Massless Particals--Come now...?

Question

I have a very hard time accepting the concep that anything can exist and be massless. Is energy not simply an aspect of something with mass?

This seems like the kind of thing I hear about black holes having infinate density or being infinately small. Very Very dense and very very small smell far more likely. Just because it is beyond our ability to meaningfuly measure doesn't make it infinate.

How does something exist if it isn't there?

That was "seem", not "smell"--Brain misfired, sorry...

Answer 1

Energy and mass are interchangeable but they are not the same thing. It might help to think of mass as 'frozen energy': if the energy is released some or all of the mass disappears - this is how nuclear reactors, bombs and stars work.

Black holes don't have infinite density, in fact the more massive they are the less dense they get. You're thinking of the singularity at the center which is so small and dense that it is beyond current physics to describe. Infinities can add up to finite quantities, believe it or not. My favorite infinite series is the endless list of the numbers 1/2 + 1/4 + 1/8 + 1/16 + 1/32 + 1/64..., each fraction half the previous one 'ad infinitum' and all adding up to exactly 1.

Answer 2

Actually, the density is regarded to be infinite, based on the math. As is always the case with scientific theories, they are always regarded as valid until the contrary is proved and updates made. Theories are often borne and brought into the scientific community in a form far different that laypeople see in Discover or Scientific American. I think Nature publishes papers in full, but am not certain.

Anyway, once complete they are studied and reviewed by peers from all over. It is then that challenges are made and then people go away for a while and work on disputing the claims, and so on until such time that any inconsistencies are dealt with to such a degree that the 'laws' become more and more solidified, but they are rarely ever regarded as 100%. Such is the case with black holes and infinite densities that you mentioned.

Ok, now the main part of your question. Sorry for going about this in this way, but at any rate, there are various weird things in physics......such as velocities that travel faster than the speed of light, how solid objects have a certain probability of passing thru other solid objects and reappearing in tact on the other side.....and massless particles.

Photons have zero REST mass, but 'in flight' they have mass....small for sure but it is indeed nonzero. Other particles are thought to be of zero mass because of the other properties they have. Just because a particle does not have mass doesn't mean it's not there. Einstein showed us all the equivalence between mass and energy, but I'm talking about his *total* energy, not the E = mc² eq'n. That is a fair trade-off. But even if you were looking at the equation I just gave you, you cannot interpret that in such a simplistic way as to assume that if m = 0 then E = 0.

There are subtleties going on in addition to what I've mentioned, as is always the case with details associated with scientific theories like this. It take additional understanding in some cases to grasp what the author(s) intend with the ideas presented. Sometimes they are sensible, other times they are not. physics (and math) has numerous instances where someone tried something that was not valid in the math-sense, or the physics sense, but it led to a completely valid result. One case is in thermodynamics, and I forget just now, but I *think* it was Van Der Waals when he was playing with ideal gas laws, and he pulled some nonsense math move that was so totally not acceptable, but it led to a completely valid and solid result.

It's similar to....and I'm sorry if this reference is nebulous, but if you take i^i....an imaginary number raised to another imaginary number......the result is totally a real number. Two number that don't really exist.....yet when combined in this way give a result that is a real number. It's way cool, but anyway, that's an example of what I'm talking about.

There are math proofs that make no sense because of this. They defy logic or common sense, but they work, and are used, and often times it is years, or decades later until they make sense.

So........massless particles.....sure....look a little beyond your senses. there is a LOT going on beyond what you can see and touch, etc. This is where the beauty and creativity comes to play in this field. Sometimes you can happen upon great and grand ideas, and other times they are stepping stones, but nevertheless it is great when they happen.

Hope this helps.

Answer 3

It is easy to cop out and say E = mc^2, but there are some real problems with this equation. First, energy is the capability to do work or cause a change. In other words, energy is just a potential for work, it is not the force that does the work. To be sure, when a force is applied and work is done, energy is expended and the potential is realized.

Second, as energy is a potential, claiming PE = mgh is potential energy (PE) is a misnomer. If enything PE is a potential potential (capability) to do work. This follows because energy is a capability, which is already a potential, to do work, not the actual doing of the work which is done by applying a force of some sort. Work is not done by applying energy, but energy (a capability for work) is expended.

Bottom line, energy and force are related, but they are not the same thing. Energy is a capability for work and force is the driver for doing that work. The so-called work function W = Fd, where F is a force acting in the direction of some distance d is a prime example of the relationship between energy (called work W) and the force (F) applied to do that work.

Now, understanding that energy and force are not the same thing, we can see that work (also called energy) is just the realization of some change (in position or chemical change) by applying a force (mechanical, electrical-magnetic, etc.) to something. That something is the mass you are looking for. So, by applying a massless force to a mass, energy is expended, but energy has no mass of its own.

For example, consider the compressed spring. When pushing a spring to compress it, we apply a force F = k(del x) which is stored in the spring with k constant and compressed del x.

Most textbooks will say energy (potential energy) is stored during compression, but that is really not the case. What is stored is a force. How do we know this? Because while compressing that spring with your hand, there is an equal and opposite force pushing back on your hand. Not an equal and opposite energy...an equal and opposite force according to Newton.

If that spring (a mass) is let go, it will decompress (expand) because of the stored force acting on its mass. Thus, as it expands that mass is moved some distance (d) and, through the work function, E = W = Fd; and energy (kinetic in this case) is expended in that expansion.

Thus, energy is just a potential for work or causing a change (which is a form of work). But a force must be applied to expend that energy and as it is applied, it is used up. On the other hand, energy cannot be created or destroyed (used up). It can only be converted from one form of energy to another. But again, we are talking about a capability for work, not a thing; not a mass.

To answer your question: energy is just a potential for doing work. You are full of energy, you are full of a potential for doing work. Clearly, there is something that gives you that potential. It's called energy. And when you move your arms and legs to move something (the mass), you realize that potential by exerting force and expending energy.

Answer 4

you must first understand that physics is mankind's attempt to make mathematical sense of the universe. therefore, what makes mathematical sense deosn't necessarily make sense in the real world. infinite or zero values applied to certain physical concepts are merely attempts to make them make theoretical sense. i agree that it is impossible to imagine a black hole with zero radius and infinite mass, but these were the concepts that put man on the moon and invented the atomic bomb, so something must be right! at least in a theoretical sense...