I have to respond to this myself uwot.
Yes gaffo, you've found quite an old post here, and you do like to tell me how wrong I am it seems.
gaffo wrote: ↑Sat Aug 04, 2018 3:33 am
Time as a coordinate system.
no, that is space.
time is the 4th dimension.
Yes, a 4th dimension (axis) to the coordinate system whose other three axes are space. So I agree except for the 'no' part. Two events in 4-dimensional spacetime have fixed separation regardless of inertial frame, which is the same as saying that two points in a coordinate system (be it 2D, 3D, 4D, whatever) have a fixed separation regardless of the orientation of the axes chosen.
Unlike the gravitation field in which a thing finds itself, speed is not a property of a thing,
nope - velocity and gravitiation field have the SAME effect upom matter.
I didn't say what effect speed had. I said speed wasn't a property of a thing. What is your current velocity? Can't answer coherently without a reference to something else, which makes it a relation, not a property.
gaffo wrote: ↑Sat Aug 04, 2018 3:33 am
Noax wrote:Speed is not a property of an object,
indirectly it IS - since the mass of an object increases with speed!
mass is a property of an object!
If I have all these different masses in different inertial frames, all without actually changing my trajectory, then mass is variable, and not a property at all. What is a property of an object is rest-mass. That is a frame independent value for any object, and thus a property. If a value (like mass or speed) is indirectly a property, then it isn't really a property, but a relation with, in this case, a reference frame. That's what I am trying to say. I consider an objects properties to be things that do not vary depending on reference frames.
matter increases in mass in both a gravity well and with speed.
Mass (not matter, which is not a physical quantity) increases with speed, but since speed is not a property, the amount of mass of a thing can still be a fixed property of the thing. Two identical objects might have massively different velocity vectors, but since speed is not a property of either of them, neither is the one that actually masses more than the other.
Noax wrote:so speed cannot make something happen slower.
again, nope, speed/gravity (same thing) slows time for the object in question.
OK, carelessly worded on my part. If it has speed, clearly it is being referenced from a frame in which it has speed, and in that frame, yes, its processes are dilated. But in the frame of the object itself, it is the rest of the universe (anything not moving along with the object) that slows down.
light travelling in space will give you zero time.
so nope, you are wrong.
Light speed is not a valid reference frame. Speed of light is c in any frame. You're attempting to make light stationary, but light cannot be made to do that. What velocity would a photon going the other way have?
Two events (one of a pair of twins saying goodbye to the other as he boards the rocket, and the event of their subsequent reunion) are separated by different amounts of time depending on the path taken. The path with excessive spatial displacement requires less time displacement to connect the two events. This is unintuitive since it seems to violate euclidean geometry, but so does the gravity thing, so Euclid was already out the window.
gravity wells will give you the result.
you left that out.
No I didn't. I made it bold so you'd see it. The twins are not going to age noticeably different due to the gravity well of anything in our solar system. To illustrate that, you'd have to do something like they attempted to depict in Interstellar
, however implausible. The planet they depicted was for one thing waaaaay inside the Roche limit and cannot exist, especially with water on it.
As for the twins experiment, it can be done with only SR rules if instantaneous velocity changes can be made, but gravity is simply not part of SR, so the experiment assumes no significant gravitational objects come into play. I've sort of written an illustration of it with no acceleration at all, but instead using tag teams, and keeping it down to minutes, not years. I'll post it if you want to tell me how wrong it is.