What do we really know about the universe? Big Bang, expansion, size of it, does it never end, multiple universes, how far does time go back, etc. Any cool facts or theories? I read a recent article that they believe the universe is something like 20x bigger than previously believed with new telescopes.
When they said bigger, they mean the number of galaxies. The Hubble has been a bonanza of information. That and other technology is why this is being called the golden age of astronomy. http://www.news.com.au/technology/s...t/news-story/6a632b09d2a0b6ca9fb118f8e89ea184 It was only in the 1980s that we began to get hints of dark energy. That, taken with dark matter [two entirely different concepts] account for about 80% of the universe. We have competing theories and models for the history of the universe. Some argue that the universe essentially popped into existence from nothing. But more and more it looks like we might develop a model that explains the big bang. One model has the universe as a 11 dimensional hypersurface that underwent some kind of catastrophic event, that collapsed all but 4 dimensions we know, as the forces of nature - Strong force, weak force. electromagnetic, and gravitational. That collapse is what we call the Big Bang. So in that model, the universe has always existed but underwent a dramatic transformation. And what we measure a electric force, for example, is really due to hidden dimensions from the early universe. Another model suggests that empty space isn't empty and matter arose as the byproduct of a changing speed of light [inflation theory] during the earliest moments of the universe. Other models have universes popping into existence endlessly like bubbles from a bubble machine. These are just other universes. And then we have theories like the strong version of The Many Worlds Theory, which suggests that a new universe is created with every choice or path. If you make a left instead of a right, in fact both occurred, with you going right in one universe, and left in the other. And yet another recent paper and follow up work suggests that the entire universe really is a simulation and we are all just self-aware programs. And the scary thing is, the argument makes a lot of sense! So the complete history of existence is still undetermined. If we have the explanation for everything, we don't know which model is correct.
It is estimated that the diameter of the observable universe is about 28.5 gigaparsecs (93 billion light-years, 8.8×1026 metres or 5.5×1023 miles), putting the edge of the observable universe at about 46.5 billion light-years away
We are limited by what we can observe and we can observe is so limited that it is barely consequential.
Althougb it does continue to amaze me that scientists are able to work out so much from the limited information available. Sort of like Sherlock holmes... extracting meaning from apparently trivial details
68% Dark Energy + 27% Dark Matter = 95% Where did you get 80%? Science popularizing documentaries, articles, books, tend to dwell on the more controversial(fringe) ideas because they tend to attract the most attention. "M-theory" is based on the assumption that all non-contradictory interpretations of "Superstring theory"(which itself is but one "plausible" interpretation of the entire Standard Model of Particle Physics) are correct. Many(most, I think) physicists are skeptical as to whether M-theory, or even Superstring theory, even qualify as science. Many Worlds "theories", since they are untestable in principle, are without question, not science. Inflationary Standard Big Bang models are testable(and thus falsifiable) in principle, and so definitely are real science. The main appeal, though, of inflation(as posited by Guth) is how well it explains observations and that we can use it to make reasonable predictions, which happened to also be the main appeal of the Ptolemaic model of the Solar System.
I have often wondered how they know we live in a spiral galaxy. It isn't like we can get a view from far away.
Spectroscopic Parallax works to measure the distance of stars up to about 150,000 light years away(or is it 10,000 parsecs? I'm not sure, but there are other methods). You measure the apparent magnitude of a star of a known Spectral Type in its Main Sequence, and then do some math to find out its approximate distance from here. Once you have the distances and the respective angles between them and us against the sky of enough Main Sequence stars, you can have a pretty good idea of the shape of the galaxy.
Well, using what we know of the evolution of knowledge and the history of science, some of what we think we know is probably not correct and something will replace it. And a shift in paradigm may occur.
I was probably pulling an old estimate from memory. Well, right up until it can be tested. True as it stands, but that doesn't mean its wrong. And it is still a major school of thought. He asked what we know. There is reason to believe the Many Worlds Theories in some form could be correct. And if wrong, is meaningless. It doesn't make sense to hang your hat on a theory that is incomplete and can't account for 95% of what is believed to exist. So it is no more compelling than M Theory at this point.
It's hard to say what we really know or don't. I think right now there are 2 big unknowns in the universe, things we know we don't know. There are other things we don't know, like are their aliens, how did life begin, or what's the cure for cancer, but I'll try to limit it to "universe" questions. 1) What is Dark Matter? We don't know what it is and it's supposed to make up most of the universe. "Dark Matter" is just a term, we know it affects gravity/spacetime so it's assumed to be some sort of matter, but that's not necessarily the case. It could be gravity doesn't behave the way we think it does. 2) Quantization of gravity/spacetime. This is a big problem in physics. Einstein's general relativity equation currently has an imbalance in its equation. If you remember from Algebra an equation like 2*x = 6, we can solve for x knowing the equation is balanced (divide both sides by 2 and x = 3). This is how equations must work, or they're not equations. This is the equation for General Relativity, the details are much, much more complex but here it is: The left hand side of the equation basically represents space-time. The right hand side essentially represents energy (with constants to convert to space-time units), so the equation relates energy and space-time. The imbalance is we KNOW energy is quantized from quantum theory, and we have absolutely no idea how to quantize space-time (gravity). Physicists get around this now with what is called the semi-classical equation for gravity, which is a cheat. It does work well for a lot of problems but mathematically it breaks down in extreme cases.
They don't know, they speculate. Some find the speculation interesting, others find it utterly pointless. No prize for guessing which camp I belong to!
Not too long ago I read a book called "The Elegant Universe" by Brian Greene. It talked about string theory and the possibility of 13 balled up universes. Balled up universes? Where? What?? It made my head hurt.
https://www.spaceanswers.com/solar-system/can-we-grow-food-on-mars/ In short, what we observe locally is consistent with other spiral galaxies observed at a distance. And we know local observations are not consistent with any other types of galaxies observed.
Look, all you're doing is parroting what you've read they've said. Would you believe it if they said Saturn is made of cheddar cheese? Of course you wouldn't. Or would you?
Science can explain (and over time does a better and better job at explaining) how things work. For explaining why they work, you will always need some sort of faith...
I often wonder if there's nothing they can't dream up which is so ridiculous that it would make even the most gullible of space nerds stop and question whether or not they're being led down the garden path. - - - Updated - - - Um, like blind faith for instance?
Faith need not be blind, but it will never be scientific. (When was the last time you heard a scientist try to explain why the universe is? Why the big bang occurred? Why we're here at all?)
Does that mean anyone and who has a vivid imagination together with the ability to articulate convincingly - you know lie through their teeth - can call themselves an astrophysicist? I mean take this 'big bang' thing - could it have been dreamt up by such a charlatan, or is there tangible evidence that it actually happened?
But that's my point. Having tangible evidence that a thing actually happened does nothing to answer the question of why it happened.
