You have some space. You want to protect it. We’ll call this your Home System, or HS for short. For ages your HS has been emitting light, and that’s a problem. If someone (say, me) decides they want to invade and subjugate your HS (annihilation is harder to solve) AND I have FTL travel I can just show up uninvited and the instant I do I will be able to see you (albeit a past version of you) but I will be invisible.
Yes, invisible. Not just hard to detect, but actually invisible. How? Because you’ve been emitting light forever, and the light I emit or reflect hasn’t gone anywhere yet. I wasn’t there to emit or reflect light (nor any other wave or particle).
So, practically: I travel at FTL to a light year distant from your system. I check it out and decide that I want to control it for some reason. I then travel at FTL speeds (meaning I’m ahead of the reflection of my armada, which will reach you in a year) to 179,875,474.8 kilometers from your HS. When I pop out of FTL travel it will take my light 10 minutes to reach you, and that entire time I’m invisible. All my readings of you and your HS are only 10 mins old.
Now I jump to a mere 17,987,547.48 kilometers away and I’m 1 light minute out from your HS. My sensors can now pick up activity in your HS that is EARLIER than my last reading (I know, that kinda cooks my brain a little bit too) and I diff things so that I can predict where everything was (most likely) and will be (most likely). I plot my targeting appropriately.
Now I jump at FTL again to as close a distance as I possibly can without running into something bad (like a planet). I deploy my munitions (beam weapons? kinetics? missiles? fighters? all of the above?). I’ve got all my targets pre-plotted and depending on how close I can get to you in my final FTL jump you’ll have something like fractions of a second to seconds to react before my incoming attacks start to hit your HS. I will then plot follow-ups in real time (missiles and fighters are great for this because they can be steered).
All of this basically sucks if you’re a HS. There are basically four ways of solving this problem:
- Go offensive – as soon as you can do FTL find and colonize or destroy every and any thing that might ever want to return the favor. This, unfortunately, might work. It explains the Romulans.
- Mine the hell out of space between you and the rest of the universe. Make it so that it’s basically impossible to ever plot targets without getting destroyed. A dubious solution.
- Abandon your HS for a life of space travel so that you are never sitting still long enough to be such an easy target. Also workable, but kind of a drag. Planets are nice places on the whole.
- Use FTL communications to mitigate the threat.
You’ll be happy to know that we earthlings are getting much closer to number 4 based on several amazing breakthroughs in quantum physics.
We’ve suspected for awhile that quantum tunneling will let us do something to something in one place and get an instantaneous (meaning infinitely FTL) response in another. Recent experiments are showing that this may actually be how things work.
This is the most recent example:
How does this solve the above scenario? With FTL travel + a comms network based on quantum tunneling you can now build millions or even billions of what amount to solar powered quantum webcams. Once these are out there, far away from the HS, they are picking up light that is light seconds, minutes, hours or even more ahead of the light hitting the HS in real time, but they are reporting back to the HS in real time.
Now, if I decide I want to invade you, you can have a heads up that I’m coming based at least on how long it takes me to plot my targets – which ought to give you enough time to plot your defenses. You can start launching waves of kinetics now, hoping I find myself in a shit-storm of rapidly moving ball-bearings that weren’t there before. You can detonate nukes, get your own ships deployed in reasonable places, or launch missiles. You have choices. Options make the fight at least a little bit less one-sided for static targets like your HS.
Astute readers will note that once if you have FTL you ought to be able to do a hack solution for this based on physically moving objects from one place to another. For example you put an FTL drive on your webcams and then when it picks up something that the onboard computer thinks is bad (like my invasion armada) it jumps back to the HS and dumps the data. This might work but it’s got all sorts of impractical issues (unlike this deeply practical blog post). For starters FTL is likely going to cost vastly more energy than quantum tunneling. It’s kind of like those pneumatic tube systems. Neat but not particularly scalar.
So, let’s hear it for quantum physics! Solving problems you might not have thought about and will never have in your lifetime.