Atmosphere Definition and 34 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. Lotto

    What is an atmosphere comparable to Earth's atmosphere?

    Does it mean that the atmosphere is made of the same atoms and molecules like our atmosphere and that it has the same spheres such as trophosphere? And that the temperatures in these spheres are also the same or very similar like here? And are distances between these spheres the same like here...
  2. Isopod

    B Could anything heat back up the core of Mars?

    My understanding of why Mars lost its atmosphere was because it cooled down too much internally and that when this happened, the planet lost its magnetic field that helped protect it from solar winds (which then ended up stripping away the planets atmosphere). Is there anything that people could...
  3. Algr

    Terraforming the Pre-Earth? (Algol's video)

    I find this video absolutely amazing, and have watched it over a dozen times now. It helps if you can use the spacebar to pause it and read the text, and arrow keys to back up 5 seconds. - This is NOT phone friendly! Big monitor and 1440p recommended. So two different questions for...
  4. J

    A Is this evidence that Venus originally had a nitrogen atmosphere?

    Has MESSENGER found evidence that Venus originally had a nitrogen atmosphere, and might have been more habitable, and the present amount of CO2 was released by some cataclysm afterwards?
  5. Fabrizio Vassallo

    What is the composition of the Earth's exosphere?

    Hello! My name is Fabrizio, I'm a high school student doing some research on the atmosphere. Right now, I'm trying to figure out how much matter escapes into space via Jean's Escape. I've found several formulas, all of which require me to know what the amount of particles per m3 of a certain...
  6. K

    Pressure Difference Between the Inside and Outside of a Balloon

    Hello all. I have a question about gasses and pressure: Is there a way to calculate how strong a material making up a balloon has to be to withstand a given pressure difference between the inside and outside? In other words, if I have a balloon I need to fill to a pressure of 10atm inside vs...
  7. D

    Misc. Hydrostatics problem in a water vessel

    I am trying to design a water vessel system that maintains it's water level as it is consumed. In item 1. It's a simple water barometer, where the height of water in the column can be supported by atmospheric pressure until 10.34. In item 2. There are two columns that are open to atmosphere...
  8. K

    Atmospheric Refraction

    Does atmospheric refraction only work at certain temperatures, distances, and shape of the object (i.e. only spheres)?
  9. P

    Future of the Atmosphere W/Unregulated Pollution?

    In a future (100, 500, and 1000 years in the future specifically) where industrial and domestic pollution is totally unregulated, what does the composition of the atmosphere look like? And what do weather systems look like? I know this is an extremely broad question, I'm just looking for a few...
  10. I

    Continuous Grey Atmosphere Model

    Homework Statement In the grey atmosphere radiative energy balance model, we replace the multi-layer approximation used above with still simplified but significantly more realistic model involving a continuous atmosphere with a continuously varying temperature. The variation with temperature is...
  11. hilbert2

    Flame in a background atmosphere of fuel

    In combustion science, typical flames that are studied are premixed or diffusion flames, where a stream of methane, propane or some other fuel is released to an atmosphere of air or oxygen and ignited. Another scenario is a "pool fire", where a puddle of volatile solvent is burning in air and...
  12. J

    Brightness temperature in remote sensing

    Hi all, I don't know if I'm on the right forum to ask this, but maybe somebody knows anything about brightness temperatures measured by remote sensing devices. In a paper that I read "Atmospheric corrections for retrieving ground brightness temperature at commonly-used passive microwave...
  13. Brunolem33

    B Missile reentry

    A couple of days ago, there was this beautiful ballistic missile launched from North Korea. While reading about this momentous event, I was surprised to learn that said missile had climbed over 2,000 km before crashing into the sea some 700 km from its launchpad. Since this missile flew into...
  14. K

    How to calculate sound speed in atmosphere?

    Hello. Just wondering how to calculate the sound speed in the atmosphere if I have temperature and pressure from the surface and all the way up to thermosphere?
  15. sistruguru

    Relative Humidity (RH) affecting atmospheric attenuation of light?

    Ok, so I have another question that online searches have not been able to produce. Everything I've seen online references sound waves, or RF signals, or electromagnetic waves. I know that the reason we can view sunsets and sunrises safely is because of atmospheric attenuation - the amount of...
  16. A

    I Time to equalization

    Hi, I have a pipe that is unpressurized initially at atm internally with air. Inside the pipe there is a welded container that is vented at the top. The vent is made to have air pass through so that the internal pressure of the container eventually equals the pressure of the internal pressure of...
  17. I

    Expressing concentrations as a percent

    You measure the concentration of O2 in seawater to be 5.0 mg O2/L H2O. Express this concentration as a percent. Question 2: The Earth's atmosphere contains 21% O2/L of air. How much more oxygen does the atmosphere hold than seawater from the previous question? So for question one I got 0.01%...
  18. B

    Amateur author seeking help on attacking ozone layer

    Hi, I'm looking for plausible fiction based content regarding environmental destruction. Sort of future UV wars or something. So here goes. Would appreciate any ideas or feedback on what I've come up with so far. Several dissidents build 12ft mirrored parabolic dishes which shine narrow focussed...
  19. Ravi Singh choudhary

    Why atmospheric pressure does not crush us?

    1atm is typically something 101.13 kPa that means 100kN force is acting on 1 square meter surface area of our body. How we are capable for taking such high pressure? Sometime I think on 1 square cm area what immense force they are creating. I feel something is wrong with my concept of...
  20. A

    Why do vacuum and the air behave so similarly ?

    I may be in the dark here but many of the media-dependent constants like permeability, permittivity and even the speed of light are ALMOST identical in both media ie. vacuum and the atmosphere of the Earth. This exists even though the 2 are very different because one is almost empty and the...
  21. Stephanus

    Atmosphere layer

    Dear PF Forum, Our atmosphere consist of 78% N2, 21% O2, 0.9% Argon, and other... What about theses gases? Will they form a layer like this liquid because of their buoyancy difference? Or they will be scattered evenly because of the wind. I...
  22. 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...
  23. 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...
  24. R

    Space Travel to mars

    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...
  25. 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...
  26. 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...
  27. 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...
  28. 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...
  29. 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...
  30. 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...
  31. T

    Questions about rainbows

    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...
  32. 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...
  33. 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...
  34. A

    Atmospheric Molecule Reaction

    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...