Freethought & Rationalism Archive

cfgauss · 01-14-2003, 01:35 PM

I don't think I follow you...

beco · 01-14-2003, 01:50 PM

If I gave you two readings of a particular piece of space how could you determine which occured first? Measure the entropy? Some other method, how can one event be determined to occur before or after another event in physics. I'm sorry if I'm not making sense, I'm trying to remember what Hawkins said on the subject. Last try I'll have to do some reading.

Hawkingfan · 01-14-2003, 02:10 PM

Quote:

Originally posted by beco
Err *raises hand* is there a good working defination of "time" now? I remember S. Hawkins saying time was entropy. I'm a layman, be gentel.

It's "Stephen Hawking"

He was probably quoting the second law of thermodynamics which states that entropy increases with the passage of time. He has used thermodynamics to explain the event horizon (boundary) of black holes.

Hawkingfan · 01-14-2003, 02:20 PM

Time is a personal concept, relative to the observer who measures it. The laws of science do not distinguish between the past and the future. Entropy is only one example of the "arrow of time"--a thing that is able to distinguish the past from the future, giving a direction of time. There are 3 arrows of time:
1--thermodynamic: entropy increases
2--psychological: direction which we feel time pass, remember the past but not the future.
3--cosmological: direction of time in which the universe is exanding and not contracting.

(Imaginary time, invented by Hawking and Penrose, was developed in order to unify gravity with quantum mechanics. It had to be imaginary because the mathematics was limited by directions in space, a result of time #3 above).

Mageth · 01-14-2003, 02:29 PM

Imaginary time, invented by Hawking and Penrose

C'mon, lawyers have been using imaginary time in their billing records for decades.

cfgauss · 01-14-2003, 04:19 PM

Hawkingfan, that is so wrong it's not even funny.

Time has no more to do with observers or perception than space does! Remember time is another dimension--almost exactly like each of the dimensions in a normal Cartesian plane that you learned about in grade school.

Your arrow of time thing doesn't even make sense. And regarding the 'imaginary time' thing, have you even looked at SR? Notice those little i's next to some of those t's? Did you read the box in the textbook when they introduced them? Didn't think so.

Starboy · 01-14-2003, 07:14 PM

I don't know much about GR but recently it occured to me that our perception of the flow of time may be an artifact of the expansion of the universe. No expansion, no flow of time.

Starboy

cfgauss · 01-14-2003, 08:47 PM

No, that doesn't really make any sense in the context of GR.

fando · 01-14-2003, 11:17 PM

beco · 01-15-2003, 05:48 AM

Ok it's official, I really don't have a clue about physics. Thanks for trying to help out there, really.

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01-14-2003, 01:35 PM	#11
cfgauss Regular Member Join Date: Jan 2003 Location: USA Posts: 108	I don't think I follow you...

01-14-2003, 01:50 PM	#12
beco Regular Member Join Date: Jan 2003 Location: Reston, VA Posts: 123	If I gave you two readings of a particular piece of space how could you determine which occured first? Measure the entropy? Some other method, how can one event be determined to occur before or after another event in physics. I'm sorry if I'm not making sense, I'm trying to remember what Hawkins said on the subject. Last try I'll have to do some reading.

01-14-2003, 02:20 PM	#14
Hawkingfan Veteran Member Join Date: Oct 2002 Location: Texas Posts: 1,247	Time is a personal concept, relative to the observer who measures it. The laws of science do not distinguish between the past and the future. Entropy is only one example of the "arrow of time"--a thing that is able to distinguish the past from the future, giving a direction of time. There are 3 arrows of time: 1--thermodynamic: entropy increases 2--psychological: direction which we feel time pass, remember the past but not the future. 3--cosmological: direction of time in which the universe is exanding and not contracting. (Imaginary time, invented by Hawking and Penrose, was developed in order to unify gravity with quantum mechanics. It had to be imaginary because the mathematics was limited by directions in space, a result of time #3 above).

01-14-2003, 02:29 PM	#15
Mageth Contributor Join Date: Jul 2001 Location: Deep in the heart of mother-lovin' Texas Posts: 29,689	Imaginary time, invented by Hawking and Penrose C'mon, lawyers have been using imaginary time in their billing records for decades.

01-14-2003, 04:19 PM	#16
cfgauss Regular Member Join Date: Jan 2003 Location: USA Posts: 108	Hawkingfan, that is so wrong it's not even funny. Time has no more to do with observers or perception than space does! Remember time is another dimension--almost exactly like each of the dimensions in a normal Cartesian plane that you learned about in grade school. Your arrow of time thing doesn't even make sense. And regarding the 'imaginary time' thing, have you even looked at SR? Notice those little i's next to some of those t's? Did you read the box in the textbook when they introduced them? Didn't think so.

01-14-2003, 07:14 PM	#17
Starboy Banned Join Date: Jun 2002 Location: Tallahassee, FL Reality Adventurer Posts: 5,276	I don't know much about GR but recently it occured to me that our perception of the flow of time may be an artifact of the expansion of the universe. No expansion, no flow of time. Starboy

01-14-2003, 08:47 PM	#18
cfgauss Regular Member Join Date: Jan 2003 Location: USA Posts: 108	No, that doesn't really make any sense in the context of GR.

01-14-2003, 11:17 PM	#19
fando Veteran Member Join Date: Sep 2001 Location: Los Angeles Area Posts: 1,372

01-15-2003, 05:48 AM	#20
beco Regular Member Join Date: Jan 2003 Location: Reston, VA Posts: 123	Ok it's official, I really don't have a clue about physics. Thanks for trying to help out there, really.

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