Big Bang, Big Claim: Why This Bold Idea Is Right

Space.com ^ | Apr 21, 2018 | Paul Sutter, Astrophysicis | LiveScience

[ETL]

At 13.8 billion years ago, our entire observable universe was the size of a peach and had a temperature of over a trillion degrees.

That's a pretty simple, but very bold statement to make, and it's not a statement that's made lightly or easily. Indeed, even a hundred years ago, it would've sounded downright preposterous, but here we are, saying it like it's no big deal. But as with anything in science, simple statements like this are built from mountains of multiple independent lines of evidence that all point toward the same conclusion — in this case, the Big Bang, our model of the history of our universe.

But, as they say, don't take my word for it. Here are five pieces of evidence for the Big Bang:

#1: The night sky is dark

Imagine for a moment that we lived in a perfectly infinite universe, both in time and space. The glittering collections of stars go on forever in every direction, and the universe simply always has been and always will be. That would mean wherever you looked in the sky — just pick a random direction and stare — you'd be bound to find a star out there, somewhere, at some distance. That's the inevitable result of an infinite universe.

And if that same universe has been around forever, then there's been plenty of time for light from that star, crawling through the cosmos at a relatively sluggish speed of c, to reach your eyeballs. Even the presence of any intervening dust wouldn't diminish the accumulated light from an infinity of stars spread out over an infinitely large cosmos.

Ergo, the sky should be ablaze with the combined light of a multitude of stars. Instead, it's mostly darkness. Emptiness. Void. Blackness. You know, space.

The German physicist Heinrich Olbers may not have been the first person to note this apparent paradox, but his name stuck to the idea: It's known as Olbers' paradox. The simple resolution? Either the universe is not infinite in size or it's not infinite in time. Or maybe it's neither.

#2: Quasars exist

As soon as researchers developed sensitive radio telescopes, in the 1950s and '60s, they noticed weirdly loud radio sources in the sky. Through significant astronomical sleuthing, the scientists determined that these quasi-stellar radio sources, or "quasars," were very distant but uncommonly bright, active galaxies.

What's most important for this discussion is the"very distant" part of that conclusion.

Because light takes time to travel from one place to another, we don't see stars and galaxies as they are now, but as they were thousands, millions or billions of years ago. That means that looking deeper into the universe is also looking deeper into the past. We see a lot of quasars in the distant cosmos, which means these objects were very common billions of years ago. But there are hardly any quasars in our local, up-to-date neighborhood. And they’re common enough in the far-away (that is, young) universe that we should see a lot more in our vicinity.

The simple conclusion: The universe was different in its past than it is today.

#3: It's getting bigger

We live in an expanding universe. On average, galaxies are getting farther away from all other galaxies. Sure, some small local collisions happen from leftover gravitational interactions, like how the Milky Way is going to collide with Andromeda in a few billion years. But at large scales, this simple, expansionary relationship holds true. This is what astronomer Edwin Hubble discovered in the early 20th century, soon after finding that "galaxies" were actually a thing.

In an expanding universe, the rules are simple. Every galaxy is receding from (almost) every other galaxy. Light from distant galaxies will get redshifted — the wavelengths of light they're releasing will get longer, and thus redder, from the perspective of other galaxies. You might be tempted to think that this is due to the motion of individual galaxies speeding around the universe, but the math doesn’t add up.

The amount of redshift for a specific galaxy is related to how far away it is. Closer galaxies will get a certain amount of redshifting. A galaxy twice as far away will get twice that redshift. Four times the distance? That's right, four times the redshift. To explain this with just galaxies zipping around, there has to be a really odd conspiracy where all the galactic citizens of the universe agree to move in this very specific pattern.

Instead, there's a far simpler explanation: The motion of galaxies is due to the stretching of space between those galaxies.

We live in a dynamic, evolving universe. It was smaller in the past and will be bigger in the future.

#4: The relic radiation

Let's play a game. Assume the universe was smaller in the past. That means it would have been both denser and hotter, right? Right — all the content of the cosmos would've been bundled up in a smaller space, and higher densities mean higher temperatures.

At some point, when the universe was, say, a million times smaller than it is now, everything would have been so smashed together that it would be a plasma. In that state, electrons would be unbound from their nuclear hosts and free to swim, all of that matter bathed in intense, high-energy radiation.

But as that infant universe expanded, it would've cooled to a point where, suddenly, electrons could settle comfortably around nuclei, making the first complete atoms of hydrogen and helium. At that moment, the crazy-intense radiation would roam unhindered through the newly thin and transparent universe. And as that universe expanded, light that started out literally white-hot would've cooled, cooled, cooled to a bare few degrees above absolute zero, putting the wavelengths firmly in the microwave range.

#5: It's elemental

Push the clock back even further than the formation of the cosmic microwave background, and at some point, things are so intense, so crazy that not even protons and neutrons exist. It's just a soup of their fundamental parts, the quarks and gluons. But again, as the universe expanded and cooled from the frenetic first few minutes of its existence, the lightest nuclei, like hydrogen and helium, congealed and formed.

We have a pretty decent handle on nuclear physics nowadays, and we can use that knowledge to predict the relative amount of the lightest elements in our universe. The prediction: That congealing soup should have spawned roughly three-fourths hydrogen, one-fourth helium and a smattering of "other."

The challenge then goes to the astronomers, and what do they find? A universe composed of, roughly, three-fourths hydrogen, one-fourth helium and a smaller percentage of "other." Bingo.

There's more evidence, too, of course. But this is just the starting point for our modern Big Bang picture of the cosmos. Multiple independent lines of evidence all point to the same conclusion: Our universe is around 13.8 billion years old, and at one time, it was the size of a peach and had a temperature of over a trillion degrees.

[ETL]

Ummmmm - maybe the author didn't see the story where they pointed Hubble at an "empty" part of the sky and ended up detecting galaxies upon galaxies......

Not quite, There are millions of light years between those (and most) galaxies. They only appear close in the sky in that image because it's looking out to 12-13 billion light years. ONE light year, the *distance* light travels in a year at its fixed speed of 186,000 miles per second, works out to about 5.9 Trillion miles.

[ETL]

The Hubble Deep Field (HDF) is an image of a small region in the constellation Ursa Major, constructed from a series of observations by the Hubble Space Telescope. It covers an area about 2.6 arcminutes on a side, about one 24-millionth of the whole sky, which is equivalent in angular size to a tennis ball at a distance of 100 metres.[1]

The image was assembled from 342 separate exposures taken with the Space Telescope's Wide Field and Planetary Camera 2 over ten consecutive days between December 18 and December 28, 1995.[2][3]

The field is so small that only a few foreground stars in the Milky Way lie within it; thus, almost all of the 3,000 objects in the image are galaxies, some of which are among the youngest and most distant known. By revealing such large numbers of very young galaxies, the HDF has become a landmark image in the study of the early universe.

Three years after the HDF observations were taken, a region in the south celestial hemisphere was imaged in a similar way and named the Hubble Deep Field South. The similarities between the two regions strengthened the belief that the universe is uniform over large scales and that the Earth occupies a typical region in the Universe (the cosmological principle).

A wider but shallower survey was also made as part of the Great Observatories Origins Deep Survey. In 2004 a deeper image, known as the Hubble Ultra-Deep Field (HUDF), was constructed from a few months of light exposure. The HUDF image was at the time the most sensitive astronomical image ever made at visible wavelengths, and it remained so until the Hubble eXtreme Deep Field (XDF) was released in 2012.

[ETL]

https://en.wikipedia.org/wiki/Hubble_Deep_Field

[ETL]

“The field selected for the observations needed to fulfill several criteria. It had to be at a high galactic latitude, because dust and obscuring matter in the plane of the Milky Way’s disc prevents observations of distant galaxies at low galactic latitudes.

The target field had to avoid known bright sources of visible light (such as foreground stars), and infrared, ultraviolet and X-ray emissions, to facilitate later studies at many wavelengths of the objects in the deep field, and also needed to be in a region with a low background infrared ‘cirrus’, the diffuse, wispy infrared emission believed to be caused by warm dust grains in cool clouds of hydrogen gas (H I regions).[6]

These criteria restricted the field of potential target areas. It was decided that the target should be in Hubble’s ‘continuous viewing zones’ (CVZs)—the areas of sky which are not occulted by the Earth or the moon during Hubble’s orbit.[6] The working group decided to concentrate on the northern CVZ, so that northern-hemisphere telescopes such as the Keck telescopes, the Kitt Peak National Observatory telescopes and the Very Large Array (VLA) could conduct follow-up observations.[7]

Twenty fields satisfying these criteria were initially identified, from which three optimal candidate fields were selected, all within the constellation of Ursa Major. Radio snapshot observations with the VLA ruled out one of these fields because it contained a bright radio source, and the final decision between the other two was made on the basis of the availability of guide stars near the field: Hubble observations normally require a pair of nearby stars on which the telescope’s Fine Guidance Sensors can lock during an exposure, but given the importance of the HDF observations, the working group required a second set of back-up guide stars. The field that was eventually selected is located at a right ascension of 12h 36m 49.4s and a declination of +62°[6][7] it is approximately 2.6 arcminutes in width,[2][8] or 1/12 the width of the Moon. The area is approximately 1/28,000,000 of the total area of the sky.[9]”

https://en.wikipedia.org/wiki/Hubble_Deep_Field#Target_selection

[DungeonMaster]

Ummmmm - maybe the author didn't see the story where they pointed Hubble at an "empty" part of the sky and ended up detecting galaxies upon galaxies......

The original argument "the sky is dark" is a red herring because it leaves out the definition of dark and light.

[ETL]

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[trebb]

Understood - my point was there is a difference between “looking” at the night sky and using a tool that can see much better than us to see further into the “empty” spots - those distances you mention belie the argument that “in an infinite universe one wouldn’t see any empty spots...” (or something like that).

[Chode]

i'll prolly get slapped for this, but... space is flat?

i would have thought it is spherical?

[ETL]

The geometric terms flat, opened, and closed, depend on the overall amount of mass in the universe. Just the right amount and the geometry of the universe is such that parallel lines will remain parallel. Lesser amount of mass and the lines will diverge. Over the amount and the lines will eventually converge. Flat is the first scenario. Opened, the second, and closed, the third. You can think of flat as a cubical grid system, like a Rubrics Cube.

[Chode]

but spherical in all directions X,Y and Z?

[ETL]

Spherical would be a “closed” universe. It would imply that the universe contains so much mass that it will eventually curl up on itself. However, observations indicate that the universe is actually flat, or perhaps opened, given the fact that the expansion is now believed to be accelerating.

[ETL]

Yes, but even with that Hubble Deep Field image, and others of the sort taken of different regions of the sky, there remain dark patches where there are no galaxies. Then again, more galaxies likely exist beyond the so-called ‘observable universe’. Beyond the OU galaxies and all else arspeed,eding faster than light speed via the big bang expansion.

[Texas Songwriter]

Why regress the expansion only back to the size of a peach.? Einstein, Hubble, Eddington, Hoyl, Wilson, Penzias, and many others regress back beyond the peach to ex nihlo universe. Then suddenly......the universe came to be.

[trebb]

Thanks - always interesting to interact with you and see the subjects you post about.

[Fightin Whitey]

Where was the peach to begin with?

Somebody cobbled it together.

[Fightin Whitey]

Then suddenly...the universe came to be.

Isn't that the truth of it?

They don't have a clue.

Given our means of understanding, something can't come from nothing, and yet it did.

Given our means of understanding, at least as I understand it, there is no way possible that any of us is here, and yet we are.

It is a miracle and a power and a gift so vast that we ought to quiver and rejoice every moment of every day.

[Chode]

OK, i guess i dint state my question correctly

i dint mean as a boundary but radiating outwardly in a uniform expansion in all possible vectors

[ETL]

They don't have a clue. Given our means of understanding, something can't come from nothing, and yet it did.

In so-called "empty" space things materialize all the time. They call the objects "virtual particles". They are the basis for the "Vacuume Genesis" (pre-Big Bang) theory I referred to in an earlier post (above).

[ETL]

Virtual Particles: What are they?

The term “virtual particle” is an endlessly confusing and confused subject for the layperson, and even for the non-expert scientist. I have read many books for laypeople (yes, I was a layperson once myself, and I remember, at the age of 16, reading about this stuff) and all of them talk about virtual particles and not one of them has ever made any sense to me. So I am going to try a different approach in explaining it to you.

The best way to approach this concept, I believe, is to forget you ever saw the word “particle” in the term. A virtual particle is not a particle at all. It refers precisely to a disturbance in a field that is not a particle. A particle is a nice, regular ripple in a field, one that can travel smoothly and effortlessly through space, like a clear tone of a bell moving through the air. A “virtual particle”, generally, is a disturbance in a field that will never be found on its own, but instead is something that is caused by the presence of other particles, often of other fields. ...”

Lots more at link...

https://profmattstrassler.com/articles-and-posts/particle-physics-basics/virtual-particles-what-are-they/

[ETL]

Here’s a brief video clip explaining the pre-big bang theory known as Vacuum Genesis.

https://m.youtube.com/watch?v=euRZwo0PBHU