Does light, theoretically, have any mass?

[Ipquarx]

Just wondering, how many of you have taken first year physics, let alone advanced physics? And how many of you are reading stuff on Wikipedia and then posting here (or just plain and simply are making these things up)?

I've taken second year physics and am currently taking third year physics.

[Ad Bot]

[BluetoothBoy]

Light is not matter.
"Matter" is any particle which takes up space and has mass.
Therefore, photons do not have mass.

That's... really backwards thinking.

[Steve5451²]

i've only taken an intro to physics during my freshman year.
i read a lot on certain physics, mostly specific particles, neutrinos, higgs-boson, photons. i haven't found a good place to really start learning from the beginning of physics until recently.

I'm taking intro to physics...in my junior year.

[Stocking]

Well anything that has mass cannot reach the speed of light so I guess light is massless.

that's a theory though, merely nothing has been observed travelling at that speed

[$trinick]

Just wondering, how many of you have taken first year physics, let alone advanced physics? And how many of you are reading stuff on Wikipedia and then posting here (or just plain and simply are making these things up)?

The only formal class I've taken about physics is Highschool physics, but that doesn't even begin to encroach upon topics like these. Everything I know about quantum physics has come from one of three sources; Stephen Hawking, Wikipedia, and my father. I recognize the last holds no credibility, but he's responsible for teaching me all of the basics of physics to answer my childhood questions. The more advanced things I learned on my own and merely discussed with him.

[Blockzillahead]

yes
photons

[Nexus]

thats like saying you aren't affected by gravity unless you are more than 100lbs.  There isn't a theoretical wall of gravity that has to be broken before the light is affected by it.  It is affected by gravity period.  The reason it doesn't fall straight to the ground is because it is moving at such an insanely high speed.  It passes by Earth too fast to "fall down".  It isn't fast enough, though, to escape a black hole.

I guess this poses the question would light have any measurable mass if we were able to theoretically stop a photon and measure it.  We know that light travels faster in a vaccum than it does in earths atmosphere so it apparently is colliding with the molecules in the air, but further I can't really elaborate on it because it's beyond my realm of knowledge.

Did you read the posts right above yours wtf, that isn't how gravity and light interact.
Also no the photons are not colliding.  The speed of light is different for different mediums.  That's why 'c' is qualified as the speed of light in a vacuum.

for a mass then (say a brick) to move at the speed of light would require an infinite amount of energy. from our current understanding of the universe, that's not possible.

Right.  Not sure if you are disagreeing with something I said or something but yep.

[Treynolds416]

I've taken second year physics and am currently taking third year physics.

Same here. I didn't read pages 2-5 of this thread but there's a definite answer so I don't know why there was this much discussion. Light exhibits qualities of both a particle and a wave. It is composed of photons. Photons have mass. End of story.

Sort of related: I read an article a while ago about how laser-propulsion systems are the next generation in space travel. The laser shoots behind the spacecraft and it is propelled forward. Apparently it's very efficient and can reach very fast speeds (in environments with negligible friction). Anyone who knows about newton's third law will concur that light has mass

[Nexus]

there's a definite answer
Photons have mass.

Nope, maybe you should read back then

There is definitely a consensus on an answer on page one, but that doesn't make it the correct answer.

[Swat 3]

Light is not matter.
"Matter" is any particle which takes up space and has mass.
Therefore, photons do not have mass.

....

photons are loving particles you nitwit

[Mr. Hurricane]

....

photons are loving particles you nitwit

They are both a wave and particle to my understanding.

Photons exert some sort of pressure that is observable in solar sails, it's pretty much the whole reason a solar sail works to my understanding.

[Ipquarx]

Photons are particles, yet they have no rest mass. They have inertial mass, which is not the same thing. If you tried to "weigh" a photon that was theoretically sitting as a regular particle at rest in the gravity field of earth, you would find that it does not have any mass whatsoever.

[Swat 3]

If they don't have mass, how are they matter?

Sorry first-year physics is not doing me any good, but I love thinking about these subjects.

[Jaxx]

Photons are particles, yet they have no rest mass. They have inertial mass, which is not the same thing. If you tried to "weigh" a photon that was theoretically sitting as a regular particle at rest in the gravity field of earth, you would find that it does not have any mass whatsoever.

Except no. Gravitational lensing means this is the opposite of true.

[Lego lad]

If they don't have mass, how are they matter?

It doesn't matter!