moth

if you've got some time, and haven't noticed yet, you might search you tube for "math lectures" and physics lectures too. MIT is awesome for posting these lectures

Lorentz said the rate at which time passes depends on the velocity of energy moving (compared to some other point) through space, to me rate implies ratio like velocity=distance/time, so what is the ratio for time passage? seconds per second seems useless except for describing acceleration so what would be a reasonable denominator?

the short term future is in a way pre-determined by the present.but sensitivity to initial conditions makes the trajectories of the future diverge so it becomes unpredictable Merged post follows: Consecutive posts mergedwhile there could be a spacetime coordinate for all possible futures some will be more or less likely depending on past and current actions.freewill could affect (effect?) the future you experience even if all futures were pre-determined.

is there anything that is not moving? "at rest" depends on the observer who is probably moving in some way so the task is to change momentum by working against inertia. could you say force against inertia is transformed into momentum? a force could be equally opposed by inertia, and if enough momentum is created by the force motion results?

as strange as it is to imagine, time and distance are not the reliable measure of things they seem to be in everyday life. distance/time < c is the measure. distance changes depending on the direction you're moving and time varies depending on the speed you're moving.

i'll go! interesting point they make about C.B.R. getting blue-shifted enough to melt the ship.

ajb "I guess it is not completely clear if we are talking about a "test object" in the gravitational field of some source, i.e. in vacua or if we are talking about how the energy-momentum of an object "bends itself", principally in "time"." i was thinking about the latter, but i can see that it's not so simple to swap time and space coordinates as though they are the same. Pmb bent in time would be like saying a vertical arch like over a door in a wall was bent in height,or a horizontal arch like a dam was bent in depth.it's clumsy, but it seems similar to what is going on in Lorentz contraction.

in addition to ternary logic check out q-bits http://en.wikipedia.org/wiki/Qubit their value is 0 and 1

decimal points are slippery little suckers. fortunately, you can always catch mistakes later(but hopefully before anybody reads your post).

check this if you haven't already http://relativity.livingreviews.org/open?pubNo=lrr-2003-1&page=node1.html i've been slowly working my way through this overview of g.p.s. and G.R., the math is over my head but there are enough words and results to get a good idea what's going on.

pmb "Since the R_tt= 0 in a vacuum then "amount of bending in time" = 0 in a vacuum." that seems okay if a vacuum means no energy.without ether what could bend in a vacuum?

thanks for the planetmath link ajb, i've been looking for something like that. i recently read about Hinton (inventor of the tesseract) who came up with words to describe motion in 4 dimensions ana and kata (up and down or left and right)maybe i can invent a word that means the curve that matter gets from momentum(other than bend) and take it on the road.

time seems cyclic on many scales, with orbits and frequency of electromagnetic radiation, and a one-way process with stellar evolution and radioactivity, on the other end. i wonder if an end to time could be more like a horizon, like the edge of the observable universe you just can't get there?

thank you all for your replies. i'm starting to see why bend in time is not the best terminology. interesting universe we live in. i can't believe i cut and pasted that formula( 2*pi*r*(1-v^2)^-1/2)to make sure i got it right but it's still miswritten i gotta be more careful.

the wikipedia page on the Ehrenfest paradox http://en.wikipedia.org/wiki/Ehrenfest_paradox says Einstien showed that Circumferance = 2 * pi *r* (1−v2)^-1/2. maybe the disk has become bowl shaped? Merged post follows: Consecutive posts merged ok after looking at the classical equations i see x-vt is the relative motion of the x' origin so if v=(change in x)/time, and the change in x is positive and time is positive v is positive. also i guess any (small?) value but 0 will work for t(because at t=0 nothing has happened?) and the answer is an offset from t. am i on the right track here?

according to wikipedia Planck time is about 5.39124 * 10^-44 seconds so 1/Planck time is about 1.8548 * 10^43 cycles per second. 1/(3*Planck time) might be a better estimate of a maximum frame rate so you could get a couple of samples per frame.

according to quantum mechanics Planck time is the smallest unit of time so 1/Planck time would probably be your theoretical maximum frame rate(physical limitations of photodetectors and memory will keep you from getting anywhere close), but as Baby Astronaut pointed out you have to wait for the photons to bounce off something and hit the camera before you see anything.

maybe centrifugal force is warped spacetime pushing us away from the center

thanks for the encouragement swansont and MrSkeptic. " Keep in mind that it is space itself being bent as well as anything in it." does that mean pi has a different value on a rotating disk?or does time dilation balance the books here too? Merged post follows: Consecutive posts mergedif i was using Lorentz equations on a rotating disk (radius=1 for simplicity) i would center the disk at the origin and look at x=0,y=1(and ignore y=1 since it's not changing much)for my x. then calculate the velocity of the edge of the disk(pi * diameter * r.p.m.) for v(how do i tell if v is positive or negative?). what value do i use for t? other than that, it seems straightforward enough.

that makes sense to me now, acceleration is acceleration. gravity only seems special because it's not obvious whats doing the pushing.

in my last post i said the distance from the surface of the earth when i should have said center of the earth but i think you get the idea. i'm just not sure if it applies when you're underground.it seems like your weight would decrease underground until you reached the center where you would be weightless. i don't think artificial gravity would cause time dilation but thats just my opinion. there are people here who know. i guess it's a question of wording. it would be interesting to find out if 1G in a rotating artificial gravity chamber caused the same amount of Lorentz contraction and dilation as 1G on earth, but when i try the math i get confused about that vx/c^2 term in the time part of Lorentz equation.

from the little bit of math i know the force of gravity decreases by the square of the distance so something that weighs 1 pound some distance from the surface of earth,weighs 1/4 pound when it's twice that distance 1/d^2. since 1 divided by a huge number is a tiny little number no matter how huge the big number gets (even 13 billion light years) this means earths gravity(for example) is still a force even at the edges of the observable universe. i don't know about centrifugal force and time dilation it seems like you would need to be spinning really fast to slow a clock.

thanks for the input npts2020 and klaynos i understand you couldn't build a physical example i'm just trying to understand where the distance "goes" during lorentz contraction. lacking the math skill to solve the equation i try and model in my head and read wikipedia and of course this forum. i'm starting to get the idea that time dialation and length contraction balance each other so lightspeed stays constant but it's a journey.

npts2020 "propellers only move at a small fraction of the speed of light, " it sounds as if you're saying the solution to the Ehrenfest paradox is the train flies off the track. what if instead of a propeller i used a carbon nanotube spinning in a magnetic field?

it seems like the propeller blades would bend back like boomerangs as the tips slower time passage would begin to affect how much distance they could cover without exceeding lightspeed. as for the bend in the time direction, we can't see it in our 3-d view of this 4-d bend. picture a box sitting on a 2-d surface like the floor. the vertical dimension would be the box's height. now try and picture the vertical dimension as the length of time the box sat on that spot on the floor.kind of rotate the familiar height dimension out of view and the time dimension into it's place so you have a 2-d slice of the box (the width and the depth) for every instant the box sat on that spot on the floor in our 3-d picture.now if you could pull on the top of the box (in time) you might expect the width and/or depth to change too, and that change would show up in our everyday 3-d worldview. of course there might also be weird effects at both ends of the duration(the top and bottom of the box in the rotated time view).