IMHO the Universe is expanding outwards at an increasing rate as evidenced by galaxies moving away from each other. Some researchers suggest this expansion may end in just 100 million years and a big crunch will take place where the universe will start contracting on itself. I keep an open mind.Where is the expansion?
Where is the contraction?
Is this simply a matter of any volatile substances present moving, providing they are above absolute zero?nature abhors a vacuum
We explore a Gedanken-model for cosmic evolution, where dark matter is strongly self-interacting and stays in a plasma state until late stages. After decoupling, it condensates to super-structures with cosmic voids similar to the current picture of the universe. With the help of the equation of state of dry foam (equivalently a fluid with voids in it) from fluid mechanics, it is possible to show that tension within these cosmic walls due to their binding interaction may cause an accelerated expansion in the absence of dark energy. Furthermore, we give a cosmological analysis of this scenario with a semi-phenomenological ansatz, where we use recent Type Ia supernova compilation.
Imagine the core of M87 being 0ver 7 billion solar masses and trillions of stars in the galactic envelopeWe report measurements of the gravitationally lensed secondary image -- the first in an infinite series of so-called "photon rings" -- around the supermassive black hole M87* via simultaneous modeling and imaging of the 2017 Event Horizon Telescope (EHT) observations. The inferred ring size remains constant across the seven days of the 2017 EHT observing campaign and is consistent with theoretical expectations, providing clear evidence that such measurements probe spacetime and a striking confirmation of the models underlying the first set of EHT results. The residual diffuse emission evolves on timescales comparable to one week. We are able to detect with high significance a southwestern extension consistent with that expected from the base of a jet that is rapidly rotating in the clockwise direction. This result adds further support to the identification of the jet in M87* with a black hole spin-driven outflow, launched via the Blandford-Znajek process. We present three revised estimates for the mass of M87* based on identifying the modeled thin ring component with the bright ringlike features seen in simulated images, one of which is only weakly sensitive to the astrophysics of the emission region. All three estimates agree with each other and previously reported values. Our strongest mass constraint combines information from both the ring and the diffuse emission region, which together imply a mass-to-distance ratio of 4.20+0.12−0.06 μas and a corresponding black hole mass of(7.13±0.39)×109M⊙, where the error on the latter is now dominated by the systematic uncertainty arising from the uncertain distance to M87*.