when we observe an horizon is it bent or is it straight?
964062
Hi. It is bent at any height above zero. Look at the horizon from a spacecraft and you'll see this. The bending gets reduced as you approach zero height, at which point it is a flat circle.
494502
This question is answered very well in solid geometry.\n\nOn a plane, it's a straight line.\n\nOn the surface of a sphere, it's a curved-line called a great circle.\n\nIn space, considering the curvature caused by the masses of any nearby bodies between you and the destination point, it may be a complex three-dimensional curve.
551537
The line that connects the two points of the crescent Moon is always almost at right angles to the path of the Moon along the sky. If the Moon goes up almost straight from the horizon (as it does when seen from the equator), then the crescent appears horizontal. If the Moon rises at a shallow angle (as seen far from the equator), then it moves as well along the horizon towards the west, and then the crescent is mostly vertical. The Moon rises almost vertically as seen from the equator because the orbit of the Moon stands approximately above the equator.
124314
Actually, this happens only under certain atmospheric conditions, when the air is quite clear. It is because the speed of light in the layers of air near the ground is slower than the speed of light in layers of air above that. Therefore, just like a lens, the light is bent by this gradient in the speed of light. \n\nRefraction of light is a wavelength-dependent phenomenon. The longest wavelengths are bent, or refracted the least. and the shortest wavelengths are bent the most. The reds, yellows and oranges are the long wavelengths, and they will bend the least, and will head off into space. The shorter wavelengths, the blues and greens and violets will be bent down by the atmosphere to be visible at the ground. In fact, the sun is actually below the horizon for the last few minutes of the sunset. The light has to bend around the earth, and the color that gets bent the most includes the short wavelengths. \n\nWhy do we see green in the green flash, and not violet or blue? There is also Rayleigh-Tyndall scattering going on, caused by the small nitrogen and oxygen molecules in the air. The shortest wavelengths are most scattered by the air molecules, and are scattered out of the sunlight, leaving longer wavelengths for us to see. The blues and violets have very short wavelengths, and are therefore scattered the most. (This is the same process that creates blue skies and orange and red suns at sunset). However, in this case, the yellows and reds and oranges are not present in the sunlight as the sun sets below the horizon, but have travelled out into space, so only the greens, blues and violets remain. The blues and violets are scattered away, leaving the green for us to see as a green flash. \n\nA more complete explanation complete with pictures is in the references.\n\nIt is also interesting to note that the moon can also exhibit a green flash, or a green edge (and also a red edge, in a kind of red flash). At the poles, when the sun is barely below the horizon for hours, the green flash can last for hours apparently, according to friends that have seen it.
301180
Also, we only see it when it is above the horizon.\n\nDuring the day, the sun is obviously above the horizon.  But the moon sets an hour or so later each day, so sometimes it is below the horizon in the day, and sometimes not.
104230
This shape is called the "omega shape", at least as the lower limb of the sun disappears beneath the apparent horizon (the sun has already set quite a bit farther beneath the horizon and one is only seeing so much of the sun because of refraction effects). It is called an omega because it is not strictly an oval or ellipse at that point, and actually has a pair of "feet" at the bottom like an omega. \n\n The actual shape will vary, depending on refraction effects, and those depend on the temperature profile of the atmospheric layers. The shape is typically computed in a simulation by ray-tracing, although one might be able to do some sort of approximation by an ellipse. See the attached link for more details.
359151
No.  The angle between the sun and the moon as viewed from the earth is 180 degrees for the full moon pahse.  This means that the full moon and the sun are always on opposite sides of the earth.\n\nSince the moon is not always "in plane" with the sun, and your horizon is not perfect, it may be possible on occasion, depending on the geography of the horizon, and one's latitute to see the full moon rising as the sun is setting, or to see the full moon setting as the sun is rising.
484670
The easiest way to remember which way horizontal is, is that is goes in the same direction as the horizon
257670
Depends on visibility.\n\nYes, the Earth curves out of sight.\n\nhttp://www.boatsafe.com/kids/distance.htm\n\nhttp://science.howstuffworks.com/question198.htm\n\nHere is a site that will do the math for you:\n\nhttp://www.boatsafe.com/tools/horizon.htm
962965
Here's what happens: imagine you're standing with the Sun at your back looking at a water drop. As a light ray from the Sun hits the drop, it is bent inwards, toward the center of the drop. It bounces off the back of the drop (coming towards you again) and then refracts again on its way out. As a result you see the light ray appearing to come from some point behind the drop, that is, on the opposite side of the sky from the sun (which is where you see rainbows!) \n\n\nBut what about the colors? It turns out that each color of light is bent a little bit differently - red light is bent the least and violet the most. So, each color appears to be coming from a slightly different place behind the water drop. \n\nThe rainbow is circular because only drops located at certain places on the sky (in a circle around the point opposite the Sun) redirect the light exactly back toward your eye. It's only the light from those drops that you see, and hence you see a circle.\n\nanother explaination: This is difficult to envision and to describe, but we'll use some real common sense objects for our model. Picture yourslf standing in front of a tunnel, like you might find under a bridge - a nice even, round, smooth tunnel. Now, if you cast a shadow parallel to the ground, like a shadow from a power line (not the pole, the line - which is parallel to the ground) and let the shadow fall inside the tunnel, you can imagine that the shape of the shadow on the ceiling of the curved tunnel looks as though it is arced, even though the source of the shadow is a straight line. Can you picture that? This is what is happening in the atmosphere. The rainbow is actually a straight line, since light travels in a straight line. Its just that the straight line is falling across a 'fish bowl' like pocket of moist, reflective air, like our tunnel in the model. The rainbow appears, therefore, to be an arc.
439985
short answer:  grey disappears in the horizon, making for a less visible target.
245562
I think at space is round like the earth and that there really  not straight flat
444832
As the light from the sun enters the atmosphere, the atmosphere bends it a certain amount. Because the sun is closer to the horizon at sunrise and sunset, there is more atmosphere to bend the incoming light rays. Hence, the sun appears larger at sunrise and sunset because of atmospheric lensing.
974637
That is a good question, it's mainly an illusion but I'm not sure why they looked curved though.
31265
Frosty is right, Otisabi is wrong. The round shape of the atmosphere bends the light. You also get a reddish taint to the moons colour when it's close to the horizon. This is due to the red part of the light reflected from the moon hitting your eye, while the rest is into space. If you've ever looked into a round fishbowl you'll see how it distorts light to make things look larger.
967418
yes there are straight lines. what you describe is according to the earth and the solar systems that appear round due to the force that acts from all directions creating a universal container (the sphere) which is round. But look at the BIGGER picture a straight line has to exist even if it is as small as an atom (universe - meter scale). also there are other geometrical forms. infact the only reason why round is soo common in all universal shapes (objects). well think of all forces acting on a body from all sides then reason the kind of shape it will produce when all forces level out the object.
1153025
Bart,\nGood question bro, and the answer is fairly simple. As an aviator I've been from ground level to 35,000 ft and the reason why the horizon appears to be at eye level is something called 'Line of Sight'.\n\nThe earth is curved right? Well - to truly get a glimpse of the earths curvature your going to have to be well into the Stratosphere to notice that the horizon begins to go below your line of sight at those altitudes. Anything below that, the curve of the earth is going to intercept the angle at which you view it, and appear to be level at your level (the point where the earth's curve is in your 'Line of Sight'.\n\nHope this helped bro, take it easy out there.