The big bang and expansion of the universe. I have a question for you

The big bang and expansion of the universe. I have a question for you.

Everyone knows the universe is expanding - all the galaxies are getting farther apart from each other. However, all the explanations I've seen have been "the space between them is expanding" - the galaxies don't have velocity of their own, just the space between them is getting bigger. I accept that space can expand, I'm not wondering about whether that's possible.

My question is how do we know it's "space is expanding" and not simply "everything is flying apart"?

Imagine this: you're a very small person riding on a chunk of shrapnel (galaxies) from a recently-exploded grenade (big bang) in an infinite empty room (the universe) with no overall gravity except for between the chunks of shrapnel . From your perspective, no matter whether you're on one of the chunks of shrapnel that got ejected the farthest or one that just barely has velocity out from center, *every* other piece of shrapnel will be moving away from you, right?

A chunk of shrapnel closer to the origin will appear to be moving away from you because you're moving faster than it (that's why you're farther out - you were moving faster from the start).

A chunk of shrapnel farther than you from the origin will be moving away from you because *it's* moving faster than you.

A chunk of shrapnel above you will appear to be moving away from you because it's on a different trajectory - it's moving along a path 60 degrees above the horizon (for example) while you are only headed 30 degrees above the horizon.

The same as above counts for pieces of shrapnel to your left, right, and below you; they're heading in different directions than you, therefore they are getting farther away.

What I'm asking is how do we know that the shrapnel analogy *isn't* the case, and that it's actually just "the space between them is expanding" while the pieces of shrapnel actually don't have any velocity?

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everything is flying apart/space is expanding

same thing

space is expanding is a more useful lingual model. The image it brings to mind is far more accurate to the math then "everything is flying apart". "everything is flying apart" is from our perspective, based on our human senses of the world. When dealing with srs bisnes scientific models and such, "space is expanding" is much more accurate. It's much more accurate.

Your entire model is wrong. Nothing exploded in a big empty space. There wasn't any big empty space. There was nothing (not even space or time). Everything (space, time, energy, mass) expanded from a single "point" called the "big bang."
We know this for a lot of reasons: There is no "central point" in space where everything expanded from, and the current models of expanding space fit perfectly with the observed data.
It boils down to observing, measuring, and recording exactly what's happening in the real, physical universe and coming up with a theory that fits all of the data. Spatial expansion fits the data. A big explosion from a point in pre-existing space doesn't.

Neat

>Nothing exploded in a big empty space. There wasn't any big empty space. There was nothing (not even space or time). Everything (space, time, energy, mass) expanded from a single "point" called the "big bang."

How do we know there was no empty space? How do we know it wasn't a singularity in the "regular" sense, already surrounded by infinite space, which then started expanding, dragging the singularity with it?

I'm not arguing, I'm genuinely curious.

The most accurate theory we have shows space to be expanding. If you run the model backwards, space contracts. Using the measured rate of expansion (backwards), there was a time about 13.7 billion years ago when the size of space was ~0. That was the "big bang". Since the idea of some other kind of "space" outside of the space we experience is unobservable, untestable, and undefinable, it belongs to the realm of metaphysics, not science.

I personally doubt anyone who says "billions of years", but putting that aside for now.

I believe Tesla said electricity is basically degrading magnetism and magnetism is degrading "aether" and any transceiver was as an ocean.

There is this theory that the earth has a water core instead of a magma core. Another that says the earth is ever expanding with our collective consciousnesses.

The Bible : "And God said, "Let there be an expanse in the midst of the waters, and let it separate the waters from the waters.""

Could perhaps the firmament keep our water(terrestrial core) from the aether out there in space. Both of which could be expanding cause of our and others collective consciousnesses. Could be a sort of fail-safe system so primitives cant hop in there primitive rockets and just "blast off" to another planet.

en.wikipedia.org/wiki/Friedmann_equations

The waters above the rigid sky provide rain (and flood), learn ancient cosmology.

The easiest way to get your head around this shit is this.

Imagine a volume. Any size, doesn't matter. Imagine it as a volume without boundaries. Like a room without walls.

Okay, now, instantly fill this volume with nothing but pure energy. All the energy of the existing Universe.

That is the big bang.

Now wait. Dont imagine the volume getting bigger. Just imagine it cooling. That is the first phase of the Universe expanding.

Matter eventually settles out. It becomes transparent. You can see through it. You see galaxies form as these minute glowing specks.

Now, imagine these bit of matter, the galaxies and all, all uniformly SHRINKING.

That is the second phase of the expansion of the Universe. The one we are seeing now.

There is justification for this. To scientists whether the space itself is expanding or the energy/matter within is shrinking makes no difference. Its the same.

In the grenade model, the speed of other shrapnels with which they recede from you would be different for different shrapnels. A shrapnel originating next to yours in the original grenade would have much smaller relative speed to your shrapnel compared to a one from the another side of the grenade.

In current cosmology, by my understanding, the recession speed only depends on the distance between the object and the observer, with no directional dependency. Somehow the shrapnels further away should've gotten more energy from the grenade blast than the ones close by. This is easily explained by uniformly expanding space.

It's also been observed that the mass density of the Universe is quite constant, which wouldn't be the case in the grenade situation when you would only have mass in the expanding ring of shrapnel.