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[Chiaroscuro]

The problem with people trying to understand faster than light travel or communication and causality is that they are seeing the scenario as a third party viewer (think point "d") observing eveything at once, with all the information available at once, which is impossible. As soon as they only have the information from only one of the parties involved they will start to see the problems

 

[maquiladora]

The SETI Institute is going to point their telescope array at this star system to see if any interesting signals will be found.

@SETIInstitute

Star KIC 8462852 is in the news. Its dimming might be due to alien constructions. Hang tight: The Allen Telescope Array is looking.

 

[Charles Foster Kane]

Nothing will be found

If we hear something though...

 

[Abstruse Moose]

Prepared for disappointment, hoping for excitement.

 

[SuperBanana]

The SETI Institute is going to point their telescope array at this star system to see if any interesting signals will be found.

Would sound have even reached us? Wouldn't it mean the structures were thousands of years old if we could?

 

[maquiladora]

Would sound have even reached us? Wouldn't it mean the structures were thousands of years old if we could?

Electromagnetic radiation travels at the speed of light. Visual light and radio waves arrive at the same time.

 

[gutshot]

Would sound have even reached us? Wouldn't it mean the structures were thousands of years old if we could?

The fact that we can see the structures already means they are thousands of years old. "Sound", or in this case radio waves, will be just as old of course.

 

[Pryce]

The thought of a civilization far advanced than anything we could dream of today blows my mind. In our own galaxy, even!

 

[Orbis Tabula]

Spacetime cares a hella lot about information about events (in part because that's sort of what events really are).They're right that in the "spaceships in flight" situation you actually can literally send information into the past. Maybe this is one that would actually be better with equations, let me see if I can find a good piece that goes through them in an understandabe way

If you have an explanation that goes through it with more equations, I'd be happy to check that out. The math, I don't expect, will intimidate me. SkyOdin's explanation makes sense to me, but I think the actual work behind it would drive it home for me.

 

[Jonm1010]

Isn't it possible that an advanced civilization has evolved their tech beyond using radio waves as a communication tool? So for us listening we won't hear anything because we missed the narrow window where they were using radio transmissions regularly and are now using some cool alien shit to communicate that doesn't leak out into space in a way radio telescopes could hear it?

 

[The Beard]

Would sound have even reached us? Wouldn't it mean the structures were thousands of years old if we could?

I think that's how it works. Anything we hear today would've been sent from "them" 1,500 years ago (if there is a them).

 

[SuperBanana]

The fact that we can see the structures already means they are thousands of years old. "Sound", or in this case radio waves, will be just as old of course.

Electromagnetic radiation travels at the speed of light. Visual light and radio waves arrive at the same time.

Oh of course. For some reason I'm thinking it travels at the speed of sound. Derp.

 

[80s Bad Guy]

The SETI Institute is going to point their telescope array at this star system to see if any interesting signals will be found.

 

[Simon Belmont]

That was not a good movie.

 

[maquiladora]

Isn't it possible that an advanced civilization has evolved their tech beyond using radio waves as a communication tool? So for us listening we won't hear anything because we missed the narrow window where they were using radio transmissions regularly and are now using some cool alien shit to communicate that doesn't leak out into space in a way radio telescopes could hear it?

It's possible, especially since SETI focus on the Hydrogen line and not the entire radio spectrum. But the theory is that even if aliens don't use radio waves to communicate. the technology involved in these huge theoretical space engineering projects would "leak" noise that we could detect as being artificial.

 

[SuperBanana]

The SETI Institute is going to point their telescope array at this star system to see if any interesting signals will be found.

One thing though. If a civilization is that advanced would they even use radio transmission? I mean, to build a planet sized object would be thousands of years more advanced than us, not just hundreds.

Edit: Jonm totally just asked that same question. Never mind!

 

[gutshot]

I wonder if we are still looking at a Jan timeframe for when SETI will investigate this system? Or if that timeframe has been accelerated due to the media interest? The tweet is sort of vague on that point but could be read as the latter.

 

[80s Bad Guy]

That was not a good movie.

I remember liking it when I was twelve. But to be fair my favorite movie at that time was The Lost Boys.

If they setup a complicated light-array signal they probably included audio backup for primitive cultures like ours also looking.

 

[The Technomancer]

If you have an explanation that goes through it with more equations, I'd be happy to check that out. The math, I don't expect, will intimidate me. SkyOdin's explanation makes sense to me, but I think the actual work behind it would drive it home for me.

Hm nothing I'm really happy with on searching first, but these two pieces are pretty good with diagrams
http://www.askamathematician.com/2012/07/q-how-does-instantaneous-communication-violate-causality/
http://scienceblogs.com/principles/2015/01/09/what-does-a-faster-than-light-object-look-like/

One of the important things to keep in mind is that sending a signal isn't, from a physical perspective, different than sending a person.

 

[Eteric Rice]

So when are they going to point at the star and check it?

 

[gutshot]

Oh of course. For some reason I'm thinking it travels at the speed of sound. Derp.

Yeah, the speed of sound is not a thing in space due to the vacuum. All communication in space is sent via light. Unless of course this hypothetical advanced alien race has developed an alternate method of interplanetary or interstellar communication.

Personally I find that a bit unlikely since any sort of theoretical non-light wave communication has a tendency to break causality (as has been illustrated in this thread) which makes it problematic.

 

[Orbis Tabula]

Hm nothing I'm really happy with on searching first, but these two pieces are pretty good with diagrams
http://www.askamathematician.com/2012/07/q-how-does-instantaneous-communication-violate-causality/
http://scienceblogs.com/principles/2015/01/09/what-does-a-faster-than-light-object-look-like/

One of the important things to keep in mind is that sending a signal isn't, from a physical perspective, different than sending a person.

Those diagrams did help. I guess the part I'm having trouble internalizing is this concept that what observers are seeing happen is what is happening. I'm having a hard time abandoning a gods eye view, so it's hard for me not to see it, like one of those links put it, as an optical illusion. That things look as if they're violating causality, when they're not. I'll need to work on that.

 

[3phemeral]

(Also even if you could, each particle would be good for sending precisely one instance of information. You'd need to re-entangle them to reuse them. So if you had 100 particles with binary states you could send one 100 bit message...once. Any further communication would require entangling more particles on one end and physically sending them to the other)

Ah, yes. People forget that entanglement isn't completely infallible in terms of information "transmission." That once the state of one entangled particle is changed and the other particle reflects that, their entanglement is broken. The only method I've read about entangling particles is for those particles to be physically together, then separated. Seems impractical to me unless, say, an ancient alien civilization somehow sent an entangled macro-quantum object into far-off region of space in hopes that some technologically capable life-form would understand its purpose and then send a signal back.

Isn't it possible that an advanced civilization has evolved their tech beyond using radio waves as a communication tool? So for us listening we won't hear anything because we missed the narrow window where they were using radio transmissions regularly and are now using some cool alien shit to communicate that doesn't leak out into space in a way radio telescopes could hear it?

Interesting thing on a recent episode of Startalk, Edward Snowden believes that if there were an alien civ protecting their communications, they'd likely achieve "perfect encryption" that would be indistinguishable from background noise.

 

[PrivateWHudson]

In respect to all of this, aren't we already experiencing time travel? Lighting cracks in the distance, but I don't notice it and the thunder scares me. However, if I was on the phone with a friend across town and he saw the lightning, and I heard the thunder through the phone and now knew that it was coming and braced myself for it...I wouldn't get scared. Didn't that faster than sound communication alter the future?

 

[TheLostBigBoss]

In respect to all of this, aren't we already experiencing time travel? Lighting cracks in the distance, but I don't notice it and the thunder scares me. However, if I was on the phone with a friend across town and he saw the lightning, and I heard the thunder through the phone and now knew that it was coming and braced myself for it...I wouldn't get scared. Didn't that faster than sound communication alter the future?

Huh? No, you're just receiver information faster than you would have without a communication device. You're not going faster or slower in time, you just have a scout giving you a heads up.

 

[cebri.one]

I believed SETI was moving away from detecting radio signals, aparently an advance civ may not emit one at all (edit: not really accurate, check below), as as it was discovered that the radio signature of the earth is also decreasing, i believe it was due to moving from analog to digital communications.

Edit: Found the article.

http://www.bidstrup.com/seti.htm

There is a new modulation technique that we have recently developed (mathematically, it is related to both AM and FM, but the resulting signal is so unlike either that it can for all intents and purposes be considered a new method). It is called "digital." Using a variety of techniques that result in both strenth and frequency shifts at the same time, the new digital methods produce a signal that, to an incompatible receiver, is totally indistinguishable from that receiver's own internally-generated noise.

 

[3phemeral]

In respect to all of this, aren't we already experiencing time travel? Lighting cracks in the distance, but I don't notice it and the thunder scares me. However, if I was on the phone with a friend across town and he saw the lightning, and I heard the thunder through the phone and now knew that it was coming and braced myself for it...I wouldn't get scared. Didn't that faster than sound communication alter the future?

Well, when you think of time travel, you can think of it in terms of:

1. Traveling to the past or future or
2. Time Dialation, where gravity physically effects the time-space you occupy, altering your clock relative to another (like you orbiting a black hole versus Earth's)

In your example the sound you're hearing isn't the actual sound produced by the crackle of lightning, but a simulation of it produced by the phone's speaker and transmitted using electricity, which travels near speed of light (1/100th). The sound itself is still traveling at its own speed and will eventually reach your ears, as you've said.

I think your reaction to the sound is more akin to jumping back onto a sidewalk curve because you noticed a car swerving your way, versus being engrossed in your phone and getting hit.

 

[BizzyBum]

Is it just me or have we been getting way more announcements and discoveries regarding space then we ever had before? Exciting times.

As for this star, that would be bonkers if an alien civilization was advanced enough to build a dyson sphere around their star 1,480 years ago. We were just entering the very beginning stages of the Middle Ages. It more likely to be something natural, but if it is alien, there could be three possibilities.

1. The civilization that built it is extinct / moved on (interstellar travel?)

2. The civilization is still there but has not contacted us, meaning interstellar travel and FTL travel is essentially impossible. If they could build something like a dyson sphere to harness the energy of their sun 1,480 years ago and if they are still around today, I can't imagine how much more advanced they are. They would be practically gods. But this is sort of a depressing scenario because that means a civilization almost 1,500 years after going Type II still cannot figure out how to acquire interstellar travel, that most certainly means it's impossible or at the very least something the human race won't figure out until thousands of years into the future, if at all.

3. They know we are here and are not interfering and perhaps even protecting us. This goes with the zoo hypothesis theory of the Fermi Paradox where intelligent extraterrestrial life exists and does not contact life on Earth to allow for its natural evolution and development. It could also be possible they are the enforcers of this law and protect us from other alien life to come and disturb us.

I WANT TO BELIEVE

 

[TheLostBigBoss]

Is it just me or have we been getting way more announcements and discoveries regarding space then we ever had before? Exciting times.

As for this star, that would be bonkers if an alien civilization was advanced enough to build a dyson sphere around their star 1,480 years ago. We were just entering the very beginning stages of the Middle Ages. It more likely to be something natural, but if it is alien, there could be three possibilities.

1. The civilization that built it is extinct / moved on (interstellar travel?)

2. The civilization is still there but has not contacted us, meaning interstellar travel and FTL travel is essentially impossible. If they could build something like a dyson sphere to harness the energy of their sun 1,480 years ago and if they are still around today, I can't imagine how much more advanced they are. They would be practically gods. But this is sort of a depressing scenario because that means a civilization almost 1,500 years after going Type II still cannot figure out how to acquire interstellar travel, that most certainly means it's impossible or at the very least something the human race won't figure out until thousands of years into the future, if at all.

3. They know we are here and are not interfering and perhaps even protecting us. This goes with the zoo hypothesis theory of the Fermi Paradox where intelligent extraterrestrial life exists and does not contact life on Earth to allow for its natural evolution and development. It could also be possible they are the enforcers of this law and protect us from other alien life to come and disturb us.

I WANT TO BELIEVE

Why does everyone assume that #2 means that FTL or near FTL is impossible?

1440 LY gap, meaning we are seeing them 1440 years ago and they are seeing us 1440 years ago. Why would they contact us, they wouldn't even know that we are here at that point in human history.

Not only that, but you're assuming that they want to go to every single world and go "Oh wow a planet we can colonize". If you're a type II civilization who can create a dyson sphere, that means you have an easy way to mine astroids and create large structures in space, which means that you will most likely be able to create massive artificial habitats in space that meet the needs of your specific biological makeup.

Why go to a planet, fuck up it's ecology just to create a few mega cities on it when you can leave the planet alone, let it evolve into what ever it evolves into and just roam around space with your perfect mobile habitat that can easily escape danger of your local start system if the sun decides to blow or something. Don't have to worry about super volcanos or giant earthquakes or simply waiting years and years of terraforming for a planet to be perfectly habitable.

 

[Turin Turambar]

In respect to all of this, aren't we already experiencing time travel? Lighting cracks in the distance, but I don't notice it and the thunder scares me. However, if I was on the phone with a friend across town and he saw the lightning, and I heard the thunder through the phone and now knew that it was coming and braced myself for it...I wouldn't get scared. Didn't that faster than sound communication alter the future?

Time travelling is breaking the speed of light, not breaking the speed of sound. We can even do planes that break the speed of sound.

 

[LookAtMeGo]

So if you build a Dyson sphere, does it have to be around the entire sun for it to work? If so, wouldn't it mean that you would have to travel to another star system to build one?

Like, wouldn't the sphere block too much light that it would be devastating to your planets ecosystem?

 

[TheLostBigBoss]

So if you build a Dyson sphere around the entire sun for it to work? If so, wouldn't it mean that you would have to travel to another star system to build one?

Like, wouldn't the sphere block too much light that it would be devastating to your planets ecosystem?

It doesn't sound like this is a dyson sphere where the entire structure is engulfing the sun, it sounds like it's a dyson ring type platform if anything

 

[MikeDown]

Time travelling is breaking the speed of light, not breaking the speed of sound. We can even do planes that break the speed of sound.

You don't need to surpass the speed of light in order to time travel, I can't pull up the documentation as I'm on a government computer atm. But I recall that there have been studies done where astronauts have traveled ahead in time by micro-seconds due to the higher rate of speed when orbiting, compared to our relative time here planetside.

 

[Jackben]

You don't need to surpass the speed of light in order to time travel, I can't pull up the documentation as I'm on a government computer atm. But I recall that there have been studies done where astronauts have traveled ahead in time by micro-seconds due to the higher rate of speed when orbiting, compared to our relative time here planetside.

lmao

 

[PrivateWHudson]

Huh? No, you're just receiver information faster than you would have without a communication device. You're not going faster or slower in time, you just have a scout giving you a heads up.

Well, when you think of time travel, you can think of it in terms of:

1. Traveling to the past or future or
2. Time Dialation, where gravity physically effects the time-space you occupy, altering your clock relative to another (like you orbiting a black hole versus Earth's)

In your example the sound you're hearing isn't the actual sound produced by the crackle of lightning, but a simulation of it produced by the phone's speaker and transmitted using electricity, which travels near speed of light (1/100th). The sound itself is still traveling at its own speed and will eventually reach your ears, as you've said.

I think your reaction to the sound is more akin to jumping back onto a sidewalk curve because you noticed a car swerving your way, versus being engrossed in your phone and getting hit.

Time travelling is breaking the speed of light, not breaking the speed of sound. We can even do planes that break the speed of sound.

Of course I know you're all right, I'm not Einstein and can't begin to do the math, I'm just trying to sort it out in my head.

To cave men, breaking the the sound barrier with comms first, then later with physical objects would have been magic. To have a plane show up before you could even hear it! What? I'd imagine you can't step out of a super sonic plane without being turned inside out, but we just know better and surround ourselves with technology to avoid that.

If someone shows up in our solar system before the even leave theirs would break every rule we know, but I like to think of a future where we've overcome that and have a piece of technology that could put us in a bubble that protects us from the consequences of breaking the rules.

 

[rallaren]

Spoiler

I tihnk it is us from the future.

 

[SkyOdin]

Nope, I still don't get it. You keep talking about perspective, or "relative to" an external observer. What seems to be the order of events don't really matter, causality is about the actual flow of events at a single point in space.

A and B are communicating with supra-luminic tools. Can B send a message to A's past from A's perspective? It doesn't matter if from B's perspective it was received in A's past, if A doesn't experience it that way. The analogy with the speed of light and sound difference seems correct, it just sounds like there is a discrepancy in the order of events, but there isn't really.

Yes, in my example, A was receiving a reply to their message before they sent the message in the first place. The reason I use the term "relative" a lot is because space and time are relative. There is no absolute or universal time. That is exactly why they call Einstein's model of the universe "Relativity".

In respect to all of this, aren't we already experiencing time travel? Lighting cracks in the distance, but I don't notice it and the thunder scares me. However, if I was on the phone with a friend across town and he saw the lightning, and I heard the thunder through the phone and now knew that it was coming and braced myself for it...I wouldn't get scared. Didn't that faster than sound communication alter the future?

*sigh*
The speed of sound and the speed of light are set by two completely different physical principles that are not at all comparable in any way. The speed of sound is based on the simple physical properties of the medium the pressure wave is passing through. That's why the speed of sound varies between whether it is passing through air, water, or solid materials. Sound waves are a type of physical wave that always move in respect to their physical medium. In situations where the medium is moving, the apparent speed of the sound wave will increase to match.

On the other hand, the speed of light is an absolute physical constant. It is set in stone. Any light wave will be observed to me moving at the speed of light, no matter what frame of reference the observer is in. This is because space-time itself bends to accommodate the speed of light. When we say that going faster than the speed of light means time travel, we are literally talking about the Back to the Future sort of sending messages to your past self.

So if you build a Dyson sphere around the entire sun for it to work? If so, wouldn't it mean that you would have to travel to another star system to build one?

Like, wouldn't the sphere block too much light that it would be devastating to your planets ecosystem?

A Dyson sphere is just a means of maximizing how much light your solar panels collect. It isn't really a special system, and there is no requirement for the coverage to be complete.

 

[Turin Turambar]

I get that it would produce a shit ton of energy, but wouldn't it block out the sun at the same time? That seems like quite the downside.

At that point your species has migrated to AI entities running on hardware that is on the surface of the sphere, so whatever.

 

[Turin Turambar]

You don't need to surpass the speed of light in order to time travel, I can't pull up the documentation as I'm on a government computer atm. But I recall that there have been studies done where astronauts have traveled ahead in time by micro-seconds due to the higher rate of speed when orbiting, compared to our relative time here planetside.

I mean backwards in time, not forward in time (with time dilation because relativity, that's what you refer to).

 

[Chiaroscuro]

The speed of light is s hard concept to understand for most people because it defies our common sense.

Sound waves are like every physical object, like let's say a train. If you are in a place and there is a train coming in your diection travelling at 100 mph, its speed is 100 mph. Now if you are on a car traveling at 50 mph going towards that train, the train relative speed to you is 150 mph. If you are travelling in tbe same direction as the train, the train relative direction to you is 50 mph.

Now light does not work tjis way. Its speed is always the same, no matter if you are "stoped" in a place, going in tje direction of its source or going away from its source. It s absolute,"c", not "c" plus or minus your speed. The space-time is relative to accomodate that property, meaming it will be distorced for that to happen.

 

[CitizenVectron]

You don't need to surpass the speed of light in order to time travel, I can't pull up the documentation as I'm on a government computer atm. But I recall that there have been studies done where astronauts have traveled ahead in time by micro-seconds due to the higher rate of speed when orbiting, compared to our relative time here planetside.

You have it mixed up a tiny bit. They haven't moved forward in time, they've actually moved slower in time. The faster you go (inside a frame of reference) the slower time is experienced by you. So a person on Earth might age 1 second, but a person in orbit might only age .99999999999 seconds. So they are in the same time as us at all times, but the rate of time they are experiencing is slower.

 

[ratcliffja]

You have it mixed up a tiny bit. They haven't moved forward in time, they've actually moved slower in time. The faster you go (inside a frame of reference) the slower time is experienced by you. So a person on Earth might age 1 second, but a person in orbit might only age .99999999999 seconds. So they are in the same time as us at all times, but the rate of time they are experiencing is slower.

To be fair, if you were somehow able to advance three minutes while the rest of the world advanced three years, you would certainly feel like you time traveled. With that said, I don't see any way that reverse time travel could ever be possible.

 

[abstract alien]

With that said, I don't see any way that reverse time travel could ever be possible.

Isn't there some strange shit in quantum mechanics where this seems to happen, like with the slit or observer experiments?

 

[SuperBanana]

Isn't there some strange shit in quantum mechanics where this seems to happen, like with the slit or observer experiments?

If you're talking about what I think you are I don't think it's time travel but atoms somehow knowing when they're being watched. It's very weird. When you get to a small enough scale the normal laws of the universe and thermodynamics no longer exist. However, I think reverse time travel would be a lot harder than forward. You could slow time around you to move forward but to go back you'd pretty much need to understand dimensions beyond us. I might be mistaken though...it's a hard subject.

 

[Jacksinthe]

1440 LY gap, meaning we are seeing them 1440 years ago and they are seeing us 1440 years ago. Why would they contact us, they wouldn't even know that we are here at that point in human history.

Why are we looking? Why do we scour the depths of our oceans? Mountains? Caverns? Space?

Curiosity, discovery, science, knowledge. Pick one or all of them. There's a myriad of reasons to poke around the cosmos.

 

[SuperBanana]

Why are we looking? Why do we scour the depths of our oceans? Mountains? Caverns? Space?

Curiosity, discovery, science, knowledge. Pick one or all of them. There's a myriad of reasons to poke around the cosmos.

We might be as uninteresting on a galactic scale as a possum in a tree is to us. You look at it and keep walking, you don't stop and interact with it because it's just a possum. We might be one of a million uninteresting inhabited worlds to someone who can build mega-structures.

 

[3phemeral]

If you're talking about what I think you are I don't think it's time travel but atoms somehow knowing when they're being watched. It's very weird. When you get to a small enough scale the normal laws of the universe and thermodynamics no longer exist. However, I think reverse time travel would be a lot harder than forward. You could slow time around you to move forward but to go back you'd pretty much need to understand dimensions beyond us. I might be mistaken though...it's a hard subject.

Well, it's not that the particle knows that it's being watched. More like the very act of observing affects the quantum property. To observe something, you need an object that measures said property and its that measuring device's interference that changes the outcome.

 

[God of Gamblers]

If the object/s causing the dimming of the light from the star is indeed from a Dyson sphere/ring/shell, with our present technology is there anyway of proving it? i.e. is our imaging tech advanced enough to distinguish.

 

[Measley]

That would be wild if we're surrounded by intelligent life and they're leaving us to our own devices until we either destroy ourselves, or rise to a level of relevance in the galaxy.

 

[Slayer-33]

If the object/s causing the dimming of the light from the star is indeed from a Dyson sphere/ring/shell, with our present technology is there anyway of proving it? i.e. is our imaging tech advanced enough to distinguish.

Doubt it, let's just hope that they find the radio waves

Also for everyone else wondering if ftl travel is impossible just because they've built a Dyson sphere... We'll I'm willing to bet that building a Dyson sphere is INFINITELY easier than solving the ftl issue. Specially when you take the manufacturing automation process into account for construction.

It doesn't have to to be perfect, as long as they solved the tech on how to harness a stars energy I bet even we can get a project like that started.