a permanent theory that will hold water "so to speak".... And how many other elements and cominations are out there in space that we don't know of ????
Our Sun lacks the mass to collapse into a Black Hole- but let's ignore that for the moment.

If our Sun (magically) collapsed into a Black Hole, what effect would this have on the other planets of our solar system?
They would be colder.
The planets in orbit are held by the gravity of the Sun which is proportional to its Mass. If the Sun became a black hole, it's mass would not change (Not by much, in actuality, so matter is expelled into space in the process, but again, we'll ignore that as we're hypothesizing a magical cause for our Sun to collapse into a BH). Since the mass does not change, at this distance, the Earth would feel the same pull. Our orbit would continue unchanged.

Originally Posted by warthog213
Well first off lets explain that light contains a tiny part of matter which it carries as it travels and this is how the star/sun slowly expels its matter "which takes a very long time" due to the light particles mass which is nearly nothing.... But not all particles are deflected off the curve only some are which as see by eyes as different effects.... Really pretty simple and an easy way to explain its results....
EM radiation does not have Mass. It does, however, have momentum and can alter the trajectory of tiny particles in a game of cosmic billiards. Light does not 'carry matter with it, though.'

22. Neverfly
EM radiation does not have Mass. It does, however, have momentum and can alter the trajectory of tiny particles in a game of cosmic billiards. Light does not 'carry matter with it, though.'[/QUOTE]

Now here you say tiny particals, "which is mass" very little but none the less mass of a sort.... And also I said that over millions of years the suns mass deteriorates in stages from a white hot sun (newly formed sun) in a perfect model to a black dwarf star and then into a black whole and slowly pulls everything around it into it as it slowly burns out.... And also I said that in this model that the sun was radiating its mass away from it burning in the form of light.... Fact basis for this model is fire and things which burn which turn to ash, all natural effects which can not be denied.... I never said that the sun would magicaly form into a black hole, I said in a model of the perfect sun it forms into a white sun and over billions of years it changes by burning out slowly by expelling its matter and its condensing its matter which it can not expel into a dwarf star which also turns into a black hole over billions of years.... And I said it will be thousands of years for this idea to ever be proven wrong or right.... I beleive in nature and its forces because it has outlasted men by billions of trillions of years.... And this we know because it has taken some light particals from distant stars to travel here billions of years alone just arrive here on earth.... And those particals at least some of them have traveled here in a straight line which blows your theory about bending light out of the water because most particals pass through and some are curved of their trajectory.... Hopefully you can comprehend this concept/explanation a bit more > .

23. Originally Posted by warthog213
So to try to explain the unexplainable is a very difficult thing if you are looking for 100% accurancy...

I am not looking for 100% accuracy, but for a consistent explanation of gravity and its effects on light.

Whowever does not understand relativity is considered an ignorant or a fool, but the point is that one can predict a result ascribing that same result to a great number of causes, including illegitimate ones; the fact that Einstein predicted the deflection of light around the Sun, does not justify the basic arbitrary, unlawful logical (and scientific) operations performed by Relativity: I'll explain my idea

1) In this very moment you have threads questioning the very existence of TIME, nobody knows if it really exists or is an alias for CHANGE or other, if it does exist nobody knows what it is, what its porperties , if any etc..
2) SPACE is just an intuitive notion , but physics has sofar no idea if it is empy, i.e. the Nothingness, or a kind of potential, virtual energy , what are its property, if any etc.

My question is very simple:
how can anyone imagine or state that space CAN be curved: is it made of particles?, is it otherwise straight? can you curve beauty, energy, heat...?
how can a curved space maintain its previous properties, granting it can be curved?
how can anyone consider scientific, let alone plausible, that such TWO vague concepts can be merged into ONE: a space-time? can we postulate space-beauty?

But my purpose is not questioning GR, I wouldn't have a chance, I am only trying to understand the explanations which are currently cosidered true.

Originally Posted by Markus Hanke
. Since the gravitational field itself contains energy, it is therefore also a source of itself, so to speak.
....in other words, Strings always vibrate in some manner.
I thank you Markus for your clear explanations, I hope you can be more precise: is that statement apodictical or is there a logical or scientific proof that if something contains energy, must be itself a source of energy?, the electric field does not contain energy?
What I am trying to investigate is the need of a warped spacetime to justify the minor correction (by a factor of two) of the classical prediction GMm/r^2
What is the ratio, the formula of the self-reproducing energy?

24. Originally Posted by warthog213
And also I said that over millions of years the suns mass deteriorates in stages from a white hot sun (newly formed sun) in a perfect model to a black dwarf star and then into a black whole and slowly pulls everything around it into it as it slowly burns out.... And also I said that in this model that the sun was radiating its mass away from it burning in the form of light.... Fact basis for this model is fire and things which burn which turn to ash, all natural effects which can not be denied....
It absolutely can be denied. What you're saying is totally inaccurate. The Sun operates by Nuclear Fusion, not burning of wood. It does not burn its fuel away in fire. The energy we get from the Sun is the product of fusion- as it fuses Hydrogen into Helium and so on.
It's not radiating all its mass away.
A star needs a critical mass in order to have enough gravity to form a black hole.
If it lacks sufficient mass it will convert to either a dwarf star after going nova or into a Neutron star.
Originally Posted by warthog213
I never said that the sun would magicaly form into a black hole
I never said anything even hinting that you had said that. I am the one who said that in using it as an example in explaining that Black holes are not cosmic vacuum cleaners that hoover everything up.
Originally Posted by warthog213
I said in a model of the perfect sun it forms into a white sun and over billions of years it changes by burning out slowly by expelling its matter and its condensing its matter which it can not expel into a dwarf star which also turns into a black hole over billions of years....
This is not correct.
Originally Posted by warthog213
And I said it will be thousands of years for this idea to ever be proven wrong or right....
This is not correct. Not only do you need to work on your reading comprehension, but on reigning in your imagination and assumptions.
Originally Posted by warthog213
And those particals at least some of them have traveled here in a straight line which blows your theory about bending light out of the water because most particals pass through and some are curved of their trajectory.... Hopefully you can comprehend this concept/explanation a bit more > .
Light always travels in a straight line. But space can be curved. This causes light to travel in a straight line through curved space.

You would do well to do more learning and less making up crap. You haven't got the slightest clue what you're talking about.

Gravitational lens - Wikipedia, the free encyclopedia

Einstein ring - Wikipedia, the free encyclopedia

25. Photons exist, which in turn means that they contain some portion of matter how ever inmeasurable it may be, its still some form of matter.... Its also fuel and energy which also contains different portions of matter.... >"The intrinsic properties of photons, such as charge, mass and spin, are determined by the properties of this gauge symmetry" < a quote from wiki

26. Originally Posted by warthog213
Photons exist, which in turn means that they contain some portion of matter how ever inmeasurable it may be, its still some form of matter....
Here you go again, making baseless assumptions without actual knowledge because you think it's all just 'common horse sense.'

You have no idea how the scientific method works. It's not philosophy nor is it the realm of Make Believe.

27. Photons exist, which in turn means that they contain some portion of matter how ever inmeasurable it may be, its still some form of matter.... Its also fuel and energy which also contains different portions of matter.... >"The intrinsic properties of photons, such as charge, mass and spin, are determined by the properties of this gauge symmetry" < a quote from wiki

Now having said that.... Some light particals must escape a black hole or radiate their own form of light or we wouldn't be able to see them at all....

Whizkid
I read that light emerging from a black hole (or from the Sun) is (partially) cancelled by gravity.
How can that be possible since gravity cannot travel faster than the speed of light?
Warthog213
Though I have established that light does have some matter, it however doesn't have enough matter for gravity to pull on for the most part.... This isn't true and it evident here on earth as the suns light travels straight here and from distant stars which clearly are seen here on earth daily/nightly.... Any contaminated particals would be heavier and have more matter and are effected by forces.... I also think that a black hole is a sun that has burned out and perhaps is omitting its own light on a different spectrum.... Which to me makes a ton of sense.... The model for this is the fact that if set a bonfire, what is left when it burns out>>>> the opposite of what it was before the fire started....

28. Originally Posted by warthog213
Photons exist, which in turn means that they contain some portion of matter how ever inmeasurable it may be, its still some form of matter.... Its also fuel and energy which also contains different portions of matter.... >"The intrinsic properties of photons, such as charge, mass and spin, are determined by the properties of this gauge symmetry" < a quote from wiki
Quote mining is never impressive. Support your claim that photos are matter.
Originally Posted by warthog213
Now having said that.... Some light particals must escape a black hole or radiate their own form of light or we wouldn't be able to see them at all....
We do not and have never seen black holes. You have a great many serious misconceptions about astronomy. I suggest you start clearing them up- rather than asserting your misconceptions as facts and waving aside correction.
Originally Posted by warthog213
Though I have established that light does have some matter,
You most certainly have not established anything of the kind.
Originally Posted by warthog213
it however doesn't have enough matter for gravity to pull on for the most part.... This isn't true and it evident here on earth as the suns light travels straight here and from distant stars which clearly are seen here on earth daily/nightly.... Any contaminated particals would be heavier and have more matter and are effected by forces.... I also think that a black hole is a sun that has burned out and perhaps is omitting its own light on a different spectrum.... Which to me makes a ton of sense.... The model for this is the fact that if set a bonfire, what is left when it burns out>>>> the opposite of what it was before the fire started....
This is the biggest load of hogwash I've seen in a long while. Must be Warthogwash.

Warthog- allow me to be clear. It's people like you that spread misinformation in an ego driven frenzy to be recognized that screws up serious people that are interested in science. You'd do better to just keep your ideas to yourself if you have no intention of learning. You hold others back, create confusion and contribute nothing to educate minds except provide an example of how not to be.

29. Originally Posted by whizkid
is there a logical or scientific proof that if something contains energy, must be itself a source of energy?
Careful now, don't get confused - the discussion is about gravity. Therefore, the statement was not that energy is a source of itself, but that energy is a source of gravity. And since the gravitational field contains energy as well, it is self-coupling.

the electric field does not contain energy?
Yes it does, but the source of the electric field is electric charge; EM fields are not self-coupling, which is one of the main differences between EM and gravity.

What I am trying to investigate is the need of a warped spacetime to justify the minor correction (by a factor of two) of the classical prediction GMm/r^2
The correction is only minor for weak gravitational fields. If the fields are very strong, the inverse square law simply ceases to be valid, not even approximately.

What is the ratio, the formula of the self-reproducing energy?
Once again, energy is not self-reproducing, it is rather the curvature of space-time which is non-linear. The field equation is

which is a non-linear set of partial differential equations. It is the non-linearity of this system of equations which corresponds to the self-coupling.

Whowever does not understand relativity is considered an ignorant or a fool
That is not true. We all know that relativity can be a difficult beast to grasp, so no one is considered ignorant just because he/she doesn't understand relativity. Ignorant are only those people who say "I don't understand it, it makes no sense to me, thus it must be false !!".

how can anyone imagine or state that space CAN be curved: is it made of particles?, is it otherwise straight? can you curve beauty, energy, heat...?
Firstly, it is space-time, not just space. The two are not distinguishable in GR. It is not made of particles, and whether or not beauty, energy and heat can be curved seems entirely meaningless to me since those aren't geometrical concepts, unlike space-time. The reason why one can postulate that space-time is curved is that we cannot actually see, feel touch or grasp space-time - we can only perform measurements in it. You can measure how far apart in space two events take place, and you can measure how far apart in time two events take place. Note that both of these are distances, namely distances in space and distances in time. As it turns out, mathematically there is no difference in the way you treat those distances, so it is convenient to combine them into one manifold, being space-time. If you really, really wanted to you could of course keep them separate and treat them separate, but it makes no sense since they behave in the exact same way so far as measurements are concerned.
So here we are now - GR is a theory about measurements in space-time, and how measurements performed by observers relate to each other. One then takes into account the Equivalence Principle, being that acceleration and gravity are not distinguishable in the same frame of reference. This is really the heart of GR, everything else is just maths - the mathematical description of the Equivalence Principle leads to a space-time which has intrinsic curvature around sources of gravity.
Note that Einstein started with the Equivalence Principle, not with curved space-time; the latter is a result of describing the former mathematically.

how can a curved space maintain its previous properties, granting it can be curved?
What properties are you referring to ?

how can anyone consider scientific, let alone plausible, that such TWO vague concepts can be merged into ONE: a space-time?
See above - both can be defined via the notion of geometrical distance. Think events in space-time, rather than points in space.

I am only trying to understand the explanations which are currently cosidered true.
That's perfectly fine. Bear in mind though that there is a limit to what can be explained in words, from a certain point onwards one would have to get the maths involved. For example, the self-coupling of the gravitational field is largely a mathematical phenomenon, and difficult to show in plain text.

30. Originally Posted by warthog213
Photons exist, which in turn means that they contain some portion of matter how ever inmeasurable it may be, its still some form of matter
Not correct. Photons exist, but they have vanishing rest mass because they do not couple to the underlying Higgs field. They only possess momentum.

The intrinsic properties of photons, such as charge, mass and spin, are determined by the properties of this gauge symmetry
This is a generic statement which is true for all fundamental particles. In the case of the photon :

Mass = 0
Spin = 1
Charge = 0

If you look on the right hand side of that very page ( Photon - Wikipedia, the free encyclopedia ) you would have seen that.

Some light particals must escape a black hole
They do so long as they originate outside the event horizon.

radiate their own form of light
No, photons do not emit other photons.

Though I have established that light does have some matter
The only two things you have established thus far is that you do not possess much knowledge about this subject, while at the same time refusing to listen to our explanations.

Which to me makes a ton of sense....
It may make sense to you, but is woefully wrong scientifically. Black holes are the results of the gravitational collapse of a body, the highest form of degeneracy for matter. The original body is in most cases a massive star, though there are other processes which also may lead to black holes ( primordial black holes ). In either case, black holes aren't "normal" bodies just gone dark.

and then into a black whole and slowly pulls everything around it into it as it slowly burns out
The sun does not have enough mass to collapse into a black hole.

And those particals at least some of them have traveled here in a straight line which blows your theory about bending light out of the water because most particals pass through and some are curved of their trajectory.

31. A quote from the wiki for photons::::Copied and pasted here for everyone to see::::

"In the Standard model of particle physics, photons are described as a necessary consequence of physical laws having a certain symmetry at every point in spacetime. The intrinsic properties of photons, such as charge, mass and spin, are determined by the properties of this gauge symmetry. The photon concept has led to momentous advances in experimental and theoretical physics, such as lasers, Bose–Einstein condensation, quantum field theory, and the probabilistic interpretation of quantum mechanics. It has been applied to photochemistry, high-resolution microscopy, and measurements of molecular distances. Recently, photons have been studied as elements of quantum computers and for sophisticated applications in optical communication such as quantum cryptography"

Now this funny because in the first of the statement on wiki it says that photons have no mass which I know they don't in the traditional sense but facts are facts and they do exist which means that must have some form of mass which is equal to the mass of any proton, neutron or electron and the fact that they are expelled by a source means that they too are certain special part of that mass which expelled it.... I always check my sources before I post constantly....

32. In special relativity, it turns out that we are still able to define a particle's momentum p such that it behaves in well-defined ways that are an extension of the newtonian case. Although p and v still point in the same direction, it turns out that they are no longer proportional; the best we can do is relate them via the particle's "relativistic mass" mrel. Thus
p = mrelv . When the particle is at rest, its relativistic mass has a minimum value called the "rest mass" mrest. The rest mass is always the same for the same type of particle. For example, all protons, electrons, and neutrons have the same rest mass; it's something that can be looked up in a table. As the particle is accelerated to ever higher speeds, its relativistic mass increases without limit.
It also turns out that in special relativity, we are able to define the concept of "energy" E, such that E has simple and well-defined properties just like those it has in newtonian mechanics. When a particle has been accelerated so that it has some momentum p (the length of the vector p) and relativistic mass mrel, then its energy E turns out to be given by
E = mrelc2 , and also E2 = p2c2 + m2restc4 . (1)
There are two interesting cases of this last equation:
1. If the particle is at rest, then p = 0, and E = mrestc2.
2. If we set the rest mass equal to zero (regardless of whether or not that's a reasonable thing to do), then E = pc.
In classical electromagnetic theory, light turns out to have energy E and momentum p, and these happen to be related by E = pc. Quantum mechanics introduces the idea that light can be viewed as a collection of "particles": photons. Even though these photons cannot be brought to rest, and so the idea of rest mass doesn't really apply to them, we can certainly bring these "particles" of light into the fold of equation (1) by just considering them to have no rest mass. That way, equation (1) gives the correct expression for light, E = pc, and no harm has been done. Equation (1) is now able to be applied to particles of matter and "particles" of light. It can now be used as a fully general equation, and that makes it very useful.
Is there any experimental evidence that the photon has zero rest mass?

33. but facts are facts and they do exist which means that must have some form of mass
This is a logical fallacy. Existence does not imply mass.

A quote from the wiki for photons::::Copied and pasted here for everyone to see::::
Why did you not quote the bit from that very same page that says that mass and charge are both zero ?

Is there any experimental evidence that the photon has zero rest mass?
You can never proof experimentally that something has an exact value, you can only place upper/lower limits on a measurement. In the case of the photon that limit is of the order of 10-18 eV/c2 - refer here :

Phys. Rev. Lett. 80, 1826 (1998): Experimental Limits on the Photon Mass and Cosmic Magnetic Vector Potential

34. but facts are facts and they do exist which means that must have some form of mass which is equal to the mass of any proton, neutron or electron and the fact that they are expelled by a source means that they too are certain special part of that mass which expelled it.... I always check my sources before I post constantly....
Then you either need better sources, or you need a basic education so you can understand what your sources are actually saying, because EVERYTHING you've posted has been incorrect.

35. Originally Posted by AlexG
but facts are facts and they do exist which means that must have some form of mass which is equal to the mass of any proton, neutron or electron and the fact that they are expelled by a source means that they too are certain special part of that mass which expelled it.... I always check my sources before I post constantly....
Then you either need better sources, or you need a basic education so you can understand what your sources are actually saying, because EVERYTHING you've posted has been incorrect.
My sources are from other people just as yours are and are just as reliable in my opinion....
Which further brings us closer to the paradox of man>>>> sometimes he just over thinks things....
I was an honor role student in high school.... Also I give my father the full rundown as to why some of his inventions wouldn't work.... But then again I have just a general education because I have been working for people since the age of 13 yrs old with "thousands"of successful jobs done and people pleased to have them done at the lowest possible expense.... You can't just draw everything out on paper and expect everyone to understand it, but it is however a good start.... Most people can read a blueprint but it however amuses me when I run into the few who are lost when looking at a simple drawing and refuse to understand it.... After all trying to explain some new concept to a scientific mind bares a striking resemblance to trying to teach a slug to speak, he just goes about his sluggish ways adhering to what he knows works for him.... Not complaining because I understand that entirerly because I too use that method in creating and building things everyday>>> my hands are my hands and thats what they are because they are just hands but they build what I conceive daily which you (a scientist) are very limited to achieve on a daily basis....
So shoot your bullets of anger for they won't come through my screen and kill me, i'll still be alive and well and doing what do....

36. After all trying to explain some new concept to a scientific mind bares a striking resemblance to trying to teach a slug to speak, he just goes about his sluggish ways adhering to what he knows works for him
If you know anything about what you're trying to explain, it might work. As it is, you don't, so it doesn't.

I have been working for people since the age of 13 yrs old with "thousands"of successful jobs done and people pleased to have them done at the lowest possible expense...
Mowing lawns and shoveling driveways doesn't add anything to your knowledge or credibility.

37. Originally Posted by Neverfly
The way you're asking the question throws me off a bit. You're referring to the speed of light, but the speed is not as relevant as the curvature of space.

Think of a race car traveling along the race track. You'll notice that the track is banked; that is the outer edge is raised higher than the inner edge where the track curves around. If the roadway is properly banked, then you could hit the curve at speed without turning the steering wheel at all, because the bank would make you travel through the curve in a straight line.

Well this is a pretty good analogy for how heavily curved space-time can still effect even light which has no mass.
It isn't that the gravity is so strong, it even pulls on light. It's that the warping of space-time which gives us the effect of gravity demonstrates such and extreme curve of space that light will travel, at c, in a straight line and still curve back inside of the black hole.
Space-time itself is that curved.

It's curvy enough to make the big bad wolf whistle long and loud.
You're referring to the speed of light, but the speed is not as relevant as the curvature of space.
The way you are answering the question is throwing me off some. Could you explain?

38. Originally Posted by AlexG
After all trying to explain some new concept to a scientific mind bares a striking resemblance to trying to teach a slug to speak, he just goes about his sluggish ways adhering to what he knows works for him
If you know anything about what you're trying to explain, it might work. As it is, you don't, so it doesn't.

I have been working for people since the age of 13 yrs old with "thousands"of successful jobs done and people pleased to have them done at the lowest possible expense...
Mowing lawns and shoveling driveways doesn't add anything to your knowledge or credibility.
I don't think you are right, there is always something to learn unless you are stupid.

39. Originally Posted by warthog213
My sources are from other people just as yours are and are just as reliable in my opinion....
Hardly. Much of it was stuff that you, yourself, made up in your own mind.

Originally Posted by warthog213
I was an honor role student in high school....
Yet, you can't spell "roll" much less half of anything else you type. Your grammar is almost non-existent, you totally misuse punctuation and your scientific knowledge is pretty much 3rd grade level. No, I do not believe you were Honor Roll and if you were, then your school needs serious evaluation.
Originally Posted by warthog213
So shoot your bullets of anger for they won't come through my screen and kill me, i'll still be alive and well and doing what do....
Doing what you do- spreading misinformation?

40. Moderator Comment: Let's tone down the personal remarks fellow members. I'll be watching this thread and will skewer the next member who fails to take note.

Moderator Warning: warthog213, it does appear that your understanding of some of the topic being discussed here is faulty. Unfortunately you insist upon presenting your opinions as if they were well validated and at least the equal of those who have done proper study in the area. In future please make it clear your are expressing an opinion, or provide a proper citation - wikipedia really won' cut it in this case. alternatively - and this would be best - get yourself educated in the matter before you post further definitive statements.

41. Lecture 20: Black Holes
 Astronomy 162: Introduction to Stars, Galaxies, & the Universe Prof. Richard Pogge, MTWThF 9:30
Lecture 20: Black Holes

Readings: Ch 24, sections 24-3, 5, 6, 7 & 8 Key Ideas

Black Holes are totally collapsed objects gravity so strong not even light can escape predicted by General Relativity Schwarzschild Radius & Event Horizon Find them by their Gravity X-ray Binary Stars Black Hole Evaporation Emit "Hawking Radiation"
Gravity's Final Victory

A star more massive than about 18 Msun would leave behind a post-supernova core this is larger than 2-3 Msun:
Neutron degeneracy pressure would fail and nothing can stop its gravitational collapse.
Core would collapse into a singularity, and object with
• infinite density

Black Hole

The Ultimate Extreme Object
• Gravity is so strong that nothing, not even light, can escape.
• Infalling matter is shredded by powerful tides and crushed to infinite density.
• Escape speed exceeds the speed of light.

Becomes a Black Hole:
• "Black" because they neither emit nor reflect light.
• "Hole" because nothing entering can ever escape.

Light cannot escape from a Black Hole if it comes from a radius closer than the Schwarzschild Radius, RS to the singularity: Where M = Mass of the Black Hole
A black hole with a mass of 1 Msun would have a Schwarzschild Radius of RS=3 km.
Compare this with a typical 0.6 Msun White Dwarf, which would have a radius of about 1 Rearth (6370km), and a 1.4 Msun neutron star, which would have a radius of about 10km. Comparison of a 1.5 Msun Black Hole and Neutron Star with Island of Manhattan for scale.
RS is named for German physicist Karl Schwarzschild who in 1916 was one of the first people to explore the implications of Einstein's then-new General Theory of Relativity, the modern theory of Gravity.
The Event Horizon

RS defines the "Event Horizon" surrounding the black hole's singularity:
• Events occurring inside RS are invisible to the outside universe.
• Anything closer to the singularity than RS can never leave the black hole
• The Event Horizon hides the singularity from the outside universe.

The Event Horizon marks the "Point of No Return" for objects falling into a Black Hole.
Gravity around Black Holes

Far away from a black hole:
• Gravity is the same as that of star of the same mass.

Close to a black hole:
• R < 3 RS, there are no stable orbits - all matter gets sucked in.
• At R = 1.5 RS, photons would orbit in a circle!

Journey to a Black Hole: A Thought Experiment

Two observers: Jack & Jill Jack, in a spacesuit, is falling into a black hole. He is carrying a low-power laser beacon that flashes a beam of blue light once a second. Jill is orbiting the black hole in a starship at a safe distance away in a stable circular orbit. She watches Jack fall in by monitoring the incoming flashes from his laser beacon.
He Said, She Said...
From Jack's point of view:
• He sees the ship getting further away.
• He flashes his blue laser at Jill once a second by his watch.

From Jill's point of view:
• Each laser flash take longer to arrive than the last
• Each laser flash become redder and fainter than the one before it.

Near the Event Horizon...
Jack Sees:
• His blue laser flash every second by his watch
• The outside world looks oddly distorted (positions of stars have changed since he started).

Jill Sees:
• Jack's laser flashing about once every hour.
• The laser flashes are now shifted to radio wavelengths, and
• the flashes are getting fainter with each flash.

Down the hole...
Jill Sees:
• One last flash from Jack's laser after a long delay (months?)
• The last flash is very faint and at very long radio wavelengths.
• She never sees another flash from Jack...

Jack Sees:
• The universe appear to vanish as he crosses the event horizon
• He gets shredded by strong tides near the singularity and crushed to infinite density.

Moral:
The powerful gravity of a black hole warps space and time around it:
• Time appears to stand still at the event horizon as seen by a distant observer.
• Time flows as it always does as seen by an infalling astronaut.
• Light emerging from near the black hole is Gravitationally Redshifted to longer (red) wavelengths.

Take a Virtual Trip to a Black Hole or Neutron Star. Pictures & movies by relativist Robert Nemiroff at the Michigan Technical University.
Seeing what cannot be seen...

Question: If black holes are black, how can we hope to see them? Answer: Look for the effects of their gravity on their surroundings.
• Look for stars orbiting around an unseen massive object
• Look for X-rays emitted by gas that is superheated as it falls into a black hole.

X-Ray Binaries

Bright, variable X-ray sources identified by X-ray observatory satellites:
• Spectroscopic binary with only one set of spectral lines - the second object is invisible.
• Gas from the visible star is dumped on the companion, heats up, and emits X-rays.

Estimate the mass of the unseen companion from the parameters of its orbit.
• A black hole candidate, conservatively, would be a system in which the mass of the unseen companion was larger than 3 Msun, the more massive the better.

Black Hole Candidates

A number of X-ray binaries have been found with unseen companions with Masses > 3 Msun, too big for a Neutron Star.
Currently 20 confirmed black hole candidates in our Galaxy: First was Cygnus X-1: M = 7-13 Msun Largest is GRS1915+105: M = 10-18 Msun Most are in the range 4-10 Msun
Estimated to be as many as 1 Billion stellar-mass black holes in our Galaxy, which points out how very hard it is to find something that does not emit any radiation of its own.
Black Holes are not totally Black!

"Classical" General Relativity says:
• Black Holes are totally black
• Can only grow in mass and size
• Last forever (nothing gets out once inside)

But, General Relativity does not include the effects of Quantum Mechanics.
Evaporating Black Holes

Black Holes evaporate slowly by emitting subatomic particles and photons via "Hawking Radiation":
• Very cold thermal radiation (Temperatures of ~10 nanoKelvin)
• Bigger Black holes are colder
The smaller the mass, the hotter the black hole, and so the faster the evaporation.
For black holes in the real universe, the evaporation rate is VERY slow:
• A 3 Msun black hole would require about 1063 years to completely evaporate.
• This is about 1053 times the present age of the Universe.
Probably unimportant today, but it could be an important process in the distant future of the Universe.
A Final Word

Physicist John Archibald Wheeler (b. 1911), who coined the term "black hole", has been one of the most innovative thinkers on space and time. The singularity at the center of the black hole, which we passed over quickly, is not a simple beast. Its existance, at least in the classical theory of relativity, is a real problem that is telling us about the limits of our ideas. Prof. Wheeler has put it this way:
[The black hole] "teaches us that space can be crumpled like a piece of paper into an infinitesimal dot, that time can be extinguished like a blown-out flame, and that the laws of physics that we regard as 'sacred', as immutable, are anything but."
from "Geons, Black Holes, & Quantum Foams: A Life in Physics" by Wheeler and Ford (1998, AIP Press)
Return to [ Unit 3 Index | Astronomy 162 Main Page ]
Updated: 2007 August 3

You see John I read very well, and I do hope this helps you understand a little better whizkid.... "warthog213"

42. Lecture 20: Black Holes
 Astronomy 162: Introduction to Stars, Galaxies, & the Universe Prof. Richard Pogge, MTWThF 9:30

Lecture 20: Black Holes

Readings: Ch 24, sections 24-3, 5, 6, 7 & 8 Key Ideas

Black Holes are totally collapsed objects gravity so strong not even light can escape predicted by General Relativity Schwarzschild Radius & Event Horizon Find them by their Gravity X-ray Binary Stars Black Hole Evaporation Emit "Hawking Radiation"
Gravity's Final Victory

A star more massive than about 18 Msun would leave behind a post-supernova core this is larger than 2-3 Msun:
Neutron degeneracy pressure would fail and nothing can stop its gravitational collapse.
Core would collapse into a singularity, and object with
• infinite density

Black Hole

The Ultimate Extreme Object
• Gravity is so strong that nothing, not even light, can escape.
• Infalling matter is shredded by powerful tides and crushed to infinite density.
• Escape speed exceeds the speed of light.
Becomes a Black Hole:
• "Black" because they neither emit nor reflect light.
• "Hole" because nothing entering can ever escape.

Light cannot escape from a Black Hole if it comes from a radius closer than the Schwarzschild Radius, RS to the singularity: Where M = Mass of the Black Hole
A black hole with a mass of 1 Msun would have a Schwarzschild Radius of RS=3 km.
Compare this with a typical 0.6 Msun White Dwarf, which would have a radius of about 1 Rearth (6370km), and a 1.4 Msun neutron star, which would have a radius of about 10km. Comparison of a 1.5 Msun Black Hole and Neutron Star with Island of Manhattan for scale.
RS is named for German physicist Karl Schwarzschild who in 1916 was one of the first people to explore the implications of Einstein's then-new General Theory of Relativity, the modern theory of Gravity.
The Event Horizon

RS defines the "Event Horizon" surrounding the black hole's singularity:
• Events occurring inside RS are invisible to the outside universe.
• Anything closer to the singularity than RS can never leave the black hole
• The Event Horizon hides the singularity from the outside universe.
The Event Horizon marks the "Point of No Return" for objects falling into a Black Hole.
Gravity around Black Holes

Far away from a black hole:
• Gravity is the same as that of star of the same mass.
Close to a black hole:
• R < 3 RS, there are no stable orbits - all matter gets sucked in.
• At R = 1.5 RS, photons would orbit in a circle!

Journey to a Black Hole: A Thought Experiment

Two observers: Jack & Jill Jack, in a spacesuit, is falling into a black hole. He is carrying a low-power laser beacon that flashes a beam of blue light once a second. Jill is orbiting the black hole in a starship at a safe distance away in a stable circular orbit. She watches Jack fall in by monitoring the incoming flashes from his laser beacon.
He Said, She Said...
From Jack's point of view:
• He sees the ship getting further away.
• He flashes his blue laser at Jill once a second by his watch.
From Jill's point of view:
• Each laser flash take longer to arrive than the last
• Each laser flash become redder and fainter than the one before it.
Near the Event Horizon...
Jack Sees:
• His blue laser flash every second by his watch
• The outside world looks oddly distorted (positions of stars have changed since he started).
Jill Sees:
• Jack's laser flashing about once every hour.
• The laser flashes are now shifted to radio wavelengths, and
• the flashes are getting fainter with each flash.
Down the hole...
Jill Sees:
• One last flash from Jack's laser after a long delay (months?)
• The last flash is very faint and at very long radio wavelengths.
• She never sees another flash from Jack...
Jack Sees:
• The universe appear to vanish as he crosses the event horizon
• He gets shredded by strong tides near the singularity and crushed to infinite density.
Moral:
The powerful gravity of a black hole warps space and time around it:
• Time appears to stand still at the event horizon as seen by a distant observer.
• Time flows as it always does as seen by an infalling astronaut.
• Light emerging from near the black hole is Gravitationally Redshifted to longer (red) wavelengths.
Take a Virtual Trip to a Black Hole or Neutron Star. Pictures & movies by relativist Robert Nemiroff at the Michigan Technical University.
Seeing what cannot be seen...

Question: If black holes are black, how can we hope to see them? Answer: Look for the effects of their gravity on their surroundings.
• Look for stars orbiting around an unseen massive object
• Look for X-rays emitted by gas that is superheated as it falls into a black hole.

X-Ray Binaries

Bright, variable X-ray sources identified by X-ray observatory satellites:
• Spectroscopic binary with only one set of spectral lines - the second object is invisible.
• Gas from the visible star is dumped on the companion, heats up, and emits X-rays.
Estimate the mass of the unseen companion from the parameters of its orbit.
• A black hole candidate, conservatively, would be a system in which the mass of the unseen companion was larger than 3 Msun, the more massive the better.

Black Hole Candidates

A number of X-ray binaries have been found with unseen companions with Masses > 3 Msun, too big for a Neutron Star.
Currently 20 confirmed black hole candidates in our Galaxy: First was Cygnus X-1: M = 7-13 Msun Largest is GRS1915+105: M = 10-18 Msun Most are in the range 4-10 Msun
Estimated to be as many as 1 Billion stellar-mass black holes in our Galaxy, which points out how very hard it is to find something that does not emit any radiation of its own.
Black Holes are not totally Black!

"Classical" General Relativity says:
• Black Holes are totally black
• Can only grow in mass and size
• Last forever (nothing gets out once inside)
But, General Relativity does not include the effects of Quantum Mechanics.
Evaporating Black Holes

Black Holes evaporate slowly by emitting subatomic particles and photons via "Hawking Radiation":
• Very cold thermal radiation (Temperatures of ~10 nanoKelvin)
• Bigger Black holes are colder
The smaller the mass, the hotter the black hole, and so the faster the evaporation.
For black holes in the real universe, the evaporation rate is VERY slow:
• A 3 Msun black hole would require about 1063 years to completely evaporate.
• This is about 1053 times the present age of the Universe.
Probably unimportant today, but it could be an important process in the distant future of the Universe.
A Final Word

Physicist John Archibald Wheeler (b. 1911), who coined the term "black hole", has been one of the most innovative thinkers on space and time. The singularity at the center of the black hole, which we passed over quickly, is not a simple beast. Its existance, at least in the classical theory of relativity, is a real problem that is telling us about the limits of our ideas. Prof. Wheeler has put it this way:
[The black hole] "teaches us that space can be crumpled like a piece of paper into an infinitesimal dot, that time can be extinguished like a blown-out flame, and that the laws of physics that we regard as 'sacred', as immutable, are anything but."
from "Geons, Black Holes, & Quantum Foams: A Life in Physics" by Wheeler and Ford (1998, AIP Press)
Return to [ Unit 3 Index | Astronomy 162 Main Page ]
Updated: 2007 August 3

You see John I read very well, and I do hope this helps you understand a little better whizkid.... "warthog213"

43. Right, so where does any of that say that photons have mass?

44. Posting large sections of copyrighted material

1. Is a no no.

2. Doesn't demonstrate that you have any understanding of what you cut and pasted.

45. Once again, photons do not have mass, they only have momentum. Your failure to acknowledge that fact does not make it any less true, you know.

46. Emergence of light from the sun had been a controversial issue among the scientist, this document encompasses different views related to it

Light-Classical Physics-Handouts, light Electromagnetic Wave - Docsity.com

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