Recent content by Pedroski55

Thank you all again for your replies. Here is a link to another PDF from Professor Richard Conn Henry. It seems some of you think Professor Henry is mistaken, but the maths is from Einstein and Minkowski: ##d τ^2 = dt^2 − dx^2 = dt^2 − v^2dt^2 = (1 − v^2) dt^2## When v = 1, d τ = 0. To...

Thanks everyone! If, (big if!) I understand it correctly, using the speed of light as a standard, 1 light second = approx. 300 000 000 metres, so it is not incongruent to subtract dt from dx as both may be measured in metres? Professor Henry says in his pdf, because a photon is light...

Reading this PDF from Professor Richard Conn Henry, I am confused by the multiplication by c on page 2. x, y and z are metres. t has units seconds. So I would think, "We can't subtract seconds from metres , we can't subtract dt from dx." To sidestep that, Einstein multiplied dt by c. c has...

Well, thank you for your replies, I see I am going to have to read a lot more about this!

I assume the obverse. Is that not so? Thinking about this, I am wondering why Predicate logic makes such absurd claims. UD : all people Some of them are guitarists, but I have no way of knowing that Lemmy is or is not able to play. If I want to know if Lemmy is a guitarist, I will look up...

Thanks for your reply! Sorry, but I don't get it! Could you elaborate? p is not a guitarist, by definition Gp is FALSE (When p = Agnishom, I think) I read Gx→Gl : if Gx is true, then Gl is true ( and the obverse is : when Gx is false, then Gl is false) 1>3 is false 1>2 is false but I don't...

I'm just learning some basic predicate logic. I found this. UD: People Gx: x can play the guitar l: Lemmy In the expression ∃xGx→Gl, the scope of the quantifier ∃ is the expression Gx. This translates to If there is a guitarist, Lemmy is a guitarist. Now this is changed to: ∃x (Gx→Gl), we...

Thank you all very much! I am the wiser! Wouldn't happen to have a link or info on how, in practice, one catches, measures or reads the oscillations of caesium 133?? That's a very high frequency!

Hi, I'm wondering about time. Time is very important in physics. It seems we inherited the idea of 60 minutes in an hour from the Babylonians. I don't know if the Babylonians were even interested in minutes, let alone seconds, probably not. Later on, we needed more accuracy, I suppose it...

Thanks again everybody! I'll go sit on my little wall and wonder about all this some more!

Thank you both very much! Sorry about getting the speed of light wrong! It is however hard for me to imagine a negative length and impossible for me to imagine spacetime! The is I believe, but the square root of a negative number is unreal. Today, I sat on a wall by the lake in the...

Hi, I'm just an amateur, no physics qualifications. I've been reading here. Professor Richard Conn Henry likes the word trivial. None of this is trivial for me. Einstein apparently said: (sorry don't know how to present the maths correctly here, dx2 means 'dx squared'.) dx2 + dy2 + dz2 -...