# If aliens are looking at Earth with a telescope light years away...



## Aladdin Sane (May 10, 2016)

[obviously a very powerful telescope lol]

....they are seeing the past, they are seeing light that has reached them, so basically, if they were looking at Earth through a telescope, they could see JFK getting shot or something.

I mean that is what science says, that things we see from light years away are from the past. 

So basically the universe recods everything like a video cassette or a collection of photos? And if the universe is infinite, then there will always be a place in the universe where the light finally reaches and something new becomes visible there, and so things that have happened are forever observable with your own eyes, someplace in the universe? 


:shocked:


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## HAL (May 10, 2014)

Nope. Light is energy, which is simply a slightly more intense form of heat. Everything cools own eventually.

Also there are things like redshift, blueshift, and the fact that the rate of expansion of the universe means there's a border that we can never see beyond, because our relative velocities exceed lightspeed (or something like that - I can't quite remember how it works).

Kind of a bit a like this:


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## ae1905 (Jun 7, 2014)

are you bored of tv and youtube, already?


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## FearAndTrembling (Jun 5, 2013)

That's actually an interesting thought. That from some point of view in the universe every event is always happening somewhere. Like a wave that keeps moving.


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## yet another intj (Feb 10, 2013)

Aladdin Sane said:


> So basically the universe recods everything like a video cassette or a collection of photos?


No... Unfortunately, the magnification factor of their telescope is irrelevant. Space is not a perfect vacuum. When you are looking at darkness, you are practically staring at interstellar medium. Which contains random chunks of molecules, energetic particles, force fields, etc. So, there will be many problems such as absorption, reflection, refraction, etc in micro scale and their cumulative effect will be horrendous. There will be also problems caused by movement(s) such as relativistic doppler and rolling shutter effects. Because everything is moving towards whatever relative direction. Including our galaxy, which is not spherical yet constantly spinning. By the way, I'm not even talking about path loss and gravitational lensing. They can't see shit unless they have a magical DSP technology to measure/calculate and correct all those things. In other words, it's nothing we can even assume with our current level of technology and understanding.



Aladdin Sane said:


> And if the universe is infinite, then there will always be a place in the universe where the light finally reaches and something new becomes visible there, and so things that have happened are forever observable with your own eyes, someplace in the universe?


"The visual representation of Earth" and "randomly scattered photons originated from Earth" are different things. A single photon doesn't mean anything just because it was somewhat coming from an object. Actually, even a remarkable amount of photons alone can't be interpreted to make sense by any means. Same for old radio signals leaked into/aimed at deep space. Carrying information with electromagnetic waves is quite inefficient between "that long" distances.

I think you may find this a little more interesting: Superluminal Communication


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## Simpson17866 (Dec 3, 2014)

HAL said:


> because our relative velocities exceed lightspeed (or something like that - I can't quite remember how it works).


 That's exactly how it works :wink:

Nothing can move _through_ space at more than the speed of light, but space itself is not bound by the speed limit. If the distance between two objects doubles between time t=0 and time t=x, then the distance will double again from t=x to t=2x.

If two positions are 1 million parsecs apart (3.26 million light years), then the amount of space between those positions is increasing at about 67 kilometers/second. The speed of light is about 299,792 km/s, so two positions would have to start 4,500 million parsecs (15 billion light-years) apart in order for the space between them to be expanding at faster than the speed of light.


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## Aladdin Sane (May 10, 2016)

yet another intj said:


> Nope... Unfortunately, the magnification factor of their telescope is irrelevant. Space is not a perfect vacuum. When you are looking at darkness, you are practically staring at interstellar medium. Which contains shit load of molecules. So, there will be many problems such as absorption, reflection, refraction. There are also distance and movement related problems such as relativistic doppler and rolling shutter effect because everything (including our galaxy, which is not spherical yet constantly spinning) and eventually path loss. By the way, I'm not even talking about gravitational lensing. They can't see shit unless they have a magical digital signal processing technology to calculate and correct all those things. In other words, it's nothing we can even assume with our current level of technology and understanding.
> 
> 
> "The visual representation of Earth" and "randomly scattered photons originated from Earth" are different things. A single photon doesn't mean anything just because it was somewhat coming from an object. Actually, even a remarkable amount of photons alone can't be interpreted to make sense by any means. Same for old radio signals leaked into/aimed at deep space. Carrying information with electromagnetic waves is quite inefficient between "that long" distances.
> ...


I don't understand any of that and I was not really looking to get that deep. But if we see the things as they were in the past when we look at galaxies light years away, are you saying that from the other side, it doesn't work the same way?


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## FearAndTrembling (Jun 5, 2013)

Aladdin Sane said:


> I don't understand any of that and I was not really looking to get that deep. But if we see the things as they were in the past when we look at galaxies light years away, are you saying that from the other side, it doesn't work the same way?


He is pointing out the real world difficulties. I certainly agree it is way beyond our current means. I am just thinking it as a thought experiment. You would need to have like a God's eye view of the universe. But it is technically true that the universe records itself in a sense. I like that analogy. John Wheeler was really good. And used more like a ghost analogy. 

About 20 years ago I ran into John Wheeler at a Baltimore hotel. "Tell me," he asked, "how do you hold up half the ghost of a photon?" His question was a typically Wheelerish: intriguing, enigmatic, pithy, and provocative. I soon discovered it referred to an outlandish thought-experiment designed to probe the conceptual foundations of quantum mechanics.


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## Aladdin Sane (May 10, 2016)

FearAndTrembling said:


> He is pointing out the real world difficulties. I certainly agree it is way beyond our current means.


... what is beyond our current means? We know that we see the past when we look at far away objects, not their current state. So we know that if someone was looking at Earth from far away in space, they would see it in its past form.


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## yet another intj (Feb 10, 2013)

Aladdin Sane said:


> I don't understand any of that and I was not really looking to get that deep.


That's why your assumption was wrong. You were talking about looking to get that deep into space without "really looking to get that deep".



Aladdin Sane said:


> But if we see the things as they were in the past when we look at galaxies light years away, are you saying that from the other side, it doesn't work the same way?


"Detecting a distant galaxy (100,000 light years in diameter)" and "focusing on a planet until you recognize JFK and watch his last minutes once again" are "very" different. The bundle of photons to represent "whatever ridiculously tiny detail" will be already fucked up/meaningless because it will be heavily affected by matter and energy on it's way while traveling that distance. That's why they can't see everything as you did, even if they have virtually infinite magnification factor. They can notice our galaxy and observe it's "general features as a whole" but even that observation will be extremely flawed. I mean even in that insanely huge/forgiving scale. By the way, what our current astronomers are serving as "whatever high detail visual from past" is mostly a soup of X-ray/visible/infrared spectrum originated from billions of blinding suns and many other extremely prominent objects. Needless to say, those visuals are "somewhat interesting" because they are heavily processed/adjusted to make sense to our human eyes. The thing is, they can't even represent "what a galaxy looks like" and talking about "a human being who lived in somewhere inside of that mess" is beyond logic. Actually, there's no way to simply interpret "how a galaxy looks like" according to our intuitive/practical visual concepts. It's that big, fast and bright, you will still observe how it was looking 50,000 years ago when you look around even if you are standing in the center of it anyway.


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## WorldzMine (Sep 9, 2014)

The reason that one see's the past as they look out at the universe is because the speed of light is finite, not because the universe is somehow recoding information from light. The universe's event horizon that you can actually observe is literally expanding at the speed of light.


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## Donovan (Nov 3, 2009)

the idea is interesting in the way that a lot of what we see in the night sky, may actually be from a star that is in fact long dead by the time its light reaches earth... but i don't know if all light necessarily "escapes" earth. especially when on the level that it illuminates human-to-human interaction. 
and in the end, wouldn't we just we witnessing light--even if it did escape--and not what the light was illuminating in and of itself, nor what it was emitted from?


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## Sylarz (Sep 4, 2014)

Aladdin Sane said:


> [obviously a very powerful telescope lol]
> 
> ....they are seeing the past, they are seeing light that has reached them, so basically, if they were looking at Earth through a telescope, they could see JFK getting shot or something.
> 
> ...


It is light that shows you what it looked like when the light left. So when we observe the universe, we are looking at how it was. But the light that has left earth is forever lost. It's useless because you can't catch up to the light and have a look. So you can hardly call it a recording, if you can never see it. It's only viewable _once_ for aliens who are light years away, just like everything else.


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## Sylarz (Sep 4, 2014)

HAL said:


> Nope. Light is energy, which is simply a slightly more intense form of heat. Everything cools own eventually.
> 
> Also there are things like redshift, blueshift, and the fact that the rate of expansion of the universe means there's a border that we can never see beyond, because our relative velocities exceed lightspeed (or something like that - I can't quite remember how it works).
> 
> Kind of a bit a like this:


Well I don't mean to contradict you, but I think this is slightly inaccurate 

Light is electro-magnetic radiation [5], not energy, it _has_ energy. Its energy is calculated by plank's equation: E = hf. [3] This equation shows that the energy light contains is dependent only on its frequency, which is very strange, because it is unlike other waves, where amplitude matters. But energy does not equal electro-magnetic radiation. 

Energy is the capacity to do work. It is a property, not a thing. "*Energy* is measured in joules, and one joule is defined "mechanically", being the energy transferred to an object by the mechanical work of moving it a distance of 1 metre against a force of 1 newton." [4] As you can see, it's about moving stuff. 

*Heat*, scientifically, is "the exchange of thermal energy between physical systems." [1] It is not _equal_ to radiation, nor is heat a type of radiation. Radiation is a way that heat can be transferred. I think this is an important point. Heat* can be released *as electro-magnetic radiation, but it doesn't have to. There are other ways. "The three fundamental modes of heat transfer are conduction, convection and radiation."[2] So radiation is merely one of them. For example, conduction is where ajacent more energetic atoms knock into atoms around them, transfering internal kinetic energy in this way. There is no electro-magnetic radiation involved. 

However, it is confusing perhaps a little bit, because we all know that any body of a non-zero temperature will eventually cool off, without conduction or convection, because EM radiation is emitted _whenever_ charged particles are accelerated[5], and since the particles of the body are moving (it's non-zero temperature), heat is always given off by every non-zero temperature body in the universe in the form of electro-magnetic radiation. And since there's no 0K things in the universe, everything is essentially giving off heat as electro-magnetic radiation. A cool way to think about it is that everything in the universe is glowing. I can see how that could be confusing.

I believe these are common misconceptions and equivocations. I see a lot of these sorts of equivocations thrown around. It's easy to become confused, especially when you hear people around you saying these things, so I understand.  

References:
[1] https://en.wikipedia.org/wiki/Heat 
[2] https://en.wikipedia.org/wiki/Heat_transfer
[3] https://en.wikipedia.org/wiki/Planck–Einstein_relation
[4] https://en.wikipedia.org/wiki/Energy
[5] https://en.wikipedia.org/wiki/Electromagnetic_radiation


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## HAL (May 10, 2014)

Setrleua said:


> Well I don't mean to contradict you, but I think this is slightly inaccurate
> 
> Light is electro-magnetic radiation [5], not energy,


Hmm I know what you're trying to say, and you're right about my incorrect terminology (I should have said light is just the more intense cousin of _infrared radiation_ - not "heat" - though I doubt I'm the first to make that mix-up!) but I'm very sure light is definitely pure energy. It's massless and can travel through a vacuum at the speed of light. This immediately removes it from the physical realm you and I are accustomed to.

I realise how poorly I worded that whole previous post though. It's quite embarrassing actually, heh. I'm a 3rd year physics student. So it was real case of me knowing what I'm on about but the words managing to just come out as vomit across my keyboard.


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## Sylarz (Sep 4, 2014)

HAL said:


> Hmm I know what you're trying to say, and you're right about my incorrect terminology (I should have said light is just the more intense cousin of _infrared radiation_ - not "heat" - though I doubt I'm the first to make that mix-up!) but I'm very sure light is definitely pure energy. It's massless and can travel through a vacuum at the speed of light. This immediately removes it from the physical realm you and I are accustomed to.
> 
> I realise how poorly I worded that whole previous post though. It's quite embarrassing actually, heh. I'm a 3rd year physics student. So it was real case of me knowing what I'm on about but the words managing to just come out as vomit across my keyboard.


I don't know where you learned that but I don't think that light is pure energy. Energy is not a thing, but a property of things. Light is a thing. Having mass does not equal physical. There are massless particles, which are very much physical. Mass is a property of some types of matter.


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## HAL (May 10, 2014)

Setrleua said:


> I don't know where you learned that but I don't think that light is pure energy. Energy is not a thing, but a property of things. Light is a thing. Having mass does not equal physical. There are massless particles, which are very much physical. Mass is a property of some types of matter.


All I'm seeing here is a clear case of semantic whataboutery because energy is present in everything ever. Energy is in mass, heat, everything. I'm not sure what point you're trying to make other than to redefine the definition I was using.

As far as I'm concerned, 'energy' is like the aether that was used to describe the medium light travelled through. It's an abstract thing to fit the space so people can feel like they better understand what's going on. There's still something going on, and in my opinion EM waves are energy in its purest form. They're the only known thing that can transfer the entire of themselves across a vacuum with unlimited distance until they strike something and transfer the entire of themselves into the object they hit. Seems like a pretty damn good contender for pure energy to me.

There are three massless particles and they all act as a gauge for energy transfer during particle interactions. Again this seems like a pretty obvious hint they they are all pure energy. Without photons, gluons and possibly gravitons, certain interactions would simply not occur, and the thing defining these interactions is a change of energy (and a few other things but the bottom line is it wouldn't happen if there was a stable energy equilibrium).

It's a fairly nitty-gritty subject with various lines of attack but personally I think the universe is nothing other than an incredibly complex set of interacting waves. Pair production sets this in motion pretty well - making something out of nothing other than a propagating disturbance in a self-contained EM field. Then we have all of quantum mechanics which goes off the basis that everything is a wave aka a propagating disturbance in some medium, and that disturbance can be nothing other than energy itself.

Just my thoughts. I do know what you're saying, but I just don't like the wishy-washy nature wherein people say energy goes from here to there and from one form to another. It's obviously all one and the same, and something is causing it to go from place to place. The most logical answer is wave propagation and that's what light and gauge bosons are. 

Feynman diagrams show it pretty well too. The curly lines are where the energy transfer takes place. Those are your massless particles.

I'm sure particle physicists would lynch me for all I've said here but meh, it just seems bloody obvious that waves are at the core of everything and waves are just a propagation of energy.

Alright, mini rant over.


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## DaveJohnson (May 29, 2018)

I don't believe in a video recording the universe lol


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## Cosmic Chaos (Jun 8, 2018)

That's a super interesting thing Ive always pondered on since learning that light and therefore seeing things takes time. Like everytime I think of a intergalactic society I then think how would the light distance between everything affect how they communicate and see each other like hell I could see in SW Luke hyperspace warping from Tattooe say about 40-50 light years away in the events of ANH and seeing his own father on the same planet as Anakin or hell even Darth Vader could see his past self its mind bending lol.


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## The red spirit (Sep 29, 2015)

In physics I knew that we see rising sun 8 minutes later than it actually happens and as distance increases light travels longer, creating even weirder light distortions. But looking at objects itself I don't know. We should see the actual stuff happening, because humans aren't light and then aliens would be directly looking at stuff happening right now. 

Einstein thought that time traveling could exist if person somehow could spin very fast against Earth rotations. But that would be way too fast. So if aliens wanted to see JFK, then they probably have to be in a place that constantly spins very fast and in counter-Earth direction, but this is speculation only. For me it doesn't make any sense. Just like traveling against time zone to get pack into past. But plane pilots already traveled into past, just very tiny amount. It's pats of seconds and really it's meaningless.

Another way to travel to the past is to find negative matter. Stuff that is in all ways negative to what we have. Theoretically it be negative and may distort time. If I remember correctly black holes distort time, sounds and are key element in time traveling. Maybe someone lives in black hole.

Another theory is that we are first civilization in whole space that is intelligent enough to actually comprehend space concept. So we can be first to actually think about stuff like that. But isn't it entertaining?

Another theory is that our understanding of life forms is probably not entirely without holes or just is unclear. We already know that viruses are life forms and they live, but they don't have cells and in many ways are very different from other life forms on Earth. They could probably be even considered as dead of their existence time, but they aren't. Imagine aliens in far far away. What if their life forms are invisible to us. We can't hear, see them existing at all. Those would remain undiscovered until we make equipment to extend human senses, at least. Or maybe there's something very far, but their level is very low. Imagine planet, where only few amoebas are living. That would be technically a life form, but probably really big let down to us, who imagine aliens as seemingly intelligent species. I start to think that there aren't any aliens, it's just our imagination working, due to desire to know more about the space we live in and what's is beyond it. Or maybe it's mixed with our self-safety instincts to feel safer in space. Humans grew to be more intelligent, so safety feeling requirements grew too, I guess. Just like living standards and other stuff. Evolution may not be about survival anymore, but about living requirements getting higher. No one would want to live like in middle ages and be into today's society. They would just go extinct. So we get interested in weirder and weirder stuff and keep making society that makes more sense. Science was probably not respected in 1500s much, but now we take it as granted. Just like people don't work until they die. We have some life too. Our definition of living has truly expanded and I think it will expand even further. That's just the way stuff keeps moving.

And yet another theory is that aliens may be very different in their thinking and seeing organs and they built not telescope but something like ray recorder and could see Earth in the past and probably in the present time. Weird machinery, but hey if it works, it works. Or maybe they decided to spin those rays and make them get back into past that way.

I'm not a scientist. I really don't know physics all that well, but I think I have imagination and some theories. What I know is that time traveling or seeing past is impossible and nobody really knows how it would really work out. We need more research and experimentation to really know that. We don't even know a lot about various wave surrounding our Earth, neither we know much about depths of oceans. I would just say, wait and enjoy. Currently you can live and believe various theories and enjoy all those "colors" of imagination. It looks like dudes and girls got seriously "scientific" in this stuff, but I see very low chances into them getting to the real truth of subject like this.

Anyway your question looks really interesting. Thanks for asking.


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