Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > rec.puzzles > #28090

Re: Puzzling Questions

Show all headers | View raw

ram@zedat.fu-berlin.de (Stefan Ram) writes:
> ram@zedat.fu-berlin.de (Stefan Ram) wrote or quoted:
>>"E = mc^2" does /not/ mean that energy (E) can be converted
>>into mass (m), but rather that mass is always conserved.
>>Can you see why? ("c" is a constant, the speed of light.)
>
>   Spoiler warning: This post now contains what I deem to be
>   the correct answers.
>
>   We know from high-school that energy is conserved, i.e.,
>   constant. The speed of light also is constant. But when E
>   is constant, c is constant, and E=mc^2, m also is constant!

Energy isn't conserved. That was a naive pre-GR view.

The equations of motion are not invariant over time, therefore Noether's
theorem has no symmetry to work with, and provides no invariance law.

Phil
-- 
We are no longer hunters and nomads. No longer awed and frightened, as we have
gained some understanding of the world in which we live. As such, we can cast
aside childish remnants from the dawn of our civilization.
-- NotSanguine on SoylentNews, after Eugen Weber in /The Western Tradition/

Back to rec.puzzles | Previous | Next — Previous in thread | Find similar | Unroll thread

Thread

Puzzling Questions ram@zedat.fu-berlin.de (Stefan Ram) - 2026-09-10 08:49 +0000
  Re: Puzzling Questions richard@cogsci.ed.ac.uk (Richard Tobin) - 2026-09-10 10:26 +0000
  Re: Puzzling Questions ram@zedat.fu-berlin.de (Stefan Ram) - 2026-09-17 09:26 +0000
    Re: Puzzling Questions Phil Carmody <pc+usenet@asdf.org> - 2026-09-30 23:33 +0300

csiph-web