questionposter Posted November 15, 2011 Posted November 15, 2011 But how can even the most extreme gravity affect something that has no mass? And according to Professor Stephen Hawking, even a black hole is not truly black so it must emit something. Well, I guess we can't answer "why" to a great extent but there are experiments that prove it. The best bet is that light follows the curves in the fabric of space too. Why this happens isn't answered right now.
morgsboi Posted November 15, 2011 Author Posted November 15, 2011 Well, I guess we can't answer "why" to a great extent but there are experiments that prove it. The best bet is that light follows the curves in the fabric of space too. Why this happens isn't answered right now. Ah, I understand. Do you know the proper name for the curves? For research purposes. Thank you
IM Egdall Posted November 15, 2011 Posted November 15, 2011 (edited) Ah, I understand. Do you know the proper name for the curves? For research purposes. Thank you [/quote The path of light (and everything else like planets, comets, etc.) is "bent" in a gravitational field because of the warping of space and the warping of time due to the presence of mass/energy (the source of gravity.) This warping of space and time is called spacetime curvature. Edited November 15, 2011 by IM Egdall
morgsboi Posted November 16, 2011 Author Posted November 16, 2011 [/quote The path of light (and everything else like planets, comets, etc.) is "bent" in a gravitational field because of the warping of space and the warping of time due to the presence of mass/energy (the source of gravity.) This warping of space and time is called spacetime curvature. Okay, thankyou
A Tripolation Posted November 16, 2011 Posted November 16, 2011 (edited) I was under the impression that light didn't escape a black hole because of the fact that it was redshifted out of existence. Is this incorrect? Ah, nevermind. That's just the way that it appears to any observer beyond the event horizon. My mistake. Edited November 16, 2011 by A Tripolation
The time Traveller Posted December 8, 2011 Posted December 8, 2011 Light is not matter, it has no mass, it's primary composition is just energy, and energy is another form of matter and vice versa. Both are effected by the fabric of space and they both effect the fabric of space. Light can't escape from a black hole simply because the gravity of a black hole is too powerful, it creates a gravitational well so steep not even light has enough speed to escape it. As far as scientists can tell, nothing comes back from the event horizon except perhaps whatever the result is of black hole evaporation. Once light passes the event horizon, it doesn't come out. Black holes don't emit optical photons, so they are the color of black. When light passes a large body in the universe the gravity of the said mass causes the light to bend and curve around the mass so in theory the light adjacent to the light that has just curved around the mass will be travelling faster as the curved light has travelled a greater distance so there for one or the other would have had to of travelled at a different speed its not possible for some thing travelling at a constant to cover a greater distance eg the straight line is say 500.000miles and the curved line is 510.1740 miles how can something with the same speed and velocity cover two different distances at the same time and speed QED
RichIsnang Posted March 21, 2012 Posted March 21, 2012 @the time traveller, do you know for a fact that these two light rays will arrive at the same time? If so, just speculation, you may need to look at the 'amount of space' on the curved path, as spacetime is curved by the massive body, space-time is curved round it so i can only imagine that the distance from one end to another may be 510.174 but a meter may be slightly smaller in the hugely curved regions. Einsteins theory of gravity tells us why massless particles like photons effected by gravity, it is not an attraction of the matter as such, it is just spacetime is bent around the matter, and as photons are in our time and space, their paths get curved too. The curvature of space-time at the event horizon will cause all matter and energy to accelerate towards the black hole at the ~3x10^8ms^-2, regardless of if it has mass or not
questionposter Posted March 21, 2012 Posted March 21, 2012 (edited) But how can even the most extreme gravity affect something that has no mass? Because energy and mass are equivalent. In fact, I think photons distort the fabric of space even easier than matter. Both matter and energy responds to distortion in the fabric of space. Edited March 21, 2012 by questionposter
morgsboi Posted March 22, 2012 Author Posted March 22, 2012 Because energy and mass are equivalent. In fact, I think photons distort the fabric of space even easier than matter. Both matter and energy responds to distortion in the fabric of space. Yeah, I actually don't remember making that post. :S if it were possible to see, I wonder what light would look like in a singularity. So what makes you think photons distort the fabric of space easier than matter?
questionposter Posted March 22, 2012 Posted March 22, 2012 (edited) When light passes a large body in the universe the gravity of the said mass causes the light to bend and curve around the mass so in theory the light adjacent to the light that has just curved around the mass will be travelling faster as the curved light has travelled a greater distance so there for one or the other would have had to of travelled at a different speed its not possible for some thing travelling at a constant to cover a greater distance eg the straight line is say 500.000miles and the curved line is 510.1740 miles how can something with the same speed and velocity cover two different distances at the same time and speed QED The speed of light is always constant as far as we can tell, and I think your getting measurements mixed up where they shouldn't be. Prior to measurement or direct interaction with objects, light doesn't "take" two paths, it simply "is" those two paths and an infinitesimal amount of paths in between, and this is due to its wave nature which I think is known as "superposition". After measurement, we measure that the photon's probability has collapsed down to a single interaction point for which it has transferred energy. However, after a photon has been "measured", it doesn't keep going as some point, if it's measured then it pretty much is absorbed in some way and no longer exists as that photon. In fact, I think it's impossible to directly measure a photon without destroying it. Even if an electron jumps right back down to its original energy level, it's still emitting a different photon. So when a photon is altered by the black hole, it's not two individual photons, it's the same entire photon who's probability spans over 3-dimensional changing its shape. Edited March 22, 2012 by questionposter
granpa Posted March 22, 2012 Posted March 22, 2012 the speed of light is constant as measured by a local observer however due to gravitational time dilation it is possible for the speed of light as measured by a distant observer outside the gravity well to be less than c
Spyman Posted March 22, 2012 Posted March 22, 2012 the speed of light is constant as measured by a local observer however due to gravitational time dilation it is possible for the speed of light as measured by a distant observer outside the gravity well to be less than c AFAIK, the gravitational time dilation does NOT have an effect on the measured speed of light for any observers.
granpa Posted March 22, 2012 Posted March 22, 2012 http://en.wikipedia.org/wiki/Gravitational_time_dilation The speed of light in a locale is always equal to c according to the observer who is there. The stationary observer's perspective corresponds to the local proper time. Every infinitesimal region of space time may have its own proper time that corresponds to the gravitational time dilation there, where electromagnetic radiation and matter may be equally affected, since they are made of the same essence (as shown in many tests involving the famous equation E=mc2). Such regions are significant whether or not they are occupied by an observer. A time delay is measured for signals that bend near the Sun, headed towards Venus, and bounce back to Earth along a more or less similar path. There is no violation of the speed of light in this sense, as long as an observer is forced to observe only the photons which intercept the observing faculties and not the ones that go passing by in the depths of more (or even less) gravitational time dilation. If a distant observer is able to track the light in a remote, distant locale which intercepts a time dilated observer nearer to a more massive body, he sees that both the distant light and that distant time dilated observer have a slower proper time clock than other light which is coming nearby him, which intercepts him, at c, like all other light he really can observe. When the other, distant light intercepts the distant observer, it will come at c from the distant observer's perspective
Spyman Posted March 22, 2012 Posted March 22, 2012 (edited) http://en.wikipedia.org/wiki/Gravitational_time_dilation The speed of light in a locale is always equal to c according to the observer who is there. The stationary observer's perspective corresponds to the local proper time. Every infinitesimal region of space time may have its own proper time that corresponds to the gravitational time dilation there, where electromagnetic radiation and matter may be equally affected, since they are made of the same essence (as shown in many tests involving the famous equation E=mc2). Such regions are significant whether or not they are occupied by an observer. A time delay is measured for signals that bend near the Sun, headed towards Venus, and bounce back to Earth along a more or less similar path. There is no violation of the speed of light in this sense, as long as an observer is forced to observe only the photons which intercept the observing faculties and not the ones that go passing by in the depths of more (or even less) gravitational time dilation. If a distant observer is able to track the light in a remote, distant locale which intercepts a time dilated observer nearer to a more massive body, he sees that both the distant light and that distant time dilated observer have a slower proper time clock than other light which is coming nearby him, which intercepts him, at c, like all other light he really can observe. When the other, distant light intercepts the distant observer, it will come at c from the distant observer's perspective I stand corrected, the distant observer can't see the curving of space and therefore the distance covered by light seems shorter for him. Edited March 22, 2012 by Spyman
questionposter Posted March 22, 2012 Posted March 22, 2012 (edited) I stand corrected, the distant observer can't see the curving of space and therefore the distance covered by light seems shorter for him. However, light should still always be measured at "c" because of the Lorentz Transformation "Since relativity postulates that the speed of light is the same for all observers, the Lorentz transformation must preserve the spacetime interval between any two events in Minkowski space." The transformation also sort of demonstrates how you can't even achieve the speed of light, seeing as how events asymtote at the frame-rate of "c" thus making it unachievable. Edited March 22, 2012 by questionposter
Spyman Posted March 23, 2012 Posted March 23, 2012 (edited) However, light should still always be measured at "c" because of the Lorentz Transformation "Since relativity postulates that the speed of light is the same for all observers, the Lorentz transformation must preserve the spacetime interval between any two events in Minkowski space." The transformation also sort of demonstrates how you can't even achieve the speed of light, seeing as how events asymtote at the frame-rate of "c" thus making it unachievable. I don't think you can explain the phenomena in the example provided by The time Traveller in post #31 with Lorentz transformations. The speed of light is c for both observers, but the distant observer is unable to measure the real length along light's curved path inside a gravity field. Edited March 23, 2012 by Spyman
questionposter Posted March 23, 2012 Posted March 23, 2012 I don't think you can explain the phenomena in the example provided by The time Traveller in post #31 with Lorentz transformations. The speed of light is c for both observers, but the distant observer is unable to measure the real length along light's curved path inside a gravity field. So what's the point of saying that if light is still "c" for all observers?
Spyman Posted March 23, 2012 Posted March 23, 2012 So what's the point of saying that if light is still "c" for all observers? To point out that the speed of photons through space are still c for all observers, even if it appears to be slower for some.
Aguirre Posted March 23, 2012 Posted March 23, 2012 To point out that the speed of photons through space are still c for all observers, even if it appears to be slower for some. Don`t forget the eigentime (Eigenzeit) for every Photon that has a eigentime Zero.
Spyman Posted March 23, 2012 Posted March 23, 2012 Don`t forget the eigentime (Eigenzeit) for every Photon that has a eigentime Zero. Sorry, unable to understand that.
Aguirre Posted March 23, 2012 Posted March 23, 2012 To point out that the speed of photons through space are still c for all observers, even if it appears to be slower for some. To explain the constance of the speed of light you have at least find a reason where this constance comes from. Otherwise it comes falling down from heaven. And i think the constant of the speed of light is connected to the Eigenzeit. No more to say at the moment.
questionposter Posted March 23, 2012 Posted March 23, 2012 To explain the constance of the speed of light you have at least find a reason where this constance comes from. Otherwise it comes falling down from heaven. And i think the constant of the speed of light is connected to the Eigenzeit. No more to say at the moment. No it has to do with how the "distance" between you and the photon decreases, like dilation, only it's more to do with the frame-rate of events.
Spyman Posted March 23, 2012 Posted March 23, 2012 To explain the constance of the speed of light you have at least find a reason where this constance comes from. Otherwise it comes falling down from heaven. And i think the constant of the speed of light is connected to the Eigenzeit. No more to say at the moment. I am not trying to explain the constancy of lightspeed, it is an confirmed fact by experimental observation and don't need a reason. Eigenzeit seems to translate from german to "proper time" which is a concept in the theory of relativity and connected to lightspeed. I still don't understand what you are trying to say and how it is related to what I said and the context of current conversation.
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