bendvis t1_j1gnl3b wrote
Reply to comment by polovstiandances in Did you know it will still take 46 billion years to cross the universe at the speed of light? 65 mph = 4.8 * 10^17 years! by NotAndroid545
The common analogy is an ant crawling across the surface of an inflating balloon toward a specific spot. The spot is stationary on the balloon’s surface and the ant is moving toward the spot, but the distance between them is growing because the size of the balloon is growing.
Compare the expanding 2d surface of the balloon to space itself, and that’s why distant galaxies are moving away. Like the spot, they’re maybe not moving, but the distance between us and them is still growing.
polovstiandances t1_j1gofji wrote
Thanks for your reply. So then how can one explain why the rate at which this expansion process happens isn’t a function of the speed of light at all? If the analogy serves, I can only blow a balloon up as equivalently fast as the speed of light, meaning there’s some max distance that can be produced in some time delta between the ant and the target spot, no?
420binchicken t1_j1gq6pn wrote
No, the speed at which the balloon can inflate, or the universe can expand, is not limited by the speed of light. The speed of light is a speed limit for things moving across that space, not the space itself expanding.
polovstiandances t1_j1gqrop wrote
Ok, well that’s like, fucking insane right? Maybe my understanding of the concept of space needs revision because conceptually I believe space to still be an object, and nothingness to be space, meaning that an “object” is still moving across a plane (of nothingness) at a rate. But this isn’t very physical or scientific I guess
bendvis t1_j1grw9y wrote
Imagine a wave traveling through water. Each water molecule doesn’t really go anywhere. It just gets bumped and jostled by its neighbors and it ends up moving in a circle as the wave passes through.
Light is a wave too. It’s a wave passing through the electromagnetic and mass fields in the same way that a wave passes through water. Light is a vibration that propagates through those fields. So, empty space is an area whose fields aren’t vibrating. The fields are still there just like water is still there when there isn’t a wave passing through it.
polovstiandances t1_j1gs4lm wrote
Oh wow, this was a really helpful image. Thank you. Damn I should have studied this shit.
bendvis t1_j1gpibe wrote
The speed at which you can stretch a balloon’s surface and the speed at which an ant walks across the balloon’s surface are distinct and separate things that aren’t related.
The same is true of the speed at which light (or gravitational waves or information in general) propagates through space and the space it’s propagating through. They’re not related.
Keep in mind that space expanding happens ‘faster’ on bigger scales. If 10 cm of balloon distance expands to 11 cm over the course of a minute, then the points that were 10 cm apart are moving away from each other at 1 cm/minute, even though neither point is moving across the balloon in its own frame of reference. If the balloon were enormous with two points 10 light years apart and it expands at the same rate, they’d be moving apart at 1 light year per minute - much faster than the speed of light.
polovstiandances t1_j1gpzu1 wrote
Ok this makes sense. But still doesn’t touch on how fast spade can expand, and whether there is a max limit to that. But I guess you’re saying that yeah, space still cannot expand faster than a certain rate, it’s just that the rate it expands informs a different understanding on the time plane. But space cannot expand faster than the speed of light, right? What I mean is just the raw rate at which the universe is expanding must be some function of an expansion rate even if it causes the amount of total space to exceed the distance achievable by the speed of light, right?
bendvis t1_j1gqo13 wrote
According to one theory, during a time called Inflation, space expanded really fast. The volume of space expanded 10^78 times larger in 10^-32 seconds. That was way faster than the speed of light. This super rapid expansion explains why the cosmic background radiation is so nearly perfectly even - because at that time in the early universe, it was all in one point. If there is a limit, it would have to be faster than that.
polovstiandances t1_j1gqx97 wrote
That’s fucking nuts. I need to know more. Thanks.
bendvis t1_j1gs98d wrote
My wife and I just discovered a really well done YouTube channel called Astrum. Their video on black holes is fascinating and covers this stuff in a clear and straightforward way. Highly recommended!
f_d t1_j1gysd5 wrote
>This super rapid expansion explains why the cosmic background radiation is so nearly perfectly even - because at that time in the early universe, it was all in one point.
It wasn't necessarily in one point, it was just extremely dense and homogeneous. Space could have been infinite even when everything was packed together tightly.
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