Does Dark Matter BREAK Physics?

Tweet at us! @pbsspacetime
Email us! pbsspacetime [at] gmail [dot] com

SPACETIME IS BACK! And with this episode we welcome in Matt O’Dowd as the new host to rigorously take you through the mysteries of space, time, and the nature of reality. We’re starting off this new season with perhaps one of the most mysterious things of all — DARK MATTER. What is it? Where does it come from? And is it even real? Watch this episode of Space Time to find out!

----------------------------------------­---------

Comment Links

SafetySkull

Agen0000

----------------------------------------­---------

[calcaware]

Wow. Matt from 4 years ago looks like he stayed up all night and discovered something important. Now he has a more calm confidence. I think that is evidence he loves his job.

[gabeperez-giz]

See, guys? I told you -- the show is in good hands. Great first outing. Keep it up, new guy.

Sincerely,

The "other guy"

[pbsspacetime]

Hey guys, this is Matt. Also FIRST!!! (No seriously, this is my first episode.)

[BalasielVOD]

Over 7 years later, it's awesome to see your first episode again and realize how the show has evolved

[richardmasters]

Matt - watching you now 4 years later I now feel we’d be good friends if we ever should meet. Thanks for all your efforts to inspire everyone’s interest in the universe.

[hey.goldfish]

Matt, your AMA from 12/10/21 said to NOT watch your first video, so here I am, watching it (at least according to the complete playlist - so I apologize if it's not your first)! You always have been so easy to understand and you explain everything in a simpler way. Thank you for all of your time and effort you put into the videos. ❤️

[Theaumes]

Great first episode, Matt! Can't wait for more!

[Jobobn]

Two years later, and Matt is easily in my top 5 hosts for science videos. Seriously, man, you've got the perfect voice for delivering this material.

[MikeVDrumming]

I love coming back to older episodes and noticing drops in audio quality and lighting etc. and to see how far they've come. Mat is a brilliant teacher and i hope this channel never stops!

[joshuaolian]

“they’re basically compact, dead or failed stars. black holes, neutron stars, brown dwarf, Macaulay Culkin, etc.”
most underrated joke ever
😂😂

[zennstuff]

Excellent video.

One small point I would like to make, having lived through the time of this science and having been part of it. While the bullet cluster is an especially clean example of dark matter, it was not the first "direct" detection, and curiously the initial paper did not give the explanation here (which by the way, is the correct one.) But that is another topic really.

What people (mostly younger physicists) who tell this story get wrong is that there was an equally clean measurement back in the early 1980s. At that time, the work of Rubin and Ford, the work of Mort Roberts, the theoretical explanation of Einasto, Kaasik, and Saar (1974), and the size of tidal radii of our Galaxy's satellite systems pointed toward dark matter. The 1930s work of Zwicky, which broke open the field, was actually not compelling since the old value of the Hubble constant was used (500) and the unknown virial time of Coma was assumed. The work of Rubin, Ford, and Roberts was also questioned by astronomers who argued about "maximal disks" where lots of normal mass could be hidden (this has been ruled out now).

Then, in the early 1980s Marc Aaronson discovered that the velocity dispersion of stars in dwarf spheroidal galaxies were way too large to be accounted for by normal mater. Sandy Faber and collaborators slightly later showed that the dispersions in normal elliptical galaxies were also too large. The dSph galaxies were particularly easy to measure star by star. There was no way around this measurement of dark matter unless the velocities were increased by repeated passages of the satellite galaxy near our Galaxy. But in order to puff up these satellites, basically all of them would have to be on their last orbit before breakup, which was statistically silly.

The discovery by Aaronson, now long forgotten by people who tell the story of dark matter, showed that dark matter existed on a completely different scale than that of rotation curves or galaxy clusters. These galaxies are very simple - no gas and just a few hundreds of red giant stars to measure. This made, and still makes, it difficult for modified gravity models because there are other objects of the same size- the distant Palomar globular clusters - which do NOT show any dark matter. This discovery by Aaronson helped lead to the quick acceptance of dark matter and he deserves not to be forgotten as one of the pioneers in the field.

The tragedy here is that Marc died in a terrible accident at KPNO in 1987 while observing these same galaxies, and along with his death seems to have also gone the knowledge of his work by people who retell the story of dark matter by copying what others have said. To put it bluntly, he died while confirming his discovery, something that is tragic. He deserves to be better remembered.

[TheFishCostume]

These scientists are amazing at acronyms.

[MrUtak]

I really like the new host. How can you find two awesome hosts that are so knowledgeable in physics? This is amazing!

[Yumari-Mai]

Coming here to finally watch the complete dark matter & energy playlist after finding PBS space time a few months ago... and what treasure do I see! Matt's first ep.
So much energy and excitement ;D It's fun to compare the past presentation style with current, and of course, both are pleasant.
Thanks for putting out soo much educational content that will keep me busy for so long :)

[Jobobn]

2019 here, and I'm rewatching all of Matt's Space Time episodes for probably the third or fourth time. It's always funny to see him so animated in the earlier episodes and not using The Voice That Could End All War.

Seriously, his cadence in later episodes is the most relaxing thing ever.

[akari]

*_Obligatory Image of Einstein Sticking His Tongue out_*

[Epoch]

Good job, man. These are complex topics with very difficult answers and you did a good job of explaining these things. You have a hard act to follow as your predecessor was very adept at explaining these things.

I hope to see more videos about the universe and about physics that are at the very edge of our knowledge. People often seem to think that once an idea is developed it is set in stone and will never change, but this is not the case. Newton's Gravitational model was replaced by Einstein's and though it did not invalidate what Newton had said it did give us a much better understanding of the universe around us. I feel that we are most likely going to find a better model for the microscopic world than Quantum Mechanics, but this will only add to our understanding. I also feel that when we do finally discover what Dark Matter actually is, we will take a giant leap forward in our understanding of what it is we talk about when we discuss "matter".. Things at small scales get fuzzy and this is something that is inherent to the natural world and not a result of our inadequate equipment that we use to measure things.

I am amazed by how far we have come in so short a time in science. Things we have no right as human beings to discuss, such as the weight of an electron, have now become things we can accurately measure to many decimal places. As our equipment improves, so will our knowledge. I feel that in the not too distant future, the intelligent machines we are building will give us a significant advantage in tackling these remarkable questions about existence.

I think everyone who comes here has a thirst for knowledge and a better understanding of our place within Spacetime. We are lucky to live in an era where, while in the comfort of our home, we can find answers to the most profound questions.

[Waltham]

Dark Matter hold the Universe together.

Ergo, Dark Matter = Duct Tape.

Problem solved.

[altareggo]

I learned two things from this video: 1) Even though Einstein can't possibly be completely right, he always wins in the end, and 2) Space used to be orange.

[XiaosChannel]

first video of the new host!!!! cheers, you're totally nailing it!