Can Energy Exist Without Mass?

[ZapperZ]

Why is wikipedia saying that photons have mass then? Not rest mass, no. But look at my quote. Are they just wrong or is this some kinda gray area or misunderstood area?

Here's the http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/tdil.html" :

$$m = \gamma m_0$$

where $m_0$ is the rest mass, and $\gamma$ is the usual relativistic factor.

What is m when the rest mass is ZERO? What do you believe more? Wikipedia, or the physics? What is the credential of the person (or persons) who wrote that Wikipedia entry that you trust so much?

Light has MOMENTUM. The apparent "inertial" reaction that light has is due to this momentum, not due to "mass", relativistic or not. There is no "gray or misunderstood area" here.

Zz.

 

[russ_watters]

Why is wikipedia saying that photons have mass then? Not rest mass, no. But look at my quote. Are they just wrong or is this some kinda gray area or misunderstood area?

Your quote does NOT say that photons have mass. You misread/overinterpreted a simplistic bullet point. For full treatment you should read the full article they linked at the end of the point!

...or better yet, read the article specific to the question: the photon article. It says in plain english a dozen times that the photon has no mass!

 

[Jarfi]

Your quote does NOT say that photons have mass. You misread/overinterpreted a simplistic bullet point. For full treatment you should read the full article they linked at the end of the point!

...or better yet, read the article specific to the question: the photon article. It says in plain english a dozen times that the photon has no mass!

Photons have mass because they have momentum and if they had no momentum they wouldn't exist because photons can't exist without momentum so they must have mass

 

[ZapperZ]

Photons have mass because they have momentum and if they had no momentum they wouldn't exist because photons can't exist without momentum so they must have mass

This is wrong. You need to read the PF FAQ in the General Physics forum first before making such statements.

Zz.

 

[sahil_time]

Photons have mass because they have momentum and if they had no momentum they wouldn't exist because photons can't exist without momentum so they must have mass

Only according to classical Physics P(Momentum)=Mass*Velocity! Not according to modern Physics where all u need is energy to carry it!:)

 

[Drakkith]

Your quote does NOT say that photons have mass. You misread/overinterpreted a simplistic bullet point. For full treatment you should read the full article they linked at the end of the point!

...or better yet, read the article specific to the question: the photon article. It says in plain english a dozen times that the photon has no mass!

What article at the end of the point? (Did I misunderstand what a "Point" is in wikipedia? I didn't see anything linked after the part I quoted.)

Alright, I wholeheartily agree that photons have no mass. I've read up a little bit more on it all and it appears to me that there is simply a lot of confusion over the concept of mass. This quote from Einstein sums it up pretty well in my opinion.

It is not good to introduce the concept of the mass of a moving body for which no clear definition can be given. It is better to introduce no other mass concept than the 'rest mass' m. Instead of introducing M it is better to mention the expression for the momentum and energy of a body in motion.

Gotta go do some stuff here at work, I'll be back later.

 

[Drakkith]

In addition to my previous post, I have read that the concept of Relativistic mass is outdated and not used anymore. No wonder there's confusion...

So, Photons have NO mass of any type (since I guess there's really only 1 type of mass, rest mass?).