Limitations of Observing Distant Space Objects

[laith salim]

Physicists suggesting that observing space objects will be in a time that passed the time you are doing the observation if that object is far enough to exceed the distance the light photons can travel in respect to time (300,000 km/sec), anybody can refer me to equation, study or science that support that? How the physicists concluded that our observation is limited to that distance. In other words, how the speed of light photons dectate our observation limits.

 

[PeroK]

Your question appears to be: why are light signals not instantaneous? The speed of light is finite and was first measured in 1676 by Ole Roemer. See, for example:

https://www.amnh.org/learn-teach/cu...osmic-horizons-book/ole-roemer-speed-of-light

 

[phinds]

How the physicists concluded that our observation is limited to that distance

I'm not sure what "distance" you are referring to. ALL of the observable universe is, by definition, observable even though objects that the far reaches of it are receding (NOT "moving" in the sense of proper motion) away from us at about three times the speed of light. The farthest-away light is the Cosmic Microwave Background and the objects that we see now are currently about 47 billion light years away from us but the light was emitted about 13+ billion years ago (the age of the universe minus about 400,000 years). The greater distance is due to the expansion of the universe.

If, on the other hand, you are asking why we see what we see, the only answer is "because that's the way nature made it". We develop theories to EXPLAIN what we see, but nature doesn't care how we describe things, it just does what it does.

 

[PeterDonis]

ALL of the observable universe is, by definition, observable even though objects that the far reaches of it are receding (NOT "moving" in the sense of proper motion) away from us at about three times the speed of light.

More precisely, objects near the edge of our observable universe are receding from us now at about three times the speed of light. But that does not mean they were receding from us at that speed when they emitted the light we are seeing now.

 

[laith salim]

I'm not sure what "distance" you are referring to. ALL of the observable universe is, by definition, observable even though objects that the far reaches of it are receding (NOT "moving" in the sense of proper motion) away from us at about three times the speed of light. The farthest-away light is the Cosmic Microwave Background and the objects that we see now are currently about 47 billion light years away from us but the light was emitted about 13+ billion years ago (the age of the universe minus about 400,000 years). The greater distance is due to the expansion of the universe.

If, on the other hand, you are asking why we see what we see, the only answer is "because that's the way nature made it". We develop theories to EXPLAIN what we see, but nature doesn't care how we describe things, it just does what it does.

When you look and see the 47 billion light year distant object (Star) do you see light photons coming from that object or or you see a burning flamed object (star)? Because there is a differnce between the two that physicists seems to ignore.

 

[PeterDonis]

When you look and see the 47 billion light year distant object (Star) do you see light photons coming from that object or or you see a burning flamed object (star)?

Both. Light photons from the object reach our eyes or detection instruments and form an image of the star as it was when the light was emitted.

Because there is a differnce between the two that physicists seems to ignore.

I'm not sure what you are talking about here.

 

[Ibix]

How the physicists concluded that our observation is limited to that distance. In other words, how the speed of light photons dectate our observation limits.

Do you mean, how did we conclude that nothing can travel faster than light? It's a postulate that Einstein made. The implications of that postulate are testable, and so far we've never seen any evidence it's wrong.

 

[laith salim]

Both. Light photons from the object reach our eyes or detection instruments and form an image of the star as it was when the light was emitted.I'm not sure what you are talking about here.

Flamed object is not a light wave, flamed burning object produce light photons which in turns these photons produce light that brightens the sphere around the burning flamed objects.

 

[Ibix]

Flamed object is not a light wave, flamed burning object produce light photons which in turns these photons produce light that brightens the sphere around the burning flamed objects.

So, you mean you think we should say "we watch light from the TV" and not "we watch TV"? It seems a little unnecessary.

 

[laith salim]

So, you mean you think we should say "we watch light from the TV" and not "we watch TV"? It seems a little unnecessary.

Again, in your example, the TV is the star that produce the light photons that brightens the surrounding field, the two ( TV screen & light photons) are different entities and have different properties.

 

[PeterDonis]

Flamed object is not a light wave

Yes, this is obvious. But you claimed that physicists are ignoring this fact. What is your basis for this claim?

the TV is the star that produce the light photons that brightens the surrounding field, the two ( TV screen & light photons) are different entities and have different properties.

Yes, everybody knows this. But "brightens the surrounding field" is itself ignoring the thing we are actually interested in, which is the image that is produced when we receive the light from the TV or the star. That image tells us about the source--the TV (which means the program we are watching) or the star--not the "surrounding field".

Again, what is your basis for the claim that physicists are ignoring these obvious points?

 

[PeterDonis]

Moderator's note: Thread level changed to "I".

 

[laith salim]

Do you mean, how did we conclude that nothing can travel faster than light? It's a postulate that Einstein made. The implications of that postulate are testable, and so far we've never seen any evidence it's wrong.

No, my question is about observation and distance, not a speed of light calculation.
Searching for any equation suport observation distance limit in the moment of now in time before it becomes past.

 

[PeterDonis]

my question is about observation and distance, not a speed of light calculation

You're quibbling. The two are directly related.

any equation suport observation distance limit in the moment of now in time before it becomes past

I don't know what you mean by this. If you want to observe something as it is "now" it has to be right next to you, i.e., at a distance of zero. (Even that is not strictly possible. Something right "next to you" is still, say, 1 foot away, which means you aren't observing it as it is "now", you are observing it as it was about 1 nanosecond ago.)

 

[laith salim]

Yes, this is obvious. But you claimed that physicists are ignoring this fact. What is your basis for this claim?Yes, everybody knows this. But "brightens the surrounding field" is itself ignoring the thing we are actually interested in, which is the image that is produced when we receive the light from the TV or the star. That image tells us about the source--the TV (which means the program we are watching) or the star--not the "surrounding field".

Again, what is your basis for the claim that physicists are ignoring these obvious points?

The Physicists observing distant flamed objects and trated it as light photons and use speed of light as bassis to estimate time elapsed for light photons traveled from the flamed object.
Again we are looking at flamed object in universe, not a light photons.

 

[laith salim]

related

Please, educate me and show me how it is related? This is my post question.

 

[PeterDonis]

The Physicists observing distant flamed objects and trated it as light photons and use speed of light as bassis to estimate time elapsed for light photons traveled from the flamed object.

I don't see how this means they are ignoring anything you said they are ignoring.

Again we are looking at flamed object in universe, not a light photons.

We have already gone over this. We are detecting light photons that come from the object. Physicists recognize that. If you don't, then it seems that it is you who are ignoring relevant facts.

 

[PeterDonis]

Please, educate me and show me how it is related? This is my post question.

Light from objects takes longer to reach us if the objects are farther away from us when they emit the light.

In our universe, there is also expansion to take into account. That affects the precise relationship between distance and light travel time, but does not change the basic principle given above.

 

[russ_watters]

t=d/s?

 

[phinds]

When you look and see the 47 billion light year distant object (Star) do you see light photons coming from that object or or you see a burning flamed object (star)? Because there is a differnce between the two that physicists seems to ignore.

First of all, there ARE no stars at the distance of the CMB. None had formed yet.

Second, physicists do NOT ignore pertinent facts and observations so I suggest that you are misunderstanding something.

Third, EVERYTHING we see with our eyes, is photons impinging on our inner eye and they are all created by EM waves in the visible part of the spectrum. We "see" lots of things using detectors other than our eyes.

Fourth, the CMB is not visible to the naked eye and it only observable by microwave detectors. The clue to that is in the name CMB => "Cosmic MICROWAVE background". Microwaves ARE photons when detected but microwaves do not create photons in our eyes, only in microwave detectors.

 

[Dale]

Searching for any equation suport observation distance limit in the moment of now in time before it becomes past.

I know every one of those words, but I have no idea what you are asking. Especially the phrase “in the moment of now in time before it becomes past” is unintelligible.

 

[phinds]

I know every one of those words, but I have no idea what you are asking. Especially the phrase “in the moment of now in time before it becomes past” is unintelligible.

 

[laith salim]

The Physicists observing distant flamed objects and trated it as light photons and use speed of light as bassis to estimate time elapsed for light photons traveled from the flamed object.
Again we are looking at flamed object in universe, not a light photons.

Light from objects takes longer to reach us if the objects are farther away from us when they emit the light.

In our universe, there is also expansion to take into account. That affects the precise relationship between distance and light travel time, but does not change the basic principle given above.

Let me explain my question from a diffrent view and forget the stars, If you are looking at distant planet with no light at its surface, what is the equation, law or theory that the scientists use to conform their claim that I'm looking at that planet as it was minutes ago, 1000 years ago or bilions of years.
If you know one let me where I can find it and we will have more talk.

 

[PeterDonis]

If you are looking at distant planet with no light at its surface, what is the equation, law or theory that the scientists use to conform their claim that I'm looking at that planet as it was minutes ago, 1000 years ago or bilions of years.

It's not an equation, law, or theory. It's the experimental fact that light has a finite speed.

 

[laith salim]

How you

It's not an equation, law, or theory. It's the experimental fact that light has a finite speed.

Experimental fact, thank you for the correction.
How the finite speed of light used to make the scynteist

 

[laith salim]

...the scientists sure of their claim.

 

[Drakkith]

Let me explain my question from a diffrent view and forget the stars, If you are looking at distant planet with no light at its surface, what is the equation, law or theory that the scientists use to conform their claim that I'm looking at that planet as it was minutes ago, 1000 years ago or bilions of years.

The fact that light has a finite speed means that every object you look at, including your computer monitor's screen, is showing you how it looked in the past. The further away that object, the further back in the past you are seeing something.

 

[hutchphd]

The first demonstration was Ole Roemer's 1676AD observance of the eclipses of Jupiter's moons and how the observation time of these clocklike occurances depended upon the distance between the earth and Jupiter. Since then we have made countless measurements including bouncing green laser light light from reflectors placed on the luner surface by Apollo astronauts. All of GPS relies upon knowing exact photonic travel times. The examples are approximately endless.

 

[Drakkith]

This is simple logic. If it takes 5 seconds for light to reach you from me, then when I wave to you, you will not see me wave until 5 seconds has passed.

Similarly, let's say that you and I are standing far apart and you see me raise my hands and clap my hands together. There will be a delay between you seeing my hands clap together and you hearing the sound. Let's say that delay is 1 second You can only hear the clap 1 second after you see it. The same thing happens with light as with the sound, except that we don't have a faster means of transferring information than light.

 

[Dale]

what is the equation, law or theory that the scientists use to conform their claim that I'm looking at that planet as it was minutes ago, 1000 years ago or bilions of years.

The general equation that works for all coordinate systems in all spacetimes is $$\mathcal{L}=\frac{1}{2}g_{\mu\nu}\frac{dx^\mu}{d\lambda}\frac{dx^\nu}{d\lambda}$$
Use the usual Lagrangian techniques to solve that using any affine parameter. Then choose constants of motion to make the Lagrangian null, and you have the specific equation for any situation

 

[jedishrfu]

I think we need to step back a little and explain how we know how far away some astronomical object is.

There are several schemes that have been used that are described in this NASA article:

https://starchild.gsfc.nasa.gov/docs/StarChild/questions/question39.html

1) radar -- for planets and asteroids
2) parallax -- for nearby stars
3) cepheid variable stars -- for distances within our galaxy to star clusters and to nearby galaxies
4) supernovas -- for near by galaxies
5) redshift and the Hubble's law -- for the most distant objects



The methods overlap each other and so its possible to use radar to measure the distance to a planet and then verify that parallax works well. Next we can use parallax to a nearby cepheid variable star to calibrate the cepheid yardstick... We build a set of ladders to farther and farther distances.

You mentioned whether we can see the distant star close up like we see our sun. No we cannot as we don't get enough light to construct a detailed image of the star like we can with the sun. For the most part, stars are treated as point sources of light where we can do spectral analysis to get a composition of elements but no image.

Think about how much dust the light has traveled through and how that in itself would make any image fuzzy.

 

[phyzguy]

The Physicists observing distant flamed objects and trated it as light photons and use speed of light as bassis to estimate time elapsed for light photons traveled from the flamed object.
Again we are looking at flamed object in universe, not a light photons.

I think you are confused by what it means to see something. Everything we see we see because photons from the object travel through space and enter our eyes. When you see "we are looking at flamed object", what you mean is that photons from the flamed object are traveling into our eyes and our eyes are making an image of the flamed object.

 

[vanhees71]

Here's a very clear paper about the correct conceptions of horizons and all that in the FLRW-metric based standard cosmology:

https://arxiv.org/abs/astro-ph/0310808
https://doi.org/10.1071/AS03040

 

[PeterDonis]

Experimental fact, thank you for the correction.
How the finite speed of light used to make the scynteist

...the scientists sure of their claim.

Obviously if light travels at a finite speed, it takes time for light to travel from the object that emits it to you receiving it. The light shows you the object as it was when the light was emitted, which will be a finite time earlier than the time you see it. I don't see what the problem is.

 

[laith salim]

View attachment 334018

You don't have to comment if you don't have a convincing answer or you did not understand the question as a respect for everybody, thanks

Obviously if light travels at a finite speed, it takes time for light to travel from the object that emits it to you receiving it. The light shows you the object as it was when the light was emitted, which will be a finite time earlier than the time you see it. I don't see what the problem is.

When we look at burning tree, we don't say we looking at light, we say we are looking at fire, flames or burning object because that we are observing. Burning object is a burning object and not a light.
Time, speed and distance are related, in order to calculate a true value of any of them, it is required that all of the three to have a true value, in order to have a true measure of time then you have to do the real distance, by using telescopes to observe a star, you are standing still and zooming in an instrument to magnify an distant object, there is no real distance traveled to have a true value of time. What actualy the telescope measuring is the estimate time reqired to travel that distane. there is no solid evidence that light photons will take that long journey through the dark matter and reach your eyes billions earth years later, there is no solid convincing link between observation and time that I'm aware of.