Andromeda paradox and determinism?

[Dale]

If there is no experiment to prove the existence of space-like events (observer independent reality), then solipsism rules.

Irrelevant. Nobody is disputing the existence of space-like separated events. Only that there is any experimental method to choose between the block universe and LET. Neither LET nor the block universe implies solipsism.

Even a more extreme stance where you only assert the observer independent existence of events within your past light cone (and remain agnostic about any other events), still would assert the existence of space-like separated events since the past light cone contains many pairs of space-like separated events.

Your comments about solipsism are irrelevant and off topic for the forum. Nobody is promoting solipsism.

 

[15characters]

Thanks for the reply Naty. So in the particular case of the Andromeda paradox, the sequence of events on the Andromeda galaxy will be present in every distant reference frame, regardless of its motion. It's just the case that some observers will some events from the past of the Galaxy before another observer does (because of their relative distance). So it's something like the case that if we were really close to the sun we would see its specific past state before another observer on the Earth will, right?

I previously got confused by paradoxes until I understood how the plane of simultaneity works last week. In my opinion for beginners it is more important to understand

length X velocity = fixed time gap between observers

This phased time difference is key. It is calculated as relative velocity x distance. So for example at 0.5 c every light second of distance will produce 0.5 light seconds of time gap between observers. (0.5 x 1 = 0.5).

At 0.8c an event 10 light seconds away in distance will have a time phase gap of 8 seconds between observers ( 0.8 x 10)

The gap works both ways so if you are moving at 90% C then events 10 light years behind in distance will shift 9 years into the past while those 10 light years in front of you would shift 9 years into the future.

Example

We all see the photons arriving from the sun at the same time. Those stationary on Earth assume the photons were sent 8 minutes ago when the sun was 8 light minutes away. A passing spaceship at 50% of the speed of light, traveling past Earth towards the sun on seeing the same photons would see this a phase difference of 500 x 0.5 = 250 seconds.

What this means is they will assume events that we say happened on the sun NOW actually happen 250 seconds into the future or past - depending which way they are moving

For example moving towards the sun will move their sun 250 seconds into our future. They see

1) Earth and Sun rushing towards them at 0.5C.
2) Photons from the sun moving at C.

They would conclude that the photons just now arriving from the sun took some time to arrive and must therefore have been sent when the sun was further away from their current position than it is now (remember the Sun is rushing towards them). They will say this time was 250 seconds before what we think it is (8 minutes).

Therefore they will conclude the photons are from about 12 minutes ago not 8 minutes ago.

The formula for time phase gaps is simple = distance x velocity. Talk of moving clocks etc only confuses people.

Another example

Every passenger on the train has a clock. They all show the same time for people on the train.

From the outside to observers the train moves at 0.5C. For every light second of distance along the train the passenger's clocks appear 0.5 time seconds out of phase. Its a fixed phased gap related to distance.