Atmospheric refraction

pilotod

pilotod

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This something I just found out. Maybe some of you already know about this. When we see the sun just above the horizon, it really is just below the horizon due to atmospheric refraction. For some reason I'm just stunned to find this out.:goofy:

15do2no.jpg
 
It's dark magic I say! Here's a clip from QI, a British show that I find hilarious, on this exact subject:

 
pilotod said:
This something I just found out. Maybe some of you already know about this. When we see the sun just above the horizon, it really is just below the horizon due to atmospheric refraction. For some reason I'm just stunned to find this out.:goofy:

15do2no.jpg
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High school science class.:dunno:

You do know it takes 8 minutes for the light from the sun to reach earth?

That the "surface" of the sun rotates once every 25 - 36 days? It is not consistent?

That the energy being radiated from the sun is NOT constant? That it effects our weather patterns way more than anything man does? You do know man made global warming is a myth made up by politicians to tax us more?
 
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I'm only just getting around to learning theoretical physics and the other dimensions. But high school? I remember a couple of teachers and girls but that's about it.

Your post has some nice irony in your last sentence. At first I thought you might be super intelligent. What kinds of things do you read about the environment?

Geico266 said:
High school science class.:dunno:

You do know it takes 8 minutes for the light from the sun to reach earth?

That the "surface" of the sun rotates once every 25 - 36 days? It is not consistent?

That the energy being radiated from the sun is NOT constant? That it effects our weather patterns way more than anything man does? You do know man made global warming is a myth made up by politicians to tax us more?
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pilotod said:
Your post has some nice irony in your last sentence. At first I thought you might be super intelligent. What kinds of things do you read about the environment?
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Go with your first thought. :lol:

Maybe you should start questioning what you are reading. ;)
 
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I feel confirmed! I'll have to check out that show.

jpower said:
It's dark magic I say! Here's a clip from QI, a British show that I find hilarious, on this exact subject:
Click to expand...
 
A related fact: the official times of sunrise and sunset show that at the equinox, the day is several minutes longer than the night. That's because official sunrise and sunset are calculated based on when the sun's leading edge lifts above the horizon at sunrise, and when its trailing edge sinks below the horizon at sunset. The point that's above the horizon 12 hours on the equinox is the sun's geometric center. But that doesn't account for all of the difference; in fact most of it is because of refraction.

A few years ago I was driving down a road running due west at sunset a day or two after the autumnal equinox and was amused to see the sun setting slightly to the right of the road, when it actually sets south of west on the winter side of the equinoxes. Of course, it was already actually below the horizon and I was seeing a mirage. :D
 
azure said:
A few years ago I was driving down a road running due west at sunset a day or two after the autumnal equinox and was amused to see the sun setting slightly to the right of the road, when it actually sets south of west on the winter side of the equinoxes. Of course, it was already actually below the horizon and I was seeing a mirage. :D
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True north vs magnetic north vs ecliptic?
 
azure said:
It was true west, not magnetic, if that's what you mean.
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Yeah, I just wonder if true west is actually in line with the plane of the solar system come equinox time.
 
the interesting thing is that the refracted light does not include infrared or UV. So there is almost zero heating of the ground created by the sun when it is actually below the horizon but can be seen by refraction - the infrared gets refracted into the ground long before it reaches you and the UV is scattered above you - little of either reaches the ground -

FWIW - the definition of sunset/sunrise is when the sun is -0.83 degrees below the horizon. . .,
 
EdFred said:
Yeah, I just wonder if true west is actually in line with the plane of the solar system come equinox time.
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NO.

The Ecliptic is the plane that the planets move in and it not generally true east and west and certainly is never vertical to the horizon EXCEPT at the equator -

Not all planets revolve exactly in the plane either.

If you start paying attention to this you will see that the moon is inclined 5 degrees to the ecliptic which is why we don't get eclipses every month. Moreover, depending on phase of the moon the moon is within 5 N or S of where the Sun would be at the same right ascension in its orbit.

When the moon is near its southern declinations it may not even be visible from Anchorage and Fairbanks - this can most easily be seen in summer when the moon never rises or sets - the math is as such - Fairbanks is at 64.8N - if there is a moon near the southern limit it can be as far south as -28.8 declination. if you add 28.8 and 64.8 you get more than 90 - which puts the moon below the horizon. the further north you go - the more often the moon is not visible.

Then the earliest sunrise or sunset is not on the solstices. Most folks confuse longest or shortest day with the earliest sunrise and sunset - and that only works the further away from the equator you get.

For example in Hawaii the earliest sunset is in early November, its December 5 in Los Angeles and December 9 or 10th in New York . . . .
 
comanchepilot said:
the interesting thing is that the refracted light does not include infrared or UV. So there is almost zero heating of the ground created by the sun when it is actually below the horizon but can be seen by refraction - the infrared gets refracted into the ground long before it reaches you and the UV is scattered above you - little of either reaches the ground -

FWIW - the definition of sunset/sunrise is when the sun is -0.83 degrees below the horizon. . .,
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Nope. IR light refracts, just less than visible light. I'm working on a paper on that at this very instant.... As a function of wavelength, temperature and pressure, in addition to the usual elevation angle.

At least those parts of IR that are passed through the troposphere. Big hunks of it don't make it to the ground, but are absorbed mostly by water vapor and reradiated at longer wavelengths.

Near IR isn't that different from red.

The lunar orbit isn't well described by a conic section, so its inclination to the ecliptic is variable. Tidal forces and perturbations from Jupiter and other planets are significant. Those of us who have to calculate its position with precision tear our hair out over it.

There are multiple definitions of sunset (and twilight). It's not just the FAA that does that. We'll do IR observations at the start of civil twilight if the stars are bright enough -- the limiting factor is getting the sun in the aperture; imagine a 2.5m magnifying glass. For dimmer stars, we need more like -5 deg elevation.
 
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While on the topic you may also learn an interesting fact about light refraction.

It is related to the fact that speed of light decreases in a denser substance (it is fastest in vacuum of course).

Now the refraction is a consequence of the above and the principle that to travel from point A and B light will select path with the least travel time. If you do the basic math you will see that light must refract in order to satisfy this least time principle.

This least travel time principle also explains reflection of light from mirrors.

Fermat was the first scientist who discovered this 'least time' principle for light.

This "least of something path" carries over to the Newtonian mechanics - in calculus of variation you can formulate the whole classical mechanics using it (so called Lagrangian approach). It also carries over to quantum physics - Richard Feynman was able to formulate quantum physics using calculus of variation rather than more typical Heisenberg's or Schroedinger's approach (this is a fairly modern discovery).
 
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And may I add that Feynman is pretty damn funny....I'm listening to his book ..."Surely You're Joking...."


olasek said:
It also carries over to quantum physics - Richard Feynman was able to formulate quantum physics using calculus of variation rather than more typical Heisenberg's or Schroedinger's approach (this is a fairly modern discovery).
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olasek said:
While on the topic you may also learn an interesting fact about light refraction.

It is related to the fact that speed of light decreases in a denser substance (it is fastest in vacuum of course).

Now the refraction is a consequence of the above and the principle that to travel from point A and B light will select path with the least travel time. If you do the basic math you will see that light must refract in order to satisfy this least time principle.

This least travel time principle also explains reflection of light from mirrors.

Fermat was the first scientist who discovered this 'least time' principle for light.

This "least of something path" carries over to the Newtonian mechanics - in calculus of variation you can formulate the whole classical mechanics using it (so called Lagrangian approach). It also carries over to quantum physics - Richard Feynman was able to formulate quantum physics using calculus of variation rather than more typical Heisenberg's or Schroedinger's approach (this is a fairly modern discovery).
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I I have learned that when you turn the nut to the right it usually gets tighter!

IOW :confused:
 
colojo said:
I wish US television was half this intelligent.
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Episodically, it is.

But you have to look for it.

It's highly dated, but Carl Sagan made a very interesting contribution to public astrophysics in the 80s, in the form of a complete television series that aired on PBS. It was VERY good, but unfortunately he chose a topic that was changing rapidly at the time.
 
pilotod said:
And may I add that Feynman is pretty damn funny....I'm listening to his book ..."Surely You're Joking...."
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He was also too damn smart for his own good. He managed to kill off any reasonable discussion of the reasons renormalization models work in the physics community. His explanation is obviously mathematically incorrect (it assumes Laurent series converge, but they don't), but it's verified by experiment to high precision, so it's not "interesting."

He was a gifted lecturer.
 
MAKG1 said:
He was a gifted lecturer.
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He is one of the main contributors to Quantum Electrodynamics (actually one of its founding fathers) for which he received the Nobel prize so I would say his gifts extended beyond the lecture hall.
 
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