We’ve established that things don’t happen at the same time. This is true in almost all circumstances. Indeed, it has been shown that since we, humans, are in a gravity field, even our head and our feet don’t experience the same time frame.
How do we even function, you ask? That’s not too hard, everything moves slower than this tiny time difference, so we don’t notice it.
Last time, we looked at the speed limit of the universe and the top speed. By relating it to the human experience you will hopefully have got an idea of what it means when we say that nothing happens at the same time.
In your head, because we used, implicitly, this model, we had two people separated who had synchronised clocks. That implication is faulty, but it is fixable.
Let’s explore why it is faulty.
My clock says 10am. We’re going to assume it’s accurate to within some arbitrary limit. What do I mean. I mean that if you argue that the clock is a bit “out” I’m going to say that we can make it more accurate. Is this valid? Well, yes and no. It is certainly valid enough of our purposes, we have already made locks that are accurate enough to only lose or gain a second in a few billion years. That’s pretty accurate, specifically we can measure the difference in time passing between our head and our feet on Earth. It’s not absolutely true though, because there are fundamental uncertainties built in the universe. If you can accept that the clock is accurate enough that you will never see a deviation that is not caused by some other effect, then we’re good.
My clock says 10am.
Juno is 48 light minutes away. Remember that light travels at the speed limit of the universe, so we can make statements like this, it takes any signal at least 48 minutes to travel from Juno to Earth. Light does top speed, so it’s 48 minutes.
What time is it on the spacecraft?
At MY 10am Juno send a signal to Earth, a clock synchronising signal.
That “beep” is going to arrive at 10.48am my time.
Right well, let’s discount a few things. Acceleration and gravity will change things, let’s leave them out for simplicity, we can factor them back in after.
So what time did Juno send the signal.
Juno’s 10am is our 10.48am, because we don’t get the signal for 48 minutes, therefore, Juno’s 10am arrives with us those 48 minutes later.
I know I’m labouring this, but I’m going to mess with it down the road, partly due to sound physics, partly due to my fictional universe.
Now, we know that Juno sent a signal a while ago, but Juno’s now is synchronised with our now at 10.48.
That’s the closest we can be.
For the same reason, we can only be as near as 4 years away from Proxima. Note carefully what I said.
Now, you and I know that is the same as 4 light years away, that 4 year gap is how simultaneous we can be, at most. (I should probably say “least”)
So anything that happens at that star cannot affect us for 4 years, and we cannot affect that star for that same 4 years.
Good so far?
If you think you’ve understood this, you probably have, it’s not quantum physics. (Don’t get me started).
Alright, now we’re going to lay a little non-linearity on you. If you want to know about the weird stuff that comes with a universal speed limit, then you should look at this https://youtu.be/msVuCEs8Ydo. (It’s a really good intro, don’t be scared) There are a lot of people who explain it a lot better than me, but I am also arrogant enough to believe that there are still holes, gaps in the knowledge that have been “hand waved” over. (Bear in mind thought that I’ve been doing cosmic/quantum physics for 45 years as a hobby and I still learn things daily).
Not the point here though.
Here, in this article, I’m going to go for the fiction.
Specifically, I’m going to break the light speed rule and have a think about the consequences. It doesn’t matter HOW we break light speed, but again, in the interests of our heads not exploding, we’re going to ignore most of relativity, (as we have so far) exactly as I have been explaining some parts of it.
So, no time dilation, nothing like that, just classical travel as though we’re doing low speed and we cannot generally see the results of relativity without really accurate clocks.
What happens if one of the Mind Ships breaks the speed limit?
Let’s take a simple scenario. Let’s say that our spaceship, The RuleBreaker can travel, um at 4 times the speed of light. Remember, there is nothing special about light, but it does provide a convenient measure of the speed limit of the universe, precisely because light travels at top speed.
Let’s further assume that we can’t intercept any signals between the Earth and The RuleBreaker while in transit. (Because being able to do so has consequences that we’re not ready to discuss).
So, we send a signal to Proxima at 10am 4th July 2016. It is the “beep’ of our now.
It will arrive no earlier than (taking it to be exactly 4 years), 10am 4th July 2020. That is when our now will be at Proxima.
Our star ship takes off at the same time, 10am, 4th July 2016.
It arrives at Proxima on 4th July 2017. The RuleBreaker takes up an orbit and now awaits the signal that we sent at light speed from Earth, it won’t arrive for another 3 years.
Now, here’s the question, has The RuleBreaker travelled to the future or the past?
Earth’s now signal won’t arrive at Proxima until well into the future of The RuleBreaker.
The consequence of this is that we must say that The RuleBreaker has travel into the past.
How can we show this?
The RuleBreaker sends a signal to Earth immediately upon arrival at Proxima. That signal will arrive at Earth on 4th July 2021, a year after the original signal from Proxima. This means that The RuleBreaker has sent a signal from the past, (remember Proxima always lies 4 years into our past) to the future, to us, 4 years later.
So have we broken causality?
Any signals arrive at Proxima from Earth could now be intercepted by The RuleBreaker, but that signal would have to be sent after 4th July 2013, because those signals are the earliest that The RuleBreaker can capture, because before then it is not at Proxima to capture anything.
Let’s say that The RuleBreaker stays at Proxima for a year, until 4th July 2018. In that year it can capture signals from Earth that are sent up until date 4th July 2014.
So far we’re not in too much trouble, but we have clearly broken causality.
You’ll remember that in the first article I laboured the speed limit of the universe at length, and that was because I want to be able to make it clear, um, now, (I’m hilarious), that this idea, causality is directly influenced by the speed limit.
We should be clear now that the universal speed limit means that the consequence of any action doesn’t happen, (or for a certain point of view, even exist) until the effects have travelled to the place it is observed from.
That was a bit obscure. What I’m saying is that events at Proxima don’t happen as far as Earth is concerned for 4 years. By the same logic, events at Earth don’t influence Proxima for 4 years.
Until, that is, The RuleBreaker arrives at Proxima. Now, as far as the ship is concerned, the closest simultaneity is now 1 year apart, not 4, but the rest of the universe still uses that 4 year gap.
This means that a signal from Earth, sent at the same time as the star ship set off to Proxima still has 3 years before it, the signal, will arrive at Proxima.
We have broken causality. I’m going to call this the Minor Break in Causality. From a certain point of view we must have travelled back in time, because we can interfere with the natural and normal course of events. But, note, effect cannot come before cause here, there is still a linear time in everything that we have discussed so far.
Let’s make things a bit more desperate.
The Sun goes nova. (Um, I’m not sure it can, but for the sake of argument, that’s our scenario).
We’ve got a little colony on a planet of Proxima, and Earth has built another ship.
The sun goes Nova 10am 25th December 2020. We know it’s going to do this; it’s been showing signs. But let’s say we only knew yesterday, 24th December.
We know the destruction of Earth is coming, but, and you might not know this, Novas are so powerful that anything “only” 4 light years away will be affected too, rendered inhabitable. (So yeah, Proxima, don’t go Nova).
Yesterday we launched The Rulebreaker II, which also takes a year to reach Proxima, as with the original ship. It will get there 24th December 2021, which is three years before the destructive radiation of the Novas will get there, more than enough time to evacuate.
So, yes, we’ve broken causality, but so far only in a “we sped up simultaneity to a year instead of four years”, kind of way. Note, we’ve IGNORED relativity more or less. Deal with that after. This whole section is about going from the non-fiction to the fiction, and what that means.
I’m going to stop there and let that all sink in. Someone might pick holes in it, and I need a chance to revisit it as well.
It would be nice to have some non-spam comments that think about this idea.