What is the Universe expanding into..

Do you think there was anything before the big bang?

  • I don't think there was anything before the Big Bang

    Votes: 56 12.5%
  • I think something existed before the Big Bang

    Votes: 200 44.7%
  • I don't think the big bang happened

    Votes: 54 12.1%
  • I think the universe is part of a mutiverse

    Votes: 201 45.0%

  • Total voters
    447
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So the "coin-core-hobb" 🙂

I don't know what you deem as an explosion... but the coin-core-hobb was quite a whopper of an explosion as I see it 🙂

It was something expanding in 3D - its still expanding in 3D. How even mundane and boring that seem to be, I think we need to accept that as the one resonable description. Why mystify it? Every time you describe it here in this thread, it is what you tell - an explosion in 3D. If you have something else in mind - then please use other words so that I can understand it.

Only if we know that the "edges" stood still, I would accept that there is not an universal expansion... bit rather the pressure increasing - i.e. entropy increasing.

You seem hung up on the short time span of the first part... the very essence of an explosion is that it takes part during a very short period or it wont be called an explosion. Explosion: release of a lot of energy during a very short time ;-) see...? Was the inflation part of the coin-core-hobb without energy exchange?

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...an explosion in 3D. If you have something else in mind - then please use other words so that I can understand it.

I've used the words "metric expansion of space" on numerous occasions, but apparently to no avail!

"The metric expansion of space is the increase of the distance between two distant parts of the universe with time. It is an intrinsic expansion — that is, it is defined by the relative separation of parts of the universe and not by motion "outward" into preexisting space as, for example, an explosion of matter."
 
Cosmic inflation is a 'faster than light' version of metric expansion, the meaning of which I've covered on several occasions (refer to the forum search function).

Cosmic inflation was hypothesised in the 1980s to compensate for failings in the Big Bang theory - a sort of correction if you like.
 
Is metric as in the metric (1 meter SI system) system or does "metric" have a special meaning in context of expansion?

Would you believe I explained this to you just a few months ago?

A coordinate system locates points in spacetime by assigning unique coordinates, to each point.

The 'metric' is a formula that converts the coordinates of two points into distances.

Understanding spacetime requires us to stop regarding 'distance' as an absolute, but as something which is determined by a metric which is changing with time.

It all results from the fact that spacetime is 'non-Euclidean'. An example of non-Euclidean geometry is the Earth's surface. We can use different 'metrics' to measure the distance between two points on the Earth's surface. For example, local mapmaking often ignores the curvature of the Earth.

Since the Earth is not flat, the "distance" between two points (such as Glasgow and New York) may differ depending on the metric used to measure it.

In a similar way, the "distance" between two points in spacetime depends on the metric used to measure it at a particular time.
 
As a keen Astronomer in Portsmouth, UK, I watch the Night skies with interest. Jupiter is ligthing up the skies before midnight, Mars (for the elderly insomniacs) presents an interesting spctacle at 3 AM.

The most interesting news today is the latest JWST images of Neptune. TBH, I have never seen this one in our incredibly light-polluted skies in Portsmouth:

S7 Neptune and the Spiral Galaxies.jpg


S7 Neptune by JWST 2022 Latest.jpg


But here's the thing. Voyager 2 took far better pictures of Triton in 1989!

S7 Triton by Voyager 2 1989 (copy).jpg


BTW, I have no great desire to visit this planet. Looks cold.
 

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Red shift analysis of distant objects indicates expanding universe. However, since "space neither stretches nor gets created, but simply is" then the increase of distance between objects is not caused by more space in between but metric expansion of space which in turn means the formula to calculate distance of objects is a function of time, in which time is also part of spacetime.
Terrific. Over my head terrific. 😉
 
Surely it is Yin and Yang? I say this as a Tai Chi master.

As my wise friend Galu says, you will never understand The Expanding Universe without a basic grasp of what "The Metric" might be!

Here, in terms that even a Child of Ten can understand, is how it works...

S7 Jeff Bezos The Metric.jpg


Time and Distance. It is what we measure. Here in Imperial Units of a half foot, and clock times that work in Imperial or Metric units.. Interestingly, 11.11 is the date and the moment when the Guns fire in the UK ad everybody has a sombre moment.

111 is known as "Nelson" to cricket followers. Usually a wicket falls at that score. I will leave General Relativity for the interested student.

All is Mathematics. 😎
 
Nice to see Sabine Hossenfelder giving the particle physicists the one-two in the Guardian today. Hopefully tomorrow she'll land a few punches on the string theory guys.

(If you've ever watched Brian Greene on YouTube, you'll know where I'm coming from. Snake oil doesn't begin to describe it.)

We need another Einstein. Perhaps Steve is our man 😀

https://www.theguardian.com/commentisfree/2022/sep/26/physics-particles-physicists
 
"Ambulance-chasing is a good strategy to further one’s career in particle physics", says Sabine.

Namely, after every announcement of a preliminary experimental result there is an explosion of theory submissions explaining it.

It often turns out that the result happened to lie within an experimental error bar and can not be confirmed by future measurements.

However, even when wrong, the theory papers receive a fair number of citations, which is clearly advantageous to the careers of the theorists.

https://lemeshko.blogspot.com/2016/04/ambulance-chasing-in-particle-physics.html
 
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