Question How do we know that the universe started with a Big Bang?

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I really hope you're not referring to my comments because I don't consider them as answers.


No offense but, this sounds like "accept it or not, that's how it is now and you better don't challenge that"

But then, why disapproving or defending something that was not proved in the first place? :)

There are few candidate theories you surely know about that could evolve to answer the missing "creational" portion of the BB or even give a complete new theory at some point, candidates listed for:
Theory of everything - Wikipedia
The universe whatever that may be is a game of energy in one format or another.
since we see an expanding area with views beyond our vision it had a start point.
Winding the clock back put at least what we see all back to a start location so i would say the big bang is on solid ground as a theory.

What creates the energy and what is the mechanism for a BB is the real subject of what the universe is and how it came to be.
Right now we see an explosion but have no clue how that explosion came to be or how the tnt came to be for the explosion.

IMO the universe is endless fluctuation that is the cause for energy building in regions and reason for BB's when energy levels get to high in one region or BB's collide.
Fluctuation right now creates sub atomic particles then promptly destroys them.
Before fluctuation became balanced it probably created sub atomic particles and didn't destroy them.
That gives us a start point to creating everything and a new perspective on what the true universe might be.
Then the question of what is fluctuation?
If we have an area of endless void space that has nothing it it but consumes space does it have potential energy? That could be what fluctuation is, just a balance of potential energy.

To have any format of a universe we need a deeper understanding than expansion from a 0 point of space for no reason.
That is the current BB theory.

Our BB might simply be 1 expanding BB in forever with endless other BB's in every format possible from giant black hole to compression to expansion and sub BB areas with not enough energy accumulated to do anything yet.
 

IG2007

"Don't criticize what you can't understand..."
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I think because the answer is blowing in the wind.
They had a song like that about how many trees etc.
"How many roads must a man walk down, before you call him a man?
How many seas must the white dove sail, before she sleeps in the sand?
How many times must the cannon balls fly, before they are forever banned?
The answer, my friend, is blowing in the wind,
The answer is blowing in the wind."


The song was originally sung and written by Sir Bob Dylan, he received the Nobel Prize for Literature in 2016 for his lyrics. :)
What creates the energy and what is the mechanism for a BB is the real subject of what the universe is and how it came to be.
Right now we see an explosion but have no clue how that explosion came to be or how the tnt came to be for the explosion.
I just explained it in #12.
 

Catastrophe

The devil is in the detail
Two distant objects (inhabited points) each moving away from a central point in opposite directions each at velocity c, have a relative velocity c, not 2c.
Likewise if each moves away from a central point at 0.8c, their relative velocity is still c, not 1.6c.

Cat :)
 
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IG2007

"Don't criticize what you can't understand..."
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Two distant objects (inhabited points) each moving away from a central point in opposite directions each at velocity c, have a relative velocity c, not 2c.
Likewise if each moves away from a central point at 0.8c, their relative velocity is still c, not 1.6c.

Cat :)
Um, Cat, I don't exactly understand what you mean to say. Sometimes your genius is above even my own understanding. Can you please explain it? :)
 
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Catastrophe

The devil is in the detail
IG, you know that the relative velocity of two objects travelling away from each other at velocity c (relative to fixed external point) is c and not 2c (Einstein).
It was my fault to have overcomplicated the statement in post #28.

Cat :)
 
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I did not say speed faster than light exists.

What I meant is that 2 "distant" points in space move from each other FTL, that's why light may not reach.

However since space doesn't expand at constant rate saying light will never reach is moot point, because it applies only from the point in time when 2 points reached 50% of light speed and onward.

For example, given 2 distant points A and B, and central point C:
A - C - B

If points A and B each happens to move away from point C at 60% of the speed of light then point B moves away from point A at 120% the speed of light which is faster than light, so light from point A may never reach point B.

For all time until points A and B were expanding up to (but not including) 50% speed of light, the light will eventually reach both points.
The speed of light at each point will measure 'c' locally. So think it and time. A moves away from both C and B. Light as time will not keep up with that constant of distancing between A and C, and B. Regarding C and B, A appears to be slowing down in time from the growing stretch between A and C, and B. And the growing stretch between C and B, and between A and B. Time appears to be stretching out.

As far as C and B are concerned, there is a growing distance between real space, real time, A and relative time A. There is now a stretched out in time ghost A between A and C, and a different even more stretched out in time ghost A between A and B. And vice-versa regarding B and C, and B and A. Two ghosts of A, one slowed down in time between A and C, one slowed down even more in time between A and B. If all three could last long enough, the ghosts would disappear into the collapsed horizon of the BB. in other words, all the ghosts slowed down so much in time as to having gone into time reversal regarding each other. Over the course of separations there will have been curvature and accumulations of light-times. More, and ever more, accumulations. Until a collapse of complexity into that horizon and coming from that horizon to very long lived A and C and B. Meanwhile, what form of non-local Universe exists between real space, real time, A, C, and B., each of which measures the speed of light locally to be 'c'? A mighty dark real Universe BETWEEN reals! Each observes a relative time universe. A universe in time relative to A: A universe in time relative to C: A universe in time relative to B. Not one universe observed by the three (A, C, And B), but three (relative time) universes.
 
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Catastrophe

The devil is in the detail
Considering what we know of the Universe is a tiny part of the <5% (matter that we *know*) and that we know virtually nothing of the other 95% dark matter and dark energy (for example, are there any life forms there) is it not a fair analogy to consider our species as inhabiting a tiny hamlet in St Helena with no knowledge of the rest of this planet and very little beyond?

And then our inhabitants ask how did we get in this ocean?

Cat :)

P.S. "St. Helena island, part of the British Overseas Territory . . . . . . . . . is a remote volcanic outpost in the South Atlantic Ocean". Wiki.
Area approx. 47 sq miles population from census 4,257 in 2008.[
 
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The speed of light at each point will measure 'c' locally. So think it and time. A moves away from both C and B. Light as time will not keep up with that constant of distancing between A and C, and B. Regarding C and B, A appears to be slowing down in time from the growing stretch between A and C, and B. And the growing stretch between C and B, and between A and B. Time appears to be stretching out.

As far as C and B are concerned, there is a growing distance between real space, real time, A and relative time A. There is now a stretched out in time ghost A between A and C, and a different even more stretched out in time ghost A between A and B. And vice-versa regarding B and C, and B and A. Two ghosts of A, one slowed down in time between A and C, one slowed down even more in time between A and B. If all three could last long enough, the ghosts would disappear into the collapsed horizon of the BB. in other words, all the ghosts slowed down so much in time as to having gone into time reversal regarding each other. Over the course of separations there will have been curvature and accumulations of light-times. More, and ever more, accumulations. Until a collapse of complexity into that horizon and coming from that horizon to very long lived A and C and B. Meanwhile, what form of non-local Universe exists between real space, real time, A, C, and B., each of which measures the speed of light locally to be 'c'? A mighty dark real Universe BETWEEN reals! Each observes a relative time universe. A universe in time relative to A: A universe in time relative to C: A universe in time relative to B. Not one universe observed by the three (A, C, And B), but three (relative time) universes.
What if the guts of a big bang was already moving at C before it expanded?
Sure would make things complicated for time/space/size dilation and trying to figure our anything relative takes on an entire new meaning.

Drink to much coffee and that's the crazy thoughts that come to mind :)
 
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Two distant objects (inhabited points) each moving away from a central point in opposite directions each at velocity c, have a relative velocity c, not 2c.
Likewise if each moves away from a central point at 0.8c, their relative velocity is still c, not 1.6c.
I'm sorry but that is wrong in respect to the problem.

In my example from previous post #25 we have 2 distant points A and B moving away from central point C,
each moving at constant speed of 60% of the speed of light.

A <-- C --> B

Formula to calculate relative velocity for this problem is as follows:
Vab = Va - (- Vb)

Where:
Vab is relative velocity of point A in respect to point B
Va is velocity of object A
Vb is velocity of object B

So the calculation is as follows:
Vab = Va - (- Vb)
Vab = 0.6 - (- 0.6)
Vab = 0.6 + 0.6
Vab = 1.2
Vab = 120% the speed of light

That means point A and B move away from each other 1.2x the speed of light, which is faster than the speed of light.
Which explains why light may never reach either points as soon as 50% speed of light is exceeded.

This formula is shortened version because the degree of central point C is 180 relative to points A and B.
Point C is not relevant here because C is not the observer but rather a reference point, the actual observers are points A and B here.

Why A and B?
Because the problem was whether light of these points can or cannot reach each other, which depends on individual velocities of both points. (it doesn't have to be constant speed)

We can say one point is moving at 40% the speed of light and other one is moving 65% the speed of light and the answer is again the same, FTL obviously.

If points A and B move away from each other at different angle then the calculation should take that into account.

The speed of light at each point will measure 'c' locally.
No 'c' is not relevant because we are not observers between 2 points, but rather trying to figure out whether light might or might not reach from one point to another point if they are moving away from each other faster than light.

You said such thing is not possible but that really depends on whether FTL is taking place or not.

If they move away less than the speed of light the light will eventually reach at some point in time.
if they move away faster then the speed of light then light may not reach.
 
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IMO, light can only propagate at one speed - c. I think all see this fact. So, regardless of the ships’ speeds, their light moves toward one another, or a central observer at c.

If the ships’ relative speed > c, then the light can’t reach one another. It may help to recall the relativistic Doppler term, (1 - v/c), that reveals the redshift for frequency. Thus once v=c, then the frequency becomes 0.
 
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I'm sorry but that is wrong in respect to the problem.

In my example from previous post #25 we have 2 distant points A and B moving away from central point C,
each moving at constant speed of 60% of the speed of light.

A <-- C --> B

Formula to calculate relative velocity for this problem is as follows:
Vab = Va - (- Vb)

Where:
Vab is relative velocity of point A in respect to point B
Va is velocity of object A
Vb is velocity of object B

So the calculation is as follows:
Vab = Va - (- Vb)
Vab = 0.6 - (- 0.6)
Vab = 0.6 + 0.6
Vab = 1.2
Vab = 120% the speed of light

That means point A and B move away from each other 1.2x the speed of light, which is faster than the speed of light.
Which explains why light may never reach either points as soon as 50% speed of light is exceeded.

This formula is shortened version because the degree of central point C is 180 relative to points A and B.
Point C is not relevant here because C is not the observer but rather a reference point, the actual observers are points A and B here.

Why A and B?
Because the problem was whether light of these points can or cannot reach each other, which depends on individual velocities of both points. (it doesn't have to be constant speed)

We can say one point is moving at 40% the speed of light and other one is moving 65% the speed of light and the answer is again the same, FTL obviously.

If points A and B move away from each other at different angle then the calculation should take that into account.


No 'c' is not relevant because we are not observers between 2 points, but rather trying to figure out whether light might or might not reach from one point to another point if they are moving away from each other faster than light.

You said such thing is not possible but that really depends on whether FTL is taking place or not.

If they move away less than the speed of light the light will eventually reach at some point in time.
if they move away faster then the speed of light then light may not reach.
A car drives away from you at 60 miles an hour. It is traveling faster than the speed of light. How? Why? The real time traveler is a micro-micro-second ahead of the relative time traveler you observe driving away from you. Separating from both you and his ghost (you observe) in space and time. Be careful when he turns around and comes at you, he will appear to you to be accelerating toward you even though he is maintaining a speed of 60 miles per hour. How? Why? He, the traveler, is not only closing with you but closing with the ghost between him and you the only thing of him you observe. He will close and merge with that ghost only at the point he runs over you.
 
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IMO, light can only propagate at one speed - c. I think all see this fact
Correct but the speed of light is not an issue here because the speed of light is constant value, and as such it does not affect the result of calculation.

The problem is whether light from point A can or cannot reach point B and vice versa, and what is the relative speed of points A and B relative to each other, not C.

So, regardless of the ships’ speeds, their light moves toward one another, or a central observer at c.
Yes it does but again the target isn't point C but rather A -> B or B -> A

You can move point C in either direction toward either A or B and it won't change the result because it's only purpose is to highlight that A and B travel away from each other rather than one toward other.

Notice that either point A or point B is moving in negative direction!

Code:
             +y
              -
              -
-x ----A----- C -------B--- +x
              -
              -
              -y
The light itself of either points A and B indeed does travel one toward other but we don't calculate relative speed of "light A" and "light B", but rather relative speed of points, the speed of either "lights" is constant

If point A moves faster than point B from central point C then this only means light from point A will reach sooner to point C while light from point B will be "late", however point C is not a target here therefore speed difference doesn't matter at all.

Whether light will reach by passing C depends on velocity of both points.

A car drives away from you at 60 miles an hour. It is traveling faster than the speed of light.
I did not say that nor did I mention miles per hour.

The car isn't approaching me but rather going in completely opposite direction of my own route that I took, I'm not sitting in the center waiting for the car to approach me but rather moving away from some imaginary central point.
If I walk 10 mph and the car moves at 60 mph then we're moving away from each other 70 mph.
 
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The problem is whether light from point A can or cannot reach point B and vice versa, and what is the relative speed of points A and B relative to each other, not C.
Agreed, which is why I ignored C and referenced the relative speed of the ships only (ships' - plural possessive).

You can move point C in either direction toward either A or B and it won't change the result because it's only purpose is to highlight that A and B travel away from each other rather than one toward other.
It's a bit ironic that C could serve as a stepping stone to help eschew obfuscation only to create more confusion. :)

Whether light will reach by passing C depends on velocity of both points.
C could get a signal from A, then relay the signal to B, so communication via the C relay should work. But what I see is that relativistic redshift will be too great for any direct communication between A and B. I think this is right.
 
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t's a bit ironic that C could serve as a stepping stone to help eschew obfuscation only to create more confusion. :)
lol, I'm sorry for confusion :(

But what I see is that relativistic redshift will be too great for any direct communication between A and B. I think this is right.
Exactly this!

Because universe expansion is accelerating, it's therefore safe to say that whether light will reach some far reaches of the galaxy depends not on the speed of light but rather on relative speed of 2 points in space.

Expansion of arbitrary points may exceed the speed of light many times over but magnitude depends only on sample points that we choose. it may be less than speed of light it may be much much faster.
 
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Because universe expansion is accelerating, it's therefore safe to say that whether light will reach some far reaches of the galaxy depends not on the speed of light but rather on relative speed of 2 points in space.
Yes, though c determines vanishing points, of course.

The expansion is, apparently, uniform and is flowing outward, "outward" just means spacetime is enlarging with time. It may help others to see that this flow is uniform and it's known as the Hubble Flow. The clocks floating, if you will, in the HF will essentially tick at the same rate as our clocks (ignoring local gravity, etc.) even those a billion lyrs. from us. Seeing it as a flow is an easy way, for me at least, to see how the term "comoving" is used, and often. The flow will move inertial frames at speeds relative to one another depending on the flow, which is defined by the expansion rate.

Once the radial regions of extreme distances are moving (flowing) a little past the speed of light away from us due to the expansion, any light will be lost to us. Thus, our chance of seeing more of the universe fades from us with time. I guess we will just to have work with the 2 trillion galaxies we can see. ;)
 
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Catastrophe

The devil is in the detail
How do we know that the universe started with a Big Bang?

To come back on topic, have we in any way improved on the answer in post #13?
My apologies for being as guilty as any in digressing.

Cat :)
 
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@Catastrophe

I guess if govern ourselves according to "a map is not the territory" then that not only rules out any possible conclusions but it also defeats all theories we know about including the theory of big bang.

Because big bang is based on our observation of observable universe (the map) rather than having the entry universe somewhere on the table (territory) where one could perform some experiments.

Or is there something else you wanted to point out?
 

Catastrophe

The devil is in the detail
Question: How do we know that the universe started with a Big Bang?

Answer: We don't.

There are other possibilities e.g., the "BB" (albeit derogatory as it was originally intended) may not have been The beginning, but a nexus between two 'phases' of the Universe. A singularity seems to require "pushing an infinite mass up a very steep hill" if you get my meaning? Cyclic makes more sense (Occam's Razor).
Whatever, if there is more than one alternative, neither is the answer. At least that is my understanding of the English language. (Vide excluded third).

Cat :)
 
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Question: How do we know that the universe started with a Big Bang?

Answer: We don't.
The problem is in the word “started” since BBT doesn’t argue how it started. It is a theory of today we rewind in time to get to as far as we can take it, but not beyond that.

It’s like if Doubleday didn’t invent baseball that baseball would somehow vanish?

A singularity seems to require "pushing an infinite mass up a very steep hill" if you get my meaning?
Nicely put! I will want to use this!😀

Cyclic makes more sense (Occam's Razor).
But cyclical requires more time requirements, IMO.
 
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Question: How do we know that the universe started with a Big Bang?

Answer: We don't.

There are other possibilities e.g., the "BB" (albeit derogatory as it was originally intended) may not have been The beginning, but a nexus between two 'phases' of the Universe. A singularity seems to require "pushing an infinite mass up a very steep hill" if you get my meaning? Cyclic makes more sense (Occam's Razor).
Whatever, if there is more than one alternative, neither is the answer. At least that is my understanding of the English language. (Vide excluded third).

Cat :)
Could be a few simple reasons for a big bang.
When 2 meet an energy level that cant exist in normal space happens and spawns a BB.
Singularity doesn't exist and when a BB meets a BB black hole time gets crunched releasing it's energy.
A very odd particle is created by fluctuation that is everything, happens every Xzillion years.

Could be a pretty shallow hill :)
 

Catastrophe

The devil is in the detail
"Could be a few simple reasons for a big bang."

Well, sorry, I can see none. Just my personal opinion :)

Question: How do we know that the universe started with a Big Bang?
Answer: We don't.

Either it did or it didn't. (Vide excluded third). My opinion is didn't.

Cat :)
 
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Cheez, can't anyone else see it yet? Physicists at the Large Hadron Collider are working their way toward the Big Bang event by working their way toward the Planck level horizon. Not as creationism but as constancy. What happens, happens at the Planck level of the universe and goes from there. The Big Bang is only a representation in universes at large. The infinity of hot blue-white holes, of quantum fluctuations, at the Planck level being represented at the level of relativity as Big Bang event. Relativity does not deal in infinite / infinitesimal / infinity of.... It does not deal in non-locality non-relativity. It deals strictly in the relative, the local relative, the local finite, the local finite universe. Relativity cannot work with quantum fluctuations at the collapsed horizon of the Planck level of universe. So it works with a representative of its own, the Big Bang [up and out] at the far horizon of the collapse of infinite / infinity (it is impossible to observe "infinite" / "infinity", so it must collapse to and into horizon (though the infinite still has representations and influences in and regarding the finite... from that collapsed horizon in and into the finite)). But then they make a mistake, a titanic mistake, and start seeing "creationism" in it (turning science into a religion.... and themselves into priests of that religion).
 
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But then they make a mistake, a titanic mistake, and start seeing "creationism" in it (
turning science into a religion.... and themselves into priests of that religion)
lmao :D

Well they name it "God particle", couldn't the name be more scientific? ¯\_(ツ)_/¯

It makes one think that the definition of the big bang is un professional and I guess we'll never know for sure.
 
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