The ElectroMagnetic Multiverse.

originally posted by: Direne
Can we have light without stars? Sure. Repeat the above experiment: an empty universe, get into it one star. Photons will propagate from the star. Remove the star: photons are still traveling away from it. For eons. What's what you get? A universe with no stars filled with light.

Right. Of course stars don't get physically removed, but they do run out of fuel like our sun will do in about 5 billion years, so this is a very real scenario where we commonly see light from stars in distant galaxies, which ran out of fuel long ago.

The problem with the OP is his inability to understand that effects can persist in time long after the cause has disappeared. Therefore, explaining to the OP that gravity is a property of spacetime, and not of matter, is totally impossible. Most likely this has to do with his inability to conceive a Universe devoid of matter, which means he is also unable to understand the Big Bang theory where we first have a radiation age without matter. As temperature decreases, radiation condenses due to gravity, and only then matter appears. Hence: first comes gravity, only in the end matter appears. Want it or not, that's how things work.

I thought about bringing the Big Bang model up earlier, but didn't because I was trying to keep the explanations simple like in the minutephysics video, and the big bang model is rather complex. But since you brought it up, yes that's another counter example to this claim in the opening post saying that without matter there is no gravity:

"Without Electromagnetism nothing would exist. Atoms wouldn't be able to bond and matter as we know it would never exist. Without matter there is no gravity."

Specifically, the period after the Big Bang which contradicts that is called the "Photon Epoch":

Photon Epoch: Between 10 seconds and 370,000 years after the Big Bang...

After most leptons and antileptons are annihilated at the end of the lepton epoch, most of the mass-energy in the universe is left in the form of photons...Therefore, the energy of the universe, and its overall behavior, is dominated by its photons.

So from 10 seconds to 370,000 years after the big bang, the universe was dominated by massless photons, which had gravity. The electromagnetic force existed, but was insufficient to overcome the high temperatures and energetic photons which prevented electrons and protons coming together to form atoms. If an electron did briefly bond with a proton, the bond didn't last because of the high temperatures and all the high energy photons.

There might be people who question how we could know what happened so long ago. It's not just what our models show, but when when the universe had cooled enough for atoms to start forming at about 370,000 years old, that's when the cosmic microwave background (CMB) was created, and we can still see that CMB today.

originally posted by: ElectricUniverse
a reply to: Arbitrageur

The only misconception keeps on coming from you. The only problem with Newton's law of universal gravitation is the matter/mass that we cannot observe.

I just told you two very specific problems with Newton's model, but you ignore those and say the "only problem" with Newton's model is something else. That's false. How about acknowledging the other problems I mentioned:

1. You can't explain the precession of the planet Mercury with Newton's model. Einstein's model explains it.
2. The modern GPS system relies on calculations from Einstein's general relativity to work, it won't work under Newton's model.

There are other issues I didn't mention with Newton's model, such as it can't explain the results of Gravity Probe B, but Einstein's model explains the results:

NASA's Gravity Probe B Confirms Two Einstein Space-Time Theories

It is true that so far the known mass of the universe can account for a percentage of gravity observed. But quantum mechanics has a solution to that problem, and that solution is that gravity from the mass in other dimensions/parallel universes also affects our own universe.

In fact this leak of gravity from the mass in other dimensions has been observed already.

You have a history of making claims, and then posting sources that don't support your claim. In this case not only does that video not support your claim, it actually contradicts it, at time index 6:25, where Matt says:

"Although we've never detected these extra dimensions, they seem a promising potential solution to unifying gravity with the other forces."

So your video directly contradicts your claim that the extra dimensions have been observed, when it says we've never detected them. Maybe someday we will.

When you refer to "the mass in other dimensions/parallel universes", you seem to be conflating those two different ideas of other dimensions and parallel universes, but again the video you posted makes it clear they should not be conflated. Matt talks about LIGO measurements which confirm the extra dimensions, if they exist, can't be large, so they would have to be tiny, meaning they aren't anything like parallel universes. They would be parts of our universe on a scale too small to see.

Then you made another string of posts where you post some sources and you also don't seem to understand what those sources are saying since your claims don't match up with the source. I don't have enough time to correct all your misunderstandings, but you need pay more attention to what your sources are actually saying and try to stop making claims your sources don't support. Here is one of those posts.

originally posted by: ElectricUniverse
BTW, there is also time crystals which could also explain the missing mass problem and which Quantum Mechanics can answer.

Crystals that repeat their patterns not only through space, but through time. As researcher Norman Yao explains it, these crystals are showing a new phase of matter, and one of the first examples of non-equilibrium matter. Physics is catching up to Quantum Physics.
...

Scientists Create A New Kind Of Matter: Time Crystals

I could find absolutely nothing in the sources you linked which support your claim that "there is also time crystals which could also explain the missing mass problem and which Quantum Mechanics can answer." The source links to a Popular Mechanics article that talks about time crystals, but it says absolutely nothing about how they might explain the "missing mass problem", or can I assume you're talking about "dark matter" when you refer to "missing mass problem"? In either case, it doesn't say or even imply a solution to any missing mass issue, did you read it?

originally posted by: Direne

A theory where gravity is a result of a gradient in ε0/μ0.

a reply to: graysquirrel

Only that, were that the case, you are implying there would be no gravity in a universe without charged particles.

Not if the E and B fields are that of electromagnetic radiation.

Anyway, a little tidbit of information since we have been talking about Einstein. Did you know that Einstein was born Autistic? He was born with Asperger syndrome. In fact he didn't speak a single word since he was a child to his early adulthood. One day his mother got so mad with him that she took him by the shoulders shook him violently and yelled to him to say something.

If it was up to today's "society" Eintein would have been murdered in the womb...

Same with Stephen Hawkins, he was born with ALS but it started to develop when he was an adult. He would have also been murdered by today's standards...

Imagine that... Two of the most brilliant men the world has ever had would have never been born and would have never contributed what they contributed to the world if their mothers had been so selfish as to murder them in the womb because of their illnesses...

What would the world be today if their mothers had decided to murder them in the womb because of those illnesses? We wouldn't have Einstein's General Theory of Relativity. The world most famous equation, E = MC^2 would have never been invented/found.

The theory of Photoelectric Effect, which was key in the development of Quantum Theory would have never been invented/found...

If Hawkins had been murdered in the womb his collaboration with Roger Penrose on gravitational singularity theorems would have never had occurred. Hawkins radiation which was the theoretical prediction that black holes emit radiation would have never been invented/found.

Hawkins achievement in the union of the general theory of relativity and quantum mechanics wouldn't had occurred, etc, etc...

originally posted by: ElectricUniverse
Anyway, a little tidbit of information since we have been talking about Einstein. Did you know that Einstein was born Autistic? He was born with Asperger syndrome.

Maybe, I've seen those claims and they may or may not be accurate but no doubt he was an extremely focused individual and didn't have as much "balance" as a more ordinary person might have.

In fact he didn't speak a single word since he was a child to his early adulthood.

"citation needed".
He may have been a "late talker" meaning he was four or five before he started speaking words, but early adulthood sounds completely wrong.

Same with Stephen Hawkins, he was born with ALS but it started to develop when he was an adult. He would have also been murdered by today's standards...

I don't know why people have so much of a problem spelling the name of Stephen Hawking, but you're not the only one who calls him Hawkins. Almost like some people can't seem to get the Berenstain Bears spelled right and think it was spelled Berenstein Bears.

What would the world be today if their mothers had decided to murder them in the womb because of those illnesses? We wouldn't have Einstein's General Theory of Relativity. The world most famous equation, E = MC^2 would have never been invented/found.

E=mc² is not the correct equation anyway, which is at the heart of why so many people have misconceptions about photons not having gravity (and about relativistic mass). The correct equation has a momentum term, which is what really came from Einstein. What makes E=mc² incorrect is it has the momentum term removed and if momentum is involved (as it is with light, and particles in accelerators like the LHC), you won't get the right answer using E=mc²

So, another common misconception is that "world most famous equation, E = MC^2" is a correct equation. It's not correct or at least not complete since it's missing the necessary momentum term, and this is really not controversial at all. Scientists agree on this point, I made a thread about it:
Science Quiz #2: Is E=mc² right or wrong?

Whether autism can successfully be screened in the womb is rather questionable, but even if it was possible, if the parents knew that autistic children can turn out to be geniuses like Einstein, then I'm not sure why they would want to terminate a pregnancy for that reason. 90% of parents terminate pregnancies identified with down syndrome though, and I don't think that will adversely affect the number of geniuses in the population.

a reply to: ElectricUniverse

No need to imagine Einstein's mother going through an abortion. Suffices to figure out what would had happen if he wouldn't had escaped from the Nazis. This also applies to Hawkings, were he to live in Eintein's time.

Anyway, I want to make two clarifications:

- the correct term is Hawking-Bekenstein radiation. it was Bekenstein who called Hawkings' attention on the fact that, if thermodynamics must hold, of necessity a blackhole must radiate. They together worked out the maths.

- Hawkings and Penrose collaboration was intimate and crucial indeed, but the crucial one was Hawkings and Ellis, when they together published the seminal work titled The Large Scale Structure of space-time. That was in 1973. It was Ellis who developed most of the maths. In Chapter 5, page 117 ((Exact solutions) you can find a reasoning about Universes consisting of just radiation and no matter fields. You can also be delighted with the mathematical description of CTCs (closed-timelike curves) which triggered all the hey-day claims about time travel.

Finally, if you wish to know how many possible Universe configurations exist, I would recommend you Exact solutions of Einstein's field equations, where Kramer, Stephani, MacCallum, and Herlt list all the possible universes described by Einstein's field equations (that is, those for which we have found an exact solution).

Both books are included in the Cambridge Monographs on Mathematical Physics. Do not be detered by the maths as the guys writing the books have been kind enough to include a conclusion paragraph in plain language for each of the solutions.