Physics Question

Again Joe, you utterly failed to either read or comprehend my post. Try actually reading it with an open mind and maybe, just maybe, the light of comprehension will dawn.

You've hoist yourself with your own petard regarding thought experiments but you haven't realised it yet. :mrgreen:

In the meantime, the OU do an excellent science foundation course. Give it a go and learn something ;)
 
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It's YOU that's not getting it. We are talking about an imaginary universe where things can disappear as if by magic.

Can you have gravity without mass? Yes or no.
 
If you assume that in order for two bodies to attract each other they must both have mass, then this contradicts the fact that light (which has no mass) can be bent by a massive enough body.

Hence, to repeat the point I've made a couple of times, gravity is a property of space and not the body in question.
 
joe-90 said:
It's YOU that's not getting it. We are talking about an imaginary universe where things can disappear as if by magic.

Can you have gravity without mass? Yes or no.
Click to expand...

Oh it's an imaginary universe with magic? In that case, the unicorns will keep the planets in their orbital paths. :LOL:

In order to perform a thought experiment, you need a mind capable of rational thought... ;)
 
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Rational thought won't allow me to accept that any matter (especially the size of the sun) can disappear without a trace. It can't happen in our universe. I find it just a bit worrying that you think that it can.
 
calorific said:
If you assume that in order for two bodies to attract each other they must both have mass, then this contradicts the fact that light (which has no mass) can be bent by a massive enough body.

Hence, to repeat the point I've made a couple of times, gravity is a property of space and not the body in question.
Click to expand...

The real fact of the matter is that no-one knows what gravity is. Did you watch Horizon the other night? A leading scientist said that - not me. He reckons we know absolutely nothing about it.

It makes sense to me that gravity IS a property of space but it cannot exist when the body is removed. If you think it can - give me an example of gravity without mass.

While I've got your attention, what would be the properties of the void left by the magically disappearing sun?
 
joe-90 said:
Rational thought won't allow me to accept that any matter (especially the size of the sun) can disappear without a trace. It can't happen in our universe. I find it just a bit worrying that you think that it can.
Click to expand...

Again, show me where I said that it could. :mrgreen:

You do like to attribute things that people haven't said to them, don't you?
 
Oh it's an imaginary universe with magic? In that case, the unicorns will keep the planets in their orbital paths.

In order to perform a thought experiment, you need a mind capable of rational thought...

Let's see some rational thought from you then.
 
Joe yer being daft.

The o.p.'s question and the one we have all been answering is whether or not the effect of instant gravity loss of one stellar body would have an instant effect on nearby planets.

All this blather about mass and gravity.... :rolleyes:

I got it right ages ago. :p
 
joe-90 said:
The real fact of the matter is that no-one knows what gravity is. Did you watch Horizon the other night? A leading scientist said that - not me. He reckons we know absolutely nothing about it.
Click to expand...
Agreed - all we can do is check how well any evidence fits the model, subject to the usual constraints - in particular those pertaining to how accurately the "evidence" is gathered/observed

joe-90 said:
It makes sense to me that gravity IS a property of space but it cannot exist when the body is removed. If you think it can - give me an example of gravity without mass.
Click to expand...
As we don;t really know what gravity is, it's not really possible to give a definitive example :mrgreen: The closest one I have already suggested which might fit the bill if certain assumptions are made is of a light particle changing away from a linear path. One could argue that a massless light particle (such as it is) is "awarded" certain gravitational properties.


joe-90 said:
While I've got your attention, what would be the properties of the void left by the magically disappearing sun?
Click to expand...
My own suspicions are already stated - instantaneous disappearance of the sun would lead to an instantaneous non-gravity effect. I.e. it is as though it were never there.

There is no sudden "implosion" of a collapsing space, nor a wobbling rubber sheet IMO. For anyone who thinks that there would be a "sucking-in" effect - it could be argued that this would counteract the gravity that might be "en route" - thus the effect would be the same; i.e an instantaneous zer-gravity effect and not an 8 or so minute delay.
 
noseall said:
Joe yer being daft.

The o.p.'s question and the one we have all been answering is whether or not the effect of instant gravity loss of one stellar body would have an instant effect on nearby planets.

All this blather about mass and gravity.... :rolleyes:

I got it right ages ago. :p
Click to expand...


Yes it would have an instant effect as I've demonstrated to you.

There is a link between space, mass and gravity that no-one understands. However, it would seem that they are inseparable. Take away the mass and you take away the gravity associated with that mass.

There is no example of mass-less gravity in the universe. If there is - feel free to win the Nobel prize.

There is little to be gained in calling me an idiot just because you cannot refute my argument.

Remember - no-one knows anything at all about gravity other than the effect that it has. Its mechanism is sciences best kept secret. That tells me that the existing model is wrong and that some other, so far undiscovered model, is right.

It may never be understood, just as we don't understand infinity or eternity.
 
There is little to be gained in calling me an idiot just because you cannot refute my argument.
Click to expand...

Nobody is calling you an idiot because they cannot refute your argument. It must be for some other reason.
 
chapeau said:
There is little to be gained in calling me an idiot just because you cannot refute my argument.
Click to expand...

Nobody is calling you an idiot because they cannot refute your argument. It must be for some other reason.
Click to expand...


And just like gravity - it's one that no-one can find. ;)
 
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