light = energy, energy = mass, so light = mass ?

[origin]

My cerebral cortex begins to ache when I try to conceive the image of nothingness,which begat the Big Bang,and the universe expanding into this infinite nothingness,only to reach some outward point where the energy expanding it can no longer sustain the outward motion,and the whole thing begins to collapse upon itself and condense until it reaches critical mass and explodes again,as it has done throughout infinite time.Simple human.Simple brain. :|

Well then I have some good new. It now appears that the universe will expand forever - at an increasing rate no less. There you go headache relieved.

 

[darkmatter4brains]

My cerebral cortex begins to ache when I try to conceive the image of nothingness,which begat the Big Bang,and the universe expanding into this infinite nothingness,only to reach some outward point where the energy expanding it can no longer sustain the outward motion,and the whole thing begins to collapse upon itself and condense until it reaches critical mass and explodes again,as it has done throughout infinite time.Simple human.Simple brain. :|

The Universe wasn't created out of nothing and it's not expanding into nothing. It only seems like nothing, because we have practically no concept of anything beyond the Universe - it's totally outside our experience.

With that said, some of the latest theories like M-theory do have ideas of what the Universe was created out of - in that theory, higher dimensional membranes collided to create the Universe.

I personally think M-Theory is wrong, but eventually some theory will come up with a "something" to replace the "nothing" mentioned above.

 

[origin]

but eventually some theory will come up with a "something" to replace the "nothing" mentioned above.

Maybe, maybe not. Let the data lead to the conclusions, I find it best to not impose my preconcieved limits on the universe.

 

[Astro_Robert]

Ramparts,

Thanks for the reply. I think I did not explain where I was going adequately, but your answer covers it. My intention was that photons from the very early universe have been carried away from us by the speed of light and by the expansion of space itself, and are therefore unobservable, although they would remain in the universe. ie that there are many primordial photons which we cannot observe. I hadn't considered the implication you mentioned that if such a photon is beyond our observation using light, then how could someone claim we would feel gravity form them.

Since matter must travel less than c, and photons travel at c, then there must be a large number of photons that are more distant than the most distant matter. These photons emitted over more than 13 BY should exert some gravitational influence which would be expansionist in nature since they are farther away than the matter.

Again, at the time I thought of this I decided that gravitational interactions of such distant photons would be negligible, I was just curious if anyone had pursued this line of reasoning towards explaining some of the accelerating expansion.

 

[darkmatter4brains]

but eventually some theory will come up with a "something" to replace the "nothing" mentioned above.

Maybe, maybe not. Let the data lead to the conclusions, I find it best to not impose my preconcieved limits on the universe.

Well, if the Universe was truly born out of nothing, there would be no data to show that. Nothing should NOT produce data. It would be the complete absence of data if anything. In addition, the statement "let the data lead to conclusions" isn't always the best way to look at things, as some of the biggest discoveries in science came about due to imagination first - the data came much later as a confirmation of theory. As Einstein said, sometimes, "imagination is more important than knowledge." With that said, I think the LHC may be an area where the data comes first, and forces us into a mode where we have to come up with answers later.

Anyhow the point of my post is that the idea of the Universe being born out of nothing IS a preconcieved limit. The human mind seems to like to deny the existence of things that it cannot fathom or cannot picture. (I mean, that's the ultimate limit you can put on something - that it does not even exist.) You can see this throughout the history of physics as well. Just because we cannot conceive of something existing outside the Universe, doesn't mean there's not something there. In my mind, just saying it is nothing is a cop-out and a laziness in imagination. Having an open mind that it's NOT nothing, is going past preconcieved limits that the human mind is apt to fall into. In addition, since all the latest theories are positing there was "something" (like M-Theory's N-d membranes) before the Universe, to imply it was born out of nothing, is to ignore mainstream physics. Anyhow, just my opinion ....

 

[Mee_n_Mac]

Who says the Universe was "begat from nothing" ? Last I knew the BB had the Universe starting from a singularity (or as near to it as possible) and then expanding. All the energy/mass we have now was there at the moment of the BB. Now where that energy/mass came from is an unanswered question but to say prevailing cosmology has the Universe coming from nothing is not true (so far as I know).

 

[dryson]

2nd of 3 crossposts deleted.

 

[MeteorWayne]

Man, you can distort anything so it no longer makes sense. You should have left the statement from the article alone. It made sense back then.

 

[Tritium]

Light has mass, just not rest mass. If it had any finite rest mass at all, it would gain infinite mass and require infinte energy to get it to light speed.

This is interesting because if light did not have any mass then how would it achieve light speed velocities?

Here is an article that covers photons and gravity which seems to fit in with the discussion.

http://csep10.phys.utk.edu/astr162/lect ... khole.html
Here is a few paraphrases from the article:

Photons always travel at the speed of light, but lose energy when travelling out of a gravitational field.
The stronger the gravitational field, the more energy the photons lose.
which is built on the principle that the speed of light in a vacuum is constant.

Now the main parts that I read from this article were that when in a gravitational field the photon maintains a light speed velocity outside of the gravitational field the photon loses energy and when in a stronger gravitational field the photon also loses energy. The article also states that the speed of light is a constant speed when in a vacuum.So somewhere in this mix of gravitational wavelengths interacting with the photon there is an interaction between the two that creates the velocity of light speed. Otherwise if this were not fundamentally true then when the photon left a gravitational field or encountered a stronger gravitational field the photon should remain in the same phase but it doesn't So when we put the paraphrases together from the article it should actually read:

Photon's will always travel at the speed of light in a vacuum where gravity is present and causes an equal reaction upon the internal operations of the photon to force the photon to obtain a speed of light velocity. The photon will lose energy and not travel at the speed of light when traveling outside of the gravitational vacuum or when the photon encounters a stronger gravitational field in a vacuum the more energy the photon will lose relative to the same manner that the photon loses energy when it is outside of a gravitational vacuum thus causing the photon to dissipate or become invisible.

A gravitational field in a vacuum is the constant that sets the photon's speed of light velocity not that the speed of light in a vacuum is the constant.

The question is though if a photon is transformed into a redshift phase because of not being inside of a gravitationally vacuumed field or encounters a stronger gravitationally vacuumed field would and becomes invisible could the photon be changed back to it's phase of radiation by subjecting it to the appropriate wavelength at it's equilibrium? Could this be what dark matter is? Light that has passed out of the gravitational vacuum becoming invisible?

The photon,as we ubiquitous humans have decided to name it is something which pisses us off because it behaves as both a particle having mass,and a wave-like energy.I can only say that I can see that we are missing large pieces of the puzzle,when it comes to understanding the laws of physics,and our model is wrong somehow.Gravity and light are needing better instrumentation and inquiry to discover their true natures.We are not there yet.I pray for a new Newton and a enigmatic Einstein to come forth,with evolved brains,and show us all how simple it is on their i-pods.

 

[killium]

If it (the universe) came from something, then where does that something came from ? With this, we're only pushing the problem a step away. If we try to go back to the "true" begining, we have to admit that the universe came from nothing.... or it has always been... I don't think there is an other possibility.. ?


ok!, solar sails work because photons have momentum ? Did those photon imparted a "recoil" when they were ejected from thier source ? Cause if not, it would mean that we could sail while bringing with us the light source, impossible no ? That is like trying to fly by holding up the handles of the bucket in which we are seating. Something doesn't jive here, or here is our reactionless drive.... ?

Last point, any matter submitted to a gravity field will see its "internal clock" slows down. If the internal clock of a photon is slower than ours', we would see it as redshifted (cause there is a relation between frequency (wavelength) and "speed of time"). A photon that was emitted earlier than another one would appear to us as more redshifted than the other one because it passed a longer time in a gravity field that is slowing its clock. So the farther the photon's source from us, the more redshifted it appears. Just thinking outloud....

 

[Tritium]

If it (the universe) came from something, then where does that something came from ? With this, we're only pushing the problem a step away. If we try to go back to the "true" begining, we have to admit that the universe came from nothing.... or it has always been... I don't think there is an other possibility.. ?


ok!, solar sails work because photons have momentum ? Did those photon imparted a "recoil" when they were ejected from thier source ? Cause if not, it would mean that we could sail while bringing with us the light source, impossible no ? That is like trying to fly by holding up the handles of the bucket in which we are seating. Something doesn't jive here, or here is our reactionless drive.... ?

Last point, any matter submitted to a gravity field will see its "internal clock" slows down. If the internal clock of a photon is slower than ours', we would see it as redshifted (cause there is a relation between frequency (wavelength) and "speed of time"). A photon that was emitted earlier than another one would appear to us as more redshifted than the other one because it passed a longer time in a gravity field that is slowing its clock. So the farther the photon's source from us, the more redshifted it appears. Just thinking outloud....

Is it particle or wave or both?I say both-an entity which crosses boundaries and displays behaviors of both mass and energy. :shock:

 

[origin]

ok!, solar sails work because photons have momentum ? Did those photon imparted a "recoil" when they were ejected from thier source ?

yes

Cause if not, it would mean that we could sail while bringing with us the light source, impossible no ?

impossible, yes

 

[Tritium]

ok!, solar sails work because photons have momentum ? Did those photon imparted a "recoil" when they were ejected from thier source ?

yes

Cause if not, it would mean that we could sail while bringing with us the light source, impossible no ?

impossible, yes

We need more than yes and no answers in here.
I think origin was trying to figure out if we could continue to "push" a photon wind on our light sail in the vast distances between stars by providing our own source of photons.To me,this seems reasonable.

Please enlighten us as to why you say "NO".

 

[MeteorWayne]

No, the poster specifically said bringing his light source with him. That is a clear and undeniable NO.

 

[origin]

We need more than yes and no answers in here.
I think origin was trying to figure out if we could continue to "push" a photon wind on our light sail in the vast distances between stars by providing our own source of photons.To me,this seems reasonable.

Please enlighten us as to why you say "NO".

First I can assure you it was not orgin that asked this.

Is there a 'recoil'? I answered yes. So that means that momentum backwards equals the momentum forward - no net acceleration.

I suppose you could have some sort of supper collimated laser that continues to send a stream of photons to the solar sail for years and years - sort of like the classic A Mote in God's Eye, but good luck stopping. :shock:

 

[MeteorWayne]

Another thread on the verge of finding another more suitable home.

 

[origin]

Another thread on the verge of finding another more suitable home.

Well, it didn't have a very promising start to it...

 

[Mee_n_Mac]

If it (the universe) came from something, then where does that something came from ? With this, we're only pushing the problem a step away. If we try to go back to the "true" begining, we have to admit that the universe came from nothing.... or it has always been... I don't think there is an other possibility.. ?

Present cosmology doesn't really address the question of what came before the Big Bang. While people certainly muse over it, there isn't an accepted theory. The best answer is ... I don't know.

ok!, solar sails work because photons have momentum ? Did those photon imparted a "recoil" when they were ejected from thier source ? Cause if not, it would mean that we could sail while bringing with us the light source, impossible no ? That is like trying to fly by holding up the handles of the bucket in which we are seating. Something doesn't jive here, or here is our reactionless drive.... ?

Yes the photons have momentum and did/do impart a recoil when they leave their source. Thus, as you've figured out, you can't carry your source and a sail and have it work.

Last point, any matter submitted to a gravity field will see its "internal clock" slows down. If the internal clock of a photon is slower than ours', we would see it as redshifted (cause there is a relation between frequency (wavelength) and "speed of time"). A photon that was emitted earlier than another one would appear to us as more redshifted than the other one because it passed a longer time in a gravity field that is slowing its clock. So the farther the photon's source from us, the more redshifted it appears. Just thinking outloud....

The problem with your formulation is that by the time we get to see the photons, they have all traverse the same gravitational potential. In the case where there gravitational field doesn't remain constant as the photons spew forth from it (or if we change our position within the field) ... then you'd see lesser or more redshifted photons, depending on which way the gravity went (increased or decreased).

 

[csmyth3025]

I started reading this thread because I thought it would be pretty hard to get off-topic with such a restrictive question as the title suggests. I seem to have underestimated my fellow posters in this regard.

On the topic itself I rely on a simplified explanation contained in the Wikipedia article on mass-energy equivalence, part of which follows:

In relativity, all energy moving along with a body adds up to the total energy, which is exactly proportional to the relativistic mass. Even a single photon, graviton, or neutrino traveling in empty space has a relativistic mass, which is its energy divided by c². But the rest mass of a photon is slightly subtler to define in terms of physical measurements, because a photon is always moving at the speed of light—it is never at rest.

If you run away from a photon in the direction it travels, having it chase you, when the photon catches up to you the photon will be seen as having less energy. The faster you were traveling when it catches you, the less energy it will have. As you approach the speed of light, the photon looks redder and redder, by Doppler shift (the Doppler shift is the relativistic formula), and the energy of a very long-wavelength photon approaches zero. This is why a photon is massless; this means that the rest mass of a photon is zero.

On the question of the "closed bottle" thought experiment described in a previous post, I again refer to the same Wikipedia article on mass-energy equivalence - specifically, the following portion:

The concept of mass–energy equivalence connects the concepts of conservation of mass and conservation of energy, which continue to hold separately. The theory of relativity allows particles which have rest mass to be converted to other forms of mass which require motion, such as kinetic energy, heat, or light. However, the mass remains. Kinetic energy or light can also be converted to new kinds of particles which have rest mass, but again the energy remains. Both the total mass and the total energy inside a totally closed system remain constant over time, as seen by any single observer in a given inertial frame. In other words, energy cannot be created or destroyed, and energy, in all of its forms, has mass. Mass also cannot be created or destroyed, and in all of its forms, has energy. According to the theory of relativity, mass and energy as commonly understood, are two names for the same thing, and neither one is changed or transformed into the other. Rather, neither one appears without the other. Rather than mass being changed into energy, the view of relativity is that rest mass has been changed to a more mobile form of mass, but remains mass. In this process, neither the amount of mass nor the amount of energy changes. Thus, if energy changes type and leaves a system, it simply takes its mass with it. If either mass or energy disappears from a system, it will always be found that both have simply moved off to another place.

and the following subsequent portion:

According to E=mc2, no closed system (any system treated and observed as a whole) ever loses mass, even when rest mass is converted to energy. All types of energy contribute to mass, including potential energies...

I believe that Origin responded to this thought experiment as follows:

That is actually sort of correct. If there was a magic bottle that could hold positrons and electrons and was also able to hold the resulting photons that result from anihilation, then that is just what would happen, you would have the mass from the particle pairs and after the anihilation you would have a bottle full of energy and the weight would decrease due to the disapearence of all of the particles...

If I understand the Wikipedia article correctly, it's saying the the bottle full of energy would weigh exactly the same as the bottle full of electrons and positrons. Am I mis-reading the article or is it mis-stating the facts?

Chris

 

[ignorant]

Here is a question, if photons release heat energy, they should lose momentum and drop below the speed of light, yet they are capable of travelling at infinite distances, also if they are pure energy, they should be able to pass through everything without being disturbed, yet they hit a wall and stop dead in their tracks, this implies they in fact take a space and must have a mass does it not? I know they aren't fully understood in physics but isn't the shear existance of them juxtaposed to how they act in nature?

 

[ramparts]

I'm not sure what you mean by photons releasing heat energy - photons don't naturally give off any energy except under certain circumstances - but when a photon loses momentum, it doesn't slow down, but rather its wavelength gets longer. This is because momentum in special relativity is more complicated than the everyday momentum, which is just mass times velocity. Momentum is really linked most closely to energy, so when a photon loses momentum, it loses energy. This is equivalent to having a longer wavelength while still moving at the speed of light.

As for photons stopping, think of it like this: if light runs into a wall, then each of those photons is pretty likely to run into an atom in that wall. When a photon hits an atom, the atom absorbs the photon's energy (though it often re-emits another photon in response - that's why most walls reflect light when you shine a flashlight on them!).

 

[ignorant]

Ok the wavelength and reduction of energy makes sense. I was referring to sometihng similar to a laser, where if my understanding is correct, is just a condensed beam of photons. Since a laser can burn through stuff it would imply that they give off heat energy when they hit something, yet when you shine a light on something it reflects back at you so some of those photons would have to lose energy in the process I would think. But as you explained, the wavelength changes due to the loss of energy which gives us the colors we see.

Now, I still don't quite understand how an object with no mass can "hit" an object, or is it that they give off a small portion of their energy as they pass through, albeit on an altered course until they have given off so much energy that their wavelength is no longer detectable, but still there.

 

[ramparts]

What happens in a collision is conservation of momentum - and even though photons don't have mass, they do have momentum. And they also have spatial positions (subject to uncertainty and all that), so they certainly can collide with other things as well as any other particle can.

 

[Mordred]

personally think M-Theory is wrong, but eventually some theory will come up with a "something" to replace the "nothing" mentioned above.

When I was a high school kid, I asked a question that we spent days on trying to answer.

If everything must have a beginning and an end what is the beginning of the Universe.

The only answer we could come up with was
"nothing +nothing =something"
So you can imagine my amusement seeing articles that describe similar ideas such as the M theory

 

[origin]

Ok the wavelength and reduction of energy makes sense. I was referring to sometihng similar to a laser, where if my understanding is correct, is just a condensed beam of photons. Since a laser can burn through stuff it would imply that they give off heat energy when they hit something, yet when you shine a light on something it reflects back at you so some of those photons would have to lose energy in the process I would think. But as you explained, the wavelength changes due to the loss of energy which gives us the colors we see.

Now, I still don't quite understand how an object with no mass can "hit" an object, or is it that they give off a small portion of their energy as they pass through, albeit on an altered course until they have given off so much energy that their wavelength is no longer detectable, but still there.

A laser is a large number of photons in a narrow beam. These photons are absorbed by the electrons in the material they are hitting. If we are talking about a high energy beam then the photons can actually cause the electrons to gain enough energy so that they fly off of the atoms. This will cause the stricture of the material to break down. So what you are doing is vaporizing a hole in the material by ionizing the material into a gas.