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Thinking About the Journey of a Photon and Mars at Opposition

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#1 Fiz79

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Posted 30 September 2020 - 09:19 AM

Preamble: This is just me thinking out loud and hopefully starting an interesting discussion. I apologize if any of this is inaccurate. Please correct me if so. The numbers I'm using are approximations, of course. Just something I was thinking about last night when looking at Mars with my naked eye.

 

So, a lot of us are excited about Mars opposition coming up. Earth will be in between the Sun and Mars, and Mars will be very close to the Earth. At this point, it takes light around 4 minutes to reach us from Mars - half the time it takes for light to reach us directly from the Sun. But we know that the light from Mars did not originate from Mars. It was reflected off of Mars when sunlight reached the planet.

 

So in actuality when you think about it more deeply, the light that we are seeing from Mars is not 4 minutes old. It's around 16 minutes old. But the photons that hit our eyes appear as Mars because Mars is what reflected that light.

 

It's cool to think that while, to us, the light we see reflected off of Mars is very "close", in actuality, that light left the Sun, passed us on Earth (at a fair distance, of course), traveled to Mars, reflected off of Mars and eventually hit our eye.

 

So while the light reflected from Mars during opposition may only be traveling 62 million km to reach our eyes, the total distance that light actually travels before we can see it is around 274 million km. That's basically how far light takes to reach Earth-Sun distance plus twice the distance Earth will be from Mars (a round trip). 

 

It gets really interesting if you think about what would happen if the Sun just hypothetically...disappeared. If this happened, the photons that left the Sun right after the Sun vanished would take 8 minutes to get to us, so we wouldn't know that the Sun disappeared until 8 minutes later. At that point, the sky would be dark and we could look at Mars and still see it for quite some time afterwards, because the light that left the Sun right after it disappeared took considerably longer to reach Mars and reflect back to Earth, so we would then see Mars disappear as well some time later. Same goes for the other planets. One by one, they would fade away. The farther away they are from us, the longer it would take.

 

One other thing I was thinking about - when you look at Mars and someone else is standing (physically distanced, of course) next to you, the view of Mars may be the same, but your image of Mars is different than theirs because the photons of light that are entering your eye cannot be the same photons that are entering their eye. Your view of Mars is, technically, your very own. And those photons that left the Sun, reflected off Mars and came back to Earth only to arrive at your eyes are yours and yours alone. They started at the Sun and ended at you.

 

Light is fascinating.


Edited by Fiz79, 30 September 2020 - 09:22 AM.

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#2 Jim Davis

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Posted 30 September 2020 - 09:47 AM

Larry Niven wrote a short story named "Inconstant Moon". It is about someone surviving on the night side of the Earth when a large solar flare hit the day side. Part of it is noticing the Moon brighten, and later Jupiter due to the delay caused by the speed of light.



#3 sg6

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Posted 30 September 2020 - 09:58 AM

It gets really interesting if you think about what would happen if the Sun just hypothetically...disappeared. If this happened, the photons that left the Sun right after the Sun vanished would take 8 minutes to get to us, so we wouldn't know that the Sun disappeared until 8 minutes later. At that point, the sky would be dark and we could look at Mars and still see it for quite some time afterwards

That "quite some time" would seem to be 8 minutes. And I am sure iof the sun had disappeared out of shining existance 8 minutes before that then very few people would be hunting for a scope to look at Mars with.

 

One other thing I was thinking about - when you look at Mars and someone else is standing (physically distanced, of course) next to you, the view of Mars may be the same, but your image of Mars is different than theirs because the photons of light that are entering your eye cannot be the same photons that are entering their eye. Your view of Mars is, technically, your very own.

This I suspect depends if you consider the light as a partical or a wave. If partical then yes you appear to have 2 different "particals", if a wave then a portion of the same wave will in effect go down each eye.

 

We talk of liaght as a "photon" but the concept was around in a way first, and has stuck. If it is a wave then the ideas have to change also. And I suggest quite a bit. Consider every prediction of relativity has been correct, and relativity says there is no force of gravity. I think we are using to a large extent out of date terminology and it may be holding us back.


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#4 PirateMike

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Posted 30 September 2020 - 10:20 AM

The photons that hits us here on earth are considerably older than eight minutes. It is estimated that the photons that are released in the core of the sun may take up to 150,000 years of being absorbed and re-emitted within the sun before it even ever escapes.

 

Because time stops moving at the speed of light photons themselves are always zero time old.

 

I am a simple man by some standards but I have created a few theories as to the nature of the universe as a whole. Since absolutely nothing is know about the universe as a whole, my theories are as valid as the greatest minds that live today or have ever lived in the past. Kind of make me feel smarter than most tomato heads.

 

 

 

Miguel   8-)


Edited by PirateMike, 30 September 2020 - 12:01 PM.

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#5 Barlowbill

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Posted 30 September 2020 - 10:33 AM

While I am certainly cannot debate the intricate workings of light, I will propose that one photon is the same as another if developed by the same source.  It is the individual's eyes that may perceive a difference in the photon(s).  A light bulb in a household lamp will emit photons.  You and I may see those photons differently based on our individual eyes.  And each of our eyes may perceive those photons differently.  Ok, I'm done thinking for the day.  Dang, that was exhausting.

I like the subject.  Cool to think about.  Thanks


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#6 Fiz79

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Posted 30 September 2020 - 10:57 AM

The photons that hits us here on earth are considerably older than eight minutes. It is estimated that the photons that are released in the core of the sun may take up to 150,000 years of being absorbed and re-emitted within the sun before it even ever escapes.

Absolutely! For the sake of simplicity in the example, I'm just referring to photons once they've escaped into the visible spectrum. I guess you could equate it to the fact that you spend approximately 9 months in the womb before you're "born". If you look back from your first birthday, you could technically say that you have existed for one year and 9 months, even though your "birthday" was one year ago. :-p 


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#7 TOMDEY

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Posted 30 September 2020 - 11:44 AM

Yeah, I think about that kinda stuff a lot.

 

Adding to the philosophical/paradoxical/physicsical are these additional perplexing considerations >>>

 

> Photons themselves are literally ageless, because they travel ~at the speed of light~; their trip from source to absorption is instantaneous.

> Photons can be thought of as reinventing themselves at every moment along the way... Huygen's/Feynman's/Adam's principle.

> Photon is not an essential physical object, but only the name we use for a 100% entangled creation/destruction (emission/absorption/detection) event.

> In this sense, light bonds remote locations in space-time... is the stuff of communication.

 

The Universe may have already ended, yet we may have billions or more years to remain blissfully unaware of our inexorable demise!    Tom

 

As Jim Croce put it >>>

~~

If I could save time in a bottle
The first thing that I'd like to do
Is to save every day
'Til eternity passes away...

~~

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#8 PirateMike

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Posted 30 September 2020 - 12:26 PM

So, let me ask a question that many may have heard before.

 

If I stand six feet away from a wall then move to half the distance, to three feet, and repeat moving to half the distance for eternity, would I ever actually hit the wall?

 

But that is the way you may have heard the question. My question is a little different, and that is... would there ever come a time when you could move no closer?

 

I guess the typical answer would be no, but I say yes. What say Ye?

 

 

Miguel   8-)

 

.



#9 Jim Davis

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Posted 30 September 2020 - 12:39 PM

The photons that hits us here on earth are considerably older than eight minutes. It is estimated that the photons that are released in the core of the sun may take up to 150,000 years of being absorbed and re-emitted within the sun before it even ever escapes.

 

The energy may have been released that long ago, but the photon is not that old. The energy is released as gamma rays. These get absorbed by other particles, some of it turned to motion (heat) and some re-emitted as longer wavelengths. The energy of the original gamma rays ends up being released as many different lower energy photons, which come into being near the surface of the sun. Some is also released as motion of particles in the solar wind.
 


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#10 PirateMike

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Posted 30 September 2020 - 12:44 PM

The energy may have been released that long ago, but the photon is not that old. The energy is released as gamma rays. These get absorbed by other particles, some of it turned to motion (heat) and some re-emitted as longer wavelengths. The energy of the original gamma rays ends up being released as many different lower energy photons, which come into being near the surface of the sun. Some is also released as motion of particles in the solar wind.
 

Hey Jim. How are you doing?

 

 

You are certainly 100% correct, which bring us right back to the idea asserted above of "when you were born..."

 

I do know a little about how stars work, I read the books more than once, but not to worry, your clarifications are always welcomed. waytogo.gif

 

 

 

Miguel   8-)

 

.


Edited by PirateMike, 30 September 2020 - 12:49 PM.


#11 TOMDEY

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Posted 30 September 2020 - 01:05 PM

So, let me ask a question that many may have heard before.

If I stand six feet away from a wall then move to half the distance, to three feet, and repeat moving to half the distance for eternity, would I ever actually hit the wall?

But that is the way you may have heard the question. My question is a little different, and that is... would there ever come a time when you could move no closer?

I guess the typical answer would be no, but I say yes. What say Ye?

Miguel   8-)

Yes! That would be the Planck Time and Planck Length. On those miniscule scales, both time and space are no longer ordered (as in past/present/future, below/proximate/above, left/proximate/right, fore/proximate/aft. In effect, they are blended into a mush... a tiny space-time eventful mush, but not identically zero in extent.    Tom

~

The Planck time is the fundamental unit of time in the system of Planck Units. It has the value: tp = 5.39 × 10-44 s. In SI units, measurements of time are made in seconds (usually given the symbol s).

 

In physics, the Planck length, denoted ℓ P, is a unit of length that is the distance light in a perfect vacuum travels in one unit of Planck time. It is also the reduced Compton wavelength of a particle with Planck mass. It is equal to 1.616255(18)×10−35 m.

~

Tom



#12 llanitedave

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Posted 30 September 2020 - 02:12 PM

So, let me ask a question that many may have heard before.

 

If I stand six feet away from a wall then move to half the distance, to three feet, and repeat moving to half the distance for eternity, would I ever actually hit the wall?

 

But that is the way you may have heard the question. My question is a little different, and that is... would there ever come a time when you could move no closer?

 

I guess the typical answer would be no, but I say yes. What say Ye?

 

 

Miguel   8-)

 

.

Kind of depends on your waist size, doesn't it?
 


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#13 Fiz79

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Posted 30 September 2020 - 04:17 PM

Great discussion, thanks all!

 

I forgot to add in my original post that it’s funny to think that when Mars is at just before or after conjunction (the Sun in between Earth and Mars but out of the way enough so we could still see the planet), that the light from the Sun travels away from Earth up to 250 million km, reflects off Mars, travels back 250 million km past the Sun again, then another 150 million km to reach us. The total trip would be around 35 minutes. And that’s just Mars. Haven’t even thought about Neptune or even Pluto in this way.

 

It’s a simple thing I don’t think about much but when I force myself to, it boggles my mind. lol.gif 


Edited by Fiz79, 30 September 2020 - 04:20 PM.


#14 TOMDEY

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Posted 01 October 2020 - 12:42 AM

I sometimes think of each particulate "object" in the universe as just sitting in its own little box in some multidimensional matrix. And that when two objects interact, that's like a geometric wire connecting them... without their moving from their little pigeon holes. So then the entire interacting Universe of Stuff... just sits there, and the only things that are changing are those spaghetti wires slithering all over the place. Closely related to entanglements. If we could overtly see these wires/strings... they would be meandering all over, like a living sponge. Maybe it is that fabric that we more commonly call ~spacetime~? And its observed properties are constrained by what a mathematical sponge can and cannot be?    Tom

 

[thumbnail from Etsy Print Catalog... print no longer available]  >>>

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#15 BillP

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Posted 18 October 2020 - 08:32 PM

Yes! That would be the Planck Time and Planck Length. On those miniscule scales, both time and space are no longer ordered (as in past/present/future, below/proximate/above, left/proximate/right, fore/proximate/aft. In effect, they are blended into a mush... a tiny space-time eventful mush, but not identically zero in extent.    Tom

~

The Planck time is the fundamental unit of time in the system of Planck Units. It has the value: tp = 5.39 × 10-44 s. In SI units, measurements of time are made in seconds (usually given the symbol s).

 

In physics, the Planck length, denoted ℓ P, is a unit of length that is the distance light in a perfect vacuum travels in one unit of Planck time. It is also the reduced Compton wavelength of a particle with Planck mass. It is equal to 1.616255(18)×10−35 m.

~

Tom

I will offer the practical answer.  The scenario is about a person approaching a wall.  I doubt anyone would be able to move their entire body forward in an increment smaller than 1/8 inch even if they had the best muscle control on the planet.  So I say once they get about 1/8 inch from the wall, their next motion will hit the wall. lol.gif


Edited by BillP, 18 October 2020 - 08:33 PM.


#16 Lucullus

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Posted 24 October 2020 - 09:25 AM

[...]

 

It gets really interesting if you think about what would happen if the Sun just hypothetically...disappeared. If this happened, the photons that left the Sun right after the Sun vanished would take 8 minutes to get to us, so we wouldn't know that the Sun disappeared until 8 minutes later. At that point, the sky would be dark and we could look at Mars and still see it for quite some time afterwards, because the light that left the Sun right after it disappeared took considerably longer to reach Mars and reflect back to Earth, so we would then see Mars disappear as well some time later. Same goes for the other planets. One by one, they would fade away. The farther away they are from us, the longer it would take.

 

[...]

I could not help smiling at the imagination that upon realising what happened to the Sun and the sudden visual(!) disappearance of Mars, amateur astronomers turn their telescopes to all sorts of "remaining" solar system objects to get the last live views or images in their lifes (which suddenly turned shorter by decades for billions due to the lack of sunlight for plants... while the mighty ones will surely survive I wonder how many of those are active amateur astronomers... Putin with a 12" SCT on his balcony? I don't think so lol.gif , but who knows), preferably in the order of increasing heliocentric distances, and amateurs on the daysight of Earth tearing their hairs out of frustration, while some rent the few public telescopes there are in beneficial locations. But just imagine the havoc in professional community! Hundreds, or thousands of teams worldwide alert applying for observing time on hundreds of various instruments on a dozen of 8-10m telescopes, space telescopes, dozens to a hundred of small telescopes...
Seriously, how would such a pandemic demand for observing time be handled by professional boards? Would they be bypassed and the observational staff bribed for observations? Or would they become self-employed and mutiny on their professional board and sell observing time? Or would the professional boards themselves begin to sell telescope time, maybe even under increasing pressure from their observatory construction sponsors to generate hard cash income? ...All under the assumption that the telescope time becomes so precious that the involved begin to sell their time...

IR observations have a grace period concerning the slow cooling time of surfaces for increasingly large bodies. In the end tidally heated bodies due to tidal resonances such as the Galilean moons will be profiteers because they remain interesting targets for observations. Io will be a prominent target for thermal observations, as well as optically. Furthermore, it's volcanic activity might slightly illuminate the close vicinity... Or depending on aperture or integration time also further out.

 

"Light is fascinating"

Indeed!

A really fun calculation would be how the increased photon pressure "sunlight + backscattered straylight from ever more telescope optics on a target" alters their orbit negligibly grin.gif while not taking into account the sudden death of sunlight in all wavelengths. Let's take Ceres as a small target. How long would the Dawn space probe need to fly around Ceres, assuming lifetime is no problem (it "died" in 2018), in order to detect an influence due to the straylight.

Also interesting: the straylight of increasing telescope apertures will enlighten the target even after the Sun is dead. When the photons from straylight return to Earth, how much might the integration time in cameras be to make meaningful images, or for short exposures what aperture might be needed to make up for the dimming... in each straylight-emission-and-return-cycle tongue2.gif?



#17 GrandadCast

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Posted Yesterday, 10:19 PM

What if a photon is like a tiny explosion and right before it peaks it then travels at the speed of light. Since traveling at the speed of light, time stands still, frozen forever, until it hit something slowing it down and that tiny little explosion can now continue to puts out that tiny little bang of energy - on my CCD.

Jess




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