As Time goes by...

Driveby Dogboy

well, currently reading 'From Eternity To Here' by Sean Carroll (well dipping in and out, reading random chapters) and i was wondering if theres a book that explanes time better,
as far as i can see, this book is all about the arrow of time, and summed up it's basically: Entropy; therefore the Arrow of Time, which is cool, but it hardly takes a whole book to explain

Is there a book that explains what time is, what makes one 'moment' different from the next (knowing that there is no universal 'moment') what makes time keep pushing on..

or is my best bet to go back to the maths, and understand that my 'understanding' of time is fundamentally wrong, and is there anything ye could recommend reading on that?

I would infinitly prefer the former, but failing that any recommendations on the latter would be greatly appreciated

Driveby Dogboy

right, i have the book infront of me now, and Carroll says if you ask people 'what is time?' they usually come up with variations of 3 different answers

• time lables moments in the universe (a coordinate)
• time measures the duration elapsed between events (what clocks measure)
  
• time is a mediun through which we move (an agent of change, we move through it/ it flows past us)

nine times out of ten a physicist will say something related to the first two, a non-physicist will say something related to the third...

and then he mentions something about 'block time' and pretty much spends the next 350 pages talking about entropy, or so it seems from the random pages i've read anyway


Anyone want to shed some light on the third definition of it there?

PointLe55

The Moving Finger writes; and, having writ,
Moves on: nor all thy Piety nor Wit,
Shall lure it back to cancel half a Line,
Nor all thy Tears wash out a Word of it.

Morbert

Driveby Dogboy wrote: »

right, i have the book infront of me now, and Carroll says if you ask people 'what is time?' they usually come up with variations of 3 different answers

• time lables moments in the universe (a coordinate)
• time measures the duration elapsed between events (what clocks measure)
  
• time is a mediun through which we move (an agent of change, we move through it/ it flows past us)

nine times out of ten a physicist will say something related to the first two, a non-physicist will say something related to the third...

and then he mentions something about 'block time' and pretty much spends the next 350 pages talking about entropy, or so it seems from the random pages i've read anyway


Anyone want to shed some light on the third definition of it there?

The third definition doesn't really have any physical weight. The 2nd definition is the closest you will get to time being a physical quantity.

General Relativity implies time must be understood as facet of a more fundamental structure known as spacetime. Spacetime, in turn, is a construct of the gravitational field, which is affected by the distribution of energy and momentum in the universe (This is why GPS satellites need to accommodate changes in time measurements due to the mass of the earth).

In short, time is depreciated in modern physics, and spacetime (and the spacetime metric) is the more fundamental property.

smcgiff

Deykeap BadaBay wrote: »

What is that? What is happening?

Isn't that just entropy?

In Stephen Hawking's book, A brief History (Quite old, but I only got around to reading it recently) he says the arrow of time will reverse if the universe collapses into itself (the big crunch) - things would tend to become more ordered. We'd be long gone as a species, but if we existed we'd know our futures and not our past. Don't buy it myself.

Morbert

smcgiff wrote: »

Isn't that just entropy?

In Stephen Hawking's book, A brief History (Quite old, but I only got around to reading it recently) he says the arrow of time will reverse if the universe collapses into itself (the big crunch) - things would tend to become more ordered. We'd be long gone as a species, but if we existed we'd know our futures and not our past. Don't buy it myself.

The big crunch has fallen out of favour as more and more information about the universe is gathered. And even if turns out to be true, our current theories imply the arrow of time will not reverse. This is because, as the universe expands and particles interact via gravity, black holes will be formed. These black holes cannot be "undone" by reversing the expansion of the universe.

smcgiff

Morbert wrote: »

The big crunch has fallen out of favour as more and more information about the universe is gathered. And even if turns out to be true, our current theories imply the arrow of time will not reverse. This is because, as the universe expands and particles interact via gravity, black holes will be formed. These black holes cannot be "undone" by reversing the expansion of the universe.

Not a fan of the big crunch either. Just brought it up in the context of this thread.