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

    Delta-v to overcome atmospheric and gravity drag at 13km?

    Wikipedia says that: Atmospheric and gravity drag associated with [space] launch typically adds 1.3 to 1.8 km/s to the launch vehicle delta-v required to reach normal LEO orbital velocity of around 7.8 km/s (28,080 km/h). Does anyone know, or know how to calculate/estimate/simulate the delta-v...
  2. K

    Some Thoughts on Atmospheric Systems

    Atmospheric sciences are—much like the sister science of astronomy—primarily observational sciences and not primarily experimental sciences. The atmospheric systems that we study are not well-defined systems under controlled conditions, but ill-defined systems under completely uncontrolled...
  3. DaveC426913

    Newest exoplanet close enough to study its potential atmosphere

    GJ 1132b, the new neighbour is a rocky, Earth-sized planet that's located only 39 light-years away - so lcose we could almost hit it with a rock. http://www.sciencealert.com/the-closest-earth-like-exoplanet-so-far-has-been-discovered-and-it-s-got-astronomers-excited?perpetual=yes&limitstart=1
  4. R

    Space Travel to Mars: Overcoming Atmosphere & Creating a Bus Stop in Space

    So off to Mars we go. But really how are we going to get there? The most expensive part of space travel is overcoming atmosphere. So you could say the biggest obstacle of space travel is Earth travel. It takes virtually no energy to cross space but it takes massive amounts to get into space...
  5. S

    Why does the heat in the atmosphere mostly go down?

    The wiki article on the greenhouse effect (https://en.wikipedia.org/wiki/Greenhouse_effect) has a top illustration which shows the flow of heat and energy (Watts per meter squared) between outer space, the atmosphere, and Earth's surface. The illustrations shows that of the 519 in the...
  6. A

    Why Do Aerial Images of Earth Appear Blue Despite Equal RGB Scattering?

    It is common knowledge that the scattering of blue photons by the atmosphere is more significant than for other colors hence aerial images of Earth look bluesh. The graph below obtained from MODTRAN 'allegedly' supports this fact. While trying to quantify this effect, I've preformed several...
  7. A

    Color of sky based on atmosphere density

    If the atmosphere was thiner would the sky be violet?, and if it was thicker would it be red?
  8. praveena

    About atmosphere light absorbtion

    Hi pf, I am having a basic doubt.Even this may be a silly question.sorry for that.While in the morning due to sun's light we can able to see our atmosphere and also clouds.But at night even when we foccused a large amount of light towards the space. why can we able to see the atmosphere...
  9. Mnemonic

    Law of Refraction with changing index of refraction

    Homework Statement A light ray enters the atmosphere of the Earth and descends vertically to the surface a distance h = 101.2-km below. The index of refraction where the light enters the atmosphere is n = 1.00 and it increases linearly with distance to a value of n= 1.000293 at the Earth's...
  10. S

    How much does weight affect re-entry into the atmosphere?

    Sorry if this is a dumb question. How much of an impact does weight have on reentry? I know it's extremely important on lift off due to fuel costs but is it any different on reentry? Are there certain trajectories calculated for different weights?
  11. DaveC426913

    How Does Atmospheric Pressure Impact Rocket Nozzle Design and Performance?

    This is perhaps a somewhat naive question about rocket exhaust. If I understand correctly, one of the challenges in designing a rocket nozzle - say, the main thrusters for the Saturn V - is that it needs to operate efficiently at sea level as well as at altitude. The difference in air pressure...
  12. S

    Can planting trees really reduce CO2 in atmosphere?

    From mycology books and articles, I read that most land plants (> 80 percent) on Earth live in symbiosis with mycorrhizal fungi. In this symbiosis, plants provide glucose to fungi and fungi provide water and nutrients to the plants. Without fungi, plants cannot harvest nutrients in sufficient...
  13. N

    Does the Moon's Gravity Affect Atmospheric Tides?

    [Mentor's Note: Post moved to it's own thread] I there a tidal swell or circulatory effect in the atmosphere caused by the moons gravity ?
  14. I

    Earth's Rotation and Atmosphere

    How does the atmosphere rotate with the Earth on its axis? There are no forces acting on it that would be strong enough to keep it moving with the ground. Gravity acts perpendicular to the direction of rotation, so it would not be able to cause this motion. It would only be able to keep the...
  15. bland

    What would the atmosphere do if the Earth were to vanish

    If the Earth were to vanish. Like the thought experiment that posits the sun suddenly disappearing to explain the 8 minute delay in the effect on the Earth, so I posit the Earth from the surface down vanishing in equally metaphysical and mysterious circumstances in order to help me to see what...
  16. 1977ub

    Guidelines for including "atmosphere" in a body's "diameter"

    When we see an official description of Pluto's "diameter" it is given without the atmosphere. The official diameters of the gas giants seem to include many layers of gaseous atmosphere. Is this difference merely a convention? Or is there a good reason for treating e.g. Pluto differently than...
  17. J

    Could a planet's atmosphere produce flares?

    < Mentor Note -- thread moved to General Physics from the Earth forum for better views > I put this in Earth Science because it pertains to atmospheric physics, astronomy might be more appropriate. I'm enrolled to take an advanced magnetism course this upcoming semester and I've been looking...
  18. kyle Bacon

    Does the atmosphere cool with altitude due to gravity?

    I read an article a day or so ago titled Hydrostatic Lapse, which makes the case for a phenomenon that I thought was well and truly confirmed; that gravity is responsible for the cooling of air with altitude. However I discover in the sequel article The Gemini Cycle that this phenomenon is...
  19. Kior

    Why is there a seasonal cycle of CO2？

    I am preparing my AOSS class next semester, and I found it is interesting that there is a seasonal cycle of CO2. I looked for some information on the Internet, and this seems to do with the plants. They awake in the spring and summer, absorbing a lot of CO2 by photosynthesis and die in the...
  20. tanmay

    Why is air pressure force not considered while weighing?

    we know that air pressure on our Earth is 1 atm. Also 1 atm = 10^5 P Also we know Pressure(P) equation = P = F/A So, F = P*A So if small area(A) in which we are standing is also taken then pressure force is that area(A) times 10^5(Atmospheric pressure in Pascal) i.e 10^5*A So why don't we...
  21. S

    How to change the earth's atmosphere to chlorine based?

    Hi, I'm working on a commissioned story, the basic jist of it is aliens colonize earth, begin a lengthy process of terraforming it to fit their toxic homeworld atmosphere. I read somewhere chlorine is the most viable alternative to oxygen in terms of energy production and it's fairly common in...
  22. Keith

    A question about heat transfer in our atmosphere

    So I've been wondering this for a couple days now: Is radiation the only means for decreasing the internal energy of our atmosphere? I know that in kinetic theory the molecules are similar to bouncy balls and if they were in contact with the vacuum of space, the air molecules would have no...
  23. 1

    How fast do we have to go if Earth had no atmosphere?

    how fast do we have to go if Earth had no atmosphere? i'm wondering why don't they send a small, but extremely fast projectile in front of the rocket, which heats and expands the air in front which reduces most of the friction? (maybe like a railgun?) does that not reduce the cost? or am i...
  24. E

    How to know the shape of a specific location on Earth?

    How do you know the shape (land altitude, roughness, etc.) of a specific location on Earth through a satellite? For example, if a specific place is covered by clouds is there a way to know the shape of the ground at this specific point? I have read through the absorption spectra of the...
  25. G

    How would music sound in a different atmosphere?

    I guess that the way we experience sounds on Earth is very importantly influenced by the composition and density of our atmosphere, since it determines how a pressure wave will be formed and will propagate. Does music sound appreciably different when heard at very high altitudes with low air...
  26. T

    Can I Reach the End of a Rainbow with a Shovel?

    I'm interested in rainbows. I'm talking about good old fashioned arc/halo rainbows like those you see in the sky. Sometimes you see rainbows from lawn sprinklers. How small would the smallest rainbow arc conceivably possible to view be? Could I make a rainbow at night using a sprinkler with a...
  27. T

    Can you see the atmosphere with you eyes or only through photos? (In space)

    Among my favorite space photos are those in which you can see the Earth's, or other planets atmosphere, and I've always wondered if this was something like you can't see a galaxy with the naked eye, unless you use really long exposure times in your photos?
  28. F

    Muons reaching Earth's surface problem

    Question: Muons created in the upper atmosphere are sometimes able to reach the Earth's surface. Imagine that one such muon travels the 60km from the upper atmosphere to the ground (in the Earth's frame) in one muon half-life of 1.52us (in the muon's frame). How thick is that part of the Earth's...
  29. G

    Mph jet engine reaches 2 atmosphere 29.4 psi

    As a jet engine travels through the sky and picks up speed ram air increases the air pressure at the air intalk of the engine. How many mph does the engine have to be going for ram air to 2 atmospheres = 29.4 psi? At what speed in mph = 3 atmospheres? 4 atmospheres? Is this a linear or...
  30. A

    Applying the ideal gas law in the Earth's atmosphere

    Hi there, I'm considering how the ideal gas law applies in practice in our planet's atmosphere. In particular, I'm considering this form of the law: P = ρRT (1) where P is pressure, ρ is density, R is the gas constant and T is the temperature. I also know that, to a good approximation, the...
  31. Z

    How the atmosphere pressure is generated

    Dear friends: The pressure is generated by the molecular collision or the weight of the air.?
  32. S

    Could the Hadean Era's Volcanic Outgassing Block Out the Stars?

    If you were standing on the Earth during the HAdean era, would the outgassing of volcanoes prevent you from seeing the stars? Would the atmosphere be transparent; what about moving into the Archean Era?
  33. C

    Consequences of denser atmosphere on Earth-like planet

    I made a brain storming, but hope that someone would be able to point out what I may have missed out. Assumptions - atmospheric pressure is 3 atm, but molar concentration of oxygen is comparable to earth. The rest is mostly nitrogen. (there are a few more assumptions like tidal lock, a bit lower...
  34. C

    Dense exoplanet atmosphere, choice zeppelin vs. plane

    Would on a exoplanet with dense atmosphere zeppelin/blimp better idea than a plane? If I get it right there would be: -much higher buyancy (argument for zeppelin) -higher drag (argument against plane) -higher lift (argument for plane) (but I'm not good enough to know what would matter)...
  35. 2

    Finding the pressure at a given height?

    I am having trouble trying to derive the air pressure at a given height. So far, I have considered a 1m^2 patch of area, and the pressure is the weight of all of the air above this patch. So P= \int_R^{\infty}g(x)\rho(x)dx So P= GM\int_R^{\infty}\frac{1}{x^2}\rho(x)dx But then I don't know...
  36. S

    Gravity -- Does gravity depends on atmosphere?

    Does gravity depends on atmosphere
  37. C

    Planet with dense neon atmosphere and streams of CO2

    Idea is a cold planet with dense atmosphere (10 atm) where human can survive, while a liquid carbon dioxide would be possible. As the main component of atmosphere I think about neon, because it should not cause nitrogen narcosis: http://en.wikipedia.org/wiki/Nitrogen_narcosis#Causes...
  38. adoion

    Pressure cooker at 1 atmosphere?

    Hi, I just read that the operating pressure of a standard pressure cooker is 15 psi or about 1 bar and they claim that water boils at 120C or 250F at this pressure. But atmospheric pressure is 1 bar in Paris and almost 1 bar in most countries in the world, here is a link I found...
  39. A

    How to Calculate Energy for Atmospheric Molecule Reaction and Isolate Gases?

    The atmosphere consists of two toxic, and unfortunately abundant gases in our atmosphere. Carbon dioxide and methane. Carbon dioxide produced by factories are not needed in the atmosphere and cause harm. So is methane. Acegikmoqsuwy and I thought of an equation to solve this problem: CH4 + CO2...
  40. D

    Escaping earth's atmosphere with a balloon

    Hi all, So my question is, could you use a weather balloon to assist with escaping the atmosphere and attaching a rocket to take it the rest of the way, and we're talking a really small payload obviously. Would the weight of the fuel/rocket weigh down the balloon enough to significantly...
  41. Spinnor

    Animation Shows One Year of CO2 Swirling Through the Atmosphere

    From NASA, a year in the life of Earth's CO2, at, http://www.wired.com/2014/11/nature-run-co2-visualization/
  42. C

    How Much Hydrogen Is Needed for a Balloon to Float at 10km Altitude?

    Homework Statement At an altitude of about 10 km, the temperature of the Earth’s atmosphere is roughly -50°C and the air pressure is around 16 kPa. (Assume ideal gas) How many kilograms of hydrogen gas (H2, molecular mass 2g/mol) should be put in a balloon to fill it to 2000 m3?What is the...
  43. Khatti

    Carbon Extraction from the atmosphere

    I sort of wandered in from the Science Fiction Forum before anyone could stop me. I have a thought that I simply lack the expertise to make use of, and I thought I would drop it in the laps of people who do have the expertise to make use of it. What would be involved to pull carbon directly...
  44. W

    Can a planet with a thin atmosphere have oceans?

    Let's say their is a Earth sized planet orbiting a sun like star in its habitable zone. This planet has a tilt and rotation rate similar to Earth. The planet however has an atmosphere of 0.1 bar. The planet orbits its star close enough to have an average temperature of 12 C. From what I...
  45. T

    Volumetric flow rate through a pipe vented to atmosphere

    My chemical engineering is a little rusty after 25 years and I could use a little help with this real world problem. This isn't my project but I've been asked to advise. Sorry for the limited information. We have a 30 gallon tank with 75% hydrogen/25% nitrogen mixture at 100 psig. From the...
  46. blintaro

    Density of Earth's atmosphere w.r.t height

    Homework Statement "It's possible to use the ideal gas law to show that the density of the Earth's atmosphere decreases exponentially with height, that is ρ=ρ0exp(-z/z0) where z is the height above sea level, ρ0 is the density at sea level and z0 is called the "scale height" of the...
  47. C

    Oxygen atmosphere without ozone layer

    OK, so I would like the following idea: -planet which already had its Great Oxygenation Event and life forms including human beings would be able to breath there freely -no oxygen layer or any other plausible mechanism which would practically preclude any daily life forms on the surface (all...
  48. M

    Bernoulli's theorem of conservation in a nozzle spraying to atmosphere

    Hi there, I'm having a problem behind the theory of bernoulli's theorem. Can it be applied in an application where water flows from a pump into a pipe with x diameter and out of a nozzle with y diameter to atmosphere. There is a pressure gauge on said pipe. There is a nozzle screwed into this...
  49. A

    Exploring Sunlight in the Atmosphere: IR Wavelengths

    Can anyone speak on the spectrum of sunlight reaching the upper atmosphere and the surface ? Specifically I interested in finding out if there are any IR wavelengths disproportionally represented when compared to the original source. Please limit responses to constructive ones.
  50. J

    Find the mean number density of particles in the stellar atmosphere.

    Homework Statement The atmosphere of a star has a mean radiation pressure of 0.33 N m-2and a mean gas pressure of 8300 N m-2. Calculate: a) the mean number density of particles in the stellar atmosphere, and b) the radiation pressure in a stellar atmosphere with twice the effective...
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