*Proper spellings are Alex Filippenko and Astrophysicist. As a fellow Redditor (flyblackbox), I was helping Alex get used to this platform, and in haste, I posted misspellings in this AMA title. Thank you for understanding.

Today is March 14th, also known as Pi day, 3/14!

piZone is dedicated to celebrating this phenomenon and I have officially been named the site's 'Pi Piper'.

My name is Alex Fillipenko, Astronomer and Astrophysicist professor at UC Berkeley, national professor of the year 2006, and frequent guest on History Channel's The Universe, as well as other science related documentaries.

I'm happy to discuss any topic related to mathematics, education reform, higher education, astronomy, or astrophysics. Miscellaneous questions will be considered

Answers will begin posting at 11:30AM EST.


[1] http://i.imgur.com/kDLQgrr.jpg [2] http://youtu.be/kSXnbbfpK2U


"The citizens of our nation need a strong understanding of math and science. Pi can be used as a hook to get kids interested in these subjects. In 2009, the U.S. House of Representatives passed a resolution (HR 224) that March 14th shall be known as National Pi Day (3.14...). This declaration extols the importance of learning about math and science in our schools. Everyone can take advantage of the day to teach children and adults about pi and mathematics. It is intended to be a fun and interactive experience for all.

Pi Day is now celebrated throughout the world, even in countries that don't list the month and day in that order."

π = 3.14159265358

Alex Filippenko must get on a flight to Hawaii, where he will attend the W. M. Keck Observatory 20th Anniversary celebration.

Tomorrow (Friday, March 15, 2:10-2:40 pm Pacific Daylight Time), he will give a talk entitled "Nobel Worthy: The Accelerating Expansion of the Universe."

If you wish, you can watch it live using Keck Observatory’s USTREAM channel: http://www.ustream.tv/channel/explore-the-universe-from-keck-observatory

During the flight, he must finish preparing the lecture, but will answer some additional questions in the future, as time permits.

Comments: 1134 • Responses: 36  • Date: 

AlexFilippenko214 karma

Let the questions pi throwing begin!


Brohio39 karma

where is this guy

AlexFilippenko123 karma

Just got back online, I am reading through the questions now. I apologize for the delays, I have been flying a bit. (Pi in the Sky!)

NotSafeForWumbo136 karma

How much of what's on The History Channel and The Science Channel is sensationalized? I feel like when watching some of the shows about the universe (maybe not specifically "The Universe" that you contribute to), they tend to fluff the science up a bit for general T.V. audiences.

AlexFilippenko117 karma

Yes, it's sensationalized to a greater or lesser degree, depending on the show. This is done to make the material more flashy, more exciting, and thus attract potential viewers. If someone is flipping channels once every 7 seconds, they are more likely to stop and watch an astronomy documentary if the show seems really interesting. To survive, these shows need a wide audience, not just people who are already interested in science.

AlexFilippenko112 karma

Thank you for all of the questions and please keep them coming! I am reading through now, and I apologize for the delay.

Brohio98 karma

How will we understand or detect dark matter/energy? Will this happen in the next 50 years?

AlexFilippenko64 karma

Physicists are trying to directly detect dark matter in terrestrial labs. I think dark matter will be found this way in the next 20 years -- and if not, we need to go back to the drawing board! Dark energy will be much more difficult to directly detect, so I'm not sure it will happen in the next 50 years. Without direct detections, a more complete understanding of both dark matter and dark energy will come from from detailed observations of how they affect the Universe. Other astrophysicists and I are busy collecting data that are setting ever more precise constraints on the physical nature of dark matter and dark energy.

baronvonbobbyhill91 karma

Your Astro C10 class - Intro To General Astronomy - is always one of the largest and most popular classes on campus (~600 students per semester). For a lot of people, it's as much science as they'll ever take, so it seems like a major goal of yours has been to instill a sense of appreciation and general undersatanding of how astrophysics is important to us. Do you think that same model should be used in other core scientific fields, to give people the kind of understanding that makes them informed voters/citizens without expecting that they devote their lives to a field before they encounter the big stuff?

AlexFilippenko68 karma

Yes, that's been my general philosophy in my 800-student Astronomy C10 course, and it has been very successful. I think it would work in many other introductory science courses as well. An example at UC Berkeley (my home institution) is Professor Richard Muller's "Physics for Future Presidents" and the associated book (which you can buy online). He teaches really interesting, relevant physics without focusing on standard technical problems (which most people think are pretty boring) found in physics courses for scientists.

aquosspectrum75 karma

What is it that makes you so happy? In every video I have seen of you, you are constantly smiling.

AlexFilippenko115 karma

I enjoy life and science, and educating people about science -- especially astronomy.

-MaJiC-69 karma

Where do you think we will be regarding space travel/research in 50 years? 100 years?

AlexFilippenko84 karma

Hard to say, that far in advance. I hope we will understand dark matter and dark energy. I hope definitive evidence for extraterrestrial life is found by that time. I'm almost certain we will have directly detected gravitational waves. Regarding space travel: Maybe within that time, people will land on Mars for the first time.

themanof3957 karma

I saw you mentioned education reform; what kind of reform do you think would help instill an actual love of knowledge in kids today? Do you think that our current system of just memorizing things and taking tests is sufficient? What do you think we can do instigate that change?

AlexFilippenko66 karma

Education reform is a very difficult issue. We have to excite kids about math and science at an early age. We might succeed in part by making these subjects more fun (check out http://www.piZone.org, for example).

We have to show kids how math and science are relevant to their lives, and how beautiful they are. Of course, some facts must be taught, but the process of science and discovery should be emphasized more.

MindExplosions54 karma

Does any money you make from the History channel allow you to buy/research scientific projects of your own that you have always wanted to try? P.S You're my favorite on the Universe!

AlexFilippenko116 karma

I'm glad you enjoy "The Universe" series and my contributions to it!

I don't make significant money from The Universe and the many other documentaries on which I appear, contrary to what many people may think. My travel expenses are covered, and occasionally I get a minimal honorarium for the time I've invested, but I don't get paid. I do it pro-bono, as a form of educational outreach. That being said, research is expensive, and I'm always very grateful for any financial donations to my research. Please contact me if you are interested in contributing.

huntus52 karma

What made you decide astrophysics as a career?

AlexFilippenko107 karma

I've always been fascinated by science. From ages 10 through 17, my main interest was chemistry, but as a freshman in high school I was given a small telescope. With it, I "discovered" Saturn -- the third "star" at which I pointed the telescope! This really jazzed me, and astronomy became a growing interest. In my freshman year of college, at the University of California at Santa Barbara, I took an introductory astronomy course from Professor Stanton J. Peale, and it was truly wonderful. I realized that the physics of the very large is governed by the physics of the very small (atoms and subatomic particles), so by switching to astrophysics I could "have it all." So I changed majors with the intention of becoming an astrophysicist, and I've never regretted the choice.

One final factor in my decision: As a budding young chemist, I played with explosives and had a couple of pretty bad accidents. I realized that I don't have the self-discipline to stay away from dangerous chemicals, so I should switch fields as an act of self-preservation, if nothing else!

themongoose8543 karma

What do you think about the odds of C/2013 A1 impacting Mars? Although it will most likely pass by Mars is there anything that Curiosity will be able to examine such as debris from the tail landing on the surface and if so what could this tell us?

AlexFilippenko43 karma

I don't think comet C/2013 A1 will collide with Mars. You can find more information, with occasional updates, at http://en.wikipedia.org/wiki/C/2013_A1 . So little debris is expected to hit Mars (especially since the comet's tail will be pointing away from Mars at the time of closest approach) that there's essentially no way for Curiosity to find it.

TheHistoryChannel38 karma

I don't remember approving of this...

..but before I speak with your higher-ups, how do you think we, as a country, are doing concerning the promotion of astrophysics, or even physics as a career in general?

I get a warm and fuzzy feeling inside every time I see a show like "The Universe" referenced out in the wild, but the ratio of Kardashian to Scientific references is still shockingly high.

It's a complicated problem, so I guess I'm asking you where you think its roots lie. Is it an early education problem? Or is it a culture problem? Or are they so related that you can't differentiate between the two?

Thanks so much for your contributions! And I'm so sorry about Ancient Aliens... Gotta pay the bills man...

AlexFilippenko20 karma

It's a complicated question. I'll give just a brief response right now. I think we need to put more focus on STEM education (science, technology, engineering, and mathematics) in primary school. Other countries are beginning to pass us up. I'm all for other countries doing well in such fields, but I'd like to see the United States remain in the top echelon as well. Things like "pi day" can help promote education in math and science by focusing on how fun and engaging these subjects are.

By the way, my wife's website http://www.piZone.org is a great place to go for a bunch of interesting facts about pi, games, videos, t-shirts, etc.

commandant_skip36 karma

My 14 year old son has been interested in a career in astrophysics since he was 7 years old. Any tips for him, education and extra-curricular programs wise?

AlexFilippenko52 karma

He should take as many math and science (especially physics) courses as possible in high school and science, but not neglect other studies as well -- as a scientist, one needs to be able to communicate effectively. He also might want to volunteer at a local planetarium or science center.

parmajohn32 karma

I recently read "A brief history of time" and my interest in the cosmos has been growing. Are there any books you could recommend?

AlexFilippenko53 karma

If you are interested in subjects like dark matter and dark energy, a good book is Richard Panek's "The 4 Percent Universe"

I coauthored this introductory text covering all of astronomy: "The Cosmos: Astronomy in the New Millennium" (3rd ed.), by Jay M. Pasachoff and Alex Filippenko. You can get it at http://www.cengage.com/us/ (Type Filippenko under "Search Products" and click on the "College Faculty" button.)

I produced a set of 12 half-hour video lectures on black holes: http://www.thegreatcourses.com/tgc/courses/course_detail.aspx?cid=1841 It is on sale now for just $40 (regular price: $200).

My 96-lecture video course on all of introductory astronomy can be found here: http://www.thegreatcourses.com/tgc/courses/course_detail.aspx?cid=1810 It isn't on sale now (regular price $800), but it will be sometime in the next month or two, typically for just $230.

retoupin28 karma

I have read recently that a new study suggests that life may not, in fact, be all that common in our universe, which makes life on earth even more precious. Are you involved in any projects that are searching for habitable planets? Also, do you believe that for humanity to truly insure its survival in the cosmos that expansion to other planets is necessary?

AlexFilippenko43 karma

I think primitive life (bacteria and microbes) may be pretty common, but that intelligence and mechanical ability at our level are very rare. We might be the only ones in our Milky Way Galaxy right now. I'm not involved in any exoplanet research. I do think that in order to help insure our long-term survival, we need to populate other planets; too many things can go wrong here on Earth, so we need to spread the seed.

SubliminalScream22 karma

You were my favorite Prof at Cal, and I was a Poli Sci major! I organized the bonfire rally the year you proclaimed Ursa Major as the official constellation of the University of California. Go Bears!

AlexFilippenko25 karma

Fabulous! Thanks for writing, and Go Bears!

KonradHarlan20 karma

If you could go to Mars on a one way trip would you?

AlexFilippenko34 karma

Perhaps only at the very end of my life. Otherwise, I wouldn't want to leave my family here on Earth or end my life prematurely.

Sobholz8820 karma

Hey Alex, what do you think about all of these exoplanets being discovered?

AlexFilippenko33 karma

It's totally fantastic! This is truly a "golden age" for research on exoplanets. In the past few years, the Kepler spacecraft has found a few thousand exoplanet candidates, more than 90% of which are probably genuine exoplanets. Studies of the "Doppler wobble" of the stars they orbit, and other observations, are gradually confirming more than more of them. Some are in, or near, the "Goldilocks zone" where liquid water might be found on the surface. Some are roughly the size of Earth. These will be excellent locations to search for life.

Salacious-19 karma

What is the most interesting fact or piece of trivia that you know about pi?

AlexFilippenko22 karma

Gosh, there are so many of them, it's hard to know what my absolute favorite is! See http://en.wikipedia.org/wiki/Pi for a bunch of interesting things about pi.

Some of my favorite things are expressions equivalent to pi. For example, in the 17th Century, John Wallis came up with the following product of an infinite number of terms:

2/pi = (1 x 1 x 3 x 3 x 5 x 5 x 7 x 7 …)/(2 x 2 x 4 x 4 x 6 x 6 x 8 x 8…)

Look at that! Products of pairs of odd numbers in the numerator, and products of pairs of even numbers in the denominator! That’s weird!

Also in the 17th Century, James Gregory discovered that

pi/4 = 1/1 – 1/3 + 1/5 – 1/7 + 1/9 – 1/11 + …

These are surprising and beautiful results, because they are completely arithmetic, yet pi first arose from geometry. But you need a LOT of terms to get an accurate value of pi: To get the first 5 digits of pi correctly, for example, you need 10,000 terms in Gregory’s series.

darthjon15 karma



AlexFilippenko23 karma

They might exist, but I don't think any have visited Earth.

tygreen13 karma

What is your favorite Pi joke?

This isn't really a joke but it's still a cool Pi observation: http://imgur.com/3AcAr1b

AlexFilippenko33 karma

It's probably the following one: "My PIN is the last 4 digits of pi" I have a t-shirt with this on it, and I probably get more comments about it from passers-by than for all my other t-shirts combined! You can get this t-shirt, and other pi-related t-shirts, at http://shop.pizone.org/ . Note that for every t-shirt sold, $3.14 is donated to provide a pi-related shirt for a teacher.

In general, the website piZone.org has lots of fun pi-related facts, games, activities, etc. -- I encourage you to visit it!

AlexFilippenko11 karma


pinkeye_uk13 karma

A warm welcome to Reddit =)

I referenced one of your papers (A LOW-MASS CENTRAL BLACK HOLE IN THE BULGELESS SEYFERT 1 GALAXY NGC 4395) in my research project for my 'thesis' at my undergraduate level. I was studying the link between nuclear star clusters and SMBH's using spectroscopy data from Hubble. I've seen your work in documentaries and in many published papers and I appreciate the way you can explain complex ideas very simply. It's been very helpful when I pursued and achieved my Astrophysics degree.

I'm currently a teacher in the Middle East where students at a middle and high school level have little to no motivation in the sciences. I'm a beginner science teacher looking to continue with my masters and PhD.

Now for the actual question:

Do you have any advice on how to get students interested in the sciences while fitting exciting activities within the strict boundaries of the American curriculum? (school is a US based system)

I want to do model rockets and things of that nature but it's very hard to get the school system on board with things like this (as well as model rocket engines being illegal here). I want to take the science beyond the textbook and into the physical realm.

Thank you for the AMA,

For anyone interested in the paper I was referring to:


AlexFilippenko3 karma

I'm glad you've enjoyed my presentations and publications, and found them to be useful. I have not taught in middle school or high school, so I don't have specific suggestions at this time, other than the kinds of things that seem to not be allowed where you teach. My main advice, in general, is to be really passionate about what you are teaching; be openly excited by the material, and explain to students why you are so interested in science. This will help get some of them excited as well. Point out the beauty of science, the logic behind it, and how it works -- all of their modern high-tech gizmos were developed through science!

omers10 karma

First, I have to say you're one of my favourite contributors to the various astronomy documentaries.

My question is, how much of the material you present is scripted by the producers/someone else and how much of it is your own words/analogies and do you write content for other presenters or contribute to their bits? Or worded differently, how much of the content do presenters contribute themselves versus presenting content written by others?

The reason I ask, the content of multi-presenter documentaries is always so consistent and I've always wondered if everything is pre-set or if the producers are just like "talk about tectonic activity on Mars. And go!"

AlexFilippenko11 karma

Thanks, I'm glad you enjoy my contributions to astronomy documentaries.

None of what I say is scripted -- I make up the words/sentences as I go along. Generally, I know roughly what kinds of questions will be asked, so I know roughly what I'm going to say. But I don't memorize my answers. I think that's generally the case for the other interviewees as well.

We tend to get interviewed for many hours, and each of us answers a ton of questions. What ends up being used by the producer is not up to us. But he/she has a lot of material with which to work, so they can pick and choose what they want. That's what probably leads to the seeming uniformity.

I sometimes suggest potentially helpful analogies that they might want to explore. Other times, they write to me with ideas, and I either suggest changes or agree to do it their way.

smurf4210 karma

What do you think is the most astounding fact about the universe?

AlexFilippenko30 karma

The Universe has the physical properties necessary for complexity to arise, culminating in life as we know it. If there's only a single universe, I find this to be inconceivable. So, in part because of such reasoning, I subscribe to the idea that ours is one universe in a multiverse whose constituent universes span a huge range of properties. Only rarely do universes have the right properties for complexity to arise, just as only rarely do planets have the right properties for life to arise.

BaronVonCrunch10 karma

Education is obviously important, but research on education is not even remotely definitive. Things that work in some places don't work on others, or only seem to work until we try to scale them up.

All we really know is that cultural expectations and family involvement are really, really important.

Given that those are not things that policy can address, how do we go about reforming education?

AlexFilippenko20 karma

It's a very tough problem. But certainly a greater emphasis on science and math education, and more resources, would be welcome. The greatest surge in science and technology in the US came after the Soviet Union successfully sent Yuri Gagarin into space on April 12, 1961; this was even more significant than their launch of Sputnik on October 4, 1957. President Kennedy then set our sights on landing Americans on the Moon, and the budget for science and technology went up a huge amount. People saw that there were well paid, interesting jobs in science and technology. A generation of kids was inspired by the Apollo landings. We have been the beneficiaries of the last half-century of exponential growth in technology, but now we are falling behind. Something needs to change.

middleageddude6 karma

Why has the discovery of the Higgs Boson and its values has seemingly shortened the life of the universe. Are we no longer headed for the "Big Rip"?

AlexFilippenko7 karma

I'm not sure what you mean. The discovery of the Higgs boson isn't relevant to the nature of dark energy, as far as I know. If dark energy remains repulsive but has a constant density throughout time, we are headed for the Big Chill (accelerating expansion). If the density of dark energy increases with time, so that eventually everything is torn apart, then that would be the Big Rip. (But the latter type of dark energy is very unlikely, in my opinion.) If the dark energy someday reverses sign (which it might, but we just don't know if it will), and if there's enough of it (again, we don't know), then the Universe might ultimately collapse into a Big Crunch (or Gnab Gib, which is Big Bang backwards!).

NoveltyAccount59285 karma

Hi Alex, thanks for doing this AMA! As someone who watches every astronomy and cosmology related documentary I can find, I always love it when you make an appearance -- your knowledge, love, and passion for the subjects is always obvious in your talks, and makes for a very engaging experience. I especially enjoyed your black holes lecture series, corny jokes and all.

Throughout history, we've been through numerous "Holy shit, we've been wrong all along!" periods, where our models and knowledge were turned on their heads. Most notably through the discoveries of Copernicus and Hubble did we discover that there's a lot more going on than we thought. My question is, do you think we've passed the point in collective human knowledge of earth-shattering discoveries? I understand that there's still a lot we don't know, and a lot of room left for major discoveries and giant leaps forward in our understanding, but is it likely that humanity will ever again experience another major upheaval in our models of the universe the likes of which Copernicus and Hubble resulted in?

AlexFilippenko11 karma

Thanks, I'm glad you enjoy my contributions to public education, as well as my corny jokes (which help lighten a complex subject). In case others are interested in my set of 12 half-hour video lectures on black holes, here's where to find it: http://www.thegreatcourses.com/tgc/courses/course_detail.aspx?cid=1841 It's on sale now for just $40 (regular price: $200).

Another set of video lectures ("Skywatching: Seeing and Understanding Cosmic Wonders") can be found here: http://www.thegreatcourses.com/tgc/courses/course_detail.aspx?cid=1852 It's not on sale right now, but I think it will be within a month or two, for just $60 instead of the usual $220.

Regarding you question of what remains to be discovered: In the past, there have been many times when we thought we know it all, but we were totally wrong. Though we know one heck of a lot now, I don't think the era of major breakthroughs is over. We don't yet know what dark matter and dark energy are, or if these are even the right framework. (I sometimes wake up screaming at night, worried that dark matter and dark energy might be the modern-day equivalents of Ptolemaic epicycles!) We don't yet have a unique, fully self-consistent theory of quantum gravity (that's what string theorists are working on, but we don't know if they are on the right track, and we certainly don't know which of many specific theories might be correct). We don't yet understand quantum entanglement at a deep level. These are just some examples.

ShepardRTC5 karma

What is your opinion of the reformulation of Einstein's Theory of Relativity by Julian Barbour and others to follow Mach's idea of true relativity, where objects are positioned only in relation to other objects?

AlexFilippenko26 karma

I don't know enough about this to comment intelligently.

CaesiaVulpes4 karma

What careers are there in mathematics and astronomy? I would love to pursue these fields in depth in school, but are the only careers just being a professor? How common are private astronomy research institutions?

AlexFilippenko7 karma

Most of the careers in math and astronomy research are at universities and some research institutions (e.g., Princeton's Institute for Advanced Study, or the Carnegie Institution for Science, or the National Optical Astronomy Observatory). However, with a good foundation in math, physics, and astronomy, you are very employable in other, more practical jobs. I've known several astrophysicists who were recruited by Wall Street, and many physicists who have had very satisfying careers in industry and the high-tech world.

ihatecats182 karma

Pssh, you haven't even officialy changed your name to Alex Fill-pi-enko.

Also, what is your 2nd favorite number?

AlexFilippenko4 karma

My name was accidentally spelled incorrectly by those who set up the Reddit AMA. It's Filippenko. My second favorite number is 42 (the answer to the question of Life, the Universe, and Everything). Possibly e. I like Sheldon Cooper's arguments for 73 (on the TV show, "The Big Bang Theory").

EternalWitness2 karma

Hello Alex! How do you think the newly confirmed discovery of the Higgs boson particle will affect our understanding of space? For example, will it affect how we view the formation of stars, galaxies, etc.? Thanks!

AlexFilippenko7 karma

The Higgs is a critical component of the Standard Model of particle physics, so the discovery is very important. But knowledge of the Higgs doesn't directly affect our understanding of the formation of stars and galaxies because these are macroscopic objects consisting of atoms and dark matter. The Higgs boson and the Higgs mechanism (for giving mass to particles) doesn't affect the interactions of these particles with each other, as long as they already exist.

nicasen1 karma

Hey Alex! More and more info is coming to light about scientific malfeasance in the medical sciences and pharmaceutical companies often struggle to replicate the findings from other papers. Has this also a major problem for the astrophysics community with groups such as NASA and the Jet Propulsion Laboratory?

AlexFilippenko3 karma

No, I don't think it has been a problem in astrophysics. One difference is that there aren't commercial products coming from our research, and we don't have the potential to get rich from them. Peer-reviewed research is subject to great scrutiny. If I were to intentionally publish something bogus but seemingly very important, others would rapidly figure things out and put me to shame. (If I made an honest mistake, that's a different story -- we're all human.) If I intentionally publish a bogus but unimportant result, it might not be noticed for a while because nobody cares -- but then what would be my point in deliberately publishing false claims?

larkable1 karma

Hi Alex! I watched your TTC Video "Understanding the Universe" lectures and enjoyed them immensely.

My question to you is:

What exactly led you to become an astrophysicist and what would you recommend to someone who was going into the astrophysics career?

AlexFilippenko4 karma

I have a deep desire to understand how the Universe and its contents work, as well as to know our fundamental origins. If you want to pursue astrophysics as a career, study math and physics a lot, but don't neglect courses in writing and clear communication either. Be prepared to put in very long hours for many years. It's definitely not for everyone, but it can be a very rewarding career for some.

JohnnyChurlish1 karma

What is the most awe-inspiring fact you know?

AlexFilippenko5 karma

"We are made of star stuff," as Carl Sagan used to say (but did not discover). The chemical elements (except hydrogen, helium, and a little bit of lithium) were produced long ago through nuclear reactions in stars, and explosions of some stars expelled these elements into interstellar space from which new stars, planets, and ultimately life formed. So the carbon in your atoms, the oxygen that you breathe, the calcium in your bones, and the iron in your red blood cells came from stars!