Delta1212

Probably the most common analogy is dots on a balloon. Take an uniflates balloon and cover it in dots from a marker. Now blow up the balloon. The distance between all of the dots will grow as the balloon expands. The same is true of the universe. The Big Bang is not really a "big bang" at all. The universe used to be much smaller, with all the matter compressed together because that's all the space there was. As space expanded, the distance between points of matter grew. Space is still expanding and matter is still growing apart over large distances (i.e. where gravity and other attractive forces aren't strong enough to hold it together). There is no central point that exploded and which everything is moving away from anymore than the dots on the balloon exploded away from a central point. There's just more room now and it's increasing at every point in space.

Strictly speaking, culture is learned behaviors and ideas passed down through generations. Learned, in that it isn't instinctive or biologically determined and therefore must be taught by someone else. Humans aren't the only species to do this; it has been observed in animals ranging from primates to marine mammals to some types of birds. What complex human language allows, however, is a much greater deal of information to be taught more effectively and much more complex and abstract behaviors and idea to be passed down and built upon. It also allows for a much larger range of cooperative behaviors between individuals which is the basis for a lot of human achievement. Language is responsible for our ability to build on each other's accomplishments, both by working with contemporaries and by learning from and expanding upon the knowledge of the previous generation. Animals can teach each other to use rudimentary tools and sing unique songs, but the ability to innovate and rapidly disseminate new knowledge really relies on communicative ability, and humanity's language skills are unparalleled.

Welcome! Black holes do have mass. Either a source of information has mislead you, or you've confused it with a singularity being a point with no volume (finite mass divided by zero volume equals infinite density). Gravity decreases with the square of the distance from the center of gravity. That means that as you get closer to the center, gravity increases exponentially. However, once you hit the surface, this stops being true. If you were to tunnel under the Earth, you would be getting closer to the center of gravity of the planet, but more and more of the mass would be above you, which leaves less to pull you to the center and more actually attracting you in the opposite direction until, at the very center (ignoring the heat and pressure that would kill you) you would be weightless because the mass in any one direction is balanced by an equal amount in the opposite direction. A black hole, however, condenses all that mass into a much smaller point, which means you can get much closer before hitting the surface and experience the gravity ramping up to a much greater degree. If the sun were to collapse entirely into a black hole right now, there would be no change in the gravity that we experience here on Earth. The planet would still orbit the black hole once a year. However, you'd be able to get much closer to the black hole than you would to the sun, and once you'd gotten well into that distance range that would currently put you inside of the sun, gravity's effects would be much stronger. Denser objects don't have more gravity than less dense objects of the same mass at any given distance, but since denser objects are smaller, you can get a lot closer to all that mass, and the closer you get the more gravity you will experience. The fact that black holes do have mass also explains how they can have the mass of "a hundred suns" and yes, a lot of that is from matter falling into them. Space does not have mass, no. Photons are one type of massless particles. Particles with mass cannot travel at light speed. Particles without mass can only travel at light speed. Mass is just a property and has nothing to do with whether something is real or not.

What is north of the North Pole? It's possible to have a finite distance with no boundaries. Imagine space as the surface of a balloon. When you blow up the balloon, the surface area increases, but there is no "edge" of the area. The Big Bang is not an explosion of matter and energy out into space; it's the expansion of space between all the matter and energy in the universe. It's also important to note that what seems logical is not always actually correct. Using logic without checking it against real world evidence is how Arostotle concluded that heavier things fall faster than lighter things.

There is no event horizon unless there's a black hole. You can't have half a black hole. There isn't one and then there is one. This doesn't prevent people from (accurately) stating that a star "is collapsing" into a black hole, even if there isn't a partial black hole that is slowly emerging during the full duration of the collapse. There are plenty of valid arguments against the OP's idea, but the idea that a collapsing [something] must, at some point, become half a [something] is not one of them.

This is incorrect. Our current understanding is that space itself is expanding between points. The expansion of the universe is the expansion of space, not the expansion of matter and energy into space.

I knew the half-exploded dynamite analogy wasn't going to work, but I hadn't thought of a better one at that point. Let's try this: A star "is collapsing" into a black hole. At what point is it half star/half black hole?

First of all, I'm not the OP, and don't agree with the OP, so I didn't say "is collapsing" at any point. Secondly, just because the transition is instantaneous doesn't mean there isn't a process leading up that that transition which doesn't necessarily lead to in between forms any more than a lit fuse leads to half-exploded dynamite. If a dimension was shrinking and the end result of that shrinkage was that it would disappear from existence, I would say that the dimension is collapsing. I would never say that it reaches a point where it is half a dimension. I don't think that is actually happening, of course, but a bad argument doesn't become a good argument just by being in favor of the right stance.

I'm not supporting the idea that we're collapsing from 4 to 3 dimensions, but this argument doesn't necessarily hold. Let's say I have some ice that is melting. Eventually, I will have no ice because it will have melted. Does that mean I ever had half-ice? At some point I must have had an ice cube that was half the size of what I originally started with, but that ice would still be entirely ice. Similarly, a dimension might, hypothetically, shrink until it popped out of existence, but that doesn't mean you'd ever have half a dimension, just a dimension that was smaller than before.

True, but wavelengths and colors aren't necessarily the same thing. Every wavelength doesn't have a distinct color that is distinguishable from that of every other wavelength. If the question is "is there an infinite number of wavelengths in the visible spectrum" then it is a physics question and the answer is yes. If the question is "is there an infinite number of colors in the visible spectrum" then it's a physiology question and the answer is no. I do realize that the question is posed as a physics question, but it seems to be framing a philosophical question that actually has an answer that is more accurately provided by the physiological question than the physics one. Unless you're just defining color as being the wavelength rather than the subjective visual experience of the wavelength, but that seems less accurate relative to what most people are talking about when they say color.

Color is a subjective experience created by specific wavelengths of light reacting with specialized cells in the eye. The number of colors you can see is based entirely on the number of different types of "color" cells in your eye. Humans (mostly) have three which roughly, but not exactly, correspond with RGB. This is why they're considered the primary colors of light. Animals with different numbers of cones (the color detecting cells) may see more, fewer, no or different colors. People with color blindness have one or more of these three types of cone that do not function properly, which is why they have difficulty distinguishing between certain colors, because those colors do not exist for them. Colors themselves do not "really" exist in nature. They exist purely subjectively as a way to distinguish between different wavelengths of light. Defining the number of colors then really becomes a matter of determining the number of hues that the human eye can distinguish between, which is a somewhat controversial subject, but the number is significantly smaller than infinity.

When you look at something, light isn't "helping" you see it. You are seeing the light that bounced off of something and using it to create an image of the thing it bounced off of. In other words, you only see light. So yes, telescopes are used to see light from stars.

In order for B and C to turn around, they have to accelerate.

Do you understand that "glare" and light are the same thing?

Why would anyone see C aging 20 years?

Nothing with mass can be accelerated to light speed. Anything massless always moves at light speed. Space, however, can expand faster than light speed, and still does over large enough distances.

Attach lever controls for a jet pack to your feet.

Are you contending that blue light is faster than red light? Because if they travel at the same speed, and that speed is constant in relation to the source, then there shouldn't be any Doppler effect.

Didymus, out of curiosity, do you accept the constancy of the speed of light, or do you believe that to be false?

Keep in mind that the coin flip analogy is solely meant to illustrate how small samples of probabilistic randomness can produce counter-intuitive results to people who are used to dealing exclusively with very, very large samples (which is almost everyone), even though the large processes derive directly from the smaller ones. The behavior of coins doesn't really otherwise apply to the behavior of sub-atomic particles in any kind of one to one fashion. I'm not entirely sure what you're trying to say here, or how what you're arguing for differs from accepted physics other than that you seem to be saying that atoms are actually whole universes, but I'm not completely sure that's what you mean, and even if it is, I'm not clear on your reasons for thinking that may be the case.

I'm far from an expert, but based on my somewhat limited exposure to the subject, infectious disease was significantly less common prior to the domestication of animals, partly as a result of the smaller population sizes of human groups and partly because of a severely diminished degree of contact with animals leading to fewer opportunities for species jumping. It's why Europeans with their generally higher population densities and significantly larger number of domesticated animals brought more diseases to the Americas than crossed back in the other direction. How much of a bearing on the health of Homo erectus in the modern world this would actually have, however, I do not know.

Sub-atomic laws average out to macroscopic laws. It's like how if you flip a million coins, it averages out to almost exactly a 50/50 split between heads and tails, but if you flip one coin, you only get either heads or tails. On the macroscopic scale, you can only see a million coins or more flip at a time. Individual coins are far too small to observe. So in our day to day lives, we can see that coin flipping always comes up half heads and half tails. On a sub-atomic level, we could see coin flips that come up only heads, or only tails, or three-fourths heads, or what have you, and these would seem extremely counter-intuitive because they contradict our everyday experiences of coin flipping. The sub-atomic weirdness doesn't require a deeper level where the laws are the same as our own, it's just that it's such a small sample size that it's much more heavily subject to randomness, whereas we deal with such huge numbers of particles in the course of our normal experience that the weirdness gets smoothed out to the point where things that are probabilistic seem entirely deterministic because the odds of them deviating by any noticeable amount from the average are vanishingly small to the point of being practically impossible.

In 1, they different amounts of time in different inertial frames. In 2, they spent exactly the same amount of time in each inertial frame. It would be like me traveling 14 miles in a car but winding up back in my house versus me traveling to my friend's house and my sister than coming to my friend's house later on. In the first case, both me and my sister are at my house, but I've traveled 14 miles and she hasn't. In the latter case, we've both traveled the exact same distance, albeit at different times. If you want it to be more symmetrical, you have the second case where the traveling observer never slows down, but the observer at rest enters a spaceship and catches up with the traveler. The observer who was previously at rest will now be the one who has aged less.

I don't think you are quite grasping what mixing frames means. Frame #1: The distance between point A and point B is 7 ly. Frame #2: The distance between point A and point B is 1 ly. Observer X starts in Frame #1 at point A, enters frame #2, travels to point B, turns around, travels back to point A, re-enters frame #1. Observer Y remains in Frame #1 at point A for the duration. Valid statements according to relativity: While traveling, Observer X measured itself moving 2 ly total over the course of approximately 2 years, therefore traveling at just under c, at the end of which Observer Y is found to have aged approximately 14 years. Observer Y observes X moving a total distance of 14 ly over the course of approximately 14 years, therefore traveling at just under c, during which time X experienced time dilation and aged 2 years. Invalid mixing of frames: Observer X aged 2 years and Observer Y measured 14 ly, therefore Observer X traveled at 7c.

What about the light from stars and galaxies that are lightyears away? Any pressure generated by them would have diminished to almost nothing by the time that light reached us, certainly to less than the outward pressure created by light from the sun. If the movement of light was created by pressure generated by a light source, that pressure should overwhelm any incoming light and prevent it from reaching Earth. Also, if light somehow entered a rest state when not being pushed by other light, then it should stop moving when the source stopped emitting light. That may not be visible with the sun, which doesn't go out, but it would be apparent every time you turned off a light. You'd wind up scattering "at rest" light any time you moved through a newly dark room. Your movement would temporarily create brief flashes of visibility in the dark.