One thing she said that struck me was that dark energy does not change in density, that it is the same despite the expansion of the universe. It sounds like dark energy may well be the reason that the universe is expanding, like it is constantly increasing and causing everything to expand as a result, or is itself somehow expanding and taking everything observable with it. It also sounds like the very fabric of space-time, or a major component of it.
Dark energy is the name for the cause of the unexplained acceleration of the expansion. We call it dark energy because we don't know what it is. Due to the force of gravity, the expansion should be decelerating, not accelerating. Dark matter is the name for unidentified mass that is seen to effect galactic structures and movement. We call it dark because we can measure its effects but it is invisible.
You Say, "Dark Matter" Moi Says, "Show Moi". And no arithmetic games of expected mass, seen mass, etc. Nor artist conceptions. Show me! Moi No Dark Matter No Dark Energy No Anti Dark Matter No Anti Dark Energy etc. FREE Meng Wanzhou!
Ah, well there we go. I had it backwards, in a way. Dark energy is there to explain the expansion. I did know that much about dark matter, though. I see she is proposing that dark matter may feature a variety of particle types akin to regular matter, and that this may give rise to a disc of dark matter that may have a strong enough gravitational effect to perturb the orbits of Oort Cloud objects, and that is where the (possible) tie-in with the cretaceous-paleogene extinction event comes in. It's good to see someone suggesting ideas that may be lead to new testing and discoveries. Personally, I suspect that if anything perturbed such an object, it was most likely a passing mass of some kind, like a star or other body. Could have been something as innocuous as a gas cloud, I imagine. With gravity being so weak that far out, there are many possibilities for such distant objects being perturbed. In fact, they probably perturb one another with some frequency.
When I started college, it was believed by many that physics was nearly complete. Then, over a fairly short period of time, physicists said "ooops! We missed 95% of the universe." Wouldn't it be amazing if there is something akin to an entire periodic table of dark matter. I had never considered that possibility until she mentioned it. The fact is that the measurements of the expansion of the universe had margins of error that included both positive and negative acceleration. But it was assumed that the acceleration must be negative due to gravity. So the possibility of a positive acceleration was dismissed. But as the measurements became more and more accurate, people began to realize there was a problem.
Normal matter and its gravitational interactions seem to be like solids floating on the surface of a liquid, tending to clump together in an outwardly, roughly similar manner. The universe is like a three-dimensional version of that mostly 2D observed phenomenon. Man, what is the universe? What the hell has given rise to all of this? What lies beyond? What is the highest level of existence? Is it this or something beyond it? Endless questions.
I wish i understood what you wrote, but all this “dark”. Stuff is at the edge of my comprehension One thing she said that i thought was interesting was that, while she acknowleged her ideas were speculative, she pointed out that such out if the box ideas are a necessary precursor to new discoveries. They give ideas of patterns and phenomena to search for within a mass of data
I was intrigued by her idea that dark matter might be complex like the matter we are familiar with. It might also radiate non electromagnetic energy (dark light) which we cannot see.... mind blowing ideas
It made me think of neutrinos when she mentioned that "dark light" idea. I suppose it would be something like that, a type of fast-moving particle that we are barely if at all able to detect.
Influenza nearly wiped us out not so long ago? Yes, it nearly wiped us out globally?? Well let's hope you're right . . . I'm too young to die!
What lies beyond the known Universe? Does light and dark matter and all energy go on forever? Perhaps dark matter/energy is a canvas in which light matter/energy can expand indefinitely? Perhaps this dark matter/energy and it's gravitational affects 'canvas' allow/encourage light matter/energy to promulgate in a somewhat organized fashion? Gravitational affects of dark matter/energy can both push and pull light matter/energy to expand without diluting dark matter? Maybe the BB started the local expansion and dark matter sustains and grows the expansion?
Here is a thought experiment to try. Imagine that you have a space ship capable of reaching the edge of the known universe where the cosmic background radiation exists. When you get to the edge of the known universe and you look back in the direction that you just came from you can only see half of the known universe because of the speed of light. But when you look in the direction of travel what do you see instead? Is there nothing at all to see in that direction? Or is there matter in the form of galaxies that have already passed beyond the edge of the known universe before we started our recent observations? Logically it has to be the latter given that the universe is expanding in all directions which means that whatever was already at the edge of the known universe a year ago would have now been pushed out into space beyond what our current instrumentation can detect. How long has this been happening and how much is already there? All matter might just be ordinary matter and we are just calling it Dark Matter because we can't detect it. That is one of the hypothesis that still hasn't been tested because we lack the necessary instrumentation. However if we could built a spacecraft that could carry our instruments a hundred million light years away and then see if it can detect anything beyond what our instruments are detecting here on Earth that would answer that question.
Oh no! I haven't heard that one before. It looks like a dipplydopplydiddlydocus to me. They had feathers doncha know?
I think we would be able to test this last idea of yours. We can detect dark matter indirectly - by noticing gravitational affects. Dark matter is not evenly spread across the universe - it tends to be globbed around galaxies somewhat like other matter, and the amount of dark matter isn't proportional to the amount of other matter. It would seem that science can study the attractive and/or repulsive forces of dark matter by comparing the interaction of galaxies that have different percentages of dark matter. Just my guess, of course!
Thank you... The edge of the known Universe is the farthest normal matter/energy that we can detect...about 13.8 billion light years...right? I thought that cosmic background radiation existed in all areas of the known Universe...like where I'm sitting now and 13.8 billion light years away? Assuming I could ever catch up to the edge of the known Universe, and then look back, with my existing instrumentation, why wouldn't I still be able to see the same 13.8 billion light years? When I look in the direction of travel, I should see normal matter/energy as far as my instrumentation can detect...which should be about 13.8 billion light years...assuming the Universe continues to those distances. If the actual Universe ends prior to an additional 13.8 billion light years, like only 10 billion light years, this might tell me the actual Universe is ~13.8 + 10.0 =23.8 billion light years in size plus whatever expansion might be. So if we can detect light 13.8 billion light years away, and we know the Universe has been expanding since the BB, why do we say the Universe is 13.8 billion light years in size when we know it's actually something much larger...like 50-90 billion light years? Assuming the Universe is infinite? I don't see how there can be a hypothesis that dark matter is just light matter that we don't know how to detect? If anything I would think dark matter belongs in the family of gravity?? Both are invisible yet both have influence...thank you again...
One thought is that if we can determine the age of the visible universe, then the rest of the universe must be that age, too. We can't have a BB of the visible universe that doesn't include the whole. We CAN have a universe that is larger than what is visible, as expansion can be at a rate that exceeds the speed of light. Each unit of distance is expanding. Over large distances the expansion of each unit of distance adds to greater than the speed of light. Thus, sizing the universe based on the speed of light isn't that direct - one also needs to know about the expansion rate, which is not constant over time. Physicist tell us that the expansion rate at the beginning was stupendously large, while the expansion rate today is far, far less. OK, I've never been able to understand arguments that suggest this universe is infinite in size simply becauuse that would mean that an infintely large universe came from a point source expansion over a fixed period of time. If anyone can fix me on that, I'd love it. If the answer is that this universe is folded back on itself, fine, but that doesn't mean that it is infinitely large, right?
Our technology today lets us detect light from 13.8 billion years ago so this establishes the visible Universe. Since the Universe is expanding, we know there is normal matter well beyond the 13.8 billion light years we can detect. If we assume the Universe is infinite, then we can assume that the actual size is 13.8 billion (+) whatever the total expansion has been, or, the total of expansion since the BB. If the Universe is not infinite, and at some point beyond 13.8 billion light years the expansion is stopped, there must be some pretty messy collisions happening! If this were happening I suspect we would be detecting forms of radiation from 'out there'? Or there could be a gradual slowing of expansion until it stopped but we would see this as well...and at that point is the Universe static or does it contract on itself? I doubt humanity will last long enough to ever know the answers...
