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 Feb 20 comment Cerenkov light - a practical calculation Isn't it okay to assume that the muon would be travelling at $c$ throughout it's passage through the glass? It is only 10cm afterall. For a $5keV$ muon: $1-v/c=2.4\times10^{-5}$. Either way, my attempt at the calculation gave $4\times10^{-47}J$ which I really don't think is correct. Basically I'm still stuck :( Feb 20 comment Cerenkov light - a practical calculation Hi zephr. Of course your right if the integral were carried out over the full range of frequencies. In practice however, I'll be using something like this[1] to detect ring patterns and it is sensitive only to wavelengths in the range 300-650nm. [1]: sales.hamamatsu.com/index.php?id=13199716&language=2&; Feb 20 asked Cerenkov light - a practical calculation Jan 31 awarded Yearling Oct 11 awarded Organizer Oct 11 revised Very basic question: When to use $s=vt$, $s=1/2vt$, $s=at$ and $s=a/t^2$? Created new tag Oct 11 suggested approved edit on Very basic question: When to use $s=vt$, $s=1/2vt$, $s=at$ and $s=a/t^2$? Oct 11 comment Very basic question: When to use $s=vt$, $s=1/2vt$, $s=at$ and $s=a/t^2$? Hi @dmckee: the equations should read $s=ut+\frac{at^2}{2}$, $s=\frac{(v+u)t}{2}$, $v=u+at$, and $v^2=u^2+2as$. Or at least they are the ones I was forced to remember some 10 years ago ;-) Oct 11 answered How can I explain why the weak nuclear interaction between individual nucleons is 'weak'? Aug 4 comment Particle physics plots Hi Jim: if you search through some of the older posts of this blog you'll find many lucid and pedagogical explanations of particle physics graphs: blog.vixra.org Jul 29 comment What does scalar phi represent in spacetime? Can't decide whether I like the clarity or the humour more in this answer: +1 ;) Jul 28 accepted Roughly how many atoms thick is the layer of graphite left by a pencil writing on paper? Jul 28 comment Roughly how many atoms thick is the layer of graphite left by a pencil writing on paper? Tim: In light of your above comment defending your answer I have decided it warranted my accepting it. Thanks also to @TheSheepMan for his experimental perspective. Jul 28 comment When will the Hubble volume coincide with the volume of the observable Universe? Hi @Ned Wright, thank you kindly for taking the time to answer. I would like to just clarify the conclusion that appears to be drawn from your calculation, namely - that the observable Universe is destined to increase indefinitely, albeit with increasing redshift? This appears to contradict what I read in the aforementioned book by Penrose. On a side note, I opted for the "photist approach" purely as we're a long way from building a high-resolution neutrino or gravitational wave telescope (well, perhaps just decades for the former.) Jul 27 comment Roughly how many atoms thick is the layer of graphite left by a pencil writing on paper? Thanks @TheSheepMan, that sounds like a good method to establish an answer experimentally. Perhaps you would like to transcribe it into an answer and add to it a theoretical estimate that improves upon Tim's effort? ;-) Jul 26 revised When will the Hubble volume coincide with the volume of the observable Universe? Clarified 4th sentace to include mention of 'number of galaxies' Jul 26 comment When will the Hubble volume coincide with the volume of the observable Universe? @lurscher: Whilst I don't think it answers you query there was another independent varification of DE published recent. Here is a sciam article about it and here is the paper on which it is based. Jul 26 revised When will the Hubble volume coincide with the volume of the observable Universe? edited body; edited tags Jul 26 revised When will the Hubble volume coincide with the volume of the observable Universe? edited tags Jul 26 asked When will the Hubble volume coincide with the volume of the observable Universe?