The atmosphere of Earth is the layer of gases, commonly known as air, retained by Earth's gravity, surrounding the planet Earth and forming its planetary atmosphere. The atmosphere of Earth protects life on Earth by creating pressure allowing for liquid water to exist on the Earth's surface, absorbing ultraviolet solar radiation, warming the surface through heat retention (greenhouse effect), and reducing temperature extremes between day and night (the diurnal temperature variation).
By volume, dry air contains 78.09% nitrogen, 20.95% oxygen, 0.93% argon, 0.04% carbon dioxide, and small amounts of other gases.
Air also contains a variable amount of water vapor, on average around 1% at sea level, and 0.4% over the entire atmosphere. Air composition, temperature, and atmospheric pressure vary with altitude, and air suitable for use in photosynthesis by terrestrial plants and breathing of terrestrial animals is found only in Earth's troposphere and in artificial atmospheres.
Earth's atmosphere has changed much since its formation as primarily a hydrogen atmosphere, and has changed dramatically on several occasions—for example, the Great Oxidation Event 2.4 billion years ago, greatly increased oxygen in the atmosphere from practically no oxygen to levels closer to present day. Humans have also contributed to significant changes in atmospheric composition through air pollution, especially since industrialisation, leading to rapid environmental change such as ozone depletion and global warming.
The atmosphere has a mass of about 5.15×1018 kg, three quarters of which is within about 11 km (6.8 mi; 36,000 ft) of the surface. The atmosphere becomes thinner and thinner with increasing altitude, with no definite boundary between the atmosphere and outer space. The Kármán line, at 100 km (62 mi), or 1.57% of Earth's radius, is often used as the border between the atmosphere and outer space. Atmospheric effects become noticeable during atmospheric reentry of spacecraft at an altitude of around 120 km (75 mi). Several layers can be distinguished in the atmosphere, based on characteristics such as temperature and composition.
The study of Earth's atmosphere and its processes is called atmospheric science (aerology), and includes multiple subfields, such as climatology and atmospheric physics. Early pioneers in the field include Léon Teisserenc de Bort and Richard Assmann. The study of historic atmosphere is called paleoclimatology.
Could not find reason on molecular level. E.g. here some explanation
"There are two reasons: at higher altitudes, there is less air pushing down from above, and gravity is weaker farther from Earth's center."
However, when I start to imagine particles, when there are only a few I get opposite...
I have come up with the change in height as 170 cm. My professor does not want to solve for the problem for a reason I do not understand. 170 cm is not part of the answer key. The answer according to the answer key is 65 cm.
My attempt is:
Initial temperature:
p=F/A; (50 *9.8) / (pi * 0.05^2)...
This is for a campervan project I am working on, I am trying to take outside air that is cold (Canadian winter) and mix it into the return air in my diesel heater. I need to hit a specific minimal CFM to maintain proper Co2 levels inside and I would like to be able to calculate this.
The axial...
My goal is to determine the ideal amount of air flow, in order to keep CO2 below 1000ppm and to minimize heat loss.
I calculated the following based off a similar post in this forum, and I am hoping this can be verified so I know that i am in the right ballpark and going in the right direction...
What would happen if you tried to fly through obstacles using warp drive? Distorting space so that two points are closer wouldn't get around the fact that there might be obstacles (e.g. air molecules, space dust, empire destroyers) that you would bump into along the way right. Would all of that...
I am doing a physics lab where we are supposed to calculate air resistance and find the impacts of velocity and cross sectional area on air resistance. For the experiment, we rolled a cart down a ramp and measured data using Pasco Capstone software. When rolling the cart down the ramp, we...
Speaking of the the oft-referenced adage 'Given sufficient (time akin to orders of mag greater than the age of the universe ) the probability of all air molecules randomly collecting on one side of a room, leaving the other in vacuum - while very remote - is not zero, .'
Is this not actually...
Recently I saw an exercise on electromagnetics (plane waves) in which it was said that a plane wave was traveling through vacuum (ε0 and μ0) BUT with losses, i.e, σ ≠0.
Is that possible?
I think I have read in the past that it's OK in some texbook, but now, I have searched for it in a couple of...
I want to compare diffusion of a tracer gas with a low exposure limit (e.g. isoflurane) to the advection of air by a ventilation system. When will diffusion exceed advection? I can't make sense of diffusion constant to compare transfer rates or velocities.
At room temperature the diffusion...
Both alpha and beta radiations can only travel short distances through air as they're not as penetrating as gamma radiations. How long gamma radiations with 22 MeV energy can travel in air? Is it meters, kilometers, miles, etc.
Is there a difference between a lower energy gamma ray and a higher...
Hello, this is an assigment form the 4th grade high school physics in Croatia, concerning electromagnetic waves.
Radio waves of wavelength 12m propagate from the source. The source is on the surface of the water and two waves propagate from it: one through the air and the other through the...
Hello everybody! I was wondering today if physically, it'd be possible for the world to develop an air conditioner without an outdoor heat unit? I know this seems to violate the second law of thermodynamics, but the known version of the second law thermodynamics only consider this is impossible...
I want the board to use air to lift itself of with the coanda effect which is when air sticks at the bottom of somthing and proppels it upwards along with specially designed heliblades.l and I want somthing to cover tge blades and make it safe and I want it be compact like back invite future or...
Hi all,
I've been trying to follow a question I came across on a website. And I'm able to understand everything up until the separation of variables for solving the differential equation and coming to a solution with arctan. But there are a few things that aren't explained that I was hoping...
This video talks about how air bearings can be made using porous materials like graphite.
Is it possible to get a comparable performance using non-porous materials, with an array of pin holes?
The video talks about how the carbon seat can be easily worked into conforming with the matching...
##4\pi\mathcal L = -\mathcal e \frac{\partial A_i }{\partial t} - \phi\mathcal E^i{}_{,i} -\frac{1}{2}N\gamma^{\frac{1}{2}}g_{ij}(\mathcal E^i \mathcal E^j +\mathcal B^i\mathcal B^j) +N^i [ijk]\mathcal E^i\mathcal B^j## MTW (21.100)
I'm trying to produce the result required by the problem...
I hope you guys don't mind a bizarre question from a novice. I've learned just enough about fluid dynamics to be dangerous.
Assume that we have a straight, rigid tube with a constant inner diameter. It's not long, let's say it's around a foot (in case that matters). We cut a chunk out of the...
2 scenarios:
1) Situation in the movie "2012", where volume of ocean water hasn't changed, but worldwide seismic activity has caused massive tidal waves. In one scene, a ship is sailing by Mt. Everest close to its peak. In such a scenario, I believe the air density outside the ship would the...
Hi,
I'm trying to solve this integral and then isolate V, but I can't get the right answer. I don't know where is my errors. I probably muffed the integral.
##-bv -cv² = m\frac {dv}{dt}##
##
\int_0^t dt = - m \int_{Vo}^v \frac {dv}{bv+cv^2}
##
I get this after the integration
##t =...
Hi,
A quick question on a conundrum I seem to have encountered. My main question is: why is it wrong to use the formula above instead of the SFEE approach?
My approach:
Use the formula:
$$ w = \frac{R}{1-n} (T_2 - T_1) $$
From the data book, ## R = 0.287 ## kJ/kg K and ## n = \gamma = 1.4 ##...
Please advise for cooling time on air conditioning.
I have a project and customer asked me to make a comparison between their requirement and my proposal. And here's the result.
Let's say that we provide a room with same capacity as above, function, delta T, load on that room, but ONLY air...
Hi guys,
I used to post on here quite a bit back in 2005-2007 when I was studying Physics in school, I remember it always being a great resource so hopefully I can get some similar help with this "real life" problem I'm having now!
We are having a mini-heatwave here in the UK the last few...
I am trying to understand an excerpt from an article describing the vibrations of a string (eg. guitar/piano) which reads as follows:
This is basically the wave equation with Δm representing a small piece of mass from an interval of the string and two forces added to the right side.
He...
I've just purchased a book of child scientific experiments and it has an experiment that is titled 'Weigh some air'. It shows that if you make a scales with a piece of wood and a pivot and then balance two empty balloons on a either end and then fill one of the balloons with air the scales will...
I am open to ideas of a way to test a bus bar for insulation flaws that has a 3D shape that varies in a production environment.
I have a DC bus bar that when it was just straight we would run a high potential test on a metal table that is the reference plane, and then flip it over to test the...
I used the form of the mean free path equation taking advantage of the fact that the Boltzmann constant is equal to the ideal gas constant R divided by Avogadro's number, because I didn't know if I could use the Boltzmann constant in the ##1.381\cdot 10^{-23}J/(molecules\cdot K)## form...
good day! I did not find a suitable forum thread, so I am writing here ... There is a valve through which you need to drive gas under a certain pressure, physically there is no way to drive gas, so it was decided to replace the gas with air. Knowing the required pressure and gas temperature, how...
I'm struggling with explanation of part 3. I don't know why they are using adiabatic equation while the gas is constantly heated by condensating vapour. While we are deriving adiabatic equation we use the fact, that there is no additional heat put into the system. Thank you in advance.
To reduce the transmission of coronavirus, people are recommended to stay 6 feet apart from others. The 6 feet number is a simple guideline, but there is not much difference between 5.9 and 6.0 feet.
How does the number of droplets you breathe from another person vary with the distance d? Is it...
I am going to be working on some calculations for an air surge tank to minimize fluctuations downstream of the tank in an engin'e intake syste, Any suggestions/sources where I could study for this?
Thank you!
The Blackbird wind powered car travels directly downwind faster than the wind speed powering it. Typically a 10 mph wind from directly behind it will cause it to travel at about 30mph.
I am trying to analyse how the car accelerates from rest. I know how it travels faster than the wind speed so...
Hi, I am looking for some guidance on how to approach this calculation. I have an air cylinder operating a lever assembly that then applies pressure to a pulley of which a belt is wrapped around. I need the belt to have about 4500 lbs of tension. How do I work backwards to figure the required...
Hey, first post here.
So I have to classify these 6 elements under closed-loop/open-loop system and under CO2 removal/oxygen supply.
I thought it should be:
Closed-loop CO2 removal: Rapid cycling anime, Lithium granules
Closed-loop oxygen supply: Water electrolysis, Cryogenic tanks
Open-loop CO2...
I have a problem. The task is to develop an differential equation of the airflow of a balloon. I know that it is dependent on the volume and pressure. But I can't get a good differential equasion. Can someone help me?
[Thread moved from the technical forums, so no Homework Help Template is shown]
Hello! I'm brand new to the physics forum so please excuse any mistakes I make. I'm not even sure if I'm in the right forum section lol.
My goal is to create a air cannon to launch a piece of dog food (super overkill) and I have pretty much 0 background in anything post-high school physics. I'm...
German V2 rocket engine burn was 70 seconds. Rocket speed about 4000 ft per second. Rocket launched straight up for 3 seconds then turned to a 42 degree angle. There is a lot of counterdicting information online about how high up V2 want and how far it flew but that is not the point. Engine...
1) Let X represent the number of tires with low air pressure on a randomly chosen car. The probability of distribution of X is as follows:
X 0 1 2 3 4
P(X) 0.1 0.2 0.4 0.2 0,1
a) Find the probability...
I have two filter materials and I have manufacturer-supplied pressure drops across the filters at given flow rates. I know the desired flow rate and the negative pressure "sucking" on the downstream side of the filter, and I want to calculate the required filter surface area for each filter...
First, I tried using the Archimedes principle and calculated the weight of the surrounding air displaced when taking off.
##W = 2500\times 1.29\times 9.81 = 31637.25 N##
But then, I got stuck and do not know how to proceed from here on.
I don't want the full solution yet but can I get some...
Good morning folks. I have a question about fresh air in an HVAC system. The explanation I provide are a bit tedious, but the question is eventually asked towards the bottom.
I am evaluating a negative air pressure room for a small medical laboratory. Using ASHRAE 170, I know this room needs to...
Hi,
I am trying to figure out the strength of the various type of airflow for my Venturi ejector device. Please refer to my diagram that illustrates scenario A or scenario B. The SAME amount of compressed air is injected for both scenario A and B. For simplicity, I have added to an electrical...
The object you place in the microwave warm up because of the electromagnetic waves. How come the atoms of the air of the microwave do not warm up? Or do they only feel like they haven't warmed up, or do they not absorb the energy as much as the object you place in the microwave?
Can you, please, help me with this exercise? I know the formulas for the required parameters, but I know neither how to use them here nor in what way to solve the exercise. Plus I don't understand what for I was given the temperature
Thank you for your help and advice
Hi all, I'm new on here and will start off with what I think is a simple clarification. I'm questioning my workings due to previous work being completed by another engineer and thought this was the best place to ask.
Essentially we have compressed air being supplied through a hose, the hose...