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Dark Energy?

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16 years 4 months ago #64254 by Euronymous
Replied by Euronymous on topic Re: Dark Energy?

75% is a lot of nothing we can see, or not see. Gravity and it's effects can be seen - and tested.


Well the thing is, gravity is still a theory. There are plenty of scientists who say gravity doesn't exist at all. There are also plenty who say dark energy doesn't exist. But the gist of it all is that dark energy seems to go against gravity and causes the universe to expand. It's all still a mystery because we're just a basic version of the human species, we don't really know much, we just happened to be born in a very unfortunate time in history where we are sort of in the middle of understanding. Maybe in a few thousand years people will have a lot more knowledge and understanding, with less theories and more facts.

Celestron C8-N (200mm reflector)
Carl Zeiss 10x50's
-Amateur Astronomer, photographer, guitarist, and beer drinker-

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16 years 4 months ago #64256 by voyager
Replied by voyager on topic Re: Dark Energy?

75% is a lot of nothing we can see, or not see. Gravity and it's effects can be seen - and tested.


Well the thing is, gravity is still a theory. There are plenty of scientists who say gravity doesn't exist at all. There are also plenty who say dark energy doesn't exist. But the gist of it all is that dark energy seems to go against gravity and causes the universe to expand. It's all still a mystery because we're just a basic version of the human species, we don't really know much, we just happened to be born in a very unfortunate time in history where we are sort of in the middle of understanding. Maybe in a few thousand years people will have a lot more knowledge and understanding, with less theories and more facts.


OK, gravity is not a theory, it's a fact. There is gravity.

Our explanation of that fact is of course theoretical but those theories have stood the test of verification very well. For something to get the honor of being a scientific theory it needs to be very thoroughly tested.

Our current understanding of gravitation probably isn't the whole truth, just like Newton's wasn't the whole truth, but it contains a lot of truth. Within the limits of our ability to test it our theory of gravitation works.

There have been some attemtps to explain the bigger gravitational picture without reverting to Dark Matter by attempting to modify the laws of grviation (MOND) but they have not done well.

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16 years 4 months ago #64271 by Euronymous
Replied by Euronymous on topic Re: Dark Energy?

OK, gravity is not a theory, it's a fact. There is gravity.

Our current understanding of gravitation probably isn't the whole truth, just like Newton's wasn't the whole truth, but it contains a lot of truth. Within the limits of our ability to test it our theory of gravitation works.

There have been some attemtps to explain the bigger gravitational picture without reverting to Dark Matter by attempting to modify the laws of grviation (MOND) but they have not done well.


By me saying gravity is still a theory, I mean that what we see it as may be completely wrong. We see gravity as an isolated force that caused objects of mass to attract one another. What if one of the dozens of other theories such as the Kaluza–Klein theory is correct and gravitational force is combined with electromagnetic force? Then gravity would not exist, it would be a completely new force that we could not call gravity as it is a totally different force than that which we currently define as gravity.

Our explanation of that fact is of course theoretical but those theories have stood the test of verification very well. For something to get the honor of being a scientific theory it needs to be very thoroughly tested.


Thats the whole point of why some people question gravity. Because it can be seen to have no effect in various environments. Then why does it have effect in other environments? If we can't explain everything then it can only still be seen as a theory albeit a very strong one. There is still a chance that the force does not exist at all and it is something completely different, some other form of energy we have yet to discover. There are plenty of scientists who actually dispute the entire existence of gravity, never mind it being combined with other forces, for example some say objects are pushed and not pulled. That wouldn't just change the theory of gravity, that would be a whole new force, rejecting gravity for a new force, seeing as gravity involves a pull. And because of that, it's still a theory and not fact.

What we can say is a fact is that there is some sort of force that in some occasions has an influence on objects in some sort of way involving movement. We can't say that gravity is the fact, seeing as it has a definition and therefore all the clauses that definition hold must be true.
So yes, fact, there is a force. Theory, the force is gravity. Could be something else.

Celestron C8-N (200mm reflector)
Carl Zeiss 10x50's
-Amateur Astronomer, photographer, guitarist, and beer drinker-

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16 years 4 months ago #64273 by dmolloy
Replied by dmolloy on topic Re: Dark Energy?
Well, the question is: does gravity work, or does earth suck... 8-)

The reason I really asked the original question was that I am not convinced we need to create dark energy to explain the behaviour of the observed universe. Gravity works just fine for me. I think that something in the nature of mass and the early universe might explain why and when the universe seemed to expand faster. who knows, maybe the early universe had a density that would not allow faster expansion

Nurse....my medicine please..... :x

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16 years 4 months ago #64274 by voyager
Replied by voyager on topic Re: Dark Energy?

Well, the question is: does gravity work, or does earth suck... 8-)

The reason I really asked the original question was that I am not convinced we need to create dark energy to explain the behaviour of the observed universe. Gravity works just fine for me. I think that something in the nature of mass and the early universe might explain why and when the universe seemed to expand faster. who knows, maybe the early universe had a density that would not allow faster expansion

Nurse....my medicine please..... :x


People have tried to go that route and no one can get such theories to line up with observation and experiment. Maybe some day someone will but right now the evidence seems to point at empty space having energy. Ironically, we seem to be back at Einstein's much maligned universal constant!

Bart.

My Home Page - www.bartbusschots.ie

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16 years 4 months ago #64275 by voyager
Replied by voyager on topic Re: Dark Energy?
Oh I meant to add... if you're looking for good explanations of all these things then I can highly recommend the Asrtonomy Cast Podcast. Their back-episodes are a real treasure-trove of good explanations. The tag line for the show is "looking at not just what we know but how we know what we know" and I'm happy to say the hosts do a good job of living up to that. The main host is the guy who runs Universe Today. You can find the podcasts here: www.astronomycast.com/

Bart.

My Home Page - www.bartbusschots.ie

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