wat (thelemmy.club)
submitted 3 months ago by to c/memes@sopuli.xyz
 

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[–] 240 points 3 months ago (41 children)

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.

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  • [–] 60 points 3 months ago (1 child)

    Thanks for that that's actually a really helpful analogy.

    I mean i still dont understand. Brain hurty. But thanks anyway

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  • [–] 7 points 3 months ago

    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).

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  • [–] 34 points 3 months ago (8 children)
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  • [–] 17 points 3 months ago (2 children)

    This is a truly great explanation. One worthy of Feynman. Physics degree?

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  • [–] 17 points 3 months ago (1 child)

    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.

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  • [–] 11 points 3 months ago (19 children)

    The space between atoms starts to expand faster than the speed of light. Well i guess that is the universe fucked.

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  • [–] 13 points 3 months ago (16 children)

    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.

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  • [–] 12 points 3 months ago* (15 children)

    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.

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    [–] 68 points 3 months ago (4 children)

    Well, nothing (with nonnegative mass) can move faster than light through space. Space itself can do whatever it wants to.

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  • [–] 6 points 3 months ago (2 children)

    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...

    ᕕ(ᐛ)ᕗ

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  • [–] 15 points 3 months ago* (1 child)

    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.

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  • [–] 47 points 3 months ago*

    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. 😌

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  • [–] 38 points 3 months ago* (22 children)

    Wrong, the expansion doesn't have a speed because it isn't motion. But you have to think about it longer than you'll probably want to before hitting the up or down arrow and/or scrolling.

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  • [–] 29 points 3 months ago (9 children)

    Best intuition I've heard for this is that "things" can't move faster than light, but not everything is a "thing".

    Imagine doing shadow puppets on the wall with a flashlight. You move the bunny left, shadow moves left. The further away the wall is, the faster the apparent speed of the shadow bunny. You might think that, far enough away and with a strong enough light, your shadow bunny would be racing across the sky faster than the speed of light -- and the crazy thing is, you'd be correct! The shadow (absence of light) can move arbitrarily fast. But the light itself is moving at its normal constant speed from the flashlight out into space, perpendicular to the travel of the bunny, like a garden hose spraying water. The time it takes for the shadow to even begin to move is governed by the speed of light. No information can be communicated faster than light because the light travels at the speed of light to illuminate the places where the shadow isn't.

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    [–] 29 points 3 months ago (7 children)

    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

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  • [–] 20 points 3 months ago*

    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.

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    [–] 15 points 3 months ago* (11 children)

    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.

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  • [–] 19 points 3 months ago* (2 children)

    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.

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  • [–] 9 points 3 months ago (3 children)

    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!

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  • [–] 7 points 3 months ago (3 children)

    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.

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  • [–] 13 points 3 months ago* (6 children)

    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

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    [–] 8 points 3 months ago (1 child)

    The speed of dark is faster than the speed of light

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  • [–] 8 points 3 months ago

    Explanations why space expands are way more crazier than this.

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