In the “Masters of the Universe” movie there was a machine that let Evil Lyn(?) view what happened in the past to areas she was pointing the device at. It doesn’t seem to be mentioned here though:
I think that such a device that could tune into different times and even different locations in the past wouldn’t cause any time travel problems. If the machine was sensitive enough it would even be about to detect what sounds are happening in the past. It would cause some problems though - e.g. you could find out people’s passwords by slowly replaying video from the past. It would be good for court cases though.
I was wondering has that machine appeared in other movies or been mentioned by futurists or something?
It crops up a fair bit in SF stories - sometimes the physical range is limited (i.e. you can only track events that happened within a radius of where the device is situated), sometimes the temporal range is limited (you can watch what Shakespeare was up to, but not what someone did yesterday), sometimes, each event can only be viewed once.
The time viewer is a standard device in science fiction. That page only takes it back to the 1940s but it’s definitely older than that.
There are obvious privacy issues that such a device raises, and that’s the plot of Asimov’s “The Dead Past.”
Which laws of physics it violates probably depends on the exact details of its construction. I’m sure it violates some and therefore can’t really exist.
There are no fundamental physical laws broken by a time viewer. It’s fundamentally no different than what an archaeologist or paleontologist does: Studying something in the present to gain information about the past. It may not be practical to get information anywhere near as detailed as is described in science fiction, but that’s another matter.
Heck, a “voice machine” that could pull long-faded sounds out of the air (a demonstration picked up the Gettysburg Address) was the focus of several episodes of the 1940s Superman radio show. The plot segues when the characters point it at the city and happen across a conversation about a murder.
Here’s a kicker: suppose there isn’t really one fixed past? We don’t really know anything about the past; we know about the present, including our memories and what we observe, and deduce the past. If different possible pasts could converge on identical presents then maybe all of them are equally valid, and a time viewer would show different views weighted by probability until the past vanished into a fog.
Studying something means interacting with it. You have to detect/observe/record the photons involved. You’re either sending a probe into the past or picking up the photons instantaneously at a distance of x lightyears where x is the number of years they’ve existed or some variation. I can’t see any way that doesn’t violate causality.
That’s if you’re using photons. An object interacts with many other particles, many of them slower-than-light or stationary (in some reasonable choice of reference frame), and you could in principle get information from any of them.
Perhaps it isn’t possible to study past events to a very high level of precision an unlimited number of times… like how archaeology involves making some changes… or maybe there is a thing like X-rays that could involve things being analysed without really affecting the original…
The movie Final Edit is kinda based on this idea, but it is a special chip people are implanted with that records their entire life and is viewable on death.
Stephen Baxter visited the idea again in The Light of Other Days, which Clarke wrote the synopsis for. Clarke’s afterword discusses the use of such devices in SF.
I’ve seen stories with that theme as well. In one, the protagonist saw a different past, equally consistent with the present, each time he used the devide to see a particular past event. This was very disturbing for him when he watch the Resurrection and got multiple results.