Reminder: I actually wrote everything that was needed, and then, my browser stopped responding! How great! You never know what the Universe is going to throw at you. I will try my best writting it again.Why? This is by far the most successful theory of cosmology ever developed, and all astronomers use it. I even implicitly use it in my own research (I use Lambda-CDM model with established values of cosmological parameters), since without it I would compute distances and sizes of galactic clusters incorrectly.
Also a word of caution on determining the stability of the two moons -- the orbital mechanics that can lead to instability are more complicated than "is there air or not?" Mutual interaction between the moons will be important, as well as between the moons and the Sun (this is already important for the current Moon), and the tidal interaction (which can cause orbits to expand or contract over time, also important for the current Moon.) Simulating the tidal interaction is probably beyond our ability to do here, but we can at least see the effects of the direct gravitational interactions with an n-body simulator.
This is a popular idea, but it doesn't fit with observations. For example, if the asteroid belt was once a planet, then it would have differentiated, producing a dense metallic core surrounded by mantle and crust. If it was then shattered, then every asteroid independent of size would show compositions related to that differentiated structure. But this is not what we observe. Instead, every large asteroid (e.g. Ceres) is differentiated on its own, while the smaller asteroids are more homogeneous mixtures. What this indicates is that the asteroid belt is a bunch of primordial material left over from the protoplanetary disk, and the gravitational effects of Jupiter prevented them from accreting into a single object.
This is a great and fundamental question, actually.
Science is based on building models which attempt to explain and predict what we observe. Sadly, we can never know if a model is "right" -- science just doesn't work that way -- but we can test between different models and see which one works best. For example, Newtonian gravity makes sufficiently good predictions in most circumstances, but in other circumstances you have to use General Relativity to be more accurate.
With any model, you can find out if it begins to diverge from reality by making observations. In the Newton vs. General Relativity example, you can find out that Newton is wrong in strong gravitational fields by looking at how much light is deflected when passing near the Sun. Or you can find out that it is wrong in weak gravitational fields (like here on Earth) if you have very high precision. But if you only care about motions in weak gravity, speeds much slower than light, and you don't have 10+ decimal points of precision, then you're fine to use Newton.
There is a whole field of science known as "Error Analysis", which deals with the gory details of how we figure out "how well we know something" (how confident we are in a measurement, or a model). It's a fascinating topic!
It will still be visible at night even if both worlds are mutually tidally locked. You just won't ever be able to see it from one side of the planet. From where you can see it, it will appear fixed in place in the sky, while the Sun and stars revolve around. Try it out in Space Engine -- there are some mutually tidally locked binary planets out there.
I hope this post didn't come across as being nitpicky or anything. Your answers are really good and a joy to read! I just wanted to correct any misconceptions, as they can also be interesting to learn and talk about, or lead to new questions. In my opinion learning is one of life's great pleasures.
Keep in mind there is something removed and added.Firstly, I'll explain why I don't believe in the Big Bang theory. I'll probably miss something, but never mind.
Ok, first question is when did it happen? It is speculated that Big Bang happened 13.8 billion years ago. Well, that's big number, lol. We 'have' time, now where did it happen? It is not sure where it happened. But, it 'can' be explained with Hubbles Universe and Space expantion. Where everything look like it is moving away from you. Ok, we have when and where. Now more complex question: Why? Why did it happen and also, how? Scientist have no idea why and how did that happen. But, in the Book from Stephen Hawking, he said that there isn't a necesary need for 'God' to start all that. He said that Big Bang could be just random. I didn't read the book, but it was mentioned in one episode from 'The Universe' from H2 channel. But something or someone had to start it. Question is what.
Everybody are referring to God as someone. He/She isn't a human. God is force. Then why are the bible and the Book of Genesis written? That is not a joke. I have a religion. I was religious more before. Now, i am not that much, but i still believe there is something, something that we still need to acomplish to have the ability to understand. Big Bang theory is created for one puropose. And that is getting poeple away from religion. It is easier to manipulate people that don't have fate. Don't get me as some mad scientist and conspirasy theorist that has aluminum foil on head, lol. I have more proof of God than hundreds of scienteist for Big Bang. I don't know if you want to hear my stories, but that would be off-topic. I am a scientist with religon. And I'll only believe in Big Bang theory if God 'itself' tell me that. And that would mean that God created Big Bang! So, there would be a creator needed.
Some atheist said that religion killed more people than any war. Smart words, but wars can be fought for religion.
What happens when you die? Do you go to heaven or hell? Or there is just nothing. Reincarnation? Maybe you go in what you believe and you see what you believe.
But enough of Big Bang and God. I am not convincing you in anything. You have freedom of believes, like everybody.
Second, about the moon. It was middle of the night when I was typing that. I wanted to make it bit longer, and I could make it. It looks like I am finding some exuses to why I didn't explain better.
Third, about the asteroid belt. I indeed believe that there was something there. And something big happened. Maybe Ceres was a moon and there was planet. And then it got shattered into million fragments. There's a lot of telling there.
Now, Fourth. That's about measurments and right things. Many people believe that now we are at the final form of knowledge and that our meassurements are correct. Well, that's wrong. Same thing was hundreds of years back. Like Newton and his laws and his light observation. But people in that time, like in any era, they didn't want to go in the future. Only those people that wanted, they had hard time getting us where we are today.
Now, Fifth, the Venus thing... That could be simulated in the Universe Sandbox 2 or SE like all other things here. And I tought that that if they are tidally locked, then they are facing same side always.
You are probably right more than me, you have years of experience and, what I know. I just hope what we will find answers to anything in our lifetime.
Looks like our lives are just questioning and answering infinite things.I would like to talk about other things also, rather than just questioning and answering. I am curious if you watched season 1 of 'Genius' TV show from National Geographic channel. If you did, tell me some of your reviews. If you didn't, I recommend watching it.
Hope it is written good enough.
