Earth-sized' UFO orbiting Sun

Discussion in 'The Guru's Pub' started by J.B.west, Oct 27, 2014.

1. DeathchildAncient Guru

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It's not another photon created, it bounces off the side of the wall and reaches our eyes. So a reflection. It's the same light from the sun it's just that it's been mirrored and reflected a lot of times thus it reaches everywhere.

But didn't AsiJu already determine that photon is a sort of energy but with no mass. It's an energy of its own?

Damn I love physics, The explanation of the universe (in our own limited understanding). XD

http://en.wikipedia.org/wiki/Andromeda_Galaxy#mediaviewer/File:WISE-_Andromeda.jpg

Look at the picture guys and think of all the civilizations there.

Last edited: Nov 4, 2014
2. southamptonfcAncient Guru

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That's totally incorrect. Inertia or momentum has nothing to do with gravity.

f=ma

Photons do have intertia.

Last edited: Nov 4, 2014
3. DeathchildAncient Guru

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Inertia has everything to do with gravity, why does a ball gain an increased strength/amplitude of swaying when you hold it with a thread/string?

It's the gravity that pulls down the ball everytime it goes up, it adds to the strength everytime, thus inertia is created.

Isn't this what inertia is?

Last edited: Nov 4, 2014
4. southamptonfcAncient Guru

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No, intertia is an object's resistance to change of velocity.

Inertia is fundamentally linked to an object's mass. Mass is constant regardless of the presence of gravity.

f=ma

a = f/m

5. PhragmeisterAncient Guru

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Should have took school more serious lol.

6. AsiJuAncient Guru

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That's Newtons second law of motion you're referring to.
Force = mass x acceleration.

You solved for acceleration (of an object), which has nothing to do with inertia.
Also, inertia is the objects tendency to retain it's current state of motion, to be more precise.

Still, inertia is only present within a gravitational field. In vacuum there's no inertia.

7. southamptonfcAncient Guru

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'state of motion' as you put it is a rather vague attempt at saying velocity in mechanics!

Sorry but this is total BS. I'm not getting sucked into this. Bye!

8. AsiJuAncient Guru

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It's allright if you want to get 'technical', which I do ;-)

Mechanical engineering more precisely.
I do quotations, production development and design at a machine workshop.

The pay is fine. However this recession really isn't helping...

edit: about the photon: it can't be said it's an energy of its own, but photon HAS energy, determined by the frequency of light.
It does not, however, have mechanical (kinetic or potential) energy as it's massless.

To recap a bit, mass can have energy or, in some cases, can be converted to energy with a suitable process.
This doesn't mean that mass would be energy or vice versa, that's a misconception (common one in this thread).

Also, objects (=masses / particles) can exist without having energy.
Imagine you have an object at absolute zero temperature, resting on the floor or equivalent "zero height" (of potential energy).

Such object would practically have zero energy as even molecular motion is stopped.
We can't (yet) artificially reproduce absolute zero temperature exactly.
Still, it's safe to assume that mass doesn't seize to exist even then.

Last edited: Nov 6, 2014
9. AsiJuAncient Guru

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I'm willing to admit I may have mistaken that part, inertia is present in all inertial reference frames.

Mass is the measure of objects inertia, that's true (and so Newtons second law does relate to this too, I wrote too hastily above).
But there you have it: in turn, a photon doesn't have inertia as it's massless.

Newtons first law of motion is actually the law of inertia, stating:

"Every body continues in its state of rest or of uniform speed in a straight line unless acted on by a nonzero net force"
(source: Giancoli: Physics, Fifth Edition.)

This is also the way to see whether a frame of reference is inertial or not.
If it satisfies Newtons first law, it is. So yes, vacuum certainly satisfies that condition (an object keeps moving in space unless stopped by an external force).

Last edited: Nov 5, 2014