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Chandra Chekuri

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SODA 2019 CFP is essentially the website info. Dates, PC etc are available. PC Chair is my colleague Timothy Chan.
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UIUC is looking for a new dean for its college of engineering.
Job posting below. Spread the word and apply if you are interested.
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ACM STOC 2017 was the first "Theory Fest" that happened in June 2017. There were a number of interesting talks and workshops, all of which were recorded. I was interested in the workshop videos and have been asking around to see why they have not yet been made available. Unfortunately I have not received much information. Posting this to see if some information can be gathered.

Update: SIGACT Chair Michael Mitzenmacher sent an email informing me that the videos are being uploaded to ACM DL website. I hope there will an official announcement when it is done.
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WSDM 2017 tries making half of its reviews double-blind and half the usual single-blind (reviewer knows who the authors are but not vice versa), with everything unblinded for the discussion phase of the review process. The results: well known authors, and authors from well-known institutions, get both more reviewers wanting to read their papers and higher review scores. Also, oddly, the blinded reviewers requested to read more papers.

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Avrim Blum sent an email about hosting workshops at TTI Chicago.
Looking forward to more people coming to Chicagoland.
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Voyager 1

Launched 40 years ago, the Voyagers are our longest-lived and most distant spacecraft. Voyager 2 has reached the edge of the heliosphere, the realm where the solar wind and the Sun's magnetic field live. Voyager 1 has already left the heliosphere and entered interstellar space! A new movie, The Farthest, celebrates the Voyagers' journey toward the stars:

What has Voyager 1 been doing lately? I'll skip its amazing exploration of the Solar System....

Exit from the heliosphere

On February 14, 1990, Voyager 1 took the first ever "family portrait" of the Solar System as seen from outside. This includes the famous image of planet Earth known as Pale Blue Dot. Soon afterwards its cameras were deactivated to conserve power and computer resources. The camera software has been removed from the spacecraft, so it would now be hard to get it working again. And here on Earth, the software for reading these images is no longer available!

On February 17, 1998, Voyager 1 reached a distance of 69 AU from the Sun - 69 times as far from the Sun than we are! In doing this, it overtook Pioneer 10 as the most distant spacecraft from Earth. Traveling at about 17 kilometers per second, it's moving away from the Sun faster than any other spacecraft.

That's 520 million kilometers per year — hard to comprehend. I find it easier to think about this way: it's 3.6 AU per year. That's really fast — but not if you're trying to reach other stars. It will take 20,000 years just to go one light-year.

Termination shock

As Voyager 1 headed for interstellar space, its instruments continued to study the Solar System. Scientists at the Johns Hopkins University said that Voyager 1 entered the termination shock in February 2003. This is a bit like a 'sonic boom', but in reverse - it's the place where the solar wind drops to below the speed of sound. Yes, sound can move through the solar wind, but only sound with extremely long wavelengths - nothing humans can hear.

Some other scientists expressed doubt about this, and the issue wasn't resolved until other data became available, since Voyager 1's solar-wind detector had stopped working in 1990. This failure meant that termination shock detection had to be inferred from the other instruments on board. We now think that Voyager 1 reached the termination shock on December 15, 2004 — at a distance of 94 AU from the Sun.


In May 2005, a NASA press release said that Voyager 1 had reached the heliosheath. This is a bubble of stagnant solar wind, moving below the speed of sound. It's outside the termination shock but inside the heliopause, where the interstelllar wind crashes against the solar wind.

On March 31, 2006, amateur radio operators in Germany tracked and received radio waves from Voyager 1 using a 20-meter dish. They checked their data against data from the Deep Space Network station in Madrid, Spain and yes — it matched. This was the first amateur tracking of Voyager 1!

On December 13, 2010, the the Low Energy Charged Particle device aboard Voyager 1 showed that it passed the point where the solar wind flows away from the Sun. At this point the solar wind seems to turn sideways, due to the push of the interstellar wind. On this date, the spacecraft was approximately 17.3 billion kilometers from the Sun, or 116 AU.

In March 2011, Voyager 1 was commanded to change its orientation to measure the sideways motion of the solar wind. How? I don't know. Its solar wind detector was broken.

But anyway, a test roll done in February had confirmed the spacecraft's ability to maneuver and reorient itself. So, in March it rotated 70 degrees counterclockwise with respect to Earth to detect the solar wind. This was the first time the spacecraft had done any major maneuvering since the Family Portrait photograph of the planets was taken in 1990.

After the first roll the spacecraft had no problem in reorienting itself with Alpha Centauri, Voyager 1's guide star, and it resumed sending transmissions back to Earth.

On December 1, 2011, it was announced that Voyager 1 had detected the first Lyman-alpha radiation originating from the Milky Way galaxy. Lyman-alpha radiation had previously been detected from other galaxies, but because of interference from the Sun, the radiation from the Milky Way was not detectable.

Puzzle: What the heck is Lyman-alpha radiation?

On December 5, 2011, Voyager 1 saw that the Solar System's magnetic field had doubled in strength, basically because it was getting compressed by the pressure of the interstellar wind. Energetic particles originating in the Solar System declined by nearly half, while the detection of high-energy electrons from outside increased 100-fold.


In June 2012, NASA announced that the probe was detecting even more charged particles from interstellar space. This meant that it was getting close to the heliopause: the place where the gas of interstellar space crashes into the solar wind.

Voyager 1 actually crossed the heliopause in August 2012, although it took another year to confirm this. It was 121 AU from the Sun.

What's next?

Voyager 1 will reach the Oort cloud, the region of frozen comets, in about 300 years. It will take 30,000 years to pass through the Oort cloud. Though it is not heading towards any particular star, in about 40,000 years it will pass within 1.6 light-years of the star Gliese 445.

NASA says that

The Voyagers are destined — perhaps eternally — to wander the Milky Way.

That's an exaggeration. The Milky Way will not last forever. In just 3.85 billion years, before our Sun becomes a red giant, the Andromeda galaxy will collide with the Milky Way. In just 100 trillion years, all the stars in the Milky Way will burn out. And in just 10 quintillion years, the Milky Way will have disintegrated, with all stars either falling into black holes or being flung off into intergalactic space.

But still: the Voyagers' journeys are just beginning. Let's wish them a happy 40th birthday!

My story here is adapted from this Wikipedia article:

You can download PDFs of posters commemorating the Voyagers here:
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Useful statistics. U of I seems to be doing better than some other places in the midwest in terms of hispanic and black enrollments but the overall numbers are distressing to see.
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