Across the Universe

Updated 1 Nov 26

I have recently come across a couple of items online based on the elapsed time for occupants of a spaceship accelerating at 1g to traverse cosmic distances.

First a video, Something Terrifying Would Happen If a Spaceship Constantly Accelerated at 1G Through Space..., on YouTube channel ExoSci, posted 27 Sept. The audio refers to an article, but which? Could it be this one, How long does it take to travel through the Universe at 1g?, posted by Ethan Siegel on Big Think just the day before? Too soon surely, but perhaps Siegel had posted something similar earlier. Astonishingly, he concludes: All destinations within the reachable Universe are achievable in 25 years, maximum. Of course, that is for the occupants of the spaceship and is a consequence of relativistic length-contraction over the cosmic distance travelled.

For some reason, this made me remember an amazing fact I first came across many years' ago - if the Earth were to be squeezed as a cylinder of 1 square metre cross-section (maintaining its density), its length would equal the diameter of our galaxy! 

Let's check:

• the radius of the Earth is 6.4 million metres
• therefore its volume is ~ 10^21 cubic metres
• with a cross-section of 1 square metre, the cylinder would have a length of 10^21 metres
• one light year is about 10^16 metres, so that makes the squeezed Earth 100 thousand light years in length
• our galaxy is believed to be 100 to 150 thousand light years across, so the assertion is roughly correct!

Why stop there? What if we were to reduce the cross-section of the cylinder to 1 square centimetre? There are 10,000 (100 squared) of those in a square metre, so the squeezed Earth would now be 10,000 times longer than before, so 1000 million, or 1 billion light years in length!

What if we were to reduce the cross-section of the cylinder further to just 1 square millimetre? There are 100 (10 squared) of those in a square centimetre, so the squeezed Earth would now be 100 times longer than before, so 100 billion light years in length! That's about the diameter of the observable universe!

(We could also dial back and increase the cross-section to 1 square kilometre, in which case, the cylinder would stretch to about one millionth the diameter of the Milky Way, i.e. to one tenth of a light year, about the distance from the Sun to the inner edge of the Oort Cloud).

Conclusion: the (observable) universe is vast, but not unimaginably vast. (And 'just' a million Milky Way galaxies placed side-by-side will span it).

Heavy breathing from the woods!

More strange noises to report! They are like this and come from nearby woods at night. They have been heard on many occasions - quite un-nerving the first time! Presumed to be made by stags as there are deer there. No specific time of year, as I have several recordings dated January to June.

(The recording may be on the quiet side if played online, in which case, download it and try again).

Nocturnal screeching!

Recording made around 11 pm towards the end of June this year, just one of several occasions when there have been these screeching sounds outside our house. I don't recall seeing anything, perhaps just catching the occasional fluttering as well. I'd heard such sounds in previous years and had always thought that they were made by bats, while also being fully aware that their echo-location uses ultrasound. Once disabused of the notion that bats also make audible sounds, I surmized that these must have been made by birds instead, but which ones? I was amazed that the BirdNET app identified them as from Tawny Owls! We often hear typical owl hoots, living close to several woods. Almost certainly though, these sounds are made by owlets calling out to be fed.

(The recording may be on the quiet side if played online, in which case, download it and try again).

Non-magnetic stainless steel!

I hate to throw out old motors etc. without first trying to retrieve parts like wire or magnets. The item I was attempting to dismantle was an old water pump for a garden water feature. It was completely sealed and looked to be difficult to break into, so I didn't try, but I did save a magnet which was outside the main body. It was dirty, so I washed it and then placed it onto the draining board section of a stainless steel sink. I expected it to snap into place, but nothing happened, which was a great surprise! It turns out that the crystalline structure of austenitic stainless steel renders it non-magnetic. Amazing to have discovered something so basic so late in life!