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There are two parts to your question. First, why can we see things "46 billion light years away" if the Universe is only about 13.8 billion years old? Because the Universe is expanding. How far does a photon travel in 13.8 billion years in an expanding Universe? It depends on the rate of expansion. I'll give a simplified example to illustrate the point: ...


2

When they say the universe was the size of a baseball about a billion billion billion billionth of a second after the big bang, does that means the observable universe was the size of a baseball, or does it mean the entire universe? In the past, the answer would have been the entire universe. Big bang cosmology is all about the expanding universe starting ...


-1

In my Physics Class we had to look into possible areas where Dark Matter could be "hiding". Where is all the dark matter? Actually, I think it's hiding in plain sight. If you've read up on relativity I think you can work it out. See Einstein's Leyden Address where he described a gravitational field as space which was "neither homogeneous nor isotropic", and ...


-7

There are two main misconceptions about dark matter. One is that dark matter is a clump of stuff traveling with the matter. The other is that matter does not interact with dark matter. Dark matter fills 'empty' space. 'Empty' space has mass. Spacetime has mass. Dark matter is displaced by matter. The Milky Way moves through and curves spacetime. The ...


2

The discrepancy between the predicted big bang nucleosynthetic abundance of Lithium 7 and the measured value can be summarised as follows. If we take what we know about the the baryonic mass density of the universe and the Hubble constant, we get a self-consistent picture between the cosmic microwave background, observations of galaxy recession etc. and the ...


10

There are several reasons to believe that dark matter is a particle. The most widely accepted alternative explanations for the different phenomena that led us to conjecture dark matter in the first place, can collectively be labeled "we don't understand gravity well enough". But no matter what, the effects of dark matter are sort of "localized". The ...


1

The balloon analogy imagines the universe as a 2D surface expanding around a central point as it moves through a 3rd dimension of time. This may be the origin of confusion as in reality there is no 2D surface of expansion, like a wave front, but rather an expansion of 3D spacetime, wherein every point in space quite literally is its own central point from ...


-2

Your question may presuppose that the Universe had a beginning in its own past. If we apply the logic of our experience and perception that we live with in space/time, this may seem like a reasonable inference. But just as complex systems may need more than knowledge of the sum of their constituents to be understandable, broader knowledge of the Universe ...


4

I'll answer your question with an analogy. Imagine a really small balloon, so small that it occupies a point. Now, imagine that the balloon is expanding uniformly outward from that point. Note that that central point is not part of the balloon. It's the same idea as to what happened with the BB. In this analogy, the universe is the surface of the balloon. ...


1

it must have started from a single point This is a common misconception popularized buy the media. Imagine this grid: Imagine each square getting larger. If you think about it, you will see that each point on the grid is expanding. The grid is the universe. Each point on the universe is its own "singularity".


3

The link Qmechanic has suggested is a duplicate and does discuss the question you ask. However there is another point that is worth making here. In general relativity we describe the universe as a manifold equipped with a metric, and the metric is the FLRW metric that desciribes expanding spacetime. However the FLRW metric does not include the point(s) at ...


-2

Yes! The center of the universe is the one place where time is "correct". That is, not influenced by extraneous gravitational fields. So by 'correct' I mean where time is running faster (or no slower) than anywhere else. It is left as an exercise to the reader how this location might be found.


2

The problem with this question is in the premise that where dynamical chaos is applicable nothing is predictable or can be extrapolated to the past. This is a wrong premise. Take this demonstration of a chaotic system. Note that it is computer simulation and of course it fits real data. Computer simulations are time symmetric, so the individual points can ...


0

Regular matter and energy, through, gravity tends to slow the expansion. I do not know of any theory that treats it or any other "retarding" force as friction. However there is evidence that another stuff in the universe, different from regular matter and energy (called dark energy) is actually accelerating the expansion, rather than slowing it (also, ...


1

Gravity is the retarding force. I don't think that non-conservative forces are customarily considered.


2

You seem to be misunderstanding the depth of the prediction we've made of the past in saying that the Big Bang happened. You do make a very valid point that chaotic systems even with as few elements as the solar system are practically impossible to past-predict (I'm going to start using the word "postdict"1 because it makes me feel better). I'm more than ...


2

I'm not sure if that touches your question, but the universe is thought to be non-chaotic in the long term behaviour because of some anisotropy in the initial conditions (at least this is the general opinion). I watched a cool vid about that a couple of days ago. The point for which I agree with you, is that if looking at a certain situation, in general one ...


-1

There is a concept known as entelechia, which basically means an idea so complicated and so full of border cases that no useful ideas can be obtained from it. One entelechia is the concepto of god, a súper being who created everything in just 6 days and who needs your money. And the fossil record was put there by good just to test your faith. Eventually it ...



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