I was reading an article about the new collider photon-photon, and the writer says "the scientists accelerate photons in a very high speed".

It's non sense to me, because as far I know a photon only moves on the speed of light.

So my question is: Can a photon move at another speed that's not the speed of light?


This is the article about photon-photon collider:


I found the snippet about accelerating photons at a very high speed in this Portuguese article:


  • 2
    $\begingroup$ Photons only move with the speed of light. Can you give the link to the article please? $\endgroup$
    – Hasan
    May 19, 2014 at 19:30
  • 1
    $\begingroup$ probably protons not photons $\endgroup$
    – DavePhD
    May 19, 2014 at 19:34
  • $\begingroup$ Photons, not protons $\endgroup$ May 19, 2014 at 20:05
  • $\begingroup$ I put the link of portuguese article in the question $\endgroup$ May 19, 2014 at 20:12
  • 1
    $\begingroup$ I don't speak Portuguese well, but the sentence "a colisão de dois fótons a uma velocidade altíssima resultaria na criação de um elétron e um pósitron" seems to phrase the collision as being "high-speed"; it probably was supposed to be "high-energy", but the writer just mixed the words. $\endgroup$ May 19, 2014 at 20:30

2 Answers 2


I think you are referring to a recent proposal to create matter with pure light (high energy photon-photon collisions): http://www.nature.com/nphoton/journal/vaop/ncurrent/full/nphoton.2014.95.html

The article you were reading very likely misinterpreted something or confused "high energy" with "high speed". Light (in a vacuum) only travels at the speed of light.

  • $\begingroup$ Yeah i'm saying about this article. The writer of portuguese article probably got confused between high energy and high speed? $\endgroup$ May 19, 2014 at 20:09
  • $\begingroup$ Consider the article link I posted in the comment to Lucas' question. It is said that scientists have created a new state of matter from photons and even hope to one day build a 3d structure entirely from light. $\endgroup$
    – Klik
    May 21, 2014 at 21:38
  • $\begingroup$ It is a different topic, but very interesting! $\endgroup$
    – DrEntropy
    May 23, 2014 at 3:06

Yes, normally $c$ is for speed of light in vacuum at which light travels at its maximum speed. However if I were to put, say, atmosphere or diamond in from of a light beam, the light would travel slower than $c$, therefore I conclude yes its possible to travel slower than the TRUE speed of light. Next, to elaborate, in 1905, Einstein's miracle year, he proposed his mass-energy equivalence theory which is $E=mc^2$. This must mean, with some simple rearranging, we understand that mass can be converted in energy and vice-versa. That in mind, a photon is an packet of energy in basic definition. That in mind, we can convert the photons into mass using the formula rearranged: $m=E/c^2$ which means we can even make light travel even at 0 indirectly.


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