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decibel
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today in my physics class, teacher told me that light doesent have mass...i thought it did...wuts the final answeer to this question, does it have mass or not?
[?] [?] You're not insulting him for asking a question, are you?Originally posted by PrudensOptimus
rofl, hi 9th grader.
It's very hard to understand why it would have no mass..If light is distributed through 3rd/4th dimension, wouldn't it have to be mass for it to exist physically?
and what about time, does it have a mass?
Originally posted by decibel
ok so if light has no mass, how can it get sucked in by black holes?
Originally posted by LaserFloyd
Wasn't there an experiment some time ago that showed light can exert force? I can't put my finger on the guy's name. Anyhow he did an epxeriment where light beams of some sort exerted a pressure on some sort of metal in a vacuum. (I'm sure someone could elaborate more on that)
Since mass is part of the force equation, wouldn't light have mass even if it is so small it's almost non-existent?
[?]
Originally posted by Ambitwistor
Yes, light exerts a force. It can do that because force is a change in momentum (F=dp/dt), and light does have momentum. (F=ma only in non-relativistic mechanics; it is interesting to note that F=dp/dt was Newton's original definition, which still holds in relativity.)
Originally posted by cepheid
To futz...hello to a fellow Edmontonian. [/B]
ok so if light has no mass, how can it get sucked in by black holes?
Originally posted by Ambitwistor
You could equally well ask, how can its trajectory be deflected by the gravity of any body. Light (as well as massive bodies) travel in straight lines through spacetime, but if the geometry of spacetime is curved, then "straight lines in spacetime" can be curved trajectories in space.
Just a clarification here - Ambitwisor, I think you missed his wording and the misconception continued: The phrase "sucked in" is misleading. NOTHING gets "sucked in by a black hole" any more than the Earth's gravitational field "sucks" anything in. The gravitational field of a black hole is only special as a result of its magnitude. So a black hole with the mass of the Earth would act the same as the Earth toward an object in orbit. And a photon of light will only enter the black hole if it is headed on a trajectory that crosses the event horizon.because black holes are sucking in matter at the speed of light, but the black hole has mass-a lot of mass, therefore light can't escape.
Originally posted by russ_watters
Just a clarification here - Ambitwisor, I think you missed his wording and the misconception continued:
Maybe he can answer that, but I think that is the crux if his question.Originally posted by Ambitwistor
Whether we choose to say that light (or matter, or whatever) is "sucked in" or not is not relevant to that question.
Originally posted by decibel
yes it is russ
He probably didn't understand either - its just that the way he asked the question focused on one particular misconception.Originally posted by Ambitwistor
Just to be clear: you said that the crux of your question involves specifically light being "sucked into" black holes, and not with whether light is influenced by the gravitational interaction of another body.
If that's the case, then you accept that gravity will attract massless particles, but you don't know how gravity can suck massless particles into black holes? Why do you accept one, but don't understand the other?
I've said this before, I tend to think that when people understand a topic REALLY well (like you), they tend to miss some of the more basic misconceptions people have about the topics.
Well, in any case its not a big deal as long as we've helped him.Originally posted by Ambitwistor
Actually, I still think you're focusing on the wrong misconception. I've seen (and answered) the "cosmic vacuum cleaner" question all the time, but I ignored it because I still don't think it's the core issue. The core issue was how black holes can specifically suck in massless particles, and misconceptions concerning whether black holes "suck things in" at all (massive or massless) are a side issue.
Originally posted by futz
Light is made of photons, which have no mass (rest mass, anyway).
Originally posted by MirabileAuditu
"Light" in any real sense of the word, is not at "rest." It is moving.
Mass and energy are interchangeable.
Is it not logical that the MASS lost by the sun is GAINED elsewhere?
I seem to recall a maxim of thermodynamics that matter can neither be created nor destroyed . . . .
No offense, but that's pretty illogical.Originally posted by decibel
i still think for some reason, that light does have mass, i don't know why but i do.
No, light does not have mass. According to the theory of relativity, mass is equivalent to energy, and light is a form of energy. Therefore, it does not have a physical mass like other particles.
The controversy surrounding the mass of light stems from the fact that it exhibits properties of both particles and waves. While particles have mass, waves do not. This has led to debates and different theories about the nature of light.
Yes, light can be affected by gravity even though it does not have mass. This is because gravity affects the curvature of space-time, and light follows this curvature. This phenomenon is known as gravitational lensing.
The mass of light cannot be measured directly since it does not have a physical mass. However, its energy can be measured using equations such as E=mc², where E represents energy, m represents mass, and c represents the speed of light. This energy can then be used to calculate the equivalent mass of light.
If light had mass, it would not be able to travel at the speed of light. This would have significant implications for our understanding of the universe and the laws of physics. Additionally, the fact that light does not have mass allows it to travel through a vacuum, making it essential for communication and technology such as fiber optics.