An object above absolute zero radiates energy

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Discussion Overview

The discussion revolves around the concept of energy radiation from objects above absolute zero, particularly focusing on how the motion of the Earth affects the wavelengths of radiation emitted. Participants explore the implications of relative motion on radiation and temperature, as well as the relationship between kinetic energy and radiation.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • One participant suggests that if the Earth were not moving, it might radiate energy in different wavelengths, questioning the relationship between speed and radiation.
  • Another participant argues that the speed of an object does not affect the amount of infrared radiation emitted from bodies, emphasizing that energy expenditure remains constant regardless of Earth's motion.
  • A participant challenges the notion that speed affects radiation, stating that motion is relative and does not influence the total emitted light from Earth.
  • Some participants discuss the concept of kinetic energy and temperature, with one asserting that greater speed leads to higher kinetic energy, which in turn increases temperature and radiation.
  • Another participant clarifies that temperature is related to unordered kinetic energy, and the motion of the Earth does not contribute to this unordered energy.
  • Discussion includes the idea that increased atomic motion due to collisions leads to more radiation, with a participant asking for clarification on why this occurs.
  • One participant provides an example of a jet fighter, explaining that its skin warms up due to air friction rather than kinetic energy alone, highlighting the importance of environmental factors in temperature changes.

Areas of Agreement / Disagreement

Participants express differing views on the relationship between motion, kinetic energy, temperature, and radiation. There is no consensus on how these factors interact, and the discussion remains unresolved regarding the implications of Earth's motion on radiation.

Contextual Notes

Participants reference various assumptions about kinetic energy, temperature, and radiation without fully resolving the relationships or definitions involved. The discussion includes nuanced technical arguments that are not universally accepted.

eightsquare
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An object above absolute zero radiates energy. This implies that object on Earth too radiate energy(infrared?) My question is, if the Earth were not moving, we would be much slower, so would we radiate in some other wavelength of the spectrum? We are essentially traveling really fast because of the Earth's movement.
 
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I couldn't see it affecting the amount IR radiation coming from our bodies


Dave
 
How so? We would be slower.
 
why would we be slower ?
if you walk a kilometre your body is still going to expend the same amount of
energy making your legs move regardless of whether the Earth is stationary or moving

Dave
 
You seem to think that the speed of an object affects the amount of radiation it admits. Where did you get that idea?
 
eightsquare said:
How so? We would be slower.

Slower relative to WHAT? Motion is relative. The radiation of the Earth has nothing to do with the speed that it is traveling with respect to other bodies. That speed, by the way, varies from zero to .999999% of c with all values in between. Why would picking one of those frames of reference have anything to do with how much the Earth radiates?
 
Well greater speed means more kinetic energy and higher kinetic energy means higher temperature and higher temperature means more radiation(that's the way I learned it in school). Which part is wrong?
 
its wrong in the way you are relating things ( or not relating things)
as phinds said ... motion is relative

did you read my post post #4
does that not make sense to you ?

Dave
 
If the Earth would not orbit the sun, observers at other stars would see a slightly different spectrum and this spectrum would not depend on the position of Earth in its orbit. The difference would be extremely small, however - we orbit sun with a velocity of ~30km/s, or 1/10000 the speed of light. Observers at other stars could (at most) see a shift of just 2/10000 between "earth moves away from us" and "earth moves towards us".

The total emitted light in the frame of Earth is independent on the motion of Earth relative to anything else.
The total emitted light as seen in other frames might depend on those other frames.

eightsquare said:
and higher kinetic energy means higher temperature
No it does not. Temperature is related to unordered kinetic (and other) energy. The motion of the whole Earth is not unordered.
 
  • #10
mfb said:
No it does not. Temperature is related to unordered kinetic (and other) energy. The motion of the whole Earth is not unordered.

Nice to get a civil explanation. So this basically means the more the atoms are banged about the more they radiate? Why is this?
 
  • #11
So this basically means the more the atoms are banged about the more they radiate? Why is this?

because the collisions cause an increase in temperature
Bang a piece of metal plate with a hammer ... you will find that both the head of the hammer and the metal plate get warm

Dave
 
  • #12
I know that. I'm asking WHY this increase in temperature causes more radiation.
 
  • #13
Collisions lead to accelerated charges, and those produce radiation.
More unordered motion -> more (and higher-energetic) collisions.
 
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  • #14
trying to think of an example if something that gets hotter the faster it moves ...

take a jet fighter ... it does ... its metal skin warms up. and altho the fighter traveling at say, mach 1 ( the speed of sound) has lots of kinetic energy, its not that that is warming the metal skin up.
Its the friction of that metal against the air ( air resistance). if you flew that fighter in a vacuum (with no air)
then the skin wouldn't warm up ... no friction generated heat

cheers
Dave
 
  • #15
mfb said:
Collisions lead to accelerated charges, and those produce radiation.
More unordered motion -> more (and higher-energetic) collisions.

Perfect. Thanks for the answers.
 

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