# If photon is mass-less why can it be pulled into blackhole?

Discussion in 'Physics & Math' started by Saint, Aug 7, 2017.

1. ### exchemistValued Senior Member

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No he's talking about the situation Write4U referred to, which is one involving 2 bodies only. Your scenario involves 3.

3. ### Write4UValued Senior Member

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The "net effect" may be the same but it took the acceleration of momentum to be able to escape the pull of gravity again. It's the "gross increase" in speed that allows us to break away again in the first place. If the speed is not sufficient then the object will establish an orbit or fall into the massive object.

Actually the slingshot effect is used to map a routes from planet to planet and eventually out of the solar system.

The best example is incoming debris never reaching the earth because the earth is protected by Jupiter, which captures it before it reaches the earth.
and
There is no problem with the slingshot effect, we use it to plot our maps for navigation through the solar system, and in the case of New Horizons, to eventually escape the solar system altogether.

How this effects EM, I believe has been demonstrated by Einstein which showed that relative to the earth, photons do curve around very massive objects. They do this @ c because photons can't travel faster than "c", but which is sufficient speed to enter and escape the gravity pull of other stars, if passing by at the right angle and distance.

5. ### Write4UValued Senior Member

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deleted for duplication
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Last edited: Aug 17, 2017

7. ### originHeading towards oblivionValued Senior Member

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I do not know what the 'acceleration of momentum' means.
If you are saying that the acceleration due to gravity of a small mass as it approaches a planet is the reason it can escape a planets gravity, then you have not been listening.
The new horizons uses the orbital speed of the planets to increase it's speed relative to the sun.

Imagine there are 2 bodies one is a satellite at a great distance from a planet about the size of earth. Assume the satellite is moving towards the planet at 1000 mph. As it approaches the planet it will increase in speed due to gravity. If the approach is very close to the planet the speed will be in the neighborhood of 25,000 mph as it swings around the planet. It will then move away from the planet in a new trajectory and will slow down due to gravity. When the satellite it very far from the planet it will be moving away from the planet at 1000 mph once again. No speed increase what so ever.

And with that I give up. Have a good day.

8. ### QuarkHeadRemedial Math StudentValued Senior Member

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It does you know. If a theory is a field theory, and everything on one side of an equality (in that theory) is field, then obviously everything on the other side of that equality is likewise a field.

I do not understand your inability to be civil.

I just love the "we" in there. But why do you think these guys are called "dark"? Could it just be because nobody has any idea what they are?

9. ### originHeading towards oblivionValued Senior Member

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It is sort of his hallmark....

10. ### Write4UValued Senior Member

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Yes, it's called the slingshot effect and it holds for all massive objects. Truckers use it vertically when navigating a hilly terrain. Increase momentum going down hill, in order to gather enough momentum to overcome the earths gravity going up the next hill. There is nothing special about it.
I've experienced it myself, going up and down the Grapevine in California, a truckers nightmare.

The term slingshot was not recently invented. David v Goliath?

I am not making it mysterious or a new discovery. We've been using the principle of artificially increasing momentum for thousands of years. We discovered that gravity can be used for that purpose as well. There is no rocket powerful enough to escape the gravity of the sun, but we can use other planet's gravity to gain momentum, albeit at cost (or benefit) of a change in direction. The term centrifugal force is directly related to the slingshot effect.

Last edited: Aug 17, 2017
11. ### The GodValued Senior Member

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Yes I am sort of a bit uncivil or rather tired with you. The reason is you being an autodidact pretending as expert.

Pl reread and understand what field is. And then try to learn that energy-momentum is not a field as you are claiming.

And on DM and DE do not get into semantics, just learn that they cannot make a tensor mysterious as you are claiming. No tensor or vector or scalar is mysterious. Get it?

Your slips are visible, likes of origin cannot see them. He is nicely engaged by W4U on gravity assist.

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Ok

13. ### exchemistValued Senior Member

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You are muddling several different things. Again.

1) You can't "accelerate momentum". That is a meaningless idea. You can accelerate a body and that will change (increase or decrease) its momentum.

2) The slingshot as used by David on Goliath uses the idea of increasing angular momentum by whirling the thing round the head and then, by instantaneously removing the centripetal force that constrains the object to move in a circle, it flies off at a tangent with considerable linear momentum. However the increase in its momentum is achieved by making it turn faster and faster beforehand, which is a concept totally unrelated to trucks accelerating downhill and decelerating uphill. That is to do with converting gravitational potential energy to kinetic and then back again. Altogether different.

3) Neither of the above explains the use of a 3rd astronomical body to change the momentum of a satellite. This uses the motion of the 3rd body, combined with its gravitational pull, to impart extra kinetic energy: https://en.wikipedia.org/wiki/Gravity_assist

14. ### Write4UValued Senior Member

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As I said, we can use semantic arguments, the principle remains the same. T = 0 is an absolute statement. K = 0 is an absolute statement.

15. ### DaveC426913Valued Senior Member

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Really? See if you can find a reference to "the slingshot effect" involving trucks on hills.

Just because you like the word slingshot doesn't mean you use its multiple applications in order to conclude that two dissimilar things are the same.

This apple is red and convex.
Firetrucks are red and are, IMO, sort of convex.
Therefore, firetrucks are apples.

'Slingshot' has an unambiguous meaning in orbital mechanics.

Nothing in the last 43 posts has been related to the thread topic. It has been one giant sidebar, entirely stemming from this muddling.

16. ### Write4UValued Senior Member

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Seems to me that spacetime itself has a hilly aspect. Gravitational curvature of space time is in all directions, up, down, sideways

What's the difference? A sailboat uses the same dynamic mathematics of (horizontal) "lift" to propel itself forward, just like an airplane uses the dynamics of (vertical) lift to propel itself upward.
Are you telling me this is always in a horizontal plane.

Gravity of the earth is not greater or lesser at any other point on earth than it is here.
Up, down, sideways, have no meaning in space, except when plotting a specific course for maximum utility.

Last edited: Aug 17, 2017
17. ### DaveC426913Valued Senior Member

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Because you keep using the term 'slingshot effect' to mean something it doesn't.

And because it has nothing to do with the thread topic.

Again. Science subforum. Be scientifically accurate.

18. ### Write4UValued Senior Member

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Yes, such as expressions "spooky action at a distance" is scientifically accurate? Give the narrative a little leeway.
I think I have linked sufficient scientific data to prove my point. The rest is conversational and comparative examples.
I'll be the last person to say something is off topic, when discussing these great questions dealing with the properties of gravity. It seems that just about everything is related to gravity, one way or another.

19. ### DaveC426913Valued Senior Member

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Yes, it is.

The term isn't the problem; it's the definition you're inventing that's problematic.

For the OP's sake, and posterity's sake, it is important that people understand that the point was not made, and no amount of "looks-kinda-like" references changes that.

The Slingshot Effect cannot allow a particle to escape a gravitational well without at least one other body.

It's a pity that, after all we've explained, you are still don't understand gravitational assist .

Anyway, it has nothing to do with an example of particles escaping a black hole.

So, yes. Let's please drop it.

20. ### Write4UValued Senior Member

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The term "spooky action" is a scientific term? Well then, we can say that the universe is a spooky place. How far will that get you? I am inventing a definition of the term?
p.s. I know what Einstein meant, but the term he used is not a scientific term. But you forgive Einstein.
If I used that term, you'd be all over me that this is a science forum.

Give me break and try to understand the content of what I am saying, even as that may be expressed inadequately.

Last edited: Aug 18, 2017
21. ### DaveC426913Valued Senior Member

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Sure. Let's roll back the last 49 posts, to where you say 'I see now, this effect does not apply here. Thanks guys, for clearing up my misunderstanding.'

Let's move on.

Last edited: Aug 18, 2017
22. ### Write4UValued Senior Member

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Oh, I see. there was no gravitational pull involved, only the orbital speed of a planet. Kinda like riding in the wake of a big truck?

23. ### DaveC426913Valued Senior Member

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This is where you frequently go awry with your opinions.