does earth's atmosphere have a clearly defined top?
535445
No it does not.\n\nThe outermost layer is called the "exosphere" and opinions differ as to where it ends and space begins.\n\nHere is a quote from the link below:\nThe atmosphere has no abrupt cut-off. It slowly becomes thinner and fades away into space. There is no definite boundary between the atmosphere and outer space. Three-quarters of the atmosphere's mass is within 11 km of the planetary surface.\n\nIn the United States, persons who travel above an altitude of 50.0 miles (80.5 km) are designated as astronauts. An altitude of 120 km (75 mi or 400,000 ft) marks the boundary where atmospheric effects become noticeable during re-entry. The Karman line, at 100 km (62 mi), is also frequently used as the boundary between atmosphere and space.
25248
First of all, there is no fixed end to the atmosphere: it gradually fades away to the density of interplanetary space.  However, the effective "top" of the atmosphere is often taken to be 60 miles (100 km), the altitude at which a (typical) unpowered satellite could make one orbit before air drag slowed it and caused it to fall.\nTo reach this altitude only requires that an object be headed upward, no matter how slowly.  To move upward requires that the object have some force propeling it which is at least slightly greater than the force of gravity pulling it down.  This force of gravity lessens with altitude, which is why a rocket needs a lot of power to take off, but little to maneuver in orbit.  Thus there is no minimum speed needed to reach the "top" of the atmosphere.\nHowever, the orbital velocity needed to stay in orbit is that velocity which just equals the downward pull of gravity, so orbital speed depends on the altitude of the satellite: it goes down with altitude.  (For example, at a typical low-orbit altitude of a couple hundred miles or so, the speed is around 17,000 miles per hour and the orbital period for one orbit is around an hour and a half; the Moon, 238,000 miles away, moves about 2000 mph and takes 28 days to orbit once. For mathematical details, see references on Kepler's Laws.
132804
i would say it depends where in the sky. I'm sure it's different over a polluted city and somewhere between, say, Mars and Saturn.\nsorry if it doesn't answer ur question
956514
Hi. I read your other answer. See below. The atmosphere is almost 93,000 000 miles away, so don't worry. Earth is more that just wonderful. It is exceedingly rare in my opinion. Together with the Moon, her oceans, her temperature, her atmospheric environment - all these make for an unusual combination of life supporting qualities. We should cherish this home we have.\n----------------------\n"This is wonderfull idea! Just imagine if could expand the size of our tiny little planet.\n\nOn the downside though, it is believed that the dimensions of earth is perfect for the exixtence of life on it. if we made her any bigger, our atmosphere would be too close to the sun, and earth would fry like a tomato.\n\nJust my opinion."
261896
The earths atmosphere\n\n\nMy first thought was not formal. What I thought when I read your question is that nothing is between heaven and earth that "the heavens" come down and touch the earth.
427552
X-rays are absorbed by the topmost levels of the earth's atmosphere.\nThe same applies to the gamma radiation emitted by the sun.\n\nWhen the incoming radiation strikes the top of the atmosphere, it interacts with the air molecules and is absorbed (by being broken into a shower of exotic particles, none of which exist for long enough to reach the surface of the planet)\n\nThere are two windows for which radiation reaches the ground, One starting at UV through to visible light and to Infrared, and the Radiowave window which satellites communicate through.
581432
atmospheric pressure, winds, light
453537
There are in fact many different atmospheric layers as you move upward away from the earth. However, there are NOT different layers of gases. All the gases are sort of mixed.\n\nThe troposphere, the atmospheric layer that we live in, contains the most gases. This is due to gravity. Anything that has mass will be attracted to earth's gravity.\n\nThat is why when you move away from the earth there is less air. Less gravity = less air!\n\nThe higher you go in the troposphere, the colder it gets. That is also due to less air (holds heat).\n\nThe next layer up is the stratosphere. This layer is where most jets fly & where the atmospheric ozone layer exists.\n\nTemperatures in the stratosphere will get warmer due to the ozone layer. Ozone is an insulator & traps heat.\n\nAs you move higher, you will reach the mesosphere. And, as you may have already guessed, this layer contains even less air. It also gets pretty darn cold as you move away from the ozone layer. "Shooting stars" occur in this layer. Meteorites burn up as they enter our atmosphere.\n\nThe last layer is called the thermosphere. It has the least amount of air. But the odd thing is that this is the hottest layer!!!\n\nSounds strange??? Well here is why...\n\nAlthough there is less air to hold heat, there is still some present. Mind you, it is few & far between. Imagine being in the Astrodome & someone across the field threw a BB at you! That is how sparse the air particles are.\n\nHowever, we have said there is air! That air that is present is constantly bombarded with nasty cosmic rays! By this time, here is so much energy in the air particles that the temperature is astronomical (no pun intended).\n\nBecause of this, the thermosphere is often called the "heat sphere", just as it's name implies.\n\nSatellites are put into orbit in the thermosphere.\n\nTo get directly to your question... there are different layers because scientists decided to name them according to temperature changes.
659288
are you asking for second layer from the bottom or form the top.\nFrom the bottom it is stratosphere, whichi houses the ozone layer. Many jet aircrafts fly in this layer because it is veru stable.\nFrom the top, it is the thermosphere. Auroras take place in this layer. It is also where the space shuttle orbits. It is also the layer in which space shuttles orbit.
990446
It's true that there isn't much air up high to hold heat and pass it on to you. But you'd be surprised at how short a distance you have to go to feel a big difference in temperature. Mountains that are only several thousand feet tall have permanent ice caps. The heat from the sun goes straight through the atmosphere. Much of the UV and other radiations are filtered but the longer waves go straight through until they get stopped and absorbed by the ground. The majority of the heat is then reflected back up from the ground to fill a very small layer. Try going to the top of a very tall building on a hot day, the temperature change should be noticeable there too.
1038313
Earth...It has plenty of Atmosphere, Might have a little Co2 in it but, just plain oxygen.
309151
Most of Earth's water condensed out of its early atmosphere, and that atmosphere came from world-wide volcanic eruptions. So, ultimately Earth's water resulted from volcanic activity, although much of it also comes from comets that entered our atmosphere.\n\nGod should be spelled B-I-G B-A-N-G\nPBrax@netscape.com
945520
The Earth's primitive atmosphere was much different from today's and consisted primarily of ammonia, methane, and trace amounts of carbon dioxide and water vapor.  There was little, if any, free oxygen present.
1147540
Like all matter, the atmosphere is heated by the suns light.  When light is absorbed by the earth (the ground, the ocean, etc.) it is heated up (it's molecules move around faster) The air that makes up the atmosphere then absorbs some of the heat that is emitted by the earth.  When the air absorbs heat from the earth, this cools the earth.
654750
No its not necessarily closer to the sun(visit usgs.org) and even if its closer, it may be closer by 0.000001%.What big difference does that make.Its the difference in air pressure that makes the peaks colder.The higher you go up in the earth's atmosphere,the pressure decreases.And even an object 90% closer to the sun may not be that hot.
1118601
sky is nothing but made up of gases . as gases rise uo they all collect above
43014
No. The Earth's moon is terrestrial, meaning it has a rocky surface.