# Observable universe and events between vast distances

Hi Guys. I would like to ask what is the very nature of event in the same moment given a vast distances. Considering Point A (earth)-vast distance-Point B (galaxies). Would be possible that the event we're observing already happened long before it reaches us and may not exist at this very moment. Ex. If we saw a person flipping a coin in point B does it mean that what we saw is a delay of observation and the event that we saw in point B no longer exist at the very moment and time. Delay feed of event. Hope someone can shed a bit of light on this analogy. Cheers and Thanks.

Last edited:

If I understand the question correctly, yes, this is certainly true. When we look at distant a very distant galaxy, the light we're seeing actually left that galaxy billions of years ago, so we're really looking "into the past." This is why far redshifted galaxies (the most distant observable ones) are of particular interest to astronomers studying early galactic and stellar formation.

Of course, it works the other way around as well... if aliens in some galaxy a few hundred million light years away had some hypothetical 'telescopes' powerful enough to look at the happenings on earth's surface, they would see dinosaurs, not people.

Any time you look at anything, you're looking into the past. In everyday life, the delay is completely negligible, but on galactic scales it certainly isn't.

RE:
If I understand the question correctly, yes, this is certainly true. When we look at distant a very distant galaxy, the light we're seeing actually left that galaxy billions of years ago, so we're really looking "into the past." This is why far redshifted galaxies (the most distant observable ones) are of particular interest to astronomers studying early galactic and stellar formation.

If were observing the past. Does it mean that the event @ this very moment is in a different state than the once were observing? Considering a Point A time = Point B time in direct correlation with Point A event to point B event. So in consequence; Point B time doesn't apply to point B event. Sorry i'm a bit confused right now.

RE:Of course, it works the other way around as well... if aliens in some galaxy a few hundred million light years away had some hypothetical 'telescopes' powerful enough to look at the happenings on earth's surface, they would see dinosaurs, not people.

(Wild thought) In an instance where the alien hypothetically teleports to earth at that given moment same rate between earth and some galaxy. Would it be dinosaurs or humans? Sorry for the unconventional question. I really want to understand transitional events between time and distance so bare with me.

Any time you look at anything, you're looking into the past. In everyday life, the delay is completely negligible, but on galactic scales it certainly isn't.

Bandersnatch
1.Yes
2.Humans

Analogies incoming!

Imagine you're a maester in Game of Thrones' world. You're in King's Landing and you receive a raven bearing news of the Wildling attack on the wall*.
You know that it takes the raven three days to travel all that distance, so will you tell your king that the invasion happened NOW or three days ago? If you could magically teleport to the Wall, would the attack be just starting?
The ravens are like photons we observe coming from far away places in the universe. They bring us outdated information, in a sense. Still, since nothing can travel faster than light, the events that we see now might have as well just happened to us. So in another sense, it's the freshest news you can ever get.

*(if series is alien to you, substitute "steward in the capitol of a medieval country" and "a pigeon bearing news of an attack on a faraway border outpost")

Another analogy:

Say you're Capt.Picard orbiting close to the Sun in his Enterprise. Suddenly, the Sun begins to explode! With your trained reflexes you dash towards the teleporter in split of a second, saying a super-quick prayer for the souls of redshirts on board, and appear on Earth a moment later.

You've got less than eight minutes to tell people to say goodbye to their loved ones before their world ends. On the other hand, most people don't believe you, as the Sun looks completely fine from their vantage point.

So you say "whatever", comandeer another ship, and hyperspace-jump to another star system to escape the inevitable doom.
Alas, your destination looked like a normal star from Earth, but it turned out to be in early stages of supernova when you got there. So you end up dead anyway.

The moral of this story is that teleportation is not only impossible, but also dangerous.

Hope that helps a bit.

Bandersnatch;4158680]1.Yes
RE: 2.Humans
Analogy
Given -Point A (timeline hadean-proterozoic-phanerozoic-humans) earth
-Point B (timeline phase1-phase2-phase3-aliens) earthlike
-Distance of million lightyears
*In an event that point B (aliens) saw a Point A (hadean) through a hypothetical telescope. So in real time underlies a image of Point A (humans) that exist at the same moment regardless as what they saw as Point A (hadean)?

So most of our observations are layers of event from a different fraction of time as we go deeper.Ex. Layer 1-2-3-4-5-6-present. In our present state. Layer 1-2-3 might not exist(lack of better word) Or changed to a different state. So most of what were observing are projection of decays in space. Or i'm missing something crucial here. Help?

Analogies incoming!

Imagine you're a maester in Game of Thrones' world. You're in King's Landing and you receive a raven bearing news of the Wildling attack on the wall*.
You know that it takes the raven three days to travel all that distance, so will you tell your king that the invasion happened NOW or three days ago? If you could magically teleport to the Wall, would the attack be just starting?
The ravens are like photons we observe coming from far away places in the universe. They bring us outdated information, in a sense. Still, since nothing can travel faster than light, the events that we see now might have as well just happened to us. So in another sense, it's the freshest news you can ever get.

*(if series is alien to you, substitute "steward in the capitol of a medieval country" and "a pigeon bearing news of an attack on a faraway border outpost")

Another analogy:

Say you're Capt.Picard orbiting close to the Sun in his Enterprise. Suddenly, the Sun begins to explode! With your trained reflexes you dash towards the teleporter in split of a second, saying a super-quick prayer for the souls of redshirts on board, and appear on Earth a moment later.

You've got less than eight minutes to tell people to say goodbye to their loved ones before their world ends. On the other hand, most people don't believe you, as the Sun looks completely fine from their vantage point.

So you say "whatever", comandeer another ship, and hyperspace-jump to another star system to escape the inevitable doom.
Alas, your destination looked like a normal star from Earth, but it turned out to be in early stages of supernova when you got there. So you end up dead anyway.

The moral of this story is that teleportation is not only impossible, but also dangerous.

Hope that helps a bit.[/QUOTE]

Chronos
Gold Member
Another problem with instantaneous transport is nothing is actually where it appears to be. All galaxies [and all stars as well] have a random component of motion called called proper motion. A typical galaxy has a proper motion of about 200km/s, so an instantaneous line of sight transport to a distant galaxy could miss the galaxy entirely.

Bandersnatch
First of all, if I may ask you to double check your quotation tags before posting - there's a handy "preview post" feature next to "submit reply" that might help. As it is, your posts are very hard to read.

As for your questions, yes you do seem to have the right intuition there. We see other places in the universe as they'd been long time ago, and the hypothetical aliens see the Earth as it had been long time ago as well.

A good example might be the star Betelgeuse in the Orion constellation. While I'm not sure what's the current consensus on the matter, some time ago it was thought that the stars' fluctuation in size might be an indication of it entering the last stages of life before exploding as a supernova.
Since the star is roughly half a thousand light years away, it might've already exploded, but we wouldn't know, and in fact, couldn't know, before the information about the event(photons) reached us.

The thing is, in cosmology, you have to be very careful with what you mean when thinking about "events happening at the same time". Since in principle no event can influence another event before the interaction travelling at the speed of light(e.g.photons, gravity waves) arrives at its destination, does it even make sense to think of aliens 1000 light years away as living in our "now" moment, i.e. 1000 years in the future of the image we're receiving? It's kind of like trying to predict their future - interesting to think about, but ultimately meaningless. All we know is what we see, and what we see is their past. We can never see their "now".

Another problem with instantaneous transport is nothing is actually where it appears to be. All galaxies [and all stars as well] have a random component of motion called called proper motion. A typical galaxy has a proper motion of about 200km/s, so an instantaneous line of sight transport to a distant galaxy could miss the galaxy entirely.

Isn't proper motion usually given in arcsecs/year, or other appropriate angular units? What I mean to point out, is that proper motion only relates to the transverse velocity of the object in question; that is, the angular velocity along the surface of the celestial sphere. So even if we could miraculously predict what some distant object's proper motion has been since it emitted the light we are seeing, we would still need to account for its radial velocity if we wanted to estimate its "current" distance, and thus location.

Last edited:
Chronos
Gold Member
Yes, the peculiar motion of a galaxy may be aligned with our line of sight, perpendicular to it, or [most likely] at some angle in between.

Last edited:
First of all, if I may ask you to double check your quotation tags before posting - there's a handy "preview post" feature next to "submit reply" that might help. As it is, your posts are very hard to read.

As for your questions, yes you do seem to have the right intuition there. We see other places in the universe as they'd been long time ago, and the hypothetical aliens see the Earth as it had been long time ago as well.

RE: A good example might be the star Betelgeuse in the Orion constellation. While I'm not sure what's the current consensus on the matter, some time ago it was thought that the stars' fluctuation in size might be an indication of it entering the last stages of life before exploding as a supernova.
Since the star is roughly half a thousand light years away, it might've already exploded, but we wouldn't know, and in fact, couldn't know, before the information about the event(photons) reached us.

Thanks.

RE: The thing is, in cosmology, you have to be very careful with what you mean when thinking about "events happening at the same time". Since in principle no event can influence another event before the interaction travelling at the speed of light(e.g.photons, gravity waves) arrives at its destination, does it even make sense to think of aliens 1000 light years away as living in our "now" moment, i.e. 1000 years in the future of the image we're receiving? It's kind of like trying to predict their future -

-Apologies on OT.

I agree. Sometimes I get the thinking that i'm missing something fundamental about time, space and distances. So i refer to analogies, thought experiment and play a little to understand more on how does it function and its limitation besides the obvious reason of "seeing into the past Or time moves forward that past and future may or may not exist at the same rate and "now" is just an illusion". It's like we're observing the past but underneath is the future which hypothetically exist at the same instance with the observer upon layers of event stack at the same rate. I know going any further than this makes no sense at all. And thanks for the insight. Now back to reality. Got to read more on flat ΛCDM Big Bang model.^^