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Ask me anything physics related! I'll keep to laymans terms and no math if possible. :-) Choose from cosmology to string theory. What about the Universe doesnt make sense? Black holes? Quantum electrodynamics? Planetary formation? M-Theory and Branes? Higgs Boson? Quantum tunneling?
Lets see where the conversation goes! :-) And if you are reading a question yet to be answered and you know the answer, chime in too! Lets try to make this the longest Science thread ever on city-data.
Ben the Physicist
What is your opinion of dark energy and how it relates to possible superluminal travel and transmission of information?
What is your opinion of dark energy and how it relates to possible superluminal travel and transmission of information?
Superluminal travel and transmission of information are the same thing. Alcubierre drive all over again right? I dont believe this has any merits at all as previously mentioned, however, there's a lot of papers on this -- even ones I've reviewed and inputted pages of criticism. In my expert opinion, I believe that once you use two wormholes to connect to each other (if even possible) their creation and subsequent connectivity would result in their immediate decay. Unless we discovered that our Universe is a Godel Universe, which I dont believe to be true either. Still theories working on this very subject are submitted and published with frequency, but each one is full of speculation on "if this would work then this could work". There's a lot of unknown knows. I prefer to work with known unknowns. :-)
I tried finding a definition of Godel Universe but it made my head hurt. Can you explain it in simple terms?
Certainly. It's called the Godel Metric, or the Godel Solution. Its one (of many) exact solutions to Einsteins's field equations.
What is important, is that our Universe isnt rotating. It isnt spinning. It isnt revolving around anything or on an axis or on a point. It's simply here, and expanding.
A Godel Universe is one that would be rotating on an axis, and *not* expanding. It is *not* a real version of our Universe. There is a lesser known (because its wrong) solution to this that does allow expansion and rotation, but alas because its wrong, it still isnt representative of our Universe.
What makes it worth knowing about, is that since it is an exact solution to field equations, means that in a *different* Universe out there, somewhere, that relativity could be present in a similarly structured Universe to ours. It helps physicists work out possibilities into Universes that arent ours, that's all. :-)
Currently there is no scientific consensus how to combine quantum mechanics with relativistic gravity. Science is currently not able to make predictions about events occurring during intervals shorter than Planck time (~5.39106E−44 seconds) or distances shorter than one Planck length (~1.616E-35 meters). Without an understanding of quantum gravity the physics of the Planck Epoch (from zero to approximately 1.0E−44 seconds after the Big Bang) remains in the realm of pure speculation.
After cosmic inflation ends (1.0E-33 seconds after the Big Bang), the universe is filled with a quark–gluon plasma. From this point onwards the physics of the early universe is better understood, and less speculative. At this point the universe is still entirely energy, no matter yet exists.
During the Hadron Epoch (1.0E-6 seconds to 1 second after the Big Bang) the universe cools off enough to form hadrons and baryons (such as protons and neutrons). It is during this period that matter first comes into existence.
Is it understandable how the universe went from hadrons and baryons shortly after the big bang to hundreds of billions of galaxies that the universe is said to contain today (let alone all the dark matter)?
Was all the matter that presently exists in the universe contained in those hadrons and baryons during the Hadron Epoch? Or did most of our universe's matter spontaneously come into existence sometime after the Hadron Epoch?
Is it understandable how the universe went from hadrons and baryons shortly after the big bang to hundreds of billions of galaxies that the universe is said to contain today (let alone all the dark matter)?
Was all the matter that presently exists in the universe contained in those hadrons and baryons during the Hadron Epoch? Or did most of our universe's matter spontaneously come into existence sometime after the Hadron Epoch?
There are still many aspects of the early universe that are not fully understood. Which is why I said that beginning with the Hadron Epoch our understanding of the universe becomes "less speculative." That is not the same thing as saying we are "all knowing."
Unless you are aware of white holes that science has not found, there is no known means of spontaneously creating matter. According to the law of conservation of energy, energy can not be created nor destroyed, but it can change form.
There's a lot of unknown knows. I prefer to work with known unknowns. :-)
LOL! That reminded me of Donald Rumsfeld's famous quote:
"The message is that there are no "knowns." There are things we know that we know. There are known unknowns. That is to say there are things that we now know we don't know. But there are also unknown unknowns. There are things we do not know we don't know."
Isn't "matter" mostly space? A rock is made of various molecules, which are made of atoms, which are made of Protons, neutrons and electrons, which are made of smaller particles (well I don't know about the electron), and on and on.
That said...if space is expanding...isn't the space between the itsy bitsy stuff expanding too? Isn't everything getting bigger? Thats the thing I can't quite grasp. Is gravity too weak to stop the expansion once you get a certain distance apart?
Isn't "matter" mostly space? A rock is made of various molecules, which are made of atoms, which are made of Protons, neutrons and electrons, which are made of smaller particles (well I don't know about the electron), and on and on.
That said...if space is expanding...isn't the space between the itsy bitsy stuff expanding too? Isn't everything getting bigger? Thats the thing I can't quite grasp. Is gravity too weak to stop the expansion once you get a certain distance apart?
Structures the size of galaxy clusters or smaller are gravitationally bound; the expansion of the universe is far too small at such scales to overwhelm this. The forces holding an atom together are many orders of magnitude stronger than gravitation, so I doubt any atoms will be expanding apart for a very, very, very long time. (If ever, there are scenarios where this happens and where it doesn't.)
Structures the size of galaxy clusters or smaller are gravitationally bound; the expansion of the universe is far too small at such scales to overwhelm this. The forces holding an atom together are many orders of magnitude stronger than gravitation, so I doubt any atoms will be expanding apart for a very, very, very long time. (If ever, there are scenarios where this happens and where it doesn't.)
Please correct me where I am wrong. This stuff called space...which is made of something we can't measure yet...is expanding and carrying us along with it. So even though we may be traveling extremely fast since there is no velocity (or maybe only a little) difference between us and space our perspective is that we are not moving...therefore not violating the speed of light law.
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I dont believe this has any merits at all as previously mentioned, however, there's a lot of papers on this -- even ones I've reviewed and inputted pages of criticism. In my expert opinion, I believe that once you use two wormholes to connect to each other (if even possible) their creation and subsequent connectivity would result in their immediate decay. Unless we discovered that our Universe is a Godel Universe, which I dont believe to be true either. Still theories working on this very subject are submitted and published with frequency, but each one is full of speculation on "if this would work then this could work". There's a lot of unknown knows. I prefer to work with known unknowns. :-)
