yes and there's a reason I put in words like "subspace stuff" in my posts
Subspace is something in Trek that clearly allows for FTL stuff. Whether that's FTL movement (warping into subspace or however it works - we don't know) or FTL communications or sensors - Subspace is always the key word from some TOS, to lots of TNG and in DS9 and Voyager it's in nearly every episode.
In fact, Subspace is required for FTL movement at least - "Omega destroys subspace". Without subspace, Warp isn't possible.
I have zero (literally zero) issues with Federation sensors getting "real-time" data from places up to 20 light years away (I can cite, if you like, I'll need to look it up - but the Ent D can scan "one sector a day" and a sector is 20 by 20 by 20 light years), because of "subspace".
We know comms travel way, way faster than a ship can in FTL.
You want my theory?
To make an obect (even an atom) move at the Speed of light, it requires an absurd amount of energy. To the point it's impossible by known physics. I believe it requires *infinite* energy to propel normal matter - especially a starship - at the speed of light (let alone FTL).
E = MC^2.
Warp drives lower the mass of the vessel.
What if M is now equal to 0.1M (maybe warp 1). What if M is 0.0005M ?
And so forth. We KNOW warp lowers the mass of objects (Deja Q - they wanted to extend the warp field of the ship to the moon/asteroid, to lower its mass and THEN use the tractor beam to push it - it would mean making a big warp field - way bigger than normal - and extending it around all or part of the moon).
I think Warp factors are actually factors of mass lightening. And the higher the warp factor (lower the mass) requires more energy (warp engines / warp drive).
I think they use Impulse engines, as the "go forward", and the warp drive lowers the mass. Allowing the fusion drive impulse engines (which you see glowing when they're at warp, esp in TNG) to go beyond their normal speeds. Which can get to 0.7 or 0.8C by themselves (ST:TMP).
Or maybe they don't use the impulse engines to go forward and the warp engines also have a propulsion bit, idk.
The warp engines either lower mass or they push "deeper into subspace" (which itself could be a lowering of mass - again, we don't know).
we know:
Warp requires subspace (VOY: Omega, TNG, DS9, VOY: nearly any episode)
Warp engines reduce "intertial mass" (Deja Q)
Warp drive requires large (but not insurmountable) amounts of power - M/AM etc.
Real-time FTL comms work on subspace
I say:
Sensors work on subspace. And that's why they detect light / EM spectrum or gravity in real time, in far-out places.
"Subspace antennae" or "subspace array" has been mentioned a few times.
ALL other times comms (and sensors) have been FTL it's been because of a wormhole or similar thing allowing them to "see" the other side of the hole.
Incidently, that's why i think in SW: TFA we could see the 4 planets blow up at once from the surface of the star killer - we were looking "down" the "hyperspace tunnel" that the (quote) "Hyper-light weapon" used to get so far, so quick.
With all the above and the other discussion in the thread - and I'm usually one to stick to canon 100% btw, I'm Trekkie but I'm not rabid hehe - I am 100% happy that the Federation can detect "gravity" in whatever shape or form they choose, because of subspace. And they can do it in real time over FTL distances.
In ST:GEN, Data can say what the destruction of the Amagosa star will do and that Federation (and presumably other) ships have had to make course corrections, lightyears out (they're on other star systems on the map), already, to take account of this.
Federation tech (and most Trek races) can detect gravity fluctuations to varying degrees (we can already do it now, apparently!) FTL and in real time, with "gravetic sensors". Imo.
And whilst some of that is supposition, I think it holds, all things being equal.