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Everything posted by Mordred
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Unfortunately a lot of people are hung up on the medium for light propagation. I've never really had a problem with that hurdle. Never really understood the hangup. Common reasoning seems to be sound requires a medium. Yet one can simply ask. If I throw a ball do I require a medium for the ball to get from a to b ? My physics instructor in grade 6 asked that to the class. Might have been what prevented me from getting caught on the same hangup. Though that still doesn't define real
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nice reference and example Studiot. I don't want to add anything just yet. Might add confusion. My explanations often do lol.
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How about strengthening the interferance under a stronger gravitational interaction ? Wouldn't that be easier to detect? If you can't detect an interference at 1 g, using zero g wouldn't necessarily help. Part of the reason the link is using larger objects. Just like smaller slits increase the interference.
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If the universe is finite and bounded yes.
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Time is the cause of motion (hijack split from Time)
Mordred replied to stupidnewton's topic in Speculations
Yes but none of the above has anything to do with time causing motion. Everything you described above amounts to how we measure change. Whether its length or time The Op is essentially stating rate of change (time) causes motion. Essentially stating time has energy (ability to perform work) which nothing you've stated above suggests. Just because an object has had sufficient time to get from a to b does not mean time causes the object to move from a to b. -
Up to a point, those transforms you posted are no longer accurate when Janus described any dynamic where it is an acceleration. Which includes change in magnitude and direction. Once you undergo acceleration you must reestablish simultaneity under a different transform (synchronization) which will follow a hypola curve. The twin that undergoes (rapidity=acceleration) is the inertial twin (not at rest).
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😅😂😂😂 Good one +1 But first you gotta agree where coordinate (0,0,0,0) is lol
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Correct provided its within a possible causal connection to our OU. Think of two observable universes overlapping. If there is an overlap you have a causal connection. However only in the overlapped regions. That's your causal connected region.
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technically yes this is correct we can only approximate how our observable portion evolves over time
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Its a huge subject to learn cosmology. It involves essentially every aspect of physics. Thermodynamics is a major portion. The FLRW metric essentially allows us to model the thermodynamics under GR as a reasonable approximation.
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it really depends on what changes between datasets. Hubble constant isn't very telling as its based on current value today. Its not constant over time but constant everywhere at a particular time. There is one formula far more telling. [latex]H_z=H_o\sqrt{\Omega_m(1+z)^3+\Omega_{rad}(1+z)^4+\Omega_{\Lambda}}[/latex] This will give you the value of Hubble's constant at a particular redshift value. The thing about using Hubbles constant to calculate age of universe for example is that you still need to apply the curvature term to get the correct energy/density. The evolution of the mass/energy density however is not consistent. So at some point we draw reasonable approximations. A convenient tool is to map the evolution of the scale factor. Which is non linear, but not too badly so. Depending on what density changes affect expansion rates at different ratios as per the equation above. For example radiation dominant era had a fast expansion rate. The dominant era expansion rate was slowing down. For our current Lambda dominant universe the expansion rate is still slowing but the rate of decrease is less than the matter dominant. Even though we see an accelerating seperation distance the rate per Mpc is gradually decreasing. This is what the Reis paper is essentially doing is it is questioning the reasonable approximations and trying to find a better means to eliminate those approximations.
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Astronomers unveil most detailed map of the Milky Way to date
Mordred replied to Sensei's topic in Astronomy and Cosmology
good link thanks -
Without worrying about whether or not your model works. For symbology one can just use subscripts. ie [latex]t_{cmb}, t_{now}, d_{cmb}, t_{bb}.....[/latex] etc keeps the symbology straight forward with less characters used. If you don't know latex yet just type t_{whatever} your identifying the variable to ie time,distance, coordinate, particular event, etc.
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Well smaller than that really. To give an example. I'll just compare WMAP 2013 to Planck 2013. If you look at what each value each dataset gives for the age of the universe. It will be easiest to see how miniscule the difference is on a smaller volume. ie a parsec. WMAP H_o 69.8 km/s/Mpc age of universe 13.752 Gyrs. @ redshift 1089 proper distance 45.731888 Gly Planck H_o 67.9 km/s/Mpc age of universe 13.787. @redshift 1089 proper distance 45.331596 Gly. You can see on a scale of the observable universe proper distance from the above that an approximate difference of 2 km/s/Mpc is really a small deviation same applies to the age of the Universe calc. In the Reis paper he has only examined local Hubble parameters so via the method he is using he would need to include further statistical error sources such as magnitude luminosity greater than z=5.0 as well as the Hubble horizon and change over of expansion rate due to matter dominant crossover to Lambda dominant at roughly universe age 7 Gyrs.
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After taking some time to read the Reis article. His paper is essentially trying to factor in the statistical uncertainties at various distance ladder stages. In this sense he is factoring in datasets and fine tuning the various statistical error sources by accounting for them using logarithms and additional statistical degrees of freedom. So yes I can see some contention on the end results.
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Yes correct I mentioned indirect thermodynamic evidence earlier this thread.
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Case in point on Real. If there is no way to measure the Lorentz ether or distinquish it. Why would one consider the Lorentz ether as Real? Isn't that being reliant on a mathematical theory that one can never measure? In essence based upon faith of that particular math model ? I always find that amusing.
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mathematics is the lanquage of physics. Both the Lorentz transformations and SR are modelled according to geometrical relations. Under modern treatment the Lorentz transformation tensor has 4 effective degrees of freedom. Due to having 4 coordinates. Enough said. You can't argue because mathematically you know I'm right. Which means according to physics I'm also right to follow the definitions not just willy nilly personal belief and incorrect terminology. Precisely what I have been telling you Thanks for agreeing. That is precisely correct. So why aren't you following the same dimension rules for Lorentz ether? When you know it mathematically indistinguishable from SR? Though force is accounted for by use of the vectors to geometrically model spacetime under the 4 momentum. Quite frankly though it can be argued that there is no 3d objects. You place a box on a table with two atomic clocks. With enough sampling time. You will measure time dilation within that object. Regardless of how small the box is. Which brings up a further argument opposing 3d (Rigid objects) in that under GR there are no 3d rigid objects. Just as in the case of taking same said object, with Earths rotation move the box left and to the right along the equator. You measure a difference in time. So in all honesty is there any such thing as a 3d object? Quite frankly we describe that object as 3d as people are accustomed to Galiliean/Newtonian views. Lol though a particle physicist could argue that the box has 11 dimensions. 3 spatial 1 time 1 electromagnetic (charge is reducible to a vector under a change in sign) 3 strong force Quarks etc 3 weak force. Oops did I just describe the basis of string theory? Technically these degrees of freedom are present in that box. Understanding this might help numerous posters understand what scientists mean by the extra dimensions beyond 4d. Regardless it's only related to this thread as it shows a key issue on how one defines "Real"
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I should have opened the article first lol. The details in this 65 length will take me a bit to examine. At first read I thoroughly enjoyed it. I plan on adding it my collection. Thanks for sharing this.
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thanks I'll have to study it in detail and see where he is getting the differences. Should have time later this evening. Though without reading it. The details should be in the critical density calculations. With density of matter,radiation and cosmological constant. In essence he may have derived a different curvature value
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Lets be careful here Energy is a property Which is the ability to perform work. However mass via infalling matter is lost. So via mass density vs energy density relations in a sense via e=mc^2. Though that adds mass to the BH itself
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While I am familiar with Planck I am not familiar with the Reis paper can you link it?
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No Hubble constant is only constant at all spatial locations at a given time. However the differences in the values above comes from uncertainties in measurement. As we collect more data we reduce the uncertainties.
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A snow clearing challenge for those who like them.
Mordred replied to Dovahkiin's topic in The Lounge
Only for lighter snowfalls the cheaper ones simply don't have the needed HP and your Roller diameter limits the practicality for deeper snow. Particularly as your getting deeper and deeper as you progress with having to move the snow ahead of you. PS them crazy rascally Rabbits.