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Photon as a bullet. A newtonian question..

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TauTsar
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Photon as a bullet. A newtonian question..

#1 Post by TauTsar » Fri Jul 27, 2018 5:32 am

As light can't escape a black hole..

A bullet and a photon are simultaneously fired from a gun. The bullet falls to the ground at x distance from the gun. Question, how wide would earth need to be before the photon hit the ground?

Perhaps black-holes aren't super-gravitational but just really wide.

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Re: Photon as a bullet. A newtonian question..

#2 Post by arjaybe » Fri Jul 27, 2018 12:39 pm

It wouldn't matter how wide the planet was. The speed of light is greater than a planet's escape velocity.
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Re: Photon as a bullet. A newtonian question..

#3 Post by Stevo » Fri Jul 27, 2018 2:20 pm

The singularity literally has no dimensions at all, being considered as a mathematical point. So it has no width. Going by the way relativity handles it, its gravity warps space so much that all possible paths lead into the singularity.

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Re: Photon as a bullet. A newtonian question..

#4 Post by TauTsar » Fri Jul 27, 2018 5:24 pm

Black holes are interesting, thanks for indulging my simple mind.

Thinking about the expansion of the universe and the proposed cause being dark energy. I was considering our universe being either in a large black hole or entering into one. With the black hole devouring matter, converting it into energy and injecting it into our universe creating expansion.

The obvious flaw in this hypothesis being we'd be destroyed and converted into energy as well.

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Re: Photon as a bullet. A newtonian question..

#5 Post by arjaybe » Fri Jul 27, 2018 7:59 pm

Some hypotheses do speculate that black holes might be universes, but I think it's the surface of the event horizons they mean.
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Re: Photon as a bullet. A newtonian question..

#6 Post by colin_b » Fri Jul 27, 2018 8:40 pm

I'm not convinced singularities exist because of their infinite nature. Let me explain with this thought experiment.

Imagine you're stood at your bathroom sink. We'll call the top of the basin the event horizon - if anything goes past this it can't come back out. We'll also imagine the plug is out and that the suction from the plug hole is infinite.

If you turn on a tap the water will fall into the basin, and in milliseconds it would be sucked down the plug hole. If the second tap is turned on the same will occur. If more taps are added to the sink, it's irrelevant how many, the same will occur because of the infinite suction - the water from a thousand taps would disappear near instantaneously. When the taps are turned off the sink would immediately be empty because of the infinite suction from the plug hole.

With this thought experiment I find it impossible to believe that supermassive black holes can exist at he center of galaxies. It's a contradiction in terms, something can either be supermassive or it can be a black hole, but it can't be both because infinite gravity won't allow it.

That's my wacky thought for today :happy:

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Gordon Cooper
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Re: Photon as a bullet. A newtonian question..

#7 Post by Gordon Cooper » Fri Jul 27, 2018 9:21 pm

Illogical thinking. If light was trapped in a black hole, then possibly the black hole would be of a lighter hue ? :bagoverhead:
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Adrian
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Re: Photon as a bullet. A newtonian question..

#8 Post by Adrian » Fri Jul 27, 2018 9:48 pm

colin_b, black holes don't have infinite mass, the mass is just enough so the escape velocity is higher than the speed of light (so impossible to escape even for light). You cannot compare that to a sink. Also, black holes behave like regular objects of the same mass, so if the Moon was replaced with a black hole of the same mass as the Moon pretty much nothing would change with the Earth https://what-if.xkcd.com/129/

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Re: Photon as a bullet. A newtonian question..

#9 Post by Stevo » Fri Jul 27, 2018 9:50 pm

Well, lot of deep thinkers are also offended by the singularity dictated by the equations and have come up with workarounds and alternatives. Even Hawking was wrong about no information ever coming back from within the event horizon, and lost a famous bet about that. https://en.wikipedia.org/wiki/Thorne%E2 ... eskill_bet

About the thought experiment--gravity doesn't work like water in a tub that always seeks the lowest level. The usual analogy is that of weights on a stretchy rubber sheet, a 2D representation of space-time, where a black hole is so heavy that it tears a hole in the sheet. Matter can be more influenced by closer weights/depressions, like we are held to the earth's surface instead of flying off to our galaxy's central supermassive black hole.

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colin_b
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Re: Photon as a bullet. A newtonian question..

#10 Post by colin_b » Sat Jul 28, 2018 6:39 pm

It's the infinite part of a singularity which bakes my noodle.

If the singularity is a point in space with infinite gravity, then where is the pull of the gravity not infinite? At the edge of he singularity? A millimeter away? A meter away? 100KM away? A light year away? I can't see an answer because of infinity, it screws everything up.

My guess is a black hole is a star with gravity which is strong enough to prevent light escaping, i.e. incomprehensibly strong, but its gravity is not infinite.

Gamma rays have more energy than light, and they can escape from black holes https://www.newscientist.com/article/dn ... ack-holes/. I can't see this happening if a singularity exerts infinite gravity upon them.

Anyway, I'm sure your bored of my wacky thinking so I'll leave it there.

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