"Probing the Dark Universe" - A Lecture by Dr. Josh Frieman
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In this one-hour public lecture Josh Frieman, director of the Dark Energy Survey, presents an overview of our current knowledge of the universe and describe new experiments and observatories. Over the last two decades cosmologists have made remarkable discoveries: Only 4 percent of our universe is made of ordinary matter - atoms, molecules, etc. The other 96 percent is dark, in forms unlike anything with which we are familiar. About 25 percent is dark matter, which holds galaxies and larger-scale structures together and may be a new elementary particle. And 70 percent is thought to be dark energy, an even more mysterious entity which speeds up the expansion of the universe. Josh Frieman is senior staff scientist at the Fermilab and Professor of Astronomy and Astrophysics and member of the Kavli Institute for Cosmological Physics at the University of Chicago. The Dark Energy Survey is a collaboration of 300 scientists from 25 institutions on 3 continents, which built and uses a powerful 570-Megapixel camera on a telescope in Chile to carry out a 5-year survey of 300 million galaxies and thousands of supernovae to probe dark energy and the origin of cosmic acceleration.
Comments
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Great lecture, and very informative!
It's funny to see these hobby astronomers in the comments, trying to explain something that hasn't been figured out by the smartest people for over 80 years :D
Yeah sure guys, the answer was X instead of Y. Why didn't we think of that? xD -
I'm no cosmologist but I still don't buy into dark matter/energy no matter how many of these documentaries and talks I watch.
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I am new to this theory, but could it be that some cohesive force/forces which work/s at massive levels of universe, could have become weak beyond a certain distance, and thus causing universe to expand at an accelerated pace? Or it could be that the Big Bang theory itself is flawed/incomplete, causing all scientists to come up with flawed/incomplete equations. The best idea would be to construct the nature of dark energy and dark matter with their observable characteristics, rather than to try to describe them with the help of our understanding/equations of visible matter and energy. And in a situation of weakening attractive forces over distance, the objects should naturally speed up.
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interesting - a couple of points though, maybe need to take into account other possibilities. The acceleration premise of calculation via type1A explosions which are shown to be fainter than expected from within the early universe, thus launching the suggestion that the universe is accelerating; i am wondering if it could be that early universe type 1A explosions were actually fainter due to there being less mass and light as there is now or, what about the 'lensing' effect that maybe increases luminosity for closer/newer type 1A explosions - suppose that just wasn't present in the early universe and so, the explosions appear fainter? thank you for the presentation and for inspiring these questions.
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Before abandoning the law of conservation of energy altogether we should change our definition of total energy. If we take the total energy as mass plus energy plus spacetime curvature we can maintain conservation of energy. This is taking the GR equations which equate spacetime curvature to a mass energy distribution and putting all the terms on the left side of the equation and zero on the right. The total energy of the universe is always zero.
Then with this definition of total energy there is the possibility of mass energy being derived from the expansion of spacetime where the expansion results in an increased radius of curvature.
https://www.academia.edu/5009126/The_evolution_of_the_universe
Richard -
There is another explanation for the observations of distant supernovae. We have to give up the cosmological principle and assume that the universe is finite and bounded. This means that the universe has a centre and we can estimate our position using Hubbles law with reference to the CMBR rest frame. This calculation shows that the Milky Way galaxy is an estimated 26 million light years from the centre of the universe.
From this preferred position close to the centre of the universe we observe distant supernovae but it is variation with distance that we are detecting. The rate of expansion of space varies depending on the distance from the centre of the universe.
https://www.academia.edu/5009126/The_evolution_of_the_universe
Richard -
I have a different theory about galaxy formation where the galaxies formed individually at specific locations in space with a gamma ray burst and a huge quantity of neutrons. Single neutrons can decay into a proton and an electron and then form hydrogen. However, neutrons may collide to form neutron groups of two or more neutrons which would be stable just as an atomic nucleus is stable.
This process would result in a large gas cloud of hydrogen plus an invisible halo of neutron groups which forms the dark matter halo.
So my conclusion is that dark matter consists of neutron groups.
https://www.academia.edu/5009126/The_evolution_of_the_universe
Richard -
we never use miles...we use SI units...km meters cm.. etc..
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the most distant visible object is 30 billion ly away....light is halfway to earth buddy
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7m28s What is the total angular momentum of a "typical" galaxy, say, Andromeda or ours: the Milky Way?
What is its moment of inertia? I ought to force myself to do these simple calculations myself. -
Does anyone get the idea that he has no idea what he is talking about?
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I wonder, has anyone ruled out "Quantum Field Fluctuations of the Gluon/Quark fields in a Vacuum" as to a potential candidate for "Dark Energy?"
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the point is, handsome white guy must marry beautiful white girl, that is the point.
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~ 1:34:00: "It's not because the region of the solar system is somehow deficient in dark matter, it's that the density of dark matter is much lower than that [of 'baryonic; matter]".
Our solar system is in free-fall with respect to any blobs of dark matter to which it is gravitationally bound. Disregarding tidal effects, the local ratio of the density of dark matter vs. baryonic matter has nothing to do with it. -
It's interesting that he says that Quantum theory indicates that the vacuum has infinite energy, so "that much be wrong". Why must that be wrong? I thought common sense went out the window with Quantum theory, so that seems like a bold statement.
If you look at the amount of energy there appears to have been released from 'nothing' in the Big Bang, that looks awfully like the near infinite release of energy that might, under some circumstance, be released from empty space. -
Uhhh horrible umm lecture.
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Why is he talking about science while using miles?
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Just skip to 3:50. You’re welcome. :)
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one of your own 971 has already done this back in 2007, at this time, but she saw not the truth, she saw what she wanted to see.
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So we've known about dark matter for about 80 years or so and we still have no freaking clue what it is?! Awesome. I'm on it.
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