Atmosphere Definition and 407 Threads

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. T

    Earth's surface temp without atmosphere vs moon's

    Without an atmosphere, the Earth's average surface temperature would be -18 C. The moon's surface temperature averages -23 C. Is this 5 degree C difference due to heat from the Earth's core? (I'm not a student; I'm curious about the climate debate, and trying to figure some things...
  2. N

    Rayleigh scattering in Earth's atmosphere

    Does anyone know a rough ballpark figure for the opacity of the Earth's atmosphere in the visible? Assuming an observer is at sea level looking to the horizon, I calculated the opacity due to Rayleigh scattering in the visible band, as shown in the attachment. I don't really require a high...
  3. B

    What caused the disappearance of Mars's atmosphere and surface water?

    I hope someone can clear up some issues about Mars's atmosphere, specifically: -- Since most evidence indicates that Mars once had surface water, I assume that it must have had a considerably more substantial atmoshpere than it currently has. --- A magnetic field is necessary for the...
  4. Z

    Atmosphere, Pressure, & Weather

    A balloon can be filled with 5.0 L of "He" w/o bursting. The balloon is filled 0.5 L at a pressure of 1 atm. The balloon rises and the pressure gets lower. At what pressure will the balloon burst? I tried a few of the gas laws but I think my answers are incorrect. How do you solve this?
  5. B

    Moon slingshot powered atmosphere scoop?

    Here is the scheme: A craft from Earth slingshots around the moon back towards the earth, gaining some speed (and slowing the moons orbit slightly). a few days later it expends this energy skimming the Earth's atmosphere, scooping some atmosphere into its tanks. It heads back towards the moon...
  6. P

    Earth's Atmospry: Heavier Elements, N2, O2, CO2, H2O

    The heavier elements tend to be found near Earth's surface than the lighter ones. However the most widely found element is N2 but elements like CO2 and O2 are other heavy ones so more near the Earth's surface? What about water? Is water mostly near Earth's surface or way above? If way above, is...
  7. P

    Recognition of 'Sublimation of Atmosphere'

    I want to know how we will recognize when our CO2 PPM is approaching 'Pre-Sat'/Sublimation of our atmosphere. I'm thinking if we recognize that our oceans are dying(blue green aglae and phytoplakton dying off), and some species that pollinate our flowers(bumble bees and honey bees) are going...
  8. C

    Why Doesn't Earth Lose Atmosphere Over Time?

    Why doesn't the Earth lose it's atmosphere eventually? I realize that gravity generally keeps the atmosphere close to the Earth but over a long period of time I would expect that we would lose some amount to the vacuum of space and the solor winds. Over millions of years we would lose it all...
  9. Loren Booda

    Will a changing atmosphere host a burgeoning ecosystem of microbes?

    Would global warming (with its dynamic weather systems, carbon surplus, increased radiation and humidity, etc.) encourage the vitality, diversity and interaction of unicellular life in the atmosphere?
  10. A

    Number Density in the Atmosphere

    Assume that the Earth's atmosphere has a uniform temperature of 20ºC and uniform composition, with an effective molar mass of 28.9 g/mol. a) show that the number density of molecules depends on height according to: nv (y) = (n0) e^ -(mgy)/kBT b) commercial jetliners typically cruise at an...
  11. L

    Re-Entry into Earth's Atmosphere: Understanding Space Ship Speed

    How Does a Space Ship reenter the Earth's atmosphere at such a great rate of speed? I understand speed in this way W=F x D. there is nothing in space for the ship to propel itself off to build this great speed.
  12. M

    Early Earth Atmosphere: Could Earth Have Had a Denser Air?

    If Mars used to have a denser atmosphere in the past, could Earth have had one as well?
  13. Z

    Escape Speed and Atmospheric Temperatures of Planets: Calculations and Analysis

    a) Show that the escape speed for a particle to leave the gravitational infuence of a planet is given by (2GM/R)^1/2, where M is the mass of the planet, R is its radius, and G is the gravitational constant. b) The temperature near the top of Jupiter's multicolored cloud layer is about 140K. The...
  14. M

    Does Heat Truly Get Trapped in the Earth's Atmosphere?

    Here is my theory: Once heat radiation enters our atmosphere from the sun and gets absorbed by the material inside, it is emmitted back as conduction/convection. In order for this heat to travel it needs a medium such as air. Now isn't it true that once this heat reaches the border between...
  15. E

    Aerodynamics - Standard Atmosphere problem

    Here's the problem: We are ascending in an elevator at sea level. Our eardrums feel a 1 percent decrease in pressure per minute. Calculate the upward speed of the elevator. My solution: *I am using the equation p1/p0 = (T1/T0)^(-g/aR), where p1 and p0 are pressure at point 1 and point 0...
  16. A

    Jupiter's Atmosphere: Questions & Answers

    once i looked at short video clip of Jupiter atmosphere. i have questions in mind: 1. why the atmosphere seems to travel at different speed making up a number of sliding rings?why don't they travel together? 2. what makes the pattern of turbulence so huge? i think we need such an incredible...
  17. quasar987

    Measuring the potential of the atmosphere

    In lecture 9 of the second volume of the Feynman Lectures on physics, it is written... How can we measure [the field in the air above the ground] if the field is changed by putting something there? There are several ways. One way is to place an insulated conductor at some distance above the...
  18. Z

    Imagine to be Pluto's surface, climate and atmosphere?

    Hi there. I have two questions to make. First how do you imagine to be Pluto's surface, climate and atmosphere? And second how much time does the sun light to reach Pluto? Please answer, i really want to know about these two things. Thank you.
  19. D

    Effects of different atmosphere on evolution

    I am a science fiction writer and I need some help with developing a plausible alien species. The species has to end up technologically advanced. What would be the effect on a species that evolved on a world with 74% nitrogen and 25% oxygen (other gases remaining similar to Earth)? Thanks for...
  20. H

    Taking energy from the atmosphere

    Our atmosphere is continously being heated and energized by the sun. Has anyone ever actually developed an engine able to take this energy directly from the atmosphere or if not, why nobody was able yet to make one?
  21. U

    Why Can Gas Molecules Escape the Atmosphere Despite Low Average Speeds?

    I'm reading in my physics book that: "A rule of thumb used by astrohysicists is that a gas will escape from a planet's atmosphere in 10^8 years if the average speed of its molecules is 1/6th of the escape velocity." they said this statement without any derivatins and I was windering why...
  22. S

    Chemical asorb sun energy?high CO2 in atmosphere

    good day to everyone, i wish to ask what chemical in our environment asorb some energy from sun? and what it has to do with high C02 level in the atmosphere? thanks in advance
  23. S

    Calculating Total Mass of 14CO2 in Atmosphere

    (a) If galactic cosmic rays produce 75 gm of ^{14} C per year in Earth’s atmosphere, the ^{14} C [/itex] resides in the atmosphere as 14CO2 and the radioactive decay half life of ^{14} C is 5730 years, calculate the total mass of ^{14} CO2 in the atmosphere. ok the half life equation is...
  24. M

    Is Slow Travel Through Earth's Atmosphere Possible?

    If you find a way to acctually travel (defining gravity of course) slowly like 20 MPH as you enter the Earth's atmosphere from space would you burn up? Is burning up just an effect because of the speed ships are coming in? Or, even if you were traveling at 10 MPH through the atmosphere would the...
  25. R

    Heat of objects entering an atmosphere?

    Does a planet's atmosphere effect how hot objects get when entering its atmosphere? If we had two exact space shuttles entering two different planets, the first planet is Earth while the other is significantly smaller planet but its atmosphere is predominately made of carbon dioxide. Both are...
  26. A

    Astronauts Jump So High on Moon: Weight and Atmosphere Matter

    Astronauts on the Moon can jump so high because 1) they weigh less there than they do on Earth. 2) their mass is less there than it is on Earth 3) there is no atmosphere on the Moon I believe the correct answer is 1, because they weigh less. Choice 2 has got to be wrong since mass...
  27. P

    Accummulation of Gases in the Atmosphere

    I was reading that helium does not accummulate in the Earth's atmosphere due to the fact (a claim) that it is too light to be retained by gravity and diffuses out into space. Does anyone know the physics that prevent the atmosphere seeking the vacuum at whooshing out into space. Is there a...
  28. R

    How Is the Mass of Earth's Atmosphere Calculated?

    What is the mass of the Earth's atmosphere? The radius of the Earth is 6.4E6m. The only thing I can think of is to subtract something from the mass of the entire Earth or something...
  29. S

    What would be the color of the sea without an atmosphere?

    what will be the colour appearance of the sea on earth?
  30. loseyourname

    Muon-Catalyzed Fusion in the Upper Atmosphere

    All right, you're going to have to really humor me here. As far as I know, the only kind of 'cold' fusion that has ever been demonstrated to work is muon-catalyzed. The reason it isn't viable is that is takes so much energy in the first place to create muons and they have a very short...
  31. C

    Fireworksdamaging our atmosphere?

    Is there any damaging effect or chemical that gets released into our atmosphere? I know wildfire and deforestation is a problem, but what else? Also, sorry if I post on wrong place, I was stuck in between Chemistry, and Biology. =/
  32. P

    How much does the Earths Atmosphere weigh?

    How much does the Earths Atmosphere weigh? Also let us know how to calculate that.
  33. S

    Earth's Atmosphere: Temperature, Pressure & Density FAQs

    I am searching for graphs to answer te following questions but I cannot find it on the internet. What is the temperature, density ,and pressure of the atmosphere as altitude changes? What is the temperature of the thermosphere at night?
  34. G

    Calculating Total Mass of Nitrogen in Atmosphere

    Hi. Can someone give me a hint to how to calculate total mass of nitrogen in the atmosphere. I've calculated the mass of all the atmosphere, I got the percent by volume of nitrogen to be 78.03 %. I converted the mass of the atmosphere to Liters. I got the volume of nitrogen to be 3.18e21 L and...
  35. E

    Create Artificial Atmosphere: Pros & Cons

    Should we create artificial frictional medium such as atmosphere ?
  36. dav2008

    Will the atmosphere run out of CO2?

    I watched a program on some public broadcast channel where a professor from a university detailed the possible ends of the earth. One of them (from what I recall) had to do with lowering CO2 levels in the distant future. The lack of CO2 would eventually kill off all plant life. I tried...
  37. quasar987

    Why does the atmosphere move with the earth?

    HallsofIvy wrote in another thread: Just yesterday I was asking myself that very same question. So thanks for giving such a nice an simple explanation. I was also wondering why the atmosphere revolves with the earth; something you stated but didn't explained. Is it something that goes...
  38. z-component

    What Would Happen If the Moon Entered Earth's Atmosphere?

    If the moon ever did enter our atmosphere, what would be the first thing that would happen? How would the two gravitational fields interact with each other?
  39. G

    Calculate Fractional Abundance of HI,HII,H- & e- for Hydrogen

    how can i calculate the fractional abundance of HI, HII, H- and e- for hydrogen in the photosphere (T=5770K) and density 10^17?
  40. D

    Atmosphere, Kinetic, related question.

    Hello all, I have a relative simple question, but I'd like to double check with you folks. Typically, in normal atmosphere the kinetic energy of water molecules in water, should be lower than the kinetic energy of water molecule in hot vapor, isn't that right? Thank you! /cheers!
  41. ?

    Atmosphere can be absorbed into the solution?

    when cooling a solution, if the container is open, is it possible that some water from the atmosphere can be absorbed into the solution? and if so, can there be a significant amount of absorbance (i.e enough to alter some properties of the solution) ? I'm trying to explain some results i got...
  42. M

    Anyone know how much xenon is in our atmosphere?

    anyone know how much xenon is in our atmosphere? This is where we get it right?
  43. G

    How far does a gamma beam go in the atmosphere?

    Hi, can someone tell me the extinction coefficient of a gamma ray in the atmosphere? How far does a gamma beam go in the atmosphere before its intensity reduces to half or to 1/e?
  44. L

    Space as a vacuum and earth's atmosphere

    Awesome web site, but its mostly over my head... with my physics expirence limited to high school. I have always wondered this... if space is a vacuum... and gasses in a vacuum tend to ... uh... for a lack of a vocabulary... de-concentrate... disperse... what causes Earth's gases to stay...
  45. P

    What Substances Exist in the Atmosphere of Our Galaxy?

    Would you please tell me what is in there ? I mean what substances are existing ? Where can i find out some information about this ? Thank you very much,
  46. T

    Life on Earth Without the Atmosphere: What Would Happen?

    I was unsure of where to post this so that it would get attention. I am preparing a short lecutre about the Earth's atmosphere and I need to know the following(which I have not found answers to elsewhere): How would be experience standing on Earth without an atmosphere? Would we be totally...
  47. T

    Calculating Weight of 100lb Man on Earth & Atmosphere

    can someone tell me how i can calculate what the weight of a 100lb man (on the surface of the Earth) would be on different parts of the Earth: the core and at all the layers of the atmosphere thanks
  48. S

    Low orbits, if Earth did not have an atmosphere?

    If the Earth did not have an atmosphere could you make a golf ball orbit the Earth just 1 foot above the highest point of the crust of the Earth?
  49. S

    How Do Molecules Stay Distinct Between the Stratosphere and Troposphere?

    Hey I was just wondering if you know the height of the atmosphere, and the pressure that atmosphere creates on the Earth (1 atmosphere), then how would you approach calculating the number of molecules in the atmosphere? I was thinking of using the PV=NKT formula, where K is boltzmann's...
  50. D

    Finding the mass of the earth's atmosphere

    A barometer having a cross-sectional area of 1.00 cm^2 at sea level measures a pressure of 76.0 cm of mercury. The pressure exerted by this column of mercury is equal to the pressure exerted by all the air on 1 cm^2 of Earth's surface. Given that the density of mercury is 13.6 g/mL and the...
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