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A scientific fact/tidbit you recently learned that you thought was interesting

Wudang said:
I just read a social media post stating that sharks are older than Polaris, the north star. I know a bit about evolutionary timescales and stellar evolution and I'm still regoogling the numbers. Some 200 million years versus 70. I'm not sure why this has blown my mind.
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I imagine that's 70 million years? Or else that would indeed be mindblowing.
 
Ziggurat said:
For human purposes, electrons occupy most of the volume of their orbits, so no, that's not correct in any generally useful way. The ways in which it is true are the fringe cases.
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Fair enough, but how much of an atom's total volume is that? What's the gap between, say, the electron and the proton in a hydrogen atom?
 
ahhell said:
Which is why, one day, if I try hard enough, I'll totally pass through the door without opening it. The constant banging and cussing is getting on the neighbors' nerves though.
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You could, in fact, quantum tunnel through the door. The chances of you doing so are so ridiculously small that you'd have to wait many, many times longer than the current age of the universe for it to happen.
 
Thing is: I don't see a big advantage of maglev over high-speed train: in most places, urban density is so high that a maglev wouldn't be able to get up to speeds that make a difference, and drag is the main energy drain, not friction.

And it makes sense anyway to separate Freight and Passenger tracks.

but then a School of Engineering in Munich still trying to make Hyperloop work, even though it obviously wont.

https://www.asg.ed.tum.de/en/asg/research-and-innovation/topics-projects/tum-hyperloop/
 
arthwollipot said:
You could, in fact, quantum tunnel through the door. The chances of you doing so are so ridiculously small that you'd have to wait many, many times longer than the current age of the universe for it to happen.
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You would not go through the door. What would happen is that you would be on one side of the door or the other. Never in the door.
 
arthwollipot said:
You could, in fact, quantum tunnel through the door. The chances of you doing so are so ridiculously small that you'd have to wait many, many times longer than the current age of the universe for it to happen.
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Well, if you are a hero, you will definitely get through on the other side of the door. Heroes thrive on impossible odds. T. Pratchett thought it is because they attract a particle called narrativium that is not currently accommodated in the standard model.
 
GlennB said:
Fair enough, but how much of an atom's total volume is that? What's the gap between, say, the electron and the proton in a hydrogen atom?
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I'm reminded of a passage from Loren Eiseley's The Firmament of Time, in which an elderly physicist began to take the idea seriously, and began walking around with huge padded slippers to help prevent falling through the interstices of matter.
The pulsing rivers of his blood, the awe-inspiring movement of his thoughts had become a vague cloud of electrons interspersed with the light-year distances that obtain between us and the further galaxies. This was the natural world which he had helped to create, and in which, at last, he found himself a lonely and imprisoned occupant. All around him the ignorant rushed on their way over the illusion of substantial floors, leaping though they did not see it, from particle to particle over a bottomless abyss. There was even a question as to the reality of the particles that bore them up. It did not, however, keep insubstantial newspapers from being sold nor insubstantial love from being made.
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GlennB said:
Fair enough, but how much of an atom's total volume is that? What's the gap between, say, the electron and the proton in a hydrogen atom?
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In the ground state, there is no gap between the electron orbital and the proton in a hydrogen atom. The nucleus isn't a node. The orbital extends all the way to the nucleus, and in fact is most dense at the nucleus. And even for excited states where the nucleus is a node, it's only actually zero at the center, it's nonzero an any point away from the center no matter how close. You could calculate a gap if you assume that below some probability density the electron might as well not be there, but even then that's only for excited states in hydrogen. For ground states, you won't get any gaps, and for higher Z elements you won't have any gaps even in most excited states, because a gap in one orbital can still be filled by others.

tl;dr: Electron orbitals occupy the entire volume of an atom, there's no empty space inside.
 
rjh01 said:
You would not go through the door. What would happen is that you would be on one side of the door or the other. Never in the door.
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That's... not quite true. In order to quantum tunnel, the wave function has to be nonzero inside the barrier. So in a sense, it is inside the barrier. It kind of looks like teleporting from one side of the barrier to the other because there may not be any point in time where the wave function is primarily inside the barrier, but you still can't tunnel without being inside the barrier at least a bit.
 
arthwollipot said:
You could, in fact, quantum tunnel through the door. The chances of you doing so are so ridiculously small that you'd have to wait many, many times longer than the current age of the universe for it to happen.
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So, you're saying there's a chance!
 
Ziggurat said:
Sort of. They use the existing track, but they have to basically build an additional track on top of it for the maglev capability. So it can still run traditional trains on the same lines, and don't need to take land for new tracks, but there's still going to be a big infrastructure cost for the new track.

I'd like to see them testing a curve, not just a straight shot. Cool if it works at a reasonable price, but too early to tell.
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What happens when the very fast magelv train getsstuck behind a regular train?
 
steenkh said:
Well, if you are a hero, you will definitely get through on the other side of the door. Heroes thrive on impossible odds. T. Pratchett thought it is because they attract a particle called narrativium that is not currently accommodated in the standard model.
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Cannonically, Narrativium doesn't exist in roundworld. :(
 
theprestige said:
On the atomic level, matter is mostly force fields occupying significant and contiguous volumes. If it were mostly space, things would be sifting through each other all the time.
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The way I learned it (which Ziggurat has pointed out is an oversimplification to the point of being misleading or probably just outright wrong) it is the electric fields of the atoms repelling each other that prevent that from happening.
 
Came across a new term: "non-quantum entanglement"
Not entirely sure what it means.
I've heard a fair bit about quantum entanglement. Two particles become "entangled" in a way that measuring a property of one of the two reveals information about its counterpart.

https://scitechdaily.com/350-year-old-theorem-reveals-new-properties-of-light/

The work, led by Xiaofeng Qian, assistant professor of physics at Stevens and reported in the August 17 online issue of Physical Review Research, also proves for the first time that a light wave’s degree of non-quantum entanglement exists in a direct and complementary relationship with its degree of polarization. As one rises, the other falls, enabling the level of entanglement to be inferred directly from the level of polarization, and vice versa. This means that hard-to-measure optical properties such as amplitudes, phases, and correlations – perhaps even those of quantum wave systems – can be deduced from something a lot easier to measure: light intensity.
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Is "non-quantum entanglement" just normal everyday entanglement, like a fly becoming entangled in a spider's web, or a country becoming entangled in a foreign conflict?
 
As I found out when I severed mine...

The palmaris longus tendon in the wrist is the most useless tendon in the human body. It's so useless in fact that 14% of people don't even have one. It's used by monkeys to let go of branches quickly.

It's attached to the palmaris longus muscle in the forearm, so when the tendon is cut, like mine is, the muscle just sits there, attached to nothing and doing nothing.
 
arthwollipot said:
As I found out when I severed mine...

The palmaris longus tendon in the wrist is the most useless tendon in the human body. It's so useless in fact that 14% of people don't even have one. It's used by monkeys to let go of branches quickly.

It's attached to the palmaris longus muscle in the forearm, so when the tendon is cut, like mine is, the muscle just sits there, attached to nothing and doing nothing.
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That's the one you can see when you have your hand palm up, bend your wrist back, and touch your thumb and pinky finger together. I have it one one side but not the other. (And no, this is not a "Did you know there's no entry for 'gullible' in the dictionary?" trick.)
 
alfaniner said:
That's the one you can see when you have your hand palm up, bend your wrist back, and touch your thumb and pinky finger together. I have it one one side but not the other. (And no, this is not a "Did you know there's no entry for 'gullible' in the dictionary?" trick.)
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That's the one. I can demonstrate that move with my left hand, but no longer with my right.
 
arthwollipot said:
As I found out when I severed mine...

The palmaris longus tendon in the wrist is the most useless tendon in the human body. It's so useless in fact that 14% of people don't even have one. It's used by monkeys to let go of branches quickly.

It's attached to the palmaris longus muscle in the forearm, so when the tendon is cut, like mine is, the muscle just sits there, attached to nothing and doing nothing.
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I'm sorry to hear that. I don't think I could function in modern society without being able to let go of branches quickly.
 
arthwollipot said:
As I found out when I severed mine...

The palmaris longus tendon in the wrist is the most useless tendon in the human body. It's so useless in fact that 14% of people don't even have one. It's used by monkeys to let go of branches quickly.

It's attached to the palmaris longus muscle in the forearm, so when the tendon is cut, like mine is, the muscle just sits there, attached to nothing and doing nothing.
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Apparently it is often used to repair tendons elsewhere in the body.
 
More historical than scientific:

There are exactly fourteen countries in the world that never in their history got invaded by England.
 
The Great Zaganza said:
More historical than scientific:

There are exactly fourteen countries in the world that never in their history got invaded by England.
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From what I can doscover, that's not entirely true.
For a start, it's 22, not 14.
Also, Britain, not England- there's a difference, you know.
More importantly, though, the counting is highly suspect. Included in that list, for example, are Spain and Portugal. Britain landed troops to drive out Napoleon: that hardly counts as an invasion. The British never invaded Poland, except again as part of the Napoleonic Wars (naval blockade of Danzig), and that was to defend Poland. I could go on, but I'm sure you get the point. The source for this claim is an author called Stuart Laycock, who presumably massaged the figures in order to sell his book.
 
I have some anxiety over the size of the Black Hole of my Milky Way when I have to watch galaxies that are hung like TON 618 ...
 
steenkh said:
I was at a lecture last Thursday where a cosmologist told us that all supermassive black holes are rotating at the maximum speed possible, and that it seems to be an important fact for the formation of supermassive black holes.
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It seems logical since the more compact you make a massive object, the faster it will spin if it had any spin to begin with. Neutron stars spin very fast, so presumably black holes will spin even faster.

Here's a question that occurs to me though: If all galaxies have supermassive black holes at the center, does the spin of the SMBH match the plane and direction of the galaxy? Or could it be eccentric to the galactic plane or even spin in the opposite direction?
 
Puppycow said:
Here's a question that occurs to me though: If all galaxies have supermassive black holes at the center, does the spin of the SMBH match the plane and direction of the galaxy? Or could it be eccentric to the galactic plane or even spin in the opposite direction?
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A few galaxies have been found without a supermassive black hole. But we have found so many galaxies with SMBHs that we suspect that these galaxies have lost their SMBH in some way, like if it has been kicked out in an encounter with another galaxy.
 
I found out that I can jolly well stop buying the most expensive headsets and sound cards, because my hearing stops somewhere below 11KHz anyway. So, you know, I don't really need the sound card to be doing 384KHz accuracy anyway :p
 
Blasphemer! Bigger numbers are better. duh...what you've never seen Spinal Tap? Besides, what about consideration for dogs and bats? Don't be a species-ist.
 
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