Massless particles

[elas]

We can have a metre of string or a kilo of jam or the energy of mass, but if we remove the string, jam and mass what do we have the energy of?

[Fred56]

The answer is 42. Or zero.

[insane_alien]

well you don't have anything as you removed everything. you need to have something to get the energy of it.

[swansont]

The question is ill-formed. kilo and meter are units of measurement, but mass is not. You have quantified a length and a mass, but not the energy.

[Country Boy]

To answer the question implied by the title, the only "massless particle" is the photon.

[Severian]

To answer the question implied by the title, the only "massless particle" is the photon.

 

Not true. Gluons and presumably gravitons are also massless.

[thedarkshade]

Well you literally have nothing left. Matter cannot exist without movement, and there is no movement without matter. But this movement to happen you need energy, so matter and energy are basically the same thing. So if you take out matter, you neither have energy!

[insane_alien]

Well you literally have nothing left. Matter cannot exist without movement, and there is no movement without matter. But this movement to happen you need energy, so matter and energy are basically the same thing. So if you take out matter, you neither have energy!

 

and where did you get this idea from?

 

thet would require a preffered frame in which to measure the movement and mean everything that accelerates to zero velocity will disappear. why don't we see things eroding if they accelerate through zero velocity?

[thedarkshade]

and where did you get this idea from?

 

thet would require a preffered frame in which to measure the movement and mean everything that accelerates to zero velocity will disappear. why don't we see things eroding if they accelerate through zero velocity?

I said matter and energy are the same thing based on this:

[math]E=mc^2[/math]

because when an object that has mass reaches the speed of light (just making assumptions!), its mass is completely converted into energy, as is gives the maximum energy containing in its mass.

 

And:

[math]a=\frac{v}{t}[/math]

Zero veloctiy means zero acceleration!

[insane_alien]

1/ i was reffering to the 'matter can't exist without motion' thing

 

2/ full equation is E^2=(mc^2)^2 + (pc)^2

 

3/ massive objects can't reach the speed of light

 

4/ they do not suddenly convert to energy when approaching the speed of light

 

5/ acceleration does not equal velocity over time. it is the differential of velocity with respect to time. a = dv/t is probably what you were thinking of where dv is the change in velocity.

[timo]

I said matter and energy are the same thing based on this:[math]E=mc^2[/math]

The letter m stands for mass, not for matter.

[insane_alien]

add that as a 6th point to why that post was wrong.

[ydoaPs]

because when an object that has mass reaches the speed of light (just making assumptions!), its mass is completely converted into energy, as is gives the maximum energy containing in its mass.

Where did you come up with that? I can think of a handful of ways of converting mass into energy and none of them involve accelerating something to the speed of light.

 

And:

[math]a=\frac{v}{t}[/math]

Zero veloctiy means zero acceleration!

I think you mean [math]\vec{a}=\frac{d\vec{v}}{dt}[/math] which means acceleration is the time rate of change of velocity, NOT velocity divided by time.

 

How does an object initially at rest go from being at rest to moving without acceleration?

[timo]

How does an object initially at rest go from being at rest to moving without acceleration?

Instant transfer of momentum comes to my mind.

[elas]

Swansont

 

The question is ill-formed. kilo and meter are units of measurement, but mass is not. You have quantified a length and a mass, but not the energy.

 

My error, I should have written the energy of a particle followed by what do we have if we remove the mass.

Kilo, meter, mass and energy are units of measurement but the mass and energy of matter are related by Einstein’s equation. I am trying to understand how we can have one without the other.

Take two cars about to collide, remove the mass of one car and leave the energy; what happens when they collide? What takes part in the collision?

In stating that particles can be massless it seems to me that energy ceases to be a unit of measurement and becomes an entity. Either I am misunderstanding ‘energy’ and ‘mass’ or there is something wrong with the term ‘massless particle’.

There is, of course, an ulterior motive, for my question, have you spotted it?

[Fred56]

It depends which view you take. Cosmologists refer to energy, so do particle physicists.

The thing about energy is that it's something mass (particles or matter-waves) can have (due to inertia, let's say), and it can also be something that is a result of matter and charge changing their own moments, and transferring this change to another bit of charged matter. This 'interaction' occurs only between 'charged' bits of matter, and it carries the (quantised) momentum as a kind of wave-packet, with just 2 components (scalars) that rotate (and it has another spin which is independent of the momentum transferred by the particular change in the electron's --atom's-- quantum energy state --the sum of its quantised moments).

 

Ultimately you are able to describe the whole show in terms of this transfer "function": the photons of individual momentum transfer to other bits of matter (which has inertia). It's all to do with harmonic motion and resonance (and allowed and forbidden states). Energy, spin, momentum and charge, are all conserved quantities, and fundamental measurements we have.

Round and around the description goes...

[swansont]

Energy is a property that things have.

 

"We can have a metre of string or a kilo of jam or the energy of mass" is ill-formed, but that doesn't become

 

"We can have a metre of string or a kilo of jam or a joule of energy" because you have to go further and describe what has the energy as that's what you've done before.

 

You didn't say "We can have a metre of length or a kilo of mass" whioch would be the equivalent formation of the statement "a joule of energy." You might also have to describe what type of energy, as we make distinctions between them. (which you would have to do if it turned out that gravitational and inertial mass were different)

 

So, is this anything but semantic games?

[JaKiri]

I am trying to understand how we can have one without the other.

 

E = mc² only applies in very specific circumstances. The correct equation remains E²=m²c⁴ + p²c².

[ydoaPs]

E = mc² only applies in very specific circumstances. The correct equation remains E²=m²c⁴ + p²c².

I wonder how many times he must be told this before he listens.

[JaKiri]

I wonder how many times he must be told this before he listens.

 

If it's finite, then we're getting closer all the time!

[ydoaPs]

We can have a metre of string or a kilo of jam or the energy of mass, but if we remove the string, jam and mass what do we have the energy of?

 

What does this question have to do with massless particles?

[elas]

When I raised a similar question on a QT forum my submissions were transferred to the junk forum.

I did not raise the question on my Particle Structure forum to avoid the possibility of having the whole forum junked. Instead I created this forum to ask the question.

 

In my paper on particle structure I use Hall fractions and a Linear force constant to describe charged elementary particles, two particle composites (mesons) and three particle composites (baryons). I could not include massless elementary particles.

I showed that a conversion constant converted the energy found using the Linear Force formula into the energy found using E=mc>2; so this question was intended to explore energy.

Your replies show that the question is not grammatically correct and that mathematically I have used the Standard model special case formula for E. not the full Standard model equation.

 

This indicates that in order to include massless particles I need to work with the full equation for E.

 

My sincere thanks to all those who, after some struggle; managed to point me in the right direction.

elas

[CPL.Luke]

massless particles always travel at c, because of this they have no inertia (mass). remember mass is just a quantity that describes an objects resistance to force, energy is a quantity describing an objects ability to do work. the two quantities are related but not equivalent. While an objects mass implies an objects ability to do work (as mass can be converted to energy in a number of reactions), an objects energy and ability to work do not imply mass.

 

also the complete formula for the energy of a particle assuming there is no other potential (like the electric potential) would be

 

 

 

[MATH]g_{{{\it uv}}}{U}^{v}{U}^{u}=-{m}^{2}[/MATH]

 

where U^u is the four momentum and tau is the proper time.

[MATH]{m \frac {({{\it dx}}^{u}}{\mbox {{\tt d\/tau}})}}[/MATH]

 

and g_uv is the metric tensor. this of course simplifies to the formula given previously if you are in flat space. however this formula is the one that can be used for any curved space thats found in general relativity. if you are unfamiliar with the einstein summation convention you can place to summation symbols infront of the the equation, one for v and one for u that range from 0-3.

 

as an unrelated note the above equation is how you get gravitational potentials in general relativity, once you include the conservation of energy and angular momentum.

 

 

PS how do you put greek letters into latex?

[elas]

CPL.Luke

 

My aim is to explain the underlying structure that is missing from the Standard model. swansont has transferred this to the madhouse, so it would be improper to continue using my theory on a Classical Physics forum. If you wish to continue please go to:

http://www.scienceforums.net/forum/showthread.php?p=376223#post376223

 

I have not been able to download the latex prog. used on 'scienceforums' sorry, cannot help you with that.

[Fred56]

"Epistemologically, Science in its present state is concerned with the knowledge 'that occurs' and has no way of explaining 'how that occurs'. The end result is that we are left with the same contradictions that Aristotle found, in many new and strange ways --the same problem exists now as it did then.

 

From my perspective, classically speaking, energy is defined as the motion of a body or the potential to move. In that respect, it is created by a force, and is not [itself] a force. However, during a collision, the energy of one particle can transfer to another, and that represents a force. Really, the momentum of one is transferred to the other. It may be arguable, that if energy as an incorporeal entity exists, say as a photon, where the particle nature of the photon is obscure and potentially nonexistent, that this represents a motion as well. Given that each photon has a linear propagation that is incorporeal, i.e., not [particulate] in nature, but an energy that is related to the wavelength, it may be possible that the photon has another internal motion that we are unable to appreciate.

 

The question that evolves is what a particle is? Is it a body, with a physical size and is that a constant? Aristotle argued that substance, as a body, is generated. It follows that if there is a process which generates the body, that the process is a constant, whereas the body may be a variable. The question then becomes, what happens if the body is a minimum? Does the process vanish or does it still exist, and do we now treat the virtual state of a particle in terms of energy alone, since the definition of a particle no longer exists."

--Sean Torrebadal physicsforums.com