Videos by topic: UNIVERSE

Sounds of the Skies

Hear the Spacetime Ringing
[3.23.16]

The effect of these gravitational waves is to squeeze and stretch space. If you were floating near these black holes, you would literally be squeezed and stretched. If you were close enough, you would feel the difference between the squeezing and stretching on your face or your feet. We’ve even conjectured that your eardrum could ring in response, like a resonant membrane, so that you would literally hear the wave, hear it even in the absence of a medium like air. Even though we think that empty space is silent, in these circumstances you would hear the black holes collide but you wouldn’t see them; it would happen in complete darkness. The two black holes would be completely dark, and your only evidence of their collision would be to hear the spacetime ringing.

JANNA LEVIN is a professor of physics and astronomy at Barnard College of Columbia University. She is the author of How the Universe Got Its Spots; A Madman Dreams of Turing Machines; and most recently, Black Hole Blues and Other Songs from Outer SpaceJanna Levin's Edge Bio Page 


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The Exquisite Role of Dark Matter

[6.10.15]

It is definitely the golden age in cosmology because of this unique confluence of ideas and instruments. We live in a very peculiar universe—one that is dominated by dark matter and dark energy—the true nature of both of these remains elusive. Dark matter does not emit radiation in any wavelength and its presence is inferred by its gravitational influence on the motions of stars and gas in its vicinity. Dark Energy, discovered in 1998, meanwhile is believed to be powering the accelerated expansion of the universe. Despite not knowing what the dark matter particle is or what dark energy really is, we still have a very successful theory of how galaxies form and evolve in a universe with these mysterious and invisible dominant components. Technology has made possible the testing of our cosmological theories at a level that was unprecedented before. All of these experiments have delivered very exciting results, even if they're null results. For example, the LHC, with the discovery of the Higgs, has given us a lot more comfort in the standard model. The Planck and WMAP satellites probing the leftover hiss from the Big Bang—the cosmic microwave background radiation—have shown us that our theoretical understanding of how the early fluctuations in the universe grew and formed the late universe that we see is pretty secure. Our current theory, despite the embarrassing gap of not knowing the true nature of dark matter or dark energy, has been tested to a pretty high degree of precision.                      

It's also consequential that the dark matter direct detection experiments have not found anything. That's interesting too, because that's telling us that all these experiments are reaching the limits of their sensitivity, what they were planned for, and they're still not finding anything. This suggests paradoxically that while the overall theory might be consistent with observational data, something is still fundamentally off and possibly awry in our understanding. The challenge in the next decade is to figure out which old pieces don't fit. Is there a pattern that emerges that would tell us, is it a fundamentally new theory of gravity that's needed, or is it a complete rethink of some aspects of particle physics that are needed? Those are the big open questions.

PRIYAMVADA NATARAJAN is a professor in the Departments of Astronomy and Physics at Yale University, whose research is focused on exotica in the universe—dark matter, dark energy, and black holes. Priyamvada Natarajan's Edge Bio Page


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Layers Of Reality

[5.28.15]

We know there's a law of nature, the second law of thermodynamics, that says that disorderliness grows with time. Is there another law of nature that governs the complexity of what happens? That talks about multiple layers of the structures and how they interact with each other? Embarrassingly enough, we don't even know how to define this problem yet. We don't know the right quantitative description for complexity. This is very early days. This is Copernicus, not even Kepler, much less Galileo or Newton. This is guessing at the ways to think about these problems.

SEAN CARROLL is a research professor at Caltech and the author of The Particle at the End of the Universe, which won the 2013 Royal Society Winton Prize, and From Eternity to Here: The Quest for the Ultimate Theory of Time. He has recently been awarded a Guggenheim Fellowship, the Gemant Award from the American Institute of Physics, and the Emperor Has No Clothes Award from the Freedom From Religion Foundation. Sean Carroll's Edge Bio Page


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Formulating Science in Terms of Possible and Impossible Tasks

[12.6.14]

It turns out that in the constructor theoretic view, humans, or knowledge creating systems, are quite central to fundamental physics in an objective way and not an anthropocentric way. This is a very deep change in perspective. One of the ideas that will be dropped if constructor theory turns out to be effective is that the only fundamental entities in physics are laws of motion and initial conditions. Of course they are, but in order for physics to accommodate more of physical reality, there needs to be a switch to this new mode of explanation, which accept is a scientific explanation more than predictions. The ideal prediction will be complemented with the idea of statements about what tasks are possible and impossible and why.

CHIARA MARLETTO is a Junior Research Fellow at Wolfson College and Postdoctoral Research Assistant at the Materials Department, University of Oxford. Chiara Marletto's Edge Bio Page


 

Chiara Marletto on Extinction

[11.6.14]

There is a new fundamental theory of physics that’s called constructor theory, and was proposed by David Deutsch who pioneered the theory of the universe of quantum computer. David and I are working this theory together. The fundamental idea in this theory is that we formulate all laws of physics in terms of what tasks are possible, what are impossible, and why. In this theory we have an exact physical characterization of an object that has those properties, and we call that knowledge. Note that knowledge here means knowledge without knowing the subject, as in the theory of knowledge of the philosopher, Karl Popper.

We’ve just come to the conclusion that the fact that extinction is possible means that knowledge can be instantiated in our physical world. In fact, extinction is the very process by which that knowledge is disabled in its ability to remain instantiated in physical systems because there are problems that it cannot solve. With any luck that bit of knowledge can be replaced with a better one. 


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What's New In The Universe

Direct Evidence Of Cosmic Inflation
[3.17.14]

Even though cosmology doesn't have that much to do with information It certainly does have to do with revolution and phase transitions, in fact phase transitions in both the literal and the figurative sense of the word.
 


 

What's New In The Universe

Direct Evidence Of Cosmic Inflation
[3.17.14]

Inflationary theory itself is a twist on the conventional Big Bang theory. The shortcoming that inflation is intended to fill in is the basic fact that although the Big Bang theory is called the Big Bang theory it is, in fact, not really a theory of a bang at all; it never was.

 


 

What's New In The Universe

Direct Evidence Of Cosmic Inflation
[3.17.14]

Think about it this way: previously we thought that our universe was like a spherical balloon. In the new picture, it's like a balloon producing balloons, producing balloons. This is a big fractal. The Greeks were thinking about our universe as an ideal sphere, because this was the best image they had at their disposal. The 20th century idea is a fractal, the beauty of a fractal. Now, you have these fractals. We ask, how many different types of these elements of fractals are there, which are irreducible to each other? And the number will be exponentially large, and in the simplest models it is about 10 to the degree 10, to the degree 10, to the degree 7. It actually may be much more than that, even though nobody can see all of these universes at once.


 

THINK ABOUT NATURE

A Conversation with
[5.14.13]

Feynman once told me, "Whatever you do—you're going to have to do crazy things to think about quantum gravity—but whatever you do, think about nature. If you think about the properties of a mathematical equation, you're doing mathematics and you're not going to get back to nature. Whatever you do, have a question that an experiment could resolve at the front of your thinking." So I always try to do that.

LEE SMOLIN is a founding and senior faculty member at Perimeter Institute for Theoretical Physics in Waterloo, Canada. He is also Adjunct Professor of Physics at the University of Waterloo and is a member of the graduate faculty of the Department of Philosophy of the University of Toronto. His is the author od Time Reborn: From the Crisis in Physics to the Future of the Universe. Lee Smolin's Edge Bio Page

 


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CONSTRUCTOR THEORY

A Conversation with
[10.22.12]

There's a notorious problem with defining information within physics, namely that on the one hand information is purely abstract, and the original theory of computation as developed by Alan Turing and others regarded computers and the information they manipulate purely abstractly as mathematical objects. Many mathematicians to this day don't realize that information is physical and that there is no such thing as an abstract computer. Only a physical object can compute things.

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I think it's important to regard science not as an enterprise for the purpose of making predictions, but as an enterprise for the purpose of discovering what the world is really like, what is really there, how it behaves and why.
 

DAVID DEUTSCH is a Physicist at the University of Oxford. His research in quantum physics has been influential and highly acclaimed. He is the author of The Beginning of Infinity and The Fabric of Reality. David Deutsch's Edge Bio Page


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