What is the Universe expanding into..

Do you think there was anything before the big bang?

  • I don't think there was anything before the Big Bang

    Votes: 56 12.5%

  • I think something existed before the Big Bang

    Votes: 200 44.7%

  • I don't think the big bang happened

    Votes: 54 12.1%

  • I think the universe is part of a mutiverse

    Votes: 201 45.0%
  • Total voters
    447
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I did set my alarm clock up this morning for the Comet, but it was grey and raining at 5AM. 😡

Perused diyaudio.com for any interesting crossover action. Encountered an interesting glitch in the 6AM backup. It was still going on at 06.07 AM... 😕

Whatever was that guy reading so absorbedly? Thank Goodness the woman remembered to press the right button. Someone has to take charge. 😀
 

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My wife frequently pushes my buttons! 😀

P.S. I bet that guy is reading the horse racing form sheets! 😉
 

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Has China's Yutu 2 rover spotted an alien obelisk on the Moon's horizon?

Or is it simply a large cube-shaped boulder which has been excavated by an impact event?

It'll take 2 to 3 Earth months for the rover to get closer for a better look, so don't hold your breath! 😉
 

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I was reviewing all, well many, of the links on WIKI on gravity.
I did not know:
Gravity travels at the speed if light. To my logic, nature liking to take the easy way out and re-use things, implies a particle and force carrier. Boson and Lepton.

I did not know the Plank constant was not a limit, but a handy value for calculation
This implied to me no limit on smaller things. This gives me support of the various string theories.

I did not understand space-time may not be real, but just a brilliant tool to explain observation. Just as dark mater and dark energy, cold, warm, hot, etc., are a way of explaining observation, but not necessary, although a WIMP, even not in favor, seems to have a lot going for it.

I did not understand the 25 or so theories of gravity in how a black hole may have multiple horizons. How some theories have an expanding universe, but some can explain the dimming of the super nova's without acceleration.

Is the speed of light, or for that matter, any wave, at the event horizon zero, or is it a limit approaching zero?
 
Galu said:
Has China's Yutu 2 rover spotted an alien obelisk on the Moon's horizon?

Or is it simply a large cube-shaped boulder which has been excavated by an impact event?

It'll take 2 to 3 Earth months for the rover to get closer for a better look, so don't hold your breath! 😉
Click to expand...

I smell aliens.
 
tvrgeek said:
I did not know: Gravity travels at the speed if light.
Click to expand...
You bring up some interesting concepts and relationships.

In Newton's theory, gravity propagates instantaneously. There is no "light travel delay" or "propagation delay" in Newtonian gravity, otherwise its predictions of the orbits of the planets would not match astronomical observations.

In Einstein's general relativity, gravity propagates at the speed of light. However, in weak fields the propagation delay is almost exactly cancelled and general relativity very nearly produces the Newtonian result.

We can delve into the details here: Does Gravity Travel at the Speed of Light?

tvrgeek said:
I did not know the Plank constant was not a limit, but a handy value for calculation
Click to expand...
The Planck constant (h) simply relates the energy (E) of a photon to its frequency (f). It is the constant of proportionality in Planck's famous equation, E = hf.

It is not to be confused with the Planck length which is a unit of length defined in terms of the Planck constant (h), the speed of light (c) and the gravitational constant (G).
 
Chinese experiment measured the speed of gravity just a couple years ago. Of course LIDOS has measured gravitational waves.

Just was re-watching the various U-Tube bits on Feyman. The casual interviews on thinking are worth pondering. I happen to be a very visual thinker, possibly developed by my dyslexia which makes memorization very difficult. His observations on which facilities we use rang home. I failed at mathematics as I could not memorize sufficient trig substations quickly enough even though I could visualize the direction an equation was headed.

His lecture on his experience at Los Almos is informative as far as history, but very light and informative about people.

The answer to everything is 1010102, but only 10 kinds of people understand it.
 
tvrgeek said:
Is the speed of light, or for that matter, any wave, at the event horizon zero, or is it a limit approaching zero?
Click to expand...

I read there is a possibility that, in the time reference frame of a distant observer, the apparent speed of light will change in a gravity field and, in particular, go to zero at an event horizon.

This appears to be a hypothesis which attracts great discussion, but its understanding is beyond my mathematical ability!

See the "Interpretations of general relativity" section here: Variable speed of light - Wikipedia
 
I can clearly see Venus (which is at its most brilliant tonight) just above the crescent Moon - one of your better efforts I must say, Steve! 😎

During the rest of the week, the crescent moon will pass by Venus, and then Saturn and Jupiter, as it rises slowly in the night sky.

So, I'm looking forward to, not just a trio, but a quartet from you!
 
Galu said:
I read there is a possibility that, in the time reference frame of a distant observer, the apparent speed of light will change in a gravity field and, in particular, go to zero at an event horizon.

This appears to be a hypothesis which attracts great discussion, but its understanding is beyond my mathematical ability!

See the "Interpretations of general relativity" section here: Variable speed of light - Wikipedia
Click to expand...
I see the article discusses "various alternative theories" ...

As I understand the mainstream theory, the speed of light is a "true constant" but that time SLOWS DOWN under higher gravity, and effectively stops at the event horizon.* Thus, light goes at the same speed, but since time slows down near the event horizon, it gives the APPEARANCE of light slowing down.

* But then if time stops then everything stops. How does matter CROSS the event horizon??? Perhaps it's just that the event horizon expands to include the extra mass that's immediately surrounding it? There are conundrums such as this which are not explained by what I've read, and I'm hoping I don't need to get a physics degree just to find out a few details like this.
 
benb said:
But then if time stops then everything stops. How does matter CROSS the event horizon???
Click to expand...
Although time appears to stop from the perspective of an outside observer, it doesn't stop from the perspective of the matter crossing the event horizon.

It is known as the "Time-Stopping Paradox".

The paradox is resolved by realising that, as infalling mass enters a black hole, the event horizon gets larger. That means the infalling mass can easily make it inside the event horizon.

I asked Ethan! Ask Ethan: Does A Time-Stopping Paradox Prevent Black Holes From Growing?
 
Black holes are not magical . They are just supermassive chunk of matter . Nothing more nothing less . Matter so dense . There is no space between two particles . Space means actual space . Which means . No field electric magnetic or combined can pass through actual blackhole . Because there is no space . Only gravity created by blackholes as due to lack of space in the blackhole exist . To be fair we all no matter what we try cannot fill space to its maximum . Only blackhole can achieve it
 
But that assumes particles exist. Do they or are they just how we observe and describe? No space assumes a solid and a dimension, which assumes a fundamental particle. Then we get to the question of shape. Unless something that packs without space, i.e. cube, dodecahedron etc., you can't pack without space. Or are you suggesting black holes contain a singularity and the observable dimension is just matter collapsing but still having dimension? Then the questions becomes how much energy can be contained in a singularity?

Let us be clear between a current description best guess and a fact. Even the rate of expansion is a best guess and mostly accepted, there are other factors that could explain the brightness and red shift of distant supernovas. We just don't know enough about gravity. We observer quantum entanglement but have absolutely no idea how it works.
 
Actually, by math either a point or disk, depending on spin, but both with infinite curvature, so no space. But, this is an example where it approaches zero. Infinity is just as undefined dividing by zero. They are only our abstract way of looking at them.

Point is, we do not know anywhere near enough about gravity ( some 25 or so theories) to make this assumption into a fact. I am not saying it is not true, but not saying we should not accept it as fact yet.
 
Quoting from A Briefer History of Time by S.Hawking with L. Mlodinow:

"General relativity must be altered. By predicting points of infinite density - singularities - classical (that is, non-quantum) general relativity predicts its own downfall."
Click to expand...
The reason that all experiments thus far have supported general relativity is because all the gravitational fields we normally experience are weak.

In the presence of the strong fields caused when matter and energy are squeezed into a black hole, the effects of quantum theory should be important.

A quantum theory of gravity would open up a new possibility in which there would be no singularities at which the laws of physics break down.
 
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