4 ms·

Yea physicists are in a weird spot when it comes to inertia. Everyone’s heard of it but it’s not real. To say something has mass is to say it requires a force t

Yea physicists are in a weird spot when it comes to inertia. Everyone’s heard of it but it’s not real. To say something has mass is to say it requires a force to move it which is what we call inertia. And also the E=m equivalence isn’t as simple as may be believed. The famous equivalence is cutting out a piece that is important when talking about photons.

SAI_Peregrinus 9y ago
There are certainly many subtleties. For example, I said E=M. But that's for objects at rest. For an object in motion it's E^2=m^2c^4+p^2c^2. In natural units that turns into E=m+p. The energy of a photon is hf, where h is Planck's constant and f is the frequency. That energy is entirely the photon's momentum. And that's without getting into the issues of invariant mass or relativistic mass increases...
- evanb 9y ago
  You dropped a bunch of important squares... E^2 = m^2 + p^2 does not simplify to E=m+p.
  - SAI_Peregrinus 9y ago
    You're right, of course. I really shouldn't do math in my head after midnight.
- jdmichal 9y ago
  Unicode's got a full supplement of sub- and superscript numbers now. E² = m²c⁴ + p²c² https://en.wikipedia.org/wiki/Unicode_subscripts_and_superscripts https://en.wikipedia.org/wiki/Unicode_subscripts_and_supersc...
  - Bromskloss 9y ago
    That's one of those things that, if you ask me, should fall outside the scope of a character set. As I see it, they are just the usual numbers, and restyling, resizing and positioning them should be a concern of a "text" layer, above the "character" layer.
    - teddyh 9y ago
      Maybe in an ideal world, sure, but in this world, nobody is going to add those features to the text layer as long as there are perfectly good Unicode characters right there in the character layer. So we may as well use them.
      - beojan 9y ago
        Most styling markup formats (except markdown, irritatingly) have added those features to the "text" layer.
    - kps 9y ago
      It should. But Unicode's mandate included incorporating common existing character sets, and ISO8859-1 had ² and ³, and it all when down from there, so that now you can write 𝘌 = 𝘮𝘤² which isn't the same as E = mc². A number of early computer systems used teletypes for I/O, and had programming languages in which exponentiation was expressed by moving a half line up, and array subscripts by moving a half line down.
      - e12e 9y ago
        I seem to recall the designer of ascii stating that it was a mistake, and they should've gone with prefix coding instead (following-is-capital,a->A;following is number,<byte>->67 or something along those lines - basically escape codes for everything, I suppose). Instead we got ascii evolved to really, really, really big ascii (utf-32, and the variable encoding utf-8). But yeah, having a "next-is-superscript"-token would probably be cleaner than individual code points for every little glyph that might be a superscript...
    - jdmichal 9y ago
      In that case, you're really going to love the blackletter block: https://en.m.wikipedia.org/wiki/Blackletter#Unicode https://en.m.wikipedia.org/wiki/Blackletter#Unicode

SAI_Peregrinus 9y ago

There are certainly many subtleties. For example, I said E=M. But that's for objects at rest. For an object in motion it's E^2=m^2c^4+p^2c^2. In natural units that turns into E=m+p. The energy of a photon is hf, where h is Planck's constant and f is the frequency. That energy is entirely the photon's momentum. And that's without getting into the issues of invariant mass or relativistic mass increases...

evanb 9y ago
You dropped a bunch of important squares... E^2 = m^2 + p^2 does not simplify to E=m+p.
- SAI_Peregrinus 9y ago
  You're right, of course. I really shouldn't do math in my head after midnight.
jdmichal 9y ago
Unicode's got a full supplement of sub- and superscript numbers now. E² = m²c⁴ + p²c² https://en.wikipedia.org/wiki/Unicode_subscripts_and_superscripts https://en.wikipedia.org/wiki/Unicode_subscripts_and_supersc...
- Bromskloss 9y ago
  That's one of those things that, if you ask me, should fall outside the scope of a character set. As I see it, they are just the usual numbers, and restyling, resizing and positioning them should be a concern of a "text" layer, above the "character" layer.
  - teddyh 9y ago
    Maybe in an ideal world, sure, but in this world, nobody is going to add those features to the text layer as long as there are perfectly good Unicode characters right there in the character layer. So we may as well use them.
    - beojan 9y ago
      Most styling markup formats (except markdown, irritatingly) have added those features to the "text" layer.
  - kps 9y ago
    It should. But Unicode's mandate included incorporating common existing character sets, and ISO8859-1 had ² and ³, and it all when down from there, so that now you can write 𝘌 = 𝘮𝘤² which isn't the same as E = mc². A number of early computer systems used teletypes for I/O, and had programming languages in which exponentiation was expressed by moving a half line up, and array subscripts by moving a half line down.
    - e12e 9y ago
      I seem to recall the designer of ascii stating that it was a mistake, and they should've gone with prefix coding instead (following-is-capital,a->A;following is number,<byte>->67 or something along those lines - basically escape codes for everything, I suppose). Instead we got ascii evolved to really, really, really big ascii (utf-32, and the variable encoding utf-8). But yeah, having a "next-is-superscript"-token would probably be cleaner than individual code points for every little glyph that might be a superscript...
  - jdmichal 9y ago
    In that case, you're really going to love the blackletter block: https://en.m.wikipedia.org/wiki/Blackletter#Unicode https://en.m.wikipedia.org/wiki/Blackletter#Unicode