# Aeschylus

Senior Members

241

1. ## Through which medium does light travel.

Neither a classical wave description or a classical particle description of light is fully adequate to describe light.

3. ## Through which medium does light travel.

Personally I think if your going to think of light as anything, then think of it as waves, with the possible exception of high frequency em radiation which exhibits particle-like behaviour that's not difficult to observe. Of course for a fuller descripion you need to look at quantum mechanics, which shows that neither a classical particle nor a classical wave description of light is completely adequate.

7. ## randomness in math?

Not all maths is completely deterministic, sattistics is obviously not deterministic. Chaos theory is a just an branch of maths that is detreministic. Noise just means unwanted informatioon in a signal and can be completely dedteriministic. If there's anythg random in nature it's quantum physics.
8. ## Calculating Time Dilation

So in other words the direction most defintely does matter.
9. ## Turn Html on!!!!!

It's an absolute must for a vB science or maths forum for Html to be turned on in order to make equations more readable.
10. ## Calculating Time Dilation

Remember: x' = γ(x - uxt) y' = y z' = z t' = γ(1- βx/c) edited to add: for the love of God turn Html on!!!!!!!!

12. ## photon acceleration?

No, because the photon is never at rest in any inertial frame, when your a photon your born at c and you die at c.
13. ## Infinite Universe

In all models of the universe the universe is unbounded and yes an infinite universe can expand, there's certianly nothing unphysical about an infinite expanding unievres. Hugh Everret was the father of the many-worlds interpreation of quantum mechanics, I don't think it's that helpful to say that this means mutiple universe, all it means is that we and presuambly the universe are in a superpostion of states.
14. ## Ending the 0.999~ = 1 debates

Here's nice little proof (well, it's not laid out formally and it uses inequalities that really should be proved first (though they're easy inequalties to prove), but I've gauged it exactly for the sort of person who will argue 0.99.... is not equal to 1. Though are alot better and more comphrehensive proofs, people who've I've shown this one seem to liek it) that I came up with: (Firstly just about every crank whose claimed that 0.999.. is not equal to 1 claims that there are nbo numebrs inbetween 0.999.. and 1, this proof really sets out to deal with this claim) if x = 0.999... then there are 3 possible relations that x and sqrt(x) could have 1. sqrt(x) > 1 Howver if this is the case then 0< x < 1 must be UNTRUE as for any 0 < x < 1, 0 < sqrt(x) < 1. If this is the case x > 1 2. sqrt(x) = 1 If this is the case then x = 1 is the only solution, meaning that 0.999 does indeed equal 1. 3. sqrt(x) < 1 If this is the case then there is a number between 1 and x (as if 0 < x < 1 then sqrt(x) > x); what is the decimal representation of this number? Of cousre at this point someone could argue that in this case sqrt(x) = x, but this means that x msut equal 1 or zero).
15. ## time exists?

Yes indeed velocity is dx/dt, so in order to have velocity we must 'have' dx and dt (i.e. there must be a change in both postion and time). Well GR has some situations in which spacelike dimensions become timelike, but this is the exceptional case in places like the interior of a black hole. In relatviity even though the concept of a spacetime continuum is introduced, there is still a very definite differnce between the two. This is easiest to see in the simplest case of a spacetime continuum, as described by (a form of)the Minowski metric (taking c =1): ds2 = dx2 + dy2 + dz2 - dt2, notice in this form that dt cannot really be considered equivalent to dx, dy or dz due it's minus sign.
16. ## Speed of light and mass

Objects with real rest mass cannot travel at or above c, any object that travels at c MUST have a rest mass of zero. The inertial mass of an object in some inertial refernce frame will tend infinity as that object's speed tends to c. 1/0 is undefined in the real numbers, but in the extended reals it is taken as infinity. Physicists don't use the extended reals, but they are lazy and they will often say that x is infinty at y = z if x tends to infinity as y tends to z. If you get 1/0 in an equation inn special relativity you should interpret the result as unphysical and hence referring to an impossible situation.
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