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Jul
12 |
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answered | Doubt on conservation of angular momentum for Kepler's laws |
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Jul
11 |
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Inconsistency between Velocity vs Redshift and Scale Factor vs Time plots I can't understand what you have written, what comparison you are trying you make between two graphs with different axes or what "with added Doppler" means in the context of the scale factor plot. |
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Jul
10 |
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awarded | Enlightened |
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Jul
9 |
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Are any Population III stars red dwarfs? Is that equation for low (zero) speed stars? I think halo stars will accrere much less because of their velocity wrt the ISM. |
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Jul
9 |
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answered | Dark matter detector experiments above ground? |
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Jul
9 |
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Regarding the absorption property of a blackbody @CPofPhysics yes, that is what I have assumed and the only situation in which your equation (ii) is accurate. If $T_c$ does not change "significantly" then the inserted body will eventiually reach an equilibrium at temperature $T_c$ - when it will emit and absorb energy at exactly the same rate. |
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Jul
9 |
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Are any Population III stars red dwarfs? How much matter does a dwarf star accrete over 10 billion years in the Galactic halo? Negligible I presume? |
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Jul
9 |
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answered | Regarding the absorption property of a blackbody |
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Jul
9 |
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revised |
Using helioseismology what are the equations astrophysicists use to determine the age of the Sun? deleted 1 character in body |
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Jul
9 |
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Using helioseismology what are the equations astrophysicists use to determine the age of the Sun? added 12 characters in body; edited tags; edited title |
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Jul
9 |
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Using helioseismology what are the equations astrophysicists use to determine the age of the Sun? added 967 characters in body |
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Jul
9 |
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Using helioseismology what are the equations astrophysicists use to determine the age of the Sun? A creationist would say that the Sun and its oscillation spectrum were created as they are (6000 years ago or whatever). You may as well argue with a pigeon. @Walter About the best you can do is say the Sun was born from interstellar gas, but seismology shows its internal composition is now half helium. It takes about 4.7 billion years to make that helium, agreeing with the precise radioactivity ages. |
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Jul
9 |
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Cooling properties of trees and thermal radiation Note that trees have the opposite effect in winter - the ground and air temperature are warmer near trees in cold weather. |
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Jul
8 |
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Confused about Weinberg's result of gravitational time dilation added 300 characters in body |
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Jul
8 |
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Confused about Weinberg's result of gravitational time dilation added 300 characters in body |
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Jul
8 |
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revised |
Confused about Weinberg's result of gravitational time dilation added 300 characters in body |
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Jul
8 |
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Confused about Weinberg's result of gravitational time dilation The freely falling clock cannot be simultaneously at two positions. The formula is comparing the clock rates at one position. |
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Jul
8 |
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Confused about Weinberg's result of gravitational time dilation Well what do you mean by "a clock runs slower in a gravitational field" - it only runs slower compared to a stationary clock that is "higher up" - i.e. in a different place. Your clocks are in the same place. |
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Jul
8 |
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Confused about Weinberg's result of gravitational time dilation Now I'm confused. We need a proper definition of what these time intervals are. Is $dt$ (in contradiction with almost every GR text I've seen) a proper time interval for a stationary observer at some point in the gravitational field and $\Delta t$ the proper time interval for a free-falling body at the same position? |
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Jul
8 |
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answered | Confused about Weinberg's result of gravitational time dilation |