Speed of Light question

[Hand of Evil]

The one that gets me is speed of gravity

 

[mps42]

Here's the way I understand it (which could be wrong).

Think of space-time as a huge sheet or blanket. There are things of different sizes and masses on this blanket. Each object creates a dent in the blanket, the more massive the object, the bigger the dent. That's gravity.
A "Black hole" is created when a white dwarf star (which is a super dense object) collapses in on itself to the point where there is an incredible amount of mass in almost no space. A virtual singularity.
Now, light passes along the surface of space-time but, for our discussion, is't really a "part" of it. Einstein theorized that light, being almost pure energy, traveled at a constant velocty, written as "c". That being the case, it can be effected by gravity (the dents in the fabric of space-time) but cannot be sped up by those dents. If that is true, then a "black hole" is bending light to the point where it keeps going around in circles and never gets out again. Light doesn't "stop". If it did, it couldn't be light, it would be something else. There are ways to detect black holes, by radio waves and radiation and such which means that we can currently either detect something that IS escaping the gravity hole or, in my opinion more likely, we can find them (black holes) by observing the movements of other objects.
Now, as for relativity, that's almost a completely different animal...

Dangit, now I gotta read "A brief history of time" again...

 

[fuindordm]

Black holes can come from a variety of different sources. AFAIK, they are usually created in supernova; a white dwarf is also a supernova remnant, but from a star that wasn't massive enough to make a black hole. There are also galactic black holes, which have as much mass as hundreds of thousands to millions of stars, and live in the core of many galaxies. These are thought to be the source of quasars.

When we observe black holes, we detect radiation emerging from its immediate environment: radio waves from electrons going into a death spiral down its magnetic field, X-rays from the accretion disc of superheated gas flowing into the black hole, and so forth.

Light that gets captured by a black hole really gets captured, although it is possible to get trajectories that spiral hundreds or thousands of times before they reach the hole.

Ben

 

[Umbran]

Would it be to much to think that light can be bent, could it not be slowed by the same force that bends it? Could that same force not alter its speed to go faster? Say the light speeds towards the massive star then slows as it passes then tries to pull away from that same star. Could that be true?

Nope, it can't

Above, you fall into the trap of thinking about light as a normal physical object. If you toss a ball near a massive object, it'll speed up and slow down as you describe, but light is not a rubber ball.

What happens to the ball is that it gains energy while falling towards the massive body, and loses energy when falling away. The speeding up and slowing down is a result of that energy gain and loss.

Light will also gain and lose energy, like the ball. But, having no mass, the speed of the light cannot vary. So, instead, the light changes wavelength. It shifts towards the blue while falling inwards, and shifts to the red when falling away.

Fuindorm: I'm sorry, but you've got the time thing backwards. Remember - time is relative. To a local observer, his own clock always seems to run normally. It's everyobdy else's clocks that change.

Take two clocks. Keep one yourself. Hand another to your friend, and drop him into the black hole (well, don't use a good friend for this).

You look at your clock, and it seems to be running normally. You take a telescope and look at your friend's clock, and it will seem to be running more and more slowly. The light reflecting off the clock face gets more and more red - from your perspective it's got fewer and fewer oscillations per second, a lower frequency. His clock ticks more and more slowly, and eventually, just as he reaches the Event Horizon, the ticks are infinitely far apart, and you never see the last one. From your point of view, he never actually falls into the hole. He can't, because time would have to pass for him to cross the threshold, his clock would have to advance, but he's frozen with the next tick off at forever...

From his own point of view, though, his clock keeps ticking just fine. But if he looks up at your clock, it seems to be speeding up! Ticks come faster and faster. The light falling in towards him has more and more oscillations per second, so it looks more and more blue. He just falls into, and through, the Event Horizon normally. From his point of view, it's the rest of the Universe that's speeding by.

 

[Kemrain]

http://homokaasu.org/gasgames/game.gas?21

It's not about light, but it involves Gravity heavily!

- Kemrain the Enjoying the Discussion.

 

[Harmon]

Thank you, Umbran for the time it took you to write that.

I actually knew all of that, modern understanding of the speed of light seems a little narrow minded to me and thus the question.

Reasons why I disagree with the theory about the speed of light and black holes pull is that the rules of our understanding change to an unknown bases when our physics is applied to a black hole. However when you consider that our perception is what limits our understanding it kinda opens up some new possibilities.

So- say there is something that is faster then the speed of light, something we can't see. How would we detect it it travels/moves faster then anything we can percieve (using our eyes, using advanced machines, etc- light is still the fastest "thing")

So if we open our minds to the possibility that there is something faster then light then we understand that light does not have a constant.

Our knowledge of the speed of light is based on the gravity around us, if we understood that light travels at different speeds in different areas of gravity then maybe we'd be able to understand the physics of a black hole a little better.

<shrug> thank you for your time and trying to help me get past this theory. I guess I am just not willing to accept that we understand everything absolutely. Like I said- thank you for your help.

 

[fuindordm]

Thanks, Umbran. You're right, of course, and I'm ashamed of myself. I even wrote a light-propagation code for black hole accretion disks a couple of years ago for my previous research project, and I still have to think hard every time the question comes up.

Ben

 

[fuindordm]

So- say there is something that is faster then the speed of light, something we can't see. How would we detect it it travels/moves faster then anything we can percieve (using our eyes, using advanced machines, etc- light is still the fastest "thing")

So if we open our minds to the possibility that there is something faster then light then we understand that light does not have a constant.

Our knowledge of the speed of light is based on the gravity around us, if we understood that light travels at different speeds in different areas of gravity then maybe we'd be able to understand the physics of a black hole a little better.

Well, people have theorized about tachyons (particles of negative mass that travel faster than light) and warp fields (configurations of gravitational fields that allow faster-than-light travel while still obeying the rules of relativity locally) in scientific journals.

I don't follow your question, though. Whether or not we can detect something has little to do with how fast it goes; it has everything to do with how it interacts with other particles. You're welcome to postulate a particle that moves faster than light and participates only in the gravitational interaction, which would be incredibly hard to detect unless the universe was filled to brimming with them. (Or maybe we have--who knows, it could be the 'dark energy' that we're hearing so much about these days.) But the existence of such a thing wouldn't change our understanding of light.

There's a lot of stuff out there in the theoretical journals that *could* exist as far as we know, and some of it's pretty wacky.

But I would bet all the limbs of my body that we do understand the nature of LIGHT completely. The theories governing the behavior of light have been subjected to experiments of incredible precision. Our understanding of gravity may change, but that won't affect the basic features of light--constant speed, redshifting and blueshifting, etc.

Cheers,
Ben

 

[Michael Morris]

Note on black holes and stars. Only really, really, really big stars produce black holes on their deaths. Most (like our sun) will expand into red giants (sufficient to make the sun absorb all the planets closer to it than Jupiter) and then after another billion years or so it will fly apart leaving a white dwarf.

If a star is bigger than the sun - say - 100x the mass - it will collapse into a neutron star. Here the collapse is so violent that all the atomic nuclei in the star loose their charge and become neutrons (hence the name).

Ten times bigger still are the stars which, in theory, spawn black holes. Here Stephen Hawkings (I believe) theorized that all black holes have a single mass - any thing that collides with them (and any excess mass at their creation) is slung off as high energy xrays.

Nothing - not even light, penetrates the "hole" It's slung off the exact opposite side.

Incidently, a black hole's gravity doesn't somehow grow due to it's new status. It's gravitational pull is the same as the star it came from and the event horizon is, usually, near where the surface of the star was in life.

(Disclaimer - I am not a scientist. Astronomy is one of my favorite hobbies but don't quote me as an expert).

 

[Tarrasque Wrangler]

I have heard that Time slows down as you move closer to a Black Hole.

Possibly. I know that time slows to a crawl if you have to spend a weekend in Fontana, CA.