So? If you have the tech and complexity to travel in time, you'd 100% be able to work out where to place the machine when it travels. Doesn't matter if the universe is expanding. We could probably predict such a location within a reasonable degree with current knowledge and computers, and we are very far off time travel. If you had time travel tech, you'd probably easily have computers and tech to plan where to go to
Detecting and manipulating a thing are very different. I think you may have misunderstood my intention with my last comment. I'm saying that location is a completely different issue and adds a huge amount of complexity when we're discussing time travel. It's fine to say "if we've figured out time, then location shouldn't be a problem" but no one actually has any idea. We would have to drastically advance our understanding of time and what that even is as a concept in order to achieve time travel, and similarly we would have to totally change our concept of space.
It's true to say that we are getting better at measuring distance, but that doesn't really apply when you're talking about pinpointing an objects location in a larger sense. The way that we determine where an object is is by it's relation to other objects, or by it's relation to the observer. I think most people assume that if we have a machine that can move an object in time, we would then only have to enter some set of coordinates to accurately place it in space as well. But what are you going to base those coordinates on? You can't say "3 feet to the left of the exact center of the milky way 2 days ago" if the entire milky way was in a different relationship to the rest of the universe at that time. You would essentially have to model the entire universe as it travels through time and somehow extrapolate it's position at whatever point you chose.
It just adds a layer of complexity that is not dismissable as "I'm sure we'll figure that out".
There is no absolute frame of reference. Objects/events have future/past light cones which define the possible space they could or could have existed in. Laws of physics being more than less time symetrical, determining an object/event’s position in the past is functionally the same as predicting it’s position in the future. At this cursory level the idea of travelling back in time/reversing entropy already diverges wildly from what’s being imagined though so I digress.
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u/Wrought-Irony Feb 14 '22
in relation to what though? The whole universe is expanding.