« on: 15/09/2023 20:13:10 »
Thanks, Evan_au. As I explained above I answered similarly in a more verbose but most likely less clear answer that evaporated.
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length of the air column and the timbre of the harmonics are determined by the wood (or metal in most cases nowadays) .So, a brass flute would sound more like a tin whistle than like a wooden flute.
: if you filled your trombone or bagpipe with helium, would that alter its pitch?One way to find out; check on YT and see if it's been done.
- Half of the time, the Sun is above the horizon for a radiotelescope on the far side of the MoonTrue, but for on the "near" side of the moon, the earth is in line of site 100% of the time and on earth the earth is in line of site 100% of the time.
Reversing time by flying around the Earth is not compatible with our understanding of General Relativity,But if you fly eastwards from Samoa you can arrive yesterday, and 20,000 miles to the west, even in a light aircraft.
, are they god/bad/neutralFrom the viruss perspective they are very good.
3, how are they madeThe same way a virus makes any other protein; they hijack the biochemical pathways of the cells they infect.
4, do they occur naturallyYes; they are part of many viruses.
5, if they are bad, how do we get rid of themOur immune system destroys them (if we are lucky)
My simplistic understanding of what they said is:It's actually about 1/10000th of that. In cosmic coordinates (the only coordinate system I know that describes the universe), the oldest light we see (that of the CMB) was emitted at a proper distance of about 1.5 million LY away. The reason it took 13.8 billion years to get here is due to the very high expansion rate of the universe back at the time of the recombination event, perhaps 3M km/sec/mpc compared to 70 km/sec/mpc today.
- Roughly 15 (or 14) billion light years is the distance from "where the source was when the light was emitted" to "where we are now"
Roughly 100 billion light years is the distance from "where the source is now" to "where we are now"That would put it beyond the size of the visible universe which means we could not see it. So around 45 billion light years is the proper distance from "where the source is now" to "where we are now".
- There is an even smaller number which represents the distance from "where the source was when the light was emitted" to "where we were back then"Well since we have not moved significantly in that time, that distance is also that 1.5 MLY figure. Cosmic coordinates has the Earth at the center, unmoving. You have to assign the origin somewhere.
As relativity illustrated, all times and distances are relative to which frame of reference you are talking aboutYes, which is why I carefully specified the cosmic frame and not say some inertial frame, which isn't valid at all at large distances since spacetime isn't Minkowskian.
And anything outside your light cone is irrelevant to you (eg if some object is now 100 billion light-years away, light from that object will probably never reach us, due to the expansion of the universe).Correct. Any recombination light emitted from what is currently over about 58 BLY away will never reach us. Any light emitted today from over 16 BLY away will also never reach us. That latter figure is the current distance to the event horizon.
Ahh video, hours and hours of people recording their holidays on camcorders,Before Facebook, you had to photograph your lunch, rush to the chemist, get the film developed, make 25 postcard prints,then go to the post office and send them to your friends, by which time the meal was cold.
Hey... Does anyone have any comments on my back-of-the-envelope calculation of air being 99.85% vacuum?While your calculation isn't precise, it's a whole lot better than lots of the ideas put forward in this thread.
Especially the part where I try to derive the refractive index of air from the refractive index of liquid nitrogen
- The method I used for that calculation used a lot of hand-waving
- What would be a better method of calculating it?
Quote from: hamdani yusuf(400 kHz homing beacon)...interference and diffraction are distinct phenomena, but both are effects of superpositionThe behaviour of radio waves from a homing beacon can be described quite well by Maxwell's equations. This is "classical" physics.
- Superposition derives from quantum theory, and cannot be described by classical physics.
- You don't need superposition to describe radio waves
The superposition principle, also known as superposition property, states that, for all linear systems, the net response caused by two or more stimuli is the sum of the responses that would have been caused by each stimulus individually. So that if input A produces response X and input B produces response Y then input (A + B) produces response (X + Y).
A function F(x) that satisfies the superposition principle is called a linear function. Superposition can be defined by two simpler properties: additivity
for scalar a.
This principle has many applications in physics and engineering because many physical systems can be modeled as linear systems. For example, a beam can be modeled as a linear system where the input stimulus is the load on the beam and the output response is the deflection of the beam. The importance of linear systems is that they are easier to analyze mathematically; there is a large body of mathematical techniques, frequency domain linear transform methods such as Fourier and Laplace transforms, and linear operator theory, that are applicable. Because physical systems are generally only approximately linear, the superposition principle is only an approximation of the true physical behavior.
The superposition principle applies to any linear system, including algebraic equations, linear differential equations, and systems of equations of those forms. The stimuli and responses could be numbers, functions, vectors, vector fields, time-varying signals, or any other object that satisfies certain axioms. Note that when vectors or vector fields are involved, a superposition is interpreted as a vector sum. If the superposition holds, then it automatically also holds for all linear operations applied on these functions (due to definition), such as gradients, differentials or integrals (if they exist).
However, I hope you will not be offended. If I said, we could use a second opinion of a physicist with regards to this particular point. because I believe it's important, I don't remember you addressing it anyway
Literally existing!? partly existing!? There are no such things, and they have no meaning in this universe, it's either you exist, or you don't.
I think the name quasi-particles has nothing to do with them being real or imaginary or partly existing. They have mass and they interact, they are a form of matter.
Although am not sure if they can split the positron in a different experiment into anti-quasi-particles.
what mattered is the question: would there be any matter left of the Electron? which you did not address as well.
Maybe, they don't need a medium like light, or maybe when they are bound, they are each other's medium, maybe if there is a force that governs their bound state (external factor) maybe, it would be their medium, can you say for sure it is impossible to be?
I don't see that; they can't cease to exist in any sense other than "cease to exist"
There is space between the particles, held at distance by the nuclear strong force which is strong enough to resist the pressure due to the gravity.Which is not entirely true and also uses the term "pressure" in a very informal way (I think "compression due the gravity" might have been better. You can see that calling it pressure instead of compression has started a bad trend because @evan_au has gone right down the same road).
If the electrons could get to the protons, they'd likely be turned into neutrons as had occurred to most of the proton/electron matter, but the picture below has electrons quite deep where the protons are, so go figure.The Chandrasekhar limit describes the point where the density of electrons would exceed that permitted by the Pauli exclusion principle. If the star has mass above the Chandrasekhar mass, then gravity is too strong and the pressure due to electron degeneracy is insufficient to stop it. At that point, either the temperature has to increase, so that the degeneracy of the electron gas is lifted and higher energy states are available to the electrons (which doesn't happen*) OR ELSE the usual thing happens.
There is another limit: If the total mass of the neutron star exceeds about 2.5 times the mass of the Sun (in a ball only 10km across!), it is thought that even the Strong Nuclear Force will not be able to withstand the pressure, and it will collapse into a black hole.That comment from evan_au was just another example where it reads as if "pressure" is what was causing the inward collapse and not the thing opposing it. Additionally, degeneracy pressure has to be mentioned again. It's not just the strong force that is keeping the Neutrons apart. Neutrons are also fermions - they behave much like electrons and must comply with the Pauli exclusion principle. The degeneracy pressure of the Neutron soup is the last bastion that gravity has to overwhelm. This one is a much more genuine last great barrier where degeneracy pressure and the Pauli exclusion principle really is everything because there is no alternative this time. The electrons could combine with protons and be removed. The neutrons don't seem to fuse with anything and be removed.
Quote from: bored chemistMainly the MW is in orbit around itself.And the mass of the Milky way is dominated by the (so far) invisible Dark Matter halo.
if the tetrahedral diamond carbon structure could coated with something like a graphene carbon surface,The graphene would act as kindling.
graphene carbon surface, which has no loose bondsGraphene is entirely covered with loose bonds and is rather reactive.
But at the surface are "loose" carbon bonds, which are much more reactive. Dissolved oxygen will react with these bonds, exposing yet more unpaired carbon bonds, and slowly eroding the diamond.If that was significant, the same process would occur in the absence of water and indeed, it does. Diamonds will burn in air.
bends in the road can take the car in front out of the beam for a few seconds. So it appears to "remember" the speed of the car in front for perhaps 5 secondsBut the car in front could do an emergency stop in the 5 seconds it's out of view, can the assisted braking respond in the time left after the car reappears?
The more complexity in the control system, the more responsibility on the driver to understand it in detail, and to understand (and take action) when it hits corner cases where it doesn't do what you intend.The more complexity in the control system, the more opaque it generally gets.
if the car in front is slowing to turn a corner, and I can see that it will be safely out of the way before I get close; the radar system (configured for sensitive mode) sees the car in front slowing to a near stop in the line of sight, and rapidly slows down my car. Flicking off the speed control for a second resolves this problem.The problem with automation is fighting it to stop it doing what you don't want can often make more work than doing the job yourself.
As I understand it, the magnitude of a wave function indicates the probability of detecting the particle in a particular place.Yes. At a particular place and also a particular time if ψ = ψ(x,t) = a function of space AND time, which is how CompuAI seemed to be representing the wave function.
Many compounds with chiral asymmetry that exist in right and left handed configurations will rotate the plane of polarisation...I completely agree. It's not clear that polarising lenses based on crystalline macromolecules really are just blockers rather than rotators of polarised light. (I also agree with the other statement but that's why I'm asking if anyone knows of a suitable experiment).