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If a black hole is created from light, can this black hole then move at speed of light?
The Next CEO of Stack OverflowWill free-fall object into black hole exceed speed of light $c$ before hitting black hole surface?Entropy of a black hole can be zero?Speed of light originating from a star with gravitational pull close to black-hole strength?How can a black hole reduce the speed of light?If you shine a light away from the center of a Schwarzchild black hole, will it stay still?Can a black hole move at speed of light?can light go faster than light speed?Does a black hole move through space? What happens to other things around it?If photons don't experience time then why can't they escape a black hole?if light is the fastest 'thing' then why can it not escape the pull of a black hole
$begingroup$
Imagine we managed to squeeze light into a very tiny region of space so that the energy concentration at that point becomes a black hole, can this blackhole then move at speed of light?
black-holes mass speed-of-light mass-energy speed
edited 12 hours ago
Qmechanic♦
107k121981229
asked 18 hours ago
user6760user6760
2,94212044
$endgroup$
add a comment |
$begingroup$
Imagine we managed to squeeze light into a very tiny region of space so that the energy concentration at that point becomes a black hole, can this blackhole then move at speed of light?
black-holes mass speed-of-light mass-energy speed
edited 12 hours ago
Qmechanic♦
107k121981229
asked 18 hours ago
user6760user6760
2,94212044
$endgroup$
add a comment |
$begingroup$
Imagine we managed to squeeze light into a very tiny region of space so that the energy concentration at that point becomes a black hole, can this blackhole then move at speed of light?
black-holes mass speed-of-light mass-energy speed
edited 12 hours ago
Qmechanic♦
107k121981229
asked 18 hours ago
user6760user6760
2,94212044
$endgroup$
Imagine we managed to squeeze light into a very tiny region of space so that the energy concentration at that point becomes a black hole, can this blackhole then move at speed of light?
black-holes mass speed-of-light mass-energy speed
black-holes mass speed-of-light mass-energy speed
edited 12 hours ago
Qmechanic♦
107k121981229
asked 18 hours ago
user6760user6760
2,94212044
edited 12 hours ago
Qmechanic♦
107k121981229
asked 18 hours ago
user6760user6760
2,94212044
edited 12 hours ago
Qmechanic♦
107k121981229
edited 12 hours ago
Qmechanic♦
107k121981229
edited 12 hours ago
Qmechanic♦
107k121981229
107k121981229
asked 18 hours ago
user6760user6760
2,94212044
asked 18 hours ago
user6760user6760
2,94212044
asked 18 hours ago
user6760user6760
2,94212044
2,94212044
add a comment |
add a comment |
2 Answers
2
active
oldest
votes
$begingroup$
No. I assume you're thinking that a black hole made from light would have a zero rest mass and could therefore travel at the speed of light. However the rest mass of any black hole is due not only to the mass that went into it but also the energy (e.g. photons) that went into it. The increase in mass due to the energy is given by Einstein's famous equation $E = mc^2$.
So if we create the black hole from purely mass $m$ the rest mass of the black hole is just $m$.
If we create the black hole from purely energy $E$, e.g. from photons with a total energy $E$, then the rest mass of the black hole is $E/c^2$.
Or for completeness we could use a mixture of mass $m$ and energy $E$ in which case the rest mass would be $m + E/c^2$.
So a black hole made from just photons would not have a zero rest mass and therefore could not travel at the speed of light.
This conversion of photons to a mass isn't unique to a black hole. For example suppose we start with a hydrogen atom in the ground state, $1s$, and let it absorb a 10.2eV photon to excite it to the $2p$ state. This would increase the mass by $10.2textrmeV/c^2$ i.e. even though the photon is massless absorbing it increases the mass of the hydrogen atom. As a general rule mass is not a conserved quantity either in special or general relativity.
answered 17 hours ago
John RennieJohn Rennie
279k44556804
$endgroup$
$begingroup$
Comments are not for extended discussion; this conversation has been moved to chat.
$endgroup$
– ACuriousMind♦
7 hours ago
$begingroup$
Could you make a black hole out of photons in the first place? I recall seeing the claim that photons don't exert gravitational force on each other.
$endgroup$
– Acccumulation
6 hours ago
$begingroup$
@Acccumulation See second answer...
$endgroup$
– Mithoron
4 hours ago
$begingroup$
@Mithoron I don't see an anwer to Acccumulation's question.
$endgroup$
– onurcanbektas
3 hours ago
$begingroup$
@Acccumulation yes, a black hole made from photons is called a kugelblitz
$endgroup$
– John Rennie
25 mins ago
add a comment |
$begingroup$
No. Nothing with non-zero mass can move at lightspeed. A kugelblitz would behave just like a more conventional black hole formed from matter, due to the no-hair theorem.
answered 18 hours ago
PM 2RingPM 2Ring
3,1232922
$endgroup$
$begingroup$
'formed directly from matter'. If it's a black hole it has mass. If it has mass that means the photons collided and became electrons and positrons. = no lightspeed :(
$endgroup$
– Mazura
7 hours ago
$begingroup$
Lightspeed - qualify by being in vacuum (I am thinking of Cherenkov radiation)?
$endgroup$
– Peter Mortensen
2 hours ago
add a comment |
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
$begingroup$
No. I assume you're thinking that a black hole made from light would have a zero rest mass and could therefore travel at the speed of light. However the rest mass of any black hole is due not only to the mass that went into it but also the energy (e.g. photons) that went into it. The increase in mass due to the energy is given by Einstein's famous equation $E = mc^2$.
So if we create the black hole from purely mass $m$ the rest mass of the black hole is just $m$.
If we create the black hole from purely energy $E$, e.g. from photons with a total energy $E$, then the rest mass of the black hole is $E/c^2$.
Or for completeness we could use a mixture of mass $m$ and energy $E$ in which case the rest mass would be $m + E/c^2$.
So a black hole made from just photons would not have a zero rest mass and therefore could not travel at the speed of light.
This conversion of photons to a mass isn't unique to a black hole. For example suppose we start with a hydrogen atom in the ground state, $1s$, and let it absorb a 10.2eV photon to excite it to the $2p$ state. This would increase the mass by $10.2textrmeV/c^2$ i.e. even though the photon is massless absorbing it increases the mass of the hydrogen atom. As a general rule mass is not a conserved quantity either in special or general relativity.
answered 17 hours ago
John RennieJohn Rennie
279k44556804
$endgroup$
$begingroup$
Comments are not for extended discussion; this conversation has been moved to chat.
$endgroup$
– ACuriousMind♦
7 hours ago
$begingroup$
Could you make a black hole out of photons in the first place? I recall seeing the claim that photons don't exert gravitational force on each other.
$endgroup$
– Acccumulation
6 hours ago
$begingroup$
@Acccumulation See second answer...
$endgroup$
– Mithoron
4 hours ago
$begingroup$
@Mithoron I don't see an anwer to Acccumulation's question.
$endgroup$
– onurcanbektas
3 hours ago
$begingroup$
@Acccumulation yes, a black hole made from photons is called a kugelblitz
$endgroup$
– John Rennie
25 mins ago
add a comment |
$begingroup$
No. I assume you're thinking that a black hole made from light would have a zero rest mass and could therefore travel at the speed of light. However the rest mass of any black hole is due not only to the mass that went into it but also the energy (e.g. photons) that went into it. The increase in mass due to the energy is given by Einstein's famous equation $E = mc^2$.
So if we create the black hole from purely mass $m$ the rest mass of the black hole is just $m$.
If we create the black hole from purely energy $E$, e.g. from photons with a total energy $E$, then the rest mass of the black hole is $E/c^2$.
Or for completeness we could use a mixture of mass $m$ and energy $E$ in which case the rest mass would be $m + E/c^2$.
So a black hole made from just photons would not have a zero rest mass and therefore could not travel at the speed of light.
This conversion of photons to a mass isn't unique to a black hole. For example suppose we start with a hydrogen atom in the ground state, $1s$, and let it absorb a 10.2eV photon to excite it to the $2p$ state. This would increase the mass by $10.2textrmeV/c^2$ i.e. even though the photon is massless absorbing it increases the mass of the hydrogen atom. As a general rule mass is not a conserved quantity either in special or general relativity.
answered 17 hours ago
John RennieJohn Rennie
279k44556804
$endgroup$
$begingroup$
Comments are not for extended discussion; this conversation has been moved to chat.
$endgroup$
– ACuriousMind♦
7 hours ago
$begingroup$
Could you make a black hole out of photons in the first place? I recall seeing the claim that photons don't exert gravitational force on each other.
$endgroup$
– Acccumulation
6 hours ago
$begingroup$
@Acccumulation See second answer...
$endgroup$
– Mithoron
4 hours ago
$begingroup$
@Mithoron I don't see an anwer to Acccumulation's question.
$endgroup$
– onurcanbektas
3 hours ago
$begingroup$
@Acccumulation yes, a black hole made from photons is called a kugelblitz
$endgroup$
– John Rennie
25 mins ago
add a comment |
$begingroup$
No. I assume you're thinking that a black hole made from light would have a zero rest mass and could therefore travel at the speed of light. However the rest mass of any black hole is due not only to the mass that went into it but also the energy (e.g. photons) that went into it. The increase in mass due to the energy is given by Einstein's famous equation $E = mc^2$.
So if we create the black hole from purely mass $m$ the rest mass of the black hole is just $m$.
If we create the black hole from purely energy $E$, e.g. from photons with a total energy $E$, then the rest mass of the black hole is $E/c^2$.
Or for completeness we could use a mixture of mass $m$ and energy $E$ in which case the rest mass would be $m + E/c^2$.
So a black hole made from just photons would not have a zero rest mass and therefore could not travel at the speed of light.
This conversion of photons to a mass isn't unique to a black hole. For example suppose we start with a hydrogen atom in the ground state, $1s$, and let it absorb a 10.2eV photon to excite it to the $2p$ state. This would increase the mass by $10.2textrmeV/c^2$ i.e. even though the photon is massless absorbing it increases the mass of the hydrogen atom. As a general rule mass is not a conserved quantity either in special or general relativity.
answered 17 hours ago
John RennieJohn Rennie
279k44556804
$endgroup$
No. I assume you're thinking that a black hole made from light would have a zero rest mass and could therefore travel at the speed of light. However the rest mass of any black hole is due not only to the mass that went into it but also the energy (e.g. photons) that went into it. The increase in mass due to the energy is given by Einstein's famous equation $E = mc^2$.
So if we create the black hole from purely mass $m$ the rest mass of the black hole is just $m$.
If we create the black hole from purely energy $E$, e.g. from photons with a total energy $E$, then the rest mass of the black hole is $E/c^2$.
Or for completeness we could use a mixture of mass $m$ and energy $E$ in which case the rest mass would be $m + E/c^2$.
So a black hole made from just photons would not have a zero rest mass and therefore could not travel at the speed of light.
This conversion of photons to a mass isn't unique to a black hole. For example suppose we start with a hydrogen atom in the ground state, $1s$, and let it absorb a 10.2eV photon to excite it to the $2p$ state. This would increase the mass by $10.2textrmeV/c^2$ i.e. even though the photon is massless absorbing it increases the mass of the hydrogen atom. As a general rule mass is not a conserved quantity either in special or general relativity.
answered 17 hours ago
John RennieJohn Rennie
279k44556804
answered 17 hours ago
John RennieJohn Rennie
279k44556804
answered 17 hours ago
John RennieJohn Rennie
279k44556804
answered 17 hours ago
John RennieJohn Rennie
279k44556804
279k44556804
$begingroup$
Comments are not for extended discussion; this conversation has been moved to chat.
$endgroup$
– ACuriousMind♦
7 hours ago
$begingroup$
Could you make a black hole out of photons in the first place? I recall seeing the claim that photons don't exert gravitational force on each other.
$endgroup$
– Acccumulation
6 hours ago
$begingroup$
@Acccumulation See second answer...
$endgroup$
– Mithoron
4 hours ago
$begingroup$
@Mithoron I don't see an anwer to Acccumulation's question.
$endgroup$
– onurcanbektas
3 hours ago
$begingroup$
@Acccumulation yes, a black hole made from photons is called a kugelblitz
$endgroup$
– John Rennie
25 mins ago
add a comment |
$begingroup$
Comments are not for extended discussion; this conversation has been moved to chat.
$endgroup$
– ACuriousMind♦
7 hours ago
$begingroup$
Could you make a black hole out of photons in the first place? I recall seeing the claim that photons don't exert gravitational force on each other.
$endgroup$
– Acccumulation
6 hours ago
$begingroup$
@Acccumulation See second answer...
$endgroup$
– Mithoron
4 hours ago
$begingroup$
@Mithoron I don't see an anwer to Acccumulation's question.
$endgroup$
– onurcanbektas
3 hours ago
$begingroup$
@Acccumulation yes, a black hole made from photons is called a kugelblitz
$endgroup$
– John Rennie
25 mins ago
$begingroup$
Comments are not for extended discussion; this conversation has been moved to chat.
$endgroup$
– ACuriousMind♦
7 hours ago
$begingroup$
Comments are not for extended discussion; this conversation has been moved to chat.
$endgroup$
– ACuriousMind♦
7 hours ago
$begingroup$
Could you make a black hole out of photons in the first place? I recall seeing the claim that photons don't exert gravitational force on each other.
$endgroup$
– Acccumulation
6 hours ago
$begingroup$
Could you make a black hole out of photons in the first place? I recall seeing the claim that photons don't exert gravitational force on each other.
$endgroup$
– Acccumulation
6 hours ago
$begingroup$
@Acccumulation See second answer...
$endgroup$
– Mithoron
4 hours ago
$begingroup$
@Acccumulation See second answer...
$endgroup$
– Mithoron
4 hours ago
$begingroup$
@Mithoron I don't see an anwer to Acccumulation's question.
$endgroup$
– onurcanbektas
3 hours ago
$begingroup$
@Mithoron I don't see an anwer to Acccumulation's question.
$endgroup$
– onurcanbektas
3 hours ago
$begingroup$
@Acccumulation yes, a black hole made from photons is called a kugelblitz
$endgroup$
– John Rennie
25 mins ago
$begingroup$
@Acccumulation yes, a black hole made from photons is called a kugelblitz
$endgroup$
– John Rennie
25 mins ago
add a comment |
$begingroup$
No. Nothing with non-zero mass can move at lightspeed. A kugelblitz would behave just like a more conventional black hole formed from matter, due to the no-hair theorem.
answered 18 hours ago
PM 2RingPM 2Ring
3,1232922
$endgroup$
$begingroup$
'formed directly from matter'. If it's a black hole it has mass. If it has mass that means the photons collided and became electrons and positrons. = no lightspeed :(
$endgroup$
– Mazura
7 hours ago
$begingroup$
Lightspeed - qualify by being in vacuum (I am thinking of Cherenkov radiation)?
$endgroup$
– Peter Mortensen
2 hours ago
add a comment |
$begingroup$
No. Nothing with non-zero mass can move at lightspeed. A kugelblitz would behave just like a more conventional black hole formed from matter, due to the no-hair theorem.
answered 18 hours ago
PM 2RingPM 2Ring
3,1232922
$endgroup$
$begingroup$
'formed directly from matter'. If it's a black hole it has mass. If it has mass that means the photons collided and became electrons and positrons. = no lightspeed :(
$endgroup$
– Mazura
7 hours ago
$begingroup$
Lightspeed - qualify by being in vacuum (I am thinking of Cherenkov radiation)?
$endgroup$
– Peter Mortensen
2 hours ago
add a comment |
$begingroup$
No. Nothing with non-zero mass can move at lightspeed. A kugelblitz would behave just like a more conventional black hole formed from matter, due to the no-hair theorem.
answered 18 hours ago
PM 2RingPM 2Ring
3,1232922
$endgroup$
No. Nothing with non-zero mass can move at lightspeed. A kugelblitz would behave just like a more conventional black hole formed from matter, due to the no-hair theorem.
answered 18 hours ago
PM 2RingPM 2Ring
3,1232922
answered 18 hours ago
PM 2RingPM 2Ring
3,1232922
answered 18 hours ago
PM 2RingPM 2Ring
3,1232922
answered 18 hours ago
PM 2RingPM 2Ring
3,1232922
3,1232922
$begingroup$
'formed directly from matter'. If it's a black hole it has mass. If it has mass that means the photons collided and became electrons and positrons. = no lightspeed :(
$endgroup$
– Mazura
7 hours ago
$begingroup$
Lightspeed - qualify by being in vacuum (I am thinking of Cherenkov radiation)?
$endgroup$
– Peter Mortensen
2 hours ago
add a comment |
$begingroup$
'formed directly from matter'. If it's a black hole it has mass. If it has mass that means the photons collided and became electrons and positrons. = no lightspeed :(
$endgroup$
– Mazura
7 hours ago
$begingroup$
Lightspeed - qualify by being in vacuum (I am thinking of Cherenkov radiation)?
$endgroup$
– Peter Mortensen
2 hours ago
$begingroup$
'formed directly from matter'. If it's a black hole it has mass. If it has mass that means the photons collided and became electrons and positrons. = no lightspeed :(
$endgroup$
– Mazura
7 hours ago
$begingroup$
'formed directly from matter'. If it's a black hole it has mass. If it has mass that means the photons collided and became electrons and positrons. = no lightspeed :(
$endgroup$
– Mazura
7 hours ago
$begingroup$
Lightspeed - qualify by being in vacuum (I am thinking of Cherenkov radiation)?
$endgroup$
– Peter Mortensen
2 hours ago
$begingroup$
Lightspeed - qualify by being in vacuum (I am thinking of Cherenkov radiation)?
$endgroup$
– Peter Mortensen
2 hours ago
add a comment |
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