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.
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.
On todays episode of: University degree or autism?
The space between atoms starts to expand faster than the speed of light. Well i guess that is the universe fucked.
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.
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.
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.
But space contracts at close to light speed,so your analogy isn’t perfect, right?
No, time contracts, not space.
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Well, nothing (with nonnegative mass) can move faster than light through space. Space itself can do whatever it wants to.
Well, the thing space is moving into and across. Or the nothing.
I don’t know why maybe the painkillers are speaking but I have to ask, does farts count as negative mass?
I’ll take my leave…
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Okay … enjoy your painkillers, man.
Incoming vibe killer: no, farts do not count as negative mass. They do in fact have positive mass. You will weigh ever so slightly less after farting. And, in theory, if you were in a frictionless environment, you could propel yourself by farting, because the fart’s mass would act as a reaction mass and propel you like a (very weak and stinky) rocket.
Negative mass would be a very weird thing that breaks physics in a lot of ways, and probably isn’t physically possible in the first place. Allowing faster-than-light travel is only one of many stupid ways negative mass would horribly wreck all known physics.
Thank you for the explanation.
The universe is mostly nothing. So obviously the universe, being nothing, expanding faster than the speed of light isn’t surprising, as nothing is faster than light. 😌
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
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.
Thank you! I used this weird thought to wipe my brain from other weird thoughts, it needed that.
Explanations why space expands are way more crazier than this.
That’s so no matter how much knowledge we gain we can never escape the bad place to kill the Demiurge.
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
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.
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
Well duh. When a thing moves away from another thing, that is moving at the speed of light, at the speed of light, you have speed of light time two!
Since nothing can move faster than the speed of light doesn’t it also mean that the universe cannot be expanding faster than 2c either?
Not necessarily.
The expansion of the universe here doesn’t necessarily mean matter moving faster than light.
Think of the universe as a 3+1 dimensional ballon - specifically, the 3D space we occupy is the 2D surface of the balloon. As you blow air into the ballon, that 2D space expands.
Now, it’s a simplistic example mainly because we’re three dimensional beings and thus can’t easily wrap our heads around a 4D space where one of the surfaces is three dimensional. You run into the same issue as e.g. trying to visualise a tesseract (a four dimensional cube). So a balloon has to do.
And since this expansion of our universe technically happens outside of it, the general laws of physics - such as the speed of light - do not apply.
That’s what I meant. Since matter isn’t moving at the speed of light, if we assume the universe expansion is due to the movement of its edge objects, then it cannot expand faster than 2c. If the expansion is happening for a different unrelated reason than the edge objects ofc that’s something else
Your presumption that there’s an “edge” is at fault here. Consider the surface of the ballon (or rather- a bubble) - it’s continuous, just like our universe. And that’s why it’s hard to explain how a 3D space can expand seemingly without a center point - because said center point is not within the constraints of this 3 dimensional space, just like how the center of a balloon or bubble is not on the two dimensional surface but in the center.
so just like the surface of an expanding bubble, the expansion of our universe doesn’t happen in a plane we can conceptualise easily - it’s a 4 (or possibly more!) dimensional expansion, of which we are just the surface, therefore the expansion appears as if everything literally drifted away from everything - which should be impossible in a 3D space but not when you add a fourth axis.
I don’t know much about astrophysics, but it seems to me the analogy breaks down. Unlike a balloon, the universe does not move on a medium, so the only way to surmise it’s size is by its edges (i.e. the objects at its farthest edges). So the important thing here is how fast those edges move (the dots, on the balloon) which can never be higher than the speed of light. What am I missing?
You’re still missing the 2D to 3D translation…
Think in two dimensions. The surface of the balloon is the two dimensions - X and Y axes. The “medium” (the rubber of the balloon) is the fabric of the universe.
The two dimensional space - much like e.g. the surface of the Earth - has no edges. When the balloon expands (on the third dimension, which the surface dwellers are unaware of), all the surface notices is that any two or three or N points have gotten further from each other. The size of this 2D plane thus can be described by a single dimensional number - the circumference of the balloon (aka "how long does it take to get back to the starting point in the 2D space if you go in any direction).
You need to extrapolate this continuous 2D surface on a 3D object to a 3D surface on a 4D object. In a four dimensional space, our universe has a four dimensional volume it consumes - but in 3D, it’s effectively infinite (curving into itself, much like the surface of the balloon), but also expanding (everything is being further and further from each other).
To grasp this I’d recommend you read the book Flatland by Edwin Abbott - it’s a 140 year old study in the format of a novel, on how beings from an N spatial dimension plane would “see” and interpret a being from an N+1 spatial dimension (in this case, 2D beings, like a square, seeing 3D being, a sphere, intersect with its 2D plane). Mind you it’s also a social satire so you’ll find a ton of social commentary of the Victorian era Britain, but the core conceptualisation is there - an N spatial dimension being will always have trouble visualising an N+1 dimension.
So again, in our 3 dimensional plane, the universe has no edges, it’s infinite, yet expanding. Just like how the surface of a balloon or bubble has no edges, or how the surface of the Earth has no edges - but in a 3D space you can create a bounding box to define its size. Our 3 dimensional universe is essentially the surface of such a 4D bubble, but that fourth dimension is outside of our universe therefore it can’t easily be measured directly. Just like how a dot on the surface of the balloon couldn’t measure the 3 dimensional space of the balloon, only by inference of the expansion, theorise that it actually exists in a 3 dimensional system but is limited to the 2D surface of said balloon, and infer its mechanics based on the expansion of space between any two points on the surface.
Well, ok I’m afraid I’m really out of my depth here. It seems to read like the universe is expanding due to an unknown force acting on the 4th dimension (like the air coming in the balloon), but I can’t imagine what that would be. I always understood that the universe expansion is simply leftover momentum from the big bang
Nothing within the known universe moves faster then light, but the universe itself expands faster then light travels within it.
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.
You also need to consider what the things inside it look like to you or anyone else. The observable universe is the volume inside which light can reach us here on the earth… technically it’s different for everyone because we’re all in a slightly different position, making everyone the centre of the universe, but in terms of the scale of the universe, that’s irrelevant levels of accuracy and you can safely state that everyone on earth is in the same place. Now because space is expanding and carrying stars and galaxies with it, those galaxies will eventually pass the point where their light could travel for an infinite time and never reach us, in other words, they would pass beyond the edge of our observable universe. Eventually, given enough time, all that will be left in the night sky (long after the earth is destroyed) will be our galaxy, and possibly bits of our local group, which are gravitationally bound and would hold their relative positions as space expands around them.
How to tell people you don’t know more than school level basic science: the person who made that image and OP making this thread.
All you did was write “hey, I don’t comprehend things that are easily learned and have been freely available to learn from your own home via the Internet for several decades” on a sticky note and put it on yoir forehead, then went into a public place for everyone to see and somehow didn’t realise you did any of that.
First of all, there is absolutely nothing wrong with having a “school level basic science” (nice grammar mate). Most people are of average intelligence and education. Who are you to shame the average person?
Second of all, shut the fuck up. You’re being elitist over a young person learning science. You’re a cretin.
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.
