(August 9, 2016 at 7:27 pm)abaris Wrote:

(August 9, 2016 at 6:20 pm)Excited Penguin Wrote: Except older civilizations out there could've sent plenty of messages that would've reached us by now.

Why? If their message missed us, as in today, by a measly century, noone would have heard the message. Hell, if they missed us by 55, 60 years, nobody would have noticed. Don't you realize how tiny that pinhead of reception still is?

They could've been sending messages constantly. One would assume they would have the resources for it.

(August 10, 2016 at 3:04 am)Excited Penguin Wrote:

(August 9, 2016 at 7:27 pm)abaris Wrote: Why? If their message missed us, as in today, by a measly century, noone would have heard the message. Hell, if they missed us by 55, 60 years, nobody would have noticed. Don't you realize how tiny that pinhead of reception still is?

They could've been sending messages constantly. One would assume they would have the resources for it.

That would make it easier certainly. We've been broadcasting unto space for something like 80 years.

I have to wonder how far away we would be able to detect our own broadcast noise with the technology we have today. I'd be surprised if it were more than hundreds to several thousand light years which would be relatively nothing at galactic scales. I wouldn't be surprised if it was a lot less.

I'll answer the OP in a minute, but something else - I think it's an intriguing question how interpersonal relationships would be affected by a 14 or 20 minute time gap. I imagine some friend or family member, maybe the wife or me being on a mission to mars for a couple of years or so. Would our conversations end up being like email or letters, containing a largely self-contained block of stuff, which gets answered by another largely self-contained block of stuff, or would it be more like a really slow conversation? Would people develop a strange kind of communication mode in which they find a rhythm where one person speaks, and when the recipient receives one of your pauses, gives the answer, thus having several conversations interspliced with time delays? I think this is a really interesting thing to explore for a fiction writer, too.

(August 9, 2016 at 6:01 pm)RozKek Wrote: I've come to notice that because of the speed of light, communication and discovering etc will be restricted between planets and solar systems. E.g if let's say we want to find distant life in another solar system we can't see what's going on at the moment because the light that'll have reached us would've been very very old. To make matters worse, let's say in the far future we populate another planet, let's use Mars as an example, communication between Earth and Mars takes around 14 minutes or so, and that's at the speed of light.

My question is, is there any possible/theoretical way to work our way around this obstacle?

(August 9, 2016 at 11:34 pm)Kosh Wrote: I'm not a physicist, but I do read a bit on the subject. I've always wondered if quantum entanglement could be used to create a faster-than-light communications device.

(August 9, 2016 at 11:57 pm)bennyboy Wrote: The point of QM entanglement is that it allows spooky action at a distance, and that this action is instant.  But I'm pretty sure that the entanglement effect would need a steady stream of newly entangled particles to "read."

According to what we currently know about the laws of physics, there doesn't seem to be a feasible way to break the speed-of-light barrier.

Quantum Entanglement - if you look at how causality plays out in Quantum Field Theory (that's currently the best experimentally secured description of quantum physics which also takes into account relativity), yes, there's this spooky action at a distance thing. But if you write down the mathematical formula for a communication at superluminal speeds, you find that the spooky particles and the spooky antiparticles exactly cancel each other out and you get zero; It's a famous textbook example, it's in my book as well - nature makes sure that no information can be transported until enough time has passed - as soon as enough time has elapsed, the quantum formula returns a number different from zero and communication is possible. It's the strangest thing, as if the universe had built-in machinery set up to hide superluminal messages from us.

Our only hope would be messing with space-time itself in order to shorten the path to the remote point by changing the geometry or topology of space. If you'd have a (as far as we know inexistent) substance with negative Energy, that would upset the maths of the above calculation, and information could travel faster than light (the recently often-discussed example is the Alcubierre Drive). But my personal opinion from what I've seen is that as soon as this kind of device would actually work, one would unavoidably run into time travel paradoxes. If wormholes in spacetime, connecting distant reaches via a shortcut, would exist, that would work, but it's not clear whether they can be stable and traversible without erasing everything that tries to pass them. So far, we haven't seen one. To make wormholes, one would probably again need this weird negative energy substance to keep them stable.

So my conclusion so far is that it's not completely out of the question that it might one day be feasible if some surprising physics discoveries happen, but so far, not much speaks in favour of the possibility.

I've been playing a lot of Elite recently where you can zip around solar systems beyond the speed of light. If you try to restrict your speed to below the speed of light it takes a really long time. If you stop and think about it, you realise just how big everything is. But conversely, it also struck me how slow the universe is.

Take two human bodies and information can be transmitted between each other seemingly instantaneously from the other side of the room. Yet light between two suns that far apart relative to their own sizes takes a long while to travel from one object to another.

But then the universe exists for billions of years rather than 80 years so taken over that time span maybe it isn't that slow?

(August 10, 2016 at 4:19 am)Mathilda Wrote: I've been playing a lot of Elite recently where you can zip around solar systems beyond the speed of light. If you try to restrict your speed to below the speed of light it takes a really long time. If you stop and think about it, you realise just how big everything is. But conversely, it also struck me how slow the universe is.

Take two human bodies and information can be transmitted between each other seemingly instantaneously from the other side of the room. Yet light between two suns that far apart relative to their own sizes takes a long while to travel from one object to another.

But then the universe exists for billions of years rather than 80 years so taken over that time span maybe it isn't that slow?

You can play the following game: How old are things compared to the time light needs to travel across them? Let's compare me and the Milky Way

Let's approximate my size with 2 Meters (it's actually 1.92, but 2 will do). That's about 6.5 nanoseconds, or 1/(150 million) seconds.
I'm roughly 40 years old, that's about 1.3 billion seconds (jeez what have I done with all this time???). This means that light has travelled across my length a whopping 2*10^17 times during my lifetime. So I'll define my relative age as

A_Alex = 2*10^17.

Now, it's hard to define a definite age for our galaxy, but it's about as old as everything, so let's say 13 billion years. Let's say it's 150 000 lightyears big. That means the relative age of our galaxy is only

A_Milkyway = 9*10^4

What this means is that indeed, the Milky way so far is a much slower object than myself even if you take its great age into account. During the entire past life of our Galaxy, you could have only sent 90000 messages back and forth between its corners, versus 200 quadrillion between my head and toe in my lifetime.

So you're saying you chose physics over basketball, yeah.

(August 10, 2016 at 4:42 am)Excited Penguin Wrote: So you're saying you chose physics over basketball, yeah.

I actually played basketball in a local team when I was in school, even some regional tournaments, but wasn't very good at it and kind of lost interest after a while...

(August 10, 2016 at 3:04 am)Excited Penguin Wrote: They could've been sending messages constantly. One would assume they would have the resources for it.

With infinite energy and infinite funds I suppose they could. But it takes a tremendous amount of energy and money to send out even a second's worth of signal being able to reach other solar systems.

Alex probably knows better than me, since I only read about the problem being brought up by astro physicists. There's a reason why we sent out Voyager 1 with a disk on board instead of continuously broadcasting signals.

(August 10, 2016 at 4:06 am)Alex K Wrote: According to what we currently know about the laws of physics, there doesn't seem to be a feasible way to break the speed-of-light barrier.

Quantum Entanglement - if you look at how causality plays out in Quantum Field Theory (that's currently the best experimentally secured description of quantum physics which also takes into account relativity), yes, there's this spooky action at a distance thing. But if you write down the mathematical formula for a communication at superluminal speeds, you find that the spooky particles and the spooky antiparticles exactly cancel each other out and you get zero; It's a famous textbook example, it's in my book as well - nature makes sure that no information can be transported until enough time has passed - as soon as enough time has elapsed, the quantum formula returns a number different from zero and communication is possible. It's the strangest thing, as if the universe had built-in machinery set up to hide superluminal messages from us.

Our only hope would be messing with space-time itself in order to shorten the path to the remote point by changing the geometry or topology of space. If you'd have a (as far as we know inexistent) substance with negative Energy, that would upset the maths of the above calculation, and information could travel faster than light (the recently often-discussed example is the Alcubierre Drive). But my personal opinion from what I've seen is that as soon as this kind of device would actually work, one would unavoidably run into time travel paradoxes. If wormholes in spacetime, connecting distant reaches via a shortcut, would exist, that would work, but it's not clear whether they can be stable and traversible without erasing everything that tries to pass them. So far, we haven't seen one. To make wormholes, one would probably again need this weird negative energy substance to keep them stable.

So my conclusion so far is that it's not completely out of the question that it might one day be feasible if some surprising physics discoveries happen, but so far, not much speaks in favour of the possibility.

Which paradoxes are we talking about here, and what would some possible solutions?