Science and Society podcast: Interview with Dr Kim Griest 2

Part 2 of a podcast with Dr. Kim Griest discussing dark matter and dark energy with Dr. David Lemberg/Sam Kephart on Science & Society radio, April 19th 2006. Source- http://www.scienceandsociety.net/podcasts/archives/2006/04/dr_kim_griest_p.html Part 1 and description- http://www.youtube.com/watch?v=lfJA_BcOPc8 Blog relating to Dark Energy- http://blog.myspace.com/index.cfm?fuseaction=blog.view&friendID=120129993... Hubblesites Dark Energy website- http://hubblesite.org/hubble_discoveries/dark_energy/

Category:

Science & Technology

Tags:

• dark
• matter
• energy
• supernova
• universe
• galaxies
• griest
• science
• wimps
• machos

[hunterbender]

well, here's my question, if this dark energy is causing the expansion of space....and with more space, there is more energy..then isn't energy being created? Won't that contradict with the first law of thermodynamics?

[stevebd1]

It's the nature of the first law of thermodynamics that gives dark energy it's peculiar anti-gravity quality. Dark energy has negative pressure. In Einstein's law of gravity, the sign of the gravitational force is determined by the total energy density plus three times the pressure. If the pressure of the material is negative and big enough, it can cancel out the energy density, nullifying gravity.

[stevebd1]

If the pressure is negative and bigger still, then the 'sign' of the gravity actually reverses, and instead of gravity attracting, it repels. This negative gravitational energy exactly cancels out the positive energy represented by the matter introduced. The total energy of the universe remains zero.

[xorion134]

let me just give a hint first of all to began Mathematics is wrong for about 5000 thousand years ago many civilizations like egyptians, aztecs, mayas they were using another type of system that was precisely and accurate but was not mathematics.Is like the religions, people went wrong at the beginnig. Is the same as today dark matter and energy thats just wrong and I know another concept on this

[xorion134]

I have another perspective or idea of what really is "dark matter" or "dark energy" it seems that maybe theyre so close of what is really outer if you interesting you just hit me and we can disscuss this...

[JuanVoyce]

Dark energy is the new Plato's ether.

[forthreisch]

Ok, see what you mean. Allthough it's pretty hard to imagine stuff like this.

It's pretty much accepted that the universe is expanding. Not like a balloon, but also the spaceroom and time. It's so very confusing to me.

What is this nothing the universe is expanding into. I just can't grasp it. But that's kinda the beauty with it for me.

[fatihkhider]

i do not know where time fits in on these observations of expansion of the universe!it is affected by space,if space is warped time will dilate, now what will happen to it when no baryonic matter around to warp it ?

[forthreisch]

This so messes with my line of thought.. What could be outside the universe? another even bigger one? where does it end? does it end? See what I mean?

[mareleblond98]

that's so fucked up! say goodbay to space travel!

[oxydized]

chanfle!!!

[stevebd1]

This caused the expansion of the universe to increase due to the 'anti-gravity of dark energy. Eventually our universe will be about 95% dark energy, 4% dark matter and 1% baryonic (and so forth).

[stevebd1]

Based on observations of supernovae at various redshifts, this balance was slowly eradicated at about 7-8 billion years after the big bang when there was a 'shift' in the rate of the cosmic expansion. As the universe had been expanding, the vacuum had increased and therefore vacuum energy (the cosmological constant) had increased to the point that it began to out weight dark and baryonic matter (today being about 5% baryonic, 23% dark matter and 72% dark energy).

[stevebd1]

Shortly after the big bang when the volume of the universe was smaller, there was less vacuum (i.e. the cosmological constant was small) and more dark and baryonic matter (about 15% baryonic, 75% dark matter and 10% dark energy), therefore gravity slowed down cosmic expansion (dark matter interacts like regular matter with gravity whereas dark energy is repellant).

[superfisto]

so the cosmological constant is the slope on the side of that "funnel" in the picture?

[RobotsAreHereNow]

cool