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. S

    I What is the thickness of the atmosphere?

    I was thinking of a Fermi-question: the thickness of atmosphere with diffusive equilibrium. And I estimated roughly 10^{5}m (where it should be ~10^{4}m). The difference of order of magnitude to real thickness is 1 (from Wiki). I had a lot of fun, and I am looking for interesting ways other...
  2. A

    Could a spacecraft refuel from the atmosphere?

    https://phys.org/news/2018-03-world-first-air-breathing-electric-thruster.html If it dipped into the atmosphere temporarily on an elliptical orbit, could the air gathered be stored for a long flight? Then maybe get more fuel from another planet's atmosphere or moon for the return trip?
  3. 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...
  4. 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...
  5. I

    Residence time of SO2 in the atmosphere

    Homework Statement Use the IPCC estimate of anthropogenic SO2 emissions of 55 ⋅ 109 kg/year and natural SO2 emissions of 15 ⋅ 109 kg/year to estimate the residence time of SO2 in the atmosphere. Is the residence time consistent with SO2 emissions being able to travel from Ohio to Maine as...
  6. Noisy Rhysling

    What would it take to ignite the atmosphere?

    The Los Alamos guys were laying bets on what would happen when the Trinity device went off. This ranged from "wet firecracker" to "igniting the atmosphere". (I've read ahead, it was something in between.) My question is, would it be possible to build an atomic bomb that could actually "ignite...
  7. yrjosmiel

    Why don't ion thrusters work within the atmosphere?

    So I was reading about ion propulsion when I read this: I understand the fact that drag will be too powerful for the ion thruster to overcome. However, why does it matter when there are foreign ions? Does the magnetic field of the grids pull ions from the atmosphere, thus pulling the entire...
  8. E

    How to pump liquid from vacuum to atmosphere

    Greetings, The application is a wiped film evaporator (~1.2-1.5 kg/hr throughput). The concentrate and the distillate gravity feed round bottom flasks. I'm not worried about the cold-trap waste. The evaporator volume is under vacuum (~0.003Torr). I want to pump the liquid from the...
  9. 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...
  10. J

    Ball bouncing on a planet (no atmosphere) follow up questions

    This thread will contain several follow up questions, but let me start with the most simple one. Imagine a planet with no atmosphere and a ball in empty space. The ball is dropped on the planet from a certain height and starts bouncing. We ignore friction and consider this to be the fully...
  11. Brunolem33

    B How Do Missiles Reenter Earth's Atmosphere?

    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...
  12. M

    Find the difference in pressure between each atmosphere

    Homework Statement There are two similar atmosphere ISA +30C and ISA tropical Maximum, they have identical: Mean Sea level conditions, same basic shape of temperature profile and same lapse rate in troposphere. The difference is the altitude of the tropopause and hence a different temperature...
  13. 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?
  14. J

    Can CO2 in the Earth's atmosphere sublimate into a solid?

    CO2 becomes a solid at -78.5 C or -109.3 F. The coldest temperature ever recorded on Earth was on Antarctica at -89.2 C or -128.6 F. So is it possible for CO2 to literally freeze out of Earth's atmosphere under certain conditions? If not then why not?
  15. Blank_Stare

    At what point does the atmosphere become space?

    A few years ago, a Australian guy jumped from a platform that was attached to a weather balloon, from roughly 24 miles or so in the atmosphere. News articles claimed he jumped "From the edge of space". https://en.wikipedia.org/wiki/Felix_Baumgartner But did he?, I mean clearly 24 miles is an...
  16. infinitebubble

    I Guarding Mars' atmosphere with a magnetic shield

    NASA scientists have proposed a magnetic shield that would sit at the L1 Lagrange Point beyond the planet, creating an artificial magnetosphere that would deflect solar winds and incoming radiation... Let's discuss thoughts and implications, engineering problems, etc. in such a formidable task...
  17. 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...
  18. A

    I Equalizing Pressure in Pipe for Safe Container Design

    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...
  19. pkt

    B Our atmosphere and the rotating Earth

    What force keeps our atmosphere spinning with the rotating earth? How can there ever be a calm day?
  20. P

    I Requirements for a breathable atmosphere

    Hello all, hope you had happy holidays and new year. I had some questions regarding atmospheres, breathable mostly and what conditions are required on a planet to sustain them. Could a low gravity planet with the temperature of Earth maintain a breathable atmosphere? Could it be given one...
  21. 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%...
  22. JCB123

    I Air flow from atmosphere into a tank

    Hi, I have a tank of air which has been depressurized to 0.2bar (absolute) via a vacuum pump, where air can be let in from atmosphere through pipework controlled by a valve. What would be the equation I can use to determine the flow rate into the tank with time? As the flow rate is determined by...
  23. 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...
  24. A

    Mass, Density and Volume of atmosphere

    Homework Statement : [/B] The density of the Earth's atmosphere varies with altitude, and can be approximated by an exponential: ρ(h)=ρ0e^(-h/h0) where ρ0 = 1.3 kg/m3 (the approximate density at sea level) and h0 = 8.2 km (this is determined empirically). Calculate the mass of 15 km of the...
  25. Geoffw

    Would a non radiative atmosphere be isothermal?

    Many credited physicists have entertained the notion of a non radiative atmosphere being isothermal as a function of height. But is this a physical reality? Many physicists accept the macroscopic conclusions of kinetic theory, the gas laws. Statistical mechanics. Experimentally verifiable...
  26. Sawdust7

    Surface speed of atmosphere and jet fuel

    The surface of the Earth is moving approx. 1000 miles per hour at the equator. Which means, excluding natural wind and especially hurricanes, the air is also moving about 1000 miles per hour along with the surface, or the central areas of the Earth would be stripped of just about...
  27. N

    Can UV Light be the Key to Changing Venus' Atmosphere?

    I thought a bit about the prospect of terraforming other worlds starting with the ones closest to us, Mars and Venus. Personally even though I don't mind the hype over Mars, I prefer thinking of Venus as the main target for terraforming. it's just a lot more tempting. for example: It's surface...
  28. Battlemage!

    B Albedo, atmosphere, and predicted temperature of Venus

    The reason I am making this thread is because I have a question regarding predicted temperatures of planets based on their area, distance from the sun, and albedo. Going by the planetary equilibrium temperature, T4 = [L(1-a)]/(16σπD2), I have seen numerous websites state that Venus would...
  29. Prasun-rick

    B Does Atmosphere Dilation Affect Sunlight Travel Time? | Explained

    Light from the sun takes about 8 mins to reach the earth. But does the time get delayed appreciably due to Earth's atmosphere?? Thanks in advance !
  30. P

    Why is there atmosphere at the equator?

    The bulge at the equator, which Wikipedia says is 42km, means that a point on the equator (at sea level) is 21 km further away from the centre of the Earth than the poles. That's two and a half Everests! I think that the difference in the force of gravity (gravity only) between the equator and...
  31. Narayanan KR

    I Poynting energy flow in Eath's atmosphere?

    1.There is an electric field between ionosphere and ground, also Earth's magnetic field is perpendicular to this E field, hence by poynting theorem integrating E x H across the entire surface of Earth gives a great deal of energy flowing west to east. 2. |S| = (E X B)/u0 = (150 V/m X...
  32. victorhugo

    I Light and our atmosphere (some quantum physics)

    I was looking at the moon rising and noticed that it starts off quite yellow/orange and gets more and more white as it reaches the middle of the sky. Why does it look bigger? I'd imagine it's something to do with refraction, but how exactly does it work? Does the moon look more orange closer to...
  33. slick_willy

    Why does atmosphere rotate w/ constant angular velocity?

    Hey guys. I've seen this question asked on a few different forums, and I understand the basic gist of the answer but I am not yet satisfied with what I have read. People seem to have varying degrees of understanding of this, and I am the type of person that wants to understand things 100% and...
  34. 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...
  35. A

    Can we lift water more than 10.3m using atmosphere pressure?

    I'm trying to design a solar heated (non electrical pump) ..but by theory when we are lifting water by using vacuum and atmospheric pressure the weight of water after rising 10.3 m is equal to the atmospheric pressure created by vacuum ,so they cancel out..so is it impossible to lift water using...
  36. F

    Fluid discharge from pipe to atmosphere

    Homework Statement I know that when the fluid flow from pipe to reservoir, the coefficient of discahrge is 1, where head loss =k(v^2)/2g... How about the fluid is discharged from pipe to atmosphere?? Homework EquationsThe Attempt at a Solution
  37. L

    Calculate where the top of the atmosphere would be.

    1. The weight of the atmosphere above 1 square meter of Earth's surface is about 100,000 N. Density, of course, decreases with altitude, but suppose the density of air were a constant 1.2 kg/m^3. Calculate where the top of the atmosphere would be. - weight = 100,000 N (or 10197.16 kg) - density...
  38. Hoophy

    Low Atmosphere Rocket Launch Stages Carry Their Own Oxygen -- Why?

    So I was wondering how come liquid rocket engines (operating in the lower atmosphere (such as launch stages)) are using Oxygen that they have packed on board. What I mean to say is why would the rocket need to waste space and mass bringing Oxygen with them in the launch stage when they could...
  39. F

    B How to contain an atmosphere in space?

    Ok this is an interesting idea I had today. Would it be possible and how to contain an atmosphere in space without gravity. Like some sort of plasma magnetic field. Not sure there is a real practical use for Themis other then studying asteroids without space suits.
  40. B

    B "Without Earth's atmosphere, cosmic rays would be lethal"

    In the episode Unafraid of the Dark in Neil deGrasse Tyson's series Cosmos, Tyson says the following: "Hess had discovered cosmic rays, showers of subatomic particles that crisscross the universe at nearly the speed of light. Without the shielding effect of the Earth's atmosphere, they would be...
  41. S

    I Boltzmann distribution: isothermal atmosphere error?

    There is a well-known analysis of the distribution of particles by height in an isothermal atmosphere. It states that the probability of finding a particle at height ##h## is ##p(h) \propto e^{-\beta mgh}##, and then goes on to state that the number of particles at height ##h## is ##n(h) \propto...
  42. B

    Could a planet have liquid water without an atmosphere?

    I once knew both how atmospheres formed on planets and how oceans of liquid water formed on planets, but I have forgotten that information. I know that both atmospheres and oceans of liquid water formed due to chemical reactions, but I used to know more of the details of what type of matters...
  43. EliotBry

    What is the total mass of the atmosphere?

    Homework Statement Problem from the book "Engines, Energy and Entropy", Page 55, question 7 has me stumped. It doesn't feel like their is sufficient information to work out the mass of the air. They've given us density (as seen in the picture, if the upload works) , which is mass over volume...
  44. P

    I How does gravity hold onto the atmosphere

    Gravity seems emense in strength of objects with large mass. So how does the Earth hold on to air molecules
  45. S

    A Solar drive / neutron atmosphere

    I am wondering, if the sun is a fusion reactor, it should have an "atmosphere" of neutrons ? So presumably a craft with suitable fuel eg boron or uranium, in a close pass, would be able to use that to react with the fuel in a suitable drive ? Probably not good for humans - (!) but for an...
  46. 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...
  47. Stephanus

    Atmosphere Layer: Gases Buoyancy & Wind Effects

    Dear PF Forum, Our atmosphere consist of 78% N2, 21% O2, 0.9% Argon, and other... https://en.wikipedia.org/wiki/Atmosphere_of_Earth 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...
  48. 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...
  49. 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...
  50. 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
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