Recent comments in /f/explainlikeimfive

thatbromatt t1_j6mmfpw wrote

Iron is the “kiss of death” for a star. Stars are just giant engines fusing elements - at the center you have a dense mass that gravity is pushing together and fusing elements into heavier elements. Once a star fuses it’s way up the chain and reaches iron - a chain reaction is set into place because there’s just not enough energy in a star to fuse iron. Since fusion can no longer occur this is where the engine shuts down and gravity overcomes the star, collapsing in on itself

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Gnonthgol t1_j6mmao7 wrote

You are assuming that the universal speed limit, aka. the speed of light, applies to space itself. But this is not the case. Nothing can move faster then the univerals speed limit compared to the fabric of spacetime but the fabric itself does move faster then this. As far as we can tell the space that is infinatly far away from us also have infinate speed away from us. It could therefore have moved from a single point to where it is now.

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[deleted] t1_j6mm8e1 wrote

I'm replying because I am in fact a genius

I'm the guy who came up with the political solution of disenfranchising all men

I'm the guy who came up with the idea to teach all babies sign language

I'm the guy who first discovered that quantum entanglement does in fact communicate information: it guarantees that randomness can be the same all over the universe at the same time

I think that this discussion could be more polite that's all

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AshFraxinusEps t1_j6mm18r wrote

Doubt that. Most/all natural plants have seeds and to my knowledge this one was just a default herb-like plant, so should have some seeds

Also the fact that it was cultivated suggests that it had a normal plant lifecycle. We can make seedless fruits but not so much for herbs and such

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pselie4 t1_j6mkz86 wrote

>These new seconds are not the same length as regular seconds. I haven't done the math but it is possible to just make a second faster or slower.

You just gave every scientist and engineer a new nightmare. And I'm sure every programmer who ever had to code time and date functions has put you on their hit list.

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Pocok5 t1_j6mkuar wrote

OLED also incurs extra power cost when switching stuff around faster (at the minimum, there are a bunch of multiplexers and a logic driver to convert from the display input signal - a serial protocol over a couple wires - to the thousands of pixel row/column lines) but power save mode on it is usually switching to a dark color theme which lets it turn off pixels and reducing overall brightness.

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dirschau t1_j6mknjt wrote

There is a short answer to your title question: "nobody knows and currently have no way of knowing". Any contradictions come from comparing ideas that aren't meant to go together because they're parts of different models.

We don't know if the universe is infinite. We don't know what was happening at the earliest moments of the universe. Was it a single point? Maybe, although that's a very unpopular idea among physicists, just like the singularity in black holes. It contradicts quantum mechanics. There's currently not a better model, but they're pretty certain infinite density should be false.

We simply do not have the maths or technology to answer those questions. It would require the "Theory of Everything", with quantum gravity and all that. And the tech to test it.

To the followup questions.

It's absolutely possible for infinite space to have infinite matter and still be relatively "empty". There's just more space than matter. Just repeat what you can see in the sky infinitely in all directions. There's no contradiction.

Expansion can be weird to think about, but that's why the baloon/rubber band imagery is helpful. If every point in space stretches the same amount, something 1 "unit" away will stretch to 2, but 2 will stretch to 4. So distance matters. "Our local area" is the few neighbouring galaxies that are gravitationally bound, so any expansion of space (at observed rates) that close wouldn't be significant.

Also, expansion isn't actually uniform, gravity does counteract it. There is no expansion within a galaxy, or even within clusters (as far as I understand). The concentration of mass counteracts expansion.

BTW, our immediate vicinity being fairly empty actually IS weird. Our galaxy is actually in a void, imaginatively called the Local Void. The galactic neighbourhoods are usually more busy.

As for CMB and flatness, I only have a rough idea based on what I've read, but essentially is goes like this: "flatness" of soacetime is all about parallel lines being parallel and angles in a triangle adding up to 180 degrees. So geometry you'd do on a sheet of paper. For example, on the surface of the earth which is NOT flat, you can draw three lines (along the great circles) which will meet at 90 degrees and yet form a triangle. That's non-euclidian geometry.

Where the CMB comes in is the fact that it represents the very early universe. But it directly corresponds to today's universe, but everything has grown since then. So depending on the curvature of the universe, the patterns in the CMB should have specific shapes, corresponding to the massive structures in the visible universe. So astronomers made the observations, made the modelling, and the shape of the CMBs patters corresponds to the model where spacetime is flat.

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fleur_essence t1_j6mkikq wrote

This is an excellent explanation. To provide some context, though, a hemoglobin of 6.6 is not all that low. It’s certainly low enough that the person should get transfused a unit of blood (usually indicated if the value is below 7). However, the real issue is figuring WHY it got low in the first place. Is the patient’s own immune system attacking their blood (autoimmune)? Is there a bleed somewhere (like the gastrointestinal tract)? Is there cancer in the bone marrow leaving (less likely if only the red cells are low but not the other blood counts)? Is there an iron deficiency for some reason? Figuring out the cause of the anemia will be important to knowing how to treat and the actual prognosis.

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adam12349 t1_j6mkasd wrote

So flat does not equal infinite. One option is an infinite universe but there are finite options that are flat in their fundamental domain. The universe has a topology. The part we care about is curvature. Lets drop one spacial dimension. So now the universe could be something like the surface of a sphere it has positive curvature. The defining property of positive curvature is that initially parallel lines converge and the opposite for negative curvature. Now flat topology is where parallel lines remain parallel.

Lets look at an example you got a 2D universe with flat geometry. Its a sheat of paper. One option is that the paper is infinite. Parallel lines on that paper remain parallel. This is the geometry in the fundamental domain (2D) of this universe. Now lets give it a rule, lines going far enough to the left emerge on the right coming back to their start. If you want to embed this topology in 3D you just connect the left and right edge. You got a cylinder. It has flat geometry in its fundamental domain and is almost finite. To make it finite we connect the upper and lower edge to get a torus a donut. It has a flat geometry and a finite size, you go far enough in any direction you get back where you started. As it turns out you can embed a this flat geometry and get a torus without distortions. So add an extra dimension with the same rules and our 3D universe could be though of as the surface of a 4D torus. But there are other options that also have a flat geometry in their fundamental domain but give us a finite universe.

For an infinite universe it has always been infinite. The big bag happened everywhere. You being able to trace back every path to a single point only means that the universe is scale invariant so you can resale it all you want. Lets look at density if you look at the universe now but zoom way out because volume essentially means nothing you see a really high matter density. So your scale for volume is arbitrarily. If you have a collection of points on a grid you can zoom in and conclude that the points have a low density but zoom out and see that they have a high density. If the universe is infinite you can pick an arbitrarily large scale and there is always a scale where the universe looks the same. Infinite means that you have no reference points for scale, there is no true scale to the universe. Well the only problem is matter being finitely divisible so something like the size of an atom kinda gives a scale to the universe. But the thing is an infinite universe is consistent with the data we have.

And yes infinite energy is a consequence. And infinite density only means that the volume you pick is arbitrarily. Scale it up and density grows approaching infinite scale it down and it approaches 0.

And flattenes from the CMB is basically just draw a triangle as big as you can, so the two other points on the CMB is the largest we can make. Add up the angles, if its <180° thats negative curvature if ist >180° positive curvature and =180° means flat geometry.

So all in all you can think like this the global properties of the universe don't change. It always has an infinite density and an infinite size, but local properties can. You have a numberline with all the natural numbers. You can stretch the nubers and create larger gaps, the length of the numberline and the amount of stuff it contains remains and you can zoom out to get back the original "number density".

1-2-3-4-... early universe

1---2---3---4---... current universe zoom out and you see

1-2-3-4-... again.

Zoom out even further and everything overlaps.

● - you pretty much see a point.

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