Sky Definition and 265 Threads

Does anyone have any stories of close calls from objects falling out of windows of high rises in the city (or elsewhere)? I was watching the Ken Burnes series on the civil war recently and they said that the women in New Orleans used to dump their chamberpots on the occupying Union soldiers...

Janus submitted a new PF Insights post How Representative is the Night Sky? Continue reading the Original PF Insights Post.

Another interesting article Pi in the sky by the intrepid duo Ali Frolop, and Douglas Scott. Those pesky CMB anomalies again! Garth

Hi! I'm not studying physics and what I know about light is mostly what I've read on the internet and what I've learn thinking and observing the nature. I come to realize that the space is full of light. When I look at the black space, I don't see light but I know that is light everywhere up...

I was thinking about adding another page to my website concerning the nearest stars, the brightest stars, etc. In a list of the nearest stars, the vast majority are brighter than the Sun. (I looked for stars with an absolute magnitude that was greater than the Sun's (4.85) and had a visual...

Homework Statement Is sky wave signal less stable than ground wave signal? Homework Equations None The Attempt at a Solution Ground waves face attenuation because when it glides over the surface of earth, there will be induced fields which can oppose the wave. In case of sky waves, it...

suppose there is an astronaut sitting in a space station orbiting Earth, what colour would the sky appear to him? Same as us? Why or why not? Thanks!

What would be the propable trajectory and position of the ninth planet that has been suggested few days ago (20.1.2016 by Konstantin Batygin and Michael E. Brown) ? if i understood correctly, the exact position of the planet is unknown and has not been evaluated. But by looking this article...

There seems to be enough of us night owls who use DSS for me to open a discussion about how to 'tune' all of the parameters to get an optimal result. Personally, I've used the program for a few years but still have no clue about many of the settings, and would appreciate any insight. First...

If the atmosphere was thiner would the sky be violet?, and if it was thicker would it be red?

From time to time I see discussions about the expansion of the universe that describe a future state where the view of the sky from Earth (assuming Earth were to still be in existence) will be completely dark. There are two possible explanations of this prediction. 1. The universe will...

Let's put an observer hovering near the event horizon of a charged black hole. As the black hole is charged we can change its velocity from zero to 10 m/s in one second. But we can not send a message to the observer in one second. So the observer does not know that the black hole that he is...

Though the intensity of violet light is more than that of blue we see the sky blue.Why this happens?Does it happen only for that our eyes are more sensible towards blue light than violet light or due to absorption of violet light by Ozone layer? And why different light waves having different...

I know the question is generally "Why is the evening sky red/orange?" but actually the evening sky is very rarely red/orange. On most evenings it is blue. Why is it blue? Shouldn't it be red/orangish? Does the location on Earth have anything to do with this?

I want to know, excluding the sun with an appropriate boundary, whether it is possible for the balance of bbr to be positive for outerspace rather than on earth? I am thinking of a half convex with an active polariser across-the outer surface which allows through most radiation below the...

I've searched the internet and found a few sites, of varying depth, that contain some of the equations to calculating the solar path. At the moment, I'm not particularly concerned with precision. I am trying to discern the equations in order to implement them into a java program I am writing...

I'm quite aware of how to compute how FAR you are from the horizon, but my question is, how WIDE is the observable horizon at sea level (like, from left to right, how many kilometers is this): http://www.jeicentral.com/wp-content/uploads/2014/10/far_sunset_in_te_ocean_horizon-wide.jpg Thanks!

Hi! :) This is my first message here. The reason I joined this forum is because there are some knowledgeable people here who might be able to shed some light on an observation that I cannot explain. It happened during the night of July 28, 2013, at around midnight, and it still keeps me...

Hi, If you were to half Earth's orbit around a K4.5V main sequence star (assuming the same composition and density of atmosphere), what colour would the sky be? Thanks in advance. Chinspinner

Hi all! In the absurd hypothesis that we could take all water from Earth's oceans and distribute it equally through the sky ceiling (as shown below). We have the point of view of an observer in the land. Questions: 1. We know that the water pressure rises as we come closer to Earth's core...

I have some confusions about this that I'm not finding clear answers for. First, looking at the color violet, it looks like a sort of "purple". The answer as I've understood it to why the sky doesn't appear violet or this "purple" is that it has to do with a combination of the fact that there...

Well today my mother got a pretty nice camera, she's been wanting one for a while and what better way to test it then getting some shots of the moon! This is the best photo she could get, the rest were very shaky and we're probably going to invest in a tripod. I also went out with my cheapy...

I've had a telescope for a few years. I know pretty basic stuff - and I can easily find planets when they are in the sky (mostly because I know Venus is around sunrise/sunset, and Jupiter & Saturn are non-twinkling bright objects in the sky). I know a few constellations - Cassiopeia, Orion, Ursa...

I have a location of approximately 35 deg 14' S and 149 deg 4' E, and I have measured the position of the star Antares to be at an altitude of 27 deg 00' using an inclinometer, and direction 247 deg using a compass. Using this information can I calculate the direction of the star on the...

It is very well known that the sky scattering of visible light decrease with the wavelength, it is bigger in the blue portion of the spectrum( the reason why the sky is blue ) and is lower on the red portion of the spectrum, this scattering is even lower on the infrared section and lower still...

Homework Statement If the Earth did not spin on its axis, would the other planets still appear to move across the sky? Justify your answer. Homework Equations N/A The Attempt at a Solution If the Earth continued to rotate around the sun but NOT on it's own axis then wouldn't...

I imagine it depends on the chemical makeup of their atmospheres.

Found this great chart!

The light from stars radiates out from them as a sphere. When a part of the surface of the light sphere reaches the earth, it is far enough away from the star so that each point on that part of the surface of the sphere near the Earth has about the same light energy. But, I only see a point...

I was practicing for my upcoming optics exams, by making an old exam. And got stuck on some problems that seem so silly. 1. Why is the sky blue? My answer: To answer this problem I first need to mention Rayleigh Scattering, a form of scattering which has a very large wavelength...

I've long used GoSkyWatch Planetarium. The augmented reality using GPS is very smooth and it's easy to find objects. http://www.gosoftworks.com/GoSkyWatch/GoSkyWatch.html I know there are a few of these out there. Which are you using?

Why is separation of Earth and sky so common in different mythologies around the world? EDIT: Sorry about my poor phrasing of the question. My question is actually why people would assume Earth and sky were joined once. Which observation/ reasoning led them to make up such a non-obvious story...

Homework Statement Find the angle ϕ between the filter's polarizing axis and the direction of polarization of light necessary to increase the ratio of the clouds' intensity to that of the blue sky so that it is three times the normal value. Express your answer in degrees to four significant...

I was wondering about how much of the night sky one could see from various locations on the Earth. At anyone time, near sea level, how much is visible? My guess is that much less than half is visible, with the rest being blocked from view by the earth. Is that correct? How small a portion...

Lets say Earths atmosphere with the same composition of gases was 500 bar. Would the sky be red instead of blue because light from the Sun would have to travel through more atmosphere?

The latest quasar catalog, SDSS DR10, has been released - http://arxiv.org/abs/1311.4870! Yes, I know, you can hardly contain your excitement.

1. In 1956, Frank Lloyd Wright proposed the construction of a mile-high building in Chicago. Suppose the building had been constructed. Ignoring Earth's rotation, find the change in your weight if you were to ride an elevator from the street level, where you weigh 600N, to the top of the...

Hello, I am doing an assignment, and am required to work out how much of the sky can be imaged in a single night by a telescope. If the amount of celestial sphere that is visible for this particular site is 26360.64 degree squared for the 12 hours. The field of view of the telescope is 2100 x...

Homework Statement Mike Harris stands at the very top of the sky dome stadium roof to pitch the opening ball for the Blue Jays game. He slips a bit left of centre and slides down along the frictionless roof surface. For what distance, measured along the curve, will he slide before leaving the...

A physics stack question asks why when the air is hotter then your body thermodynamics allows your body to operate as a heat engine as a heat engine must have a sink for waste heat. See question here, http://physics.stackexchange.com/questions/59316/human-as-a-heat-engine Part of the answer is...

I am currently in training to become an analyst using thermal imagery. In the studies I have been introduced to cold sky reflection on thermal imagery, however the instructor explained it as a surface 'reflecting the cold from the sky' which, as far as I'm aware, doesn't fit with the second law...

An object (a tin can for example) orbiting the Sun at about the same distance as the Earth would be what temperature?

Suppose it's the equinox, when the Earth's closest point to the sun is the equator. Would people who live somewhere along the equator see the sun rise directly from the east, move directly above so, and set directly to the west? For instance, if someone, living on the equator, were to put a...

Hello, I have a novice question. I know that the sky color is blue (at noon, when there is no clouds), because the air particles (mostly N2 and a little O2 ...and other) scatter short-wavelength light more than longer wavelengths. That is why we can't see the stars trought the atmosphere...

Hello and thank you for allowing me to post a question. I am not very familiar with systems engineering and have a question about the frame joints connecting the main body of the MSL (Mars Science Laboratory) powered descent stage with its 8 Aerojet MR-80B 800 lbs thrusters (1). I am...

Homework Statement When viewed from Earth, the Moon subtends an angle of 0.5° in the sky. How large an image of the Moon will be formed by the 3.6 m diameter mirror of the Canada-France-Hawaii Telescope, which has a focal length of 8.5 m? Homework Equations 1/s + 1/s' = 1/f, but I'm...

Homework Statement What is the best physics modeling for the motion of sky lantern? can I assume that the temperature in the lantern same in every place so that the air density is same too? Homework Equations The Attempt at a SolutionHomework Statement Homework Equations The Attempt at a...

is it possible to harness the lightning to get electricity.

free fall equations ...Sky diver Felix :) need some help please hi :) OK..i tried to use the equations below to evaluate the distance or the time at which felix will reach the speed of sound ...but i failed ..i need some help: here what i did: first i neglect the air resistance , but the...

Hallo PF, Both are startups working on high altitude wind power generation. In general, both uses some sought of kite design to keep the generator afloat in air and the high velocity winds rotate the propellers of generators producing power. However, in Makani the kite travels along a...