Shadows can move faster than light.
No they can’t, because they aren’t moving at all. That vsauce video pisses me off so much and I’ve debunked it more than once over the years, but suffice to say, you could claim light moves faster than light using the same logic he uses for shadows/darkness.
You can compute triangular numbers and factorials using the same logic, doesn’t mean either is wrong, just that you’d be wrong if you tried to compute one in place of the other.
That is not analogous to this. The fact you can measure the same effect using light as using dark should immediately tell you that you aren’t measuring dark at all.
The reality is all you are measuring is discreet points and calling it movement. It’s not movement even in a loose sense. Calling this movement is like calling an animated character running across the screen movement. Just like that is hundreds of individual images that your brain perceives as movement, the light or shadow is thousands of points of light (or, in the reverse, absence of light) that your brain perceives as movement.
If there was a ring around the earth and you shine a laser pointer at it and rotate 360 degrees you could measure insane “speeds” of the dot moving along the ring. By the same logic his video uses you can claim to have invented teleportation and essentially infinite speed by turning the light off, moving it, and having the light or shadow be in another location when you turn it back on. Hopefully that really illustrates how much these are individual “things”, not things “moving”.
The photons making the light, or with the shadow, the photons being blocked, are not the same photons that were making the initial point. They are new ones in a new location.
I remember finding out the shape of space isn’t a vast plane of emptiness, but more of an ever growing sphere and that messed me up.
As far as I know, not even that is certain. I read something about other topologies, like a donout shape or even higher dimentional topologies being plausible as well. Interesting rabbit hole but really makes you question our how we view our reality.
Preemptive explanatory note: the speed of light, approximately 300,000 km per second, is the highest speed that something can move through space.
The expansion of space doesn’t happen at a set speed. It happens at a rate of approximately 70 km per second per megaparsec. So if you’re measuring two points half a megaparsec away from each other, then every second, the space between them grows by about 35 km. If you’re measuring two points 2 megaparsecs away from each other, then every second, the space between them grows by about 140 km.
If you’re measuring two points 4300 megaparsecs away from each other, then the spacetime between them grows by about 300,000 km every second. That’s not to say that anything is moving at 300,000 km per second, there’s just more space between them every second
just more space between
Space out of thin air… tell me, mate, can I sell it?
NFT’s sold, so probably yes
Beautiful! That’s the kind of perfect explanation I was trying to come up before giving up and just saying the expansion doesn’t have a speed because it isn’t motion, which is only partially correct lol.
This guy expands!
Moving is just putting more space between you and something. If it walks like a horse, talks like a horse, bites like a horse… you get the idea. It’s not clear to me why the increase of inbetween space in cosmic inflation “gets a pass” whereas the increase of inbetween of space from movement doesn’t
Wtf is a megaparsec? It’s a million parsecs. Tf is a parsec? A parallax arcsecond.
…Tf is a parallax arcsecond?
An attempt at an explanation for the layperson
Imagine you’re standing outside. In front of you is a tree and behind that on the horizon is a mountain. You move 10 ft to your left, and the tree looks like it moved to the right, but the mountain looks like it hasn’t moved at all. That’s parallax. The closer something is, the more it appears to move when you move.
Imagine you are the pivot point on a big protractor. Your field of view can be divided into 360°. Every degree can be divided into 60 parts, called arcminutes. Every arcminute can be further divided into 60 arcseconds. Each arcsecond is 1/3600 of a degree.
How do these fit together? There’s one more thing I need to explain.
The earth orbits the sun at around 149.6 million kilometers. That’s called an Astronomical Unit. A parsec is the distance that an object would have to be, so that moving one Astronomical Unit would make it appear to shift sideways by 1 arcsecond.
Fraser Cain did a better job explaining, because he can use pictures
It’s 3.26 lightyears.
Quantum entanglement is faster than light
Nope. Quantum entanglement is when two particles are made to have the same states. Measuring one tells you about the other one in much the same way you can tell what someone you’ve never met before looks like if you’ve seen their identical twin. Also, much like how punching one twin in the face and breaking their nose has no effect on the other twin fifty miles away, doing something to one half of an entangled pair does nothing to the other. In fact, because they’re no longer identical, the particles aren’t considered to be entangled anymore.
Entanglement can be used for encryption, but it can’t be used to transmit data.
Nope!
Information can only travel at the speed of light.
During my undergraduate CERN did this experiment (a decade ago now).
And they had the shocking result of the second wave function collapsed faster than c.
That was until a clock was found to be loosley connected and caused a timing error, that would account for the slower than c speed.
Information can only travel at the speed of light.
I like the general term being used nowadays instead of “the speed of light” - the speed of causality; which is nice because it fits neatly into E=mc2.
That’s so no matter how much knowledge we gain we can never escape the bad place to kill the Demiurge.
We should probably use the word “growing” instead of “expanding”, would that be easier to follow 🤔
no
besides the expansion of spacetime which is the correct answer, there’s also nothing keeping two objects from traveling in opposite vectors each at 60% c. Frame of reference matters too
The very short, very bastardized version is that as objects move at speeds closer to the speed of light, the way everything else around them appears to be shaped and moving changes. A “stationary” object you pass seems less long than it should in the dimension parallel to your travel. The net result is that however two objects are moving relative to each other, their own speeds warp their experiences of the universe such that nothing else is observed to be doing something “illegal”.
There actually are things keeping that from happening but I don’t want to get into it
I may be wrong, it’s been a while since I looked into relativity. But I think it’s possible from an outside perspective to see 2 objects that have a velocity relative to each other that is faster than the speed of light.
If 2 spacecraft travel in opposite directions at 60% of the speed of light from the earth it would appear that they are traveling away from each other faster than the speed of light. From either ship it would not appear that the other ship was traveling faster than the speed of light however.
Yeah that’s correct. If things couldn’t move apart from each other faster than the speed of light from a 3rd party observers perspective, light itself would make no sense. Either all light would actually be travelling at half the speed of light, or half the light would be frozen.
No, spacetime doesn’t expand faster than light at any point. Its just that as you accumulate the new growth over a long distance, the farther objects appear to move away faster than light from our position.
you running vs a train vs you running on a train vs measuring two people running away from each other on two trains travelling in opposite directions
Take a balloon.
Blow it upto about 50mm
Make a couple dots around it
Blow it up a little more.
Now there’s distance between the dots.
Imagine an ant walking between the dots. That ant is going at the speed of light (as fast as it can go) relative to the dots.
Now as it walks between the dots, blow the balloon up really big
The dots aren’t moving, they’re stuck to the surface of the balloon. The balloon itself is expanding. The ant is going at the speed of ant-light, but now the dots are all “moving away” faster than the ant can walk.
The speed of the ant hasn’t changed, the space the ant is traveling has changed. And faster than the ant can move, because the balloon isn’t limited by the same things the ant is.
But space contracts at close to light speed,so your analogy isn’t perfect, right?
No, time contracts, not space.
Thanks for that that’s actually a really helpful analogy.
I mean i still dont understand. Brain hurty. But thanks anyway
Things cannot move through space at a speed faster than lightspeed.
This rule does not apply to space itself.
Also, interestingly, shadow boundaries can ‘move’ faster than the speed of light.
https://www.iflscience.com/shadows-can-move-across-a-surface-faster-than-the-speed-of-light-75112
Because a shadow isn’t truly a ‘thing’.
Its just an area where light bouncing off of something is not happening (as much).
The space between atoms starts to expand faster than the speed of light. Well i guess that is the universe fucked.
How fast space expands is described by general relativity. For the space between atoms to expand faster than the speed of light, you need a shitload of energy crammed together very densely, like a galaxy worth of stuff in every atom. This is called cosmic inflation, and it’s what happened during (and possibly before) the first part of the big bang.
We don’t know exactly how there can be this much energy in this little space, or where it all went, but we do know it was there because there are waves imprinted on the density of the universe.
Good thing the atoms (and the subatomic particles) are pulled back together as the universe expands. The same way we are pulled to Earth by gravity and don’t fly off into space as the universe expands.
This does, however, lead to the existence of “local groups”.
Meaning that, there is a local group of celestial bodies that we may theoretically be able to visit at some time in the future, which are held somewhat together by gravitational forces which help to counteract the expansion of space. But anything outside of that local group will be expanding away from the group at greater than the speed of light.
Meaning, effectively, that the universe is going to be / is already separated out into small pockets of local neighbors, who will never be able to reach other local groups unless they invent some sort of much faster than light travel. The universe is very, very large, but the percentage of the universe that is physically reachable by us is quite small, no matter how many generations we spend on the journey.
Personally I find that to be one of the more disappointing true facts about the universe.
Exactly, there will be causally disconnected pocket universes in the future. I’m thankful we still live in a time when we can see the rest of the universe. Creatures alive in 100 billion years might have no way to figure out how the universe started, or that there is anything outside of their local cluster at all.
I’m thankful we still live in a time when we can see the rest of the universe.
Do we though? How do you know our entire known universe isn’t just a local cluster?
If we could see the entire universe, then somewhere in the center we’d be able to point to the origin of the Big Bang. Since we can’t, that implies we’re only looking at a section of the universe analogous to a portion of the surface of a globe.
Someone else already replied probably better than I can, but this is one of my favorite subjects to study.
The big bang didn’t really start in a place, it happened at a point in time. As we look at all of the galaxies around us (minus the close ones we are gravitationally interacting with) they are all moving away from us, so either 1) we are exactly where the big bang took place (vanishingly unlikely) or 2) the big bang happened everywhere and all of space is expanding from that event.
We can actually see the first light ever released in the universe (not from the big bang, as the universe was a dense plasma for the first ~400,000 years until the recombination era) as the cosmic microwave background radiation. And it is (relatively) even in all directions, minus some minor temperature variations.
I highly suggest looking at a channel on YouTube called PBS Spacetime. They have videos going back years and years that dive into great depth on all of these topics!
Yes, I already responded to the other comment. Summarily, I don’t find their argument convincing.
To add, it’s not surprising that everything is moving away from us. To use the other commenter’s balloon analogy, as the balloon expands, so do the circumference and surface area. So any two points on that surface will be moving away from each other as it does so.
It’s also not surprising that the cosmic microwave background radiation appears relatively uniform. 14 billion years of expansion, and we can only observe or “neighborhood” of the universe, mind-bogglingly large as even that is. 14 billion years of moving on a more or less stable trajectory. We can’t see far enough backwards to view the origin point.
Also, if the background radiation came from the big bang, then it would have outpaced us as our galaxy slowed down and the radiation continued moving at the speed of light. This suggests that the background radiation we witness was emitted after the energy that coalesced into our galaxy, and is just now catching up/surpassing us. Unless it’s reflecting off of something further outward, and on it’s way back.
Is there any known pattern to the actual direction of cosmic background radiation? Is it aligned in any way or more or less random?
By the nature of the Big Bang and the expansion of the universe, everywhere is at the origin. That is, if we believe that the universe started out as a singularity, and that the expansion of space itself is what causes that singularity to grow, then every point in the universe originated from the exact same point, and that nothing has “moved”, in the sense that the point itself is expanding. Thus, every place is at the “origin”.
To use the balloon analogy: Draw a small dot on the balloon, that dot is the entire universe as a singularity. Now, inflate the balloon so the dot grows, and try to determine the “origin” of the dot. Of course, you could point to the centre of the dot, but I would argue that if the initial dot is infinitely small (a singularity) then every point on the expanded dot in fact originates from the exact same point.
This does cause a bit of a headache because we’re arguing that a zero-dimensional thing suddenly became 3-dimensional. I’m honestly not sure how astrophysicists reconcile that, but I seem to remember reading that they boil down to saying “we know what happened <some extremely short time> after the Big Bang, but we don’t really know anything about what happened at t=0” per my understanding, even the concept of time breaks down when you go to t=0, so it becomes impossible to get to t = 0 + h.
That doesn’t make any sense, down to the geometric level.
By the nature of expansion itself, there is an origin point somewhere in the center. That holds especially true in the case of uniform expansion.
If “every point in the universe originated from the exact same point” then that origin point is somewhere in the center of the universe, and tracing the trajectories of every point backwards should intersect somewhere very close to that point.
Your balloon analogy supports this thesis. No matter how much the dot expands, the center of the dot is where it originated. Yes, every point on the expanded dot originates from the same point. That point is in the center.
Saying “sometimes physics is mindboggling” in order to rationalize invalid leaps is not a strong argument. Yes, sometimes physics is mindboggling. But that’s no reason to handwave away inconvenient facts whenever we’re trying to argue for something illogical. You need rigorous evidential support to justify a mindboggling conclusion, as is the case with quantum mechanics. Speculative or theoretical physics however cannot simply fill in the gaps with this sort of handwaving.
Honestly, if the concept of time breaks down when you look at t=0, then that only tells me that the idea of t=0 itself is invalid and needs to be abandoned. Especially since there’s no evidential support for that theory, it’s entirely speculative, and has only been justified with the explanation that “We don’t have any better ideas.”
Time didn’t just magically start at some random point before which time didn’t exist. And space didn’t just magically expand into 3 dimensions before which there was only 0. Energy and matter didn’t just suddenly appear without any prior cause initiating some action. All of those things would require violations of the laws of thermodynamics. And in the absence of far more evidence than ever has or even can be found, this “best guess” is full of more holes than many people seem ready to admit…
Without trying to explain things even in not sure I grasp, no. The atomic forces keep atoms together, and expansion of space is only noticeable on long distances. Like light-years and parsecs kind of distances.
Also fun fact: the rate of expansion is not only INCREASING as space expands, last information I saw suggested space is expanding faster in some directions than others, which is fascinating for a number of reasons.
courtney you are going to invent rocket ants knock it off
All we are going to die?
Yes, and actually right now relatively speaking.
Yes
Eventually, the universe itself will “die” when it hits absolute zero and nothing moves anymore. Nothing can happen after the heat death of the universe (unless protons decay)
Finally, some good news.
https://en.wikipedia.org/wiki/Timeline_of_the_far_future breaks this down.
Current data suggest that the universe has a flat geometry
Holyshitholyshitholyshit don’t tell flat earthers
Not unless you donate some seed money to my church. It will come back to you, and then you pay twice as much and then I pay half. And then you, a vulnerable population, gain faith in the process and give more and more and I give less and less but this is just friendly educational propaganda from your friendly neighborhood juggler and CIA spook.
WHOS BLOWONG UP THE BALOON AND WHEN WILL IT 💥
This is a truly great explanation. One worthy of Feynman. Physics degree?
Lmao no, just autistic fascination with space and many thousands of hours of listening to astrophysics lectures and hundreds of hours listening to edu-tainment type videos from people like Dr. Becky Smethurst.
Thanks for the compliment though, I’ve heard the balloon explanation since I was a child, but the ant-splanation of light speed just popped into my head.
Didn’t get it but saving this so when i grow older I’ll see it again and think for the logic behind it… 🗿
A shadow can move faster than light too.
A shadow never actually moves.
Tell that to the Hat Man
Because it isn’t actually a thing
The speed of dark is faster than the speed of light
Light thinks it travels faster than anything but it is wrong. No matter how fast light travels, it finds the darkness has always got there first, and is waiting for it.
Terry Pratchett
I don’t think it is
It actually is.
Distance itself is expanding in the universe. Like two dots on an expanding balloon doesn’t mean there’s less balloon, its just the distance itself that expanded.
And the further something is away from you, the more distanve there is to expand. Meaning it moves faster the farther away it is.
What can not travel faster than the speed of light is ‘information’. So we have to wait even longer for light and information about a distant object to get here.
In the same way that two cars driving away from each other at 60 mph have relative speeds of 120 mph with regard to each other, two bodies moving away from each other at less than the speed of light have relative speeds exceeding it. Everything in the universe is moving away from everything else and sometimes at relative speeds that exceed the speed of light. Nothing is individually exceeding the speed of light in absolute terms.
I fucking hate that aspect of Special Relativity when I did l A-Level Physics (wait, shouldn’t that be “Physic” in the US to go with “Math”?). Two spaceships head off in opposite directions at light speed - from the frame of reference of each spaceship, the other is moving away at C, not 2C, because the Universe would rather slow down time itself than let anything move faster than its stupid precious C!
Wait does that mean theoretically one thing can slow another down by just being an observer if it is also moving in the opposite direction?
It’s pretty complicated and it’s been a while since i read the layman’s-terms no-maths explanations, but think of it like driving
You’re in a car looking at another car which is driving at the same speed on s road which is parallel to you. You’re both going to look like you’re driving at the same speed and travelling the same distance
Now say that rather than being parallel the roads are at an angle to each other. Say 45 degrees. Now when you look at the other car, even though its Speedo will say the same as yours it’ll look to you like it’s going slower and it’ll fall behind you. After a while you won’t be able to see it out of the drivers side window and will have to look through the back seat window and then the rear window to see it
And the experience in the other car will be the same - they’ll see you as going slower and falling behind them
Nobody’s speed has actually changed, it just looks different from each car’s perspective
If you can mentally change “difference travelled” to “time passing”, then that’s how to conceptualise it
Relative speeds also cannot exceed the speed of light. Since there’s no absolute reference frame, if this were possible it would be no different than exceeding the speed of light on “absolute” terms. Once you get up to speeds where this would matter, funny dilation effects that I’m too dumb to understand would prevent this.
Cars are not driving away from each other at more than the speed of light relatively. The road is stretching faster than the speed of light.
Yeah, but wouldn’t this lead to the cars perceiving each other as moving faster than light?
No, because the space is expanding faster than light, the light can’t bridge the gap and so you and the other car simply can’t perceive each other at all.
That’s intuitive but actually completely wrong. There is no “absolute” reference frame, and nothing can move faster than light in any relative reference frame.
The only thing that gets around that is the expansion of space itself. It’s not that the objects are moving away from each other, it’s that the distance between them is expanding, causing them to become farther apart.
The best analogy is to picture an ant crawling on the surface of an expanding balloon.
Okay but the ant can still only go at the speed of ant.
Exactly! That’s why we have a concept of observable universe.
As the universe expands (think of it not as ants moving, but more space created between ants as balloon gets inflated), at some distance away from us it starts doing so faster than light.
The light, however, can only travel at, well, the speed of light. As such, we will never see or reach anything that is beyond this light speed horizon. And as the expansion of the universe speeds up, more and more objects that we can still observe will disappear beyond this point.
Fuck it, question that I had since 10 years old.
if I have a very long stick, and I flick it. what would happen to the tip? what if a laser pointer is used? at a certain distance, the beam would be moving (sideways) faster than light.
it might work better with a whip rather than a solid stick.
The end of the stick would respond at the speed of sound travelling through the medium of a stick.
As for the laser pointer, the thing that’s moving faster than light isn’t really a moving thing any more than something appearing in a 24fps film is moving, if you know what I mean? It’s just an abstract notion of a moving dot. The light that comes back to you from above isn’t the same light that’s come back to you from below.
Now I wish I had a nice big wall about a light second away and a massive laser to draw things on it.
Bonus: angle the wall so that the left side is a light second and the right side is a light minute away. Alternate the laser on/off.
Good news! We do have a nice big wall about a light second away! Hard to find a laser that’ll make a visible dot on the moon, though
Lovely how xkcd seems to have the answers to life and its mysteries.
but how will it look like?
for a short scale it’ll be a straight line. but a few light years away? where the abstract dot is moving faster than the speed of light? what shape would you see? definitely not a straight line. and definitely some time issues. like it’ll hit you and then you’ll see it hit other planets you’re left and right?
Think of it like a hosepipe. You’re on the lawn with s long stream of water coming out of the hose. If you flick it quickly it doesn’t stay in a straight line. The beam of water curves as you move.
Because the beam of water isn’t an object. It’s a stream of particles which are constantly being emitted from the tip of the hose
Same thing with a laser beam. It’s a stream of photons being emitted from the laser. If you flick the laser, the photons which have already been emitted will continue in a straight line. Any which are emitted during the flick will head off in a straight line in the direction the laser was pointed. End result:a curved beam
that makes sense, but I’m trying to imagine how that beam would look like a few light years away before it hits you, when it hits you, and after.
That’s where things get weird. The tip won’t exceed the speed of light. You could have a section near you moving at the speed of light and the tip will also be moving at c, because c is the limit.
If you were on a train moving at 100mph, and threw a baseball at 50mph in the direction of travel, then the baseball is moving at 150mph. But if you were moving at c and threw that baseball it would not go faster than c.
In fact, everything would move very very rapidly away from the baseball hitting the first air molecule it touches (assuming you yourself have no mass in this scenario).
The tip of the very long stick would still move at sub light speeds. Also, the atoms at the far end will not immediately know what your hand is doing at the other. The forces the atoms make on each other also travel at (sub) light speed.
I guess imagining a perfect unbendable stick would break physics somewhere else.
The Information that the stick has begun to move takes time to travel through the stick. Kind of like bending, but not really.
First question: two reasons that wouldn’t work: the stick would just break, obviously, but if it was a super duper stick, the torque required to accelerate the end past the speed of light is directly related to how long the stick is, so any increase in speed from a longer stick will be offset by the need to apply more force at your end. Therefore the energy required to flick a stick to the speed of light does not depend on the length of the stick, you are simply creating a reverse lever of sorts. It’s still an infinite energy requirement, assuming the stick has mass.
The second question is a lot easier. The light is traveling directly away from you at all times, there is no sideways motion.
It’s actually simpler: the stick will deform because whatever movement you do travels across the stick at the speed of sound of the material the stick is made out of.
Why does it matter how long it takes for the torque to travel down the stick? The question was about the speed of the tip in the orbital direction, not the speed of the wave in the radial direction outward.
I see your point. Still, it shows there’s no such thing as a “super duper stick” because there’d be shearing forces pulling the atoms apart faster than they can move together.
Yeah that’s the boring answer, it would just break apart. But even without physical limitations, mass has the property that it can’t be accelerared past c with a finite amount of energy, and I think it’s interesting to see why that limit is more fundamental than the structure of matter. No matter how you mess with forces using simple machines, the energy calculations always come out the same.
Movement across the stick travels much faster than the speed of sound (which is related to air density).
my personal headcanon is that the universe is a giant living being and we are its fundamental particles or some other infeasibly tiny thing
idk what that has to do with light speed and space-time but you can think of that yourself i guess
Thank you! I used this weird thought to wipe my brain from other weird thoughts, it needed that.
When I was a kid I imagined that our universe and every galaxy in it make up a single atom in another, much larger universe.
That much larger universe, in turn, is also a single atom in a much larger universe. And so on…
Dark Tower did the same bit as well
I have had thoughts like that before! Especially since at school the atomic model that was taught looked like a little galaxy (which I now know is inaccurate) and it seemed like going smaller or going bigger just repeated similiar patterns, so to say.
“As above, so below” is a pattern that’s almost universally recognized for a reason. The galaxy atom model may not be accurate, but lots of things in the world rhyme at different scales.
