U.S. CitiesCity-Data Forum Index
Go Back   City-Data Forum > General Forums > Science and Technology > Space
 [Register]
Please register to participate in our discussions with 2 million other members - it's free and quick! Some forums can only be seen by registered members. After you create your account, you'll be able to customize options and access all our 15,000 new posts/day with fewer ads.
View detailed profile (Advanced) or search
site with Google Custom Search

Search Forums  (Advanced)
Reply Start New Thread
 
Old 06-09-2019, 07:55 AM
 
Location: Maryland
2,158 posts, read 729,163 times
Reputation: 4827

Advertisements

Quote:
Originally Posted by MisterEd51 View Post
To be more precise the rotational speeds of individual stars, gas and dust in galaxies. The speeds of each should be less the farther they are from the center of the galaxy. The observed values do not coorespond to calculated ones. The only way to make the numbers work is to introduce a lot more mass that extends out far beyond the edge of the galaxies. This extra matter has been called Dark Matter. Whether dark matter acually exists is up for debate until someone figures out what it is and finds a way to observe it.

It may be impossible to determine the true size of the universe because how far we can see is limited by "the visible universe". In other words the farthest we can see is the point where the observed speed is less than the speed of light. Beyond that the light emitted there will never reach us.

Another thing is that the farthur out we observe the further back in time the objects are. It is impossible to know what the whole universe looks like at at a given time.

Dark Energy has nothing to do with Dark Matter. Dark Energy was invented to explain why the universe is expanding at a rate faster than previously predicted.

In a way both Dark Matter and Dark Energy are like "fudge factors" to make the theoritical equations fit the actual observed data.
The video I posted shows images of the “last scattering surface”, the origin of the CMB, as I understand it. So according to that, we have seen right to the edge of our known universe and it is how estimates of its size (approximately 93 billion light years diameter) have been derived.

More...http://universeadventure.org/eras/era2-synthesis.htm
Reply With Quote Quick reply to this message

 
Old 06-10-2019, 03:04 AM
 
2,938 posts, read 1,118,090 times
Reputation: 1976
Quote:
Originally Posted by MisterEd51 View Post

It may be impossible to determine the true size of the universe because how far we can see is limited by "the visible universe". In other words the farthest we can see is the point where the observed speed is less than the speed of light. Beyond that the light emitted there will never reach us.
Since the observable universe represents our horizon, I doubt we would be able to ever determine the universe's true size. The universe may even have a curvature beyond that limit.

Quote:
Dark Energy has nothing to do with Dark Matter. Dark Energy was invented to explain why the universe is expanding at a rate faster than previously predicted.

In a way both Dark Matter and Dark Energy are like "fudge factors" to make the theoritical equations fit the actual observed data.
Dark Matter and Dark Energy appear to have the opposite effect. Dark Matter serves to explain why galaxies are held together instead of flying apart, whereas Dark Energy deals with the expansion of the universe and may be a property of space-time itself.

In the Big Rip scenario for the End of the Universe, Dark Energy will likely become so strong that Dark Matter won't be able to hold galaxies together anymore.
Reply With Quote Quick reply to this message
 
Old 06-10-2019, 05:40 PM
 
Location: Ohio
20,681 posts, read 14,654,220 times
Reputation: 16938
Quote:
Originally Posted by Milky Way Resident View Post
There’s an alternative theory that’s been thrown around, which is dark flow, and tries to incorporate dark matter and energy into a single phenomena.
I think they're trying to hard. There's a much simpler explanation, although I'll be damned if I know what it is. I'm partial to the theory that at larger scales, gravity works differently.

I just find dark matter/energy unbelievable. Particles are always moving. I just can't see them sitting in any one place for any amount of time. And, any matter in excess of 0°K should be giving off black-body radiation.

Quote:
Originally Posted by Milky Way Resident View Post
Yes, there’s a lot that we don’t know. For one, the actual Hubble constant is still being debated, with recent results contradicting previous findings.
I always viewed it as a "fudge factor" sort of like the gravitational constant.

Quote:
Originally Posted by Milky Way Resident View Post
The total universe may even be infinite. We still don’t even know if there is curvature to space-time.
Either the curvature exists, or it doesn't. I think if that question could be answered, it would help immensely.

Quote:
Originally Posted by Milky Way Resident View Post
It’s also been suggested that dark matter could be the imprint of another universe interacting with ours. I’m fascinated by the different multiverse concepts out there but they are in the realm of speculation.
Well, if that were true, it would seem to imply the laws of physics are the same in all universes, because we're not really seeing anything unusual.

Quote:
Originally Posted by Milky Way Resident View Post
Oh wow!! That’s a huge number. I was under the impression that most of our stellar neighbors were Red Dwarfs. As far as planets go, I think most cosmologists have come to terms with the fact that planets are rather common as they are a part of the natural formation of a star system.
It is true that Red Dwarfs are the most common star in the Universe. Most White Dwarfs are former Red Dwarfs or G/K-Class stars.

I don't believe Blue or White Giants have as many planets, because they consume so much material when they form. The smaller main sequence stars are likely to have far more planets than the larger stars.
Reply With Quote Quick reply to this message
 
Old 06-11-2019, 03:02 AM
 
832 posts, read 809,183 times
Reputation: 505
Let me put it another way. Conventional theories about our Universe are unable to explain some of the current data we have now. Right now Dark Matter and Dark Energy are just convenient terms made up to cover this. When the true causes are known to explain this the names that are given to these causes may be something other than Dark Matter and Dark Energy.
Reply With Quote Quick reply to this message
 
Old 06-11-2019, 07:44 AM
 
Location: Maryland
2,158 posts, read 729,163 times
Reputation: 4827
Quote:
Originally Posted by MisterEd51 View Post
Let me put it another way. Conventional theories about our Universe are unable to explain some of the current data we have now. Right now Dark Matter and Dark Energy are just convenient terms made up to cover this. When the true causes are known to explain this the names that are given to these causes may be something other than Dark Matter and Dark Energy.
True. But that’s also true of so much we “know”. We describe things verbally or mathematically but it is not an understanding of them. We call an electron a “thing” but it is a mathematical point charge and exists in probability states. We call a photon a particle but it exhibits wave behavior. We have positively charged “holes” ... and then there’s almost anything in the world of quantum mechanics.

We have constructed all manner of ways of communicating about things but it’s obvious our true knowledge of their nature is lacking and we’re left with mind numbing paradoxes.
Reply With Quote Quick reply to this message
 
Old 07-14-2019, 12:17 AM
 
4,255 posts, read 8,011,985 times
Reputation: 6034
Quote:
Originally Posted by LesLucid View Post
I’m a biologist, so forgive my ignorance of this field. Lawrence Krause gave a talk years ago which seemed to paint a picture of a fairly well settled view of the past, present and future of our universe. It’s a very entertaining video, which I’ve watched through several times. Do any folks here know whether this is still considered “current thought”? I realize the recent concern about faster than expected expansion of the universe could be a complication but, other than that, is this talk still considered mostly valid? I hope you enjoy the video. There is a significant portion discussing dark matter/energy.


https://m.youtube.com/watch?v=-EilZ4...ature=youtu.be
He is a great scientist and speaker, but too arrogant and dismissive for me. Here is a different view.


https://www.youtube.com/watch?v=zORUUqJd81M
Reply With Quote Quick reply to this message
Please register to post and access all features of our very popular forum. It is free and quick. Over $68,000 in prizes has already been given out to active posters on our forum. Additional giveaways are planned.

Detailed information about all U.S. cities, counties, and zip codes on our site: City-data.com.


Reply
Please update this thread with any new information or opinions. This open thread is still read by thousands of people, so we encourage all additional points of view.

Quick Reply
Message:

Over $104,000 in prizes was already given out to active posters on our forum and additional giveaways are planned!

Go Back   City-Data Forum > General Forums > Science and Technology > Space
Follow City-Data.com founder on our Forum or

All times are GMT -6. The time now is 10:04 AM.

© 2005-2019, Advameg, Inc. · Please obey Forum Rules · Terms of Use and Privacy Policy · Bug Bounty

City-Data.com - Archive 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35 - Top