The Great Universe Debate

[Great Boos Up]

The faster you travel the more time slows down for you relative to others. Everybody uses GPS right. Well the satellite time has to be corrected or we'd all drive into the sea.

[CollinsLCFC]

21 hours ago, joachim1965 said:

Time travel into the past may prove to be a little bit more problematic.

The Grandfather Paradox is interesting on backwards time travel.

 

If you were to travel back in time and kill your Grandfather before the conception of your Mum/Dad, you would never have been born to subsequently travel back in time in the first place.

[Izzy]

3 minutes ago, Great Boos Up said:

The faster you travel the more time slows down for you relative to others. Everybody uses GPS right. Well the satellite time has to be corrected or we'd all drive into the sea.

Doesn't it just mean that you use less time rather than time slowing down? (or is it the same thing? )

 

We wouldn't drive into the sea, we'd just get to our destination in a lesser amount of time wouldn't we?

[Izzy]

6 minutes ago, CollinsLCFC said:

The Grandfather Paradox is interesting on backwards time travel.

 

If you were to travel back in time and kill your Grandfather before the conception of your Mum/Dad, you would never have been born to subsequently travel back in time in the first place.

[Carl the Llama]

12 minutes ago, Great Boos Up said:

The matter and energy within the expanding remain the same, just transferred to other forms and pulled about by force.

Is there any decay?

If so the then expansion would slow?

You'd think so yet the universe is actually speeding up according to the current scientific paradigm.  Then again as recently as the 90's everyone believed that space was primarily occupied by 'space dust' but now we have theories about dark matter and dark energy dominating it so I suppose it's possible that years from now somebody will make a cosmic discovery that completely changes our definition of gravitational theory upon which the conclusion that the universe is expanding at an increasing rate is based. 

 

2 minutes ago, Great Boos Up said:

The faster you travel the more time slows down for you relative to others. Everybody uses GPS right. Well the satellite time has to be corrected or we'd all drive into the sea.

...what?

[Kopfkino]

21 minutes ago, CollinsLCFC said:

The Grandfather Paradox is interesting on backwards time travel.

 

If you were to travel back in time and kill your Grandfather before the conception of your Mum/Dad, you would never have been born to subsequently travel back in time in the first place.

 

Indeed it is, as is Dave Lewis' 1975 essay on the paradoxes of time travel, Novikov's principle and causal loops.

Do like a paradox to think about.

[Captain...]

35 minutes ago, CollinsLCFC said:

The Grandfather Paradox is interesting on backwards time travel.

 

If you were to travel back in time and kill your Grandfather before the conception of your Mum/Dad, you would never have been born to subsequently travel back in time in the first place.

That is way backwards time travel is considered impossible. The only way it could work is if a new reality was created each time you travelled back in time, so the current timeline is fixed as soon as you travel down the time line it branches off and creates a parallel timeline, which you can occupy but the question would be could you return to your original time line  (where nothing has changed) or would traveling forwards in time just propel you up that new timeline to a new future?

[Sampson]

28 minutes ago, Captain... said:

That is way backwards time travel is considered impossible. The only way it could work is if a new reality was created each time you travelled back in time, so the current timeline is fixed as soon as you travel down the time line it branches off and creates a parallel timeline, which you can occupy but the question would be could you return to your original time line  (where nothing has changed) or would traveling forwards in time just propel you up that new timeline to a new future?

Backwards time travel isn't theoretically impossible. It's impossible because we can't travel faster than the speed of light. If you could travel faster than light you would travel back in time.

 

Current consensus seems to be that time isn't linear as we perceive it - everything happens at once. 

 

There's a great video on it here - again, I'd really recommend PBS Spacetime for anyone interested in this stuff it's an incredible YouTube channel.

 

 

[Finnegan]

1 hour ago, Carl the Llama said:

Sampson is bang on, you can have varying levels of infinite.  If the universe is expanding and is infinite then all that means is it's going from a pool of space the size of infinity cubic metres to a pool of space the size of infinity+1 cubic metres then infinity+2 cubic metres and so on.

 

But again, arguing purely semantics because I'm by no means a mathematician - surely if it was always infinite then the numbers you've "added" were always there? 

 

Surely there's no such thing as infinity +1 because infinity +1 was always factored in to infinity by virtue of it being infinity. 

[Carl the Llama]

11 minutes ago, Finnegan said:

But again, arguing purely semantics because I'm by no means a mathematician - surely if it was always infinite then the numbers you've "added" were always there? 

 

Surely there's no such thing as infinity +1 because infinity +1 was always factored in to infinity by virtue of it being infinity. 

I think that's the issue here.  In mathematics infinity doesn't mean what the layman tends to understand it to be much like how in the sciences the term "theory" doesn't quite correlate with the popular definition of the term.  Going back to Sampson's example:  Between 0 and 1 you have 0.1, 0.01, 0.001. 0.0001 etc., there is an infinite number of numbers that fall in the gap between 0 and 1.  A pool of infinity can have defined boundaries, in this case 0<x<1, that don't include everything, in this example that exclusion zone would be the much larger infinite pool of numbers that are either greater than 1 or less than 0.  

Edited 19 October 2017 by Carl the Llama

[leicsmac]

1 hour ago, Izzy Muzzett said:

Doesn't it just mean that you use less time rather than time slowing down? (or is it the same thing? )

 

We wouldn't drive into the sea, we'd just get to our destination in a lesser amount of time wouldn't we?

 

1 hour ago, Carl the Llama said:

...what?

 

 

I that what he means is that GPS satellites require very, very accurately calibrated clocks to provide positioning data that is accurate to the metre (or even less). You're talking in the realms of nanoseconds - and with the satellites out at 20000 km from the Earth, the difference in gravitational effects there, though incredibly minor, means that time passes marginally faster for those satellites than on Earth. As such, they need to be recalibrated every so often.

 

That's one of the proofs of relativistic effects in everyday life.

 

1 hour ago, Carl the Llama said:

You'd think so yet the universe is actually speeding up according to the current scientific paradigm.  Then again as recently as the 90's everyone believed that space was primarily occupied by 'space dust' but now we have theories about dark matter and dark energy dominating it so I suppose it's possible that years from now somebody will make a cosmic discovery that completely changes our definition of gravitational theory upon which the conclusion that the universe is expanding at an increasing rate is based. 

 

 

Yeah, gravitational effects and how and why the Universe is expanding at the speed it is is one of the great mysteries of cosmology. Something like 70% of what contributes to gravitational expansion is unaccounted for - not observed, not even really theorised, we call it dark energy simply because we don't even know if it has physical form in the way garden-variety matter (4.9%) and dark matter (26.8%) do. 

 

Working out what is responsible for that could be crucial in learning about how gravity really works, which in turn could be crucial in long-term spaceflight by being able to manipulate it.

 

14 minutes ago, Sampson said:

Backwards time travel isn't theoretically impossible. It's impossible because we can't travel faster than the speed of light. If you could travel faster than light you would travel back in time.

 

Current consensus seems to be that time isn't linear as we perceive it - everything happens at once. 

 

There's a great video on it here - again, I'd really recommend PBS Spacetime for anyone interested in this stuff it's an incredible YouTube channel.

 

 

Would also recommend this.

[Trav Le Bleu]

Space is big.

 

REALLY BIG!

 

You might think it's a long way to the corner shop to buy your morning paper, but that's peanuts compared to space.

[joachim1965]

2 hours ago, CollinsLCFC said:

The Grandfather Paradox is interesting on backwards time travel.

 

If you were to travel back in time and kill your Grandfather before the conception of your Mum/Dad, you would never have been born to subsequently travel back in time in the first place.

This is where the multiverse theory fits right in, in the instant you kill your grandfather, the universe splits and in one reality he is dead but he will not know it as in this reality he will survive and go on to conceive your father or mother. Search quantum suicide and quantum immortality and the theory is explained in detail.

Mindblowing stuff.

[Izzy]

2 minutes ago, Trav Le Bleu said:

Space is big.

 

REALLY BIG!

 

You might think it's a long way to the corner shop to buy your morning paper, but that's peanuts compared to space.

Come and join me and @Countryfox in the dunce’s corner mate 

[Countryfox]

4 minutes ago, Trav Le Bleu said:

Space is big.

 

REALLY BIG!

 

You might think it's a long way to the corner shop to buy your morning paper, but that's peanuts compared to space.

 

Top posting Trav ...     

[Trav Le Bleu]

We time travel constantly.

 

If you were to use your feet to get to London (i.e., naturally), it would take you one or two days - longer for your average human. But in a plane you can do it in not many minutes, a train in an hour, a car in two. So, essentially, when you arrive, you will have travelled forward in time, 22+ hours ahead of your natural time.

 

[Izzy]

6 minutes ago, Trav Le Bleu said:

We time travel constantly.

 

If you were to use your feet to get to London (i.e., naturally), it would take you one or two days - longer for your average human. But in a plane you can do it in not many minutes, a train in an hour, a car in two. So, essentially, when you arrive, you will have travelled forward in time, 22+ hours ahead of your natural time.

 

What a load of old pony!

 

You’re on the wind up 

[SpacedX]

It is impossible to know for certain if the universe is truly infinite.  The observable universe is definitely finite - and by that we mean the region of the universe which is within 13.80 billion light years of us. The number 13.80 is because it is reckoned to be 13.80 billion years since the Big Bang so any part of the universe that is more than 13.80 billion light years away from us will not be visible or observable since the light from those areas cannot yet have reached us.

Cosmologists postulate that there is a significant part of the universe that lies beyond this observable portion of the universe but it is impossible to conclude that it is infinite.  The standard cosmological assumption is that the universe is homogeneous and isotropic. Partly conjecture but it is borne out in our observable universe - the universe looks the same in all directions and on a large enough scale the universe would appear to be homogeneous.  If the portion of the universe that is not observable is also isotropic and homogenous then it could well be that the universe is truly infinite.

The data that is needed to determine if the universe is infinite or not is to measure the curvature of the universe.  There are three different regimes of curvature - it could have a positive curvature resembling the two dimensional curvature of the surface of a sphere, zero curvature which is like a flat plane, or negative curvature which is like the concave curvature of the surface of a saddle.  If the universe is isotropic and homogenous and the curvature of the universe has a constant positive value then the universe will be finite - just as the surface of a sphere is finite.  On the other hand if the curvature of the universe is a constant of zero or has a constant negative curvature, the universe would be truly infinite.

 

There is no definitive answer at this point but the universe is consistent with having zero curvature. I believe that the standard model of cosmology which successfully accommodates all well measured cosmological information has a defined parameter which is related to the curvature.  If it is less than 1.0 then the universe is positively curved, if it is exactly 1.0 the universe is flat and if the value is greater than 1.0 the universe is negatively curved.  The best measured value is something like 1.0021.  We really don't actually know if the universe is infinite at this point, but since that value is so close to flat, even if the universe is positively curved and finite, you could hypothesise that it would be exponentially bigger than the observable universe.

 

Some theoretical physicists speculate that space-time is curved, so that although inflating, notionally if you travel far enough, you end up where you started.

 

If the Big Bang has happened, there is no way that the Universe, can reach an infinite size, in a finite amount of time.

If the Universe is infinite and has existed an infinite amount of time, then we would have a case of Olbers paradox...

 

http://hyperphysics.phy-astr.gsu.edu/hbase/Astro/olbers.html

 

Edited 19 October 2017 by Line-X

[Buce]

19 minutes ago, Izzy Muzzett said:

Come and join me and @Countryfox in the dunce’s corner mate 

 

How rude!

 

I'll have you know CF is a very educated man:

 

 

 

Edited 19 October 2017 by Buce

[Carl the Llama]

29 minutes ago, Trav Le Bleu said:

We time travel constantly.

 

If you were to use your feet to get to London (i.e., naturally), it would take you one or two days - longer for your average human. But in a plane you can do it in not many minutes, a train in an hour, a car in two. So, essentially, when you arrive, you will have travelled forward in time, 22+ hours ahead of your natural time.

 

I'm time travelling this very moment.  It just so happens to be in a forward direction at a pace I have no control over.

 

Though in a few minutes I'll light a spliff and slow my journey right down.

Edited 19 October 2017 by Carl the Llama

[Buce]

 

Slightly off topic but seems the best place to put it:

 

https://www.theguardian.com/science/2017/oct/19/lunar-cave-discovery-raises-hopes-for-human-colonisation-of-moon

 

 

 

[Great Boos Up]

Amazing to think that the speed of light is actually the only constant we know. Light from the sun takes about 8 minutes to reach your eyes but was formed as excess energy from just one atomic fusion within the sun. That photon may have taken hundreds of years just to break free from the density of the sun so it could travel 8 minutes.

[Great Boos Up]

1 hour ago, Line-X said:

It is impossible to know for certain if the universe is truly infinite.  The observable universe is definitely finite - and by that we mean the region of the universe which is within 13.80 billion light years of us. The number 13.80 is because it is reckoned to be 13.80 billion years since the Big Bang so any part of the universe that is more than 13.80 billion light years away from us will not be visible or observable since the light from those areas cannot yet have reached us.

Cosmologists postulate that there is a significant part of the universe that lies beyond this observable portion of the universe but it is impossible to conclude that it is infinite.  The standard cosmological assumption is that the universe is homogeneous and isotropic. Partly conjecture but it is borne out in our observable universe - the universe looks the same in all directions and on a large enough scale the universe would appear to be homogeneous.  If the portion of the universe that is not observable is also isotropic and homogenous then it could well be that the universe is truly infinite.

The data that is needed to determine if the universe is infinite or not is to measure the curvature of the universe.  There are three different regimes of curvature - it could have a positive curvature resembling the two dimensional curvature of the surface of a sphere, zero curvature which is like a flat plane, or negative curvature which is like the concave curvature of the surface of a saddle.  If the universe is isotropic and homogenous and the curvature of the universe has a constant positive value then the universe will be finite - just as the surface of a sphere is finite.  On the other hand if the curvature of the universe is a constant of zero or has a constant negative curvature, the universe would be truly infinite.

 

There is no definitive answer at this point but the universe is consistent with having zero curvature. I believe that the standard model of cosmology which successfully accommodates all well measured cosmological information has a defined parameter which is related to the curvature.  If it is less than 1.0 then the universe is positively curved, if it is exactly 1.0 the universe is flat and if the value is greater than 1.0 the universe is negatively curved.  The best measured value is something like 1.0021.  We really don't actually know if the universe is infinite at this point, but since that value is so close to flat, even if the universe is positively curved and finite, you could hypothesise that it would be exponentially bigger than the observable universe.

 

Some theoretical physicists speculate that space-time is curved, so that although inflating, notionally if you travel far enough, you end up where you started.

 

If the Big Bang has happened, there is no way that the Universe, can reach an infinite size, in a finite amount of time.

If the Universe is infinite and has existed an infinite amount of time, then we would have a case of Olbers paradox...

 

http://hyperphysics.phy-astr.gsu.edu/hbase/Astro/olbers.html

 

I like to think of the man walking lost in the desert. He his right footed so takes longer strides with his right step so eventually ends up where he started.

As the mass of the universe was set by fluke when there was more matter left than anti matter. Gravity can't count for it's path. Is there still dark energy left pulling the whole thing in circles and does this affect photons. If a black hole can catch light with gravity then it can be affected by other forces too meaning the universe at some point will reach it's maximum arc.

If so then anything outside of that arc has no energy influence and therefore no time and therefore no space and does not exist.

[Great Boos Up]

Weirdly I want to ask more questions on the quantum small scale than the giant mechanics of relationships of atoms that form our universe.

Perhaps @leicsmaccovered this ?

 

[Sampson]

56 minutes ago, Great Boos Up said:

Weirdly I want to ask more questions on the quantum small scale than the giant mechanics of relationships of atoms that form our universe.

Perhaps @leicsmaccovered this ?

 

If you're not aware of the Double-Split Experiment, it's definitely worth reading up on or watching a few videos on until you grasp it - it's the most famous Quantum Mechanics experiment which explains the fundamentals of quantum mechanics best and why it's so mind bending and illogical and completely changed our view of the universe and reality.

 

 

Edited 19 October 2017 by Sampson