# Cosmos: A Waste of Spacetime **URL:** \ **Category:** The BBQ Pit\ **Created:** [March 10, 2014, 3:06am UTC](https://boards.straightdope.com/t/cosmos-a-waste-of-spacetime/683324 "2014-03-10T03:06:41Z")\ **Posts on this page:** 12\ **Page:** 12
**Author:** ![Asympotically\_fat](https://avatars.discourse-cdn.com/v4/letter/a/e47c2d/32.png) [@Asympotically\_fat](https://boards.straightdope.com/u/Asympotically_fat)\ **Post date:** [March 21, 2014, 8:46pm UTC](https://boards.straightdope.com/t/cosmos-a-waste-of-spacetime/683324/221 "2014-03-21T20:46:23Z")
> [@klaas](#): > > Dear Asympotically fat, thanks for your reaction! We agree on the Hubble radius as the point where objects gain the recession speed of light. Beyond the sphere with that virtual radius objects move faster away from us than the speed of light. So how could you reason objects are constantly entering? That radius is only defined by the Hubble constant H0 which was measured long ago already to be about 70. Previous year the most accurate value ever was measured to be 67.80 km/sec/Mpc. That value determines at which distance from earth the recession speed is equal to C. So far it is very difficult to decide if that value is going down over time because of less accurate measurements in the past. If it would go down (expansion rate going down) the radius would increase. At H0= 70 the radius is 4283, at 67.80 it’s 4422, at 65 it’s 4612 Mpc. When distances among all objects increase and that radius stays what it is now, we “loose” the sight on galaxies from earth in the very long run. It can be very confusing, but as I said comoving objects (for our purpose we may as well call comoving objects galaxies because galaxies generally speaking are very close to comoving) are constantly entering the particle horizon. Indeed they will always be in any model with a particle horizon for so long as the particle horizon exists because our particle horizon travels away from us at the maximum speed anything can travel away from us at, so any object not travelling away from us at the maximum possible speed will be overtaken by it. However the Hubble sphere is not the same thing as the particle horizon and it can be bigger or smaller than the particle horizon, depending on the model. In fact the significance of the Hubble sphere is not all obvious, though are two examples when it coincides with actual horizons: 1) in a radiation-dominated Einstein-de Sitter Universe where it coincides with the particle horizon and 2) in de Sitter space, where it coincides with the cosmic event horizon. Neither of those models could describe our Universe though (the first one lacks ‘matter’ and the second one lacks matter and radiation). > [@](#): > > Please check my calculation example in which I use 4 moments: > Given: redshift measurement, due to recession speed only, = 1 > T1 = 8.65 billion years before now – the photons which will be measured later, leave object – distance object earth is 2653 Mpc – recession speed object compared to earth is 0.60C > T2 = now (redshift measurement) – distance 4021 Mpc – speed 0.91C > T3 = 1.98 billion years from now – the last photons ever able to arrive earth leave the object – distance 4422 Mpc – speed 1C > T4 = 16.4 billion years from now – distance 8843 Mpc – speed 2C – the last photons from the object arrive on earth Not entirely sure what you’re trying to show here or what your calculations are based on. > [@](#): > > About the big bang: If there would have been a big bang, then looking in the direction of the centre of the explosion, one would see much less mass density (mass per cubic km) and in the direction away from the centre the mass density would decrease with the squared value of the distance. Both are NOT the case. The mass distribution in the visible universe is equal everywhere, in all directions, at least in our visible sphere. Besides as we all know, according to many many redshift values, all objects are moving away from each other with the same speed, except of course if an object has a speed of its own. That speed increases with distance, if watched from one point like the earth. This makes the example of the balloon with dots a nonsense story. The universe has NO centre. At the visible horizon exactly the same will be seen. On infinite distances from earth it probably will be the same story. Why would it be different at places very far away? For me this is an indication the universe must be infinite, though it can’t be proved. > But as I am an amateur I would like to read your reaction if you find the time. Greetings! This is a fundamental misunderstanding of big bang theory. The big bang is everywhere, so there is no centre. I don’t know why we would even be discussing particle horizons if we weren’t talking about the big bang theory. The existence of a particle horizon depends on the (conformal) age of the Universe being finite. ---
**Author:** ![leftfield6](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leftfield6/32/18780_2.png) [@leftfield6](https://boards.straightdope.com/u/leftfield6)\ **Post date:** [March 23, 2014, 12:07am UTC](https://boards.straightdope.com/t/cosmos-a-waste-of-spacetime/683324/222 "2014-03-23T00:07:27Z")
> [@DragonAsh](#): > > My kids are too young to understand what’s going on, but after watching the show, my 4yr old grabbed my hand and pulled me outside, and we stood out there for almost an hour, looking at the night sky. I’d call that a win. For the rest of this thread, whenever somebody basically says this show is shit, someone please quote this and tell them to STFU. DragonAsh, kudos on the 4 year old. You did something right. A WIN indeed. ---
**Author:** ![GIGObuster](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gigobuster/32/421_2.png) [@GIGObuster](https://boards.straightdope.com/u/GIGObuster)\ **Post date:** [March 23, 2014, 2:15am UTC](https://boards.straightdope.com/t/cosmos-a-waste-of-spacetime/683324/223 "2014-03-23T02:15:34Z")
Another WIN IMHO: The creationists are upset, the poor things are complaining that they are not getting equal time in the show. [http://www.rightwingwatch.org/content/creationists-demand-airtime-cosmos-sake-balance](http://www.rightwingwatch.org/content/creationists-demand-airtime-cosmos-sake-balance) > [@](#): > > Danny Faulkner of Answers In Genesis and the Creation Museum appeared on The Janet Mefferd Show yesterday to criticize Cosmos for not providing airtime for Creationism adherents. When Mefferd asked if Cosmos will “ever give a Creationist any time,” Faulkner responded by lamenting that “Creationists aren’t even on the radar screen for them, they wouldn’t even consider us plausible at all.” > [@](#): > > Arguing that evolution, the foundation of modern biology, and one of many theological beliefs on human creation are simply “two sides” that merit competing time on a science program is much like the equally absurd argument Creationists use when trying to undermine the teaching of evolution in public schools. ---
**Author:** ![Mr.Miskatonic](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mr.miskatonic/32/310_2.png) [@Mr.Miskatonic](https://boards.straightdope.com/u/Mr.Miskatonic)\ **Post date:** [March 23, 2014, 11:47am UTC](https://boards.straightdope.com/t/cosmos-a-waste-of-spacetime/683324/224 "2014-03-23T11:47:53Z")
> [@GIGObuster](#): > > Another WIN IMHO: > > The creationists are upset, the poor things are complaining that they are not getting equal time in the show. > > [Creationists Demand Airtime On 'Cosmos' For The Sake Of Balance | People For](http://www.rightwingwatch.org/content/creationists-demand-airtime-cosmos-sake-balance) I think Electricity is a fib and demand equal time on the television to explain my side of the story! What? ---
**Author:** ![cmyk](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cmyk/32/3353_2.png) [@cmyk](https://boards.straightdope.com/u/cmyk)\ **Post date:** [March 25, 2014, 4:46am UTC](https://boards.straightdope.com/t/cosmos-a-waste-of-spacetime/683324/225 "2014-03-25T04:46:05Z")
**THINK GEEK:** I’d pay top dollar for a 72-points of dexterity of a 1/12 Scale model of Neil deGrasse Tyson enshrouded in his half-mirrored, Bobba-Fettesque Cosmoship of Wonder™. Top Dollar. Especially if it makes a ponderous _swhooooossshhhh…_ noise. ---
**Author:** ![SlackerInc](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/slackerinc/32/275_2.png) [@SlackerInc](https://boards.straightdope.com/u/SlackerInc)\ **Post date:** [March 25, 2014, 7:41am UTC](https://boards.straightdope.com/t/cosmos-a-waste-of-spacetime/683324/226 "2014-03-25T07:41:14Z")
> [@Moe](#): > > I liked it a lot and I’m very glad it’s being done. Okay, wow…it took until post 30 to get to someone who is on my wavelength. Tough crowd! Really glad to read this one though. (Who knows, maybe the tide turned later in the thread and people will read this and be like “oh, that’s right, a lot of negativity on the first page”.) I guess the rest of your post is a little more negative than me though. > [@](#): > > There’s no getting around the comparison to Sagan, and on that front, it’s just lacking. Seriously lacking. It’s a very good science documentary and it feels that way, but somehow Sagan’s had this incredible sense of depth and contemplation. I love Carl Sagan and am glad that some of his most [profound soliloquoys](https://www.youtube.com/watch?v=p_naQhynOg0) have found a new life [on YouTube.](https://www.youtube.com/watch?v=e8P1Y1a7-L4) I just don’t expect anyone to be able to replace Sagan, although I am glad his widow Ann Druyan is the first named executive producer in the credits. I have seen just the first episode so far, but have watched that twice with each of my oldest two kids. Both times I wept profusely through the elegy (and torch passing) of the concluding few minutes. I personally liked the way the scale kept expanding out, until we were at the scale that groups of galaxies (if I have it right) are what is representing basically pixels or “motes of dust”. Freaky to see that at that huge scale, there was a visible pattern to the structure, like osteoporosis or something. And my mind was totally blown by the zoom out to where our entire universe is just a bubble in an infinitely large multiverse. Anyone notice the subtle optimism in saying we can’t see back to what happened before the Big Bang, “yet”? Even if we ever can, isn’t it basically that the “Big Bang” really wasn’t so big but rather a little local pop of a continuous effervescence of bubbles? Looked at that way, aren’t we already \*living \*in the microverse? (Whoa, man, far out…but yeah, I think it’s cool that Sagan smoked a lot of dope and theorised on its effects in terms of left vs. right hemisphere of the brain.) I also thought it was cool that he was willing to just state flat out that the origin of life is one of science’s great unanswered questions, without being defensive about it. Religions try to attack on points like that as a weakness, but it is in fact a strength (imagine a major religion being secure enough to admit they don’t know something, especially the answer to a major metaphysical question). ---
**Author:** ![DragonAsh](https://avatars.discourse-cdn.com/v4/letter/d/db5fbb/32.png) [@DragonAsh](https://boards.straightdope.com/u/DragonAsh)\ **Post date:** [March 25, 2014, 10:47am UTC](https://boards.straightdope.com/t/cosmos-a-waste-of-spacetime/683324/227 "2014-03-25T10:47:06Z")
> [@SlackerInc](#): > > I love Carl Sagan and am glad that some of his most [profound soliloquoys](https://www.youtube.com/watch?v=p_naQhynOg0) have found a new life [on YouTube.](https://www.youtube.com/watch?v=e8P1Y1a7-L4) Dear god how did I miss these? [You are here: Carl Sagan on the pale blue dot](http://youtu.be/p9TIeuBF9Ss). If you can watch this and not be moved to weep at the beauty and cruelty we see everyday on that pale blue dot, you’re probably already dead. ---
**Author:** ![Lobot](https://avatars.discourse-cdn.com/v4/letter/l/ce7236/32.png) [@Lobot](https://boards.straightdope.com/u/Lobot)\ **Post date:** [March 25, 2014, 10:52am UTC](https://boards.straightdope.com/t/cosmos-a-waste-of-spacetime/683324/228 "2014-03-25T10:52:44Z")
The audiobook of _Pale Blue Dot_ is entirely worth tracking down, FWIW. ---
**Author:** ![SlackerInc](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/slackerinc/32/275_2.png) [@SlackerInc](https://boards.straightdope.com/u/SlackerInc)\ **Post date:** [March 25, 2014, 9:32pm UTC](https://boards.straightdope.com/t/cosmos-a-waste-of-spacetime/683324/229 "2014-03-25T21:32:39Z")
**Lobot** and **Dragon Ash** : if the SDMB had a “Like” button, I would enthusiastically click it for those two posts! 🙂 ---
**Author:** ![klaas](https://avatars.discourse-cdn.com/v4/letter/k/ecc23a/32.png) [@klaas](https://boards.straightdope.com/u/klaas)\ **Post date:** [March 25, 2014, 9:42pm UTC](https://boards.straightdope.com/t/cosmos-a-waste-of-spacetime/683324/230 "2014-03-25T21:42:36Z")
reaction to item #221 of asympotically fat: The real meaning of particle - and cosmic event horizon is not yet clear to me, so I’m going to study that. The calculation example I mentioned in #220 is 100% based on Hubble’s constant H0, with which you can calculate the recession speed at a given distance from earth. If you know the redshift value of an object, you first calculate the object-speed and then, with the help of H0, you calculate at which distance from earth that speed is valid. At the moment the object released those measured photons, that object was at that distance, so in the past. That was confirmed to me by astronomers. However, like I said, I don’t know about the horizons you mentioned, so I’m going to spend time to find information about it. Thanks! ---
**Author:** ![1iLeft](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/1ileft/32/4114_2.png) [@1iLeft](https://boards.straightdope.com/u/1iLeft)\ **Post date:** [March 26, 2014, 12:03am UTC](https://boards.straightdope.com/t/cosmos-a-waste-of-spacetime/683324/231 "2014-03-26T00:03:02Z")
I never get tired of listening to Carl lecture. Thanks for the links above. Here’s a few more. Carl Sagan - Pale Blue Dot - Audiobook - YouTube. Carl Sagan’s - Cosmos - Videos - YouTube. (all thirteen episodes) Carl Sagan - Demon Haunted World - Audiobook - YouTube. (not Carl’s voice - but words) ---
**Author:** ![Asympotically\_fat](https://avatars.discourse-cdn.com/v4/letter/a/e47c2d/32.png) [@Asympotically\_fat](https://boards.straightdope.com/u/Asympotically_fat)\ **Post date:** [March 26, 2014, 1:01am UTC](https://boards.straightdope.com/t/cosmos-a-waste-of-spacetime/683324/232 "2014-03-26T01:01:48Z")
> [@klaas](#): > > reaction to item #221 of asympotically fat: > The real meaning of particle - and cosmic event horizon is not yet clear to me, so I’m going to study that. The calculation example I mentioned in #220 is 100% based on Hubble’s constant H0, with which you can calculate the recession speed at a given distance from earth. If you know the redshift value of an object, you first calculate the object-speed and then, with the help of H0, you calculate at which distance from earth that speed is valid. At the moment the object released those measured photons, that object was at that distance, so in the past. > That was confirmed to me by astronomers. However, like I said, I don’t know about the horizons you mentioned, so I’m going to spend time to find information about it. Thanks! The whole subject of various horizons and surfaces in cosmological models can be very confusing, you can read a lot of incorrect and misleading things about them because they can be a source of confusion even among astronomers and astrophysicists. The best way to understand the particle horizon is that if a galaxy is outside of your (current) particle horizon it means that you can’t currently see it and the best way to understand the meaning of the cosmic event horizon is that if a galaxy is currently outside of your current cosmic event horizon you will never at any point in the future be able to see the galaxy as it currently appears. However even these descriptions are not the complete picture, for example it is technically possible (though not possible for practical purposes) to be able to observe objects that never enter the observable Universe as defined by the particle horizon if they are receding from us with a velocity additional to their recession velocity. In practice you can only approximately calculate approximate distances from red shifts using the current value of Hubble’s constant for smaller red shifts, for larger red shifts it becomes completely inaccurate. [Previous page](https://boards.straightdope.com/t/cosmos-a-waste-of-spacetime/683324.md?page=11)