granpa

you understand that: if 2 events occur at the same place and at the same time then they will do so for all observers regardless of the observers velocity. if event A causes event B then it will do so for all observers. the proper distance/time between any 2 events is the same for all observers Merged post follows: Consecutive posts mergedthe significance of all this being that our coordinate system is just a set of labels that we put on each event. changing our coordinate system doesnt change the underlying reality. only our perspective changes.

where do you see anything in my post about a universal 'now' not existing unless we 'establish' it? that post was only about how and whether it could in theory be established. (if it did exist) Merged post follows: Consecutive posts merged do you know how to draw spacetime diagrams with more than one coordinate system (corresponding to different frames) superimposed?

all you are saying is that there is an absolute 'now'. absolute time is not a new idea. nor is the andromeda paradox. Merged post follows: Consecutive posts merged if it turns out that quantum entanglement allows us to communicate instantly over any distance (but thats another whole thread) then we would be able to establish a universal 'now'. other than that there is of course no measurement that we can make to estiblish a universal 'now'.

yes. thats an improvement but its still misleading. the electron wants to point its axis either parallel or antiparallel to the external field but at any given time it can actually be pointing in any direction.

what you are describing sounds like the andromeda paradox. http://www.google.com/search?hl=en&lr=&safe=on&as_qdr=all&q=+site:www.physicsforums.com+andromeda+paradox http://en.wikipedia.org/wiki/Rietdijk-Putnam_Argument Merged post follows: Consecutive posts mergedremember, reality doesnt change because you change velocity. only your perspective changes.

spin up and spin down. which corresponds to paramagnetism and which to diamagnetism. and is there a more intuitive way to refer to the spin state of an electron than 'up' or 'down'?

and if it were somehow possible then we would expect to see large numbers of living things that are considerably smaller than what is currently considered to be the smallest possible living thing.

when an electron in an atom transitions from one shell to another does it do it instantly or is there a time when it is partially in one and partially in the other. in other words in a superposition of both states. edit:http://209.85.173.132/search?q=cache:q9tx8VVznEMJ:www.physicsforums.com/archive/index.php/t-151024.html+atom+electron+energy+levels+superposition

the context makes it clear that i mean that the acceleration of an object in a gravitational field is independent of the mass of the object undergoing the acceleration. hence a feather and a hammer dropped by an astronaut from the same height at the same time hit the moon at the same moment.

on a side note: if matter and antimatter repel then energy/light would be expected to have no net gravitational mass (but now that i think about it it might have inertial mass). i would fully expect that gravitational mass would always be perfectly conserved. Putting these together implies that inertial mass would not always equal to gravitational mass. (Neither would the ratio of inertial mass to gravitational mass always be the same for all materials) where F2=the force on mass2 due to the gravity of mass1 we have the well known equations: (g means 'gravitational' and i means inertial) F2=-G*Mg1Mg2 / r2 F2=Mi2a2 which if and only if Mi2 = Mg2 gives a2=-G*Mg1/ r2 (acceleration of Mass2 is independent of the mass of Mass2) if instead the equations were revised to read: F2=-G*Mg1Mi2 / r2 F2=Mi2a2 which gives a2=-G*Mg1 / r2 (acceleration of Mass2 is independent of the mass of Mass2 regardless of whether Mi2 = Mg2) assuming that the revised equations are true and that Mi2 and Mg2 differed by a small amount (for instance by the binding energy of the nucleus) then how would we know? the revised equations also imply that F1 would not be equal to F2. However, the net force would be so small that i can see no way of testing it.

http://tech.groups.yahoo.com/group/lawsofform/messages the latest posts seem to relate to what i've been saying in this thread http://tech.groups.yahoo.com/group/lawsofform/message/1993 "It seems hard to find an acceptable answer to the question of how or why the world conceives a desire, and discovers an ability, to see itself, and appears to suffer the process. That it does so is sometimes called the original mystery. Perhaps in view of the form in which we presently take ourselves to exist, the mystery arises from our insistence on framing a question when there is, in reality, nothing to question." in other words, the question itself is meaningless. like what is the sound of one hand clapping.

imagine a line of clocks stretching completely around the universe, stationary and synchronized with respect to each other. imagine a rocket moving along this line. whether the clock on the opposite side of the universe is ahead of or behind the local clock depends on which direction you look along the line. is that what you meant?

'thinking physics' by Epstein

here is an old thread of mine on the concept of existence without space http://www.scienceforums.net/forum/showthread.php?t=37206

the ideal height for a human being would be a couple of inches. at that height we could fall from any distance without hurting ourselves and if we had wings we could fly. we also wouldnt eat very much. no intelligent designer would design a universe where people are six feet tall. where merely tripping over your shoestrings can result in an extremely painful injury. a universe where even if we genetically engineered ourselves to have wings we still couldnt get off the ground because there are no muscles strong enough. would you design it that way? the only way a human brain could fit into a body a few inches tall is if molecules could act as neurons. that clearly isnt possible according to the laws of physics as we currently understand them.

yet mj=ml+ms not mj=ml+2*ms even though gs≅2

http://en.wikipedia.org/wiki/Relativistic_mass#Early_developments:_transverse_and_longitudinal_mass http://en.wikipedia.org/wiki/Relativity_of_simultaneity

that website has changed since I took my notes. it hasnt become any clearer. so if we restrict ourselves to talking about the component of magnetic moment in any one direction (the z direction) then the math becomes very much simpler. μB=the bohr magneton (a unit magnetic moment) for spin: μz=-gsμBms gs≅2 ms=1/2 for orbital magnetic moment: μz=-gLμBmL gL=1 mL=l,l-1,...,-l Merged post follows: Consecutive posts mergedhere is an excellent article on the magnetic moment of electrons: http://www.shef.ac.uk/physics/teaching/phy332/atomic_physics6.pdf

spin of electron=s=1/2 S=(h/2π)*√s(s+1) μs=S*gs*q/2m gs=2 l=0 or 1 or 2 ... up to n-1 L=(h/2π)*√l(l+1) μL=L*gL*q/2m gL=1 net magnetic moment of electron in subshell l = μs + μL is this correct? Merged post follows: Consecutive posts mergedalso do the 2 components have the same sign? is the sum greater than or less than the magnetic moment due to spin alone?

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if the valence electrons of a metal form a degenerate gas then what holds up metallic hydrogen? what determines its density? what prevents it from becoming more dense?

it would propagate the same way that the fields of particles propagate. the 'medium' would have to be elastic. edit:however it would not be a simple elastic. to produce the inverse square laws that we see it would have to be quite complex.

http://en.wikipedia.org/wiki/Vacuum_energy#Origin

good point

lets see what happens when I quote the op and another post. Merged post follows: Consecutive posts mergededit:in threaded view it only responds to the second post. (this line was added by simple quick reply) Merged post follows: Consecutive posts merged this is quoting a third post edit:no change. in threaded view it still only responds to the second post. Merged post follows: Consecutive posts mergedthe only way that one could use threaded view with these other features would be to list, in theaded view, each post as a response to each and every post that it quotes. which is probably not possible.