has light got mass?

[jimmer]

has light got mass?

 

jim

[bernardo]

Yes - i.e. it is bent by gravity

[jimmer]

why isn't its mass infinite then? ha ha

[Tweed]

Light has no mass. Photons have no mass

[GuavaHalf]

No is a yes sort of way! Very complex area of physics. Try this link for an explanation.

http://math.ucr.edu/home/baez/physics/Relativity/SR/ligh t_mass.html

[jimmer]

awww. i don't have permission to enter that site. is this destined to remain a mystery to me?

 

jim

[Tweed]

remove the <P> at the end of the URL

[jimmer]

ok so having read a bit on the web i'll have a stab at it: when one says "mass tends towards infinty as an object accelerates towards to the speed of light" one should say  "relativistic mass tends towards infinity as an object accelerates towards the speed of light" which actually means "energy tends towards infinity as an object accelerates towards the speed of light"

if this is right does that mean that light has infinite energy?

jim

jim

[delapeyre64]

Interesting if light has no mass then it would be imposible to convert it to electricity. It would also have no speed limit it would also be able to escape black holes. But it has a speed it carries energy in it due its speed and wave lengh almost like rms and pmpo and it cant defy gravity therefore it has a mass and an energy.

[delapeyre64]

But Of Course We Could Also Say This Is All Theory! Whenever Things Cant Be Explained We Have Them.

Problem is trying to measure these things actually upsets the results!

[QmunkE]

Bendy space makes my head hurt.

Perhaps we are not yet capable of truly understanding the way stuff moves around in the universe.

[Hamish]

OK try this. Light does not have a stationary mass,  but it does have inertia related to the energy at which it is emitted (wavelength). As light is the transmisson of radiative energy through space it cannot be 'stationary' and does not involve an accelleration. It would be like trying to measure the hight of a wave in the sea by cutting the top off and pouring the water out onto the beach .... result, hight =0.

[jimmer]

omunke. well i certainly am not capable of understanding the way stuff moves around the universe.

Harnish: thanks for an answer i can get my head around.

 

jim

[Nashwolfe]

Dela says: Interesting if light has no mass then it would be imposible to convert it to electricity.

Actually no. If light HAD mass, it would be practically impossible to convert it to electricity - energy may be converted between types fairly easily, but destroying mass to create energy, whilst theoretically very profitable ( e = mc^2   meaning destroying an atom could power my PC for a day ) is extremely difficult 

[Dacetine]

Light has no mass which is why it travels at the speed of... light. In fact any particle with zero mass must travel at the speed of light (and there are some other than photons of light itself - gravitons and gluons for instance, and perhaps also neutrinos).

Light is not bent by gravity but space is. Light following a "straight" path through bent space appears bent itself.

[incitatus]

ok, heres another go....

 

if you slowed a photon down to a standstill, then weighed it, it would have no mass.  this is why it doeasnt have infinite energy, because the rest mass is zero.  However it does, when moving, have energy equal to a constant (planck) times its frequency.  This energy is effectively its travelling mass, though the mass of each photon is small.

light is trapped in black holes by the curvature of space, not by attraction.