° of energy..

[Mareks J.]

How hot can be pure energy?

[andrewcellini]

energy is a property not a substance.

[Phi for All]

energy is a property not a substance.

 

... so there can never be pure energy (sorry, I wasn't sure that was clear). You can't separate the energy from the object it's a property of.

[DevilSolution]

I imagine that supernova's are quite hot. Obviously not energy persay but its disperses plenty of it very quickly.

[swansont]

Hot is a property or condition. Heat is energy being transferred owing to a temperature difference.

[MigL]

Energy can be expressed as a temperature.

[swansont]

Energy can be expressed as a temperature.

No, not really. Temperature tells you something about energy - average vibrational KE - but the reverse isn't true.

[MigL]

So why can't I express the energy of a particle by its equivalent temperature ?

Its done all the time, in colliders as well as descriptions of the early universe.

Please elaborate Swansont.

[ajb]

So why can't I express the energy of a particle by its equivalent temperature ?

You can always use Boltzmann's constant to go between the units of energy and temperature. However, one would have to take care and it may not be possible to understand the 'temperature' as the temperature as understood in the kinetic theory of gases.

[studiot]

 

 

MigL

Energy can be expressed as a temperature.

 

 

Sometimes yes but only indirectly.

 

Consider first my shed wall.

 

Today it is 300^oK inside and outside the shed. The wall temperature is 300^oK

Tonight the same wall, inside and outside temperatures will be 285^oK.

The wall hasn't changed its KE or its PE but it has lost some heat content.

 

So in that sense the temperature is an indication (measure even) of the energy of the wall.

 

But consider a different wall separating a furnace at 3000^oK from the outside at 300^oK.

This wall contains cooling pipes and much coolant flows through these, carrying away energy and maintaining the wall temperature.

 

In this case the wall temperature is not a measure of energy and perhaps not even a good indicator.

The mass flow and difference in temperature between inlet and outlet of the coolant is however.

[DrP]

Don't think you need the 'degree' symbol with Kelvin Studiot.. it's just 0K or 273K

[swansont]

So why can't I express the energy of a particle by its equivalent temperature ?

Its done all the time, in colliders as well as descriptions of the early universe.

Please elaborate Swansont.

 

A 1 kg ball moving with a speed of 1 m/s has half a Joule of translational KE. But it doesn't have a temperature based on that rolling. kT for that energy is about 10^22 K.

 

Temperature assumes an ensemble of particles that have reached a steady state and exhibit a Maxwell-Boltzmann distribution of speeds. The description of colliders assumes that you had such an ensemble, because in the early universe you did.

You would need to assume you had billions of 1 kg balls, elastically colliding , with an average speed of 1 m/s to assign a temperature to that.

[MigL]

I see.

I'm taking a narrow view ( from kinetic theory ) and trying to apply it generally ( where it doesn't necessarily work ).

Thank you, gentlemen.