Wouldn't it seem reasonable to think that dark energy would be the majority of the mass-energy in our Universe? There is much more empty space than space which is occupied by mass. If dark energy turns out to be 'vacuum energy', that would appear to make sense.
@setiinstitute No new talks in a while, what's the deal? Your channel is one of the precious few reasons why what Newton Minnow said of television cannot quite be said of Youtube.
Oh, and by the way, how's your funding situation at the moment?
@polymath7 Hi Polymath, actually we've been posting talks every week - you can just check back in at youtube.com slash setiinstitute any time to see the latest talk that's been uploaded. Funding at SETI is challenging at the moment due to the GFC, but we're excited by some new opportunities that might come to fruition this year - stay tuned! If people are interested in following these things more closely, we'd suggest becomeing a TeamSETI member at the seti.org site.
Yes, I realized my mistake -to my delighted relief- immediately after posting that comment. Your funding difficulties upset me as much as you.
I recently read a perceptive article by Gregory Benford about how (in his judgment) certain onerous economic constraints -and ergo altruistic motives- must be assumed on the part of any civilization willing to broadcast a signal powerful enough to reach Earth for any sustained period of time. It's well worth reading if you've not done so.
I often run into folks on YT who think that DM & DE (always conflated) is a trumped up fix to the consensus model (CM) which indicates that it should be thrown out in favor of something new. In fact, the observational data for DM, from multiple, disparate sources and lines of reasoning, is now so strong that it is, in fact, an excellent example of a *prediction* made by the CM, which has proven correct. We've come a long way from Vera Rubin. But many people still seem to live in the early 90s.
@alivemo4 We know that MACHOs do exist. But it's pretty clear, at this point, that most of the matter is not in MACHOs. It's probably in WIMPs. And the CBR data from COBE and WMAP points to CDM rather than WDM or HDM. Although HDM (like neutrinos) no doubt has some small contribution.
@sbergman27 Somewhere between Einstein and the present, photons seem to have lost their mass, but I think they might be similar to WILPs. If so, some "dark matter" would actually be "light matter".
@alivemo4 As I've mentioned, photons have always been considered massless. That's nothing new since Einstein's time. It has been confirmed experimentally down to about a trillionth of a trillionth of a neutrino mass. The neutrino itself being almost massless. Meaning it's mass is around about a billionth of an electron mass. So even if we got a big surprise and the photon turned out have a mass at that upper limit, the sum total photon mass for the Universe would likely be measured micrograms.
@sbergman27 For the sum total photon mass for the Universe, are you including those that are currently traveling through space? And would all the photons now in intragalactic space ( thus currently "dark" ) be negligible with regards to the GRP?
@alivemo4 Although present in huge numbers, neutrino's are no longer in he running as major DM candidates since they are too light, and CBR data points to a CDM particle, rather than an HDM one like the neutrino (or a hypothetical photon with mass). Meanwhile, even speculating that the massless photon was not quite massless (unlikely) we know that even at the upper limit set by current experiment it can't be more than about a trillionth of the neutrino mass. Photons are just not candidates.
@alivemo4 Furthermore, we have *maps* of DM halos, created by doing detailed gravitational lensing of background light passing through their gravitational fields. We *know* where the DM is. And if (hypothetical massive) photons were causing the gravity field, those halos would be lit up like Las Vegas on a Saturday night. They aren't. That's why we know that DM can only be acting through gravitation, and *possibly* the nuclear Weak force (now that MACHOs are ruled out as major contributors).
@alivemo4 No. But I pay a great deal of attention to what the astrophysicists involved in the field are saying. And to where the research is directed. ESA's Planck data will hopefully improve our understanding of what detailed properties to expect the DM to have. And LHC *might* just find matching candidates. The as yet unconfirmed Supersymmetry particles predicted by the Quantum Standard Model are probably the front-runners, & would solve both particle and astro physical puzzles in one go.
@alivemo4 This YouTube playlist "The Atom So Far", is relevant to this topic. The part that directly pertains to Hot Dark Matter (fast moving) particles not being suitable DM candidates is in part 6. But the whole lecture is excellent, and definitely worth a watch:
@alivemo4 No! I didn't mean to scare you away! Science does not belong to "the pros". It belongs to all of us. I'm 47. Not old, but also not young. And I want to know, before I die, as much as I possibly can about just where I fit in to the Universe, Multiverse, whatever. That's Cosmology. We (the lucky folks who are currently living) only get one shot at this. And once you are dead you will never have another chance to ask any more questions. Partake while you are privileged to do so. :-)
@sbergman27 Well, it's unlikely that you'll discover where you fit into the scheme of things by watching lectures on particle physics. You'd be better off following God on Twitter. lol.
@alivemo4 To me, the question is not "why are we here?". That would be a "Follow God on Twitter" question, I agree. I would like to know as much as possible about how I, an inconsequential being on a tiny planet, in an easily forgettable area of an unremarkable galaxy, fit in, for maybe 80 years, into a Universe (or, as it is beginning to seem, a Multiverse) that looks like it will likely endure for more than a trillion trillion years. We, all of us, are incredibly privileged.
@sbergman27 If you put it that way ( "inconsequential being on a tiny planet, etc" ) maybe you should just be trying to have as much fun as possible, rather than racking your brains over dark matter!
@alivemo4 Seeking a deeper understanding of the Universe (or Multiverse) in which we live out our 80 or so yrs *is* fun. And rewarding in the most profound possible way. On my deathbed, I likely won't have any final answers. But neither will I feel regretful for not taking the time to try to understand. I guess most people are satisfied with the fairy tales in their religious texts and feel they don't need think any further. But that seems awfully shallow. Then again, lots of people are shallow.
@braneworld We have a couple of videos like this but the December videos will have much better audio. They start with Bart de Pontieu's great talk which will be posted in about 3 weeks.
@braneworld Agreed. Providing food/drink during a seminar is not a good idea. The content of the talk should be the reason people go, they can eat afterwards or before :/
It is probably just a matter of clipping a mic on the speaker and directly feeding that into the camera, instead of using the camera's microphone. I could be wrong though, I am not an A/V expert.
Excellent lecture and the technical side is the best I've seen yet. I really like how you have the slides shown with the presenter in a sidebar. Thanks for these great programs.
@setiinstitute Are you familiar the problem of how aggregate utility in consequentialist ethics (i.e., how to weigh a mild benefit for the many against a great benefit for the few)?
I'm sure you anticipate my analogy: though you reach a small audience, it is safe to say in most cases our individual gratiude is enormous.
The Discovery channel, conversely, make me itch to climb a clock tower with a rifle.
cool beans dude!
999JPETZ 1 month ago
Brilliant and fascinating lecture. Chung-Pei Ma is a great communicator. Bravo!
RobRoyal06 11 months ago
Wouldn't it seem reasonable to think that dark energy would be the majority of the mass-energy in our Universe? There is much more empty space than space which is occupied by mass. If dark energy turns out to be 'vacuum energy', that would appear to make sense.
washmlakid 1 year ago
Awesome lecture, thanks for uploading. SETIinstitute is my favorite subscription on youtube.
Also, glad that SETI@Home finally got back online, glad to be crunching WU's again.
dgumbrecht 1 year ago
@dgumbrecht Thanks - glad you're enjoying the Series!
setiinstitute 1 year ago
@setiinstitute No new talks in a while, what's the deal? Your channel is one of the precious few reasons why what Newton Minnow said of television cannot quite be said of Youtube.
Oh, and by the way, how's your funding situation at the moment?
polymath7 1 year ago
@polymath7 Hi Polymath, actually we've been posting talks every week - you can just check back in at youtube.com slash setiinstitute any time to see the latest talk that's been uploaded. Funding at SETI is challenging at the moment due to the GFC, but we're excited by some new opportunities that might come to fruition this year - stay tuned! If people are interested in following these things more closely, we'd suggest becomeing a TeamSETI member at the seti.org site.
setiinstitute 1 year ago
Yes, I realized my mistake -to my delighted relief- immediately after posting that comment. Your funding difficulties upset me as much as you.
I recently read a perceptive article by Gregory Benford about how (in his judgment) certain onerous economic constraints -and ergo altruistic motives- must be assumed on the part of any civilization willing to broadcast a signal powerful enough to reach Earth for any sustained period of time. It's well worth reading if you've not done so.
polymath7 1 year ago
@polymath7 Can you give us a link to the Benford article (you can't use slashes here, but put in 'slash' instead). Thanks for the support!
setiinstitute 1 year ago
I often run into folks on YT who think that DM & DE (always conflated) is a trumped up fix to the consensus model (CM) which indicates that it should be thrown out in favor of something new. In fact, the observational data for DM, from multiple, disparate sources and lines of reasoning, is now so strong that it is, in fact, an excellent example of a *prediction* made by the CM, which has proven correct. We've come a long way from Vera Rubin. But many people still seem to live in the early 90s.
sbergman27 1 year ago
Spectacular, awe-inspiring lecture !!!
sachibbsr 1 year ago
@sachibbsr Glad you liked it! Feel free to recommend it to friends!
setiinstitute 1 year ago
Dark matter might be like junk DNA. There's a lot of crap rock out there :)
alivemo4 1 year ago
@alivemo4 We know that MACHOs do exist. But it's pretty clear, at this point, that most of the matter is not in MACHOs. It's probably in WIMPs. And the CBR data from COBE and WMAP points to CDM rather than WDM or HDM. Although HDM (like neutrinos) no doubt has some small contribution.
sbergman27 1 year ago
@sbergman27 Somewhere between Einstein and the present, photons seem to have lost their mass, but I think they might be similar to WILPs. If so, some "dark matter" would actually be "light matter".
alivemo4 1 year ago
@alivemo4 As I've mentioned, photons have always been considered massless. That's nothing new since Einstein's time. It has been confirmed experimentally down to about a trillionth of a trillionth of a neutrino mass. The neutrino itself being almost massless. Meaning it's mass is around about a billionth of an electron mass. So even if we got a big surprise and the photon turned out have a mass at that upper limit, the sum total photon mass for the Universe would likely be measured micrograms.
sbergman27 1 year ago
@sbergman27 For the sum total photon mass for the Universe, are you including those that are currently traveling through space? And would all the photons now in intragalactic space ( thus currently "dark" ) be negligible with regards to the GRP?
alivemo4 1 year ago
@alivemo4 Although present in huge numbers, neutrino's are no longer in he running as major DM candidates since they are too light, and CBR data points to a CDM particle, rather than an HDM one like the neutrino (or a hypothetical photon with mass). Meanwhile, even speculating that the massless photon was not quite massless (unlikely) we know that even at the upper limit set by current experiment it can't be more than about a trillionth of the neutrino mass. Photons are just not candidates.
sbergman27 1 year ago
@alivemo4 Furthermore, we have *maps* of DM halos, created by doing detailed gravitational lensing of background light passing through their gravitational fields. We *know* where the DM is. And if (hypothetical massive) photons were causing the gravity field, those halos would be lit up like Las Vegas on a Saturday night. They aren't. That's why we know that DM can only be acting through gravitation, and *possibly* the nuclear Weak force (now that MACHOs are ruled out as major contributors).
sbergman27 1 year ago
@sbergman27 So you're an astrophysicist actively involved in this field then?
alivemo4 1 year ago
@alivemo4 No. But I pay a great deal of attention to what the astrophysicists involved in the field are saying. And to where the research is directed. ESA's Planck data will hopefully improve our understanding of what detailed properties to expect the DM to have. And LHC *might* just find matching candidates. The as yet unconfirmed Supersymmetry particles predicted by the Quantum Standard Model are probably the front-runners, & would solve both particle and astro physical puzzles in one go.
sbergman27 1 year ago
@alivemo4 This YouTube playlist "The Atom So Far", is relevant to this topic. The part that directly pertains to Hot Dark Matter (fast moving) particles not being suitable DM candidates is in part 6. But the whole lecture is excellent, and definitely worth a watch:
/watch?v=NHfAv7hHMk4&playnext=1&list=PLD18AEDA8CC25030A&index=1
sbergman27 1 year ago
@sbergman27 Thanks for that, but I think I'll let the pros figure it out. It's not like I'm getting paid to. lol.
alivemo4 1 year ago
@alivemo4 No! I didn't mean to scare you away! Science does not belong to "the pros". It belongs to all of us. I'm 47. Not old, but also not young. And I want to know, before I die, as much as I possibly can about just where I fit in to the Universe, Multiverse, whatever. That's Cosmology. We (the lucky folks who are currently living) only get one shot at this. And once you are dead you will never have another chance to ask any more questions. Partake while you are privileged to do so. :-)
sbergman27 1 year ago
@sbergman27 Well, it's unlikely that you'll discover where you fit into the scheme of things by watching lectures on particle physics. You'd be better off following God on Twitter. lol.
alivemo4 1 year ago
@alivemo4 To me, the question is not "why are we here?". That would be a "Follow God on Twitter" question, I agree. I would like to know as much as possible about how I, an inconsequential being on a tiny planet, in an easily forgettable area of an unremarkable galaxy, fit in, for maybe 80 years, into a Universe (or, as it is beginning to seem, a Multiverse) that looks like it will likely endure for more than a trillion trillion years. We, all of us, are incredibly privileged.
sbergman27 1 year ago
@sbergman27 If you put it that way ( "inconsequential being on a tiny planet, etc" ) maybe you should just be trying to have as much fun as possible, rather than racking your brains over dark matter!
alivemo4 1 year ago
@alivemo4 Seeking a deeper understanding of the Universe (or Multiverse) in which we live out our 80 or so yrs *is* fun. And rewarding in the most profound possible way. On my deathbed, I likely won't have any final answers. But neither will I feel regretful for not taking the time to try to understand. I guess most people are satisfied with the fairy tales in their religious texts and feel they don't need think any further. But that seems awfully shallow. Then again, lots of people are shallow.
sbergman27 1 year ago
great lecture but the crowd noise is really distracting.
braneworld 1 year ago
@braneworld We have a couple of videos like this but the December videos will have much better audio. They start with Bart de Pontieu's great talk which will be posted in about 3 weeks.
setiinstitute 1 year ago
@setiinstitute Thanks! I really appreciate the video series and the work you guys do.
braneworld 1 year ago
@setiinstitute Thanks - look forward to it, getting ready to watch Seth Shostak's new one now.
braneworld 1 year ago
@braneworld Agreed. Providing food/drink during a seminar is not a good idea. The content of the talk should be the reason people go, they can eat afterwards or before :/
shenorock 1 year ago
It is probably just a matter of clipping a mic on the speaker and directly feeding that into the camera, instead of using the camera's microphone. I could be wrong though, I am not an A/V expert.
braneworld 1 year ago
@braneworld Yes, that is the approach we've taken and you'll hear the improvement in the talk on the Sun by Bart de Pontieu in about 3 weeks time.
setiinstitute 1 year ago
@shenorock Hopefully our new audio setup will not force us to take those measures - thanks for the input though!
setiinstitute 1 year ago
Excellent lecture and the technical side is the best I've seen yet. I really like how you have the slides shown with the presenter in a sidebar. Thanks for these great programs.
Aiden057 1 year ago
God, I love this channel. I keep adding these talks to my 'favorites'.
polymath7 1 year ago
Dark Energy = Dark Mass x C x C
where C = Speed of Light
;-)
TonyUnplugged 1 year ago
Thank you very much for this great lesson. A splendid video and magnificent work.
TrueHamal 1 year ago
@TrueHamal Thanks Hamal, it's our pleasure to bring you these talks. Hope to see more of you in the future.
setiinstitute 1 year ago
@setiinstitute Are you familiar the problem of how aggregate utility in consequentialist ethics (i.e., how to weigh a mild benefit for the many against a great benefit for the few)?
I'm sure you anticipate my analogy: though you reach a small audience, it is safe to say in most cases our individual gratiude is enormous.
The Discovery channel, conversely, make me itch to climb a clock tower with a rifle.
polymath7 1 year ago
@polymath7 Thanks polymath, yes we aim to present a little more science than the Discovery channel ... think of us as a Discovery channel-antidote!
setiinstitute 1 year ago