230 reputation
17
bio website
location
age
visits member for 2 years, 3 months
seen Sep 24 at 8:34

Jul
4
awarded  Yearling
Sep
21
awarded  Custodian
Jul
7
accepted If quarks didn't have mass, could protons (and neutrons) exist?
Jul
7
awarded  Teacher
Jul
7
answered Why are the physical sciences described perfectly by mathematics?
Jul
7
awarded  Critic
Jul
6
asked If quarks didn't have mass, could protons (and neutrons) exist?
Jul
4
comment Why did we need relativity to derive $E=mc^2$?
@JerrySchirmer ... so ... if the total amount of energy lost is not invariant in different reference frames with a classical Doppler effect, why do we need special relativity to discover the relationship between energy and mass?
Jul
4
awarded  Scholar
Jul
4
accepted Why did we need relativity to derive $E=mc^2$?
Jul
4
awarded  Supporter
Jul
4
reviewed Approve suggested edit on Why did we need relativity to derive $E=mc^2$?
Jul
4
comment Why did we need relativity to derive $E=mc^2$?
Also, just to clarify, I recognize the need for special relativity in general. I just wasn't sold on why it is needed to discover the mass-energy relation.
Jul
4
comment Why did we need relativity to derive $E=mc^2$?
Okay, so if I understand correctly: in classical physics, if the bulb emits light in all directions, then the total amount of energy lost is invariant, even in other frames of reference (so, classical Doppler effect has no impact on the total amount of energy lost due to the light pulse). It is only with special relativity, and a relativistic Doppler effect, that the light pulse carries away different amounts of energy in different reference frames. Is that correct?
Jul
4
comment Conversion of the units BeV (US) and GeV (UN)
@Non-standardmodel Hmmm, that is tricky! The wikipedia article I linked has a list of countries that use each scale, so if you know the nationality of your author, you can make a pretty educated guess. Also, you know that your author is going to consistently use only one system, so if you ever see terms like milliard or billiard, you know (s)he is using the long-scale. Likewise, if (s)he ever says "one billion eV (or 1 GeV)", you know (s)he is using the short scale.
Jul
4
comment Why did we need relativity to derive $E=mc^2$?
@SachinShekhar this video (youtube.com/watch?v=hW7DW9NIO9M) manages to derive E=mc^2 perfectly well using 1/2*mv^2. Also, I know that classical and relativistic doppler effects are different (which is why I said *similar result and not the same result); my question is, isn't the classical doppler effect sufficient to discover that when things lose energy they also lose mass, even if the equation derived wouldn't be exactly E=mc^2?
Jul
4
comment Conversion of the units BeV (US) and GeV (UN)
@Non-standard: yes, milliard is a term used to describe one thousand millions in the long scale. Where I live, if you said milliard they would look at you as if you were crazy (unless they knew French, in which case they would understand exactly what you meant :) )
Jul
4
revised Conversion of the units BeV (US) and GeV (UN)
added 321 characters in body
Jul
4
revised Conversion of the units BeV (US) and GeV (UN)
added 321 characters in body
Jul
4
answered Conversion of the units BeV (US) and GeV (UN)