Astronomy and Cosmology

In my spare time I will be writing a series of useful articles to help answer common questions. As these are being designed for forum reference I feel strongly on cooperative review. Here is the first. Please look over and feel free to make suggestions. Any solid contributions will be accorded credit at the end of the final product. (Key note all articles MUST comply with textbook descriptives, they are being designed as teaching aids) [latex]\textbf{The Cosmological principle}[/latex] is defined as "at sufficiently large scales, the universe appears as homogeneous and isotropic." [latex]\underline{Homogenous}[/latex] is oft defined as " no prefer…

this thread can be for stashing links to webpages with good explanations of astronomy stuff in Cosmology forum I just saw where aman asked about the slingshot effect (used a lot to save fuel on missions to the outer planets) and swansont gave this link: http://www.mathpages.com/home/kmath114.htm explaining clearly how the slingshot maneuver gains energy and angular momentum (taking away from the planet being used) and then Jenab confirmed having seen slingshotting in simulations he'd run http://www.scienceforums.net/forums/showthread.php?p=30823#post30823 I'm thinking of adding other good links i see to this thread, to have them handy. like link-answe…

Before posting on cosmo topics consider getting squared away on the conventional standard version. There are several great tutorials, for which I'll post link. And the standard model universe is embodied in some online calculators---playing around with them gives you some hands-on experience with redshifts, recession speeds, distances and so forth. Here's the authoritative up-to-date Einstein-Online tutorial on cosmology, written in understandable non-mathy language. http://www.einstein-online.info/en/spotlights/cosmology/index.html It is the cosmology part of a broad outreach site maintained by the Albert Enstein Institute, a worldclass science outfit in German…

Just a reminder that there is a Team SFN on the BOINC network, which you can join if you are running programs such as Seti@home. Blike set it up a while ago but I don't think it was ever advertised http://setiathome.berkeley.edu/team_display.php?teamid=134923

Why do cosmologist say there are flaws in the universe? A number of people who study cosmology say there are number of flaws with the universe. They have hard time understanding why the universe was design that way. What are these flaws with the way the universe works? They say if God created the universe it should not have been created this way because of the flaws with the way the universe works. There was video on youtube showing how cosmologist are puzzled why the universe has these big flaws.

I have no doubt that I'm about to be wrong, but... What if dark matter + space/time = gravity and space/time without dark matter = freedom of movement without restriction which = expansion. I think of it as dark matter somehow activates space/time, would that mean there's region's of space in which relativity does not apply? Just a brain fart, but I'd love to know why I'm wrong, preferably in a language I sort of understand...

Chanced upon this rather interesting application of gravitational waves to determine Hubble constant. Thats definitely one uses I would never have thought of lmao. Measuring intervening density ( underdense, overdense) I have thought of a few times but not Hubble constant. https://arxiv.org/pdf/2503.01997 It is nice to see that this also applies the evolutionary density to Hubble constant via E(z)=\sqrt{\Omega_r(1+z)^4+\Omega_m(1+z)^3+\Omega_k(1+z^2)+\Omega_\Lambda} which is used in a wide range of measurement related equations for far field measurements. (Beyond Hubble horizon ). Note use of E here is not energy, it is expansion rate at a given Z instead of using H_z an…

In orbital mechanics it is mathematically impossible to extract the true orbital velocity [math]\beta[/math] and the inclination angle [math]i[/math] from [math]K \propto \beta \sin(i)[/math] exclusively using a 1D spectroscopic curve as input. Resolving this requires independent 3D spatial data (astrometry) or transit observations. However, within a relational approach, this limitation can be bypassed (apparently) by isolating a second-order systemic scalar invariant, [math]Z_{sys} = \frac{1}{\sqrt{1-\frac{R_{s}}{r}}} \frac{1}{\sqrt{1-\beta^{2}}}[/math]. This invariant is strictly proportional to the absolute kinetic ([math]\beta^2[/math]) and potential terms, but indep…

This lecture is scheduled for the 28th Feb, but looks interesting s I am sharing here. I have also asked on Mastodon if a recording will be available. AllEventsAstronomy vs The billionaire space race

In an inflationary (or anti inflationary,I suppose) universe are there spacetime curvature effects leading to different time/space measurements wrt two different reference frames? I understand that the universe is apparently flat in terms of curvature but does its agreed expansion mean that measurements need to be adjusted to account for it?

I understand we have the concept of a universal heat death where (I think) all that remains is random interactions between objects (ie particles?) that never lead to anything of more consequence. Could those random interactions lessen in frequency over time so that eventually there are none and we can say nothing is moving ?(if there are no interactions how can an object "move" just with respect to itself?) Does an end of absolutely everything become possible in those circumstances? If it does ,would/could that rule out any restart? BTW the forum seems to be getting very ,very slow also- ironically.

🧐 It has been over twenty years since it became apparent that the Universe is full not only of red-dwarf stars , but also of rocky planets orbiting said stars . The scientific consensus since then has become that these worlds are relatively hostile to life , and thus are not suitable candidates for future inhabitation . The reasons for this are varied , and include environmental factors such as extremely intense radiation regimes , inadequate volatile resources , and inadequate atmospheric densities . There are however , several significant underappreciated mitigating factors which could potentially moderate the abovementioned negative ones , and result in these particula…

Even if we accept that errors are natural to humans, why, after so many years, have they still not corrected them? Error one According to Rømer, light took approximately 22 minutes to cross the diameter of Earth’s orbit. Error two Earth–Sun distance (1 AU) light takes to travel → 11 minutes What did Rømer actually measure: the Sun or Jupiter's moon Io? Error three Can't they even write properly whether it is 5:35:45 pm or 5:35:45 am? The single most important observation (the one Rømer quoted most): November 9, 1676: The moment Io began to disappear behind Jupiter Actually observed time → 5:35:45 PM (Paris local time) Expected time according to existing tables → 5:25:15 P…

Ole Rømer research confirmed four things: But only one of these has come to our attention, the remaining three have never come to our attention. First, the speed of light is finite. Second, light transfers energy in real-time. Third, the speed of light involves acceleration. Fourth, light dependent of source. Measurement Data (Rømer's Records) August Closer (~4.2 AU) Earlier (than predicted) February Farther (~6.2 AU) Later (11 minutes after prediction) Ole Rømer (1644–1710) was a Danish astronomer. He is renowned for being the first to measure the speed of light in 1676. At that time, many scientists believed that light traveled instantaneously. Rømer’s research proved t…

I would like to argue that our own place in time and space is the exact location from where the universe expands. Our own moment in time (now) and location in the universe is the exact place from where we leave our own action into the past while we "travel" into the future while we create or shape the future. For this moment I am not sure if this rather is philosophical or if this is also a possibility in the "real" reality. So I love to hear some thought about this concept of spacetime and the idea that "now" is the absolute boundary of the expanding universe. This would say that we all are living as "multi entities" or parallel universes next to each other from where …

Hi everyone!👋🏻 I’m studying fluctuations in high-energy nuclear collisions — how matter behaves under extreme conditions, like after the Big Bang. I use C++ and computer simulations for this. Has anyone else worked with nuclear matter simulations? Happy to chat and share ideas! 😊

I'm currently studying solar radio emission using a time-dependent approach to understand how different solar events affect the intensity and frequency of the emitted radiation. My work involves modeling radio bursts and investigating how the dynamics of coronal plasma lead to various types of radio emissions. Is anyone here studying similar topics, interested in this field, or using time-dependent models to analyze radio bursts?

Hey everyone! I’m working on 2D classification of gravitational wave signals (using spectrograms), but the detector noise is giving me a hard time. Has anyone here dealt with noisy GW data before? What kind of preprocessing or denoising methods worked best for you before training your model — like CNNs, autoencoders, or something else? Would love to hear your experiences or tips! 🚀

Hi everyone! 👋 I’m working on my Master’s thesis about modeling Nova-like variable stars using PHOEBE to analyze and fit their light curves. Has anyone else used PHOEBE for modeling accretion disks or star spots? I’d love to hear how you approached it! 🌟

I’m studying the decay of the ^{11}Be halo nucleus using a non-stationary (time-dependent) approach. My research focuses on modeling the breakup dynamics and exploring how halo structures behave under weak binding conditions. Does anyone here work on time-dependent nuclear models or halo nuclei simulations? Would love to exchange ideas or discuss numerical methods! 😊

Assuming 3i/Atlas is experiencing a deceleration 0,00000002 m/s², would its detection be unavoidable?

Modern physics is CPT symmetric, requires eternalism/Einstein's block Universe philosophy of time - assuming our Universe will finally collapse, the situation before such Big Crunch (BC) seems quite similar to after our Big Bang (BB). It brings many questions (yellow), maybe also answers - I would like to propose to discuss. For example: 1) From entropy perspective, thermodynamical parameters like densities seem very similar near BB and BC - so shouldn't the final entropy be similar? But if so, it means finally entropy should start decreasing - does it mean reversed 2nd law of thermodynamics near BC? How would evolution backward from BC differ from evolution forward fro…

What effects on Earth would we see if its orbital velocity was balanced with Jupiter's gravity at Moon distance to maintain a stable orbit? Assume everything is as it is now and we suddenly found Earth in that situation.

Is there anyone on here that can help me?

Is anyone else following the apparent discovery of objects in Earth orbit pre 1957 by Dr. Beatriz Villarroel while looking at old astronomical photography plates from Mt Palomar Observatory? It would appear that several objects were photographed by the Mt Palomar telescope in 1952 that appeared to be in Earth orbit https://www.researchgate.net/publication/394040040_Aligned_multiple-transient_events_in_the_First_Palomar_Sky_Survey These transient events are difficult to explain, I will post a youtube video explaining these transient events you can watch if you want. https://www.youtube.com/watch?v=MsV9wI4J2ic https://www.reddit.com/r/Astronomy/comments/1mjpa5k/aligned_…