Does Radiation from a Colder Body Affect a Hotter Body in a Vacuum?

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Discussion Overview

The discussion centers on the interaction of radiation between a colder body and a hotter body in a vacuum, exploring whether radiation emitted by the colder body can be absorbed by the hotter body. Participants examine the nature of radiation exchange and energy transfer between the two bodies.

Discussion Character

  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • Some participants question whether radiation from a colder body can ever be absorbed by a hotter body, suggesting that radiation is primarily one-way from hot to cold.
  • Others argue that both bodies absorb radiation from each other, but the colder body ultimately receives more energy than it emits.
  • It is noted that the hotter body emits more radiation overall, leading to a net transfer of energy from the hot body to the cold body.
  • Some participants clarify that while both bodies radiate energy into space, the colder body does emit some radiation toward the hotter body, albeit less than what it receives.
  • One participant emphasizes that the cold body may still experience a net loss of energy depending on the specific circumstances, referencing the long-term cooling of planets despite receiving energy from the sun.

Areas of Agreement / Disagreement

Participants express differing views on the nature of radiation exchange, with no consensus reached on whether radiation from a colder body can affect a hotter body. The discussion remains unresolved regarding the specifics of energy transfer dynamics.

Contextual Notes

Participants highlight the importance of context, such as the relative distances and conditions of the bodies involved, which may influence the outcomes of radiation exchange. There are also mentions of specific scenarios, like the cooling of planets, that introduce additional complexity to the discussion.

philrainey
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is it true that the radiation a colder body radiates through a vacuum will never hit a hotter body and have its radiation energy absorped? Is the radiation simply one way from the hot body to the colder body?
 
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Hi philrainey! :smile:
philrainey said:
is it true that the radiation a colder body radiates through a vacuum will never hit a hotter body and have its radiation energy absorped? Is the radiation simply one way from the hot body to the colder body?

Nooo … they both absorb radiation from each other …

:biggrin: but the colder body always wins! :biggrin:​
 
Remember that the hot emits more than the cold. So in the end there is still a net transfer from hot to cold, not from cold to hot.
 
The wording of the first sentence is very unclear to me...

Are you asking about two bodies sitting near each other in space? The hot object will radiate toward the cold one, but both will radiate away into space. Depending on the specifics of the situation, the cold one may still have a net loss of energy. Ie, the planets in the solar system have lost energy and cooled over billions of years despite getting energy from the sun. They radiate away more than they receive.
 
russ_watters said:
The wording of the first sentence is very unclear to me...

Are you asking about two bodies sitting near each other in space? The hot object will radiate toward the cold one, but both will radiate away into space. Depending on the specifics of the situation, the cold one may still have a net loss of energy. Ie, the planets in the solar system have lost energy and cooled over billions of years despite getting energy from the sun. They radiate away more than they receive.

From what I understand you are right that hot body radiates heat to the cold body and both radiate to outerspace but the cold body also radiates a little portion of heat to the hot body but not as much as the hot body to the cold one.
 
Oh, well yes, it can be said that the cold body radiates toward the hot body and just receives more in return, yes. The net effect is it is receiving.
 

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