06-17-2020 05:58 PM
#2101
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06-17-2020 09:13 PM
#2102
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06-17-2020 09:40 PM
#2103
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06-18-2020 02:05 AM
#2104
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06-18-2020 02:18 AM
#2105
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06-18-2020 05:15 AM
#2106
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https://www.forbes.com/sites/waynera.../#38bd4a7e5939 | |
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06-18-2020 05:17 AM
#2107
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Point being, quantum computers will not be allowed into the general market until they have quantum security. | |
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06-18-2020 05:30 AM
#2108
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Well sure, but that doesn't mean they're delayed, it just means the ones with the technology are gonna do their best no one else gets it. Restricted would be a better word. | |
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06-18-2020 05:50 AM
#2109
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Well I mean "delayed" in the context of us, the general public, getting it. So it means exactly the same a "restricted" in that context. I'm not quite defining words myself. | |
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06-18-2020 09:25 AM
#2110
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So according to General Relativity, all reference frames are equally as valid as one another. So if I observe someone travelling at 0.9c, and take ten minutes or whatever to get to the sun, and the distance he traveled is around 150 million km, that's a valid observation. Likewise, to the lunatic travelling to the sun, he gets there in like 20 seconds or whatever (didn't calculate that but it's obviously much faster than ten minutes). The distance he thinks he traveled is much less than 150 m km, let's say a million km (again can't be bothered to calculate). This too is a valid observation. This is fine, I've got no problems with this. | |
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06-18-2020 01:00 PM
#2111
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I'm pretty sure you mean all inertial reference frames are equally valid. | |
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06-18-2020 02:24 PM
#2112
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06-18-2020 04:18 PM
#2113
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I think you mean "free-falling in a gravitational field," rather than "moving at constant velocity." | |
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06-18-2020 05:54 PM
#2114
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06-18-2020 06:49 PM
#2115
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06-18-2020 06:50 PM
#2116
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06-18-2020 06:57 PM
#2117
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06-18-2020 07:08 PM
#2118
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06-18-2020 07:10 PM
#2119
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It's space and time that are not constant for all observers. | |
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06-18-2020 07:21 PM
#2120
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Ok yeah I've heard that, my mind had just blocked that silliness away. | |
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06-18-2020 07:23 PM
#2121
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What I mean is that none of that is any more intuitive than QM. | |
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06-18-2020 07:30 PM
#2122
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06-18-2020 07:58 PM
#2123
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Yeah but things moving around at a constant speed related to everyone else moving at various speeds is just bizarre. Or cheating. I'm guessing it's a crude software hack in our simulation. | |
06-19-2020 01:20 AM
#2124
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TY, sir. I do my best. | |
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06-19-2020 01:42 PM
#2125
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The best answers I can find for the reasons light appears to move more slowly in a dielectric medium rely heavily on field theories of matter and light. It's hard to explain them without a rigorous mathematical background without losing all the richness of conveying meaning without hand waving. | |
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06-19-2020 02:27 PM
#2126
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Struggling for time today but will revisit this tomorrow. I'm not ignoring you! I appreciate your replies very much. | |
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06-20-2020 07:45 PM
#2127
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Ok so I've had a busy couple of days, but while thinking about what we've been talking about, I do have another related question... | |
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06-20-2020 11:41 PM
#2128
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4-D spacetime curvature | |
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06-21-2020 02:28 AM
#2129
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I think I get it actually. Let's imagine the orbit of Earth, as observed by a traveler going to the sun at 0.9c. It will be an extremely eccentric ellipse, with a perihelion much smaller than observed from earth, but the aphelion will be identical (assuming direct motion to the sun). The lateral velocity of the orbit will be the same, but the observed longitudinal velocity will be much slower for the traveler than the person back home. So balance is restored, the orbital path and velocity will make sense, regardless of the frame of reference. | |
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06-21-2020 02:29 AM
#2130
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It's probably not resolved. Because the perihelion is much less, the traveler should expect to see a much faster lateral orbital velocity. Hmm this is headbending, especially for 7.30am. | |
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06-21-2020 02:30 AM
#2131
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06-21-2020 11:19 AM
#2132
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If you want a mind-bending thought experiment, consider a relativistic disk. | |
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06-21-2020 12:18 PM
#2133
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That's interesting, I'll think that through. | |
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06-21-2020 01:12 PM
#2134
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I don't there's any dispersion in empty space. The change in speed for different frequencies is a matter of the dielectric properties of a medium through which the photon travels. | |
Last edited by MadMojoMonkey; 06-21-2020 at 01:19 PM.
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06-21-2020 01:16 PM
#2135
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So this disc thought experiment... I'm visualising a massive disc, basically the size of the observable universe. It's rotating very slowly, however it is so big that the velocity at the edge is massive, relativistic even. Assuming the disc is strong enough (lol), and assuming constant rotational velocity, oh and also assuming the observer is fixed into position and is an infinitesimal point (fuck you tidal forces), the observer wouldn't notice how fast he was going. In fact from his pov, he is stationary and the centre is rotating around him at relativistic velocity. From his pov, time is normal, while the centre is dilated and in a slower time reference frame. | |
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06-21-2020 01:22 PM
#2136
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06-25-2020 04:08 PM
#2137
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What's the scoop on older generation stars? What I'm getting at is that AFAIK over the life of the universe, there have been different generations of stars. Like, say, the stars that popped up 10bn years ago were fundamentally different than the ones that pop up now. |
06-25-2020 08:13 PM
#2138
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The early universe was almost entirely composed of Hydrogen, with a bit of Helium and very small amounts of Lithium. Those are the smallest 3 atoms. | |
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06-25-2020 09:30 PM
#2139
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Thanks. Found this: |
06-26-2020 12:34 AM
#2140
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It's especially strange because there's not only life on Earth, but it's just everywhere. There's life in places we never thought it could exist, in highly toxic environments, where sunlight doesn't reach. In deep sea near volcanic vents. In secluded caves that were cut off from the outside world for millennia. In the antarctic... it's just everywhere on Earth. | |
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06-26-2020 07:13 PM
#2141
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I'm spamming this one website left and right, but again, this guy has my favorite piece on this: | |
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06-26-2020 09:25 PM
#2142
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"Our night sky consists of a small selection of the very brightest and nearest stars in the red circle." | |
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06-26-2020 10:34 PM
#2143
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06-27-2020 03:56 AM
#2144
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I'd say it's this one: | |
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06-27-2020 10:58 AM
#2145
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That article brought up some more Great Filters that I hadn't thought of before. |
06-27-2020 11:01 AM
#2146
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Rather, I should say The (3 condition) Simulation Hypothesis assumes math exists outside this reality because it relies on the exponential function to say under which conditions the probability we're in a simulation converges to 1. |
06-27-2020 11:34 AM
#2147
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@cocco: Yeah, there's simply no photo of the Milky Way from that perspective. The furthest man-made object from earth is Voyager, and it's barely away from the sun on those scales. | |
Last edited by MadMojoMonkey; 06-27-2020 at 11:37 AM.
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06-30-2020 02:09 PM
#2148
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FYI, I've asked my colleagues in the intro physics program, and 2 of them responded that they don't know the answer to this. | |
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06-30-2020 02:45 PM
#2149
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It's awesome that I've asked a question that three physics guys can't answer. | |
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07-05-2020 06:46 PM
#2150
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A wonderful demonstration of the incredible weakness of gravity... | |
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10-15-2020 03:42 PM
#2151
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What's the deal with temperature? I've watched a couple lectures now and it seems like whoever you ask you get a different answer. Isn't it always relatable to pressure of a gas in a closed system, and if so, what is all this noise: | |
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10-15-2020 03:55 PM
#2152
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Temperature is a measure of kinetic energy on the particle scale. | |
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10-15-2020 04:18 PM
#2153
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10-15-2020 04:25 PM
#2154
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10-15-2020 06:01 PM
#2155
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10-15-2020 06:08 PM
#2156
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Slight correction that at thermal equilibrium, it's not that everything is moving at the same speed, but that the distribution of speeds has settled to a specific bell-curve distribution (the Boltzmann distribution). | |
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10-15-2020 06:55 PM
#2157
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Nice correction, I have no idea what you just said! I guess I'm imagining this is a classical sense, like there's lots of tiny little balls flying around, colliding. In this instance, everything would settle to the same speed, as eventually all the balls' speeds would average out as the fast ones continually lose energy to the slow ones. Of course, atoms are not tiny little balls, so it's no real surprise that my analogy is flawed. | |
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10-15-2020 07:08 PM
#2158
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^ also yes I'm assuming all these little balls are identical. | |
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10-15-2020 07:14 PM
#2159
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Enthalpy is basically the potential heat stored in chemical bonds... right? | |
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10-15-2020 07:45 PM
#2160
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^ hmm that's not quite right. I'm neglecting work, which is an important factor. Plus, we should know how much "potential heat" is stored in chemical bonds, yet it seems it's impossible to know how much enthalpy a system has. | |
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10-15-2020 07:50 PM
#2161
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I'm fairly certain the Boltzmann distribution is known from classical physics, meaning known prior to quantum mechanics, so it's about tiny balls flying around, not wave functions. | |
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10-15-2020 07:59 PM
#2162
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Yeah. Energy is at the same time very simply and very mysterious, IMO. | |
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10-15-2020 08:07 PM
#2163
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It's the same issue in electronics where it's impossible to know the voltage at any point in space (or on a circuit board). We don't know where 0 is. We can wave our hands and say the Earth (ground) is 0 V, but we can't prove it. We can only prove the difference in voltage between any 2 points. | |
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10-16-2020 05:25 AM
#2164
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Yeah, like I say, energy is complicated as fuck. | |
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10-16-2020 05:34 AM
#2165
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Another way to understand why kinetic and potential energy are the same thing is to fire a bullet at someone's head. The final thoughts of our unfortunate friend will be "holy fuck, this bullet has a lot of kinetic energy". But let's assume that as soon as we fire the bullet, we run at the same speed as the bullet in the same direction. As we look at the bullet, we think it has no kinetic energy. What makes our observation wrong? Nothing at all. We observe potential energy in the bullet and kinetic energy in the soon-to-be-dead friend, because our FoR is differently to the poor soul about to get hit by the bullet. Both of our observations are equally as valid, and therefore there is no difference between kinetic and potential energy, just a difference in velocity, and therefore different frames of reference. | |
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10-16-2020 10:12 AM
#2166
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This is all neat n' stuff, but the moment the entropy/temperature as well as the enthalpy/temperature relation shits the bed is when you reach a phase change. When water reaches 100°C and you keep adding heat, the entropy keeps increasing, the enthalpy keeps increasing, but the temperature stays the same while a considerable amount of energy is being used up for whatever it is a liquid is doing when it turns into vapor. | |
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10-16-2020 10:40 AM
#2167
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What I like about enthalpy is that if you put energy into something then its enthalpy increases linearly regardless of its state and it's nearly identical to the energy put in. | |
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10-16-2020 05:15 PM
#2168
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10-19-2020 09:51 PM
#2169
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Just to go back a couple posts. | |
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10-21-2020 07:11 AM
#2170
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Does that energy not come from the temperature of the gas? That is, isn't this why gas cools as it expands? The gas takes up more volume for the same mass, so has lower average thermal energy. Eventually the gas stops expanding because it can lose no more thermal energy to the surroundings. | |
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10-21-2020 11:26 AM
#2171
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The energy of the temperature of the gas is calculated separately from the energy to "create" a volume to exist in. | |
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10-21-2020 02:46 PM
#2172
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I think I get it. The surface tension analogy is helpful. I guess you just have to imagine empty space having a surface tension that needs to be overcome for an object to occupy space. Surface tension might not be accurate, but it's fairly intuitive, as it provides a constant inward pressure to an immersed object. If the object cannot overcome this pressure (it requires energy to do so) then the object will collapse into a singularity (lol). | |
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10-21-2020 05:13 PM
#2173
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I'm pretty sure that displacement term would just be 0 J in empty space. Assuming there's no environment to be displaced, the displacement term would vanish. | |
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10-24-2020 09:56 AM
#2174
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So it's not a vacuum pressure, it's purely mechanical? | |
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10-24-2020 11:08 AM
#2175
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It's nearly mechanical, if not mechanical, but that's just semantics. | |
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