Silly question about mass, black holes, and energy

oklahoman · Mar 7, 2008

The question is silly, possibly stupid, because it is a hypothetical question about something that will never really happen. It is my understanding that electromagnetic energy has no mass and is not a source for gravitaty.  Maybe this is a misunderstanding, if so, correct me please. It is my understanding that  when matter and  antimatter  come into contact,  electromagnetic energy is created in the form of gamma rays. Question:  If anti matter and matter fell into a black hole and collided beyond the event horizon, would  the black hole retain the mass? Just for fun assume it is a suppermassive black hole with a distant event horizon, with relatively low gravitational attraction at the event horizon.    <div class="Discussion_UserSignature"> </div>

kyle_baron · Mar 7, 2008

It is my understanding that electromagnetic energy has no mass and is not a source for gravitaty.  Concentrated energy has gravity.  That's what is speculated  to be at the singularity of a blackhole, where all traces of matter, are stripped away.

 Maybe this is a misunderstanding, if so, correct me please. It is my understanding that  when matter and  antimatter  come into contact,  electromagnetic energy is created in the form of gamma rays.Yes

 Question:  If anti matter and matter fell into a black hole and collided beyond the event horizon, would  the black hole retain the mass? Your question isn't stated correctly.  The only way the blackhole would lose mass (and energy) is if a virtual  particle pair  becomes real, and one is accelerated away from the event horizon, while the other falls in. <div class="Discussion_UserSignature"> </div>

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oklahoman · Mar 8, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>Concentrated energy has gravity.</DIV>Your answer does not seem credible to me.  What is the difference between "concentrated" energy, and non- concentrated energy?  As I see it, either energy exerts gravitational pull or it does not.  Concentrating it should merely concentrate the effect.I know all about virtual pairs, and that is not what I was asking about.   <div class="Discussion_UserSignature"> </div>

kyle_baron · Mar 8, 2008

Your answer does not seem credible to me.  What is the difference between "concentrated" energy, and non- concentrated energy?  As I see it, either energy exerts gravitational pull or it does not.  Concentrating it should merely concentrate the effect. [sarcasm-on]  Oh No!  My credibility is at stake!  [sarcasm-off] I don't believe that we have the technology to detect the gravitational pull of a single electron, especially when it exists is a cloud of "probability positions".  However, the mass has been calculated indirectly from it's energy and momentum (known as variant mass):http://en.wikipedia.org/wiki/Electron9.109 382 15(45) × 10–31 kg[1]5.485 799 09(27) × 10–4 u1&frasl;1822.888 4843(11) u0.510 998 918(44) MeV/c2

I know all about virtual pairs, and that is not what I was asking about.

Ok, If electrons and postitrons (both real particles differing only by charge) fall into a blackhole beneath the event horizon, they wouldn't anihiliate each other, because there is no space for the particles to "explode in". It would be closer to a fusion type process, IMO.The final result would be an increase in mass (and gravitation) for the blackhole. <div class="Discussion_UserSignature"> </div>

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Mee_n_Mac · Mar 8, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>Ok, If electrons and postitrons (both real particles differing only by charge) fall into a blackhole beneath the event horizon, they wouldn't anihiliate each other, because there is no space for the particles to "explode in". It would be closer to a fusion type process, IMO.The final result would be an increase in mass (and gravitation) for the blackhole. Posted by kyle_baron</DIV> I agree with your final conclusion above but do have a question.  First once the electron and positron cross the SMBH's event horizon they are lost to us.  Should they cross paths and annihilate each other the gamma rays still can't escape.  Thus the SMBH gains mass and retains it IMO. That said I don't understand why there's no "space" for the particles to explode in.  With large enough BHs I thought the gravitational gradient could be sufficiently small so as to not spaghettifi even a person crossing it.  I take this to mean space isn't so warped that there's no space just inside the event horizon of such a BH.  Closer to the singularity itself ... sure. <div class="Discussion_UserSignature"> -----------------------------------------------------Ask not what your Forum Software can do do on you,Ask it to, please for the love of all that's Holy, STOP ! </div>

derekmcd · Mar 8, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>It is my understanding that electromagnetic energy has no mass and is not a source for gravitaty.  Maybe this is a misunderstanding, if so, correct me please. Posted by oklahoman</DIV> E=MC^2.  Energy does indeed have mass.  Take a box lined with mirrors and insert light into it.  It does gain mass as the total energy of the box is increased. So, yes... A black hole would retain the mass of two annihilated particles.  <div class="Discussion_UserSignature"> <div> </div> <div>"If something's hard to do, then it's not worth doing." - Homer Simpson</div> </div>

kyle_baron · Mar 8, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'> I don't understand why there's no "space" for the particles to explode in.  With large enough BHs I thought the gravitational gradient could be sufficiently small so as to not spaghettifi even a person crossing it.  I take this to mean space isn't so warped that there's no space just inside the event horizon of such a BH.  Closer to the singularity itself ... sure. Posted by mee_n_mac</DIV> I've heard that also, but I think it's misleading or incorrect. I found this:http://en.wikipedia.org/wiki/Black_holeThe strength of the tidal force depends on how gravitational attraction changes with distance, rather than on the absolute force being felt. This means that small black holes cause spaghettification while infalling objects are still outside their event horizons whereas objects falling into large, supermassive black holes may not be deformed or otherwise feel excessively large forces before passing the event horizon. But, the excessively large forces occur after (or beneath) the event horizon for a supermassive black hole.  <div class="Discussion_UserSignature"> </div>

derekmcd · Mar 14, 2008

I think using an event horizon when discussing what physically happens to matter as it approaches is irrelevant.  It can be misleading and confusing.The event horizon is not a physical boundary that affects matter when it passes through.  It is simply a description of a point when the escape velocity equals the speed of light.  All that happens to matter when it passes this boundary is the inability to escape the inevitable path to the singularity.The physical effects on matter approaching a singularity are solely dependent on mass and distance from the center of mass.  Same as any other 2 body system (at least until you reach the singularity).  <div class="Discussion_UserSignature"> <div> </div> <div>"If something's hard to do, then it's not worth doing." - Homer Simpson</div> </div>

origin · Mar 14, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'> E=MC^2.  Energy does indeed have mass.  Take a box lined with mirrors and insert light into it.  It does gain mass as the total energy of the box is increased.   Posted by derekmcd</DIV>There is an energy mass equivilancy, but to say that energy has mass is not correct.  If this were true then if enough photons were added to your box the box would weigh more - which is not the case.  Photons have no rest mass.    <div class="Discussion_UserSignature"> </div>

derekmcd · Mar 14, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>"There is an energy mass equivilancy, but to say that energy has mass is not correct.  If this were true then if enough photons were added to your box the box would weigh more - which is not the case.  Photons have no rest mass."   Posted by origin</DIV> I agree that photons have zero rest mass, but they do have energy and momentum (relativistic mass) which is what I was referring to.  The 'M' in Einstein's formula refers to 'relativistic' mass, aka just mass and not to be confused with rest or invariant mass.In reference to the OP's original question, two particles annihilating each other in a closed system (black hole) follow the laws of conservation of both energy and momentum (relativistic mass).IOW, the black hole gains mass whether it be from the 2 particles themselves or the resulting energy of their annihilation.I hope I understand and have explained this properly... maybe someone smarter than me can chime in and clarify.  <div class="Discussion_UserSignature"> <div> </div> <div>"If something's hard to do, then it's not worth doing." - Homer Simpson</div> </div>

thejinxkitten · Mar 15, 2008

Question:  If anti matter and matter fell into a black hole and collided beyond the event horizon, would  the black hole retain the mass? matter and antimatter would consumed each other and it will add to the gravitational pull of the black hole.   <div class="Discussion_UserSignature"> <div style="text-align:center"><img id="f4c1b2ef-0793-4f27-9615-e4e17a5bc441" src="http://sitelife.livescience.com/ver1.0/Content/images/store/4/6/f4c1b2ef-0793-4f27-9615-e4e17a5bc441.Large.gif" alt="blog post photo" /></div> ------------------------------------------------------------------- "there are other worlds than this" Jake Chamber of Dark Tower </div>

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Silly question about mass, black holes, and energy

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