Q&A - The Dark Universe - with Adam Riess

[@rationalmartian]

Some really great questions. But much more impressive is the answers. This has to be the most and best explained Q and A on these subjects, certainly that I've seen in a long time. All three do some simply superb analogies, break downs and explanations. Brilliant.

[@CaptianKeyz]

+rationalmartian I think everyone should take a look at this lecture. It really gets into the nuts & bolts of the science, as far as what we observe & can predict with models. Too many people think its all bull-shit, because they just have no clue about the science. Some of us like to think hard about big questions.

[@symmetrie_bruch]

i gree with the exception of the red haired lady her analogies are terrible imo for example the thriller album thing how someone in deli could know that. pretty obscure and nonsesical when you consider that what she wanted to say was simply: the temperature in the cmb is very uniform. what does this have to do with you favourite album? i think she leads the listener astray in many ways throughout the talk and makes it very easy to completely misunderstand what she´s trying to convey.

[@eskileriksson4457]

Brilliant Q&A. The original lecture is of course needed to understand it, but this was so much better.

[@lineikatabs]

Renée Hlozek is an amazing public speaker! I would love to read/listen more from her! Please invite her over more. Also, Risa Wechsler, fantastic scientist and good speaker as well, but she should really learn how to use a microphone. My ears are in pain.

[@cristianvargas7112]

+Ivo Temelkov So true, Renee presentation was awesome. I fell in love with her

[@sumotherdude]

this is freaking amazing. can't believe i just found this channel but glad i did!

[@TheRoyalInstitution]

Welcome! Glad to have you on board :)

[@slayerx3197]

Right??? I just search "RI Institute" and you can't go wrong! Been listening to these lectures every day since I found them

[@RayVRoberts]

Can you invite this group back for an update? This talk is 3 years old and advancements since then have been amazing...

[@jomen112]

I like it that Adam Riess points out at 27:30 to 29:40 that the "fine tuned" universe and multiverse etc are not scientific statement, but philosophical speculations. I wished this was more recognized when people argue about these things, because you often hear the claim "its been proven" or "must be so" according to science, which is utter scientific nonsense since we have no evidence to support it, nor evidence to rule out other possible explanations.

[@S....]

jomen112 We do have a lot of theories with mathematic equations which proves at least that it is possible. So it is much more then just a philosophical speculations.

[@TaylorWJ]

The Q&As add to the enjoyment of the main lecture. Thanks

[@gustavomoretto6449]

Fantastic job both by the audience's questions and by the clear and illuminating answers. If chance plays a role in the universe, this encounter ranks among the special ones.

[@sanjchiro]

All this talk only tells me that the nature of DM is so completely weird that not only is the idea that it consists of 'particles' probably way off but that ALL of our 'best ideas' are probably only barely touching on what DM is/isn't. It's like trying to measure 'consciuosness' or 'life' is...we really have no good ideas anymore

[@speider]

physicists dont believe in particles, really. you should find lectures on quantum field theory

[@En-of5oh]

32:27 of course, excellent answer that gives new meaning

[@jackpi1863]

Clear answers by all.

[@vicachcoup]

23:00 great question. The answers were striking in their lack of considering an intelligent creator. This shows the huge bias of many scientists. There is no supporting evidence for the multiverse but it is interesting to see how keen scientists are to reach for this as an answer.

[@PongoXBongo]

To sort of put the gravitational lensing of the CMB into the arrow analogy, it would be the wind blowing the arrow slightly off to the side. If you know the wind conditions at the time the arrow was loosed, then you should be able to more accurately predict where precisely the archer was positioned. Modern soldiers do this to locate distant snipers, for example.

[@jk0000079]

Well, if everyone is so keen on everything being (more or less) symmetric, and they agreed, that you have particles, which have a non-0 mass, and gravitons causing those particles to attract each other, with a weak force (gravity), why not consider having an another weak force, which causes parts of the space having 0 mass, to repell each other?

[@ozdergekko]

One of the multiverse theories says that new universes might spawn within our own universe. If this were reality, a) would it have any influence on our universe (such as causing expansion/inflation, dark energy and so on), and b) would it effect the path of light?

[@Dyslexic-Artist-Theory-on-Time]

“We think it’s a particle” LOL

[@crazieeez]

Matter (visible and dark matter) stay constant throughout the history of the universe. Dark energy increases. So the early universe, matter (visible and dark matter) made up to 99.999999% of the universe and dark energy made up to 0.0000000001% until recently, it is 72% dark energy and 28% matter.

[@erikziak1249]

What exactly is the difference between the big rip and heat death? Are they not basically the same event, just interpreted from a different viewpoint? I find it really hard to write down my thoughts, but I have a complex picture of similarities, but maybe I am just wrong.

[@erikziak1249]

+BNM Very well written. If everything accelerates wildly from everything else, there is also no ability left to do work. I wonder now, does the expansion take som energy of the system? I mean, converted into "space"? If everything expands so rapidly that particles will not have the possibility to interact with each other, then entropy reaches also a maximum. There will be no ordered state, there will not be even a measurement possible, over larger structures.

[@jomen112]

In thermodynamics entropy is a measurement of the possible microscopic configurations the system can have. From the point of view I under stand things; the seemingly contradiction is that entropy can be said to decrease as the universe continue to expands since the possible "microscopic configurations" will decrease if things has less ways to interact with each other. Another ways to say this is that the information content of the universe would decreases, i.e. everything will progressively start to look the same no matter where you look (ultimately you will see nothing anywhere - the ultimate "sameness" will occur - since even the fundamental particles will be ripped apart into photons which in turn will be red shifted into nothing as the universe continues to expand). This mean the big rip is a kind of heat death as well, in the sense that you cannot perform anymore work. Therefore, your original intuition of them both ending up in heat death is in some sense somewhat correct, but the details in how it ends this way is different (on ends up as 'nothing' the other end up as 'heat dead'). _"If everything accelerates wildly from everything else, there is also no ability left to do work"_ Not entirely correct, expansion itself is a form of work performed. But the laws of thermodynamics also states when you perform work you consume energy available for doing work. So one might ask where does this, seemingly endless, energy available to do work comes from? As far as I understand, and I may be wrong on this point, it is created by creating "more" gravitational energy, or rather creating more of "less" gravitational energy since gravity is seen as a negative energy. In other words it is a zero sum game where work is done by creating energy from "nothing", and summed up to nothing, to drive the expansion, i.e. causing things to flies apart instead of gobble together, with the ultimate end of making everything that exists to vanish into nothing again (i.e. causing the big rip in where we came from nothing and ends in nothing, that is I imagine the "purpose" of the big rip is to nullify the energy from things like matter and photons created in the big bang. To paraphrase the uncertainty principles; you can have something from nothing, but only for a while). So to your question whether the expansion takes some energy; as I understand, and just described it, yes it does but it is balanced to zero by the addition of negative gravitational energy. Again I may be wrong on this point. You also wondered if this energy is converted into space. As I understand it, the expansion was that which been tried to be explain in the first place by dark energy, wasn't it - or was it a consequence of it? I cant tell, I probably miss out on something here, but so far ignorance has never prevented anyone from saying something stupid, so I guess it is fair play by me to say yes to that. But since I have no idea what spacetime is made of, I cannot say. As far it concern what I know (not much) I myself wonder, in my own blissful ignorance, if dark energy not only can creates spacetime but can be said to _be_ spacetime?

[@RakidulAlam]

RI Renee Hlozek should be invited in RI for one more time.

[@symmetrie_bruch]

the first question about the cmb and how to distinguish it from the rest that´s supposed to be such a great question didn´t get a good answer. isn´t it quite simply because cmb radiation is much more red shifted than the rest? so it should be very easy to filter it out from the rest

[@jomen112]

As supposed to be red shifted more from what? As she she said, stuff in the universe such as stars and dusts is assumed to emits radiation with a different spectrum than the spectrum of the cosmic background radiation and, as she further explained, the problem is to identify the signature of these spectrum, not to filter them. So yea, you seams to be correct, filtering is no big deal since this is well known math/physics... the real problem is to decide what and what not to filter.

[@fari66tube1]

Are you sure that univers is expanding ? The farther away galaxy is the greater it's redshift, so the faster moving away. But the farther away you looking the more back in time you are seeing ... and the closer to the presence time you looking the lower redshift. Then the results showes expansion of the universe is decreasing as the time passes toward the presence and in the future! Just a simple logic !!

[@abufaisal1st]

Great😘

[@theDuffChimp]

Universe is expanding, how fast, at what rate? At what point does the speed of light come into play? Dark energy couldn't possibly overcome the speed of light?

[@rationalmartian]

+theDuffChimp It all depends. When and where. The further something is away from us the faster it is receding away from us. And the further back we are observing in time. If one is observing something 1 Billion light years distant, one is observing it as it was 1 billion years ago. There is only us to measure from, because we are measuring everything relative to us. Everything is relative, there is NO preferred frame of reference. The speed of light doesn't figure in this in that way. The space can expand faster than the speed of light. There is no such limitation on the space itself.

[@SoYFooD2]

+theDuffChimp if the universe start of at a big enuf size than some light will never catch up to us because we are expanding away faster then the speed of light and it will also red shift to 0.

[@theDuffChimp]

+rationalmartian First of all, spacetime is intimately connected to matter and energy in the universe. Just saying the speed of light doesn't figure in our frames of reference isn't a satisfactory way to magically allow space to travel faster than light. c is absolute, nothing can alter it without significantly altering everything connected to it, which is almost everything in the universe. Constants are constant for good reason. There may some glitch or reason for space appearing to expand faster than c but it never actually could. It is a common assumption that space is expanding at a finite rate, in order for it to exceed light speed it would have to expend infinite energy in doing so. Pretty sure they said dark energy accounted for 70% of known energy/matter in the universe and not infinity.

[@SoYFooD2]

c is the absolute for traveling thru space. but if u add more space everyware then everything seemt to be moving away wail every one sees themselves standing still.(einsteins reletivatie). Imagen u are in a boat en u jell to some one on the coast. u can communicate at the speed of sound. but if the sea is stretch en more water appears the coast will look to move away from u. wile on the coast they see u move away. if this increase of distends is faster than the speed of sound u can never ever hear what he is telling u, end as time go by the sound will lag more en more to the super sonic expansion rate u are moving away at. but because the land en the boat are standing still this is unintuitive but apparently tru

[@theDuffChimp]

o......................k...

[@abumasroorahmed4203]

After 5 years : GOOGLE RECOMMENDATION

[@jomen112]

Interesting that these discoveries might "force" a unification of physics. Can't help getting the feeling that physics today is in a similar situation as it was in 100 year back, i.e. trying to explain things that does not really fit within the current framework, which in turn would lead to a breakthrough in our understanding of nature and - more important - faster gaming computers and cheaper pizzas.

[@piccolonijel]

I love science, but I want to know the girl who asked the first question either

[@WayneJohnsonZastil]

I can see dark matter and energy. Just most humans are not clever enough!

[@CJ-jc4nt]

Renée Hlozek voice

[@leoclub626]

Risa Wechsle's voice and persona is similar to Bill Gates'. Just an observation.

[@3enjoy3]

Dr Renée Hlozek - wow you really didn't need the microphone did you? My ears!!!!! Lol!

[@misterkefir]

Jeeeeesus Christ! Risa's Wechsler super high pitched voice makes this lecture almost unenjoyable for me.. I have nothing against her, but her voice is just piercing my ears like a mother***r! Ouch!