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taylordnz
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could you out there prove to me that light has no mass because i read a lot and it always says that light has no mass and no one has told me why it has no mass please help
Originally posted by wisp
Some proof that light has no mass.
If it had mass then photons traveling to us from far reaches in the universe would clump together because of gravitational attraction.
There is no evidence that this happens and so we can assume light has no mass.
But it does have momentum and so there must be some sort of "mass" associated with its speed. But this does not have a gravitational effect like normal mass.
My own view is that normal matter causes spherical distortion to the ether that causes the mass from the ether to be attributed to matter. Light distorts the ether in a different way to normal matter and as such doesn't cause the gravitational effect. It does have mass, but not mass that has a gravitational effect.
Originally posted by Hypercase
In the case of the photon the rest mass is zero, or else it would require infinite energy to propel it to light speed.
However we notice that light has momentum.(photoelectric effect, use of light sails.)(zapper the are not scifi anymore, please refer to scientific american 2003 nov issue.)
the Newtonian formula for momentum is p=mv
using this light has no momentum.
However if i calculate mass accordin to the second definiton above,
I get m=E/c^2
now energy of a photon is
E=hf
substituting this above I get m=hf/c^2
Originally posted by Grim
so Zapperz you seem to know a bit about this,
if light has no mass would that mean that it is pure energy.. also how does this fit in with light being called a dualility?
Light has no proper mass (aka "rest mass"). That doesn't mean it doesn't have "mass" i.e. inertial, passive gravitational and active gravitational mass.Originally posted by kheorman
Okay. Let's try this on for size.
Light has no mass? Must we have numerous definitions of mass to satisfactorily explain physical phenomenon, or have we just not discovered the true nature of matter and energy?
Thus light as a non-zero passive gravitational mass.
So light has no mass? But light is effected by strong gravitational fields. It bends around the sun and provided evidence that Einstein was correct. It can be trapped by the event horizon of a black hole according to astrophysics.
Light is just electromagnetic radiation of very high frequency.
Is it just light (visible spectrum) or are all forms of electro-magnetic radiation effected by strong gravitational fields?
If so, are higher energy photons more 'massive' than lower energy ones, and therefore would 'bend' further when passing through a strong gravitational field?
[/qutote]
The higher the frequency of light the greater its mass. However if the mass of something is neglegible compared to the mass of the source of the gravitational field then the rate at which something falls or is deflected is independant of the mass. E.g. a car falls just as fast as a penny in vacuum. Same with high and low mass photons.
Sure. We've observed the deflection of light by the sun. Cosmologists often speak of the mass of radiation when speaking of gravitational sources in the universe.
Has any astronomical research been conducted to determine these answers?
Because you've made a false assumption. You've incorrectly assumed that the formula
So if light has mass, why isn't it's mass infinite at 'c'?
[tex]m = \frac{m_0}{\sqrt{1-v^2/c^2}}[/tex]
was derived with photons in mind. It was not. The inertial mass of a particle is the ratio of its momentum to its speed. Thus if p is the momentum of a photon then, since its speed is c, them the inertial mass is given by m = p/c. If the particle is not a photon then we can assume that it can have a speed which can take on any value greater than or equal to zero but less than c. When we start with that knowledge then it can be shown that the mass is a function of the velocity.
Because that would mean that all light has the same momentum and that is contrary to experimental evidence. So long as light have ahve different amounts of momentum then it can have different amounts of inertial mass. The mass being soley a function of frequency/momentum.
So if the speed of light in a vacuum is a constant regardless of the inertial frame of reference, then why would is be so far fetched to believe that the mass of light is constant also?
Antonio Lao said:Previous posts already shown the following equation for the relativistic mass m(v) of a photon.
[tex]m(v) = \frac {m_0}{\sqrt{1- \frac{v^2}{c^2}}}[/tex]
transposing
[tex]m_0 = m(v) \sqrt{1- \frac{v^2}{c^2}}}[/tex]
if v=c then [tex] m_0 = 0 [/tex]
fermions - in which quark sets do not orbit one another--Kurious