What is Atmosphere: Definition and 404 Discussions

An atmosphere (from the greek words ἀτμός (atmos), meaning 'vapour', and σφαῖρα (sphaira), meaning 'ball' or 'sphere') is a layer or a set of layers of gases surrounding a planet or other material body, that is held in place by the gravity of that body. An atmosphere is more likely to be retained if the gravity it is subject to is high and the temperature of the atmosphere is low.
The atmosphere of Earth is composed of nitrogen (about 78%), oxygen (about 21%), argon (about 0.9%), carbon dioxide (0.04%) and other gases in trace amounts. Oxygen is used by most organisms for respiration; nitrogen is fixed by bacteria and lightning to produce ammonia used in the construction of nucleotides and amino acids; and carbon dioxide is used by plants, algae and cyanobacteria for photosynthesis. The atmosphere helps to protect living organisms from genetic damage by solar ultraviolet radiation, solar wind and cosmic rays. The current composition of the Earth's atmosphere is the product of billions of years of biochemical modification of the paleoatmosphere by living organisms.
A stellar atmosphere is the outer region of a star and typically includes the portion above the opaque photosphere. Stars with sufficiently low temperatures may have outer atmospheres with compound molecules.

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  1. C

    Why did Earth lose its first atmosphere but keep its second?

    I'm trying to get a basic understanding of Earth's origins in order to teach an advanced oceanography course to high school students this summer. The course starts with one lecture on the origins of the universe, solar system, the earth, and the ocean. Why did Earth lose its first atmosphere...
  2. S

    Mass of the earth's atmosphere given the density as a function of h

    Homework Statement An exponential model for the density of the earth’s atmosphere says that if the temperature of the atmosphere were constant, then the density of the atmosphere as a function of height, h (in meters), above the surface of the Earth would be given by δ(h) = 1.28e(−0.000124h)...
  3. A

    Atmosphere Modeling: If G Doubles, How Tall?

    If g (acceleration due to gravity) was double on Earth, how tall would our atmosphere be?
  4. O

    Why don't nearby atmosphere look blue.

    Hi all We know white sun light consist of seven colours and that when it passes through the atmosphere then due atmosphere it scatters. Amount of scattering is more for shorter wavelengths( maximum for voilet). Due to multiple scattering the effect of voilet scattering washes away and blue...
  5. W

    Can a Mercury sized moon support an atmosphere?

    Lets say there is a gas giant similar to Jupiter orbiting a yellow star similar to our Sun. The planet and moon orbit at a distance that would resemble in between Mars and Earth. So the moon would receive 70% the sunlight that Earth receives. Around this planet exists a moon with 0.064 Earth...
  6. E

    Forming of our Galaxies or Atmosphere

    Hello dear people, I'm Evrim, 18 years old, from the Netherlands. Dear people, I am this time things investigating about science. I'm almost done with my questions, Really it will be good and u make me than happy if u can help me. - Dear people was during or after the formation of ranges of...
  7. T

    Titan's atmosphere vs temperature.

    I was wondering at what temperature would Titan's atmospheric particles reach escape velocity? Since Titan lacks the mass to hold onto its present atmosphere then would I be wrong to conclude that what holds such a thick atmosphere is the extremely low temperatures found on Titan?
  8. W

    Would the sky be red if the atmosphere was thicker?

    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?
  9. marellasunny

    Earth's shadow in the atmosphere

    If a clear view is available of the horizon,theory says that I'll be able to view the Earth's shadow(the curvature of the Earth in the direction of sunlight). Is it possible to calculate the curvature of the Earth just by looking at this different colored band in the horizon? Was it done...
  10. C

    How Is the Temperature of an Asteroid Between Mars and Jupiter Calculated?

    Homework Statement What should be the temperature of a spherical asteroid located between Mars and Jupiter, twice as far from the Sun as Earth? The asteroid has no atmosphere and its albedo is .15. Homework Equations The Attempt at a Solution The asteroid is twice as far from...
  11. R

    Estimate temperature of Saturn's atmosphere

    Homework Statement To estimate the temperature of the Saturn' atmosphere? (We need to use rotational spectra of CO)Homework Equations B=\frac{h}{8\pi^2 I C} cm^{-1} The Attempt at a Solution I calculated the rotational constant B of CO. I don't know how to proceed further.
  12. D

    Using energy to scrub the atmosphere of greenhouse gases

    I was wondering if someone could help me with the current and foreseeable technology to use Earth's energy (nuclear, hydro, etc.) to actually scrub the atmosphere of CO2 and other gases. I'm curious if this is even possible and how it might be done. I've been trolling the internet for this...
  13. H

    Heat in Atmosphere: Why are Mountains Nearer to Sun?

    Heat is more in ground than in mountains. Why? Mountains are nearer to sun,then what happens? Thanks!
  14. J

    Does anything travel at speed c in the atmosphere.

    I understand the electromagnetic spectrum travels below speed c in Earth’s atmosphere. Is there any part of the spectrum which remains at speed c, or indeed anything which travels at speed c in the atmosphere? Thanks
  15. W

    If Earths atmosphere were thicker?

    What would Earth be like if the atmosphere was twice as thick at 2 bar? How would it affect the daily and seasonal variation in temperature and weather? How would it have affected life in general and if we grew up in this environment how would we be different?
  16. T

    Why doesn't a barometer with vacuum get crushed by the atmosphere?

    Why doesn't a mercury barometer containing vacuum get crushed by the atomospheric pressure? Here is what I think might be the reason. Although there is vacuum inside a mercury barometer, that vacuum is pressurized by the atmosphere that pushes mercury from the reservoir. That pressure is...
  17. A

    How much water is in the atmosphere?

    At any given moment do scientists have an idea of how much water is in the atmosphere? Can we compare it to how much fresh water is stored on Earth as a liquid?
  18. Crazymechanic

    Ball lightning atmosphere interaction

    There are numerous threads here about ball lightning but I am not exactly sure have any of those addressed this issue? Now a ball lightning even though haven't been duplicated in the lab is most likely a some sort of sphere or form of a plasma or ionized gas that has to do with charges and...
  19. jhae2.718

    Lunar Atmosphere Dust Environment Explorer

    LADEE, the Lunar Atmosphere Dust Environment Explorer, is set to launch tomorrow from NASA Wallops Flight Facility on an Orbital Sciences Minotaur V launch vehicle. It's a neat mission with some good science on it. Launch is scheduled for tomorrow, Sept. 6, and will be shown on NASA TV...
  20. G

    Have we ever sent anything into the atmosphere of the gas giants?

    I've often heard there's no solid ground in the gas giants, but do we know this for a fact or are we just guessing based off the math?
  21. micromass

    Physics Challenge II: Bouncing out of the atmosphere

    Part 1: Consider ##n## balls ##B_1##, ##B_2##, ..., ##B_n## having masses ##m_1##, ..., ##m_n##, such that ##m_1\ll m_2\ll ...\ll m_n##. The ##n## balls are stacked above each other. The bottom of ##B_1## is a height ##h## above the ground, and the bottom ##B_n## is a height ##\ell## above the...
  22. U

    How can I explain that the Atmosphere will burn?

    Dear Phyisics Forum, I registered here in hope to find some help as I plan a videogame and really have to solve some "small" idea I have. More likely a way how to explain it. In basic I want to explain how a Nuclear Explosion ("regular" Nuke with uranium, i guess) can cause a chain reaction...
  23. nealshireman

    What happens to heavy atoms that come into the atmosphere as cosmic

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  24. N

    Measuring the electrical conductivity of the atmosphere

    I am trying to devise a way to test the electrical conductivity/resistivity of the atmosphere through rising altitudes. The platform for the experiment is a NASA weather balloon with the allowance of a 1 kg payload. I have started by creating a sort of leaky capacitor design which involves the...
  25. Q

    Can Atmosphere exist in Moon Craters?

    Hi, consider a Moon Crater hidden from direct sunlight that has an average temperature about -60 Celcius (213 K). It is quite possible that somewhere on the Moon such crater exists. I choose -60 Celsius because it is the average Winter temperature at the South Pole and thus possible lowest...
  26. P

    Is 11 km/s Velocity Enough to Escape Earth's Atmosphere?

    hi all, me and my friend were arguing today. We read that a cricket ball requires 11 km/s to leave the atmosphere. Now not taking friction/drag into account would this velocity be sufficent for any mass to leave the earth. Thanks.
  27. P

    Does Urine Absorb Atoms from the Air and Create a Vacuum in a Closed Container?

    I have been urinating into a plastic bottle lately (I will not elaborate why), and have been finding the bottle to hold a vacuum the following morning. What I find strange is that even without temperature fluctuations, my bottle produces a vacuum after several hours of being left alone. It is in...
  28. M

    How quickly would Mars loose its atmosphere?

    Besides low gravity and high doses of radiation, one of the more intractable difficulties in terraforming Mars is that if we build its atmosphere back up, then presumably it would lose it again via the same mechanisms it lost it the first time (ie solar wind, warmth, and low gravity)...
  29. D

    Radiative Transfer Parallel Plane Atmosphere Help

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  30. A

    Replicate atmosphere of Earth, scaled down for experimenting

    I would like to analyse the effects of passing a laser/microwave through the Earth's atmosphere, in relation to space-based solar power. As I can't do my experiment on the real scale. I would like to know if it's possible to scale it down. I.e. replicating the relative amounts of gas at...
  31. B

    Statistical Mechanics: particle density of an atmosphere

    Homework Statement I am supposed use stat mech to find the particle density in Earth's atmosphere given only the particle mass, and temperature, and the planet's mass I guess. And I don't really know where to begin. Obviously I need to use the grand canonical ensemble but I don't know where to...
  32. E

    What if there were no atmosphere

    What would be the effect on day night period if there were no atmosphere? I mean would the days become longer or shorter? Why?PS:Admims,Trust me its not my homework...
  33. Avi Nandi

    Thermodynamics: work done when a gas is leaking into atmosphere

    I have a gas container which contains gas at high pressure. The gas container is fitted with a capillary tube which opens into the atmosphere. Now we have a stopcock fitted to the capillary tube. We opens the stop cock slightly and allows the gas to leak outside. The process will go on till the...
  34. C

    What sort of atmosphere could a rogue planet have?

    Let's say that a planet of approximately Earth's size - containing, as Earth does, core heat - were tossed out of orbit. Could it maintain any sort of atmosphere, or would all the component gases liquify and freeze, or be gradually lost to space? If it could retain any atmosphere, what gaseous...
  35. Y

    Concentration and diffusion of oxygen in the Earth's atmosphere

    Homework Statement 1. Estimate the concentration of oxygen in the Earth's atmosphere (in molecules / m^3), at room temperature and at sea-level, assuming the fact that oxygen comprises 21 percent of the Earth's atmosphere by volume. 2. If you were to place a perfect oxygen sensor of...
  36. J

    Why does an asteriod burn up in the atmosphere but a space shuttle wont?

    Is it because the speed at which the asteroid is coming in greatly increases the friction between it and the air molecules in the atmosphere?
  37. S

    Why does air pressure decrease with altitude?

    At ground level, the air pressure measured with a barometer is 1000 mb. The barometer is lifted upward by a weather balloon. When the balloon reaches 2 km above the ground, the measured air pressure is 800 mb. Explain why the air pressure decreased. After the balloon goes up another 2 km (now 4...
  38. H

    Gravity in the upper atmosphere

    Homework Statement See attachment Homework Equations Centripetal acceleration Mv^2/r The Attempt at a Solution I guess the answer to be D But I am not quite sure about the same rate of acceleration. If we hypothetically remove the space station and visualize the astronaut orbiting around...
  39. S

    Atmosphere pressure from gravitation

    Hello, can I calculate the pression of the atmosphere at a certain height using the gravitational law ? thank you
  40. H

    Why does the atmosphere get colder with elevation?

    ~50 years ago, Richard P. Feynman asserted that the reason the atmosphere is colder at higher elevation is because "The ground is heated by the sun, and the re-radiation of heat to the sky comes from water vapor high in the atmosphere; so at high altitudes the air is cold--very cold--whereas...
  41. M

    Atmosphere model approximation limits

    I am modelling the atmosphere as a perfect, static gas subject to uniform gravity, assuming ideal gas equation, the density is found to follow: p=A*exp(-z/H) where A is a const, z is the heigh, and L is the scale height. I want to know when this approximation breaks down! at what density? i am...
  42. T

    Calculate the speed of the rock as it enters Earth's atmosphere

    Homework Statement In Robert Heinlein's The Moon is a Harsh Mistress, the colonial inhabitants of the moon threaten to launch rocks down onto Earth if they are not given independence (or at least representation). Assuming that a gun could launch a rock of mass m at twice the lunar escape...
  43. mesa

    Checking Average Atoms in 1 m^3 of Atmosphere at STP

    So I need a check on my calculations for the average number of atoms in a 1 meter cube of atmosphere at STP. I came up with 88.14 mols, here is how I did it: First I calculated the average amu using percentage in air by Nitorgen 78.08% @ 14.007 amu Oxygen 20.95% @ 15.999 amu Argon...
  44. N

    Calculating the Mass of Earth's Atmosphere: What Assumptions Were Made?

    1.Atmospheric pressure is 101kPa a) Calculate the total force exerted by the atmosphere on the surface of the Earth. Radius of Earth is 6.4 Mm b)Calculate the mass of the Earth's atmosphere , State any assumptions made. P = F/A ρ = m/v [\b] [b]a) Surface area of a sphere is...
  45. M

    Speed of falling in atmosphere

    How to derive a formula for speed of falling body in Earth atmosphere? I know distance from surface, pressure at this distance, object mass, falling start point and point where I want to calculate the speed.
  46. M

    Does the Rate of Descent Affect Objects Burning Up in Earth's Atmosphere?

    Objects burn up entering Earth's atmosphere. If we were to float high enough wouldn't the same thing happen? Or does` the rate of descent play a role?
  47. J

    Martian atmosphere weight and gas constant

    Homework Statement Determine the mean molecular weight of the Martian atmosphere which is composed of 95% carbon dioxide, 3% nitrogen, 1.6% argon. What is the gas constant for 1kg of such an atmosphere? Using the value for R from the last problem assuming the surface temperature of Mars is...
  48. J

    Meteorology atmosphere temp question

    Homework Statement Could a liquid thermometer register a temperature of -273° C when the air temperature is actually 500° C ? Where would this happen in the atmosphere, and why ? The Attempt at a Solution I have no idea. If someone could just give some possible tips on what it may...
  49. J

    So why does the atmosphere block gamma rays but not UV rays?

    Or light rays for that matter. Where does the window open in the atmosphere on the em spectrum, UV? Why is that?
  50. W

    The moon and earths atmosphere

    I read somewhere that Earth's moon is a cause for Earth's relativly thin atmosphere, is that true. If so would that mean if the moon was smaller we would have a thicker atmosphere?
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