Friction, resistance

[HydrogenBond]

If we could reach absolute zero we would know for sure. All of nature appears to reach a certain steady state dependant on temperature. As we approach absolute zero there is a ground state for the electrons. There should not be a ground state for a perpetual balanced system unless it was based on temperature of background energy.

[Qfwfq]

There should not be a ground state for a perpetual balanced system unless it was based on temperature of background energy.

QM predicts the ground state of atoms without temperature. The effect of temperature is to keep atoms out of their ground state, the higher the temperature the less of them will be in the ground state.

 

There's no need for the background energy for atoms to have a ground state.

[HydrogenBond]

This does not make sense. There is a gap between stable ground states. There is an energy quanta range within each stable state. It is like dragging a heavy object up a sandpaper hill. On tugs on the rope, it just stays there then jumps. But there is still potential energy within the tug between stable jumps. The electrons to not censor every quanta given to them and only cherry pick what they want. Although only certain cherries make it obvious there was a change. For example, vibrational and rotational energy levels of molecules make the intermediate states far more obvious. With the hydrogen it might only be noticed if the wave function was measured for density. If still fills the state but the probability of findng the electron on one particle spot of the wave would probably change.

[Mercenaryend]

the only prepetual motion that exist is the universe.

[questor]

in assessing friction, i assume we mean the colliding with particles which eventually slows the progress of an object. what about gravity? will it not also eventually slow the progress of an object in an orbit? what supplies the energy for orbits? every atom in our body and in the universe is orbiting . the atoms in our body are exposed to gravity. why does gravity not slow the orbiting? this orbiting is not occurring in empty space, but in a human body occupying many different altitudes and attitudes. where does this energy originate?

[CraigD]

what about gravity? will it not also eventually slow the progress of an object in an orbit?

As precisely as we can measure, gravitational force does not reduce the sum of Kinetic Energy and Gravitational Potential Energy of falling or orbiting objects. For any orbit other than a perfectly circular one, the orbiting object constantly exchanges KE and GPE, so gravity does slow it, but then speeds it up again, without frictional losses.

what supplies the energy for orbits?

The initial velocity and position of the bodies of the system supply the energy. Unlike an object like a car, which constantly looses useful energy to rolling and air drag, and must have the lost energy constantly replaced or quickly roll to a KE=0 stop, orbiting objects in the vacuum of space don’t require any energy input to sustain their motion.

every atom in our body and in the universe is orbiting

Essentially true, but the force (or interaction, to speak QM-correctly) producing these orbits is predominantly electromagnetic. Gravitational force is a staggering 10^38 times weaker than electromagnetic force, so only becomes significant in systems where electromagnetism, which, unlike gravity, can be both attractive and repulsive, cancels itself out.

[cwes99_03]

What about liquids, are you thinking in terms of friction with liquids as well?

 

I sat through a colloquia a few years ago when a professor from one of the state universities in one of the Carolinas presented some in vivo experiments dealing with friction and liquids and stuff like that. One of her conclusions was that friction wasn't actually the result of any actually touching or electric field interaction. I found her research to be lacking in depth and clarity.

 

Oh and what about viscosity? Is it a form of "friction"?

[goku]

seems to me that there is friction, resistance even in space. there is dust in space, radiation, light.

there is an exchange of energy between any two particles that collide.

[CraigD]

seems to me that there is friction, resistance even in space. there is dust in space, radiation, light.

there is an exchange of energy between any two particles that collide.

You are correct. However, the effect is so small as to be practically negligible. The kinetic energy of even the smallest observable object in space (eg: asteroids, kuiper objects), let alone a planet, is so great that the transfer of their kinetic energy due to collisions with interplanetary dust and gas won’t significantly effect their orbits for many billions of years.

 

The effect of gravitational interaction between non-colliding bodies (eg: comets passing near planets, and the cumulative effect of this on the planets) can be dramatic. Small bodies can be caused to strike the sun or the planets, or ejected from the solar system. There’s evidence to support the theory that this interaction can, in complicated ways, increase the stability of orbital systems, mostly in the form of the amazing order found in the moon and ring systems of the large planets.

 

Despite the availability of powerful new computer techniques, the motion of the solar system, and, on a larger scale, the Milky Way and other galaxies, retain many mysteries. These systems are complicated, not lending themselves to simple analogies such as the gradual loss of kinetic energy due to friction that we see in everyday objects like pendulums and spinning bicycle wheels.