Can a large passenger airliner cast a shadow on the surface when at normal cruising altitude?
490916
In geometrical optics with a pointlike sun the airplane would cast a shodow on the surface.\n\nBut: 1) The sun isn't pointlike but appears as a disc in the sky, so if light from diffent edges of the disc would cross under the plane ther would be no sharp shadow anymore, from a viewpoint on the surface the plane wouldn't cover the sun as whole\n\n2) Light is a wave, so geometic optics is not the whole story, there is refraction that bends the light into the shadow region. That's what you call "refill the void".
654209
Most of the time, clouds have no such effect on planes of any size. \nIt is only storm clouds that shake the plane, and that is because storm clouds have violent winds swirling within them.\nPilots always try to avoid storm clouds. \nBut some storm clouds are so tall and wide that the pilot, to save lots of time and distance, will fly through the edge of the cloud, avoiding the most-violent part.\nMost modern planes, and all jets, have weather radar, which shows the violent part of the cloud.\n\nClouds DO have two minor effects on the flying experience:\n1) entering a cloud, which is denser than plain air, causes the engine noises to sound louder;\n2) when descending into a cloud from clear sunshine, the clouds will suddenly diffuse the sunshine, sending bright light into BOTH sides of the plane. It could be momentarily blinding.
422752
Smoke or fog will work.  There are also 100mW red lasers out there (wickedlasers.com should do the trick) that have some visibility in daylight, but this always depends on there being something (even the tiniest amount of dust) in the air to scatter off of.
147667
As far as the commercial airjets are concerned they do not carry radar.  The air traffic controllers track the aircraft on radar and ensure that planes are flying far enough behind the plane in front, and are not in the path of another plane.\n\nThe lights are on planes so that you can tell which direction the planes are traveling.  One side is red the other is green, depending on which light is on your left side, you can tell if the plane is flying to you or away from you.  The tail light also helps.  It will not allow you to avoid collisions, just to give you an idea of the direction planes around you are flying.\n\nAnd believe me, once you get above the cloud deck and flying at night, those lights can be seen for miles.  It's actually worse flying during the day, because you can't see the planes as well.\n\nIf you are travelling by plane (private) past a certain distance you have to file a flight plan, so that the air traffic controllers know your coming and can keep track of you during your flight, and keep all other flights away from you.\n\nAir collisions are actually very rare.  Lights do not prevent air collisions, air traffic controllers do.  They have a high stress job, but it's a very important job.
670367
Unidentified flying object.
943222
Only if the plane has engines with sufficient thrust to hold it up against gravity, and it orients itself engines-facing-down to hold itself there -- the most recent jet fighter for the US Air Force can do this, as well as some "jumper jets", but not any other planes and certainly not any commercial airliners can.\n\nRelative to the ground, a plane can be "still" if the wind speed aloft is above the plane's stall speed.  In that case, air is moving across the wings of the plane at a fast enough speed to give enough lift to keep the plane aloft even though it doesn't move relative to the ground (the thrust from the engines and the "headwind" balance each other out).\n\nYou can get a good sense of this if you fly a lot between the pacific coast of the US and Asia -- the strong jetstream across the pacific does funny things to "ground" speed.  When flying west to east (with the jet stream), indicated ground speed on flights I've been on has exceeded 1,000 MPH, even though the plane can't go more than 400 MPH or so with no wind.  And flying east to west, indicated air speed will sometimes be as low as 50-60 MPH, even though airspeed is still 400MPH -- that headwind jetstream is a killer, and significantly lengthens the time it takes to get from LA to Tokyo (the normal 11-hour flight once took us 16 hours because of the headwind!) -- though I've made the return trip in under 7 hours!
123579
Shadows should be black, because a shadow is abscence of light. But really the air scatters lights, and what you see is the surface where the shadow is illuminated by this scattered light or by reflection on another surface.\nWhere there is no atmosphere you will see deep black shadows, for example in the pictures of astronauts in the moon.
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.
90810
Yes.  Air cools at about 2 deg. C. per 1000 feet.  It is quite cold up in the sky where the big ol' planes fly.
927237
It appears that the range is classified, but it can refuel in air anyway, so no, it doesn't need to land to go around the world.  It could, theoretically circumvent the world several times, as long as they had supplies and enough pilots to rotate shifts.
517769
In the US, see the FAA web site, FAR part 103. The aircraft must not be capable of more than 55 knots calibrated airspeed at full power in level flight.\n\nDo you know there is a special category for aircraft questions?
258869
In a dark(ened) room.\nUse a smal lamp. Move it up and down. Choose one pupil and let the other ones see how the length of his shadow changes with the altitude of the lamp.
454642
Let's see if I can remember is - I've been flying a lot lately:\n\nLadies and gentlemen, on behalf of ________ Airlines, I'd like to welcome you to our non-stop flight to _________.  Our flight time today is approximately ____ hours and ____ minutes.  As we prepare for take-off, I'd like to remind everyone to place their seatbacks up and return their tables to the stowed position.  All carryons should be stowed in the overhead bins or under the seat in front of you.  In a moment, we'll be showing a video about some of the safety features of our aircraft.  We ask that you remove the brochure from the seatback in front of you and follow along.  We'd like to remind you that this is a non-smoking flight.  Smoking or tampering with any smoke detectors is a federal offense.  As we prepare to taxi, all electronic devices must be turned to the off position and remain so until we are approximately 10 minutes into the flight.  The seatbelt sign is currently illuminated and any time it's illuminated, you must remain in your seat with your seatbelt fastened.  When we have reached a safe cruising altitude, the captain will turn off the seatbelt sign, but we encourage you to keep it fastened anytime you are in your seat.  Now sit back and relax as we show our safety video.\n\nHow's that?
107381
I agree, your English is poor but I think you are asking:\n\nWhen flying in aeroplane, how much pressure is outside? \n\nThe exact outside pressure will depend on the altitude at which you are flying. At a common cruising altitude of  37,000 feet, the outside air pressure is about 3.2 psi. At sea level it is 14.7 psi.  \n\nWhy does it sometimes shake?\n\nFlying in an airplane through air is just like riding in a car along a bumpy dirt road or a ship across choppy open water. The air, while invisible, is very much like an ocean and is always in motion while the aircraft moves through it. The more turbulent the air mass, the more the plane will bouce or shake as it passes through it. At high speeds the air takes on fluid like properties around an aircraft. The oceans are not always calm and glassy and neither is the air which is a constant mass in motion. Just like a journey on the seas or a country road, you cannot always expect your journey to be completely smooth.
119190
Technically yes, you would be able to see to the edge provided nothing was obscuring your view (like buildings or trees).  The problem is that dust, water vapor, and other impurities in the atmosphere would place some limitations on how far you could see.
985973
Actually this is quite possible.  The key is that the laser emits a wavelength which interacts with the N2, O2, and CO2 in the air.  Each of those molecules have specific absorption and emission spectra.  As they absorb the frequencies (research their respective absorption spectra through Wikipedia or Google) of the radiation (not necessarily light) that passes through them, the light will scatter with re-emission at different frequencies (their respective emission spectra), as if reflecting off of  an object.  They wavelengths are the important part, and not necessarily the coherency (as inherent in lasers) which tends to constructively interfere to produce "laser speckle."  The primary reason one might choose a laser is ability to key the energy on the specific frequencies of interest and to control the path of the light.  You would want mirrors on the ceiling and the floor to be perfectly aligned to allow the reflected beams to cover more area of the "laser wall" with multiple reflections from partial reflectors distributing the energy from a primary source through multiple small holes in the mirrors on the floor.  Alignment of the optics, and stability (environmental isolation) would be critical issues of the system.  Normal vibrations and movements of the geology and the house will interfere with the alignment unless properly isolated from it.
1053233
the hot pavement creates a layer of hot air just above it.. and the cooler air above that make a difference in density barrier.. which reflects light... as long as it is below a specific angle <so you see the reflection from far off but not right at your feet>\n\nI think.. hehe