Some times I wonder whether the effects we see can have a different interpretation, one we have not imagined yet. I know there attempts like modified gravity and stuff, but I mean completely different way of seeing things.
I just heard Sabine Hossenfelder’s weekly science news. She mentioned a new paper that seems to support MOND in a particular case. https://arxiv.org/abs/2210.13472
I thought I’d add (hopefully) a neutral comment or two. Since joining some ~3-4 months ago, and supporting the Origins project, this group, forum & especially Prof Krauss has enabled me to fit science back in to my busy life.... even though I’m doing science every day (industrial). It’s wonderful.
I particularly enjoy the curated selection in the “what I’m reading section”, as I don’t have the time myself to seek out such articles, and to get a curated selection of interesting subject matter is just great. I’d even love to have a “literature meeting” (just like in uni & my early days in industry) where articles are discussed....would be great, not just to read science, but to discuss science.
As you know, I’m obsessed with the inflationary epoch. I think it’s the most beautiful concept in cosmology, because it explains so much (solves the Horizon and Flatness problems, etc). I know beauty is not way to judge science…but it is so damn elegant.
As a non-cosmologist, I understand that inflation smoothed everything out and made it possible for what should have been “causally disconnected” photons can have the essentially the same temperature in the CMB.
Around 50-54 minutes, he does the calculations starting with GUT energies (10^16 GeV) and Chi the exponential expansion rate at 2.8 x 10^-38 seconds, Hubble length 8x10^-28 cm, mass density 2.3 X 10^81 g/cm^3, and he comes out with a universe that is between 1 and 10 cm large at the end of inflation.
Here’s my problem:
I cannot reconcile having the universe by Guth’s calculations at such a small size post-inflation with “space expanding faster than the speed of light” and smoothing out all matter that was ever to exist in the universe and allowing for the radiation to be the same temperature everywhere. 10 cm does not seem very far for “non-communication” between particles/radiation.
Also, I just bought Dan Hooper’s book “At The Edge of Time”. He writes on page 188: “During the epoch of inflation, space expanded at an absolutely staggering rate, tearing space and everything in it apart. No two objects, even elementary particles- remained close to one another for long enough to interact. Two objects separated by the width of an atom at the beginning of inflation were trillions of miles apart from one another by the time it was over- only a minuscule fraction of a second later. Inflation took regions of space that had been once been neighbors and forever disconnected them from each other. So utterly complete was this act of sequestration, that these regions became more than merely distant. Inflation left them in entirely difference universes.”
Now, as an amateur, that explanation of cosmic inflation is so much more mentally appealing to me to solve the aforementioned problems with standard Big Bang Cosmology, than hearing from Alan Guth, a brilliant man and THE father of inflation, that it was only 1-10 cm large at the end. I love that Hooper said “trillions of miles apart”.
What am I missing? Both explanations cannot be right. Is the nuance that Guth was talking about the patch of space that went on to comprise only the currently visible universe (90+ billion light-years wide currently), which may be a tiny fraction of the actual universe/multiverses?
I would appreciate it if you would elaborate on the following questions related to entropy and the expansion of the universe. I hope that my questions are worded properly and are significant for this chat.
1. Can you explain how the expansion of the universe be understood using entropy as per the second law of thermodynamics?
2. Is the process of expansion considered to be the positive (order) or negative (disorder) value of entropy?
3. What is considered the opposite value of the metric expansion (I assume that the velocity and increase of expansion is a preset mathematical formula) then the entopic opposite value must coincide somehow and be increasing in perfect symmetry with the rate of expansion.
4. How do we explain the increase in velocity in the expansion; is the expansion value getting stronger or is the opposite value getting weaker? (sorry not sure if this question makes sense without your answers 1-3)
5. When we refer to the entropic nature of the cosmos, can/how do we describe the state of “stability” between these two values?
My curiosity is on the dynamics of entropy but the variable of expansion may not "fit" in this discussion. Adiabatic is new for me - I will research it. What do you think of this statement: "Gravity is a "middleman", converting positive spatial entropy to positive temporal entropy, transferring the intrinsic motion of light to the intrinsic motion of time. In the process, gravity creates a metrically equilibrated spacetime, the joint dimensional conservation domain of light and matter." from John A. Gowan 21 Nov. 2001
Thank you for the 3 free 1 month gift subscriptions, Lawrence! I shared with three good friends who are all very smart doctors- and I have been telling them about you and your work- so hope they sign up and partake in the fun and learning.
Hello! I am not sure whether I will stay in this chat.
I feel uncomfortable with a trend I perceive towards more emphasis on male grievances in spite of the fact that every day in the news it is primarily women who are raped, harassed, stalked and killed by men; and men in authority sexually harassing student or subordinates (lots of scandals in the US universities). I know that men kill more men than women, but women do not kill men at the same rate.
Additionally, on the free speech issue, although I count myself as a free speech advocate, I do not consider a torrent of racist, misogynistic and otherwise bigoted social media comments directed at particular individuals as free speech. I would feel more comfortable in reading about male grievances and free speech issues as long as there is a recognition that unfortunately there is still an asymmetry about how much “freedom” there is in society and appropriate disclaimers are expressed as needed.
Here is an example: suppose that you (or somebody) are against affirmative action. You should still recognize that without affirmative action in the 70s and onward even highly qualified women and minorities were overlooked, if not discriminated against.I was there and saw it. It was in most cases benign neglect or unconscious bias, but it was there. With this disclaimer, then I feel it is fair to discuss affirmative action in the present.
Thanks Maria.. There are many asymmetries in free speech.. I am surprised you think that there is an emphasis on male grievances.. The point of the last article was that they simply shouldn't be ignored.. In any case, in the upcoming post you will learn of a woman who was removed from her tenured position for speaking out. Also no one is denying there weren't huge problems and disparities in the 60's and 70's, but this is 2022 and to ignore what has been done since is unfair. The situation was progressively worse as one goes back in time, not just for gender and race, but also religion, as when Jews were excluded from graduate schools in the 40's.. but that was long ago.
That’s what I want to hear. But it is not long ago, since some of the women who overcame obstacles in academia are now middle-aged. They were hired in the 80’s and 90’s, not 60’s and 70’s. I was indeed hired in the 70’s but remained the only woman in my department for many years, over a decade.
On the other hand, in 2022 you can be fired for having the wrong politics, the right politics being what the University Admin holds. The Regents of the U of Michigan are partisan and are elected on the partisan ticket. The U of Florida just appointed as President a Republican Senator! What kind of speech is “free” now depends on the politics of the institution.
Hello Dr. Strauss
I am wondering if you can try to explain to me what space really is. The "fabric" of spacetime.
It is all around us, but can we "see" it. Can we measure it. If gravity is bending it, shouldnt we be able to see it?
Space is streching because of dark energy, but what is streching.
Thank you
We detect space via the effects it has on objects we can see.. Space is literally a parameter that describes where events occur
Some times I wonder whether the effects we see can have a different interpretation, one we have not imagined yet. I know there attempts like modified gravity and stuff, but I mean completely different way of seeing things.
could always be... we won't know if we don't keep testing and observing.. :)
keeps us informed
I just heard Sabine Hossenfelder’s weekly science news. She mentioned a new paper that seems to support MOND in a particular case. https://arxiv.org/abs/2210.13472
I think she is biased.. I remain skeptical
I cannot evaluate
Amazing idea. A key ingredient to learn is the healthy exchange of ideas.
I thought I’d add (hopefully) a neutral comment or two. Since joining some ~3-4 months ago, and supporting the Origins project, this group, forum & especially Prof Krauss has enabled me to fit science back in to my busy life.... even though I’m doing science every day (industrial). It’s wonderful.
I particularly enjoy the curated selection in the “what I’m reading section”, as I don’t have the time myself to seek out such articles, and to get a curated selection of interesting subject matter is just great. I’d even love to have a “literature meeting” (just like in uni & my early days in industry) where articles are discussed....would be great, not just to read science, but to discuss science.
Thanks. That is an interesting idea.
Hi everyone - thank you Lawrence
Lawrence,
As you know, I’m obsessed with the inflationary epoch. I think it’s the most beautiful concept in cosmology, because it explains so much (solves the Horizon and Flatness problems, etc). I know beauty is not way to judge science…but it is so damn elegant.
As a non-cosmologist, I understand that inflation smoothed everything out and made it possible for what should have been “causally disconnected” photons can have the essentially the same temperature in the CMB.
I have watched Alan Guth’s lecture on Inflation at MIT at least 5 times. https://ocw.mit.edu/courses/8-286-the-early-universe-fall-2013/resources/lecture-23-inflation/
Around 50-54 minutes, he does the calculations starting with GUT energies (10^16 GeV) and Chi the exponential expansion rate at 2.8 x 10^-38 seconds, Hubble length 8x10^-28 cm, mass density 2.3 X 10^81 g/cm^3, and he comes out with a universe that is between 1 and 10 cm large at the end of inflation.
Here’s my problem:
I cannot reconcile having the universe by Guth’s calculations at such a small size post-inflation with “space expanding faster than the speed of light” and smoothing out all matter that was ever to exist in the universe and allowing for the radiation to be the same temperature everywhere. 10 cm does not seem very far for “non-communication” between particles/radiation.
Also, I just bought Dan Hooper’s book “At The Edge of Time”. He writes on page 188: “During the epoch of inflation, space expanded at an absolutely staggering rate, tearing space and everything in it apart. No two objects, even elementary particles- remained close to one another for long enough to interact. Two objects separated by the width of an atom at the beginning of inflation were trillions of miles apart from one another by the time it was over- only a minuscule fraction of a second later. Inflation took regions of space that had been once been neighbors and forever disconnected them from each other. So utterly complete was this act of sequestration, that these regions became more than merely distant. Inflation left them in entirely difference universes.”
Now, as an amateur, that explanation of cosmic inflation is so much more mentally appealing to me to solve the aforementioned problems with standard Big Bang Cosmology, than hearing from Alan Guth, a brilliant man and THE father of inflation, that it was only 1-10 cm large at the end. I love that Hooper said “trillions of miles apart”.
What am I missing? Both explanations cannot be right. Is the nuance that Guth was talking about the patch of space that went on to comprise only the currently visible universe (90+ billion light-years wide currently), which may be a tiny fraction of the actual universe/multiverses?
Thank you,
Steve
Dr. Krauss,
I would appreciate it if you would elaborate on the following questions related to entropy and the expansion of the universe. I hope that my questions are worded properly and are significant for this chat.
1. Can you explain how the expansion of the universe be understood using entropy as per the second law of thermodynamics?
2. Is the process of expansion considered to be the positive (order) or negative (disorder) value of entropy?
3. What is considered the opposite value of the metric expansion (I assume that the velocity and increase of expansion is a preset mathematical formula) then the entopic opposite value must coincide somehow and be increasing in perfect symmetry with the rate of expansion.
4. How do we explain the increase in velocity in the expansion; is the expansion value getting stronger or is the opposite value getting weaker? (sorry not sure if this question makes sense without your answers 1-3)
5. When we refer to the entropic nature of the cosmos, can/how do we describe the state of “stability” between these two values?
1. total entropy within coming volume remains constant to increases
2. sometimes expansion is adiabatic.. means entropy within volume remains constant.. sometimes it increases.
3. don't understand
4. Hubble constant is constant over time, which means expansion is accelerating.
5. don't understand
My curiosity is on the dynamics of entropy but the variable of expansion may not "fit" in this discussion. Adiabatic is new for me - I will research it. What do you think of this statement: "Gravity is a "middleman", converting positive spatial entropy to positive temporal entropy, transferring the intrinsic motion of light to the intrinsic motion of time. In the process, gravity creates a metrically equilibrated spacetime, the joint dimensional conservation domain of light and matter." from John A. Gowan 21 Nov. 2001
don't understand that sentence.. doesn't make sense to me.
Thank you for the 3 free 1 month gift subscriptions, Lawrence! I shared with three good friends who are all very smart doctors- and I have been telling them about you and your work- so hope they sign up and partake in the fun and learning.
thanks so much.. That is wonderfully kind of you!
I shared also with fellow scientists and have persuaded two to come to the evening events in Phoenix in 10 days or so.
Yay! Thanks.
How do I get on the subscriber chat on my laptop?
I don’t know if you need the app or whether you can use the chat on a browser.
Hello! I am not sure whether I will stay in this chat.
I feel uncomfortable with a trend I perceive towards more emphasis on male grievances in spite of the fact that every day in the news it is primarily women who are raped, harassed, stalked and killed by men; and men in authority sexually harassing student or subordinates (lots of scandals in the US universities). I know that men kill more men than women, but women do not kill men at the same rate.
Additionally, on the free speech issue, although I count myself as a free speech advocate, I do not consider a torrent of racist, misogynistic and otherwise bigoted social media comments directed at particular individuals as free speech. I would feel more comfortable in reading about male grievances and free speech issues as long as there is a recognition that unfortunately there is still an asymmetry about how much “freedom” there is in society and appropriate disclaimers are expressed as needed.
Here is an example: suppose that you (or somebody) are against affirmative action. You should still recognize that without affirmative action in the 70s and onward even highly qualified women and minorities were overlooked, if not discriminated against.I was there and saw it. It was in most cases benign neglect or unconscious bias, but it was there. With this disclaimer, then I feel it is fair to discuss affirmative action in the present.
Thanks Maria.. There are many asymmetries in free speech.. I am surprised you think that there is an emphasis on male grievances.. The point of the last article was that they simply shouldn't be ignored.. In any case, in the upcoming post you will learn of a woman who was removed from her tenured position for speaking out. Also no one is denying there weren't huge problems and disparities in the 60's and 70's, but this is 2022 and to ignore what has been done since is unfair. The situation was progressively worse as one goes back in time, not just for gender and race, but also religion, as when Jews were excluded from graduate schools in the 40's.. but that was long ago.
That’s what I want to hear. But it is not long ago, since some of the women who overcame obstacles in academia are now middle-aged. They were hired in the 80’s and 90’s, not 60’s and 70’s. I was indeed hired in the 70’s but remained the only woman in my department for many years, over a decade.
On the other hand, in 2022 you can be fired for having the wrong politics, the right politics being what the University Admin holds. The Regents of the U of Michigan are partisan and are elected on the partisan ticket. The U of Florida just appointed as President a Republican Senator! What kind of speech is “free” now depends on the politics of the institution.
agreed..