13 ms·
Given the centre of the Milky Way is about 26000 light years away, shouldn't the title read "was" instead of "is being"? And if so, wouldn't adherence to HN's
by detrites 4y ago
Given the centre of the Milky Way is about 26000 light years away, shouldn't the title read "was" instead of "is being"?
And if so, wouldn't adherence to HN's context policy require suffixing with a "(23977BC)"?
- baq 4y agoIt happened there then. We see it happen here now. We couldn’t have known about it in any other way, so for us it doesn’t really matter that it was there then.
- ericrallen 4y agoWhen will then be now?
- krapp 4y agoSoon.
- jjulius 4y agoWhen will soon be then?
- canadiantim 4y agoNow.
- geerlingguy 4y agoThis sounds like an excurb1a video.
- ricksunny 4y agoIt's a brilliant reference to Spaceballs https://youtu.be/5drjr9PmTMA https://youtu.be/5drjr9PmTMA
- kshacker 4y agoMay be it did not happen. May be Doctor Who or Captain Picard or someone not only saved themselves but also pulled the object out. Until it is confirmed to be sucked in completely, jury is still out on this one
- andrewflnr 4y agoHN title dates refer to the date of the article, not the event it covers. A 2019 article about an event on earth in 4000BC would still get (2019). But please do ignore the people confusing the delay in seeing distant events with relativistic simultaneity. It definitely did happen already in our reference frame. Just think of all astronomical events as being implicitly timestamped by observation time, not actual time. After all, distance is hard to measure in space, which means observation time is the more solid reference point.
- kryptiskt 4y agoIt's best to talk about it as if it's happening now. It is happening now from our perspective, and if we were to refer to it in past tense talking about its near future (in our past but in the object's future) would tie us up in grammatical knots instead of just being able to use future tense.
- thethimble 4y agoIf you think about the speed of light as the speed of causality then it is happening “now” in the sense that its effect is perceptible to us now. This seems like a good definition of now. Grammar becomes complicated when relativity dictates that there’s no universal ordering of events/timeline.
- leoqa 4y agoI suppose there is a universal ordering as a function of your position in the universe. Given that it’s impossible for an observer to be in two places where relativity differs, that simplifies to “there is exactly one universal ordering of events for each observer”
- thethimble 4y agoNot so “universal” if it’s per-observer, right?
- wizzwizz4 4y agoThere's a universal partial order of events. If something's in your future light cone, or your past light cone, that fact is independent of the observer. For the things that are not dependent on your present, and do not affect your present, different observers can have different understandings of the order.
- startupsfail 4y agoStatements “something is in your future” and “that fact is independent of the observer” seem incompatible. When you are saying “your”, you are talking about that particular observer, so you are negating the “independent” part.
- Aperocky 4y agoThe cone of causality establishes a present time for all events that we are able to know. There are no universal time across the universe due to relativity, so the only time that make sense and can be determined with any degree of accuracy is when it happened from our perspective.
- gpderetta 4y agoThat's litterally true for everything. Even something that's happening right in front of you has technically happened a few nanoseconds in the past. I do appreciate the HN joke though.
- Sir_Liigmaz 4y agoThe idea of simultaneity kinda breaks down on those kind of scales
- karaterobot 4y agoI think you've got tongue in cheek, so here's an upvote and a non-didactic reply.
- pizza234 4y agoAn astronomer on Reddit* says: > because the light we see is ~25k years old from the center of the galaxy, we are seeing it as it was 25k years ago. However, in astronomy we do not worry about this and instead just use the time at which the light reaches Earth- firstly there is just no way to know what is happening there literally now so in their view, it seems assuming the event as present is the norm. *: https://old.reddit.com/r/science/comments/11bk0u1/a_mysterious_object_is_being_dragged_into_the/j9yq00e/ https://old.reddit.com/r/science/comments/11bk0u1/a_mysterio...
- chongli 4y agoWhen you look at anything you are seeing what it looked like at least a few hundred picoseconds (very close to your face) to several nanoseconds (around the room you’re in) in the past. The difference here is a matter of degree, not kind.
- bcbrown 4y agoLight travels a foot per nanosecond, more or less. I believe this can be a real constraint in IC/motherboard designs with gigahertz+ clock speeds.
- nine_k 4y agoIt's called "spacetime" because space is inseparable from time. Any distance in space means a distance in time. Things happening "at the same time" are a convenient fiction applicable at short distances. Even things "happening in a particular sequence" is a fiction, if one events is not causing the other: what "happens first" depends on where you are looking from. Speaking about something beinng N lightyears away from us just means both the distance in space and time. What we are seeing happening there and then is not from our past: it could not affect our past because the light from that event hadn't arrived to us when and where our past was happening, and thus could not affect our local past. We see it happening "before" our past, but observers elsewhere may see it happening "at the same time" or "after" our past, in their frames of reference.
- detrites 4y agoIsn't this all based on the dogmatic assumption that nothing may ever traverse space faster than the light? There are potential ways in theory, and it's arbitrary to assume what's achievable now is all that ever will be.
- swayvil 4y agoGiven the time-dialation effects near the black hole, all that time may have passed in a day, relative to the object's perspective. It might be as much today for it as it is for us.
- rhaway84773 4y agoIm not sure that would be correct. It would assume there’s an absolute scale of time. But the whole point of relativity is that there is no absolute scale of time. Time differs based on the observer. So any time that we describe should be based on an observer on earth, because the overwhelming majority of HN readers are on earth.
- willis936 4y ago"c" isn't "the speed of light" so much as "the speed of causality". Light just happens to be massless packets of energy that move at the speed of causality. For all intents and purposes this is happening in real time from our local frame of reference. https://youtu.be/msVuCEs8Ydo https://youtu.be/msVuCEs8Ydo
- rhaway84773 4y agoRealizing that most often when we discuss the speed of light we’re not actually discussing the speed of light, but rather the speed of causality, was a huge eye opener for me. The speed of light is not always c. That’s why refraction happens. Because light slows down in certain mediums below c. It’s kid of a coincidence that the speed of light happens to be c in a vacuum (actually I’m not sure about this…maybe there’s an organic reason why electromagnetic waves will be c in a vacuum that is fundamental). I do think it’s interesting that as humans our primary sense is to light which does happen to travel at c. I wonder how different our species would be if we couldn’t sense waves traveling at c, and for example, were only capable of detecting sound. Alternatively it may be that a species which could not sense waves traveling at c would not be capable of becoming as sophisticated as humans.
- Matumio 4y agoDangerous speculation. One day, you will either step into a dark room and get eaten by a grue, or be killed by a gigantic bat who overheard your comment about her intellect. More seriously, I don't think speed-of-light has much biological relevance. It has consequences for microchips, though.
- anonymouskimmer 4y agoI kind of don't like this interpretation of events. The speed of causality varies depending on the speed of the causal particles and waves which propagate from an event. I was just reading an article on surviving nuclear detonations, and from those you have a few causal events propagating at different rates: the radiation, the shockwaves, the fallout. And if a tree falls in a forest with no one around, it does still make a sound.
- awb 4y ago> about 26000 light years away about makes this suggestion completely impractical
- detrites 4y agoAlright, 26673 LY within 0.3% accuracy: https://www.aanda.org/articles/aa/abs/2019/05/aa35656-19/aa35656-19.html https://www.aanda.org/articles/aa/abs/2019/05/aa35656-19/aa3... (So "24650BC" for... context.)
- awb 4y ago0.3% is +/- 80 years. So it’s not 24650BC, it’s 24570-24730BC. And the farther distance you go, the greater the uncertainty. And when measurements improve or are revised, everything would need to be recalculated. So, for posterity, it would be 24570-24730BC (2023 measurements). Or, 2023 is simpler.
- grey-area 4y agoOnly if you choose a parochial frame of reference like a small planet in the middle of nowhere instead of the centre of the galaxy.
- antod 4y agoDoes parochial mean that someone still thinks digital watches are a pretty neat idea?
- grey-area 4y agoNo, it means with limited horizons, or a limited frame of reference. I imagine core civilisations would have a good laugh at someone on the outer arms of the galaxy attempting to impose their frame of reference as preferential.
- delecti 4y agoThere are no privileged reference frames. Choosing your own reference frame is perfectly valid.
- grey-area 4y agoSure, what's invalid is expecting everyone else to share it.
- jrootabega 4y agoIsn't it even more technically accurate to say that it hasn't happened yet, and actually won't ever happen, in our frame of reference?
- xwdv 4y agoThe event has already happened, even though we cannot see it yet. There is no way to reach some state where you could still exist in a universe where the event hasn’t happened. If you traveled at the speed of light to the event location, you would see it has already happened. Since the speed of light is the fastest possible movement, there is no way to arrive at the event location faster than that, any faster movement means you would be time traveling back into the past in attempt to reach the event before it happens. Any possible event that happens in our daily lives starts off with two possible states: happened or didn’t happen. When one of those states is eliminated, the event status is resolved and reality is updated. Usually we see these updates occur damn near instantly. In this case, in this universe, the “didn’t happen” state has been thoroughly eradicated. But at these distances, we don’t see updates yet, but it has happened. Therefore, you can consider the event as having happened. It was… inevitable.
- jrootabega 4y agoThe object has been fully dragged across the event horizon into the black hole?
- anonymouskimmer 4y ago> Since the speed of light is the fastest possible movement, there is no way to arrive at the event location faster than that, any faster movement means you would be time traveling back into the past in attempt to reach the event before it happens. I don't quite get the time travel bit. I've seen too many sci fi and fantasy shows where time is effectively frozen while supernatural entities move about. Other than the supernatural entities moving about, the instant is the same everywhere, it doesn't go back. And if I see an event at Alpha Centauri, and immediately teleport there, the light wave is still at Earth. I haven't traveled back in time to the origination of the light wave at Alpha Centauri. And my light wave will not reach Earth until another ~4.3 years has passed after the first light wave that prompted my journey to Alpha Centauri. So the observer will not see anything unusual. I will not have rewritten the light pattern they saw. Also I think astronomers do see events which appear to be violations of causality, but are actually just gravitational distortions of the light traveling from an event. So interference with the travel of light from an event can't really be seen as traveling back in time.
- golergka 4y agoNot really. Time is relative, not absolute.
- jker 4y agoLighten up, Minkowski.
- mckirk 4y agoLet's just say 'it will have been dragged' to be on the safe side either way.
- analog31 4y agoThis issue is raised whenever there's a discussion of things happening at a great distance. In my view, a convention of reporting the time when something is observed on earth, and maybe the distance if it's not commonly known, is a reasonable one. Anybody is free to convert the number to their preferred reference frame.
- babyshake 4y agoIt is always mind-blowing to remember that in the astronomical scale, it is impossible to know things that are happening right now or relatively recently by our standards unless there is information traveling faster than the speed of light, which is something that at this point remains purely in the realm of science fiction as far as we know.
- andsoitis 4y agoFor this reason, I also don’t see how we could ever travel at faster than light speeds because we wouldn’t have the information that we won’t crash into something at the other end.
- cronix 4y agoYes, but I think once we reach that point we'd also be sending out some sort of mapping probes to gather data so you know where obstructions are. And since lots of things don't just sit still, they'd have to be constantly reevaluated somehow. Maybe sensors sending out data of what lies ahead kind of like our GPS. It will be an interesting issue to solve if we make it that long. But looking at how we're doing in our infancy with "self driving," we quite a long ways off lol.
- mrtweetyhack 4y ago[dead]
- geonnave 4y agoIn the Dune novel, the solution for this was a kind of evolved/specialized human kind that was able to see a bit into the future (with the help of a "drug", the Spice). Only this kind of "human" could be a pilot of a faster-than-light spaceships.
- photochemsyn 4y agoWhose relativistic frame of reference? My relativistic frame of reference!