Score
Title
75
AskScience Panel of Scientists XVIII
252
AskScience AMA Series: "I am Rhett Allain, physicist and technical consultant on Mythbusters and MacGyver. Ask me about the physics of pretty much anything!
3548
Does a Mayfly, which only lives a day, evolve fast than a human?
4799
Is body chemistry affected by sound, in the same way that melatonin production is affected by light?
96
What is the reason for Ethiopia demographic boom in recent years?
40
How do earthquakes happen that are far from tectonic plates fault lines?
146
How does a flu vaccine lessen symptoms when you catch a flu variant that isn’t one of the variants in that seasons vaccination?
17
Are there any successful attempts to create a substance that is made up entirely with antimatter particles?
2
Have we ever seen a stellar ignition?
3
Why are green aurora borealis more common than the red/ purple ones?
74
How do astronomers know the "red shift" is coming from the Doppler effect and not from static stars producing light at a red wavelength?
3
How do they catch interplanetary dust particles?
4097
Is there any organism that has more than one brain?
76
Do NSAIDs, such as ibuprofen, reduce specific areas of inflammation or do they reduce inflammation overall?
3
What are all the swirly patterns on Jupiter?
1
How do bonding and anti bonding orbitals form?
1
Does sunlight lose any energy or specific rays (UV-A, UV-B, etc.) when it's reflected by a mirror?
6
Why do some plants need full strong direct sunlight but others need partial shade and indirect sunlight? What is the physiological/chemical reason behind this?
3421
How much radiation does a luggage scanner deliver vs say medical x-ray?
0
Do other moons in our solar system have a 'near side' and 'far side' relative to the body they orbit?
35
Would Koko, the sign-language speaking gorilla, have been able to translate what a different, non-signing gorilla was saying?
14
[chemistry][nuclear physics] if the island of stability does exist, do we have any way of estimating what the behavior/properties of those elements will be like?
48
How do we know the temperature of the centre of the sun?
15
Most antibacterial sprays kill 99.9% of germs. What's the 0.1% of bacteria consist of?
31
How do they reproduce seedless fruits/vegetables ?
3
When sound waves interfere in air, they create beat frequencies. Does this also happen when electromagnetic waves interfere in space?
12
Is it possible for an object to be travelling so fast it would bounce off the atmosphere?
16
Is Crystallized Bismuth the Only Instance of Naturally Occurring Right Angles?
3
Will more electric cars on the road have any positive effect on the environment if electricity to power these cars is still generated by fossil fuels?
4
How do we know what the internal structure of planets and moons is?
620
Can someone explain the environmental impact of electric car batteries?
11
How is the CMB used to calculate the Hubble constant?
5
If we reversed all charges would the world be the same?
9
Would it be possible for a planet's day to be longer than its year?
28175
Do heavily forested regions of the world like the eastern United States experience a noticeable difference in oxygen levels/air quality during the winter months when the trees lose all of their leaves?
3
When a banana ripens, does it gain calories?
3
Are people who are addicted to prescription pain meds addicted to the chemical, or the effect? Could an addict use one to substitute the other, or would their body go into withdrawal?
2
How does the sky look like on Mars? How bright is the Sun comparing it to the view from Earth?
9
How would quantum computing break modern cryptography?
0
How do compilers adapt to different hardware?
18
Does breast size affect risk of breast cancer?
5
Do snakes have saliva glands?
12 The_Neath Not entirely sure on the details as it’s been a few years since my chem degree but an abbreviated explanation goes as follows: The first topic to introduce is how temperature affects the motions of molecules. Molecules are in constant motion, except at absolute zero (0K or -273 celcius) and that motion increases with temperature. So as molecules are heated up, they begin to move faster and faster; they acquire more kinetic energy, which is why materials expand when heated. Conversely, as the temperature is lowered, the motion of these molecules becomes sluggish. Water consists of two hydrogen molecules bonded to an oxygen molecule. Oxygen is more electronegative (electron attracting) than hydrogen and so pulls the hydrogen’s electrons away from them. This results in the hydrogens having a very slight positive charge, and the oxygen having a slight negative charge, creating a dipole. As we know, like charges repel whilst unlike charges attract and so, when to or more water molecules are brought into close proximity, they will reorient themselvelves so that the opposite ends of dipoles are facing each other. Think of two bar magnets: if you place them close to each other, they’ll naturally orient themselves so that the North Pole of one magnet lines up with the South Pole of the other. The same thing happens with H20, but with an electric dipole as opposed to a magnetic one. We call the force of attraction ‘hydrogen bonding’. For water, it turns out that these hydrogen bonds have an optimal distance of 1.5 to 2.5 Angstroms (1 Angstrom is one ten billionth of a metre). As a result, in scenarios where hydrogen bonding is do,infant water molecules will naturally an intermolecular distance of 1.5-2.5 A So, to summarise we have the thermal motion of water, and an attractive force due to hydrogen bonding. At temps above 4 degrees, thermal motion is diominant and the molecules ‘ignore’, to a greater or lesser extent, hydrogen bonding. As the temperature drops, this thermal motion becomes more sluggish, and the molecules can begin to pack more closely together. This increases the density until the temperature drops to4 degrees. Below this point, hydrogen bonding forces become significant and start to ‘coerce’ adjacent molecules into adopting that optimal distance of 1.5-2.5 A. This spacing is on average greater than the spacing between water molecules at 4 degrees and hence the molecules ‘spread out’ over a greater distance. More spread out molecules = lower density. Hope this goes some way to answering your question.
10 0 The_Neath Not entirely sure on the details as it’s been a few years since my chem degree but an abbreviated explanation goes as follows: The first topic to introduce is how temperature affects the motions of molecules. Molecules are in constant motion, except at absolute zero (0K or -273 celcius) and that motion increases with temperature. So as molecules are heated up, they begin to move faster and faster; they acquire more kinetic energy, which is why materials expand when heated. Conversely, as the temperature is lowered, the motion of these molecules becomes sluggish. Water consists of two hydrogen molecules bonded to an oxygen molecule. Oxygen is more electronegative (electron attracting) than hydrogen and so pulls the hydrogen’s electrons away from them. This results in the hydrogens having a very slight positive charge, and the oxygen having a slight negative charge, creating a dipole. As we know, like charges repel whilst unlike charges attract and so, when to or more water molecules are brought into close proximity, they will reorient themselvelves so that the opposite ends of dipoles are facing each other. Think of two bar magnets: if you place them close to each other, they’ll naturally orient themselves so that the North Pole of one magnet lines up with the South Pole of the other. The same thing happens with H20, but with an electric dipole as opposed to a magnetic one. We call the force of attraction ‘hydrogen bonding’. For water, it turns out that these hydrogen bonds have an optimal distance of 1.5 to 2.5 Angstroms (1 Angstrom is one ten billionth of a metre). As a result, in scenarios where hydrogen bonding is do,infant water molecules will naturally an intermolecular distance of 1.5-2.5 A So, to summarise we have the thermal motion of water, and an attractive force due to hydrogen bonding. At temps above 4 degrees, thermal motion is diominant and the molecules ‘ignore’, to a greater or lesser extent, hydrogen bonding. As the temperature drops, this thermal motion becomes more sluggish, and the molecules can begin to pack more closely together. This increases the density until the temperature drops to4 degrees. Below this point, hydrogen bonding forces become significant and start to ‘coerce’ adjacent molecules into adopting that optimal distance of 1.5-2.5 A. This spacing is on average greater than the spacing between water molecules at 4 degrees and hence the molecules ‘spread out’ over a greater distance. More spread out molecules = lower density. Hope this goes some way to answering your question.