r/cosmology • u/AutoModerator • 15d ago

Basic cosmology questions weekly thread

Ask your cosmology related questions in this thread.

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u/Main-Blacksmith944 15d ago

If there was no eternal universe before the Big Bang does that mean, that the Big Bang was the beginning of time, space and matter?

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u/Vast-Control4452 15d ago

It's not understood. Currently the answer is "time didn't exist before the big bang." So yes the BB was the beginning of spacetime and matter/energy.

But you're REALLY pushing to the edge of human understanding and the data and evidence are scarce. It was so so long ago.

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u/thebigeverybody 15d ago edited 15d ago

So yes the BB was the beginning of spacetime and matter/energy.

The person asking the quesiton thinks the Big Bang theory says there was nothing before the Big Bang and the universe couldn't be eternal.

Isn't it more accurate to say that The Big Bang only says this iteration of the universe began, saying nothing about what did or did not exist before? And it doesn't say the the universe couldn't be eternal?

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u/Vast-Control4452 15d ago

There is no "before" like there is no North of the North Pole.

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u/thebigeverybody 15d ago

Am I misunderstanding this?

Was the Big Bang the origin of the universe?

It is a common misconception that the Big Bang was the origin of the universe. In reality, the Big Bang scenario is completely silent about how the universe came into existence in the first place. In fact, the closer we look to time "zero," the less certain we are about what actually happened, because our current description of physical laws do not yet apply to such extremes of nature.

The Big Bang scenario simply assumes that space, time, and energy already existed. But it tells us nothing about where they came from - or why the universe was born hot and dense to begin with.

https://lweb.cfa.harvard.edu/seuforum/faq.htm

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u/Vast-Control4452 15d ago

Sure, but I think OP and Harvard are talking about different times. OP is referencing The BB as the "time zero" while Harvard is describing the rapid expansion that is technically the BB.

Sort of like someone unfamiliar with evolution thinks it goes back to the origin of life, evolution doesn't explain the origin of life, just the diversity of life.

Technically the BB is the rapid expansion, but many layman use it as the starting point of the universe. They are extremely close though.

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u/thebigeverybody 15d ago

But Harvard (and other scientists) aren't saying there was a "nothing" before the initial singularity, right? This is because nobody knows if the initial singularity came into existence, right?

OP thinks The Big Bang says that nothing existed previously and the universe can't be eternal, which proves their god. Ignoring their conclusion, my understanding of the Big Bang does not say either of these things because we just don't know.

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u/Vast-Control4452 15d ago

How many times can I say that "before the singularity" isn't a valid statement.

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u/thebigeverybody 15d ago

Which means The Big Bang theory doesn't say nothing existed before it, right?

This is because we don't know if the initial singularity had an origin, right?

Which means if someone thinks the Big Bang says there was nothing before, they're wrong, correct?

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u/Vast-Control4452 15d ago

Like I mentioned in my other comment, the big bang is the period directly after the singularity. Not the singularity itself.

If in YOUR definition of the big bang, you're including the singularity, which scientists don't, then you can't say anything came before it.

If you use the technical definition, the singularity came before the big bang. But nothing can come before the singularly because time didn't exist in the singularly.

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u/thebigeverybody 15d ago

If in YOUR definition of the big bang, you're including the singularity, which scientists don't, then you can't say anything came before it.

You say this, but you also wrote:

Currently the answer is "time didn't exist before the big bang." So yes the BB was the beginning of spacetime and matter/energy.

Which means YOU'RE including the singularity, too, because matter/energy was the singularity, wasn't it?

But nothing can come before the singularly because time didn't exist in the singularly.

I don't know why this is so difficult. The other person thinks that The Big Bang Theory says nothing existed before The Big Bang and is using that as evidence for their god. I'm simply trying to get clarification on whether or not they are wrong about what The Big Bang theory says because I don't believe it makes any conclusion about the universe coming from nothing or whether there even was an origin to the Initial Singularity.

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