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Comparing sizes starting with the moon





deanhills
Found this fascinating YouTube show (for me any way) comparing sizes of the planets and the big stars.

mazito
Is amazing, watched somo time ago but still want to see it again
deanhills
Right. I must have viewed it a number of times. Was quite fascinating to actually see the different sizes. I knew there were planets larger than earth but somehow psychologically one always thinks of earth, as the centre of the universe. Sort of shifted my mental paradigm quite a bit. Smile
Peterssidan
Yes, it is fascinating. Surprised I wonder if there is a limit to how big something can be. If it's big enough shouldn't the gravity turn it into a black hole or something?
kelseymh
Peterssidan wrote:
Yes, it is fascinating. Surprised I wonder if there is a limit to how big something can be. If it's big enough shouldn't the gravity turn it into a black hole or something?


The largest gravitationally-bound structures in the Universe are superclusters of galaxies -- that is, clusters of clusters of galaxies. A supercluster is more or less nothing: a huge volume of intergalactic space with several clusters of galaxies moving around in it.

For a gravitationally-bound object to turn into a black hole it must be dense. To form a black hole, you need a lot of mass concentrated into a very small volume, such that as gravity pulls the mass together it is strong enough to overcome, first, normal gas (temperature-based) pressure (stars); second, atomic structure pressure (solid planets); third, electron-degeneracy pressure (white dwarves); and fourth; neutron-degeneracy pressure (neutron stars).
silverdown
That is really fascinating, I always been interested in the moon since I was like 6.
truespeed
The final bit where it explained how long it would take a passenger plane to go around the largest star best gave the idea of its size,the same jet would take a couple of days to go around the earth but to go around the largest star would take 1100 years,that really brings home its size.
deanhills
truespeed wrote:
The final bit where it explained how long it would take a passenger plane to go around the largest star best gave the idea of its size,the same jet would take a couple of days to go around the earth but to go around the largest star would take 1100 years,that really brings home its size.
That bowled me over as well. We seem to be in a time and space warp here. Things could be relative.

Quote:
What does this mean for the Captain Kirk and his team? The closer an object gets to the speed of light, that object actually experiences time at a significantly slower rate. If the Enterprise were traveling safely at close to the speed of light to the center of our galaxy from Earth, it would take 25,000 years of Earth time. For the crew, however, the trip would probably only take 10 years.

http://science.howstuffworks.com/warp-speed2.htm
sanscha
This reminds me of the classic short film Powers of Ten.

www.youtube.com/watch?v=0fKBhvDjuy0

It looks a bit dated now but is still very good. And interesting if you're into the history of these sorts of videos.
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