I am not a physicist. So, someone with a better understanding please correct me when I mess this up.

I think that blurb about a spaceship flying to mars is largely equivalent to the planets spontaneously doing a step to the left around the space ship is the core of relativity.

That is points of perception in a Newtonian model, not relativity. Within a Newtonian model, all motion is

*relative* to the position or velocity of the point of view, but that is not Einstein's relativity. Concepts date back to Galileo. Nothing is 'fixed', everything is in motion relative to any other thing. There is no 'Jail' on the cosmic Monopoly game board. Simultaneously, though, proclaiming oneself as a 'static point' can make the math a lot easier.

In as much as I understand it, it's because e is constant that causes time to dilate. If you're travelling in some sense at 99% of e, you'll see light still moving at e. Because at normal time you'd see light travelling only 1% faster than you, time slows down by a factor of 100 to bring that 1% back up to 100%. But that would suggest it's speed, not acceleration that causes it, and how you square that with a dynamic universe without any fixed reference to measure against, I'm at a bit of a loss.

That is a lot closer to 'special relativity'.

Code:

```
https://www.space.com/17661-theory-general-relativity.html
https://en.wikipedia.org/wiki/Principle_of_relativity
https://en.wikipedia.org/wiki/Special_relativity
```

*Special principle of relativity*: If a system of coordinates K is chosen so that, in relation to it, physical laws hold good in their simplest form, the

*same* laws hold good in relation to any other system of coordinates K' moving in uniform translation relatively to K.

— Albert Einstein:

*The Foundation of the General Theory of Relativity*, Part A, §1

- The laws of physics are invariant (i.e., identical) in all inertial systems (i.e., non-accelerating frames of reference).
- The speed of light in a vacuum is the same for all observers, regardless of the motion of the light source.

The bit that always fascinated me has more to do with the equivalence of mass and energy - and what happens when a theoretical object approaches the speed of light. The old E=mc^2 thing. The Wikipedia article on Special Relativity cited above explains this well: "As an object's speed approaches the speed of light from an observer's point of view, its

relativistic mass increases thereby making it more and more difficult to accelerate it from within the observer's frame of reference." Conclusion: Interstellar star ships are really difficult to steer as their relative mass becomes infinite - as well as the energy needed to change direction...