The speed of gravity.

Pyro Pilots Lounge. For all topics *not* covered in other DBB forums.

Moderators: fliptw, roid

Post Reply
User avatar
Spaceboy
DBB Captain
DBB Captain
Posts: 603
Joined: Sat Oct 02, 2004 11:43 pm
Contact:

The speed of gravity.

Post by Spaceboy »

A thought just occured to me. What is the speed of gravity?
I'm aware it's a dip in space, but it can't be instant, can it?

For example, if the sun were to suddenly dissapear, how long would the Earth orbit the sun after it had dissappeared? 8 minutes at the speed of light? is it slower, or faster?
User avatar
fliptw
DBB DemiGod
DBB DemiGod
Posts: 6459
Joined: Sat Oct 24, 1998 2:01 am
Location: Calgary Alberta Canada

Re: The speed of gravity.

Post by fliptw »

Spaceboy wrote:Fore example, if the sun were to suddenly dissapear, how long would the Earth orbit the sun after it had dissappeared? 8 minutes,the speed of light? is it slower, or faster?
Gravity is a weak force, and it takes a massive object to exert a noticeable pull. Playing with Einstein's ideas, its not a question of the speed of gravity, its a question of how fast can space be deformed. Einstien states that nothing can travel faster than the speed of light, so the fastest we'd feel it is on the order of 8 minutes.

But what would we feel?
User avatar
Spaceboy
DBB Captain
DBB Captain
Posts: 603
Joined: Sat Oct 02, 2004 11:43 pm
Contact:

Post by Spaceboy »

So the speed of light is really the speed space can be deformed? That explains alot for me, actually.

I've read numerous times that no matter what speed you're going, light always appears to be traveling the speed of light. Is it really just that, say you got to the point where you were going 100mph slower than the speed of light, time would slow down enough for you that that extra 100mph appears to be the speed of light?

Does the distortion of time limit the amount the universe can be distorted to the speed of light, or does that limit at which the universe can be distorted the cause of time's distortion?

Are there any other properties to the speed of light, or the speed at which the universe can be deformed that I might not know?

I've just been thinking about it lately and am very bugged about it, so I've been asking about it everywhere.
Better yet, reccomend any books on the subject?
User avatar
QuestionableChaos
DBB Ace
DBB Ace
Posts: 81
Joined: Fri Aug 08, 2008 4:49 pm
Location: soCal

Post by QuestionableChaos »

speed of gravity is up for analysis
http://en.wikipedia.org/wiki/Speed_of_gravity
User avatar
Spaceboy
DBB Captain
DBB Captain
Posts: 603
Joined: Sat Oct 02, 2004 11:43 pm
Contact:

Post by Spaceboy »

Haha, wiki.
I picked up a book called \"The Elegant Universe\" and it explain most of my questions and questions about the explanations in like the first page, +1 for reading.

Thanks though.
User avatar
Neo
DBB Captain
DBB Captain
Posts: 990
Joined: Mon Mar 08, 2004 6:03 am

Post by Neo »

The speed of the graviton (the particle that transmits the force of gravity) is supposedly the speed of light. This, however, doesn't make sense, because, for example, the sun is pulling the earth (and vice versa) where it is now, not where it was 8 minutes ago. =P
Does the distortion of time limit the amount the universe can be distorted to the speed of light, or does that limit at which the universe can be distorted the cause of time's distortion?

Are there any other properties to the speed of light, or the speed at which the universe can be deformed that I might not know?
Try not to think too much about general relativity (theory of gravitation) when trying to understand the relative motion of light (special relativity). Einstein said that no matter which speed you are travelling, the speed of a light wave is always c. If you want to read about Relativity, just start with the book Relativity, 100th anniversary edition by Albert Einstein. Oh, and be familiar with calculus and differential equations when you read it. :P I wouldn't recommend reading about Relativity, though.

...because gravity is an electric phenomenon in an electric universe. ^_~
User avatar
d3jake
DBB Admiral
DBB Admiral
Posts: 1075
Joined: Tue Dec 21, 2004 10:08 am
Location: Minnesota, USA

Re:

Post by d3jake »

Spaceboy wrote:I picked up a book called "The Elegant Universe" and it explain most of my questions and questions about the explanations in like the first page, +1 for reading.
Check out pbs.org and see if you can find a program by the name of that book, awesome TV series.
User avatar
TIGERassault
DBB Admiral
DBB Admiral
Posts: 1600
Joined: Tue Aug 10, 2004 3:33 pm

Post by TIGERassault »

I just have one question: is the concept of a gravitational field having a field a fundamental law, or currently just a theory? Because if it's the latter, then I don't want to get into it.
User avatar
Top Gun
DBB Master
DBB Master
Posts: 8088
Joined: Wed Nov 13, 2002 3:01 am

Post by Top Gun »

In scientific terms, the distinction you're trying to make doesn't really make sense. A scientific law is simply an observation about the way the universe works. The famous law of conservation of mass/energy states that matter and energy cannot be created or destroyed, merely converted from one to the other; it's considered a law because that's exactly what we see happen in every observation we take. In contrast, a scientific theory describes an explanation for a certain set of phenomena that is consistent with the results of repeated experimentation. The theories of special and general relativity provide a model for how objects moving near the speed of light interact with one another based on our observations about how the universe works. In this context, the idea of gravitational fields fits into the category of theoretical model (as part of general relativity), since it generally meshes with what we've observed about the interaction of light with massive bodies. I can't say I've ever heard of the concept of a gravitational field having a field itself, if that's what you meant; that idea wouldn't seem to make a whole lot of fundamental sense.
Post Reply