What is matter?

?

[kitaristi0]

Could you elaborate please?

[PairTheBoard]

M = E/c^2

PairTheBoard

[mosquito]

Thought you were asking "what is THE matter?"

lol

[K C]

I would say something that has mass, but that's probably going to lead to a very long and bitter discussion /images/graemlins/smile.gif

KC

[mosquito]

[ QUOTE ]
Could you elaborate please?

[/ QUOTE ]

This is Math, Science and Philoshophy. I will not
say how math or science would view the question,
but philosophy MIGHT say -

"It matters not"

[vic1225]

By definition matter is something that occupies space. Speaking in physics definitions, it is something that has mass and exists as a solid, liquid, plasma. What is more interesting is antimatter, which is the opposite of matter, another post for a another day.

[Eihli]

What is mind? No matter. What is matter? Never mind. Ha Ha Ha Ha Ha!

[fnord_too]

Whatever it is, on the sub atomic scale, it's damn weird IMO.

[MelchyBeau]

[ QUOTE ]
it is something that has mass and exists as a solid, liquid, plasma

[/ QUOTE ]

you forgot gas and Bose-Einstien Condensate.


However, we consider a proton, nuetron, electron, etc... to be matter and they don't exist in those states. those are states that a set of atoms can be in.

The official definition is something that occupies space and has a mass.

Melch

[fnord_too]

[ QUOTE ]
[ QUOTE ]
it is something that has mass and exists as a solid, liquid, plasma

[/ QUOTE ]

you forgot gas and Bose-Einstien Condensate.


However, we consider a proton, nuetron, electron, etc... to be matter and they don't exist in those states. those are states that a set of atoms can be in.

The official definition is something that occupies space and has a mass.

Melch

[/ QUOTE ]

I thought electrons were point particles, so they did not occupy space. (It's been a long time since I thought or studied anything about sub-atomic physics, so I could be completely off base.)

Also, don't photons have mass? (They are affected by gravity, but maybe it is just space that is affected by gravity so that geodesics change but the photon is in fact massless). For some reason I am thinking that some theories have energy and mass almost married (that is, something cannot have energy without mass). I don't know, I never really learned that stuff to the point of deep understanding, so it has blurred in my mind.

[MelchyBeau]

[ QUOTE ]


I thought electrons were point particles, so they did not occupy space. (It's been a long time since I thought or studied anything about sub-atomic physics, so I could be completely off base.)

Also, don't photons have mass? (They are affected by gravity, but maybe it is just space that is affected by gravity so that geodesics change but the photon is in fact massless). For some reason I am thinking that some theories have energy and mass almost married (that is, something cannot have energy without mass). I don't know, I never really learned that stuff to the point of deep understanding, so it has blurred in my mind.

[/ QUOTE ]

photons do not have mass. It is also a gauge boson. Gauge Bosons aren't considered matter. When you get into particle physics many lines get blurred. I.E. whether or not something is a wave or a particle.

It is enough to make your head spin, but spin up or down is the question /images/graemlins/wink.gif

Melch

[PairTheBoard]

MelchyBeau --
"photons do not have mass."

How is it that light from the sun can be used to push a solar sail? When photons hit the sail they must impart, what? Momentum? How does a massless entity do this? Aren't mass and energy two forms of the same thing according to Einstein's equation? So isn't a photon the energy form of a mass equal to the photon's energy divided by the speed of light squared?

Just asking.

PairTheBoard

[MelchyBeau]

the momentum of a non-relativistic object is p=mv.
for a photon p=h(lambda). Lambda is the wavelength of the photon. Your question isn't an easy one to answer. You have to think outside of your observations. Momentum that exists in our non-relativistic viewpoint is different than momentum at relativistic speeds.

Anyways to answer your mass question quickly, a photon travels at the speed of light, thus it can't have a mass.

E=mc^2 is an equation for an object at rest. when looking at the energy for an object in motion the equation becomes

E=mc^2/sqrt(1-v^2/c^2)

the energy of a photon is

E=hf.

so we can take this equation E=mc^2 and this last one, thus

E=hf=mc^2, thus m=hf/c^2

so in other words I lied to you, sorta. photons have no rest mass, but they do have a relativistic mass.

Did I confuse you, if I did, blame Einstien and not me.

If I did not, chew on this. Gravity bends light.

Melch

[PairTheBoard]

Melch --
"Gravity bends light."

See. There's another one.

PairTheBoard

[Chairman Wood]

The authority = Me.
Matter is strictly defined as " Anything that has mass and takes up space."

[pzhon]

[ QUOTE ]
photons do not have mass.

[/ QUOTE ]
A photon has zero rest-mass, but a nonzero relativistic mass, proportionate with its frequency.

[Dov]

[ QUOTE ]
A photon has zero rest-mass, but a nonzero relativistic mass, proportionate with its frequency.

[/ QUOTE ]

Thank You!

Now it makes sense. (I think.) LOL /images/graemlins/cool.gif

[pzhon]

[ QUOTE ]
[ QUOTE ]
A photon has zero rest-mass, but a nonzero relativistic mass, proportionate with its frequency.

[/ QUOTE ]

Thank You!

Now it makes sense. (I think.) LOL /images/graemlins/cool.gif

[/ QUOTE ]
You are welcome. You should be aware that there are conflicting conventions within physics. Some physicists don't like using relativistic mass at all, and indeed, that seems to be the norm. However, this is just a convention for communication, and in expositions for nonphysicists, they usually use relativistic mass.

As a mathematician, I dislike many of the physicists' conventions. I think keeping relativistic mass in mind is more helpful for many purposes.

/images/graemlins/diamond.gif A perfectly mirrored box full of light has a higher inertia and a higher weight than when it contains no light. You can feel the effect of gravity on the photons because there will be a greater light pressure on the bottom of the box than on the top, as space-time geodesics hit the bottom of the box slightly more frequently than they hit the top. How much more massive does the full box seem? The added mass is the relativistic mass of the light.

/images/graemlins/diamond.gif Consider a spacecraft accelerating to relativistic speeds. The relativistic mass can't increase without outside help, so your spacecraft needs to have a high fuel:nonfuel ratio to achieve a high gamma, even with a perfectly efficient engine. That makes it clear why you may want to use a light sail.