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<blockquote data-quote="Umbran" data-source="post: 5306152" data-attributes="member: 177">It has been ages since I read it as well.&nbsp; At this time, I don't think Hawking would say gravity works instantaneously.&nbsp; The usual analogy is that spacetime is a rubber sheet, and masses rest on the sheet, and deform it.&nbsp; Now, if you do that with a real rubber sheet, it doesn't deform instantaneously.&nbsp; It actually takes time for the sheet to change shape.&nbsp; If you shake one end of the sheet, it takes time for that shaking to get to the other side of the sheet.&nbsp; Same thing here.They cause what they interact with to move back towards the source.&nbsp; It isn't exactly like colliding billiard balls here.&nbsp; There's nothing new about it, though.&nbsp; Electromagnetic forces are transferred by photons.&nbsp; If you bring a positive and negative electric charge near each other, they exchange photons, and are drawn together, too.They don't come from inside the black hole.&nbsp; You can think of them being emitted from the outer surface, if that helps.&nbsp; The real answer is that sometimes they act like particles, and sometimes they act like waves (again, just like light), and for most concerns, emission from a garden variety black hole is when they're more like waves.The photons have energy, and as Einstein told us, mass and energy are equivalent.&nbsp; Light is bent by heafy objects, occasionally leading to what astronomers call &quot;gravitational lensing&quot; (something else for you to look up).I don't believe they are mentioned there, so you're safe. <img src="https://cdn.jsdelivr.net/joypixels/assets/8.0/png/unicode/64/1f642.png" class="smilie smilie--emoji" loading="lazy" width="64" height="64" alt=":)" title="Smile&nbsp; &nbsp; :)"&nbsp; data-smilie="1"data-shortname=":)" />&nbsp; Remember that A Brief History of Time is brief, a short explanation.&nbsp; It doesn't contain everything.</blockquote>

[QUOTE="Umbran, post: 5306152, member: 177"] It has been ages since I read it as well. At this time, I don't think Hawking would say gravity works instantaneously. The usual analogy is that spacetime is a rubber sheet, and masses rest on the sheet, and deform it. Now, if you do that with a real rubber sheet, it doesn't deform instantaneously. It actually takes time for the sheet to change shape. If you shake one end of the sheet, it takes time for that shaking to get to the other side of the sheet. Same thing here. They cause what they [i]interact with[/i] to move back towards the source. It isn't exactly like colliding billiard balls here. There's nothing new about it, though. Electromagnetic forces are transferred by photons. If you bring a positive and negative electric charge near each other, they exchange photons, and are drawn together, too. They don't come from inside the black hole. You can think of them being emitted from the outer surface, if that helps. The real answer is that sometimes they act like particles, and sometimes they act like waves (again, just like light), and for most concerns, emission from a garden variety black hole is when they're more like waves. The photons have energy, and as Einstein told us, mass and energy are equivalent. Light is bent by heafy objects, occasionally leading to what astronomers call "gravitational lensing" (something else for you to look up). I don't believe they are mentioned there, so you're safe. :) Remember that [i]A Brief History of Time[/i] is brief, a short explanation. It doesn't contain everything. [/QUOTE]

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