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The universe about halfway through recombination (it was a long process but at the halfway point, it's flips to being mostly clear), much like the universe today, has a temperature. Today the temperature of the universe is about 2.7K, but at recombination it was around 4000K. This temperature corresponds to the blackbody radiation profile of the universe. ...


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As far as we know, nuclear decay is truly random, that is, random in the quantum mechanical sense. That is, when you observe the system, there is a probability that you will see the decay products rather than the original nucleus, because the wave function of the system is a superposition of the parent nucleus state and the daughter nucleus state (+alpha ...


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The electrons released in $^{60}$Co decay are mostly only about a third of a MeV in energy and are easily stopped. For example if your source is inside a metal foil the electrons will be blocked by it and only the gamma rays will get out. The source you're using may have been deliberately designed to block the electrons.


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Normally the "data" that is modulated onto the radio frequency of the carrier has a lower frequency than the carrier (this is not an absolute requirement, but few systems exceed it). In case of cell phones, the carrier wave is around 800-1900MHz, while the data rate is on the order of a few Mbit/s, i.e. two orders of magnitude slower than the carrier ...


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In the case of frequency modulation, the information ("data") is contained in slight modulations of the carrier frequency over time. A "1" could mean that the frequency gets a bit higher and a "0" could mean it gets a bit lower. The modulation in frequency must be tiny enough as to not overlap with the next carrier frequency. And as long as the next higher ...


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did the sky suddenly become dark, or was the amount of radiation basically same after as before? What would the distribution and timescale have been like? Recombination of hydrogen did not suddenly happen. Instead, to go from 90% of hydrogen being ionized to 10% of hydrogen being ionized, took about 100,000 years, from about 260,000 years after the ...


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Perhaps would be now possible and practical? http://www.nature.com/srep/2014/140611/srep05249/full/srep05249.html Plasmon-assisted radiolytic energy conversion in aqueous solutions Baek Hyun Kim, Jae W. Kwon Nature Scientific Reports Vol.: 4, Article number: 5249 DOI: 10.1038/srep05249 ...


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Your question addresses a general principle in quantum mechanics. If we have an initial state $i$ and a final state $f$ then we can calculate the probability of a transition from $i$ to $f$, but this is only a probability - we cannot say when the transition will happen, only the probability that it will happen in some time interval. This isn't because we ...


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Your math does check out: \begin{align} r&=vt \\ &=0.05\cdot2.9979\times10^{10}\frac{cm}s\cdot4\cdot604800\,s\\ &=3.63\times10^{15}\,cm\\ &=36.3\times10^9\,km\\ &=0.012\,pc \end{align} When a supernova explodes, it enters the free expansion phase, it's position is linear in time ($r=vt$, as used above). It stays in this phase for a few ...


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"The process of imparting energy from the nucleus to an orbital electron is a quantum process and may be seen as taking place by means of a virtual photon. In that sense the photon involved can be considered as a "virtual gamma ray"..." (Wikipedia) The electromagnetic force is indeed a long range force - virtual photons bind the electrons to the nucleus. ...


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In thermal equilibrium, at a fixed temperature, there still exist processes that are able to convert energy carried by a frequency $f$ photon (or another particle) to photons (or other particles) at different frequencies. All these processes are in equilibrium. By definition, a black body is an object that absorbs the incident light of all frequencies. It ...


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The modern mind picture of electrons bound to a nucleus is that of an orbital rather than of an orbit as you seem to be thinking. However, your ideas are still somewhat meaningful in this modern picture in that region of electron delocalisation is more tightly confined around the nucleus for lower energy orbitals than it is for higher energy ones. You might ...


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You are doing fine. You are correct to say the sun only shines on one side of the spacecraft, which the page you link to misses. Increasing the radiating area by a factor of six will decrease the temperature by a factor $\sqrt[4]6 \approx 1.565$ Dividing their $285$ by $\sqrt [4]6$ and multiplying by $\sqrt [4]{1.36}$ (to correct for your more accurate ...


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Dielectric heating is the priciple of a microwave oven. Water $H_2O$ has a strong dipole moment. Since the water molecule is not linear and the oxygen atom has a higher electronegativity than hydrogen atoms, the oxygen atom carries a slight negative charge, whereas the hydrogen atoms are slightly positive. As a result, water is a polar molecule with an ...



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