What is the Universe expanding into..

[Bonsai]

It took Einstein 10 yrs to workout special relativity and the same again for General relativity. The gears of his mind were already grappling with the SR problem when he was 16 and GR finally came when he was 35.

There is a very nice 2 hour lecture on GR in YouTube by DrPhysicsA where the field equations are derived. I watched the whole thing and found it humbling to say the least. How someone can unravel SR and then GR I found quite astounding. That’s true genius for you!

Einstein Field Equations - for beginners! - YouTube

 

[system7]

Tin Foil Hat.

Amazing. Boffins have found a use for Cosmic Rays and muons in particular! 😎

They are apparently highly penetrating, able to go through metres of rock:

Muon tomography - Wikipedia

A huge chamber was discovered in the big pyramid using the natural cosmic ray flux. Which amounts to one muon per second on your hand.

The Big Void

In 2017, scientists from the ScanPyramids project discovered a large cavity above the Grand Gallery using muon radiography, which they called the "ScanPyramids Big Void". Key was a research team under Professor Morishima Kunihiro from Nagoya University that used special nuclear emulsion detectors.[43][44] Its length is at least 30 metres (98 ft) and its cross-section is similar to that of the Grand Gallery.

Great Pyramid of Giza - Wikipedia

 

[system7]

I suspect the Egyptologists are hoping some ancient treasure is located in the void. I have visited the Pyramids as it goes. My brother fainted in the heat. Only time I ever saw him wimp out.

Hmm, enjoying the lecture on General Relativity so far:

Einstein Field Equations - for beginners! - YouTube

Taking a break at 14:45 as suggested by the lecturer, but so far so good.

I watched the Susskind lectures, but fell on my backside with the Ricci Tensor and Ricci flatness. 😱

 

[Galu]

Amazing. Boffins have found a use for Cosmic Rays and muons in particular!

It's even more amazing that muon imaging was first used in the fifties and I've never heard of it!

 

[Disco-Pete]

Einstein wrestled with the same question as yours: How was it possible for two people to see the same event in such totally different ways i.e. to have two such totally different perspectives?

The answer he arrived at was simply that time can beat at different rates throughout the universe, depending on an object's speed.

From the perspective of a stationary person watching your rapidly retreating rockets, time in the each of the rockets would appear to slow down compared to his own clock which would be beating normally.

So, from that person's perspective, the rockets do not appear to separate at as high a speed as you might think.

According to Newtonian physics, your rockets, each moving at around 66% of c should be separating at 132% of c. But Einsteinian physics shows that distances in the direction of travel are shortening and time is slowing down so that the sum of these velocities is actually 92% of c.

I can honestly 'kind of grasp' that. But is that "reality"? Or merely illusory observation/perspective?

 

[Galu]

I have visited the Pyramids as it goes. My brother fainted in the heat.

I got lost and couldn't find my mummy! 😀

 

[Disco-Pete]

It took Einstein 10 yrs to workout special relativity and the same again for General relativity. The gears of his mind were already grappling with the SR problem when he was 16 and GR finally came when he was 35.

There is a very nice 2 hour lecture on GR in YouTube by DrPhysicsA where the field equations are derived. I watched the whole thing and found it humbling to say the least. How someone can unravel SR and then GR I found quite astounding. That’s true genius for you!

Einstein Field Equations - for beginners! - YouTube

Thanks, I will definitely watch that. He must have spent an awful lot of time by himself

 

[N101N]

You have to think about the passage of time with each object and their velocity. At 2/3 c, the speed is relativistic and time will have slowed down for both objects from their perspective, so they won’t hit each other at 4/3 c, but the figure quoted earlier per the math.

Such a pompous nonsense.

 

[Disco-Pete]

I got lost and couldn't find my mummy! 😀

She was all wrapped up with something else

 

[Disco-Pete]

Such a pompous nonsense.

Probably

 

[Galu]

But is that "reality"?

Special relativity does decribe reality, and has been widely tested over the past 100 years or so.

No repeatable experiment has been found that disproves special relativity.

Would you bet your life on special relativity being real? Anyone who relies on GPS in bad weather may be doing just that!

https://homepages.abdn.ac.uk/nph120/Cosmol/specrel.pdf

 

[N101N]

Discopete,
you think too much and that is going to be your downfall. Haven't you heard the (in)famous expression: don`t ask questions, shut up and calculate.
Cosmic rays travel at the is same speed regardless of mass and frequency. That`s called relativity.

 

[Galu]

Thanks, I will definitely watch that.

Note that the lecture recommended is on General Relativity (GR), which is Einstein's theory of gravity.

You need to start by understanding Special Relativity (SR).

 

[Disco-Pete]

Discopete,
you think too much and that is going to be your downfall. Haven't you heard the (in)famous expression: don`t ask questions, shut up and calculate.
Cosmic rays travel at the is same speed regardless of mass and frequency. That`s called relativity.

Duly noted

 

[Galu]

Amazing! N101N has succeeded where others have failed!

Don't ask questions, shut up and calculate - the most sensible contribution yet! 😉

 

[Disco-Pete]

Note that the lecture recommended is on General Relativity (GR), which is Einstein's theory of gravity.

You need to start by understanding Special Relativity (SR).

I'm quite familiar with the abbreviations thank you very much, I simply prefer the long form.

 

[mchambin]

Would you bet your life on special relativity being real? Anyone who relies on GPS in bad weather may be doing just that!

https://homepages.abdn.ac.uk/nph120/Cosmol/specrel.pdf

I can't help but comment on GPS.
There are two relativistic corrections upon the extremely accurate inboard satellite clocks, one from the speed of the moving clocks, the other from low gravity. Without these taken care of, the final user's location would be so bad, the GPS would be hardly usable.
GPS is full choke of very interesting stuff in many fields of engineering and technology.

 

[MITsound]

Okay, I get that. But is perspective reality?

Yes. The observer effect is noted in the double slit photon experiment. Perspective changes everything it observes. If a photon can exhibit or reflect the affect of being observed, are its characteristics restricted to those of observed and unobserved? Are being both a particle and wave really different, or just being energy, one more expanded than coalesced? Is energy really released by a nuclear explosion, or is it merely converted back to energy, an expanded form of matter. Can energy be reacquired from someplace else? I still can't get my thoughts around light slowing down in a denser medium than vacuum, and then accelerating after re-entering vacuum, without transition. Does it reacquire energy from somewhere to accelerate to full speed?
😯🤯🤔

 

[Disco-Pete]

I can't help but comment on GPS.
There are two relativistic corrections upon the extremely accurate inboard satellite clocks, one from the speed of the moving clocks, the other from low gravity. Without these taken care of, the final user's location would be so bad, the GPS would be hardly usable.
GPS is full choke of very interesting stuff in many fields of engineering and technology.

"Chock Full o' Nuts is the heeeavenly ISS"
😛

 

[Bonsai]

Such a pompous nonsense.

Of course you’re quite entitled to your opinion but you could go one better and give us your explanation.