# Tag Info

34

The atmosphere rotates along with the Earth for the same reason you do. Force isn't needed to make something go. That's a basic law of physics - that a thing that's moving will just keep moving if there's no force on it. Force is needed either to make something change its speed, or to make its motion point in a new direction. A force can do both or just ...

20

This is from the Physics FAQ article that I wrote 15 years ago: If shorter wavelengths are scattered most strongly, then there is a puzzle as to why the sky does not appear violet, the colour with the shortest visible wavelength. The spectrum of light emission from the sun is not constant at all wavelengths, and additionally is absorbed by the high ...

16

The phenomenon is called Mirage (EDIT: I called it Fata Morgana earlier, but a Fata Morgana is a special case of mirage that's a bit more complex). The responsible effect is the dependence of the refractive index of air on the density of air, which, in turn, depends on the temperature of the air (hot air being less dense than cold air). A non-constant ...

15

Friction AKA wind resistance. You must have tried to stand in a strong wind or stuck you hand out the window of a traveling vehicle. From that you can feel the force that moving air exerts on objects in its way, and by Newton's law of reaction things in the way exert an equal force tending to move the air up to speed with the ground near it. Even if the ...

15

There are at least two reasons: the air layer adjacent to the Earth surface is dragged with it (being at rest with it). air viscosity -- it could be thought as a friction between different air layers. Upper layers are carried along by underlying layers. If the air were to stop suddenly it would result in ~1500 km/h wind speed. For comparison Hurricane ...

14

Aircraft rely on lift generated by interacting with the atmosphere and on using atmospheric oxygen to burn with fuel they carry. Orbits aren't stable until you are high enough that there isn't enough atmosphere to interact with, and long before that the oxygen content drops too low to be useful. So, to get to a stable orbit, you will need rockets ...

14

What you are seeing in those images is an ice halo. A halo is an optical phenomenon produced by ice crystals. Many can be observed while looking at the Sun or the Moon. To be precise, they are produced by the ice crystals in cirrus clouds high in the upper troposphere, at an altitude between 5 kilometres and 10 kilometres. The particular shape and ...

13

There are a lot of factors that go into whether or not a planet has an atmosphere. First, the mass and size of the planet. Really what it comes down to is the escape velocity. The higher the escape velocity (ve), the easier it is for a planet (or moon) to retain any atmosphere it gets as the gases that make up the atmosphere have to be moving faster to ...

12

Sonic boom refers to the explosive sound caused by the shock wave from an object traveling faster than the velocity of sound. Yes, It's actually spoken out as breaking the sound barrier. Felix jumped from an altitude of 39,044 km (which is 128,097 ft.) and reached a peak speed of 833 mph. Yes, He did produce the Sonic boom. Most likely, we use the term ...

11

Your first inclination is correct. It's a matter of scale. Jupiter is HUGE. I'll resist quoting Douglas Adams here, but the human brain just isn't equipped to deal with those sort of dimensions. Add to that the distance from which that photograph was taken. You are actually beyond the orbit of the moon Io in that picture, so scale will be even more set ...

11

No. A helicopter that "stays stationary" does so in relation to the atmosphere around it and the atmosphere pretty much follows the ground underneath it. The atmosphere does not stand still while the earth rotates. If it did, we would experience constant winds on the order of 1000 km/h. That would not be pleasant.

10

Crazy Buddy is quite correct that it's because gas expands and cools as it rises, but there is more to it than that. For something to be be heated it must either absorb EM radiation, or it must be heated by some hot object it's in contact with. Air doesn't absorb light so it can't be directly heated by sunlight. Instead the sunlight passes through the air ...

8

The ionized particles from mainly solar wind are caught and trapped by Earth magnetic field, which behaves like a magnetic bottle. (The region in which ions are trapped is called Van Allen radiation belts.) This trap is weaker in the polar regions, and there the ions are mainly released into the denser parts of atmosphere. There they collide with air ...

8

They would show only a very tiny negative positive weight. A typical kitchen scale has air above and below the weighing pan, and the pressure is very nearly the same because the thickness of the weighing pan is millimeters and the height of the atmosphere is a million times that. The net force of the pressure is quite small - equal to the weight of the air ...

8

I have always assumed it could be put down to a small set of causes: The stroke may have a physical extent and geometry that leads to a perceptible duration between the arrival of the sound due to the near part of the strike and that due to the far part. That is, what Georg said. If the geometry of the terrain is right you may be hearing echos off of cliff ...

8

Temperature generally gets cooler as you go higher in altitude (which is one reason why you have snow on mountain peaks long after it has melted away in the foothills). Hail develops in thunderstorms. A thunderstorm ~BY DEFINITION~ is a storm which has developed through the freezing layer. So think about this: If you see lightning or hear thunder from ...

8

The following telescopes certainly have adaptive optics systems: Keck VLT Palomar Mount Wilson CFHT Gemini Subaru Admittedly, some of these links aren't exactly clear, but I think they all confirm the presence of AO systems in those instruments. It doesn't appear that SALT uses adaptive optics, though there are proposals to implement it.

8

There are other wavelengths of light than visible and infrared. The venusian atmosphere is transparent to some of them, which also warm the surface of the planet. As the surface is warmed by these wavelengths, the infrared that it emits is trapped by the atmosphere. Over time this causes a runaway greenhouse effect, which is why the surface of Venus is hot ...

8

My guess would be that since Titan is 80% more massive than Luna, so the escape velocity is somewhat larger as well it is a lot colder there -- N$_2$/CH$_4$ molecules moving a lot slower on average there is considerably less Solar wind to blow particles from the top layers away Titan can hold its atmosphere indefinitely. I haven't done any ...

7

The key ingredient is temperature. If it were zero then all the air would indeed just fall down to the ground (actually, this is a simplification I'll address later). As you increase the temperature the atoms of the ground will start to wiggle more and they'll start to kick the air molecules giving them non-zero average height. So the atmosphere would move ...

7

Bend the light beam at the interface between a cold air mass with a mass of hot air as often seen in the mirage of the pavement. As we look into the hot air region we see the light comming from the colder region, the sky, as metalic surface. Physical explanation: The index of refraction of air exhibits a temperature dependence and makes the light rays ...

7

The previous answer is qualitatively too generous. The maximum frequency is the mean free path divided by the speed of sound, and it is a gradual thing, defined by greater and greater attenuation as you approach the limit rather than a sharp cutoff, as there is for phonons in a solid. The mean free path in air is 68nm, and the mean inter-atomic spacing is ...

7

He "only" flew at the maximum speed of 370 m/s or so which is much less than the speed of the meteoroids – the latter hit the Earth by speeds between 11,000 and 70,000 m/s. So he was about 2 orders of magnitude slower. The friction is correspondingly lower for Baumgartner. Note that even if he jumped from "infinity", he would only reach the escape velocity ...

7

The vertical part is relatively easy, but to be in orbit you need to be going fast enough horizontally, that's around 8km/s in low earth orbit. The balloon does nothing to help with that. There are launch vehicles that carry a rocket up to altitude underneath a plane and then fire that from 50,000ft. It means you don't need to use the rocket to get through ...

6

For what it's worth, even though a rocket starts its flight going straight up, once it has traveled through most of the atmosphere it soon starts to change its direction so that it spends most of its flight accelerating in the "around the earth" direction (i.e. basically horizontal). Also, to reach orbit a vehicle either has to reach a high enough speed, or ...

6

From the Wikipedia article:(My emphasis) Some people thought that the ozone hole should be above the sources of CFCs. However, CFCs are well mixed globally in the troposphere and the stratosphere. The reason for occurrence of the ozone hole above Antarctica is not because there are more CFCs concentrated but because the low temperatures help form polar ...

6

It is a mirage: in particular it is caused by hot air near the road and less hot air above it creates a gradient in the refractive index of the air and so making a virtual image of the sky appear to be on or below the road. Air currents make this shimmer, similar to a reflection of the sky on water, hence causing the illusion of wetness.

6

The etymology of limb for an astral object comes from the original Latin root. Limbus means border in Latin, a language in which all good students of last centuries were proficient, including astronomers; when describing heavenly bodies viewed through the telescopes they shortened it to limb. (astronomy) The apparent visual edge of a celestial body. (on ...

6

The atmosphere is not a simple two dimension spherical surface. You should also consider the convection up or down the atmosphere. Lets consider the following situation: A circular cylinder with heat flow into the system at the exactly middle bottom of the cylinder. So there are convection up near the central axis of the cylinder and there are convection ...

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