Why don't stars change position?

@Soothfast
Like King of Prussia, Lansdale, Horsham, Pottstown.
I used to work at the old Commodore plant, went down 309, not sure what that place is now.

@sonhouse said
@Soothfast
Like King of Prussia, Lansdale, Horsham, Pottstown.
I used to work at the old Commodore plant, went down 309, not sure what that place is now.

Small world, eh?

I moved out to here from California a couple decades ago, so I don't know so much about the history of the place.

@Soothfast
Funny that, I was born in California, El Monte, LA, had an Irish band called Southwind in Venice Beach and played all over LA and got a national TV show gig back then, LONG time ago, now compose guitar and other acoustic instruments and ship them to a site called Soundcloud, a great site for musicians.
I also lived up the side of Mount Palomar and attended Palomar College in San Marcos till I got raked into joining the Air Force🙂

@soothfast said
I don't know what Brian Greene says, but I don't agree with that idea. Time dilation also occurs merely by moving (from the point of view of one who is not). It's what's needed in order for the speed of light to be a constant from all points of view: fast, slow, accelerating, not accelerating. This is codified in special relativity, as opposed to general relativity. Special relativity doesn't deal with gravity as it is usually defined in physics textbooks.

" Time dilation also occurs merely by moving"

Of course it does. That is why the equivalence principal is relevant as a thought experiment.

@Metal-Brain
So time dilation has TWO causes, mass AND velocity or acceleration Just the position in a gravity field effects time flow, we have atomic clocks so accurate now the can detect the change in time flow from a difference in altitude of one meter so you feet run slower than your head unless you are lying down in bed.
Of course you won't see much of a change involving nanoseconds but it is there.

@sonhouse said
@Metal-Brain
So time dilation has TWO causes, mass AND velocity or acceleration Just the position in a gravity field effects time flow, we have atomic clocks so accurate now the can detect the change in time flow from a difference in altitude of one meter so you feet run slower than your head unless you are lying down in bed.
Of course you won't see much of a change involving nanoseconds but it is there.

Time dilation is gravity.
Time dilation is NOT a result of gravity. That is an absurd assertion.

@Metal-Brain
Funny how there are TWO separate physics effects going on here that can create 'time dilation'. But that won't stop you from repeating your buddy.

@sonhouse said
@Metal-Brain
Funny how there are TWO separate physics effects going on here that can create 'time dilation'. But that won't stop you from repeating your buddy.

You have no point.
You prove nothing by pointing out that fact.

@Metal-Brain
OF COURSE to someone like you who hangs your hat on someone and never let go, which limits your ability to see the trees for the forest.

@sonhouse said
@Metal-Brain
Funny how there are TWO separate physics effects going on here that can create 'time dilation'. But that won't stop you from repeating your buddy.

Why would gravity cause time dilation?
Simple question.

@Metal-Brain
It is because gravity is not a FORCE as such, it is a bending of spacetime, and like a ball let loose on a hill, the ball gains kinetic energy just falling down the hill and so does matter falling down that spacetime curve we call gravity.

That IS time dilation, spacetime curvature RESULTS in time slowing down and that is a real slowdown and very accurate atomic clocks can now measure the change in time flow from one clock one meter higher than another because one meter change in altitude causes a tiny but measurable change in time flow which for some reason you are obsessed with calling it 'time dilation'. And THAT change comes from mass. More mass, slower time flow.

Time gets UNdilated if you must, by going UP and out of a spacetime curve towards more flat spacetime curved space, that is to say away from big masses so time flows faster at the orbit of Pluto than it does on anything in orbit around the sun at say Earth distance, 93 odd million miles out compared to a couple three billion miles out for Pluto.

But plowing into that spacetime curve with high velocity ALSO causes changes in time flow, closer to c, the slower time flows for that particle or spacecraft if we can ever actually GET close to c.

THAT is why we say time flow changes, you want to call time dilation, has TWO separate physics causes and therefore cannot be the fundamental in the phenomena. Time flow changes are the RESULT of being in a steep gravity well AND being in a craft simply going close to the speed of light.

So you go to a star say 100 ly away and you are like .999999c so the trip takes say a month for you, you spend a year there, come back at the same velocity and you find Earth clocks register 201 years having going by on Earth but only a year and a couple of months goes by for you since every atom, every particle on the ship slows down timewise and so your watch slows down by that amount and you THINK you are going faster than c but in fact all that happens is the FLOW of time changes by the velocity being so close to c.

@sonhouse said
@Metal-Brain
It is because gravity is not a FORCE as such, it is a bending of spacetime, and like a ball let loose on a hill, the ball gains kinetic energy just falling down the hill and so does matter falling down that spacetime curve we call gravity.

That IS time dilation, spacetime curvature RESULTS in time slowing down and that is a real slowdown and very accurate at ...[text shortened]... than c but in fact all that happens is the FLOW of time changes by the velocity being so close to c.

Gravity is a force.

@Metal-Brain
Showing off your fourth grade education again.
Gravity is NOT a force. It is a bending of spacetime. But you are unable to understand that so you just go to the nearest fringe site you can so you can find your scientist of the month club.

MASS is what forces the bending of spacetime. Also, do you get the part about it being SPACETIME. Just like magnetism and electric forces combine to make electromagnetic forces except electric fields actually do force ions to accelerate or decelerate.
Gravity is just like a ball on a hill, it rolls down the hill and gains momentum.
A mass will gravitate to a higher spacetime curve like a ball rolling down a hill but there is no gravity field because it is bent spacetime and matter follows spacetime curves and that includes changes in time flow.
Like I already said, atomic clocks are now accurate enough to measure the change in time flow from two clocks one meter apart vertically.
If the same clocks are put side by side they will show the same time flow.
That is because the clocks are immersed in the same spacetime curve area.
Gravity ACTS like a force and we think it is a force but it is just matter responding to the bending of spacetime.

Time runs a bit faster in an orbit at the distance of pluto Vs being in an orbit at the distance of Earth. Time runs slightly faster in an orbit the same distance from the sun as Mercury but not close to mercury than something in an orbit the distance of Earth from the sun but away from Earth, just the two experiencing the spacetime curve at those two distances from the sun.

@sonhouse said
@Metal-Brain
Showing off your fourth grade education again.
Gravity is NOT a force. It is a bending of spacetime. But you are unable to understand that so you just go to the nearest fringe site you can so you can find your scientist of the month club.

MASS is what forces the bending of spacetime. Also, do you get the part about it being SPACETIME. Just like magnetism an ...[text shortened]... away from Earth, just the two experiencing the spacetime curve at those two distances from the sun.

Go to the top of your roof and jump off.
Then when you break your ribs or some other bones tell me it is not a force.

Tell us all how spaghettification is possible if gravity is not a force.

https://en.wikipedia.org/wiki/Spaghettification

@metal-brain said
That was an accident. I meant acceleration.

It is not a true equivalence. "velocity" is not "acceleration". It was the thought experiment that made Einstein realize that time dilation causes gravity. People that claim gravity causes time dilation don't know what they are talking about. Just ask them why gravity causes time dilation. They never have an answer because they have it backwards and are in denial of it.

Stop bastardizing Einstein.

Einstein never "realized time dilation causes gravity". You have this backwards.