# Does heat have inertia or momentum? **URL:** \ **Category:** Factual Questions\ **Created:** [September 17, 2007, 9:44am UTC](https://boards.straightdope.com/t/does-heat-have-inertia-or-momentum/419476 "2007-09-17T09:44:07Z")\ **Posts on this page:** 6\ **Page:** 2
**Author:** ![Ring](https://avatars.discourse-cdn.com/v4/letter/r/6a8cbe/32.png) [@Ring](https://boards.straightdope.com/u/Ring)\ **Post date:** [September 18, 2007, 8:10pm UTC](https://boards.straightdope.com/t/does-heat-have-inertia-or-momentum/419476/21 "2007-09-18T20:10:59Z")
**Pleonast** wrote: > [@](#): > > Sorry, that turned into a condensed matter lecture. Hopefully a few of you can get the gist of it. Very nice explanation. Thank you berry much. ---
**Author:** ![Napier](https://avatars.discourse-cdn.com/v4/letter/n/ce73a5/32.png) [@Napier](https://boards.straightdope.com/u/Napier)\ **Post date:** [September 18, 2007, 9:25pm UTC](https://boards.straightdope.com/t/does-heat-have-inertia-or-momentum/419476/22 "2007-09-18T21:25:17Z")
\> If the heat itself has inertia the result should be the possibility of oscillation in the heat flow. Is there any such thing? Fascinating point. There are thermal analogs to resistors and capacitors, but not to inductors as far as anybody knows. From this point of view, heat differs from other dynamic agencies such as electricity and fluid flow and vibration. So, no, you can’t build an oscillating thermal circuit with passive components only, like you can do with electronics. Note, in electronics, you can’t do it if you don’t use inductors. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [September 18, 2007, 10:01pm UTC](https://boards.straightdope.com/t/does-heat-have-inertia-or-momentum/419476/23 "2007-09-18T22:01:41Z")
> [@](#): > > Nevertheless I feel compelled, in a nit picky way, to disagree with him. I don’t think we’re disagreeing, here. Perhaps you missed that I said that mass “may appear” to be converted? It’s possible that I wasn’t as clear there as I might have been, though. ---
**Author:** ![Ring](https://avatars.discourse-cdn.com/v4/letter/r/6a8cbe/32.png) [@Ring](https://boards.straightdope.com/u/Ring)\ **Post date:** [September 18, 2007, 10:58pm UTC](https://boards.straightdope.com/t/does-heat-have-inertia-or-momentum/419476/24 "2007-09-18T22:58:29Z")
[QUOTE=Chronos] I don’t think we’re disagreeing, here. Perhaps you missed that I said that mass “may appear” to be converted? It’s possible that I wasn’t as clear there as I might have been, though. [/QUOTE] It’s funny. I specifically came back to this thread because I was worried that someone might think that I was stupid enough to contradict you. Because after thinking about it I realized that I didn’t really didn’t say anything that you hadn’t already said. I just used more words. At various other forums I’ve heard people ask questions similar to, “what exactly is happening when mass turns into energy.” And I finally came to conclusion that I didn’t like the phrase simply because it confuses people; to me it’s sort of like “relativistic mass.” On the other hand, I have no answer to this part of your post: > [@](#): > > If I look at the system consisting of the two photons, I’ll find that the total mass of that system is exactly the same as the total mass of the electron and positron. However, it might also be interesting to look at the photons one at a time. If I do this, I’ll determine that each individual photon has no mass, and that all of its energy is kinetic energy. ---
**Author:** ![Ring](https://avatars.discourse-cdn.com/v4/letter/r/6a8cbe/32.png) [@Ring](https://boards.straightdope.com/u/Ring)\ **Post date:** [September 18, 2007, 11:22pm UTC](https://boards.straightdope.com/t/does-heat-have-inertia-or-momentum/419476/25 "2007-09-18T23:22:43Z")
Also, a pretty well respected physicist (Matte Meron) on sci.physics once wrote: > [@](#): > > Just that there is energy associated with mass, that’s all. But calling mass “a form of energy” is apt to be confusing, I would refrain from it. I’d be curious as to what you think of this statement. ---
**Author:** ![Ring](https://avatars.discourse-cdn.com/v4/letter/r/6a8cbe/32.png) [@Ring](https://boards.straightdope.com/u/Ring)\ **Post date:** [September 18, 2007, 11:35pm UTC](https://boards.straightdope.com/t/does-heat-have-inertia-or-momentum/419476/26 "2007-09-18T23:35:51Z")
I forgot to add: In the momentum four-vector energy is the time component and mass is the magnitude; Given this I’ve never been able to see how mass can be considered to be just a form of energy. [Previous page](https://boards.straightdope.com/t/does-heat-have-inertia-or-momentum/419476.md?page=1)