============================ The State of this Universe ============================ I will try to give updates from time to time as to what is happening here 24/11/2025 ========== A news update is long overdue. I attended :ref:`gramaldi` conference in Glasgow back in July. It was a wonderful experience. I have spent the summer months and more trying to write up what I learnt at the conference. This has taken longer than I had hoped as my understanding of what I believe is happening has improved significantly. In short, Rourke's work implies that black holes do not merge. The principle that Rourke adopts, in addition to General Relativity is the Sciama Principle. This specifies how waves propogate through space time. This results in oscillations of space time. Much of the time these can be ignored, but there are notable exceptions where General Relativity breaks down. Galactic rotation curves are one. The distortion that a galaxy's central black hole makes in space-time, according to the Kerr metric, creates a wave that propogates through the galaxy and induces a coherent rotation on the surrouunding space time, explaining galactic rotation curves without recourse to dark matter. The oscillations of space time itself are in effect the dark matter! The detections of gravitational waves is only possible because those waves propogate through space time. But those oscillations have a firm origin in the rotations of matter. If we work in terms of the angular momentum of a body, then Kerr metric gives how that body distorts space time. This effect drops off rapidly with distance, r, from the body. In fact as 1/r**3, which means it can very often be ignored. Now in the case of binary pulsars, such as Hulse-Taylor, the current separation of the two objects in the binary is large compared to the wavelength of the waves from the millisecond rotation of the primary body. Hence it can be ignored and the observations fit perfectly with the Kerr metric and General Relativity. Regardless of whether black holes can and do merge, there is another explanation for the observations that Ligo, Virgo and Kagra are seeing. In a de Sitter space universe there is horizon due to the curvature of space time. There is an edge to the part of the universe we can see. New quasars or galaxies entering our visible universe burst on the scene highly blue shifted. In the case of a galaxy we see a gamma-ray burst as we see it's entire history in a short period of time. The wave front is shaped by the Kerr metric, but as in the merging black holes there is a hyperbolic rotation going on. I am currently working on this in the gw150914 module. Quantum Gravity --------------- Quantum mechanics models wave particle duality and hence explicitly models the effects of the waves in space time that particles are creating. It is this that is at the heart of the incompatibility of quantum mechanics and General Relativity. Rourke's adoption of the Sciama Principle removes this incompatibility, re-introducing wave-particle duality. 16/4/2025 ========= I have signed up to attend the 24th International Conference on General Relativity and Gravitation. https://iop.eventsair.com/gr24-amaldi16/ There list of invited speakers is exciting and should be an enormous help to this project. https://iop.eventsair.com/gr24-amaldi16/speakers There is also a science and art exhibition for which submissions are invited, so it looks like I will be working on a poster. I have also been working on the green valley problem :ref:`birch`, in particular looking at the data from the Dark Energy Spectrographic Instrument (DESI). The data for data release 1 was recently released publicly. The gotu.desi module downloads data and the :ref:`birch` module has a viewer for the data. 2024/12/04 ========== I very much enjoyed PyCon Ireland and am super grateful for the opportunity to talk about the Geometry of the Universe. I have done significant work on the :ref:`gaia`, visualising the Milky Way's rotation curve, using data from the European Space Agency's Gaia satellite. This includes using the :ref:`healpy` package, which provides equal-area pixellisations of a sphere, as well as spherical harmonic analysis. There is a new paper out from the Pulsar Timing Array team which gives all sky maps of the gravitational wave background based on the MeerKAT pulsar data. Specifically, the 4.5 year data release. It looks like they are using healpy to both perform spherical harmonic analysis and to display the results. https://academic.oup.com/mnras/advance-article/doi/10.1093/mnras/stae2573/7912549 It is wonderful stuff and it is going to be fascinating as more data accumulates over the years. This data provides an excellent test for the Sciama Principle. As well as visualising the Milky Way's rotation curve, using Gaia data, the module can do a simulation, taking a sample of stars at a given distance from the galactic centre and projecting their future trajectory, assuming the Sciama Principle and a large mass at the galactic centre. The resulting simulation fits the 200km/s assymptote well. It remains to model the random motions of stars on their outwards journey as well as the curvature of the universe in the large. .. image:: images/mwsim.png I am still working on adding some random noise to the stars motions and also trying to model a curved universe. The Gaia data is a treasure trove of information to help with this. There is also Appendix D. of the book, which looks at vertex deviation among stars local to the Sun. It is coming to my busy time of the year, where I am outdoors in the snow a good deal. My goals for the next little while are to continue the Milky Way simulation and to explore gravitational waves generated by the Sciama Principle in a de Sitter Universe. 2024/8/28 ========= I will be giving a talk, *Exploring the Milky Way with astropy, matplotlib and Gaia* at Pycon Ireland in Dublin. More information on the talk can be found here: https://sessionize.com/john-gill Over the summer I have been focussing on my understanding uniformly curved space time, trying to understand what it should look like and whether it explains the observations of the Dark Energy Survey and the Hubble tension. At the same time I have been working on visualisations of the Gaia data to explore the Milky Way's galactic rotation curve. Both of these involve two variables, the former distance and tangential velocity, the latter redshift and distance. 2024/4/4 ======== Today's date, 4**3 = 64. It has been a busy winter of explorations. The main module is the :ref:`spiral` module which is an evolving galactic and galaxy simulation. It contains most implementations of most of the key formulae from :ref:`gotu`. The module now include a simulation of new galaxies arriving in a de Sitter Space universe. It produces plots of blue/red-shift against distance for a sample of arrivals. The goal is to understand the observations of supernovae, which gives a good sample of galactic distances and redshifts. This sample is showing that there is more going on than a simple relation between redshift and distance. In Big Bang parlance, the expansion of the universe has accelerated. In the de Sitter model there only an asymptotic relation between redshift and distance. All the galaxies we see eventually recede at the Hubble rate. They burst on the scene, highly blue shifted for what is often a short period of time before they accelerate away from us and reach the Hubble flow. The distribution of galaxies we see is skewed to those that have been around a good while, and those are all approaching the Hubble flow. More particularly, many galaxies do not hang around long enough for a super nova event to happen. When a new galaxy appears it is at the Hubble distance. This is due to the curvature of the universe. For a galaxy beyond the Hubble distance, most of its light bends before it reaches us. See recent commits to the :ref:`spiral` module for more on this. Gaia and the galactic centre ---------------------------- The :ref:`gaia` module can now download data from the ESA's Gaia program and create plots showing the Galactic rotation curve. .. image:: images/gaia.png The image above shows the Milky Way's rotation curve, the tangential velocity, in km/s on the y-axis and the distance from the galactic centre, in kpc on the x-axis. To create the image a grid of tangential velocity (y-axis) and distance from the galactic centre (x-axis) was created. Counts were then done on the 33 million Gaia (data release 3), to establish how many were in each bin. The number of observations at each distance varies significantly as you move out from the galactic centre, so the counts were then normalised by dividing the count in each bin by the sum for all bins with the same distance from the galactic centre. The resulting grid is then plotted with :ref:`matplotlib`, which maps the counts, now in the range [0, 1], to colours based on a colormap. The image is stunning, a real example of how the Gaia mission creates better insight into our own galaxy. This image also assumes that the centre of the Milky Way is actually twice as far away as Sgr A*, which in this image is around 8kpc from the origin, where we see the most common tangential velocity is close to zero. See the :ref:`gaia` module for more on this. 2023/12/7 ========= The big news of the year for the Geometry of the Universe was the detection of nanohertz gravitational waves by the Pulsar Timing Array team. It is a stunning achievement, using pulsars across our galaxy to detect ripples in space time with a period measured in years and an amplitude of just 10m. These low level gravitational waves are a prediction of the theory presented in :ref:`gotu`. As a result I have been using the software here to explore data relating to the the theory. `astropy` has been extraordinarily helpful during this time. It really does have everything you need to explore the very latest observations of the universe. The `units`, `constants` and `cosmology` modules have been particularly useful. All the `cosmology.Cosmology` objects that are provided are instances of the FLRW class, describes itself as *An isotropic and homogeneous (Friedmann-Lemaitre-Robertson-Walker) cosmology*. These provided key parameters such as the split into dark matter, dark energy, baryonic matter, photon energy and the Cosmic Microwave Background temperature. For each parameter there is a corresponding function to give the value of the parameter at a particular *redshift*, z. In FLRW cosmology, z is synonomous with both distance and age. In a cosmology with the Perfect Copernican Principle, these functions all return the value for the current time, since it is assumed these values are constant through time. The :ref:`spiral.Cosmo` class is the beginnings of an attempt to build cosmology objects for a de Sitter universe. The default object takes the current default cosmology from :ref:`astropy` to initialise the values for the current time and sets up functions that return the same value regardless of the $z$. The :ref:`spiral.SkyMap` uses this cosmology to estimate the mass of the universe relative to the observed stellar mass. It uses the *heasarc* catalogue to get estimates of stellar mass for local galaxies. Using this distribution and the Sciama Principle the software simulates the gravitational waves that the galactic centres should create. The intriguing bit is that the waves based on a universe of the Hubble scale generates waves about 45 times smaller than those observed. Which is about the same amount that the Cosmic Microwave Background is brighter than the thermalised energy emitted by all the galaxies in the visible universe. In a de Sitter universe the Hubble distance is also a significant parameter. It is the radius of curvature of the universe. This radius is in no way an indication of the full size of the universe. Light can and does travel very much farther. At the Hubble scale, due to the curvature, it becomes a random walk and after N steps the expected distance from the origin is only sqrt(N) times the step size. So the software let's you set the factor to scale things up by, as well as other parameters. If you are having trouble getting things running then take a look at the :ref:`blume` project, which is something I wrote to help me using :ref:`matplotlib`. 2023/1/9 ======== Time for a new year review of how the models presented in :ref:`gotu` are faring under the scrutiny of the new space telescope. Quasars ------- As time goes on more and more of ARP's peculiar galaxies will be observed by the JWST. Many of these contain examples where Arp observed quasars with intrinsic redshift, caused by the light producing region being close enough to the central black hole to cause gravitational redshift. With the new infrared view, we see these galaxies with a new, improved perspective, providing stronger evidence that they are associated with the galaxy, yet have significantly larger redshift. Distant galaxies in deep fields ------------------------------- Very high red-shift galaxies have been observed by the telescope, in numbers higher than predicted by the current big bang models. There is a lot of freedom in the big bang model, but parameters will need to be tuned. The observations are entirely consistent with the model proposed in :ref:`gotu`. There was no big bang, the universe is essentially static, it is galaxies as far as we can see. The universe also happens to be curved, and this does impact the view. With expanding and contracting fields intertwined, like an Escher drawing. In short, some work to do for the big bang theorists. Galaxy formation models need to be refined. The static universe, with curvature too, is alive and well. CMB --- The Cosmic Microwave background has been in the news too. With the big bang model, the CMB gives the value of the Hubble constant. The problem: other methods of calculating the constant give a value almost 10% higher. This is the so-called Hubble tension, an indication there's something amiss. The :ref:`gotu` explanation for the CMB is that it is the thermalised radiation of all the galaxies back-lighting our view of the universe. It is complicated by the curvature of the universe, that has a visibility horizon at around the Hubble distance. On top of that there are the spherical harmonics that are observed in the CMB to take account of. Sgr A* ------ We already have excellent observations of this central black hole. It is one of the most observed objects in the Universe. According to :ref:`gotu`, it is a baby quasar, in the general direction of the centre of our galaxy, but not actually at the centre. I think in time JWST will allow us to see analogues in other galaxies. This is key to appreciating the true mass of black holes at the centre of galaxies the size of the Milky Way. Gamma-Ray Bursts ---------------- These are assumed to result from cataclysmic events, such as the collision of neutron stars. :ref:`gotu` gamma-ray bursts could herald the arrival of a distant galaxy in our visible universe. We see it's infinite past in a very short period of our time, before the new arrival rapidly recedes according to the Hubble law. The gravitational wave detectors have been upgraded and are ready for another obaservational run, starting in March. We will likely see more gamma-ray bursts with associated gravitational waves. If the distant rotating mass of the galaxy bursts on the scene as blue shifted light, presumably the inertial drag that it exerts on it's surrounding space time is also modulated in the same way. It would be good to try and estimate what these waves actually look like and understand any relation between a gamma-ray burst and a gravitational wave. 2022/12/9 ========= It has been a fascinating year for this project, with the JWST constantly in the news. Since the first pictures in July there has been one beautiful image after another. The data is openly available, considered public domain. The astropy world has done an excellent job making everything accessible. It really is a wonderful time for observations of our universe. Each JWST image also has background data, not necessarily the focus of the particular study that proposed the observation. By making the data available it increases its value as more theories can be tested with a single observation. There is now a :ref:`jwst` module that can be used to download and view JWST data and images. You can pass it the name of your favourite target using the --location option:: python -m gotu.jwst --location ngc1566 The module queries the MAST database to convert the name into sky coordinates and then queries MAST again for JWST observations in that location. It then pops up a matplotlib figure window with a table summarising the records that were found. Press 'r' and it will start downloading and displaying images. I have not got past displaying the images with matplotlib, using random colour maps. There is always something fascinating in these images. Here is a one of NGC 1566, also known as the Spanish Dancer. .. image:: images/ngc1566.png Recently, I have been focussing on the `dss` module, trying to get a natural understanding of Minkowski and de Sitter space, as this is the key to the explanation of why an essentially static universe appears to be expanding. For a while I have been lost in a world of Lorentz transformations, hyperbolic rotations and curvature in five dimensions, with parallel transport of vectors around curves in two dimensional slices. How to visualise it all? How to show what a curved universe looks like? I feel it is the key to showing that there are other universes than a big bang universe, that fit the observations, as any argument for a static universe needs to address red-shift. 2021/12/3 ========= It is very much a work in progress, an outline of ideas. I've tamed the `sphinx`_ enough so that from here most of the documentation will be in the form of comments in code. I am still using some things from another of my projects `blume`_ that gives me an interactive framework to work with. I will likely have to change a few lines of code as blume settles down. Here I should be able to move ahead, knowing very little will need changing here as `blume`_ evolves. Check the news in blume land for how that is going. Plans ----- There are several pieces that need fleshing out at this point. * :ref:`dss`, geodesics, gamma-ray-bursts and red-shift. * :ref:`quasar`, a quasar model. * :ref:`cmb`, a model with all the harmonics. * :ref:`spiral` I also want to rework my code that is downloading Gaia data, to allow me to zoom in on a particular part of the data. .. _sphinx: https://sphinx.readthedocs.io .. _blume: https://github.com/swfiua/blume .. _matplotlib: https://matplotlib.org