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What I just realised - imagine we are living in the future and have colonized distant planets. We might need a new tense that indicates that an event has already happened on that distant planet, but due to speed of light limitations, this information has not yet arrived at the observer.

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Turkish has such flavors of past tenses. They are called "observed past" and "learned past" tenses.

As the names imply, one is used when you witness the event. The other is used when you forget that you witnessed or you heard it from someone else.

Wasn't there a paragraph or two about making up a tense for that in the Hitchhiker's Guide to the Galaxy?

Edit: found it: https://sites.google.com/site/h2g2theguide/Index/t/956236 (it was about time travel, close enough)

Is this not some kind of sneaky simultaneity? You're imagining some absolute "this has happened" where, in your perspective, it hasn't yet.

I'm interested if anyone qualified could fix this issue for me. When we look into the distance, we see things that we describe as "happening X years ago" based on their light-year distance to us. We imagine that in the actual present at that location, what we're seeing happened X years ago. Is this not implying some absolute time reference that shouldn't really exist?

That concept is indeed meaningless in special relativity. So much so that mathematically there is no way to write down an absolute point in time, you can only write down time relative to another point in space time. Ergo saying something like 'that place at [same time as my absolute time]' is not even possible.

I meant to say general relativity.

It could be possible to go faster than light and preserve causality. The problem is we don't know a way to do this -- all explored ways create contradictions based on the physical laws as we know them.

If you can imagine teleporting and still having a consistent timeline, then you can imagine going faster than light.

You can certainly imagine going faster than light, but that doesn't mean it's possible. Saying it could be possible is basically saying "our understanding of physics could be wrong". Technically correct, but at that point we aren't having a productive discussion. "Assume everything we understand is wrong -> we can now teleport"

Does it even have to be teleporting to break causality, to be honest? Given a long enough journey, wouldn't the Alcoubiere (sp?) drive accomplish the same thing? By making a warp bubble and folding space using gravitational forces, none of the laws of physics are broken and the user can still move faster than the speed of light (though it isn't possible due to the lack of anti gravity, which might not exist - so there's that).

Also: https://www.sciencealert.com/pulses-of-light-can-break-the-u...

It doesn't have to be teleporting. Any superluminal travel can break causality. As I linked elsewhere, Sean Carroll has a solo podcast episode[0] where he talks about a few methods by which time travel could be imagined to be possible, given our understanding of the limitations. As is the case with the drive you mentioned, it's often the case that it's something like "well, if we imagine some special case that we don't think is forbidden, we can do xyz". I imagine at some point a few of these not-technically-forbidden holes will be blocked, but also it's not a certainty that all that is true can be shown to be so.

Your link really doesn't provide any basis for FTL travel.

[0] https://www.preposterousuniverse.com/podcast/2020/11/23/124-...

No, I know it doesn't provide any basis for FTL travel. It was more a link for the commentors stating that nothing can travel faster than light. I should have labeled it better =/

Well, it doesn't really show something travelling faster than light, any more than if you shot a laser at the moon and looked at the speed of the dot on the surface as you moved it through some angle. The dot can move arbitrarily fast, but nothing in the system is actually moving faster than light.

What is impossible for reasons related to space and time and light is going faster than light in the typical ways. It does not mean going faster than light is universally impossible, just those ways.

We are pretty sure FTL or “stargate” style teleporting would break causality. If anything like this is possible it means the universe is far, far stranger than we have imagined.

My understanding is that maximum speed is defined when going through space so light speed is maximum speed while going through space.

But I think theoretically we can defined travel through spacetime (or by transforming space itself) or something similar where a distance can seem to be travelled at higher speed than light is measured as space. I am thinking about this as I heard that when thinking that our Universe expands so each two galaxies lets say depart from each other will eventually speed up “faster than light” in the sense that the space itself expands.

Or I can be very wrong so please correct me.

Disclaimer: uneducated ignoramus posting.

Does that apply to wormholes, assuming wormholes are a thing and we ever develop a method to warp spacetime arbitrarily?

Wormholes aren't true FTL travel, they change the geometry of space such that there's a new shortest path for light to travel from A to B. Setting up a wormhole between two points requires slower than light travel to extend the wormhole ends. But after initial setup it would still be amazing :-)

If you're interested in some simplified-but-still-roughly-rigorous discussion about the physics of time travel/causality, Sean Carroll did a solo episode of his podcast where he talked about a few different ideas in this space.

https://www.preposterousuniverse.com/podcast/2020/11/23/124-...

“Going faster than light” is impossible. The intuitive concept of velocity as something that can be infinitely scaled isn’t how real relativistic velocity works.

“Teleporting” and “having a consistent timeline” are oxymorons.

We wouldn’t know about such events until light reached us anyway - light is the speed of causality, so we’d never apply this tense you propose.

Was just going to say that we should perhaps start with using the term “speed of time” instead of “speed of light” to get in the right frame of mind.

But then I started to think about it and it doesn’t seem exactly right either. Causality kind of implies interaction, and interaction implies mass (no?), so causality as such must necessarily be strictly slower than C. That is, the speed of the propagation of the wave function between causally connects to events is C but causality as such are the interesting things happening at those events.

> interaction implies mass (no?)

Not necessarily. Photons, for example, are massless. But you're still pretty much correct. Information cannot travel faster than C.

Though there may be some special cases that I'm not too familiar with. One I'm a little curious about is entangled quantum particles, though I'd have to do a little reading to be able to say anything further.

Entangled quantum particles cannot transfer information, regardless of your interpretation.

You might know that something will happen, but it hasn't happened yet in your reference frame. I guess this is actually just the return of the past, where you wouldn't know something had happened yet if it were thousands of miles away. I wonder if there's remnants of that time in the language used.

Well, if you observe two black holes moving towards each other, you might conclude that they "will" collide, But at the time when you made this observation these black holes have already collided, you just have not observed that. It's like using future tense. "I will go to work tomorrow", event though you don't know for sure if you will go to work tomorrow.

We might, but Relatively makes it counterintuitive.

In the past/future you find all the stuff within the corresponding light cone. The stuff outside the cones can flip between being what seems (non-Relativistically) like it should be past and future, can be either depending on your motion relative to it, so an extra tense for spacelike separation is something I can imagine a sufficiently advanced civilisation using.

It could be useful when discussing lightcones of others.

If we have two alien neighbour planets aranged so, that we are in the middle between them.

Then we could see both aliens' election results at the same time, knowing that aliens still have to wait a bit before they know each other's results.

We have words for infinity and shit that would never be “applied” but are useful logically.

> has already happened

This isn’t well-defined for events outside your light cone. Of course we could introduce an outside-one’s-light-cone tense.

But NASA already has that situation with their Mars rovers already. When ever those do something, its always 5-20 minutes when you know it has already happened but the signal is not on earth yet.

It is not just the future that needs it. Time travel stories are part of our mainstream fiction and so we need to deal with time travel tenses when discussing the plots of those stories.

Here's what can happen with our current tenses if you try to discuss the popular movie "Back to the Future": https://www.youtube.com/watch?v=VLpUlmiVo2k

We have this in my native language; adapted to English, it would sound like <It will have happened>. Three black holes will have merged in a nearby galaxy.

Maybe we could borrow from our distant (or not so distant) ancestors, where an event might have happened on the other side of this planet, but due to the speed limitations of ships sailing the ocean, this information had not yet arrived at the observer.

https://en.m.wikipedia.org/wiki/Light_cone

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