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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#8,861
Galu said:
The "dread" of light? Or are you afraid of the dark, Bonsai? 😀

The Michelson-Morley (M-M) experiment was devised to study the effect of the postulated Ether on the speed of light.

When the Earth moves though the Ether it should feel a resistance similar to the air resistance a bike rider feels when moving through the air.

This resistance to the Earth's movement was called the "Ether wind".

It was thought that a beam of light passing sideways across the Ether wind and another beam travelling in the direction of the Ether wind would take different times to travel the same distance.

To the astonishment of M-M, there was no difference in the journey times of the two light beams.

To M-M, the null result indicated that either there wasn’t anything called Ether or the Earth must be dragging a blob of Ether around with it, in which case there wouldn’t be any Ether wind to detect.
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It’s quite funny to look at the tittles of some of the pre-SR books on the subject. One I saw was ‘The Luminiferous Ether’ by some British lord. Quite quaint given what we know now. I guess it’s like evil spirits being responsible disease etc.
 
#8,863
Bonsai said:
Here is a fantastic video on Tensors by Daniel Fleisch.
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Thanks, Bonsai. That's the kind of explanatory video I like - short and with no complicated mathematics! 😀

Some of the phrases in the video are in accord with what I read when googling for information on Tensors.

"Vectors are members of a wider class of objects called Tensors."

"Vectors are Tensors of rank 1 and Scalars are Tensors of rank 0."

I understood the explanation of rank 2 Tensors, but was beginning to struggle when it came to the rank 3 Tensors that represent three dimensional space!

To paraphrase Daniel Fleisch, the power of Tensors lies in the fact that they allow observers in different frames of reference to agree on the facts of the universe.

That summarisation is sufficient for my needs! 😎
 
#8,864
mchambin said:
Lies from lobbyist like Greenpeace proved to be bribed to agitate so.
The alternative does exist in France that has an electricity mix 70% nuclear with little depandency of Russian gaz.
All it takes is a stop to the political ecology non sense with wind turbines at 23% availability giving zilch 77% of the time, then asking to supplement with gaz and coal, a GIEC disaster.
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I would be cautious bringing up the Greenpeace and France connection 😉
 
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#8,871

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#8,873
The most recent news from the JWST is that its Mid-Infrared Instrument (MIRI) has been cooled to just a few degrees above absolute zero.

This was achieved with the help of an electrically powered cryocooler, which is a remarkable piece of technology in its own right.

https://www.jwst.nasa.gov/content/about/innovations/cryocooler.html

Since MIRI detects longer infrared wavelengths than Webb's other three instruments it needs to be even colder than them.

Now that MIRI is at operating temperature its calibration can take place alongside the calibration of the other three instruments.

Webb’s first science images are expected this summer.
 

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#8,874
I understand that in the lab, scientists have got to within a few millions of a degree of absolute zero. One of the comments about the achievement was that it was probably the coldest temperature in the universe - Assuming of course there are no other bipedal ape-like creatures out there doing the same sort of stuff.

Astounding.
 
#8,877
Bonsai said:
I understand that in the lab, scientists have got to within a few millions of a degree of absolute zero. One of the comments about the achievement was that it was probably the coldest temperature in the universe - Assuming of course there are no other bipedal ape-like creatures out there doing the same sort of stuff.
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Like ice aliens? 😎
 

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