All Questions
209 questions
103
votes
7
answers
113k
views
Why does the atmosphere rotate along with the earth?
I was reading somewhere about a really cheap way of travelling: using balloons to get ourselves away from the surface of the earth. The idea held that because the earth rotates, we should be able to ...
- 7,463
14
votes
1
answer
8k
views
At what altitude would the air be too thin to carry a sound wave?
A related question When does an aerobraking space craft create a sonic boom? has spawned a couple of answers, but so far no compelling answers.
It is a common belief that in space there is no sound,...
- 292
50
votes
5
answers
15k
views
Why does the sky change color? Why is the sky blue during the day, red during sunrise/set and black during the night?
Why does the sky change color? Why is the sky blue during the day, red during sunrise/set and black during the night?
user68
5
votes
1
answer
3k
views
Can a hovering helicopter travel half the globe in 12 hours? [duplicate]
Suppose we have a helicopter that is able to stay stationary in flight for extended periods of time. If such a helicopter stayed at point A in the sky for 12 hours straight, would it reach the other ...
- 161
83
votes
3
answers
64k
views
Why is the sky not purple?
I realise the question of why this sky is blue is considered reasonably often here, one way or another. You can take that knowledge as given. What I'm wondering is, given that the spectrum of ...
- 9,785
73
votes
6
answers
50k
views
Why is the sky never green? It can be blue or orange, and green is in between!
I, like everybody I suppose, have read the explanations why the colour of the sky is blue:
... the two most common types of matter present in the atmosphere are
gaseous nitrogen and oxygen. These ...
user59485
20
votes
2
answers
3k
views
What is the safe distance to a supernova explosion?
In other words, what stars near the Sun may have an impact on the Solar system equilibrium or the Earth life if they become supernova ? Is SN 1987 A too far ?
user46925
28
votes
5
answers
63k
views
Why less temperature at high altitude?
Why there is always cold at high altitudes. e.g. at peak of mountains. Also as we go high from sea level, temperature starts decreasing. Why is it?
26
votes
4
answers
17k
views
The Density of Clouds
Clouds are made up of tiny water or ice droplets, depending on temperature. This implies that cloud density is greater than that of dry air. Why don't clouds sink through their surrounding atmosphere ...
- 5,812
41
votes
2
answers
19k
views
Why is the sun brighter in Australia compared to parts of Asia?
Background:
I've lived in Philippines for several years, and visited other parts of Asia occasionally (Singapore, Indonesia, Hongkong).
I just moved to Western Australia a few months ago and I ...
- 863
26
votes
5
answers
177k
views
Why does the road look like it's wet on hot days?
Often, I'll be driving down the road on a summer day, and as I look ahead toward the horizon, I notice that the road looks like there's a puddle of water on it, or that it was somehow wet. Of course, ...
- 3,439
16
votes
4
answers
39k
views
How does carbon dioxide or water vapour absorb thermal infra red radiation from the sun?
We are all told at school water vapour and carbon dioxide are the top two greenhouse gases, and that they absorb thermal infra red radiation, trap heat and warm up the Earth. My question is how do ...
- 307
137
votes
15
answers
41k
views
Is the butterfly effect real?
Is the butterfly effect real? It is a well-known statement that a butterfly, by flapping her wings in a slightly different way, can cause a hurricane somewhere else in the world that wouldn't occur if ...
12
votes
4
answers
2k
views
A water pipe from sea level to beyond the atmosphere
If a pipe extended from just above the ocean floor to outside the atmosphere, would water be sucked up it by the vacuum beyond the atmosphere? If a hole was made in the pipe, above sea level, how ...
- 137
10
votes
3
answers
5k
views
Why does air remain a mixture?
As we all know, air consists of many gases including oxygen and carbon dioxide. I found that carbon dioxide is heavier than O2. Does the volume difference neglect the mass difference? Is it same for ...
1
vote
1
answer
2k
views
Would a pipe from the surface to the Earth's exosphere suck all atmosphere to the space? [closed]
If I built a tube from Earth's surface to the exosphere, would all the air be sucked out to space?
If this pipe reached to a big planet, like Jupiter, would its gravity through the pipe suck our ...
- 121
25
votes
12
answers
13k
views
Why do spacecrafts take off with rockets instead of just ascending like an aircraft until they reach space?
I guess it's not a very educated question, but I never quite understood why spacecrafts have to shoot up and can't just reach space by simply continuing an upwards ascent like an airplane.
- 251
48
votes
9
answers
21k
views
Why is air not sucked off the Earth?
People said outside earth is a vacuum. But the air does not get sucked from the Earth's surface. Some said it is due to gravity and some said the speed of air molecules are not high enough to escape....
- 609
23
votes
5
answers
25k
views
Can helium disappear from Earth?
Helium is lighter than air, so it should fly off from Earth.
Is it possible that in the future we will run out helium?
- 863
18
votes
2
answers
13k
views
What is the temperature of the clear night sky from the surface of Earth?
Before you all jump in with 2.73 K or thereabouts, this is more of an experimental question. It will obviously depend on humidity and radiation being scattered back towards the surface of the Earth. ...
user56903
16
votes
1
answer
1k
views
Why doesn't the percentage of oxygen in Earth's atmosphere diminish significantly with altitude?
According to numerous sources online, the percentage of oxygen is approximately the same at sea level and 10,000 meters. Since oxygen is heavier than nitrogen, shouldn't the percentage of oxygen ...
- 53.7k
6
votes
2
answers
3k
views
Why is the sky blue and the sun yellow?
The blue color of light of the sky is due to Rayleigh scattering.
But the sun itself appears yellow in color whereas the scattered sunlight itself appears blue.
Why does this happen?
Should the sun ...
- 454
5
votes
2
answers
4k
views
Why is the atmosphere transparent in the visible spectrum?
One of the great 'coincidences' in physics is that the Sun happens to shine most brightly at exactly the wavelengths our eyes can see; it's an easy explanation that our eyes evolved to make the most ...
- 135k
2
votes
1
answer
274
views
Invariant Concentration of Ideal Gas Mixture with Altitude
Consider the following scenario, We have two gasses, $A$ and $B$, both approximately ideal mixed together in a gravitational field of constant magnitude $g$. Let them have masses per particle of $m_a$ ...
- 620
55
votes
4
answers
18k
views
Why doesn't hydrogen gas exist in Earth's atmosphere?
The root mean square velocity of hydrogen gas at room temperature is:
Gas constant: $R=8.31\ \mathrm{J\ K^{-1}\ mol^{-1}}$
Molar mass of hydrogen gas: $M=2.02\times10^{-3}\ \mathrm{kg/mol}$
$$\begin{...
- 579
14
votes
10
answers
28k
views
How come gas molecules don't settle down?
If the earth's gravity exerts a net downward gravitational force on all air molecules, how come the molecules don't eventually lose their momentum and all settle down? How is the atmosphere is still ...
- 1,927
13
votes
1
answer
3k
views
From how high could have Felix Baumgartner jumped without disintegrating like a shooting star?
Today Felix Baumgartner jumped from 39 kilometres high and reached the earth safely.
Just considering friction, from how high can a human jump?
I expect that from a certain height, he would have ...
- 231
12
votes
3
answers
967
views
Extended sound of thunder
Why does the sound of thunder last several seconds even when lightning lasts for only fraction of a second?
- 977
11
votes
3
answers
4k
views
Why does the air pressure at the surface of the earth exactly equal the weight of the entire air column above it
Why does the air pressure at the surface of the earth (resulting from collisions of molecules on the surface of the earth which has to do with the velocity of the particles) exactly equal the weight ...
- 113
9
votes
3
answers
27k
views
Atmospheric pressure experiment using a cup with a fluid to hold a glass plate
When I was in high school, my teacher did an experiment to show the power of atmospheric pressure.
Experiment:
Prepare a glass bottle, fill with water, put a glass plate on the bottle, make sure ...
- 93
8
votes
1
answer
688
views
What are the properties of a sonic shock wave?
An aircraft travelling faster than sound creates a shockwave.
How dense is the air in this shockwave, and how thick is the shockwave?
Is this a range or a definite number? I realize the shockwave ...
- 6,082
6
votes
2
answers
2k
views
How would the Aurora light on Earth look like if there wasn't a magnetic field?
Here are some pictures of the aurora light.
The beautiful phenomenon of Aurora is a well-known one, seen in the northern (Aurora Borealis) and southern parts (Aurora Australis) of the globe. Here is ...
2
votes
3
answers
6k
views
Why the pressure of atmosphere doesn't crush you when you e.g. walk outside?
Why the pressure of atmosphere doesn't crush you when you e.g. walk outside? I mean the density of air is $1.26 kg/m^3$, so with $100 km$ above us, it exerts much pressure on you when you walk outside....
- 735
32
votes
1
answer
3k
views
Using nuclear devices to terraform Mars: Elon Musk's nuclear proposal? [closed]
Elon Musk has recently suggested Using nuclear devices to terraform Mars. In the past, comet related ideas were mooted, but Musk seems, to me anyway, to be a man in a hurry and perhaps his idea has ...
user81619
28
votes
3
answers
7k
views
Why doesn't rain fall down in streams (as opposed to drops)
Why is it that raindrops don't collide and 'stick together' on their descent to Earth, arriving in streams rather than separate drops?
- 473
25
votes
1
answer
1k
views
Causes of hexagonal shape of Saturn's jet stream
NASA has just shown a more detailed picture of the hexagonal vortex/storm on Saturn:
http://www.ibtimes.com/nasa-releases-images-saturns-hexagon-mega-storm-may-have-been-swirling-centuries-1496218
...
- 181k
21
votes
4
answers
45k
views
How is Earth protected from the gamma rays generated by the Sun?
The Sun is generating energy by nuclear fusion. This nuclear fusion will emit energy in the form of gamma rays.
Normally, the earth's ozone layer filters the ultraviolet radiation while the earth's ...
- 694
16
votes
4
answers
17k
views
Can open, unsafe nuclear fusion reaction burn the atmosphere?
I happened to hear people saying that the nuclear fusion bomb tests could set the atmosphere on fire. I have some serious doubts about that - but I have no facts.
Nuclear fusion reaction requires $15*...
- 3,107
5
votes
3
answers
2k
views
Rayleigh equation as explanation for sky being blue
I've been reading up on the internet as to why the sky is blue. The answer usually cites Rayleigh scattering that I've checked on wikipedia: https://en.wikipedia.org/wiki/Rayleigh_scattering:
$$
I=...
- 151
5
votes
2
answers
7k
views
Why does the Sun turn red near sunset?
At daytime the Sun's light is yellowish if not near white. Why when the Sun starts to go down that it's light turn more red. I don't think the earth's rotation is so rapid to cause a red shift.
Why ...
- 347
4
votes
1
answer
445
views
Do atmospheric physics prevent hot air balloons from ascending over 60,000ft?
I was reading the altitude records for hot air balloons on Wikipedia, and noted that the max hot air balloon altitude was about 60,000ft. It didn't really say if there was a reason why. I know that ...
- 271
1
vote
3
answers
394
views
What is the reason of $dT/dh = 0$ in the gas column?
According to thermodynamics every adiabatic system and (with no external energy added) will reach thermodynamic equilibrium or an ergodic state (2 law of thermodynamics entropy can not decrease in a ...
- 158
1
vote
2
answers
385
views
Scattering of blue wavelength and red wavelength in our atmosphere
I've read the reason sky appears blue is because blue wavelength is being scattered by the gas molecules, dust particles etc. Thus, because of this scattering, we are basically being bombarded with ...
- 453
43
votes
10
answers
32k
views
Why can't we see gases?
I am not sure what causes gas molecules to be invisible.This question may look silly but I really want to know the story behind it.
- 1,653
22
votes
2
answers
7k
views
Why does my infrared thermometer say the sky is at -2 °C?
I just got myself an infrared thermometer. I wouldn't have been able to predict what temperature it would give me when pointing at the sky, but it turned out to be -2 °C the first time I measured, and ...
- 9,444
18
votes
9
answers
6k
views
Why does atmospheric pressure act on us?
I have a bit of misconception about weight which I want to clarify.
The air pressure is explained as the weight of the air column above our head acting per unit area. But since air is not continuous ...
user238497
17
votes
3
answers
2k
views
Why is there a "blue hour" after the "golden hour"?
There's a great story about why the sky is blue during the day, and turns golden during sunsets:
Rayleigh scattering affects blue light more. During the day, blue light from the Sun is scattered ...
- 105k
17
votes
1
answer
11k
views
Why does the composition of the air does not change with altitude? [duplicate]
Air contains about 78% nitrogen and 21% oxygen independent of altitude (up to 100 km). Why is this? Shouldn't the concentration of nitrogen increase with higher altitudes since nitrogen has a lower ...
- 833
15
votes
2
answers
3k
views
Only sea water appears blue in color, why this is not happening in river water?
Is the salt in the water the reason for scattering sunlight into blue?
- 191
15
votes
5
answers
19k
views
Why do lightning rods have a sharp point at the top?
We know that a lightning rod or lightning conductor is a metal rod or metallic object mounted on top of an elevated structure and, if we look closely, most of them have a sharp point at the top. What ...
- 1,850