Light: Does It Have A Mass?

Originally posted by sardion2000
If you want people to actually take you seriously for a change stop talking down to them.

I am not talking down to anyone. If you feel your beneath me get off the ground and make sure you do not defend lies.

Whenever I see someone disagree with you, you go and say something like the above quote.

Only when i am reasonable sure i am on the good side of current facts and if they made it clear they do not have any respect for those who disagree with them.

You said that University textbooks are misinformed remember that? No that wasn't it you said...

I did and i am glad i have your full attention.

Now you say go argue with people who have degrees who had to be misinformed from those same textbooks in order to get said degree. WHICH IS IT!?!?! You're contradicting yourself.

Not all scientist believed what they read in their university text books and thus we have progress in science. I quote these specific people because they clearly KNOW their text books yet chose to improve/disagree with the statements made in them.

Hope you understand where i am coming from now!
The post above should have been enough to explain my general feeling.


Stellar

Originally posted by bigpappadiaz
I'll take this one on dude, some people need explaining.

The point he was trying to drill through your head is that people like you only tend to believe those with degrees, he's not going to waste his brain space learning a big fat book's worth of crap and clutter wrote by a bunch of people who admit they don't really understand how "it all" works so how do we know learning the teachings and techniques in it will give us the right thought processes we need to understand the universe, and finally, go ahead and argue with someone like that because you'd obviously find it much more fascinating although not necessarily elightening.

There are points in learning when breakthrough discoveries are made and we supposedly can't predict what the future will be like because we don't know how we'll build ourselves around these discoveries. Being stuck in one mindset won't help you "break on through to the other side."

bpd,

While I have noticed that, certain portions, of your posts and idealogy have merit, they all too often seem rather accusatory and aggressive in nature. The result being responses containing more of the same, and the beat goes on, ending with off-topic personal conflicts, Mod interventions, Warns, or thread closures.

I am not attempting to Mod this in any way, please. I'm simply trying to convey the thought of "step back, take a few breaths, post again/respond accordingly".

By doing so, I feel your contributions here will receive a much warmer and more receptive response, which will allow for a continued civil exchange of ideas and collaboration of the topic at hand.

For what it's worth ...
Just my $.02

I can't find it right now, but several years ago, I was reading an article on light and it said that sunlight was pressing against the Earth's surface at a rate of about 6 lbs./mi.^2. The total weight against the entire Earth's surface is equal to about the weight of a modern luxury liner.

So it's my assumption that light definitely has mass. Very little but still has mass.

Got to go. Someone help me out.

Many years ago in my college classes we learned that light exhibits properties of both wave and particle!

I have been thinking about this stuff for a while now.

If light cannot escape a black hole, does that mean that the photons are being accelerated to a speed greater than the speed of light towards the centre of the black hole? If this is possible, does it also mean that all other mass that is 'sucked' into a black hole is also being accelerated to a speed greater than the speed of light?

Also, what governs the intenstiy of a light? The light from the sun can be seen very far away, but the light from a dim bulb does not travel very far. Is this related directly to the energy given to the photons when they are released? - and how?

I beleive that present day quantum mechanics are only a 'best fit' model for what we know, in much the same way that newtons laws were (are). One day a great mind will calculate a better fitting theory than Einstein for quantum mechanics - i.e greater than light speed travel will be possible!

As for reading about this stuff, the Uncle Albert books by Russell Stannard are fantastic (even though they are childrens books!)

Originally posted by DeepCoverUK
If light cannot escape a black hole, does that mean that the photons are being accelerated to a speed greater than the speed of light towards the centre of the black hole? If this is possible, does it also mean that all other mass that is 'sucked' into a black hole is also being accelerated to a speed greater than the speed of light?

Also, what governs the intenstiy of a light? The light from the sun can be seen very far away, but the light from a dim bulb does not travel very far. Is this related directly to the energy given to the photons when they are released? - and how?

Well, I'll answer these for you. First, light is not accelerating as it enters the black hole. The space it's travelling along becomes stretched in such a way that it becomes trapped. Think of it like rolling a marble around a bowl. If it's going fast enough, it'll skip out of the bowl. But if it's not fast enough, it will start spinning around and around the bowl, moving in towards it center. The truth of this isn't far from reality - except in a Black Hole's case, the bowl has infinite depth to it - so if the marble ever goes down, no matter how fast it's going, it'll never come back out again.

As for the second question, the intensity, or the brightness of light comes from photons/area. The more photons there are per area of space, the brighter it is. Low-powered lightbulbs release very few photons, and so are dim. Stars release massive amounts of photons, and so can be seen from lightyears away.

Note that this makes seeing far away galaxies very difficult. We're only seeing a few photons from every star. In fact, as Carl Sagan put it, all the energy ever collected from all the radio telescopes in the world, amounts to the amount of kinetic energy released by a single snowflake hitting the ground.

So you can see, it all has to due with photon density/popularity rather than the strength of individual photons themselves.

Hmm...maybe I misread something, but someone seemed to imply that because photons have momentum they have mass. Just because something has momentum, does not mean it has mass.

Originally posted by T_Jesus
Hmm...maybe I misread something, but someone seemed to imply that because photons have momentum they have mass. Just because something has momentum, does not mean it has mass.

Well, it may be because the Newtonian formula for determining momentum is mass times velocity. So one may think that if it has momentum it must have mass.

Newton also says that light isn't a constant, gravity propogates instantly and time is constant and not relative. We all know how that turned out

[edit on 24-1-2006 by sardion2000]

[edit on 24-1-2006 by sardion2000]

Originally posted by sardion2000
Newton also says that light isn't a constant, gravity propogates instantly and time is constant and not relative. We all know how that turned out

[edit on 24-1-2006 by sardion2000]

[edit on 24-1-2006 by sardion2000]

And I think that is why it is a mistake to associate an intermediate scale formula to examine the characteristics of a single photon. But to Newton's credit he did develop calculus and author the Principia.

On a side note, I have a liberal arts professor who thinks that Copernicus theorized that the earth 'evolves' around the sun.I don't believe Copernicus knew about or subscribed to any Gaia theory.

Originally posted by sardion2000
math.ucr.edu...

The short answer is "no", but it is a qualified "no" because there are odd ways of interpreting the question which could justify the answer "yes".

But you can say that the photon has relativistic mass if you really want to. In modern terminology the mass of an object is its invariant mass which is zero for a photon.

I actually read that article before I posted my reply to Yarium. Plus a few others on the subject too.
Outdated or not "relativistic mass" is a very usefull concept without which many phenomena would be in-comprehensible to us today.
Also it is used for all other particles then why not a photon ? Also they dont say why one should not use the particle and merely resort to calling it as mass-energy which is merely playing semantics.

Posted by Intelearthling
I can't find it right now, but several years ago, I was reading an article on light and it said that sunlight was pressing against the Earth's surface at a rate of about 6 lbs./mi.^2. The total weight against the entire Earth's surface is equal to about the weight of a modern luxury liner.

Yeah I saw that on TV too. What they were refering to then was the fact that the photons when the impinge on the earths surface trasfer realtive momentum equall to that of a mordern luxury liner.
That is photons strike the earth surface, trasfer some of their momentum on the earths surface before reflecting away.

Posted by Sardion2000
Newton also says that light isn't a constant, gravity propogates instantly and time is constant and not relative....

Well, the Einsteinian model has not yet conclusively proved the speed of gravity yet. It is theorized to be greater than the speed of light if much of cosmology and astrophyisics is to be understood on present models.
Before you employ " google " again, let me say that yes there has been an experiment that claims to have proven the speed of gravity but is not widely recognised as a definitive enough.

Also the theorectical models call for faster than light speeds that are would be required to explain properly why the earth doesnt jsut spiral into the sun, etc.
In the end, it remains to be seen who the victor is but as they say- " without the father there is no son ".

The question I would like answered is whether or not the general consensus is now that space-time curvature is not mass-dependent (whether at rest mass or accelerated mass) and that the triad of mass, energy, and dimensional structure (for lack of a better term - I'm a layperson) thought to play into one another (i.e. acceleration increases mass, enough mass can alter the number of dimensions matter exists in, etc.) may not be as interdependent upon one another as was believed.

In other words, might it be possible to cause curvature of space-time in the absence of sufficient mass? If space-time is indeed a curved "fabric" (at least conceptually when we visualize it), and light can be effected by its curvature despite lacking mass (some say it has mass at C, but that would necessitate that it has extremely small mass at rest - which you'd all know better than I lol), then would it not be conceivable that we could 'grab' this 'fabric' and bend it through some means other than mass? After all, what is mass, really? Isn't it just low frequency, highly dense energy, or am I a moron? (Very possible lol). If so, then the mass itself - while causing the curvature - isn't the cause of the gravitational force; the curvature is. Without mass there can be no curvature, but what if that isn't really the case?


[edit on 25-1-2006 by AceWombat04]

Well that's the question isn't it...

In theory, this could be achieved though the Graviton - but only mass seems to emit gravitons (IF this is indeed the case). Until we a) discover the graviton/gravity "carrying" particle/energy and b) discover how to manipulate it and create it, then we cannot affect this "fabric".

Originally posted by Yarium
Well that's the question isn't it...

In theory, this could be achieved though the Graviton - but only mass seems to emit gravitons (IF this is indeed the case). Until we a) discover the graviton/gravity "carrying" particle/energy and b) discover how to manipulate it and create it, then we cannot affect this "fabric".

So, in theory, gravity exerted through gravitons isn't necessarily dependent upon mass? And if it is dependent on mass, are there any theories with respect to the relationship between mass and gravitons? (Or is it simply that the more mass something has, the 'more gravitons' it has)?

I want to go to school really bad lol

AceWombat - the most advanced schooling I've had in this kind of stuff is Grade 12 Physics, and a 1st year basic cosmology course at Carleton University, Ottawa. Everything else, which is almost everything I talk about, has come from INDEPENDANT research.

So don't worry, you don't need schooling to understand all of this. Be a rogue scholar like me! But I won't lie, schooling is able to help you hone your talents, and will show you more of it's ins and outs (the math behind the theories).

In modern physics:

1) A photon does not have mass.

2) Mass is not necessary for momentum, and photons do have momentum, and energy.

3) The above is true even in Maxwellian (pre-quantum) electrodynamics: E&M carries momentum and energy, and the equations of motion for E&M waves in them have no mass-like term.

4) In General Relativity, a photon is affected by both the gravitational field---i.e. local metric---and can be, in itself, a *source* of gravitation similar to the way that mass is.

In GR the gravitational field is caused by the combined stress-energy tensor for all sources: and there is one for mass, and one for electromagnetic fields.

In virtually all practical circumstances other than computations involving the Big Bang or black holes and the like, the energy density of EM fields is so quantitatively infinitesimal compared that from ordinary sources of gravity, i.e. mass, that it is not considered as a significant source of gravitation.

Yes, I am a physicist.

In other words, might it be possible to cause curvature of space-time in the absence of sufficient mass? If space-time is indeed a curved "fabric" (at least conceptually when we visualize it), and light can be effected by its curvature despite lacking mass (some say it has mass at C, but that would necessitate that it has extremely small mass at rest - which you'd all know better than I lol), then would it not be conceivable that we could 'grab' this 'fabric' and bend it through some means other than mass?

This is a mostly experimental question. Firstly, the E&M fields as sources for gravitaiton are already known, but their size is extremely small. It is also presumed that the
fields which make up masses of elementary particles, e.g. color fields of quarks also contribute to gravity, though this unity requires a full "unified theory of everything" to be considered successful, and we do not have this yet. String theory covers attempts in this direction.

From a theoretical point of view, it is conceivably possible to create theories which are mathematically self-consistent, and have additional source terms for gravitation, more complex than Einstein's, which reduce to Einstein's in some certain limits which have been experimentally verified.

However, these have to be verified experimentally to be accepted as physical fact, and so far, none has been, and many alternate gravity theories have been ruled out by more and more precise experimental observations. The new satellite measuring "frame dragging" (a subtle GR effect) might give unexpected results (i.e. not consistent with GR), but I wouldn't bet on it.

In practice we would expect to see some experimental evidence deviation from Einsteinian GR which fits in a consistent pattern to prompt further testing of a theory.

One may consider the dark matter, dark energy and Pioneer 10/11 anomalies in this regard, so I have the feeling that there could be somethign we don't yet understand about gravity yet.

We know already that we don't understand gravity at a quantum level and do not have a satsifactory quantum gravity theory. But if classical GR is really true then not understanding quantum gravity would only mean that we don't know precisely how matter, made up of electrons and quarks, creates gravity at the microlevel. But practically, atomic scale gravity is not important except in exotic black holes, and we already know enough to say what the coupling of stuff to gravity is in the large-scale approximation: it's called "mass" and the big G gravitational constant.

What would be much more interesting, and unlikely so far, is if there are *classical* long-range fields and effects yet to be discovered which are cosmologically important and conceivably could be engineered for useful purposes. Yes, I want warp drive too.

This might explain why we don't have quantum gravity yet: we don't have classical gravity right yet either and we need to get that right first.

The "Heim theory" and its variants recently discussed on this very board about exotic space prepulsion, would be such an example. It's still just science fiction until there's firm experimental evidence.