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Astronomy/the future, then, is not black


Tom - thanks for your comprehensive reply to my colliding galaxy question. I'd like to follow up with a question about the consequences of what you said.

I had come to think that eventually, billions of years from now, an observer on earth would look up to see a black sky at night because all the stars would have moved away from our solar system with the expanding universe (assuming the earth isn't cooked by the sun by then).

From your description, it sounds like in fact we will always have the company of most of the stars we see now since they will remain with us, bound by gravity in our galaxy. In addition, if the Andromeda galaxy is moving toward us, then the interaction of the galaxies in collision would bring brand new stars into existence.

Then the end result universe-wide is many islands composed of many galaxies per island with each island group becoming more isolated from the other islands but still active star formation within the group. The take-away: the night skies will not go dark because of expansion.

Is this a valid assumption?

For a while, yes. But if the spacial expansion rate keeps accelerating (and we're not even sure that maybe the acceleration itself, may be accelerating)... then eventually not only galaxy clusters will "fly apart" from each other, but eventually the expansion rate becomes so great that individual galaxy's in the clusters will begin to move apart. And eventually stars will be ripped from individual galaxies, planets from solar sytems, then whole planets and stars ripped apart, then even every molecule and eventually every atom ripped apart.
As far as star formation, eventually you'll run out (use up all) of the gas hydrogen, therefore no new star formation.  So it's either a heat death or a Big Rip... take your choice... or maybe both.
Now if we could just learn how to reverse entropy and get it back to zero, then we could say
"Let there be light..."
Clear Skies,


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Tom Whiting


Astronomy has been my hobby/pasttime for over 50 years.  Currently own 3 telescopes, the largest of which is a 30 inch Newtonian truss Dob that is portable.I taught Astronomy/Meteorology at the University Level for 13 years before retiring in 1995. Being retired and home most of the time, I am able to answer all questions relatively quickly, unless it's a new moon weekend with good observing conditions.  No astrology questions please, or questions about alleged UFO picture identifications.


Experience: Astronomy has been my hobby and study for over 50 years. We currently now own a 30 inch portable telescope (Updated - Pennsylvania`s largest portable telescope). It can be seen on our website at: and also attend several regional starparties during the year, and have been on 5 total solar eclipse expeditions.

Organizations: President, Erie County Mobile Observers Group for over 15 years.

Publications: Wrote the "Over Erie Skies" newspaper article in our local newspaper for 11 years (1975-86).

Education: Masters Degree- Taught at the University level for 13 years. Retired 20 years -USAF Pilot - KC-135 with 180 combat missions;  Also Eagle Scout, Philmont staff 2 Yrs, Order of Arrow Lodge Chief, Ham Radio (inactive).

Awards: two discoveries: The mini-coathanger asterism in Ursa Minor (the little dipper) And the mini-ladle- another asterism in the bowl of Ursa Minor. Clients: Currently President of the ECMOG as mentioned above.

BS  Metallurgical Engineering Grove City College, PAMaster's Degree, Gannon University, Erie, PA Also retired USAF pilot, 20 years.

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