Astronomy and Cosmology

I have copy and translate this from a french forum : ________________________ The Hubble parameter defined from the scale factor of the FLRW metric is [latex]H(t) = \frac{\dot{a}(t)}{a(t)}[/latex] a parameter representing the expansion rate of the "physical" volume of a compact spatial domain whose coordinates of the points of the surface are constant in co-moving coordinates (i.e., whose material content is always the same) can be defined by [latex]\theta(t) = \frac{\dot{V}(t)}{V(t)}[/latex] We then simply obtain [latex]\theta(t) = 3 H(t)[/latex] Indeed, if we reason on a ball (a volume [latex]V[/latex] whose surface is a sphere), with a radius [l…

https://www.sciencemag.org/news/2019/03/mini-tremors-detected-mars-first-time THE WOODLANDS, TEXAS—After months of delicate maneuvering, NASA’s InSight lander has finished placing its hypersensitive seismometer on the surface of Mars. The instrument is designed to solve mysteries about the planet’s interior by detecting the booming thunder of “marsquakes.” But just a few weeks into its run, the car-size lander has already heard something else: the minute tremors that continually rock our red neighbor. If marsquakes are the drum solo, these microseisms, as they’re known, are the bass line. The signal first became apparent in early February, as soon as the lander …

Planets such as Jupiter that are made of gases don’t just evaporate. Can any member give me the reason?

Was there anything before the big bang?

What's the half life of dark matter?

Does it exist or are we too much enthusiastic for these things? There would need less than 1 cm thickness of tungsten(or lead --> about 1.5 cm) in the coverall to have the same terrestrial weight. What do you think about?

Does it take an infinite time to reach the center of a black hole?

Is there an edge of space or is it infinite?

गामा किरणे दुनिआ की सबसे खतरनाक मानी जाने वाली विद्युत चुम्बकीय विकिरण है , इन्हे फोटान श्रेणी का भी कहा जा सकता है , गामा किरणों की ऊर्जा का स्तर सभी ज्ञात विकिरणों से अधिक होता है ,ये अत्यंत घातक कही जा सकती है। GAMMA RAY Burst अंतरिक्ष की एक अत्यंत शक्तिशाली ,विस्फोटक और विनाशक घटना होती है। इस विस्फोट में इतनी उर्जा निकलती है जितनी उर्जा हमारा सूर्य अपने पूरे जीवनकाल में भी नहीं पैदा कर सकता है। वैज्ञानिकों के मुताबिक Gamma Ray Burst सिर्फ कुछ मिलीसेकेंड्स से लेकर के कुछ मिनट तक का ही होता है पर जो भी चीज़ इसकी चपेट में आती है वह इसके रेडियेशन से हमेशा के लिए खत्म हो जाती है। वैसे तो ब्रह्माण्ड में हर पल इस तरह के उर्जा के भयानक विस्फोट होते ही रहते हैं. यदि इस प्रकार…

Will I be reborn an endless amount of times as the universe starts over and over again?

Does inflationary theory disprove the big bang theory?

https://phys.org/news/2019-02-exiled-planet-linked-stellar-flyby.html Exiled planet linked to stellar flyby three million years ago February 28, 2019, University of California - Berkeley Some of the peculiar aspects of our solar system—an enveloping cloud of comets, dwarf planets in weird orbits and, if it truly exists, a possible Planet Nine far from the sun—have been linked to the close approach of another star in our system's infancy flung things helter-skelter. But are stellar flybys really capable of knocking planets, comets and asteroids askew, reshaping entire planetary systems? UC Berkeley and Stanford University astronomers think they hav…

Is it around 360 earthly hours from dawn to dusk or I have it wrong ?

This is the most surprising news I've heard in years! Old data from the SoHo spacecraft show that Earth's exosphere reaches far longer into space than anyone had ever imagined: 391,000 miles! That's way beyond the Moon! https://www.sciencealert.com/earth-s-atmosphere-is-so-big-that-it-actually-engulfs-the-moon I don't know if this is "Wow!" or "WTF?!" news, but it's up there.

According to researchers, the universe has produced 4x1084* photons since the big bang, with a surprisingly dim effect. So my question is: What has happened to all that energy? I have previously suggested that photons could be involved in the cosmic acceleration, which was rejected. But we know that photons can act as propulsion in solar sails, so why can't they act in the expansion of the universe itself? * That's 4,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000 photons!

The one Billion-solar-mass quasar 3c186 is off center in its' galaxy moving outward at 4.7 million mph (1305 miles per second)!! They think it got fired out of the galaxy when 2 supermassive black holes merged, after 2 galaxies merged. Can you think of more momentum than that? That will tear across the universe, like a bowling ball through pins, and maybe nothing will ever stop or divert it. "A supermassive black hole heftier than 1 billion suns has been ejected from the core of its galaxy by gravitational waves, a new study suggests. The monster black hole has already zoomed 35,000 light-years away from its galaxy's center, farther than Earth and its sun are fr…

Hello, I would like to have values (or how to calculate the values) of [latex]\Omega_b[/latex] (ordinary matter = baryonic) and [latex]\Omega_{\Lambda}[/latex] (density parameter of the cosmological constant) in relation to, or as a function of, the Hubble constant H at different ages of the universe. To verify this relationship: [latex]M_b* \Lambda / 2 \approx 8 Kg/m^{2}[/latex] ( -0.5% compared to 8 = contribution of neutrinos ? ) [latex]M[/latex] for "mass" thank you in advance[

I have no knowledge of particle behavior at different states of energy, except that in stars (very hot) they float around in chaos, outside stars (medium) they form atoms and molecules, and in a singularity they are compact. Dark energy and matter has always puzzled me however. And a while ago I got the idea that photons could play a role in dark energy. My initial though was, that the repulsive force photons contain, could somehow push the universe to accelerate, but lately I've gotten a new idea. The new idea is that photons can create new matter when they hit quantum fluctuating particles. Thus adding volume to the fabric of space and accelerating its ex…

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If a black hole is not feeding, then would inside the event horizon be a total vacuum and all energy contained within the singularity? A non-feeding black hole would be just a singularity and its' gravity?

a few further queries I mentioned earlier (1) I guess there's wind and tidal forces on Titan so maybe we can walk along the beach of one of the methane seas with methane washing up and down? (2) If liquid methane has less than half the density of water, would it still be possible to have powered craft which could float on the surface of Titan's lakes? (3) Could explorers go hang-gliding? Or maybe even a nanolight powered by methane? (4) Presumably with all the methane about, power won't be a problem. When explorers get to Titan I guess temperature suits would have to be powered (unless NASA has an insulation fabric which could withstand −179 °C?) …

A young Scientist has gone ahead to explain the Mystery of why Uranus has Vertical Rings, rather than the horizontal rings seen in other ringed planets. In the early years of our solar system, protoplanets (bodies developing to become planets) collided in violent giant impacts that helped create the worlds we see today. Most researches hold the belief that Uranus’ spin was the result of a one of these collisions. While it is not yet possible to recreate planets in the lab and smash them together to see what happens, what Jacob and his team did was to create computer models simulating the events using a powerful supercomputer as the next best thing. LINK DEL…

Lunar eclipse flash - electrical discharge "...a flash of light seen during totality has astronomers on the hunt for a new crater on the moon...." https://www.nationalgeographic.com/science/2019/01/meteor-hit-the-moon-during-blood-moon-eclipse-heres-what-we-know/ They will likely not find any new crater and here's why: It hit me early this morning: When sunlight hits the Moon's surface, the temperature can reach 260 degrees Fahrenheit (127 degrees Celsius). When the sun goes down, temperatures can dip to minus 280 F (minus 173 C) - pretty extreme. Typically, daytime on one side of the moon lasts about 13 and a half days, followed by 13 and a half night…

Hello! Does it make sense for Black Holes to be the hottest things in the Universe? Since nothing escapes it, light included, we can't actually directly observe any data. But since energy equals heat and the incredible amount of mass and energy packed into them, wouldn't that make them the hottest things in the Universe? And a follow up question. IF we could see a Black Hole, what color would it be?

How much voltage'd can a Van de Graaff generator reach on the Moon? I mean...completely without air!