Recent comments in /f/askscience

CrustalTrudger t1_jb5hcc8 wrote

The force is driven by the negative buoyancy of the slab. If the slab detaches, there is no more driving force for the portion of the plate on the surface whereas the slab continues to sink. A simple analogy would be a weight clipped to the edge of a floating mat. If the mat rips, the portion attached to the weight will sink but the rest of the mat will just sit there (assuming it is buoyant). This is expanded on in much more detail in a top level answer I made within this thread to try to address the relative incompleteness of the specific top level comment that everyone is upvoting.

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morningcoffee1 t1_jb5gs3a wrote

Our "cluster" is called the "local group" and contains about 30-35 galaxies. The two largest are our own Milky Way and the Andromeda Galaxy. The radius of the local group is ~5 million lightyears.

For comparison, the Virgo Cluster is relatively close by at 60 million lightyears and is a bit larger in radius: 7.5 million lightyears *but* contains between 1300 and 2000 galaxies.

So, using that comparison, as well as most other local clusters, our local group is indeed quite sparse.

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xxDankerstein t1_jb5fer2 wrote

The simple is answer is: sand big, clay small. Clay particles are tiny, so they hold more water between them (more surface area per volume). Sand is basically tiny rocks, which themselves don't shrink at all. The shrinkage happens when the water between the particles evaporates. The sand is holding less water, thus less shrinkage.

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Busterwasmycat t1_jb5dqbn wrote

rate doesn't affect the fact that accumulation is happening, what matters is that addition exceeds removal over time. How long it would take to make a thick pile, though, that does matter on rate, or more particularly the size of the difference between addition and removal (high addition rates combined with high removal rates would still result in slow accumulation, same as if both were low). The Antarctic has been accumulating ice for maybe as much as 25 million years, or about there, and it probably wasn't such a desert for all that time.

The earth did not go from "Antarctica is a temperate forest and grassland" to "Antarctica is a frozen desert of ice" overnight.

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Syfer2x t1_jb5d0sr wrote

I think it’s actually fairly easy to do when you correlate the rise in temperature to a rise in human industrial activity. As a previous comment mentioned, these processes are slooooow, like reeeeaally slow. The insane spike in global temperatures since the beginning of the industrial age is far too sharp to be attributed to normal interglacial activity, which I believe technically we should be exiting anyways. We’re becoming overdue for another glacial period but are staving it off and then some just with our own activities.

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DevinVee_ t1_jb5c59e wrote

but isn't "space expanding" just matter/objects spreading apart from each other? space isn't a physical thing it's the absence of physical things. So, space expanding in this spot faster than this spot just means these two objects are moving away from each other faster than these other two things are moving away from each other. This still doesn't solve the issue that if the Earth is x distance away from the hypothetical center of the universe (something afaik we haven't determined its location) where we are seeing this light come from, that light theoretically can't be from the big bang, other wise it would imply that the Earth was in this location before the big bang occurred, or that light would've passed through here already.

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If you're saying space expands faster than light in certain spots in the universe fine that happens, but saying that means the distance between Earth and the hypothetical center of the universe has expanded faster than the speed of light meaning Earth has traveled faster than the speed of light. Which is impossible according to our understanding of physics.

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So with that, I see it as a few possible explanations..

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  1. The light we are seeing today from 13 billions years ago (i.e. 13 billion light years away) was, in fact, not the first lights after the big bang.

  2. The lights we are seeing are just "the earliest lights after the big bang" that we've seen and "The first lights after the big bang" is simply click-bait titles. This means that we will never see any light source from the initial big bang or shortly there after because that light has already passed us by. (hypothetically we could see the refraction from a large gravitational force bending said light back but for it to bend back in exactly the same way to reflect something understandable seems impossible.)

  3. The lights we are seeing are from the opposite side of the universe from a source that is expanding just as rapidly (but not at the speed of light) from us and we can actually see the center of the universe -- We know we've seen things that are moving away from us, but have we seen anything moving the exact opposite direction from us? Specifically multiple things?

  4. the big bang is a lie, everything is just floating around nothing is moving away from a specific point.

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These are the things that confuse me every time some one mentions the "First lights of the universe" how can that possibly be? regardless of the expansion of space moving faster than the speed of light.

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Narwhal_Assassin t1_jb58rm4 wrote

Ok I see what you mean now. Ordinarily, you would be exactly right: there’s no way we could’ve gotten that far away from the photons that they would take 13 billion years to reach us. However, early universe is anything but ordinary.

Going back to grandma and the mailman, imagine they’re both on the sidewalk, but grandma is on the side closer to the house. At the same time, they both start to move towards the house, but as grandma steps off the sidewalk, it suddenly quadruples in size. Grandma is fine since she already got off the sidewalk, but the mailman suddenly has to walk four times as far to catch up. Then, as he hits the halfway point, it quadruples again. And as he keeps going, it keeps getting bigger and bigger. Grandma already made it to the porch and is knitting a sweater, but the mailman hasn’t even gotten off this piece of sidewalk.

This is how the early universe looked. In the first instants after the Big Bang, some photons were going the same direction but from different places. Because space expanded so rapidly, the photons with a “head start” in their direction got a lot further ahead than the others, and this head start kept growing as space continued to expand. Except instead of doubling or quadrupling, it was expanding by millions and billions. Even though they started so close in the beginning, a gap of a nanometer could expand to a light year faster than the photons could cross it, so they got left in the dust.

Remember that all the stuff we see and interact with started off as photons too, just running a shorter race, so after they got here and started settling down into planets, the other photons were still trying to overcome the vast distance that space itself had made by expanding

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perta1234 t1_jb56y5u wrote

That would be maybe more like the expected height given phenotype or genotype of parents, or posterior probability of height in certain range? The oldest quantitative prediction is that progeny is the average of parents. Clearly hides a lot of variation under that simple mean. Maybe check things like estimated breeding value. Might help. Good luck.

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