Astronomy, Cosmology, and the Big Bang.

I know this isn't about Evolution, of course. But Big Bang and Evolution always seem to be intertwined for some odd reason. (Maybe because both fly in the face of Young Earth. Not sure.)

So, I am starting this thread, hoping it will be fruitful.

First of all, what is Cosmology?

Cosmology is Astronomy times one million.

Cosmology is the study of the universe. The universe at its largest scale. Even the farthest, deepest, earliest corners of the observable universe.

While estimates among different experts vary, an acceptable range is between 100 billion and 200 billion galaxies in the observable universe. While others put the number closer to 4 TRILLION. (Numbers which rival the national debt.)

But what is Cosmology to me?

To me, Cosmology is the study of Creation itself.

Yes. Genesis.

Cosmology is over 13 billion years of Gods hand, at work. And, by limiting the speed of light, God has built in a way we can look back into the past, and watch Him work in real time. Like no other branch of science, Cosmology brings us closer and closer to the Mind of God.

Cosmology is a very young science. Beginning with the Hubble telescope, and more recently the James Webb Telescope.

And while Cosmology has given us many answers, many questions remain unanswered still.

Galactic chaos at cosmic noon may have stunted Milky Way planet formation

The Milky Way keeps its planets close to its chest. Stars in a thin, flat disk bisecting the galaxy have more planets on average than stars in a thicker, enveloping disk — and astronomers now think they know why.

Stars that currently live in the galaxy’s thick disk were born during a time of galactic chaos, says MIT astrophysicist Tim Hallatt. The stars’ violent upbringing hindered their ability to grow and retain planets, he and astrophysicist Eve Lee, formerly of McGill University in Montreal, report January 22 in the Astrophysical Journal.

The Milky Way’s stars live mostly in two neighborhoods. Young, hip stars stick together in a thin disk, orbiting as if they’re all sitting on the same flat spinning record. Older stars, about 10 billion years and up, appear to have moved to the suburbs, residing in a thick disk of stars whose orbits take them above and below that main plane.

Most of the stars in the thin disk host at least one planet, astronomers think. Observations show that nearly half have a planet whose size is between Earth’s and Neptune’s. “As far as we can tell, the dominant outcome of planet formation in the Milky Way is to produce these super-Earths and sub-Neptunes,” Hallatt says.

But as a population, stars in the thick disk seem to have about half as many of these relatively small planets as the thin disk stellar population does.

“The puzzle is, these planets are very common,” Hallatt says. “And yet when we look at this other dominant population of stars in the Milky Way, they’re less common. So what’s going on?”

Hallatt thinks it’s a question of when these stars were born, not where they live now. Thick disk stars were born in an epoch when the Milky Way was furiously producing stars, a time astronomers call cosmic noon. “It was the most intense period of star formation ever.”

All those newborn stars sent powerful winds of radiation into their cosmic neighborhoods. That radiation could have wreaked havoc on any protoplanets trying to form around the stars, Hallatt says.

He and Lee, who is now at the University of California, San Diego, calculated how much radiation an average star at cosmic noon would have experienced from its neighbors. They found that this background radiation was 1 million to 10 million times what stars experience in a modern star-forming region.

That much radiation could erode a planet-forming disk within a few hundred thousand years, the pair calculated.

“These stars, having been born at cosmic noon, had less opportunity to form planets because their disks were destroyed,” Hallatt says. Astronomers think that such disks around modern stars last for millions of years before they finish forming planets.

Hallatt focused this study on super-Earths and mini-Neptunes, but he thinks the conclusion holds for larger planets, too. “If our theory is correct, and these disks really didn’t live very long at cosmic noon, we would expect it to be even harder to form giant planets.”

If you want to name the cause of the Universe that we observe that's fine but let's not fool ourselves into thinking we can infer very much from that.

Do you think when the universe began, it began in a tiny little dot, with everything in it, and if so, why? Couldn't it have just as easily started looking like a mature universe with planets and stars fully formed?

T_M - the observation that our Universe is expanding was made less than a century ago but it made us realise that the majority (*) of galaxies are rushing away from one another. And if a number of bodies are moving away in that way it's possible to trace their paths backwards to a single point.

That's simply the fact of what we see whether or not it makes very much sense.

(*) Due to the effects of 'local' gravity some galaxies are actually pulling closer together. The Milky Way and the Andromeda Galaxy are on a collision course and will merge in several billion years.

That is true, but what it does not do is tell us the formation of the universe when it started, it only shows us what is doing now.

That's not correct T_M. It's possible to use very powerful telescopes like the James Webb to look back a long way in time to extremely distant objects and when astronomers do this they see stars that existed in the early Universe.

Spectral lines of these stars show that they consist almost entirely of Hydrogen and Helium without the heavier elements that we see in the spectral lines of our own star, which formed much later. That's to say the observations confirm the theory that when the Universe began it consisted of those two simple elements and nothing else.

Look into a telescope, look at fossils, and think we know a lot about the past. I agree the expansion shows us there was a beginning; no one, I think, disputes that any more than they dispute the Earth moves. Again, what did the universe look like when it started? A very small singularity, or a fully established universe with fully formed stars and planets, a telescope, and a fossil are quite silent on that piece of information.

What do you mean by "planets" at the beginning of our Universe? The kind we see in our own solar system, such as Venus, Mars, Jupiter and Earth of course?

They either formed after a BANG as the dust settled so to speak, or at the beginning they were there fully formed.

Well, we have looked back 13 billion years, and the galaxies and planets were formed then. So, there is that much. But the stars and galaxies were much younger. And much more densely packed, And no evidence of and heavy elements yet. So, we couldn't say "fully formed." But there, yes.

What was before that? No way we will ever know, probably. Nobody had "turned the lights on" yet. There were no stars. So, we cannot see any further back.

So, your theory might have some merit. Two problems though:

1. The universe is expanding, like the BB theory says it should be
2. There is cosmic background radiation, like the BB theory alone predicted there would be.

So, so far, the BB theory is the only theory getting its major predictions right. Putting it in the drivers seat, for the time being.

But by 'they' do you mean rocky planets such as Venus, Earth & Mars?

You looked back 13 billion years. Did you use a TARDIS or some time machine? Suggesting the universe was younger in the past is not much of a revelation; saying galaxies were much younger again is not much of a revelation. The trouble you have is you do not know how it all started; you are looking at what you see in the here and now and drawing conclusions about whether this or that continues the way you think. No one disputes the universe expansion, so going backward would mean it is more compact, but how far back should we go before we reach the beginning? Do you know what it looked like when it started?

Everything started when the universe began. Did they start off with a bang, and dust flew out and formed all of the material in the universe? Did they start off fully formed where they were only closer together? How close were they?

I get the feeling you're evading my question so here's the simple & scientific explanation for why rocky planets could not have existed before many hundreds of millions of years had passed:

Rocky planets such as Mercury, Venus, Mars & Earth are comprised of a host of marerials made from heavier elements - Silicates, Iron Oxide, Aluminium compounds etc. But these are formed in stars, especially exploding stars. When we look back to the earliest time in our Universe these elements are absent and we see only Hydrogen & Helium.

There is no reason to believe that planets existed from the beginning.

And when did the elements form?

Which elements?

All of them, of course, in the beginning, what did it all look like? Was it all at the most fundamental basic building blocks before it started to congeal and form elementary elements? Were the elements the basic building blocks, the particles that flew away from the Big Bang? What did it all look like?

The early Universe was comprised mostly of the simplest elements, Hydrogen & Helium. This article explains it much better than I can...

https://home.cern/science/physics/early-universe

"In the first moments after the Big Bang, the universe was extremely hot and dense. As the universe cooled, conditions became just right to give rise to the building blocks of matter – the quarks and electrons of which we are all made. A few millionths of a second later, quarks aggregated to produce protons and neutrons. Within minutes, these protons and neutrons combined into nuclei. As the universe continued to expand and cool, things began to happen more slowly. It took 380,000 years for electrons to be trapped in orbits around nuclei, forming the first atoms. These were mainly helium and hydrogen, which are still by far the most abundant elements in the universe. Present observations suggest that the first stars formed from clouds of gas around 150–200 million years after the Big Bang. Heavier atoms such as carbon, oxygen and iron, have since been continuously produced in the hearts of stars and catapulted throughout the universe in spectacular stellar explosions called supernovae"

Why is it reasonable to believe in a theory such as the "Big Bang"? Because observational evidence and theoretical analysis supports it.