The Astronomy Thread

I really enjoyed this article. I believe it was originally written back in '08 or so but was recently updated. Anyway, I don't know if it was posted before(probably has) but I've yet to see such a comprehensive write up of current and future propulsion technology feasibility in regards to interstellar space travel. It's actually a little depressing really to see how far away we are from anything substantial.


How Long Would It Take To Travel To The Nearest Star? - Universe Today

Can we not turn this thread into the shitfest Global warming thread with science denials and other bullshit. Just post a fun article and move on. Last thing we need is rescorla coming in here and talking about how the AGW's made up the big bang too.

Furry_sl said:

This happened to be one of the first and earliest tests of the big bang theory. The big bang theory originally predicted a perfectly even and much more intense background radiation. The steady state theory predicted a cosmic background -exactly- as it was. For some reason, people still use this as proof toward the big bang theory, even though we've since discovered its not even and the theory incorrectly predicted results.

The story of how the radiation backgrounds were theorized is a very interesting one from a historical science perspective. It actually began with a simple observation from a person I can't remember off the top of my head. He simply said something along the lines of "In every direction of the sky there is a sun, so why is the entire sky not like the surface of the sun?". It's a simple and logical observation that leads the mind to the simple fact that SOMETHING degrades the energy of light over time, and this prediction far predates the big bang theory, and setting forward as proof of the big bang theory is silly.

The big bang theory will tell you that it knows how this is happening, and why, yet there is nothing in physics at all to explain the process in any way that can be scientifically verified.

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There is a lot wrong with your understanding of the CMB, and your previous post on fundamental physics "changing" to try to explain the big bang. Older theories in physics are simpler ones that can't explain higher energy phenomena or smaller scale structure, the corner cases or edges of understanding. So physicists go searching for the higher order theories to help explain new observations that can't be explained by the older ones. Take gravity for example. Newton's laws can quite accurately describe planetary motion to some level of confidence, but some astronomers saw perturbations in orbits such as Mercury that couldn't be explained. It took Einstein's general relativity to show that gravity is actually an effect of mass warping space-time, and not some intrinsic force due to that mass. Further, you can take general relativity equations and simplify them down to Newtonian gravity if you make some limiting assumptions (like limiting velocities well below relativistic speeds, limiting masses below stellar/black hole masses, and increasing distances to remove spatial mass distributions to make them look more like point sources). In that way you can see that GR is the better more complex underlying theory, able to more fully explain the true physics of what is happening. If the problem you're trying to solve can be simplified or the solution you seek does not require high degrees of accuracy, then you reduce GR down to Newtonian physics.

I'm going to shill this again. With people asking about exposure sources to some of this science that is designed for the layman.
PBS Space Time. A Big Deal. There is around 45 videos now - some of them are bunched into topics. This is the first video of Relativity.

The CMB isn't a direct proof of any sort of big bang. The CMB is an indication that, in every direction which we can see, the universe itself used to be opaque and ludicrously energetic. The CMB is extremely interesting but it's not a smoking gun.

Expansion is an entirely reasonable explanation for why it isn't anymore. But really it doesn't have to work in reverse. (Yes, as an acceptable model of physics it does have to be time reversible. But as a physical reality -- who the fuck says it has to be?) The CMB is the timewise edge of our observable universe. Beyond it we know absolutely fuck all. We do know that it delinates a change of state, and with the particle physics we have some reasonable ideas about the nature of that change. It doesn't mean that we know more than we know.

The Big Bang is our modern creation myth. It's even changed fairly significantly in the brief period of time that we've been alive. Adhering to it as Gods Own Truth might be foolish.

It's not that we're retarded. It's not the worst guess. Given what we are confident of it seems like a pretty reasonable guess to me. But I think you do need to call a spade a spade. Plenty of reasonable things turn out to not be true.

Furry_sl said:

The problem with relying wholy on observational science and only observational science to write laws of physics is that you can not fully understand the workings of a system that you can not fully see. I understand that you generally think this isclose enoughand thebest we can do, which is most certainly true. Taking general relativity, I have issues with the explanations, but the math is obviously superior in edge cases. Since we don't have the current technology to put large parts of the theory to controlled tests, we can't refine our understanding of the theory and WHY it is happening. General relative is certainly good and tested in some mathematical regards, but I've said before that some parts of the gravitational theory require refinement. Either way, this is not the subject I brought up or was discussing.

You say my understanding of the CMB is incorrect, how? You make a pretty grand statement refuting what I've said on the subject without any explanation offered for me to attempt to refute. Care to offer that, or are you just blowing wind at me because you find my stance problematic?

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Iannis is pointed in the right direction about what CMB technically is from our understanding today. I disagree though with the inferences you can make prior to its appearance in the universe's past. It is a horizon that is predicted by some inflationary theories. Inflation has been pretty well studied and fits very well with observation. Extensions of inflation take you to the big bang or cycling universe theories, but inflation itself is on pretty firm ground theoretically.

On relativity, it has been tested more than any other modern physical theory and comes up correct every single time. We have launched several satellites that probe its predictions that have verified the model. We have made observations of light bending around the sun that confirm it. And you confirm it every time you use GPS,as relativistic effects from the large difference in velocity between the orbiting satellites and the ground are corrected for to provide better timing accuracy, and thus higher positional accuracy. The accuracy of the special and general theories of relativity are not in doubt in the current world of theoretical physics. It does though, have limitations as you approach its edges (vicinity of black holes, masses approaching the speed of light), but these are areas where parameters trend toward infinities and some higher order exotic physics has yet to be discovered to explain these phenomena.

There is a lot of work within the field on trying to understand ways to probe and test theories that predict things that are inaccessible, such as the many multiverse theories. You don't necessarily need access to them to prove they exist. Sort of like a crime investigation, if you get enough circumstantial evidence that correlate's with a theory's predictions then at some point you declare victory, and say the theory is sound. Then you just keep applying the theory until some new observation falls outside its predictions. So if there is a theory of everything that you think is beyond our grasp, we may be able to piece it together based on what that theory means for us here in our universe and our understanding.

Big Phoenix_sl said:

Well whatever it is its clearly not a planet, hasnt cleared its orbit!

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Mike Brown, the guy who "killed" Pluto and who was part of this planet 9 discovery has actually said that yes, it does meet the definition of a planet since it has significantly affected the orbits of nearby objects.

Planet 9: Astronomer Mike Brown's daughter told him to find new planet after he 'killed off Pluto' | Science | News | The Independent

A key part of the evidence is that Planet Nine seems to fulfil the third criterion for a true planet. The two astronomers have found that it exerts an influence on several objects in the Kuiper Belt beyond Nepture, the furthest known planet from the Sun.

"Is Planet 9 gravitationally dominant? I think it is safe to say that any planet whose existence is inferred by its gravitational effects on a huge area of the Solar System is gravitationally dominant," Dr Brown said.

"In short, no matter where it is, the one thing we know for sure about Planet Nine is that it is dominating the outer edge of the Solar System," Dr Brown said.

"That is enough to make it a planet by anyone's calculation."

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Frankly, I don't personally give a shit whether there's 8 planets, 10, or dozens. It's pretty obvious that as we continue to study other star systems that there is not going to be any fine line that you can draw between supposedly full fledged planets, dwarf planets, and so on. Instead we're going to find a massive variety of objects out there, some that look familiar and many that don't.

Furry_sl said:

As for the CMB, it could simply be distant stars.

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you might win the Nobel prize dude

30 year anniversary of the Challenger explosion. Doesn't seem like it's been that long. I remember watching it on TV at school.