How much faster than light are we capable of measuring?
in [Relativity]
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From: Sue... on 18 May 2010 17:53 On May 18, 4:18 pm, GogoJF <jfgog...(a)yahoo.com> wrote: ============== > What is the meaning of c? http://physics.nist.gov/cuu/Constants/alpha.html Sue... > Whether one believes that light is finite > and constant and travels at c- or whether light is to be believed to > be instant- is regardless- because the reason why the speed of light c > travels at 300,000 km/s and not 200,000 km/s, or 100,000 km/s is a > separate issue. > > Why this particular speed of c? > > 1) Is this merely the limit of man's measurably? > 2) Is there some indication of c on a planetary or stellar scale, in > terms of our inertia? > 3) Is this speed human friendly? In other words, would we as humans > be different if c were a different constant speed? Would we be the > same if c were not constant?
From: harald on 18 May 2010 18:55 On May 18, 10:18 pm, GogoJF <jfgog...(a)yahoo.com> wrote: > What is the meaning of c? Whether one believes that light is finite > and constant and travels at c- or whether light is to be believed to > be instant- is regardless- because the reason why the speed of light c > travels at 300,000 km/s and not 200,000 km/s, or 100,000 km/s > is a separate issue. OK > Why this particular speed of c? > > 1) Is this merely the limit of man's measurably? No, not directly (although we can't measure our "true" or "absolute" speed relative to light). If something moved faster than c, we could certainly measure that - unphysical things such as projections and shadows can in principle be measured to move faster than c. > 2) Is there some indication of c on a planetary or stellar > scale, in terms of our inertia? E = m c² > 3) Is this speed human friendly? In other words, would we as humans > be different if c were a different constant speed? Would we > be the same if c were not constant? c is a constant, but it's not constant - just as the c of sound is a constant that is not constant. c = 1/sqrt(eps*mu). It's difficult to say how we would be different; it depends on what you keep constant and c affects a lot of things. Cheers, Harald
From: Inertial on 18 May 2010 21:10 "GogoJF" <jfgogo22(a)yahoo.com> wrote in message news:abe719f4-dc60-42ba-a33d-d211e6df2bfb(a)q8g2000vbm.googlegroups.com... > What is the meaning of c? Whether one believes that light is finite > and constant and travels at c- or whether light is to be believed to > be instant- It isn't .. because we can measure that it isn't . > is regardless- because the reason why the speed of light c > travels at 300,000 km/s and not 200,000 km/s, or 100,000 km/s is a > separate issue. > > Why this particular speed of c? Because that is what it is. It doesn't need a reason to be that way. Its purely determined by human choice of units. In 'sensible' (or natural) units, c = 1. > 1) Is this merely the limit of man's measurably? Nope > 2) Is there some indication of c on a planetary or stellar scale, in > terms of our inertia? Nope > 3) Is this speed human friendly? In other words, would we as humans > be different if c were a different constant speed? Would we be the > same if c were not constant? The universe would be totally different is there were different 'laws' of physics .. but asking what people would be like in that case is pure guesswork.
From: OG on 19 May 2010 14:56 dlzc wrote: > Dear GogoJF: > > On May 18, 1:18 pm, GogoJF <jfgog...(a)yahoo.com> wrote: >> What is the meaning of c? Whether one believes >> that light is finite and constant and travels at >> c- or whether light is to be believed to be >> instant- is regardless- because the reason why >> the speed of light c travels at 300,000 km/s and >> not 200,000 km/s, or 100,000 km/s is a separate >> issue. >> >> Why this particular speed of c? > > 299,792,458.6 m/sec was the last measured value by the US-NBS, and had > been "honing in" on such a value for nearly 20 years, once they had > moved from a physical rod (some fraction of the assumed equatorial > circumference of Earth) to characteristic wavelengths of light. > >> 1) Is this merely the limit of man's measurably? > > No, we could measure "incredibly close to infinite", or "inclusive of > zero". > >> 2) Is there some indication of c on a >> planetary or stellar scale, in terms of our >> inertia? > > Correlates well with the conversion of rest mass to energy: > E = mc^2. > >> 3) Is this speed human friendly? In other >> words, would we as humans be different if c >> were a different constant speed? Would we >> be the same if c were not constant? > > c is tied up in the fine structure constant, and it has been observed > to have changed by about 1 part in 10^8 in the displayed history of > the Universe (about 13 billion years or so). Has a historic change been observed? I thought that we had measured the _limits_ of any possible change (1:10^8), but not any particular change itself.
From: dlzc on 19 May 2010 15:59
Dear OG: On May 19, 11:56 am, OG <o...(a)gwynnefamily.org.uk> wrote: > dlzc wrote: > > On May 18, 1:18 pm, GogoJF <jfgog...(a)yahoo.com> wrote: .... > >> 3) Is this speed human friendly? In other > >> words, would we as humans be different if c > >> were a different constant speed? Would we > >> be the same if c were not constant? > > > c is tied up in the fine structure constant, > > and it has been observed to have changed by > > about 1 part in 10^8 in the displayed history > > of the Universe (about 13 billion years or so). > > Has a historic change been observed? I thought > that we had measured the _limits_ of any > possible change (1:10^8), but not any particular > change itself. http://www.foxnews.com/story/0,2933,203180,00.html http://arxiv.org/abs/1004.5383 .... may have been refined since this. David A. Smith |