All Questions
1,323 questions
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 ...
117
votes
4
answers
11k
views
Why do clouds have well-defined boundaries?
Why do cumulus clouds have well defined boundaries? In other words, what are the physical mechanisms that hold a cloud together, as an entity separate from other clouds, that prevent it from spreading,...
- 65.1k
105
votes
6
answers
11k
views
Explain it to me like I'm a physics grad: Greenhouse Effect
What is the mechanism by which increasing $\rm CO_2$ (or other greenhouse gases) ends up increasing the temperature at (near) the surface of the Earth?
Mostly what I'm looking for is a big-picture ...
- 4,193
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
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
78
votes
6
answers
10k
views
How can we see planets thousands of light years away but don't know if there are more planets in the solar system?
That is basically my question, it arose when I saw an article (here is the scientific paper, which should be free to read) saying two Caltech scientists might have found the 9th planet of the solar ...
- 1,768
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
65
votes
3
answers
9k
views
Do sunrises and sunsets look the same in a still image?
A question that popped into my head: if I see a picture of the sun close to the horizon, in an unknown place, can I know if it was taken at sunset or sunrise?
Do sunrises and sunsets look the same in ...
- 633
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
51
votes
3
answers
3k
views
Are there tides in the atmosphere?
Analogous to the tides of Earths oceans, do the Moon and Sun cause our atmosphere to bulge in what could be described as a low and high tide?
- 6,065
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
49
votes
2
answers
8k
views
Cause for spikes in Trinity nuclear bomb test
In Richard Rhodes' book, The Making of the Atomic Bomb, I was reading about the Trinity nuclear test. High speed photos were taken and this one is from <1ms after the detonation. The book mentions ...
- 1,416
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
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
43
votes
2
answers
7k
views
Is our solar system really that odd?
I have been learning about the solar system from popular science shows. In these shows they suggest that, after having seeing around 2500 other solar systems, astronomers have concluded that our ...
- 1,430
41
votes
5
answers
11k
views
Why aren't rainbows more common?
Why are rainbows relatively rare? On any given day, there are billions of water drops in the air of varying sizes and dispersions, all of which light is passing through and refracting. What physical ...
- 517
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
39
votes
4
answers
7k
views
Why are rain clouds darker?
I was taught in school that clouds are white due to the scattering of light. Since all rays are reflected it appears as white. But I am wondering about rain clouds. Why are rain clouds darker?
user247360
37
votes
1
answer
4k
views
Nuclear bomb mushroom cloud with trumpet formation
I have found this specific image here (Loong found out that it is the Soviet Joe 4 test of the 400 kiloton RDS-6 warhead at the Semipalatinsk test site on August 12, 1953):
Also an impressive Youtube ...
- 2,020
36
votes
3
answers
16k
views
Why does the Earth cool at night time?
I do understand that open water and open ground cools by the means of convection — lower air takes the heat and goes up, where it cools.
But why does the Earth lose energy and where does it go? Does ...
- 481
35
votes
5
answers
11k
views
Why is the sky *uniformly* blue?
I've read a lot of answers to the questions why the sky is blue. However all the answers I found contain mostly qualitative analysis: Rayleigh scattering is changing the direction of blue light, so ...
- 469
34
votes
1
answer
906
views
Why are snowflakes flat?
There have been many questions and excellent answers in this community about the symmetry of snowflakes, e.g., here and here. There is however one aspect of snowflakes that does not seem clearly ...
- 65.1k
33
votes
1
answer
3k
views
Does more light from Andromeda get scattered in the atmosphere than in the entire trip to Earth?
Fires have been burning here in Northern California. Today there was just a slight haze of smoke. The sun had a slight red hue to it. As expected the lower it got the redder it became. The blue light ...
- 4,739
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
31
votes
3
answers
5k
views
Is a westward flying plane heavier than an eastward one?
I understand that you weigh less at the equator due to the increased centrifugal force. From my understanding, the faster you circle the Earth, the less your effective normal force you would feel, up ...
- 555
31
votes
2
answers
29k
views
Is there an upper frequency limit to ultrasound?
Wikipedia has this diagram of the acoustic frequency spectrum:
Is there an upper limit to the frequencies you can transmit through the air? Are they absorbed more and more at higher frequencies, ...
- 5,704
30
votes
4
answers
3k
views
What causes the direction of lightning flashes?
During a lightning strike, the flashes appear as cloud to ground or cloud to cloud. Why is this the only manner of propagation? Why do the flashes not go upwards from the clouds into the sky?
- 1,774
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?
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
28
votes
2
answers
2k
views
Why doesn't Earth's atmosphere form bands due to different rotational speeds?
If the Earth's atmosphere is rotating at the same speed as Earth, then the atmosphere must be rotating much faster at the equator than at the poles. If you spin a ball covered in oil, it will form ...
27
votes
3
answers
3k
views
Why are the northern lights so much less visible to the naked eye than to smartphone cameras?
The northern lights have been visible where I live recently, but I've found them to be practically impossible to see with the naked eye. Phone cameras, however, show them quite brilliantly. How is ...
- 1,289
27
votes
1
answer
557
views
What are these strange rays in the sky?
While driving, I noticed the sky had weird rays that appeared converge at some point on the horizon. I took a few pictures in hopes I could figure out what they were. There was a storm coming from ...
- 1,083
26
votes
6
answers
20k
views
If the pressure inside and outside a balloon balance, then why does air leave when it pops?
Sorry for the primitive question but when we inflate a rubber balloon and tie the end, its volume increases until its inner pressure equals atmospheric pressure.
But after that equality is obtained ...
- 421
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
26
votes
4
answers
3k
views
How do the “hot Jupiter” planets get so close to their host star?
Many of the extrasolar planets to date are Jovian sized planets that orbit very very close to their parent star. Traditional planetary formation models say that it is extremely unlikely (if not ...
- 6,467
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
26
votes
3
answers
4k
views
Why do the storms of Jupiter have long life unlike that of Earth?
Recently I saw How the Universe Works. In one of the episodes, concerning Jupiter, they told that the storms on Jupiter can survive many, many, times longer than those on Earth.
What is the reason ...
user36790
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
25
votes
4
answers
4k
views
Difference between sunrise and sunset?
Other than knowing which direction is east and which direction is west, or observing for a sufficient timespan (to determine the direction of motion), is there any way of telling whether what one is ...
- 456
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
24
votes
4
answers
1k
views
Why is lightning more rare during snow storms than rain storms?
Lightning and thunder during a snow storm is uncommon. As far as I know, more uncommon than during a typical rain storm. Why is this? I speculate it might be one, or both, of the following two ...
- 3,360
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
23
votes
2
answers
2k
views
How deep is the Great Red Spot?
The Great Red Spot (GRS) is a very persistent storm system that's easily visible through a telescope on the surface of Jupiter. But what is the three-dimensional structure of the GRS, and how deep ...
- 34.9k
22
votes
2
answers
10k
views
What is the scientific explanation for radio waves bending around the Earth?
The experiment
This experiment is documented in a documentary called Convex Earth. The exact location the following information is taken from starts at 14:25.
High frequency directional antennas are ...
- 331
22
votes
5
answers
3k
views
Why do X-ray telescopes have to be in space?
I have read this question:
For x-rays the (HUP limit) Δx becomes smaller than the distances between the lattice distances of atoms and molecules, and the photon will interact only if it meets them on ...
- 29.3k
22
votes
4
answers
4k
views
Why does moderately distant lightning sound the way it does: relatively quiet high pitched thunder first, and then much louder low pitched thunder?
Why does thunder, that is heard about five or ten seconds after the lightning is seen, start as relatively quiet high pitched 'crackling' thunder which is, about five or ten seconds later than that, ...
22
votes
2
answers
1k
views
Can rain evaporate?
Are there any atmospheric condition under which a visible raindrop can fail to hit the ground by evaporating first? I imagine this would require a large vertical temperature difference, and possibly ...
- 385
22
votes
2
answers
26k
views
Why doesn't the evening/morning sun feel much hotter on your face?
I understand that places on the Earth's surface get hotter in summer, and in the middle of the day rather than morning or evening, because the surface of the Earth is presented 'face-on' to the Sun at ...
- 325
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
21
votes
3
answers
944
views
Why is Jupiter so sharply defined?
In photographs of Jupiter, the limb seems extremely definite. Being a gas giant, my naive self thinks that the atmosphere should have a more gradual cut off, creating a hazy effect similar to that on ...
- 4,543