Feedback Wanted Please: Black Holes

[plutocrass]

There were a few other posts regarding black holes in another board. <br /><br />Are the following statements correct: Black holes are areas of extremely strong gravitational fields, so strong that nothing can escape their event horizon. Well, almost. <font color="yellow">Gamma radiation escapes from black holes.</font><br /><br />If they are correct, then please let me know if the following statement is correct: "If you send microwaves into a black hole, they are emitted as gamma radiation, and if you send ultraviolet rays into a black hole, they are also emitted as gamma radiation. <font color="yellow">So many different frequencies of light travel into the black hole but only one higher frequency is emitted back out."</font><br /><br />If the above is correct, is it safe to assume that <font color="yellow">strong gravitational fields speed up the frequency of light? </font><br /><br />If this assumption is correct, would it be possible to state that <font color="yellow">the frequency of the gamma light farther away from the black hole's gravitational field would be relatively lower compared to the gamma light closer to the black hole's gravitational field?</font><br /><br /><font color="yellow">Could gravity's impact on the frequency of light explain the Doppler shift?</font><br /><br />Obviously, as an anonymous submitter, <font color="yellow">I know there is something wrong with the idea</font> but I would like quality, expert feedback to help correct my thought process. <br /><br /><font color="yellow">Thanks in advance for corrections.</font>/safety_wrapper>

 

[CalliArcale]

The gamma rays emitted from black holes actually come from their accretion disks, not the holes themselves. The stuff is moving around so fast it heats up to extraordinary temperatures. There is one other kind of radiation a black hole can produce: Hawking Radiation. Stephen Hawking theorized that as matter-antimatter pairs wander around and eventually annhilate one another, if a pair does this while dancing around the event horizon of a black hole, one of the particles may be trapped by the hole while the other is freed. This process leads to gradual "evaporation" of the black hole. For stellar remnant black holes and the supermassive black holes at the cores of galaxies, this process is too slow to be noticable. But the incredibly tiny black holes produced in laboratories evaporate almost instantly.<br /><br />Note: Doppler shifts are not a result of light speeding up. The frequency increases, but light is still traveling at the same speed. Compare it to Doppler shifts in sound. Sound still travels at the same speed, but the shift changes because the frequency has increased. <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[plutocrass]

Hi CalliArcale, <br /><br />Thanks for the quick response! <br /><br />I did not know was the creation of tiny black holes in laboratories. That's pretty cool!<br /><br />One clarification in something you wrote: "Doppler shifts...<font color="yellow">frequency increases,</font>but light is still traveling at the same speed." I think you inverted here, and meant to write <font color="yellow">frequency decreases</font> I'd also like to include a clarification of my own. When I wrote that Gravity speeds up Light's frequency, I meant that Gravity increases the frequency of Light, the wavelength is shorter. I understand that c remains constant. <font color="yellow">But how could I demonstrate whether or not Gravity affects a lightwave's frequency?</font><br /><br />Beacause my question refers to the Doppler shift. <font color="yellow">Why do we assume Light acts like sound, and not like Light? This is because we know that Gravity affects Light, it does not affect sound. </font><br /><br />I'm wondering this because if Gravity affects Light's frequency, then the lightwave should have a higher frequency at its origin, compared to some point along its path of travel away from its origin. <br /><br />The lightwave should decrease its frequence as it travels away from its gravitational field. The degree of this shift would be dependent on its distance away from its origin. <br /><br /><font color="yellow">Look, I know there's something wrong here, I just don't know what it is. Could you try again to help me figure it out? </font>Actually, this invitation is open to anyone, really.

 

[CalliArcale]

<blockquote><font class="small">In reply to:</font><hr /><p>I think you inverted here, and meant to write frequency decreases. I'd also like to include a clarification of my own. When I wrote that Gravity speeds up Light's frequency, I meant that Gravity increases the frequency of Light, the wavelength is shorter.<p><hr /></p></p></blockquote><br /><br />Frequency increases or decreases; what I should've said is it changes. Frequency decreases for redshift, but increases for blueshift.<br /><br />I understand your question now, though. As far as I know, gravity does not affect the frequency of light. The x-rays and gamma rays emitted around black holes are actually being produced at those frequencies. It's not light going near the black hole and getting fantastically blueshifted. It's light being emitted by stupendously hot plasma in the environs of the black hole. Basically, matter is torn to shreds as it orbits close to the black hole, and this generates a terrific amount of heat. Heat matter up enough and it glows in x-ray.<br /><br />Disclaimer: I am not an expert. I am a software engineer by trade, so if you're doing this for a class project, you're going to want to verify what I've said before running with it. I could well be messing something up. <img src="/images/icons/wink.gif" /> <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[siarad]

Gravity reduces light's frequency, red-shifting.<br />As Calli says the increase is due to re-radiation similar to the greenhouse effect.

 

[plutocrass]

Hi Calli - It looks like we understand each other now. I can't seem to find an experiment where anyone asked the question whether or not light affects gravity. It seems like it's an important answer to know, you know? Is there an online library of physics experiments so I can find out if anyone has tested this? Seems possible, if you had an old laser and a lot of extra Gravity lying around someplace.<br /><br />Siarad, hi! Thanks for your response. You've left me completely baffled, so I will bow to your expertise! Thanks a lot though. Do you happen to know the name of the experiment where they tested whether or not Gravity affected the frequency of light?<br />

 

[yevaud]

Michaleson-Morley did some work in this area. But I believe the actual experiment you're referring to is Ives-Stillwell? (I might be wrong here)<br /><br />Ives Stillwell <div class="Discussion_UserSignature"> <p><em>Differential Diagnosis:  </em>"<strong><em>I am both amused and annoyed that you think I should be less stubborn than you are</em></strong>."<br /> </p> </div>

 

[emperor_of_localgroup]

You are right, frequecny shift by gravitational field can be claimed as 'red shift'. According to a physics text the fomulae, using general relativity, are<br />&%$#@! &%$#@!="redshift.jpg"/><br />Here f_N is new frequency, f_O is original frequency, M=mass of star or blackhole, R=radius of star, G=6.67x10^-11, c=speed of light. <br /><br />From the bottom equation, you can see, as light leaves a strong gravitational field, its frequency decreases - a red shift. Just the opposite for the top formula. <br /><br />It also says, if M/R is very high, huge mass in a small volume, frequency turns negative meaning light can't leave the field. This is why theoretical astrophysicists make me less enthusiastic, they dont throw away any absurd values of a variable. <br /><br />Yes, I also haven't seen any explanation of this red shift in receding galaxy's red shift.<br /> <div class="Discussion_UserSignature"> <font size="2" color="#ff0000"><strong>Earth is Boring</strong></font> </div>

 

[plutocrass]

Ok. but I don't get it. It looks like an alternative explanation for the redshifting, other than receding galaxies. Because as galaxies are farther away, the light would experience an increased redshifting relative to the distance it travelled away from the strong gravitational field. <br /><br /><font color="yellow">There's something obviously wrong here.</font>/safety_wrapper>