BenB
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| posted on 31/1/12 at 09:55 AM |
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OT: thought for the day
Ben's random shizzle of the day.
Do photons have mass?
My theory goes like this- photons have energy in them (otherwise what's powering the solar panels on my roof). We all know e=mc^2. For e to not
be zero m must have a value (even a small one).
Then again, the photon moving at the speed of light in a vacuum would suggest it is truly massless.
Confusing eh? 
Bloody duality of photon theory.
Are they a particle? Are they a waveform? Do they weight anything? Or nothing? Who cares?
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jabbahutt
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| posted on 31/1/12 at 10:03 AM |
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you lost me after thought for the day
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roadrunner
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| posted on 31/1/12 at 10:04 AM |
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Which came first, the chicken or the egg.
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fesycresy
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| posted on 31/1/12 at 10:19 AM |
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Easy.....
No, photons do not have mass, but they do have momentum.
The proper, general equation to use is E2 = m2c4 + p2c2
So in the case of a photon, m=0 so E = pc or p = E/c.
On the other hand, for a particle with mass m at rest (i.e., p = 0), you get back the famous E = mc2.
This equation often enters theoretical work in X-ray and Gamma-ray astrophysics, for example in Compton scattering where photons are treated as
particles colliding with electrons.
I can copy and paste with the best of them
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The sooner you fall behind, the more time you'll have to catch up.
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JoelP
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| posted on 31/1/12 at 10:27 AM |
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A similar issue applies to gravitational lensing. Popular belief is that mass deforms space, hence why things can orbit around bodies with mass. This
means photons think they are travelling in a straight line when they get bent around a heavy object, as it is the space that is bent. However, it
could be they have mass and are attracted to it like any otehr mass.
Also, to have momentum, surely you need mass, since momentum is mass times velocity?
I do appreciate that what we are discussing was probably regarded as simple 30 years ago, and i doubt its even up for debate nowadays, but its always
made me wonder.
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whitestu
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| posted on 31/1/12 at 10:33 AM |
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quote:
Do photons have mass?
I didn't even know they believed in God!
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BenB
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| posted on 31/1/12 at 10:34 AM |
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quote:
Originally posted by roadrunner
Which came first, the chicken or the egg.
That's easy.
Species are slowly evolving from one species into the next. Now there has to be a cut-off when we say a certain genotype is a new species and we shall
call that new species "chicken". Now the DNA that subsequently makes that chicken was first present in it's entirety in the egg.
therefore the (species chicken) egg came first.
Unless it's a trick question and the "egg" in the question isn't a chicken egg but infact a dinosaur egg in which case the egg
(as a method of gestation and birth) came about first.
but that's really cheating because everyone assumes we're talking about a chicken egg.
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BenB
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| posted on 31/1/12 at 10:35 AM |
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quote:
Originally posted by whitestu
quote:
Do photons have mass?
I didn't even know they believed in God!
LOL! Quality.
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BenB
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| posted on 31/1/12 at 10:41 AM |
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quote:
Originally posted by JoelP
A similar issue applies to gravitational lensing. Popular belief is that mass deforms space, hence why things can orbit around bodies with mass. This
means photons think they are travelling in a straight line when they get bent around a heavy object, as it is the space that is bent. However, it
could be they have mass and are attracted to it like any otehr mass.
Also, to have momentum, surely you need mass, since momentum is mass times velocity?
I do appreciate that what we are discussing was probably regarded as simple 30 years ago, and i doubt its even up for debate nowadays, but its always
made me wonder.
This is where it gets confusing huh? Photons don't have mass but they have momentum. So either Newton was barking up the wrong tree and momentum
isn't a function of mass or solar sails don't work due to the impulse imparted by photons.
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jabbahutt
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| posted on 31/1/12 at 11:11 AM |
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So far I've only understood that chickens come from eggs
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balidey
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| posted on 31/1/12 at 11:31 AM |
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My mate had one and it weighed just over a tonne.
Dutch bears have terrible skin due to their clogged paws
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owelly
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| posted on 31/1/12 at 11:42 AM |
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Fanny batter.
http://www.ppcmag.co.uk
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matt_gsxr
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| posted on 31/1/12 at 12:04 PM |
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of course they have mass!
Otherwise black holes wouldn't be black.
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JoelP
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| posted on 31/1/12 at 12:08 PM |
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quote:
Originally posted by matt_gsxr
of course they have mass!
Otherwise black holes wouldn't be black.
Thats the same concept as gravitational lensing, so techincally, i agree with you!
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roadrunner
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| posted on 31/1/12 at 12:47 PM |
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quote:
Originally posted by balidey
My mate had one and it weighed just over a tonne.
Thats one fat chicken or egg.
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roadrunner
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| posted on 31/1/12 at 12:48 PM |
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quote:
Originally posted by matt_gsxr
of course they have mass!
Otherwise black holes wouldn't be black.
I thought Black holes where black because the gravitational pull is so strong that light can not escape from them.
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RK
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| posted on 31/1/12 at 12:55 PM |
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and here I was wondering what I was going to have for breakfast.
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blakep82
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| posted on 31/1/12 at 12:58 PM |
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quote:
Originally posted by roadrunner
quote:
Originally posted by matt_gsxr
of course they have mass!
Otherwise black holes wouldn't be black.
I thought Black holes where black because the gravitational pull is so strong that light can not escape from them.
but then wouldn't the light particles have to have a mass to be affected by the gravity pull?
otherwise, if they didn't have mass, and weren't affected, the light could then escape, and they wouldn't be black
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don't write OT on a new thread title, you're creating the topic, everything you write is very much ON topic!
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MikeRJ
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| posted on 31/1/12 at 03:33 PM |
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They have relativistic mass i.e. their resting mass is zero, but their mass increases as their velocity increases.
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JoelP
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| posted on 31/1/12 at 06:37 PM |
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quote:
Originally posted by MikeRJ
They have relativistic mass i.e. their resting mass is zero, but their mass increases as their velocity increases.
Thats hypothesis! All that is certain is the maximum limit on their mass (which is indeed tiny), and that massless fits in with some models.
And yes, i did google that earlier, but i suspect you did too mike
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Marcus
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| posted on 31/1/12 at 08:27 PM |
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quote:
Originally posted by balidey
My mate had one and it weighed just over a tonne.
Yeah, that'd be a Proton mate (and not the positively charged sub atomic version)
Marcus
Because kits are for girls!!
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deltron63
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| posted on 31/1/12 at 08:39 PM |
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So, if the universe is ever expanding, what's it expanding into ? Before the big bang there was nothing.
Just a thought
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Ninehigh
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| posted on 31/1/12 at 09:29 PM |
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quote:
Originally posted by whitestu
quote:
Do photons have mass?
I didn't even know they believed in God!
I believe that is the win.
I suppose if they must have a mass, and yet be regarded as massless then maybe the mass is so small that even with the mass exponentially increasing
as they approach the speed of light they can still be mathematically (and practically) massless.
I.e if they weigh 2x10-500g (zero point five hundred zeroes and two grams) then you could multiply that by a british billion and it would still be in
need of some pies to be noticed!
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JoelP
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| posted on 31/1/12 at 10:45 PM |
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A quick google revealed that, when physicists are discussing photons mass, they are on a totally different level to us. They arent on about gravity as
we see it, they arent on about mass as we see it, and everything they are considering is tied up deep in general relativity, quantum mechanics, string
theory, and a whole load of stuff that turns the whole debate on its head.
At that point i gave up reading, because no one can know everything, and there really is no point spending ages trying to understand something that
has absolutely no value beyond baffling your mates in the pub.
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MikeRJ
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| posted on 31/1/12 at 11:14 PM |
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quote:
Originally posted by JoelP
And yes, i did google that earlier, but i suspect you did too mike
Actually I asked the same question to our chief scientist at work a few weeks ago
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