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Author Topic:   Where does the gravity go?
Sylas
Member (Idle past 5551 days)
Posts: 766
From: Newcastle, Australia
Joined: 11-17-2002


Message 43 of 49 (206868)
05-10-2005 9:07 PM
Reply to: Message 39 by coffee_addict
05-09-2005 9:51 PM


Re: back to energy and gravity
"Troy" writes:
Current estimates reveal that about 25-30% of the universe is made of the visible matter, about 30-35% is made of dark matter, and about 60-65%ish is made of dark energy.
Actually, current estimates for the energy budget are 4% baryonic matter, 23% non-baryonic matter, 73% dark energy, and negligible fractions radiation.
You have to be careful reading the percentages, since you can give percentages in relations to different things. The fractions above are proportions of the energy budget for a flat universe. You will also see quoted fractions of the total matter making up the universe.
Baryonic matter means matter like we know and love.
Of the Baryonic matter, some is luminous, and some is dark. It seems to be roughly about 10% of baryonic matter is actually visible.
The term "dark matter" can refer to both non-luminous ordinary matter, and exotic non-baryonic matter.
Cheers -- Sylas

This message is a reply to:
 Message 39 by coffee_addict, posted 05-09-2005 9:51 PM coffee_addict has replied

Replies to this message:
 Message 44 by coffee_addict, posted 05-10-2005 10:24 PM Sylas has replied
 Message 45 by nipok, posted 05-10-2005 10:41 PM Sylas has not replied

  
Sylas
Member (Idle past 5551 days)
Posts: 766
From: Newcastle, Australia
Joined: 11-17-2002


Message 46 of 49 (206934)
05-11-2005 4:47 AM
Reply to: Message 44 by coffee_addict
05-10-2005 10:24 PM


Re: back to energy and gravity
MAssively Compact Halo Objects (MACHOs) are normal baryonic matter. This means big lumps of matter that isn't shining. Brown dwarves, black holes, neutron stars, planets escaped from a solar system, etc. We know they exist, but the numbers in which we know they exist are not sufficient to balance the books.
The major alternative is Weakly Interacting Massive Particles (WIMPs). This is the non-baryonic alternative. There's good reason to think they exist, both on the basis of particle physics and cosmological observations. The notion is that (like neutrinos) there are many of these passing through us all the time. Problem is that we can't detect them because the interactions with matter are so weak. There are experiments trying to get very sensitive detectors able to notice a passing WIMP; but so far... nothing.
Cheers -- Sylas

This message is a reply to:
 Message 44 by coffee_addict, posted 05-10-2005 10:24 PM coffee_addict has not replied

  
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