The nature of dark energy

Astronomers have used many different methods to try and figure out the nature of dark energy: the mysterious substance comprising roughly 70% of the total energy in the universe and responsible for accelerating its expansion. These including measuring the distance to Type Ia supernovae, measuring the mass of galaxy clusters, the clumping of galaxies, and not strong lensing of more distant galaxies by nearby galaxy clusters. Read more about it here and here and here. Hopefully all these methods keep on agreeing.

Mapping the Universe

One of the most powerful tools we have in trying to understand the properties of the universe as a whole (e.g how much normal matter is in there, how much dark matter, how much dark energy? - i.e, the entire field of cosmology) are galaxy surveys - figuring out both how many galaxies there are at a particular redshift / time after the Big band and how close they are too each other. Traditionally, this has been done using large optical surveys like the Sloan Digital Sky Survey - which finds galaxies by detecting their star light. Galaxies also contain a lot of hydrogen gas, which when cold emits light at particular wavelength - 21 cm, in the radio band. It is possible to a galaxy survey by detecting this emission, which may be more sensitive to low mass galaxies with few stars than optical surveys. Such radio galaxy surveys are now feasible using telescopes like NRAO's 100m Green Bank Telescope and NAIA's Arecibo Telescope. To read more about these surveys, and how they can help determine the answer to such questions like "the nature of dark energy" read this and this and this article, with the full research articles here and here(Subscription, required).

What is Dark Energy?

Maybe it's isn't so mysterious after all, or it is. Read the debate here. The sad thing is, the pessimist in me wonders if we can ever find out...

Neutrinos they are very small.

They have no charge and have no mass
And do not interact at all.

Well, so said John Updike. They don't have no mass, but very very little mass, and it now appears that they have even less mass than people thought as you can read here. And while to them "The earth is just a silly ball," by detecting them deep underground you can learn quite about the Earth, which you can read about here. Enjoy, and my apologies for butchering that quite cute poem.

Yet more evidence for an accelerating universe

This time coming from distortions in the shapes of galaxies observed by the Hubble Space Telescopes. How, you ask? Go here to read the details. And if doesn't make sense, please leave questions below. I like questions. Maybe I can even answer them.

First results from ESA's Planck

Planck, the latest satellite to measure the properties of the Cosmic Microwave Background - essentially residual heat from the Big Bang, has released its first results and it looks very good indeed. Go here and
here to look for yourself. Enjoy!

Gravitational Waves Result

I promise to do a whole series devoted this, relatively soon-ish, but as I've talked about on previous shows, one of the key predictions of General Relativity is that objects orbiting around each other while produce ripples in space-time (and how we interact with space-time through gravity) called gravitational waves. While indirect evidence that gravitational waves has been gathered by measuring the orbital period of pulsars around each other, LIGO and other experiments are trying to detect them directly on the Earth. To listen to a recent webcast on this project - and an interesting non-detection of gravitational waves from the early Universe, go here. Hope you enjoy!

The oldest blobs in the universe

Yes, "blobs" is the scientific term they use. Given that this article is about diffuse clouds of gas in the early universe, it is a pretty appropriate term.

March 18th radio show: String Theory

Broadcast almost two months ago but finally available here is the March 18th episode of this radio show where, in addition the usual Astronomy calendar, Prof. Matt Kleban of NYU talks about string theory and how it can actually impact in cosmology. As always, please email or post below and questions, comments, or concerns you might have. Thanks for listening, and sorry for posting this so late.

February 25th Radio Show: The Earliest Universe

Broadcast a long time ago but finally available here is the February 25th episode of this radio show, which in addition to the usual calendar features an interview with Katie Mack of Princeton University on the early universe. As always, please email me or leave below any questions, comments, or concerns you might have. Thanks a lot for listening, and your patience!

February 18th Radio Show: "The Theory of Everything"

Over the past few months, I've done my best to explain what Astronomers believe is going on in the universe. An equally interesting and difficult question is how did the universe get to be the way it is, and that is focus of the very-delayed-but-finally-posted February 18th episode of this radio show. Thanks a lot for listening!

February 11th Radio Show: Cosmology

Over a month after it first aired, here is the February 11th radio show on cosmology, where I discuss why astronomers think the universe is mostly composed of dark matter and dark energy. Hope you enjoy and, as always, please leave below or email me any questions, comments, or concerns you might have. Thanks for listening!

Past Interview: Dr. Daniel Babich (Caltech)

To supplement the February 4th radio show on cosmology, here is a past interview I conducted with Dr. Dan Babich of Caltech on the Cosmic Microwave Background. Hope you enjoy and, as always, thank you for listening!

February 4th Radio Show: Cosmology

Too long coming, I know, but here is the February 4th episode of this radio show, where the "tour of the Universe" begins its close with the first episode on cosmology - the study of the Universe as a whole (as opposed to studying individual objects in the universe). Hope you enjoy and, as always, please email me or leave below any questions, comments, or concerns you might have. Thank you very much for listening.

Free Astronomy movie Tomorrow!!!!

Tomorrow night, as part of the Imagine Science Film Festival going on in NYC (look at the calendar for events), will be the NY premiere of the new documentary "BLAST!", directed by Paul Devlin, on the launch of the Balloon-borne, Large Aperture, Sub-millimeter Telescope (BLAST!) from Antarctica to study the cosmic microwave background (CMB). It sounds likes a great movie. For more information on the showing, which is tomorrow night (Oct. 23rd) at 7:30 PM at Baisley Powell Elebash Recital Hall in the CUNY Graduate Graduate Center (365 5th Ave at 34th Street), go here. For more information on this movie, check out their website. And for more information on the CMB, listen to my interviews with Dr. Daniel Babich and Dr. Gary Hinshaw. Enjoy!