How does light catch up and pass up when looking in to space

[nammynake]

alock said:

Simplify the problem to 1 dimension. You and a friend are at opposite ends of a straight road. The council come and dig up the straight road and build a twisty road instead. Neither you or your friend have moved and yet you are now twice as far apart in this 1 dimensional world.

In 3 dimensions, the big bang created the space between objects. They didn't have to move apart to end up further apart

Don't get your example. Wouldn't a twisty road be 2d by definition?

[xRIEx]

nammynake said:

alock said:

Simplify the problem to 1 dimension. You and a friend are at opposite ends of a straight road. The council come and dig up the straight road and build a twisty road instead. Neither you or your friend have moved and yet you are now twice as far apart in this 1 dimensional world.

In 3 dimensions, the big bang created the space between objects. They didn't have to move apart to end up further apart

Don't get your example. Wouldn't a twisty road be 2d by definition?

I think that's the idea - the road is in two dimensions, but the observers can only perceive one dimension. The example I've heard before is of dots on a balloon: as the balloon is inflated, all of the dots move away from each other in many directions, as 2-dimensional surface of the balloon is expanding through three dimensions.

In our universe, we can perceive three dimensions, but the universe is expanding through 4 (or more) dimensions.

[Laplace]

Mr Gear said:

If you fire a satellite out of orbit, is IT moving away from earth, or is the earth moving away from it?

It's moving away from Earth.
The example isn't symmetrical as the satellite has undergone acceleration.

[R300will]

Laplace said:

Mr Gear said:

If you fire a satellite out of orbit, is IT moving away from earth, or is the earth moving away from it?

It's moving away from Earth.
The example isn't symmetrical as the satellite has undergone acceleration.

Actually it is both, however the earth experiences such a small force of acceleration compared to its overall weight that it doesn't move. Its acceleration as a result form the satellite is cancelled by other planets in the solar system pulling on it as well as the sun of course.

[alock]

nammynake said:

alock said:

Simplify the problem to 1 dimension. You and a friend are at opposite ends of a straight road. The council come and dig up the straight road and build a twisty road instead. Neither you or your friend have moved and yet you are now twice as far apart in this 1 dimensional world.

In 3 dimensions, the big bang created the space between objects. They didn't have to move apart to end up further apart

Don't get your example. Wouldn't a twisty road be 2d by definition?

You move forwards and backwards along a theoretical road so it's 1D. You can move a little bit side-to-side on a real road, but then you can jump up-and-down as well.

[AJI]

After another episode of Stargazing last night and also this article in the news;
http://www.bbc.co.uk/news/science-environment-2564...

I wondered if I could ask if it is possible for one to locate where the big bang singularity would have been in our universe when time = zero?

Is it possible to know the direction that each galaxy is moving away from each other galaxy and then reverse these lines to point back to an origin?

[Alapeno]

I was always under the impression everything was expanding in equal directions so it would be impossible to tell? As in the space between everything is expanding rather than from a point.

May be wrong though, so someone more knowledgable may be along shortly to explain.

[Laplace]

AJI said:

After another episode of Stargazing last night and also this article in the news;
http://www.bbc.co.uk/news/science-environment-2564...

I wondered if I could ask if it is possible for one to locate where the big bang singularity would have been in our universe when time = zero?

Is it possible to know the direction that each galaxy is moving away from each other galaxy and then reverse these lines to point back to an origin?

No because the universe is homogeneous and each galaxies trajectory would appear the same from their relative perspectives.

Also, to think that tracing their trajectories back would lead to one point is thinking of the universe in a "standard" three dimensional way, which is wrong. There is no centre of the universe much like there is no centre on the surface of a ball.

[maffski]

AJI said:

I wondered if I could ask if it is possible for one to locate where the big bang singularity would have been in our universe when time = zero?

Is it possible to know the direction that each galaxy is moving away from each other galaxy and then reverse these lines to point back to an origin?

It's actually very easy. It happened here. And there. And everywhere. Our universe is the expanding remnant of the big bang.

R300will said:

What if our universe was simply an atom of another universe

There is a theory that suggests our universe is a bubble, in the foam of a crashing wave caused by colliding fronts in some kind of metaverse. There's also one that claims it was sneezed out by The Great Green Arkleseizure. You pays your money and you takes your choice.

[mrmr96]

AJI said:

I wondered if I could ask if it is possible for one to locate where the big bang singularity would have been in our universe when time = zero?

Is it possible to know the direction that each galaxy is moving away from each other galaxy and then reverse these lines to point back to an origin?

The fact that you're asking this question demostrates that you don't understand what happened at the big bang. (That in iteself is very understandable as it's a very weird topic which human brains are not designed to cope with.)

An incorrect view is to think about a big black empty nothingness, i.e. space in 3 dimensions with nothing in it, but with time passing. Then at some instant there is a bright speck appears and begins to expand over time into the pre-existing space. If this were true, which it isn't, then you would indeed to able to ask where the big bang happenend, because you could measure its coordinates within the previously existing blank space. (Although if that space were empty and infinite then it wouldn't really have any relevance.)

What actually happened (according to my latest understanding) is that before the big bang there was nothing. In fact, there is actually no such thing as "before the big bang" because time only started existing at the same time as space started existing.

There was a single point which has expanded into what we now call our universe. It is not expanding INTO anything. This is a REALLY REALLY hard concept. We like to think of watching a balloon expand, and we know it's expanding into the space around the balloon. So we could choose a point near the surface of the balloon and watch the balloon expand into/through that point. So that a point which was once outside is now inside. But that isn't what we think is happening. There is nothing outside the universe, the universe is everything.

Maybe a better way to think about it is to think that distances between things are increasing, but the things themselves are not moving? There's just more "units of space" between them? Does that help?

In answer to tracking the origin, as the guy above said, it's everywhere. That's kind of the point. If you were to try to track the path of objects in the expanding universe you'd not be able to. Because measured from Earth, everything is moving away. So it looks like (from our point of view) that we are at the centre. But measure from another galaxy, and similarly things are moving away so IT looks like the centre.

Think about my example above, maybe consider things not moving but rather the distance between them increasing. There is no "centre" of expansion in that illustration.

Let me know if that helps.

[AJI]

mrmr96 said:

The fact that you're asking this question demostrates that you don't understand what happened at the big bang.

You are quite right, I freely hold my hands up and admit I don't understand it.

[mrmr96]

AJI said:

mrmr96 said:

The fact that you're asking this question demostrates that you don't understand what happened at the big bang.

You are quite right, I freely hold my hands up and admit I don't understand it.

Ok, to be fair no one really understands it. I probably should have said "you don't understand the lay-terms explaination".
It's a really hard concept to understand that a single dot became everything and everywhere, and that it's not expanding "into" anything. Not sure if I fully get it either to be honest, I'm just repeating things I've read on the subject.

[Laplace]

mrmr96 said:

What actually happened (according to my latest understanding) is that before the big bang there was nothing. In fact, there is actually no such thing as "before the big bang" because time only started existing at the same time as space started existing.

And by that we can say the universe has always existed as there was never a time that it didn't.

[steve singh]

Laplace said:

mrmr96 said:

What actually happened (according to my latest understanding) is that before the big bang there was nothing. In fact, there is actually no such thing as "before the big bang" because time only started existing at the same time as space started existing.

And by that we can say the universe has always existed as there was never a time that it didn't.

Science is about a best fit model - Hawking's conclusion was a convenient way to close of the debate given the prevailing information.

If you read into hawking's a bit more and explore what is meant by reality, simulation theory etc. - you end up just thinking wow, we know a lot but then again know nothing!

For all we know we're in an Alien game of 'The Sims' !

[steve singh]

Also if there was nothing before the big bang, how can the prevailing laws of nature be the very start of a universe which is then said to create the laws of gravity.

If there was nothing before the big bang, then there should no laws of physics / nature?

[Laplace]

steve singh said:

Also if there was nothing before the big bang, how can the prevailing laws of nature be the very start of a universe which is then said to create the laws of gravity.

If there was nothing before the big bang, then there should no laws of physics / nature?

Events "before the big bang" are of no consequence, they can neither be observed nor measured and at the point of singularity the laws of physics as we know them no longer exist. The evolution of our universe and its laws do not depend on anything prior.

The Grand Design by Hawking and A Universe From Nothing by Krauss are worthwhile reads.

[iacabu]

Forgive me that this is probably a dumb question...could the big bang theory be wrong? I know there is evidence to support it, but are they just finding a way to link that evidence to something that is completely made up and didn't actually happen at all?

I just don't see how something came from nothing.

With reference to a couple of posts on the previous page leading to the scale of the universe link (of which there is now a 2nd version) I found an interesting page while procrastinating at work...

http://www.xiac.com/Universe/universe.html

Assuming it's right, of course

[Einion Yrth]

iacabu said:

Forgive me that this is probably a dumb question...could the big bang theory be wrong? I know there is evidence to support it, but are they just finding a way to link that evidence to something that is completely made up and didn't actually happen at all?

I just don't see how something came from nothing.

With reference to a couple of posts on the previous page leading to the scale of the universe link (of which there is now a 2nd version) I found an interesting page while procrastinating at work...

http://www.xiac.com/Universe/universe.html

Assuming it's right, of course

Everything is, observably, receding from everything else. As a thought experiment reverse the arrow of time, everything is now approaching everything else. What happens next?

[AJI]

iacabu said:

Forgive me that this is probably a dumb question...could the big bang theory be wrong?

Well yes, it is a theory, waiting for something to 'trump' it in effect.

At the moment I accept that TBBT fits observations better than other theories describing events and also at the same time with it being a theory, in science, it is something that is there for development or dismantlement etc. depending on what you are working towards within your scientific field/project etc.


I follow that there was a 'battle' between matter and anti-matter and this battle can now be replicated on a small scale at the likes of CERN, and these observations can support TBBT and why there is so much 'empty' space.


My questions in this thread have mainly been towards the speed of light issue. I just can't get my head around it.
I follow the fact that it is a relative thing etc, and this can lead to some strange occurrences, but its the 'inflation' vs 'expansion' part that I struggle with.

Edited by AJI on Friday 17th January 13:17

[andy_s]

ash73 said:

As I understand it, distant galaxies are still moving away from us faster than c, not because they are moving faster than c, but because the space in-between us is expanding faster.

A bit like two cars driving away from each other at 60, when observed from one car it could look as if the observer was still and the other car was doing 120? No one breaks the speed limit but it looks as if car two is doing double?