Electricity travels at nearly the speed of light.
Electrons themselves travel like molasses:
"In the case of a 12 gauge copper wire carrying 10 amperes of current (typical of home wiring), the individual electrons only move about 0.02 cm per sec or 1.2 inches per minute (in science this is called the drift velocity of the electrons.). If this is the situation in nature, why do the lights come on so quickly [when you flip the switch]? At this speed it would take the electrons hours to get to the lights."
This completely caught me by surprise, but it makes sense once it's pointed out. Imagine a pipe filled with solid balls that just fit in it, with little friction. If you push a ball in one end, a ball pops out the other almost immediately. But not the same ball! Even if you keep pushing balls in, that first one you pushed will take a while to get the other end.
Update: as rrobukef notes in a reply, this would be the case for direct current (DC). With the usual household alternating current (AC), the electrons barely move at all!
https://www.uu.edu/dept/physics/scienceguys/2001Nov.cfm
https://wtamu.edu/~cbaird/sq/2014/02/19/what-is-the-speed-of...
Hence you can get shocks from one live wire.
https://www.allaboutcircuits.com/textbook/semiconductors/chp...
The electrons actually move mostly side to side as they bump into each other. Pushing power just pushes the ones further down the pipe into the light, not the ones entering the copper cable.
For this to work, a hypothesis must be falsifiable. Most pseudoscience (and religion) makes non-falsifiable claims, meaning they are incompatible with scientific discourse.
This simple observation is a powerful tool in any bullshit-detection kit.
Once produced, a scientific hypothesis of any merit will be attacked vigorously with experiments until enough parties are convinced that disproof is sufficiently unlikely. The process isn't always pleasant for those making the falsifiable claims.
Sadly, this is not how science is taught in most schools. There, students are given the "truth" and, on a good day, asked to verify it experimentally. We are now living with the terrible consequences of generations of youth who think science is about "proving" the truth.
The idea you're stating is something like "It's not possible to prove hypothesis H1 if H1 is 'all swans are white' by sampling swans and only getting white ones, but it's possible to disprove hypothesis H1 by finding a black swan."
However, you can prove hypothesis H2 that "there exists a black swan" by finding such a swan. And you can't really disprove it for the same reason that you can't prove H1.
Neither of theses hypotheses are proven/disproven in the mathematical sense of "proof" but finding sufficient evidence in favor or against a hypothesis is practically the same in the case of science.
The Bayesian version of this is that the hypothesis is something like "the probability of a swan being white is P" and the value of P will by updated based on the strength of the evidence. It will never be exactly 0 or 1, but it will be close enough in many cases. Then you avoid the argument about whether a hypothesis is a binary "true" or "false" but discuss a continuous probability. E.g, the a hypothesis about the Earth being round has a probability close to one for most people while Russell's teapot and Sagan's invisible dragon have probabilities close to zero until evidence shows otherwise.
To cite a paper I currently read:
> "As Chalmers (1999) remarks, when we turn to history of science, the idea that falsificationism is actively undertaken borders on laughable (see especially Feyerabend, 1975). Not only do scientists exhibit extreme reluctance to falsify their work (Woodward and Goodstein, 1996), but if falsification had been followed as a scientific method, then many of the theories generated by some of the best minds in science would never have progressed beyond their earliest explications (see Chalmers, 1999: ch. 7; Feyerabend, 1975; Kuhn, 1970c: 234; 1970d: 13; Von Dietz, 2001: 22)." (https://journals.sagepub.com/doi/10.1177/1350508409104504)
I haven't read all the sources. But it's worth mentioning that your point is controversial.
Popper knew this, by the way. So the inverse to the trap you point out here is the claims that "if not falsifiable, then unable to be true/useful", which is just as specious.
What systems for determining the truth exist that aren't built on top of some fundamental axioms?
my point is that "we define science as empirical falsificationism" is itself nonscientific by its own definition, and that that's OK, still capable of being true, and is a handy way to get stuff done.
but at this point i would say that "religion" is a very squirmy thing to define meaningfully without a lot of "well, but except when ..." clauses tacked onto the end.
these days, we adopt models. discard them if they fail and start all over again. seems to be a better and more elegant way.
A non-relativistic quantum state will return arbitrarily close to its initial state an infinite number of times. There is such a thing as interaction-free measurements: you can take photos of things without ever letting light hit a detector and you can tell whether a bomb is "active" without actually interacting with the detonator.
Energy is just a number that is calculated as a function of the state of a closed system — that this number is a constant results from the time transitional invariance of the laws of physics. Similarly, conservation of momentum is due to the spatial invariance of the laws of physics, and conservation of angular momentum is due to rotational invariance. Also, conservation of energy does not hold under general relativity.
I thought the existence of particles was relative to how fast you're accelerating? If it's relative to how fast you're moving, wouldn't that imply that absolute velocity exists, i.e. that given two objects with known relative velocity to each other, we could potentially establish which one was "really" moving and which one was "really" still?
Can you provide a link that talks about that? It goes against my understanding of why there's an uncertainty principle at all
Wait i agree energy is mass but is this specifically correct? The rest mass is always much higher when i've seen it in equations.
This is false. The dilemma is that you can't "just weigh" a compressed spring without assistance. However, you can get around it by weighing a compression device with the spring, both when it's compressing and not compressing the spring. The weight will be the same.
Weight is mass times gravity. It is the mass of the object. As affected by a single force - gravity. Gravity is a force.
A spinning ball has ANOTHER force acting on it, and therefore cannot be defined by "weight".
In short, this is an absurd statement that tries to redefine a scientific definition for...I don't even know? Sensationalism?
All forms of energy, including potential energy in the form of a compressed/stretched spring, couple to the gravitational field. Again, read about the stress-energy tensor for how this works.
> In short, this is an absurd statement that tries to redefine a scientific definition for...I don't even know? Sensationalism?
What I've said is not even remotely controversial in the physics community. Don't take my word for it; ask anyone who has taken a basic graduate course in general physics and they will agree that a compressed spring or a spinning ball weighs an imperceptibly (i.e., immeasurably) small amount more than the uncompressed spring or stationary ball, should you have a hypothetical scale that was so precise as to be able to measure the difference.
Note however that the quoted effect – difference in weight between a compressed and uncompressed spring – will realistically be so small that I doubt you could measure that in a lab. To get a sense of how small that effect is, try comparing the E=mc^2 mass-energy of a spring to its E=kx^2 compression energy...
https://hubblesite.org/contents/articles/hubble-deep-fields
I already knew that "the universe is incomprehensibly large", but seeing how many entire galaxies there were in a random dark patch of sky was eye opening to me.
Born too late to explore the world; born too early to live forever and explore the entire universe; born just in time to make dank memes.
My hypothesis is that he has narcissistic tendencies so pondering the vastness of the universe only highlights his own insignificance. I've noticed similar reaction from people who visit a large city for the first time and get a sense of how small they are in the grand scheme.
Thousands of similar questions on reddit for anyone interested- https://duckduckgo.com/?t=ffab&q=science+fact+site%3Areddit....
(Caveat: this is assuming people shuffle well, which of course most people don't, therefore in fact people probably have shuffled to the same state).
i remember getting a clear linear relationship once that as supposed to be a curve. Solution was error bars and a curve to match expectation. Pointless
[0] https://www.vice.com/en_us/article/zmjwda/a-code-glitch-may-...
I laughed, "Well that will only happen if you put it behind your back."
They laughed, "Everyone has an astigmatism where the nerves enter the eye. We are looking for that or any other issues."
I was so shocked when the dot disappeared.
Also happy to hear it was the normal blind spot.
https://www.wthr.com/article/news/investigations/13-investig...
Wow... just... mind blown. I always read about it, but never experienced it... wow...
The answer is in the density of rod cells (which are photon receptors of the eye that specialize in low-light) are concentrated on the outer edges of the retina. So if you look straight at a dim bulb - the photons hit the cone cells, which aren't sensitive enough, but if you look away, the photons hit the rod cells and you can see the bulb!
When you see something hanging from a suction cup in your kitchen or bathroom, it's fun to imagine that the air around you is hammering the suction cup enough to keep it stuck there. With quite some force you'll notice, if you try to pull it straight out! But let some air in through a small gap, and it will help even things out.
A lack of air by itself does nothing. It's just about the net forces.
https://en.wikipedia.org/wiki/False_vacuum
This quote blew my mind:
"The possibility that we are living in a false vacuum has never been a cheering one to contemplate. Vacuum decay is the ultimate ecological catastrophe; in the new vacuum there are new constants of nature; after vacuum decay, not only is life as we know it impossible, so is chemistry as we know it. However, one could always draw stoic comfort from the possibility that perhaps in the course of time the new vacuum would sustain, if not life as we know it, at least some structures capable of knowing joy. This possibility has now been eliminated."
I immediately went out and bought Greg Egan's "Schild's Ladder" after find out he'd used this as a plot device.
Nothing can travel faster than light through space, in a vacuum. However, if you pick two points in space that are far enough apart (e.g. at opposite sides of the observable universe), these points will be moving apart faster than light, because space itself is expanding.
The expansion of space isn’t coming from a single point outward, like an explosion. It’s expanding by the same amount at every point in the universe. People analogize this in lower dimensions to stretching fabric or blowing up a balloon.
Also, really far-away galaxies are receding from us faster than light.
And, the existence of the cosmological event horizon seems to support this too, I think. Things beyond that horizon will emit light in our direction, but that light will never reach us. In fact, without this horizon, I believe that the night sky would be much brighter.
I find it kind of sad that, as time passes, more of the universe becomes unobservable. Eventually the only stars visible from our POV will be those in our own galaxy (and galaxies that ours has merged with, in the interim).
More info at https://en.wikipedia.org/wiki/Expansion_of_the_universe
https://en.wikipedia.org/wiki/Casimir_effectSo my trip to the grocery store could be adding as much carbon dioxide to the air as the groceries I pick up!
I use that as a way to visualize the problem with "a solution".
But it is more complicated that this. Consider https://en.wikipedia.org/wiki/Elitzur%E2%80%93Vaidman_bomb_t... -- if you only poke the particle in a "parallel universe", that also changes its pattern in this one.
At the end, quantum physics says there are multiple "versions" of how the particles move, and those versions interfere with each other. By interacting with each other, particles become entangled, which means that the "versions" of their states are no longer calculated independently, but together.
There are disagreements of what exactly this means: some people believe that reality only has multiple "versions" on a microscopic level, but when the entangled configuration becomes large enough (how large? no one knows), the parallel computation collapses, one of these "versions" is randomly selected to become the actual reality and the remaining ones disappear. Other people believe that multiple "versions" is the whole story; that observing the outcome means that you (being composed of particles that follow the laws of physics) also become entangled with the particles in the experiment, and now there are multiple "versions" of you, each observing a different outcome.
So, I'd say you got it half-right. Yes, it is about "observation = interaction"; and "observer" is just a shortcut for "the thing that poked the experimental particle, optionally also a display connected to that thing, optionally also a person observing the display". (That is, you could also have a completely impersonal "observer", e.g. a machine that measures the particle but no one is looking at its display.) But quantum physics is a different thing than mere classical physics where you correct for photons being actual things that hit the measured particle. It means there actually are multiple outcomes, which then interfere with each other, at least on the microscopic level.
Please note that physics as science in general is advancing constantly, but mainstream physics advances in sprints. Currently, walking droplets and Pilot Wave Theory are not good enough to be included into mainstream physics.
In order to obtain the information you wish to 'observe', you need to interact with it.
That interaction 'collapses the wave function', or rather, you become part the wave function, but seeing it 'from the inside' looks different compared to from the outside.
Anyone got a link?
https://en.wikipedia.org/wiki/Double-slit_experiment
The most mind boggling aspect of this for me is the single photon version, which is under the "Interference of individual particles" section of the above article. The point is that you get an interference pattern even when only a single photon at a time is sent through the slits!
Yet another insight is that your chance of winning by switching doors is directly related to your chance of choosing the winning door in the first place: if you choose the correct door on your first try, then switching loses; if you choose a wrong door on your first try, then switching wins; your chance of choosing the correct door on your first try is 1/3, and the chance of choosing a wrong door is 2/3.
- You pick a door (let's say 17)
- I open 98 doors (let's say 1 - 16, 18 - 78, and 80 - 100)
- Only doors 17 and 79 are still closed
- If you happen to choose a door with a goat (⅔ of the time), the host has to choose a goat door, leaving "switch" a guaranteed win
- If you happen choose the door with the car (⅓ of the time), the host opens a random goat door and you have 50/50 between staying and switching
So always switching is the correct move - if you do that you'll win the ⅔ of the time (every time you open a goat door).
https://www.scientificamerican.com/article/the-adult-brain-d...
(the famous rat experiment with the "stimulating environment" and brain grown was later attributed to the exercise wheel)
That's why haven't had a drink for the last 5 years
In similar fashion, years ago while studying the circulatory system for the anatomy class I came across a wikipedia article. This particular part of the circulatory system was documented in detail by Egyptians in 200 BC. Knowledge came from the mummification process. The next breakthrough in this area was made in the 19th century.
Looks like our species could have a colony in Mars by now, if science were allowed to breakthrough linearly.
I think humans probably have some innate desire for institutions with religious-like properties. And as we've become more secular over the past 60 years, there's been an increase in people that seem to be making politics the replacement, which may end up being more destructive than theistic religion ever was.
Hm, but we grow in a religious setting, the larger part of the population. So, is it an innate desire or a designed reality for population control?
To some, religion = faith. And I think you'll find that most faith has little to say about science (and in the case of your example says nothing about the earth/sun relationship).
More commonly though, when referencing Religion you are really talking about Politics. Heliocentrasim, the crusades, Muslim terrorism, are all about politics, not faith.
When you make an argument using the word Religion in a political sense, but others read it as attacking their faith, then things get very ugly.
In other words you can be a devout Christian, and still consider the crusades to be awful. And you can be a good Muslim and consider 9/11 to be an act of war.
Most anytime someone talks about religion as being the cause of war and conflict, the root cause is politics, not faith.
Maybe dental implements.
Our eyes collect light that is "left over"(not reflected) from other surfaces.
Can't explain why but I had always had a sense that objects somehow emanated their own "image". Learning that colors manifest themselves because every other wavelength was absorbed was fascinating.
In reality, any photon traveling inside the Sun will almost instantly collide with some other particle, which may emit zero, one, or more photons as a result. When we say "100,000 years", I believe we're summing up the total of these photons' expected lifetimes, basically following the flux of energy rather than individual photons.
That despite the apparent complexity of the weather many atmospheric phenomena can be explained from first principles with pen and paper calculations.
That the existence of elementary particles can be derived from simple symmetry considerations (That one blows my mind every time.)
That when we look out into the universe we see elements roughly in the same proportions as they appear on earth. (We are all made out of star dust!)
if you close one eye and keep the other open you'll suddenly see one side of your nose.
> Can explain DNA
...
> Can see his own nose
"diamonds are forever"
It's appealing to believe that a crystalline structure, a pretty one too, might exist until actively changed.
Diamonds are not forever. What 'blew my mind' is that diamonds are the result of compression and very slowly decompressing. That slowly over time the outer layer leaves that state and turns to dust.
Glass is a 'liquid'
I'm much less sure about glass, I'm not even sure that science is sure about glass. Apparently one process for making glass in the old days involved something blowing and spinning discs of it to produce nearly flat segments. When installed the artisan making the window would place the thicker end down for stability or some other reason. I'm not positive if glass is a liquid or not, but the reason many people might think it's a liquid is that intentional selection bias when fitting the panes of glass.
The whole concept of glass possibly being a liquid though changed the way I perceive solid, liquid, and gas states. Those labels better reflect much more temporally localized potential change and interaction than they do to uniquely describe matter.
BTW, if there is an expert, is glass actually a liquid or a solid?
TA: The flux is S for an infinite sheet.
Me: How? We have S for this side plus S for the other which yields 2S!
TA: For an infinite sheet, there is no other side.
Me: O_O
At least that's my pedestrian interpretation :)
Then they add 1 meter to the rope (it is now longer by a meter) and spread it around the earth uniformly (it hovers above the earth, everywhere at the same distance from the earth)
Estimate that hovering distance.
Try yourself to estimate it, then make the calculation.
Long ago the South American and African continents were one. To think of it, there is still a major connection!
Since entropy is a statistical quantity, the second law of thermodynamics is a statistical statement. And because modern physics essentially deals with Hamiltonian systems, it can be proven that a time exists when entropy goes down again. The intuitive proof is really nice. Since energy is conserved, one can imagine the global state (position, momentum) as position in a park covered in snow. So someone walking through it will eventually walk over his own footsteps. Not precisely but it's arbitrarily close, the longer one waits.
https://en.wikipedia.org/wiki/Poincaré_recurrence_theorem
I really like that theorem
I just remember as a child I thought it was strange, then in high school physics I saw how laser light was always grainy, and even things like the solidity of matter can be thought of as optical illusion (caused by the wavelengths of visible light casting a well-defined shadow).
Then later I got into photography and realized what you can do with even a little knowledge about light and optics. I still have a sense of wonder about it even though I'm an average shooter at best.
Hope that all made sense.
https://photo.stackexchange.com/questions/99407/what-is-the-...
This is one of my favorite PBS clips from the 80's in which Richard Feynman explains how strange the nature of light and by extension all of electromagnetic radiation.
https://www.youtube.com/watch?v=FjHJ7FmV0M4
If you listen carefully, you notice that he never talks about wave/particle duality (because he wasn't giving a classroom lecture).
What he does talk about is an electric field that waves slosh around in, and that something "elaborate and complicated" is going on at a deeper level.
That's what I'm on about, if you were pressed to explain it so that a bright child would get it, how would you do that?
e.g.
"Due to the gradual slowing down of Earth's rotation, a day on Earth will be one hour longer than it is today"
"From its present position, the Solar System completes one full orbit of the Galactic Center"
"All the continents on Earth may fuse into a supercontinent (Pangaea Ultima, Novopangaea, or Amasia)"
"Tidal acceleration moves the Moon far enough from Earth that total solar eclipses are no longer possible."
"the Andromeda Galaxy will have collided with the Milky Way, which will thereafter merge to form a galaxy dubbed "Milkomeda" ... There is also a small chance of the Solar System being ejected. The planets of the Solar System will almost certainly not be disturbed by these events"
"time until stellar close encounters detach all planets in star systems (including the Solar System) from their orbits"
"time until those stars not ejected from galaxies (1–10%) fall into their galaxies' central supermassive black holes. By this point, with binary stars having fallen into each other, and planets into their stars"
"estimated time for rigid objects, from free-floating rocks in space to planets, to rearrange their atoms and molecules via quantum tunneling. On this timescale, any discrete body of matter "behaves like a liquid" and becomes a smooth sphere due to diffusion and gravity"
"... they [Positrons] find a distant electron to pair with and the two enter into a highly excited state of positronium, with a radius larger than the current universe. Over the next 10^141 years they will gradually spiral inwards until they finally annihilate"
"time until a supermassive black hole with a mass of 20 trillion solar masses decays by Hawking radiation ... marks the end of the Black Hole Era. Beyond this time, if protons do decay, the Universe enters the Dark Era, in which all physical objects have decayed to subatomic particles"
"... time for all nucleons in the observable universe to decay ..."
"... estimated time until all baryonic matter in stellar-mass objects has either fused together [into iron-56] ... or decayed from a higher mass element into iron-56 to form an iron star"
"Estimated time for a Boltzmann brain to appear in the vacuum via a spontaneous entropy decrease"
"estimate for the time until all iron stars collapse into black holes ... which then (on these timescales) instantaneously evaporate into subatomic particles ... Beyond this point, it is almost certain that Universe will contain no more baryonic matter and will be an almost pure vacuum until it reaches its final energy state ..."
"Because the total number of ways in which all the subatomic particles in the observable universe can be combined is <big number> a number which, when multiplied by <big number>, disappears into the rounding error, this is also the time required for a quantum-tunnelled and quantum fluctuation-generated Big Bang to produce a new universe identical to our own ..."