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Question that bothers me for a really long time....


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Posted (edited)

Good day,

So i got a quick question and maybe someone can help me to understand it.

Light travels from Sun to Earth in about 8 minutes. So we can see Sun how it was 8 mins ago... (aprox).

So here is the question:

Moon does not illuminate by itself as we know. So if im sitting on the Sun and looking at the Moon, should i see it how it was 16 mins ago?.. 

Thank you.

Regards

Edited by Geekyrussian
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Posted (edited)
1 hour ago, Geekyrussian said:

Good day,

So i got a quick question and maybe someone can help me to understand it.

Light travels from Sun to Earth in about 8 minutes. So we can see Sun how it was 8 mins ago... (aprox).

So here is the question:

Moon does not illuminate by itself as we know. So if im sitting on the Sun and looking at the Moon, should i see it how it was 16 mins ago?.. 

Thank you.

Regards

Hi geekyrussian, I'm your friendly geeky Aussie.

Answering your question if you were sitting on the Sun, besides immediatly getting a hot arse, you would see the light from the Moon, reflected back to you 8 minutes later, [8.25 minutes to be exact], consequently seeing the Moon as it was 8.25 minutes ago. I understand what you sort of envisage, but I don't think it applies.

 if you were sitting on the Sun, and you had a huge screen in front of you stopping the light, so that the Moon was not visible, then removed the screen, you certainly would then see the Moon as it was 17 minutes earlier, at that instant, from the time you first removed the screen. I think!

Not 100% certain, but reasonably confident. Let's wait for another smarter geek to verify....

Edited by beecee
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Posted (edited)

Yep. I'd say it'll take 8 minutes for light to get from the Moon to you, so you'll see it where it was 8 minutes ago.

That light itself will have left the Sun 16 minutes ago - but it's when the Moon reflected it that matters here.

 

(

Consider going out on a moonless night (away from town) where everything is lit only by starlight.

That light took many thousands of years to get to Earth, but the objects seen (slightly) illuminated by it will not appear as they were thousands of years ago!

)

Edited by pzkpfw
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Posted (edited)
12 hours ago, pzkpfw said:

I'm rounding to the nearest banana.

 

Also, how is this relativity?

Great and thank you for the answers.

Now about where is the relativity in here:

So lets assume that Moon is on the same distance from the Sun im sitting on and also right next to that Moon is another Sun just like mine but a little smaller, also lets assume that between that smaller Sun and Moon is HUUUUGE wall... that us not allowing the smaller Sun light get to the moon...

Here is the question:

So is that means that i will see smaller Sun like it was 8 mins ago, but the Moon that next to it, how it was 16 mins ago?... Even though both of them are on the same distance from me...

And does that mean that i can see past and futue at the same time?

Thank you

Regards

14 hours ago, beecee said:

Hi geekyrussian, I'm your friendly geeky Aussie.

Answering your question if you were sitting on the Sun, besides immediatly getting a hot arse, you would see the light from the Moon, reflected back to you 8 minutes later, [8.25 minutes to be exact], consequently seeing the Moon as it was 8.25 minutes ago. I understand what you sort of envisage, but I don't think it applies.

 if you were sitting on the Sun, and you had a huge screen in front of you stopping the light, so that the Moon was not visible, then removed the screen, you certainly would then see the Moon as it was 17 minutes earlier, at that instant, from the time you first removed the screen. I think!

Not 100% certain, but reasonably confident. Let's wait for another smarter geek to verify....

Correct,

So 17 min apply to all the time that i am sitting on the Sun.... because there was a start point in time for that X hours, days, years etc., ago.

Thanks

Edited by Geekyrussian
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1 hour ago, Geekyrussian said:

So is that means that i will see smaller Sun like it was 8 mins ago, but the Moon that next to it, how it was 16 mins ago?... Even though both of them are on the same distance from me...

Everyone agreed you would see the moon as it was 8 minutes ago.  Why did you bring up 16 minutes?

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34 minutes ago, Bufofrog said:

Everyone agreed you would see the moon as it was 8 minutes ago.  Why did you bring up 16 minutes?

Light has to travel to the Moon for 8 mins and then reflect back for another 8 mins...

8 + 8 = 16

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Posted (edited)
51 minutes ago, Geekyrussian said:

Light has to travel to the Moon for 8 mins and then reflect back for another 8 mins...

8 + 8 = 16

Although it may take about 16 mins for sunlight to travel to the moon and then reflect back to your position on the sun, the actual reflected light from the moon will only show the moon as it appeared 8 mins ago.  Although the light from the sun to the moon and back to sun may require about 16 mins, the moon's reflection is only 8 mins old. Essentially, the light in that reflection is 16 mins old but the reflection itself is only 8 mins.

Just to add a bit more, the moon's visage is not in the 8 mins of light that travels from the sun.  Its visage is only in the 8 mins of light that is reflected back from the moon.

Edited by DrmDoc
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You will only see 16 minutes ago if there's a largish mirror on the moon and it catches the reflection of you (hopping around,  crying ouch ouch it's so hot) as you were when those photons began their journey out from the sun.   

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Posted (edited)
3 hours ago, Geekyrussian said:

Correct,

So 17 min apply to all the time that i am sitting on the Sun.... because there was a start point in time for that X hours, days, years etc., ago.

Thanks

I think you misunderstood...the 17 minutes time frame only applies as from the time you removed the screen, to when you first see the reflected light back in your eyes...as per what I said earlier "you certainly would then see the Moon as it was 17 minutes earlier, at that instant, from the time you first removed the screen". 

Otherwise  "the actual reflected light from the moon will only show the moon as it appeared 8 mins ago" as per DrmDoc

3 hours ago, Geekyrussian said:

And does that mean that i can see past and futue at the same time?

Every time we look into the night sky, we are looking into the past...I can just make out M31 [Andromeda] from where I am, as it was 2 million years ago. When I look at the C4entauri system tonight, I am seeing it as it was 4.5 years ago...theoretically it may not be there now, [my now that is] having gone nova.

16 hours ago, pzkpfw said:

Yep. I'd say it'll take 8 minutes for light to get from the Moon to you, so you'll see it where it was 8 minutes ago.

That light itself will have left the Sun 16 minutes ago - but it's when the Moon reflected it that matters here.

Bingo!

Edited by beecee
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Posted (edited)
1 hour ago, beecee said:

I think you misunderstood...the 17 minutes time frame only applies as from the time you removed the screen, to when you first see the reflected light back in your eyes...as per what I said earlier "you certainly would then see the Moon as it was 17 minutes earlier, at that instant, from the time you first removed the screen". 

Otherwise  "the actual reflected light from the moon will only show the moon as it appeared 8 mins ago" as per DrmDoc

Every time we look into the night sky, we are looking into the past...I can just make out M31 [Andromeda] from where I am, as it was 2 million years ago. When I look at the C4entauri system tonight, I am seeing it as it was 4.5 years ago...theoretically it may not be there now, [my now that is] having gone nova.

Bingo!

Yes i understand,

But reflection for 8 mins is only half of the problem. The 16 mins of delay are not going anywhere, as me sitting there and watching on the moon from that start point. As i understand that two objects on the equal distance from the point of my view (wich is the source of light #1) get 8 min difference in time, because the smaller Sun that is next to the Moon, its light travels towards me and reaches me in 8 mins, but the Moon (that is actually on the same distance from me as the smaller Sun) i will see with 16 min delay.

So 2 objects that are on the equal distance from me are actually in two different timeframes (for me). Cause in the start point i will see smaller Sun in 8 mins and the Moon in 16 mins (beacuse light needs to travel to the Moon, from my Sun, and back).

I am really sorry if its confusing, its really hard for me to explain myself on the language that is not my primary one.

 

Thank you

Regards

2 hours ago, DrmDoc said:

Although it may take about 16 mins for sunlight to travel to the moon and then reflect back to your position on the sun, the actual reflected light from the moon will only show the moon as it appeared 8 mins ago.  Although the light from the sun to the moon and back to sun may require about 16 mins, the moon's reflection is only 8 mins old. Essentially, the light in that reflection is 16 mins old but the reflection itself is only 8 mins.

Just to add a bit more, the moon's visage is not in the 8 mins of light that travels from the sun.  Its visage is only in the 8 mins of light that is reflected back from the moon.

Ohhhh,

Yes now i see... ok thanks for the answer

Edited by Geekyrussian
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Posted (edited)
3 hours ago, DrmDoc said:

Although it may take about 16 mins for sunlight to travel to the moon and then reflect back to your position on the sun, the actual reflected light from the moon will only show the moon as it appeared 8 mins ago.  Although the light from the sun to the moon and back to sun may require about 16 mins, the moon's reflection is only 8 mins old. Essentially, the light in that reflection is 16 mins old but the reflection itself is only 8 mins.

Just to add a bit more, the moon's visage is not in the 8 mins of light that travels from the sun.  Its visage is only in the 8 mins of light that is reflected back from the moon.

But i would have been correct if i would remove the wall between smaller Sun and a moon in about half way of the light traveling to me from a smaller Sun?

Meaning these 2 objects being on the same distance from me still be visiblr in 4 min difference?

 

Edited by Geekyrussian
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Posted (edited)
3 hours ago, Geekyrussian said:

But i would have been correct if i would remove the wall between smaller Sun and a moon in about half way of the light traveling to me from a smaller Sun?

Meaning these 2 objects being on the same distance from me still be visiblr in 4 min difference?

 

It's hard to parse that. But to repeat:

At time T when the Moon is at position X, any and all light hitting it that's reflected, will later hit your eyes at the same time. (Based on the speed of light and the distance between you and position X).

* All light reflected at time T will show position X.

* All light reflected from position X, came from time T.

It doesn't matter if that light originally came from any combination of our Sun, your new small Sun, lasers on Earth, or starlight from many light years away.

You will only see the Moon at one position at a time.

 

Your extra sun, your walls ... will not change that. The only thing you will affect is the brightness (and maybe colour) of the reflected light.  (Exactly when you see such effects depends on the positions and timing of the causes; and I can't follow your last post well enough to confirm one way or another.)

Edited by pzkpfw
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On 7/8/2021 at 4:21 PM, Geekyrussian said:

Y

 

So 2 objects that are on the equal distance from me are actually in two different timeframes (for me). Cause in the start point i will see smaller Sun in 8 mins and the Moon in 16 mins (beacuse light needs to travel to the Moon, from my Sun, and back).

I'm going to focus on this,  Others have already explained that you would see the both the Moon and smaller Sun as they were ~8 min prior to the moment you see them.

But, just because you "see" them that way, doesn't mean they are in a "different time-frame" from you.   So, for example, if the Moon has large clock face on it, and you, from your position, see it reading 11:52, while your clock reads 12:00, you can't conclude that is is 11.52 on the Moon when your clock reads 12:00.  The Moon clock ticked off 8 min in the time the light reflected off it left. So, When you see it read 11:52, it actually reads 12:00 just like your own clock.

The reason I bring this up is that you mentioned Relativity, and many people get confused about this.  They think time dilation etc, is all just related to what we visually see. This is not however the case.  In Relativity, we factor out any time difference caused by the time it took the light to travel the intervening distance, and are only concerned with what is left over after that. 

With your Moon example, we, for the sake of making it simple, assume that the Moon is not moving relative to you, and are ignoring any effects caused by gravity. In this case, there is no net time difference between you and the Moon ( even though the image you see of the Moon is ~8 min delayed)

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