What is a science fact that blew your mind when you learned it?

Electrons in a copper wire do not travel at the speed of electricity. Not even close.

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...

Science doesn't "prove" hypotheses - it disproves them.

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.

A compressed spring weighs more than the same spring uncompressed. The moon and earth weigh less together than if you weighed them separately and added the values together. Most of the weight of solid objects is due to the high speeds and binding energies of the elementary particles within them rather than the rest mass of the constituent particles. The number of particles that exist is relative to how fast you are accelerating. Everything that has energy (which is everything we know of) affects the gravitational field; this means that even photons are "attracted" to each other.

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 think "mind blown" is an accurate description when I first saw the Hubble Deep Field image:

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.

Not science, but Mathematics - That there are more ways to arrange a deck of 52 cards than seconds that have elapsed since the big bang took place.

Thousands of similar questions on reddit for anyone interested- https://duckduckgo.com/?t=ffab&q=science+fact+site%3Areddit....

A 2016 poll of 1,500 scientists reported that 70% of them had failed to reproduce at least one other scientist's experiment (50% had failed to reproduce one of their own experiments).

When i could "see" my visual blindspot. https://lasikofnv.com/try-these-3-fun-tests-to-find-your-vis....

It never fails to amuse me that any pressure or force that we intuitively feel is "pulled" by a vacuum, is only caused by air pressure on the other sides of an object.

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.

Ok, so maybe not a "fact" but the hypothesis of the False Vacuum:

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.

Not a fact per se, but: the sheer amount of living things that came before me, in the sense of my direct ancestors and their direct ancestors etc. etc – not only my human ancestors, but the whole of my ancestors all the way back to the origins of life itself – and I would not be here today if even one of them would have died before reproducing... that manages to blow my mind every single time I think about it.

The sun orbits the center of the galaxy every 250 million years, so when the dinosaurs were around, they were on the other side of the galaxy, compared to where we are now.

Gravity travels at the speed of light (the speed of causality). If the sun suddenly disappeared, the earth would continue orbiting around where it used to be, for about 8 minutes.

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.

The selective attention test, aka the "invisible gorilla" experiment, and the finding that 50% of people didn't see the gorilla.

I was pretty amazed by the Casimir Effect when I first learned of it.

  https://en.wikipedia.org/wiki/Casimir_effect

A gallon of gasoline creates 20 pounds of carbon dioxide.

So my trip to the grocery store could be adding as much carbon dioxide to the air as the groceries I pick up!

The dual slit experiment. Run the experiment with no one watching it, it produces result A. Run it again and watch it, it produces result B. Watching the experiment changes the result. WTF????

I absolutely cannot psychologically deal with the Monty Haul paradox. https://en.wikipedia.org/wiki/Monty_Hall_problem I've coded it multiple times in multiple programming languages as a cathartic exercise. Despite seeing the results obviously printed out in a console in front of me, I just can't handle it. I lose SAN just thinking about it.

That when we look up at distant stars, nebulas, & galaxies and the like...we are looking back in time. What we see could have been gone for decades, centuries, or longer.

Growing up, I was taught that the main reason why it's bad to drink is because it kills brain cells and brain cells don't grow back. Apparently that is not the case anymore:

https://www.scientificamerican.com/article/the-adult-brain-d...

Not a science fact per se: Until recently I haven't realised the amount of damage inflicted by religion or in the name of religion if you will, to our species. Take Heliocentrism[^1] for example, it was alluded in the 5th century BC that the Earth revolves around the sun and that stars are other "suns". Then religion came along. Galileo nearly died for re-iterating a theory that was accepted by part of the scientific community nearly 2000 years before him.

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.

[^1]: https://en.wikipedia.org/wiki/Heliocentrism

Only 10% of the cells in a human body are human, but that 90% is only 2-3% of human body weight. https://www.nih.gov/news-events/news-releases/nih-human-micr...

How prion diseases work and spread. They're basically infectious lego. You may not thank me if you read about them...

The physics & biology behind eyesight.

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.

Obvious when you think about it, but I didn't realise for ages that all the planets orbit in the same plane.

The gold in my wedding ring was formed inside a star. I kinda sorta knew all matter was formed inside stars but it never really clicked until I thought about something as simple as a lump of gold and where those atoms really originated.

BTW, "it takes a photon over 100,000 years to exit the Sun" is misleading - it sounds like there's a single photon that's generated deep inside the Sun's core and winds its way through like a cicada until it emerges at the surface.

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 there is such a thing as deterministic chaos (aka the butterfly effect), ie. infinitesimal perturbations can quickly produce macroscopic changes, and all the philosophical implications that result from it.

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!)

we can see our nose all the time, but our brain filters it out.

if you close one eye and keep the other open you'll suddenly see one side of your nose.

Average density of the universe is about 1 proton mass per cubic meter

For me it's material science misconceptions, corrections to what a kid / the over-simplified public conception are. As I'm not a material science expert, if I'm wrong or slightly incorrect please explain what actually happens.

"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?

Information has mass (and thus energy). As in a full hard drive weighs more than an empty one. https://aip.scitation.org/doi/10.1063/1.5123794

In Physics 2 (Light, Electricity, and Electromagnetism), I could not derive the correct answer for calculating the flux of an infinite sheet.

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

The 100-step rule in neuroscience, that states that no primary brain operation (e.g., face recognition) can take more than 100 neuron firing “steps.” (Feldman & Ballard, 1982)

Creating something out of nothing: The Banach - Tarski Paradox

https://youtu.be/s86-Z-CbaHA

That had interactions between protons and neutrons been but a tiny bit weaker or stronger than they are, the universe would probably contain a lot less carbon, nitrogen and oxygen (https://en.wikipedia.org/wiki/Triple-alpha_process#Resonance...), perhaps precluding existence of life as we know it.

Gravity is not really a force or objects "attracting" themselves but a consequence of the curvature of spacetime.

At least that's my pedestrian interpretation :)

I usually ask people to imagine they are putting a rope tight around the earth, following the equator (idealized sphere).

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.

Exactly anything you can think of can be represented as a segment of pi's infinite decimal expansion.

That the Amazon soil is actually very poor in nutrients and the dust from the Sahara desert is actually what keeps the Amazon rainforest alive.

Long ago the South American and African continents were one. To think of it, there is still a major connection!

A man can fast for more than a year without die https://en.wikipedia.org/wiki/Angus_Barbieri%27s_fast

The life cycle of the lancet river fluke: https://www.damninteresting.com/a-fluke-of-nature/

Many statements here:

https://en.m.wikipedia.org/wiki/Timeline_of_the_far_future

That 'normal' matter only makes up 5% of the universe. That some omnipresent dark energy field makes up the majority (63%) of the universe.

From Introduction to Elementary Particles by David Griffiths: a neutrino of moderate energy could easily penetrate a thousand lightyears of lead.

That mitochondria have their own DNA and used to be separate organisms. Or when I heard that trees feed each other and fungi through their roots.

That something trivial like seeing speckle patterns in my eyes when I'm tired is proof of the quantum nature of light.

You always weigh less in the morning compared to the previous night because you have exhaled carbon atoms from your body!

Trees form out of thin air.

Black hole singularity is infinitely dense and zero size

Hot water freezes faster than cold water (sometimes).

This question feels AskReddity

camels have three eyelids

look at the time-lines of the universe and some of the entries, especially the last few, are mind blowing ( https://en.wikipedia.org/wiki/Timeline_of_the_far_future )

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 a number which, when multiplied by , 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 ..."