FTL, Photon Mass and Black Holes

[retic]

Ok, First I want to state upfront I am not a scientist, just a welder with an over active brain and a question that has been keeping me up at night.<br />I've been searching through posts and lurking for awhile I keep reading that FTL travel is at this moment due to current Hypotheses impossible, mostly due to mass increase at relativistic speeds.<br />So the question is energy, you have to eject mass backwards to accelerate forwards in a linear fashion, so first I thought about ejecting photons IE light or another EM wave then I read photons have no mass. <br />My question Is if Photons have no mass how can they be affected by gravity ? Like a black hole sucking in Light ect. if it is due to space warping around the black hole then wouldn't that make space a medium in it's own right that light has to travel through.<br />Another thing why do they always show black holes warping space into a cone, if a black hole is caused by a collapsed star wouldn't it exert the same force on space in a 360deg globe ?<br />thanks in advance for info or even pointers to find this, I did take physics in High School but either I didn't pay close enough attention or we never discussed it. (these topics)

 

[Slate]

Well im no scientist either but this is a subject I have had interest in for some time. <br />From what I have read and answers I have received to questions here and elsewhere.<br />Gravity does not effect light its self it only effects the space in which the light particle is traveling trough. Light can only travel in a straight line from point of origin to the point of observation.<br />( barring refraction/reflection) so if the space in which the partical of light is traveling is being bent by a black hole or galaxy we can see the path change of the light. The question I have never had answered in the case of black holes is why does the light not reemerge with the space once the black hole passes by. The only answer I got was that black holes do not ever release the space that is bent into it but that makes no sense to me do to the fact that black holes are not stationary. That would mean that there would be a rift in space in the wake of a black whole from point of origin to current position and this has never been observed. As to what happens to the light I assume at some point it hits the mass of the black hole and is then absorbed and not retransmitted in any known form ( Oh wait hawking radiation) . <br /> <br /> As to why they show a cone to represent a black holes effect. That’s just a simple 2D representation of a 3D object you are correct the cone actually extends in all direction it is just difficult to make a graphic representation to reflect this and even harder for the general public to comprehend <br />that is one reason I have a hard time accepting the explanation for GRB’s but that is another topic<br />if I have any of this wrong rest assured some one will correct it <img src="/images/icons/smile.gif" /> <br /><br />Hope this helped <br /> <br />

 

[ianke]

Hello slate,<br /><br />re: "The question I have never had answered in the case of black holes is why does the light not reemerge with the space once the black hole passes by."<br /><br />The only light that is lost is the light that falls into the event horizon. Once the black hole's position is no longer in the way of an object, it is visible again.(not the same photons but the object that emits them becomes visible by emitting more photons) I don't know who told you otherwise, but that is how it works.<img src="/images/icons/wink.gif" /><br /><br />As far as the other part of your question, just think of it the same as the rubber sheet with the bowling ball on it. If the bowling ball roles away so does its effect. I know they say the rubber sheet gets a gravity hole punched in the spacetime rubber sheet, but think of the sheet as self healing. Once the BH moves to another coordinate, space time fills back to be as it was. Does that Help?<br /><br /><br />Ianke <div class="Discussion_UserSignature"> </div>

 

[Slate]

You are correct it was the light lost to the EH I was referring to I did not mean all light bent by a BH was lost thanks for pointing that out. Does that mean that the light is absorbed at the Eh and space passes on by or does the space and there by the light goes all the way till the light hits the mass further inside the EH. ( Yes I know physics brakes down at this point but there is still some form of distance between the EH and what ever makes up the BH ? )<br />

 

[ianke]

Sorry I Edited as you were writing.<br /><br />I believe that the event horizon is the point where light can no longer exit the gravity well. At that point it is just conjecture since we can not see into it, however: I think that the most accepted theory says that it is still a photon. It will remain a photon until it falls into the most extreme environment of the singularity. Then Nobody nows for sure as to its fate. Our physics breaks down at that point. <br /> <div class="Discussion_UserSignature"> </div>

 

[ianke]

Hello retic,<br /><br />Wlecome to S.D.C.<br /><br />As far as the conical shape you refer to, it is a two dimensional representation of what happens to spacetime. The event horizon would be more spherical for a black hole with little or no spin.<br /><br />Look up "Black Holes" on wikipedia for starters. they will usually point to answers for your questions of a general nature. <img src="/images/icons/cool.gif" /><br /><br />Ianke <div class="Discussion_UserSignature"> </div>

 

[Slate]

Re: As far as the other part of your question, just think of it the same as the rubber sheet with the bowling ball on it. If the bowling ball roles away so does its effect. I know they say the rubber sheet gets a gravity hole punched in the spacetime rubber sheet, but think of the sheet as self healing. Once the BH moves to another coordinate, space time fills back to be as it was. Does that Help? <br /><br />Yes that’s the way I have looked at it ( although I really do hate the rubber sheet analysis I know it’s a 2d solution for a 3d problem it just doesn’t do it justice) and I don’t remember what my point was that triggered the post I referred to. It was about 2 years ago ill try to find it. <img src="/images/icons/smile.gif" /> I know good luck right <img src="/images/icons/smile.gif" /> <br />

 

[ianke]

Yes. The rubber sheet thing is at best a somewhat lacking example, but it is the best I can do. Perhaps someone else has a better explaination for gravity warping space time. I gets difficult to speak of a 3D example of what a black hole does. I helps to live in a split level head like me though<img src="/images/icons/laugh.gif" /> <br /><br />Ianke <div class="Discussion_UserSignature"> </div>

 

[ianke]

If you find the referal I would like to see it. Please keep us posted {yuk Yuk!} <div class="Discussion_UserSignature"> </div>

 

[Slate]

re: Yes. The rubber sheet thing is at best a somewhat lacking example, but it is the best I can do. Perhaps someone else has a better explaination for gravity warping space time. I gets difficult to speak of a 3D example of what a black hole does. I helps to live in a split level head like me though <br /><br />I looked for a better one for years then a I saw that toy replica of a bucky ball you pull on it and it expands in all directions you push on it and it contracts. Extend this to space and give infinity in all directions and that’s space/time/mass I like it better then the rubber sheet anyway <img src="/images/icons/smile.gif" /> BTW I think you helped me understand what happans to the space and photon at the EH. Thanks much thats been bugging me for 2 years now <img src="/images/icons/smile.gif" /> <br /> <br />

 

[ianke]

Glad to help. You might keep checking the thread though. Someone more knowledgeable than I may correct me or add to it to make a clearer picture for you.<img src="/images/icons/wink.gif" /><br /><br />Ianke<br /> <div class="Discussion_UserSignature"> </div>

 

[sad_freak]

hold up!! <br /><br />photons do have a small mass don't they? after all matter is made of energy so it stands to reason that photons do have mass. since E=mc^2 remeber. so matter can become energy and energy can become matter. so a photon could be pulled into the BH if the escape velocity was bigger than the photon's velocity (c).<br /><br />and the escape velocity is bigger than that once the BH become smaller than the event horizin.

 

[sad_freak]

just to prove that photons have mass:<br /><br />take a photon with a wavelngth of 500nm<br />(i'm using w for wavenlngth in sted of lamda)<br /><br />v=fw<br />3e8=f x 5e(-7)<br />f = 6e14 Hz<br /><br />engergy of a photon = hf<br />E = 6.63e(-34) x 6e14<br />E = 3.978e(-19) J<br /><br />so.... the mass of a photon is:<br /><br />e = mc^2<br />3.978e(-19) = m x 9e16<br />mass of photon = 4.43e(-36) kg<br /><br />i think that's right.

 

[retic]

Great stuff guys and gals thanks for the Info, I did look up black holes and the info was kinda vague or they assume you know to much <img src="/images/icons/smile.gif" />, I have a huge amount of trouble visualizing space flat but that is neither here nor there, I have to think in 3d and 4d all day so....<br />Ok, Photons have mass, hmmm so they can't exist in normal space otherwise they wouldn't move at C, would they ?, maybe em is just a leak over from whatever dimension they are in. I know science types current hypotheses the existence of such dimensions.<br /> ooh dimensional boring engines that way you don't have to reach light speed you just bypass the space you don't need to travel through. no chance of collisions ect as long as you pop back into 3d at the appropriate place. going to research dimensions again thanks for the info.

 

[docm]

When discussing the mass of a particle you're defining its <i>invariant</i>, or rest, mass. This because any motion increases mass according to M=E/C^2 (derivation of E=MC^2), masking the rest value. <br /><br />This invariant mass is an <i>observer independent value</i>.<br /><br />Photons don't have an invariant mass but a <i>relativistic </i>(apparent) mass which depends on the frame of reference of an observer. As such it's "mass" is an observer <i>dependent</i> value.<br /><br />Apples & oranges. <div class="Discussion_UserSignature"> </div>

 

[vandivx]

<blockquote><font class="small">In reply to:</font><hr /><p>As to why they show a cone to represent a black holes effect. That’s just a simple 2D representation of a 3D object you are correct the cone actually extends in all direction it is just difficult to make a graphic representation to reflect this and even harder for the general public to comprehend<p><hr /></p></p></blockquote><br /><br />it is not 'difficult to make a graphic representation', rather it is impossible<br /><br />don't be smug in thinking scientists can comprehend that (never mind the joe public), they just play that game 'the king has new clothes' and that's all there is to it<br /><br />to see that though, you have to think as children do and that adults are extremely rarely able to do, alas<br /><br />vanDivX<br /><br /> <div class="Discussion_UserSignature"> </div>

 

[nova_explored]

More on that: exert from Wikipedia.com<br /><br />"Although the photon is itself massless, it adds to the invariant mass of any system to which it belongs; this is true for every form of energy, as predicted by the special theory of relativity. For example, the invariant mass of a system that emits a photon is decreased by an amount E / c2 upon emission, where E is the energy of the photon in the frame of the emitting system. Similarly, the invariant mass of a system that absorbs a photon is increased by a corresponding amount based on the energy of the photon in the frame of the absorbing system.<br />This concept is applied in a key prediction of QED, the theory of quantum electrodynamics begun by Dirac (described above). QED is able to predict the magnetic dipole moment of leptons to extremely high accuracy; experimental measurements of these magnetic dipole moments have agreed with these predictions perfectly. The predictions, however, require counting the contributions of virtual photons to the invariant mass of the lepton. Another example of such contributions verified experimentally is the QED prediction of the Lamb shift observed in the hyperfine structure of bound lepton pairs, such as muonium and positronium.<br />Since photons contribute to the stress-energy tensor, they exert a gravitational attraction on other objects, according to the theory of general relativity. Conversely, photons are themselves affected by gravity; their normally straight trajectories may be bent by warped spacetime, as in gravitational lensing, and their frequencies may be lowered by moving to a higher gravitational potential, as in the Pound-Rebka experiment. However, these effects are not specific to photons; exactly the same effects would be predicted for classical electromagnetic waves."<br /><br />This also explains equations for determining mass of a system involving a photon. <div class="Discussion_UserSignature"> </div>

 

[Slate]

Ok you guys have me reaching for the Advil now all these years I’ve been told that it was the 0 rest mass that mattered and was why gravity could not pull on a photon directly. Now your saying that do to the relativistic mass carried by the photon, gravity can effect it directly not just by bending the space it travels through. Ok I get that and it does make sense from that one point of view but now lets add that back to E=M/C2. Energy ( relativistic or not ) = mass and mass no matter how small can not travel at C yet C is based on the velocity of a photon thru a vacuum and the photon has mass. Im so confused now <br /><br />Another problem is that under this view a photons path can be altered by gravity that means any gravity no matter how small has an effect. Now this is no big deal If Im pointing a flash light at you from across the street. However if Im viewing a star or galaxy at a distance of 14 billion LY<br />those little photons have encountered a hole lot of gravity in their path and that would mean they have not traveled in a strait line. This calls into question the actual distance from point of origin to point of observation. Not only do you have a problem of actual distance you should also see stars and whole galaxies winking out of sight as gravity totally changes the photons trajectory and there by there final destination. There should even be photons in orbit of massive objects. I would imagine even between galaxies. Ok there is a whole lot more here to ask about but this is enough for now. My little brain will only be able to take so much in <img src="/images/icons/smile.gif" />

 

[sad_freak]

so since light always trvels in a stright line, the photons take a stright route in a curved space? <br /><br />so photons are drawn into a BH?<br /><br />i was always cnfused because of the event horizin, since it always says light cannot get higher than the escape velocity. i assumed this ment light was pulled in.

 

[chesh]

"So since light always trvels in a stright line, the photons take a stright route in a curved space? so photons are drawn into a BH?"<br /><br />As many might guess, it's rather more complicated than that. A photon takes the least energy route, which in normal space with minimal large gravitational fields is a straight line. When it encounters a gravitational field like a star, for instance, then the space time fields are bent and the light beam travels along those curves in a least energy route, which is no longer a "straight line", but a curve. Once past there, it then goes back to a virtual, relatively straight line.<br /><br />Straight lines on the earth, BTW are defined by a beam of line travelling in an uninterrupted direction. That is the straightest line one can find.<br /><br />Photons are NOT drawn into a black hole like mass is. Photons have no real mass and so they do not gravitate towards mass. Events with mass, such as electrons, protons, even neutrinos would be drawn towards the Black Hole as a function of their total mass, the strength of the gravitationsl field around the black hole and the velocity of the mass.<br /><br />Photons are NOT drawn into a black hole, such as happens with masses. Photon have no mass. They have momenta, but are massless. <br /><br />So, to demonstrate this, if a photon and a mass were moving in the exact same trajectory, the photon would only move towards the black hole according to a relativistic bend in the gravitational field. and the mass would diverge substantially more because of its mass. Photons and masses do NOT behave the same in a gravitational field.<br /><br />IN an even more delicate differentiation of this process, cosmic rays are mostly Fe atoms travelling near light speed. if a photon and a Fe atom cosmic ray entered an large gravitational field very near to a black hole, the cosmic ray's path would diverge more than the photon's path, due to the mass difference between mass and photon.<br /><br />It would be slight bu

 

[alokmohan]

A very nice reply.Where you hided?Not in a black hole is suppose?

 

[lukman]

That case, i believe photon is not traveling at C, maybe around 0.999999999999999999999999999999999C. because something at C will be eternity and invisible, can occupy anypoint in the universe at anytime. Perhaps the C Constantr is only a small fraction faster than speed of light. <div class="Discussion_UserSignature"> </div>