Hjdcti

Why are electrically insulating heatsinks so rare? Is it just cost?

Which models of the Boeing 737 are still in production?

What would happen to a modern skyscraper if it rains micro blackholes?

"to be prejudice towards/against someone" vs "to be prejudiced against/towards someone"

Why do I get two different answers for this counting problem?

Pattern match does not work in bash script

Modeling an IP Address

What defenses are there against being summoned by the Gate spell?

Why can't I see bouncing of a switch on an oscilloscope?

What are the differences between the usage of 'it' and 'they'?

Why is consensus so controversial in Britain?

What typically incentivizes a professor to change jobs to a lower ranking university?

In Japanese, what’s the difference between “Tonari ni” (となりに) and “Tsugi” (つぎ)? When would you use one over the other?

Today is the Center

Voyeurism but not really

String Manipulation Interpreter

How is it possible to have an ability score that is less than 3?

Is it unprofessional to ask if a job posting on GlassDoor is real?

How did the USSR manage to innovate in an environment characterized by government censorship and high bureaucracy?

How does strength of boric acid solution increase in presence of salicylic acid?

Is it legal for company to use my work email to pretend I still work there?

I’m planning on buying a laser printer but concerned about the life cycle of toner in the machine

Why, historically, did Gödel think CH was false?

What do "features" mean/refer to in this sentence?

Minkowski space

Minkowski MetricMinkowski Metric SignatureMinkowski metric — why does it follow from the constancy of the speed of light?Minkowski spacetime: Is there a signature (+,+,+,+)?Minkowski spacetime vs Euclidian spaceMinkowski metric: Why does it look like it does?Understanding space-like hyperplanes in Minkowski spaceCausality in general relativityCan an a distance in Minkowski space, based on a Euclidean plane, be time-like?How to Construct Proper Spherical Coordinates in Minkowski Spacetime?

1

$begingroup$

1) In Minkowski space, coordinates which satisfy

x²=t²-X²>0

Region of spacetime is time-like.

2) If its

x²=t²-X²<0

Region is space-like.

3) But if

x²=t²-X²=0

then its "trajectory of light-like particles".

I have understood the first two points about time and space like region but I could not get the third one about "light like particles".
My confusion is about why just light like particles? there are many other particles at quantum level.

special-relativity mass metric-tensor causality

share|cite|improve this question

edited 1 hour ago

Qmechanic♦

107k121991239

asked 2 hours ago

sk9298sk9298

595

New contributor

sk9298 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

$endgroup$

add a comment | 

1

$begingroup$

1) In Minkowski space, coordinates which satisfy

x²=t²-X²>0

Region of spacetime is time-like.

2) If its

x²=t²-X²<0

Region is space-like.

3) But if

x²=t²-X²=0

then its "trajectory of light-like particles".

I have understood the first two points about time and space like region but I could not get the third one about "light like particles".
My confusion is about why just light like particles? there are many other particles at quantum level.

special-relativity mass metric-tensor causality

share|cite|improve this question

edited 1 hour ago

Qmechanic♦

107k121991239

asked 2 hours ago

sk9298sk9298

595

New contributor

sk9298 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

$endgroup$

add a comment | 

$begingroup$

1) In Minkowski space, coordinates which satisfy

x²=t²-X²>0

Region of spacetime is time-like.

2) If its

x²=t²-X²<0

Region is space-like.

3) But if

x²=t²-X²=0

then its "trajectory of light-like particles".

I have understood the first two points about time and space like region but I could not get the third one about "light like particles".
My confusion is about why just light like particles? there are many other particles at quantum level.

special-relativity mass metric-tensor causality

share|cite|improve this question

edited 1 hour ago

Qmechanic♦

107k121991239

asked 2 hours ago

sk9298sk9298

595

New contributor

sk9298 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

$endgroup$

share|cite|improve this question

edited 1 hour ago

Qmechanic♦

107k121991239

asked 2 hours ago

sk9298sk9298

595

New contributor

sk9298 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

share|cite|improve this question

edited 1 hour ago

Qmechanic♦

107k121991239

asked 2 hours ago

sk9298sk9298

595

New contributor

sk9298 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

edited 1 hour ago

Qmechanic♦

107k121991239

edited 1 hour ago

Qmechanic♦

107k121991239

asked 2 hours ago

sk9298sk9298

595

New contributor

sk9298 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

asked 2 hours ago

sk9298sk9298

595

2 Answers
2

active

oldest

votes

3

$begingroup$

My confusion is about why just light like particles? there are many other particles at quantum level.

You are correct. The terminology is historical in nature. Light was the first massless particle to be discovered. The terminology “lightlike” was established before any other massless particles were discovered. Once other massless particles were discovered it was shown that they also travel along lightlike geodesics, but by then the term “lightlike” was well established.

An alternative term with the same meaning as “lightlike” is “null”. If you prefer then you can always use “null” and just understand that people saying “lightlike” mean the same thing.

share|cite|improve this answer

answered 2 hours ago

DaleDale

6,5971829

$endgroup$

add a comment | 

1

$begingroup$

Only particles with zero mass can travel between two events which are separated by a light-like distance. The trajectory is called light-like because photons (light) are massless, and historically the first example of a massless particle, as well as the only example in the 1910's. There are other massless particles, like gluons which would also be able to travel between two events separated by a light-like distance.

The reason why only massless particles are able to travel between two events separated by a light-like distance is that it requires you to travel at exactly the speed of light. You can see this by considering the equation $t^2-x^2=0$, this means that $x=pm t$. These equations are with the units such that the speed of light $c=1$. Thus the particle taking this trajectory is travelling at the speed of light.

share|cite|improve this answer

answered 2 hours ago

LucashWindowWasherLucashWindowWasher

30312

$endgroup$

add a comment | 

Your Answer

StackExchange.ifUsing("editor", function ()
return StackExchange.using("mathjaxEditing", function ()
StackExchange.MarkdownEditor.creationCallbacks.add(function (editor, postfix)
StackExchange.mathjaxEditing.prepareWmdForMathJax(editor, postfix, [["$", "$"], ["\\(","\\)"]]);
);
);
, "mathjax-editing");

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
);



);

sk9298 is a new contributor. Be nice, and check out our Code of Conduct.

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%2f470979%2fminkowski-space%23new-answer', 'question_page');

);

Post as a guest

Name

Email

Required, but never shown

3

$begingroup$

My confusion is about why just light like particles? there are many other particles at quantum level.

You are correct. The terminology is historical in nature. Light was the first massless particle to be discovered. The terminology “lightlike” was established before any other massless particles were discovered. Once other massless particles were discovered it was shown that they also travel along lightlike geodesics, but by then the term “lightlike” was well established.

An alternative term with the same meaning as “lightlike” is “null”. If you prefer then you can always use “null” and just understand that people saying “lightlike” mean the same thing.

share|cite|improve this answer

answered 2 hours ago

DaleDale

6,5971829

$endgroup$

add a comment | 

3

$begingroup$

My confusion is about why just light like particles? there are many other particles at quantum level.

You are correct. The terminology is historical in nature. Light was the first massless particle to be discovered. The terminology “lightlike” was established before any other massless particles were discovered. Once other massless particles were discovered it was shown that they also travel along lightlike geodesics, but by then the term “lightlike” was well established.

An alternative term with the same meaning as “lightlike” is “null”. If you prefer then you can always use “null” and just understand that people saying “lightlike” mean the same thing.

share|cite|improve this answer

answered 2 hours ago

DaleDale

6,5971829

$endgroup$

add a comment | 

$begingroup$

My confusion is about why just light like particles? there are many other particles at quantum level.

You are correct. The terminology is historical in nature. Light was the first massless particle to be discovered. The terminology “lightlike” was established before any other massless particles were discovered. Once other massless particles were discovered it was shown that they also travel along lightlike geodesics, but by then the term “lightlike” was well established.

An alternative term with the same meaning as “lightlike” is “null”. If you prefer then you can always use “null” and just understand that people saying “lightlike” mean the same thing.

share|cite|improve this answer

answered 2 hours ago

DaleDale

6,5971829

$endgroup$

share|cite|improve this answer

answered 2 hours ago

DaleDale

6,5971829

answered 2 hours ago

DaleDale

6,5971829

answered 2 hours ago

DaleDale

6,5971829

1

$begingroup$

Only particles with zero mass can travel between two events which are separated by a light-like distance. The trajectory is called light-like because photons (light) are massless, and historically the first example of a massless particle, as well as the only example in the 1910's. There are other massless particles, like gluons which would also be able to travel between two events separated by a light-like distance.

The reason why only massless particles are able to travel between two events separated by a light-like distance is that it requires you to travel at exactly the speed of light. You can see this by considering the equation $t^2-x^2=0$, this means that $x=pm t$. These equations are with the units such that the speed of light $c=1$. Thus the particle taking this trajectory is travelling at the speed of light.

share|cite|improve this answer

answered 2 hours ago

LucashWindowWasherLucashWindowWasher

30312

$endgroup$

add a comment | 

1

$begingroup$

Only particles with zero mass can travel between two events which are separated by a light-like distance. The trajectory is called light-like because photons (light) are massless, and historically the first example of a massless particle, as well as the only example in the 1910's. There are other massless particles, like gluons which would also be able to travel between two events separated by a light-like distance.

The reason why only massless particles are able to travel between two events separated by a light-like distance is that it requires you to travel at exactly the speed of light. You can see this by considering the equation $t^2-x^2=0$, this means that $x=pm t$. These equations are with the units such that the speed of light $c=1$. Thus the particle taking this trajectory is travelling at the speed of light.

share|cite|improve this answer

answered 2 hours ago

LucashWindowWasherLucashWindowWasher

30312

$endgroup$

add a comment | 

$begingroup$

Only particles with zero mass can travel between two events which are separated by a light-like distance. The trajectory is called light-like because photons (light) are massless, and historically the first example of a massless particle, as well as the only example in the 1910's. There are other massless particles, like gluons which would also be able to travel between two events separated by a light-like distance.

The reason why only massless particles are able to travel between two events separated by a light-like distance is that it requires you to travel at exactly the speed of light. You can see this by considering the equation $t^2-x^2=0$, this means that $x=pm t$. These equations are with the units such that the speed of light $c=1$. Thus the particle taking this trajectory is travelling at the speed of light.

share|cite|improve this answer

answered 2 hours ago

LucashWindowWasherLucashWindowWasher

30312

$endgroup$

share|cite|improve this answer

answered 2 hours ago

LucashWindowWasherLucashWindowWasher

30312

answered 2 hours ago

LucashWindowWasherLucashWindowWasher

30312

answered 2 hours ago

LucashWindowWasherLucashWindowWasher

30312