Hcfyk

Install LibreOffice-Writer Only not LibreOffice whole package

Snap victim memorial reference in Avengers: Endgame

What was Bran's plan to kill the Night King?

Why would a military not separate its forces into different branches?

Gerrymandering Puzzle - Rig the Election

Should I mention being denied entry to UK due to a confusion in my Visa and Ticket bookings?

As a GM, is it bad form to ask for a moment to think when improvising?

Should homeowners insurance cover the cost of the home?

Would you use "llamarse" for an animal's name?

Why aren't nationalizations in Russia described as socialist?

Will 700 more planes a day fly because of the Heathrow expansion?

Where to draw the line between quantum mechanics theory and its interpretation(s)?

Start job from another SQL server instance

Handling Null values (and equivalents) routinely in Python

Out of scope work duties and resignation

Is Benjen dead?

Is “snitty” a popular American English term? What is its origin?

How do I calculate how many of an item I'll have in this inventory system?

Why is my arithmetic with a long long int behaving this way?

Do I add modifiers to the Charisma check roll of 15 granted by the Glibness spell?

Correct way of drawing empty, half-filled and fully filled circles?

Definition of conditional probability and a problem.

Removing racism on a multi raced world

Why do people keep telling me that I am a bad photographer?

If a black hole is created from light, can this black hole then move at the speed of light?

Will free-fall object into black hole exceed speed of light $c$ before hitting black hole surface?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 escape a black hole?Can a High Enough Temperature Create a Black Hole?can light go faster than light speed?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

23

3

$begingroup$

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 black hole then move at the speed of light?

black-holes mass speed-of-light mass-energy speed

share|cite|improve this question

edited Mar 30 at 8:07

Peter Mortensen

1,96111424

asked Mar 29 at 11:00

user6760user6760

3,18112146

$endgroup$

add a comment | 

23

3

$begingroup$

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 black hole then move at the speed of light?

black-holes mass speed-of-light mass-energy speed

share|cite|improve this question

edited Mar 30 at 8:07

Peter Mortensen

1,96111424

asked Mar 29 at 11:00

user6760user6760

3,18112146

$endgroup$

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 black hole then move at the speed of light?

black-holes mass speed-of-light mass-energy speed

share|cite|improve this question

edited Mar 30 at 8:07

Peter Mortensen

1,96111424

asked Mar 29 at 11:00

user6760user6760

3,18112146

$endgroup$

share|cite|improve this question

edited Mar 30 at 8:07

Peter Mortensen

1,96111424

asked Mar 29 at 11:00

user6760user6760

3,18112146

share|cite|improve this question

edited Mar 30 at 8:07

Peter Mortensen

1,96111424

asked Mar 29 at 11:00

user6760user6760

3,18112146

edited Mar 30 at 8:07

Peter Mortensen

1,96111424

edited Mar 30 at 8:07

Peter Mortensen

1,96111424

asked Mar 29 at 11:00

user6760user6760

3,18112146

asked Mar 29 at 11:00

user6760user6760

3,18112146

2 Answers
2

active

oldest

votes

30

$begingroup$

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.

share|cite|improve this answer

answered Mar 29 at 12:17

John RennieJohn Rennie

281k45565812

$endgroup$

• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  Comments are not for extended discussion; this conversation has been moved to chat.
  $endgroup$
  – ACuriousMind♦
  Mar 29 at 22:23
  

  
  
  
  

add a comment | 

9

$begingroup$

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.

share|cite|improve this answer

answered Mar 29 at 11:19

PM 2RingPM 2Ring

3,70821225

$endgroup$

• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  '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
  Mar 29 at 22:10
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  Lightspeed - qualify by being in vacuum (I am thinking of Cherenkov radiation)?
  $endgroup$
  – Peter Mortensen
  Mar 30 at 3:23
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  @Mazura Yes, the black hole formed from photons has mass, but that doesn't necessarily mean that the photons produced matter. See chat.stackexchange.com/transcript/message/49710715#49710715
  $endgroup$
  – PM 2Ring
  Mar 30 at 10:49
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  @Peter Yes, by "lightspeed" I mean c, the speed of light in a perfect vacuum, 299792458 m/s.
  $endgroup$
  – PM 2Ring
  Mar 30 at 11:06
  

  
  
  
  

add a comment | 

Your Answer

StackExchange.ready(function()
var channelOptions =
tags: "".split(" "),
id: "151"
;
initTagRenderer("".split(" "), "".split(" "), channelOptions);

StackExchange.using("externalEditor", function()
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled)
StackExchange.using("snippets", function()
createEditor();
);

else
createEditor();

);

function createEditor()
StackExchange.prepareEditor(
heartbeatType: 'answer',
autoActivateHeartbeat: false,
convertImagesToLinks: false,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: null,
bindNavPrevention: true,
postfix: "",
imageUploader:
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
,
noCode: true, onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
);



);

draft saved

draft discarded

Sign up or log in

StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);

Sign up using Google

Sign up using Facebook

Sign up using Email and Password

Post as a guest

Name

Email

Required, but never shown

StackExchange.ready(
function ()
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fphysics.stackexchange.com%2fquestions%2f469345%2fif-a-black-hole-is-created-from-light-can-this-black-hole-then-move-at-the-spee%23new-answer', 'question_page');

);

Post as a guest

Name

Email

Required, but never shown

30

$begingroup$

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.

share|cite|improve this answer

answered Mar 29 at 12:17

John RennieJohn Rennie

281k45565812

$endgroup$

• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  Comments are not for extended discussion; this conversation has been moved to chat.
  $endgroup$
  – ACuriousMind♦
  Mar 29 at 22:23
  

  
  
  
  

add a comment | 

30

$begingroup$

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.

share|cite|improve this answer

answered Mar 29 at 12:17

John RennieJohn Rennie

281k45565812

$endgroup$

• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  Comments are not for extended discussion; this conversation has been moved to chat.
  $endgroup$
  – ACuriousMind♦
  Mar 29 at 22:23
  

  
  
  
  

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.

share|cite|improve this answer

answered Mar 29 at 12:17

John RennieJohn Rennie

281k45565812

$endgroup$

share|cite|improve this answer

answered Mar 29 at 12:17

John RennieJohn Rennie

281k45565812

answered Mar 29 at 12:17

John RennieJohn Rennie

281k45565812

answered Mar 29 at 12:17

John RennieJohn Rennie

281k45565812

9

$begingroup$

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.

share|cite|improve this answer

answered Mar 29 at 11:19

PM 2RingPM 2Ring

3,70821225

$endgroup$

• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  '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
  Mar 29 at 22:10
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  Lightspeed - qualify by being in vacuum (I am thinking of Cherenkov radiation)?
  $endgroup$
  – Peter Mortensen
  Mar 30 at 3:23
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  @Mazura Yes, the black hole formed from photons has mass, but that doesn't necessarily mean that the photons produced matter. See chat.stackexchange.com/transcript/message/49710715#49710715
  $endgroup$
  – PM 2Ring
  Mar 30 at 10:49
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  @Peter Yes, by "lightspeed" I mean c, the speed of light in a perfect vacuum, 299792458 m/s.
  $endgroup$
  – PM 2Ring
  Mar 30 at 11:06
  

  
  
  
  

add a comment | 

9

$begingroup$

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.

share|cite|improve this answer

answered Mar 29 at 11:19

PM 2RingPM 2Ring

3,70821225

$endgroup$

• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  '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
  Mar 29 at 22:10
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  Lightspeed - qualify by being in vacuum (I am thinking of Cherenkov radiation)?
  $endgroup$
  – Peter Mortensen
  Mar 30 at 3:23
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  @Mazura Yes, the black hole formed from photons has mass, but that doesn't necessarily mean that the photons produced matter. See chat.stackexchange.com/transcript/message/49710715#49710715
  $endgroup$
  – PM 2Ring
  Mar 30 at 10:49
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  @Peter Yes, by "lightspeed" I mean c, the speed of light in a perfect vacuum, 299792458 m/s.
  $endgroup$
  – PM 2Ring
  Mar 30 at 11:06
  

  
  
  
  

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.

share|cite|improve this answer

answered Mar 29 at 11:19

PM 2RingPM 2Ring

3,70821225

$endgroup$

share|cite|improve this answer

answered Mar 29 at 11:19

PM 2RingPM 2Ring

3,70821225

answered Mar 29 at 11:19

PM 2RingPM 2Ring

3,70821225

answered Mar 29 at 11:19

PM 2RingPM 2Ring

3,70821225