Not unless they beam a signal at us. Or do mega-engineering, create huge obviously artificial structures in space.
If they are just going about their own thing, and have efficient technology that doesn't leak much, or they don't have technology, we'd never know.
Even if they have technology and actively try to communicate with us, they would need to be very dedicated to send signals into space for hundreds of millions of years continuously in hope that someone spots them eventually - and if they only do it as a short term project for a few centuries or millennia, it would be an amazingly lucky chance to spot them just at the moment when they do the transition, over periods of many billions of years.
However this is just one example. There are many nearby planets that may well be habitable. List of nearest terrestrial exoplanet candidates
And even restricting search to sun like stars, quite a few nearby G stars.
Even Alpha Centauri, closest G type star known to Earth, only 4.24 light years away, only a little further than Proxima Centauri, the closest known star to Earth, could have planets in its habitable zone.
These authors in a 2008 paper raised the possibility that we could detect those planets: Page on arxiv.org
And there is a search underway to try to find them: The Mt John University Observatory search for Earth-mass planets in the habitable zone of α Centauri
If there are Earth mass stars orbiting Alpha Centauri in its habitable zone, then we will be amazingly lucky as G stars are rather thinly spread, for such a near neighbour to be a G type star is rather lucky. None others amongst the nearby stars until you get to Tau Ceti over 10 light years away.
List of nearest stars and brown dwarfs
With a close by star, then we could spot the way that life makes a difference to the atmosphere, or even e.g. spectroscopic signatures of some prevailing chemicals in its vegetation (or whatever the equivalent is), e.g. chlorophyll. This would be a very delicate measurement, but we have already made spectroscopic observations of the atmospheres of some nearby gas giants, so not beyond our capability, to get started on learning about the composition of the atmospheres of nearby Earth like stars, especially with next generation telescopes such as James Webb.
We have even managed reflection spectroscopy - not just how light is affected as it passes through a gas giant's atmosphere - but also the spectrum of the surface of the planet, for a "hot Jupiter"
First visible light spectrum from exoplanet observed
But - that's just searching for life. As for intelligent life - even for nearby stars could easily miss intelligent life.
We could even have intelligent life in our own solar system in the oceans of any of the moons or dwarf planets that are thought to possibly to have liquid ocean interior shells below the ice - and again - we'd never know, not yet, and they wouldn't know about us if non technological as is quite likely in such a situation (so far we have no way to see into these oceans, and if non technological they would probably have no way to know even that there is a universe outside of their ocean and no way of getting out of it - to them, their ocean would be the entire universe almost certainly). There would be no sign at all of a civilization in the ocean of an icy moon around an exoplanet, there wouldn't even be any sign of life at all at that distance if the planet or moon is covered by a layer of several kilometers of ice - so there's a strong observer bias here - we can only spot very limited types of civilizations and types of life. Civilizations with radio signals or such like if not too far away - and forms of life that make changes to the atmosphere or the surface of their planets which can be noticed by spectroscopy from a long way away.
We could spot a civilization which transmits or leaks radio signals if it is really close. If close enough, just a few tens of light years away, chances are they've spotted us already.
At 1400 light years away, not likely to detect them unless they get into mega-engineering in a big way or leak huge amounts of radio energy etc . But it might be that as ETs get more advanced, they leak less energy and are more efficient in how they use it so harder to detect.
As for them contacting us, they would see Earth as it was 1400 years ago - no matter how sensitive their detectors, they wouldn't know that we have developed radio technology but might be able to detect life on our planet, and so we might be a target of their radio transmissions or optical laser transmissions if they do happen to have a very long term probably hundreds of millions years long ET contact program directed towards all the known nearby potentially habitable planets just on the off-chance that technological species eventually evolve on them.
If they just broadcast to us, say, for a century, out of billions of years - we'd have to be amazingly lucky to evolve to the point where we can detect them during that very century when they try to contact us (or rather, tried to contact us exactly 1400 years ago to the nearest century).
Or we have to wait for hundreds of millions of years before we contact them. So - especially if you try to contact a civilization about a particular star - then if you do make contact, one or the other of you has to be very patient, and either broadcast, or listen, for a very long time. Or one of you has to be very noisy in the radio or optical spectrum or do mega-engineering in a big way.
Claes Wallin has just mentioned in the comments: there's research into the possibility that we could also spot intelligent extraterrestrial life if they are polluters of their planet e.g. create CFCs etc. A New Approach to SETI: Targeting Alien Polluters. Though it might be that only immature young ETIs like ourselves do that. More generally, if their industry or technology transforms their planet's atmosphere or surface in some obviously artificial way, that could be a clue for technology, and so indirectly, for intelligence (or something like intelligence). This again would be far easier for nearby planets. It's probably going to be some time before we can do spectrosopic observation of the atmosphere of Kepler 452b.
See also: Robert Walker's answer to How can NASA be assured of potentially favourable living conditions just by looking at Kepler 452B?
If they are just going about their own thing, and have efficient technology that doesn't leak much, or they don't have technology, we'd never know.
Even if they have technology and actively try to communicate with us, they would need to be very dedicated to send signals into space for hundreds of millions of years continuously in hope that someone spots them eventually - and if they only do it as a short term project for a few centuries or millennia, it would be an amazingly lucky chance to spot them just at the moment when they do the transition, over periods of many billions of years.
However this is just one example. There are many nearby planets that may well be habitable. List of nearest terrestrial exoplanet candidates
And even restricting search to sun like stars, quite a few nearby G stars.
Even Alpha Centauri, closest G type star known to Earth, only 4.24 light years away, only a little further than Proxima Centauri, the closest known star to Earth, could have planets in its habitable zone.
These authors in a 2008 paper raised the possibility that we could detect those planets: Page on arxiv.org
And there is a search underway to try to find them: The Mt John University Observatory search for Earth-mass planets in the habitable zone of α Centauri
If there are Earth mass stars orbiting Alpha Centauri in its habitable zone, then we will be amazingly lucky as G stars are rather thinly spread, for such a near neighbour to be a G type star is rather lucky. None others amongst the nearby stars until you get to Tau Ceti over 10 light years away.
List of nearest stars and brown dwarfs
With a close by star, then we could spot the way that life makes a difference to the atmosphere, or even e.g. spectroscopic signatures of some prevailing chemicals in its vegetation (or whatever the equivalent is), e.g. chlorophyll. This would be a very delicate measurement, but we have already made spectroscopic observations of the atmospheres of some nearby gas giants, so not beyond our capability, to get started on learning about the composition of the atmospheres of nearby Earth like stars, especially with next generation telescopes such as James Webb.
We have even managed reflection spectroscopy - not just how light is affected as it passes through a gas giant's atmosphere - but also the spectrum of the surface of the planet, for a "hot Jupiter"
First visible light spectrum from exoplanet observed
But - that's just searching for life. As for intelligent life - even for nearby stars could easily miss intelligent life.
We could even have intelligent life in our own solar system in the oceans of any of the moons or dwarf planets that are thought to possibly to have liquid ocean interior shells below the ice - and again - we'd never know, not yet, and they wouldn't know about us if non technological as is quite likely in such a situation (so far we have no way to see into these oceans, and if non technological they would probably have no way to know even that there is a universe outside of their ocean and no way of getting out of it - to them, their ocean would be the entire universe almost certainly). There would be no sign at all of a civilization in the ocean of an icy moon around an exoplanet, there wouldn't even be any sign of life at all at that distance if the planet or moon is covered by a layer of several kilometers of ice - so there's a strong observer bias here - we can only spot very limited types of civilizations and types of life. Civilizations with radio signals or such like if not too far away - and forms of life that make changes to the atmosphere or the surface of their planets which can be noticed by spectroscopy from a long way away.
We could spot a civilization which transmits or leaks radio signals if it is really close. If close enough, just a few tens of light years away, chances are they've spotted us already.
At 1400 light years away, not likely to detect them unless they get into mega-engineering in a big way or leak huge amounts of radio energy etc . But it might be that as ETs get more advanced, they leak less energy and are more efficient in how they use it so harder to detect.
As for them contacting us, they would see Earth as it was 1400 years ago - no matter how sensitive their detectors, they wouldn't know that we have developed radio technology but might be able to detect life on our planet, and so we might be a target of their radio transmissions or optical laser transmissions if they do happen to have a very long term probably hundreds of millions years long ET contact program directed towards all the known nearby potentially habitable planets just on the off-chance that technological species eventually evolve on them.
If they just broadcast to us, say, for a century, out of billions of years - we'd have to be amazingly lucky to evolve to the point where we can detect them during that very century when they try to contact us (or rather, tried to contact us exactly 1400 years ago to the nearest century).
Or we have to wait for hundreds of millions of years before we contact them. So - especially if you try to contact a civilization about a particular star - then if you do make contact, one or the other of you has to be very patient, and either broadcast, or listen, for a very long time. Or one of you has to be very noisy in the radio or optical spectrum or do mega-engineering in a big way.
Claes Wallin has just mentioned in the comments: there's research into the possibility that we could also spot intelligent extraterrestrial life if they are polluters of their planet e.g. create CFCs etc. A New Approach to SETI: Targeting Alien Polluters. Though it might be that only immature young ETIs like ourselves do that. More generally, if their industry or technology transforms their planet's atmosphere or surface in some obviously artificial way, that could be a clue for technology, and so indirectly, for intelligence (or something like intelligence). This again would be far easier for nearby planets. It's probably going to be some time before we can do spectrosopic observation of the atmosphere of Kepler 452b.
See also: Robert Walker's answer to How can NASA be assured of potentially favourable living conditions just by looking at Kepler 452B?
About the Author
Robert Walker
Writer of articles on Mars and Space issues - Software Developer of Tune Smithy, Bounce Metronome etc.Studied at Wolfson College, Oxford
Lives in Isle of Mull
4.8m answer views110.3k this month
Top Writer2017, 2016, and 2015
Published WriterHuffPost, Slate, and 4 moreHuffPost, Slate, Forbes, Newsweek, Business Insider, and Science 2.0