Score
Title
180
AskScience Panel of Scientists XVII
9410
Megathread: 2017 Hurricane Season
6246
There is a video on the Front Page about the Navy's Railgun being developed. What kind of energy, damage would these sort of rounds do?
2943
In 1972 a woman fell 33,332 feet without dying. How is that possible?
391
Could there exist an Earth-like planet in which continents move extremely fast?
6256
Was working at Jimmy John's today when I customer came in and was severely allergic to cucumbers but could eat pickles, how's that possible?
12
In physics, why is the formula to calculate force F=ma instead of F=mv (mass x velocity)?
3
Could we railgun the Moon?
54
How do rainbows that curve away from the sun work?
17
When I tear open plastic packaging (like a bag of chips or any type of plastic packaging) , are chemical bonds being broken? What is happening on the molecular level during the tearing?
14
How accurate is it theoretically possible for weather forecasting to be? For example, with a powerful enough supercomputer, will we eventually be able to predict the exact track of a hurricane weeks in advance? Are there any other factors limiting prediction accuracy aside from computing power?
21
Why Does Distilled Water Evaporating Slower Than Tap Water?
13366
What is the gold and silver foil they put on satellites and why is it important?
19
For a reaction with a given reaction mechanism, is the activation energy a constant?
3
Iron Man's arc reactor could theoretically work by using Palladium isotopes, how much energy could this produce and how difficult would it be to make?
22
What Does Sagittarius A* Look Like?
6
Do the radioactive elements in nuclear weapons emit detectable radiation?
5
Does the heating of the earths surface during summer months affect plate tectonics?
12
What is gravity like at the center of the Earth?
58
Is all matter composed of stardust?
27
What causes the smoke cloud around a railgun's barrel if it doesn't use gunpowder or explosive propellant?
8
Since the surface of the Sun is only ~14 times hotter than my oven when I'm baking a pizza, why am I able to feel the Sun's heat from 93 million miles away?
4
What is the speed difference between the different mass state components of neutrinos in flight?
2
No-slip condition with a draining pipe?
4
Why do lots of Viruses (Ebola, Bubonic Plague etc) present with Flu like symptoms? How can someone tell the difference?
3
Can someone explain what a typical MD simulation of a protein would look like and what you get from this?
1
Why does gamma decay only emit gamma radiation and not other wavelengths, like visible light?
56
In terms of evolution, why is vitamin D synthesis dependent on exposure to sunlight?
4
So does recent proof in math mean any 2 infinities are equal?
4
How does the difficult with heat dissipation in space restrict computational power on small spacecrafts, and how do engineers handle this problem?
43
Why does the sun and the full moon appear bigger when near the horizon?
7
How do you explain photoelectric effect using quantum mechanics?
119
Does the "location" of a headache say anything about its cause?
3
Why are rabies vacines so different between dogs and humans?
3
Why does tidal acceleration happen sattelites that orbit a oceanless planet?
62
We have maps of what the continents looked like millions of years ago when they were all together. How accurately can we map what the continents will look like millions of years from now?
18
As time progresses, does the perimeter of the visible universe recede because photons (albeit redshifted ones) from distant stars finally reach us, or does it get closer because inflation pushes stars at the edge of the visible universe away faster than their light can get to us?
0
Why hasn't NASA ever sent a microscope to another celestial body?
50
Is it possible to micro dose a poison and eventually gain immunity?
13
What is the ph of liquid co2?
9
Would mechanically moving electrons create a super-strong magnetic field?
12
My Uncle was just diagnosed with Creutzfeldt-Jakob disease (CJD), a prion disease. What makes these disorders so hard, to impossible to treat?
195 RobusEtCeleritas In a beta-plus decay, it's not a single neutron which is decaying into a proton, it's an *entire nucleus* decaying into a new species. While a free proton can't decay into a neutron, beta particle, and neutrino due to energy conservation, an entire nucleus can decay to a species of lower mass by converting one of its protons into a neutron.
81 somedave An isolated proton is less massive than an isolated neutron yes, but a bound state of a neutron and proton is less massive than two isolated protons. This is due to the binding energy of the proton and neutron. Remember E = mc^2, so as the two isolated protons had more mass, they had more potential energy that the deuterium nucleus, this energy is released in a positron and neutrino that are emitted after fusion. Edit: Typo
19 [deleted] [removed]
6 centurion236 Classical physics gives us conservation of mass and energy, but these are approximations. Einstein proposed a system in which mass and energy are interchangeable, and mass-energy is conserved. You'll notice that every element is slightly lighter than the sum of its neutrons and protons. That "mass defect"is related to the forces and energy that holds the nucleus together. To enable positron decay, the decay must release enough energy to make up for the mass that is "spontaneously" created.
3 DrFeathers The whole system must have more energy than the state it wants to decay to. In the case of a free neutron you only have the neutron's mass to work with. Once you are in a nucleus, then you are considering the mass of all of the protons and neutrons as well as the binding energy. A proton can sort of "borrow" energy to allow a decay to happen, as long as the mass of the resulting nucleus will be lower.
191 0 RobusEtCeleritas In a beta-plus decay, it's not a single neutron which is decaying into a proton, it's an *entire nucleus* decaying into a new species. While a free proton can't decay into a neutron, beta particle, and neutrino due to energy conservation, an entire nucleus can decay to a species of lower mass by converting one of its protons into a neutron.
77 0 somedave An isolated proton is less massive than an isolated neutron yes, but a bound state of a neutron and proton is less massive than two isolated protons. This is due to the binding energy of the proton and neutron. Remember E = mc^2, so as the two isolated protons had more mass, they had more potential energy that the deuterium nucleus, this energy is released in a positron and neutrino that are emitted after fusion. Edit: Typo
18 0 [deleted] [removed]
8 0 centurion236 Classical physics gives us conservation of mass and energy, but these are approximations. Einstein proposed a system in which mass and energy are interchangeable, and mass-energy is conserved. You'll notice that every element is slightly lighter than the sum of its neutrons and protons. That "mass defect"is related to the forces and energy that holds the nucleus together. To enable positron decay, the decay must release enough energy to make up for the mass that is "spontaneously" created.
3 0 DrFeathers The whole system must have more energy than the state it wants to decay to. In the case of a free neutron you only have the neutron's mass to work with. Once you are in a nucleus, then you are considering the mass of all of the protons and neutrons as well as the binding energy. A proton can sort of "borrow" energy to allow a decay to happen, as long as the mass of the resulting nucleus will be lower.