[Professor Mega-Mind]

...................Mass-ive ?
 Virtual particles , quantum fluctuations , fields of force ?
What is the speed of a magnetic field anyway ?  It's a mystery wrapped within an enigma .
 We need to master the actual composition of space , in order to manipulate/use it .  Think unidirectional & absented/partial fields of force/gravity .
Useful , huh ?
D.H.

[Paul25]

It sounds more credible to liken it to something which is better understood

[Professor Mega-Mind]

Nobody likes to profess their igernance !
P.

[Professor Mega-Mind]

Actually , the items mentioned in Reply#18 all have mass or virtual-mass . Both produce gravity , as any form of matter or energy does .
P.M.  .

[Bill S]

https://www.ualberta.ca/~pogosyan/teaching/ASTRO_122/lect24/lecture24.html

“The vector V is the direction that the star is moving”.

Presumably, this is motion relative to the Earth.  How would that relate to movement relative to anything else?

[Professor Mega-Mind]

The vector of time , or as it's commonly described ; The Arrow-of-Time .
In otherwords , an object's 4-dimensional vector .
*Also called an object's "World-Line" .
>For a more detailed examination of this topic, go to thread:How does the expansion of space work ?
Focus on my posts .
Ref : www.thenakedscientists.com/forum/index.php?topic=79683.0new;topicseen#new
P.M.