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

[andy_s]

ash73 said:

andy_s said:

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?

Yep, except light doesn't behave like that; if the two cars flash their headlights they will both see the photons of light approaching at c. Everything is relative, except c. And because c is constant other things (distance and time) have to bend.

Yes - in the analogy the cars were the galaxies, the light from them is a different matter (no geek pun intended), but I see what you mean.

[steve singh]

Laplace said:

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.

Not really, the grand design by Hawking's simply says we should ignore events before the big bang as there was no such thing as time?

However on deeper reading, as I understand it, it suggests the singularity originated and then exploded based on the laws of nature - this therefore implies that the laws of nature pre-existed the big bang, which then says something existed before the big bang?

I think the Grand Design work was widely regarded in science as a mere Ego stroke as opposed to anything of substance.

[Laplace]

steve singh said:

Not really, the grand design by Hawking's simply says we should ignore events before the big bang as there was no such thing as time?

However on deeper reading, as I understand it, it suggests the singularity originated and then exploded based on the laws of nature - this therefore implies that the laws of nature pre-existed the big bang, which then says something existed before the big bang?

I think the Grand Design work was widely regarded in science as a mere Ego stroke as opposed to anything of substance.

Anything written regarding conditions pre big bang at this present time and for the foreseeable future are going to be nothing more than educated ideas and musings.

The "big bang" or period of rapid expansion need not imply the laws of nature pre existed the big bang. These laws were created at the moment of the big bang. Run a few million "big bang" events and you will probably never see the same laws twice, you will also be a long way from reaching the amount of possible combinations if string theory predictions are to be believed.

[steve singh]

Laplace said:

steve singh said:

Not really, the grand design by Hawking's simply says we should ignore events before the big bang as there was no such thing as time?

However on deeper reading, as I understand it, it suggests the singularity originated and then exploded based on the laws of nature - this therefore implies that the laws of nature pre-existed the big bang, which then says something existed before the big bang?

I think the Grand Design work was widely regarded in science as a mere Ego stroke as opposed to anything of substance.

Anything written regarding conditions pre big bang at this present time and for the foreseeable future are going to be nothing more than educated ideas and musings.

The "big bang" or period of rapid expansion need not imply the laws of nature pre existed the big bang. These laws were created at the moment of the big bang. Run a few million "big bang" events and you will probably never see the same laws twice, you will also be a long way from reaching the amount of possible combinations if string theory predictions are to be believed.

The Beginning of Time - Stephen Hawking:

The conclusion of this lecture is that the universe has not existed forever. Rather, the universe, and time itself, had a beginning in the Big Bang, about 15 billion years ago. The beginning of real time, would have been a singularity, at which the laws of physics would have broken down. Nevertheless, the way the universe began would have been determined by the laws of physics, if the universe satisfied the no boundary condition. This says that in the imaginary time direction, space-time is finite in extent, but doesn't have any boundary or edge.





Like you said, it's all best fit and some of the scientific explanations are really a leap of faith that is no different as that required in religion.

[Robb F]

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

Of course it could be wrong, it's science. If anything had been observed that rendered the big bang theory impossible it would have been thrown out already.

Read 'A universe from nothing' by Lawrence Krauss to see how something came can come from nothing. *Ninja edit

Edited by Robb F on Monday 20th January 15:34

[nammynake]

steve singh said:

Like you said, it's all best fit and some of the scientific explanations are really a leap of faith that is no different as that required in religion.

'Faith' in religion is blind by definition. The belief in a supreme entity without evidence.

Science is the continued act of using experimental evidence to support or refute theory.

[Laplace]

steve singh said:

The Beginning of Time - Stephen Hawking:

The conclusion of this lecture is that the universe has not existed forever. Rather, the universe, and time itself, had a beginning in the Big Bang, about 15 billion years ago. The beginning of real time, would have been a singularity, at which the laws of physics would have broken down. Nevertheless, the way the universe began would have been determined by the laws of physics, if the universe satisfied the no boundary condition. This says that in the imaginary time direction, space-time is finite in extent, but doesn't have any boundary or edge.

The laws as we know them would not have existed before the big bang, just as Hawking states in your quote. That's not to say there wasn't laws that gave rise to the primordial conditions that allowed the universe to come into existence, just not the ones we are bound by today.
Are you asking what came before the singularity rather than the big bang?

[steve singh]

Laplace said:

steve singh said:

The Beginning of Time - Stephen Hawking:

The conclusion of this lecture is that the universe has not existed forever. Rather, the universe, and time itself, had a beginning in the Big Bang, about 15 billion years ago. The beginning of real time, would have been a singularity, at which the laws of physics would have broken down. Nevertheless, the way the universe began would have been determined by the laws of physics, if the universe satisfied the no boundary condition. This says that in the imaginary time direction, space-time is finite in extent, but doesn't have any boundary or edge.

The laws as we know them would not have existed before the big bang, just as Hawking states in your quote. That's not to say there wasn't laws that gave rise to the primordial conditions that allowed the universe to come into existence, just not the ones we are bound by today.
Are you asking what came before the singularity rather than the big bang?

Yes to your last question - i've read about multiverses and the theory of cosmic background radiation with differentials in temperature which suggests a possible cyclical cycle of universe, back to singularity then back to a big bang.

[AJI]

steve singh said:

.....suggests a possible cyclical cycle of universe, back to singularity ....

Would there be enough mass/energy for a cyclic universe to reduce back down to a singularity/big bang condition?

I thought that the initial 'fight' between matter and anti-matter took out much of the mass present at the big bang, the resultant mass expanding and then compressing under gravity would not return conditions to what they were at the beginning.
Probably having a major oversight of something or other so happily stand to be corrected.

I know energy is conserved (in present laws of physics anyways), but even after the matter/anti-matter battle the resultant energy would not have gravitational effects on the resultant universe would it?

[Laplace]

AJI said:

Would there be enough mass/energy for a cyclic universe to reduce back down to a singularity/big bang condition?

I thought that the initial 'fight' between matter and anti-matter took out much of the mass present at the big bang, the resultant mass expanding and then compressing under gravity would not return conditions to what they were at the beginning.
Probably having a major oversight of something or other so happily stand to be corrected.

I know energy is conserved (in present laws of physics anyways), but even after the matter/anti-matter battle the resultant energy would not have gravitational effects on the resultant universe would it?

I guess as visible matter only makes up a miniscule amount of what the universe is made of it may have little affect on the outcome of the universe, or not. Dark matter and dark energy are thought to be the main constituents of the universe with the more abundant dark energy thought to be driving the accelerating expansion.

Also, to say energy is conserved is to take a classical view of the universe. With general relativity it is shown that energy, with certain caveats, is not conserved.

I like the idea of a "cyclic" universe but I'm going to side with the big freeze where the universe just keeps expanding and becomes a cold and desolate place.

Edited by Laplace on Tuesday 21st January 02:00

[annodomini2]

AJI said:

steve singh said:

.....suggests a possible cyclical cycle of universe, back to singularity ....

Would there be enough mass/energy for a cyclic universe to reduce back down to a singularity/big bang condition?

I thought that the initial 'fight' between matter and anti-matter took out much of the mass present at the big bang, the resultant mass expanding and then compressing under gravity would not return conditions to what they were at the beginning.
Probably having a major oversight of something or other so happily stand to be corrected.

I know energy is conserved (in present laws of physics anyways), but even after the matter/anti-matter battle the resultant energy would not have gravitational effects on the resultant universe would it?

There was something recently that for 'the big crunch' to occur there would have to be some kind of shift in the Higgs field.

Some scientists reckoned it was feasible, but it's still a bit out there.

[Laplace]

annodomini2 said:

There was something recently that for 'the big crunch' to occur there would have to be some kind of shift in the Higgs field.

Some scientists reckoned it was feasible, but it's still a bit out there.

That sounds intersting. I'm guessing it must be some sort of shift in the field which will alter the mass of elementary particles from what they are now.

[steve singh]

We could just be the output of a universe sucked into a black hole and we're now the other side of it!

[AA999]

I think this thread conveys some of the misconceptions, but this vid from Veritasium explains things in slightly more Layman terms...
https://www.youtube.com/watch?v=XBr4GkRnY04&li...


The main points to take away are (a) The Hubble Sphere and (b) the universe is (and has always been) expanding faster than the speed of light.

[KareemK]

AA999 said:

I think this thread conveys some of the misconceptions, but this vid from Veritasium explains things in slightly more Layman terms...
https://www.youtube.com/watch?v=XBr4GkRnY04&li...


The main points to take away are (a) The Hubble Sphere and (b) the universe is (and has always been) expanding faster than the speed of light.

Excellent spot - thanks.