Origins : Dark Matter & Dark Energy

1. Origins:Dark Matter & Dark Energy WWK: Students will understand the theories of Dark Matter & Dark Energy and how they’re thought to affect the Universe.

2. Dark Matter • Dark Matter - matter that influences the evolution of the universe gravitationally, but emits no light. (Hence, “dark”) • There are two types of Dark Matter: Baryonic and Nonbaryonic. • Baryonic Dark Matter is considered Hot, while Nonbaryonic Dark Matter is considered Cold. BARYONS – SUBATOMIC PARTICLES CONSISTING OF 3 QUARKS, BELONGING TO THE HADRON FAMILY OF PARTICLES. THESE MAKE UP BARYONIC DARK MATTER.

3. Dark Matter cont’d. • As mentioned in the previous slide, Baryonic is hot because of its ability to form hot gas clouds. This is a result of the velocities baryonic particles are able to achieve. • Nonbaryonic are cold because they travel at relatively lower velocities and form colder gases.

4. Dark Matter cont’d. • However, there are theories that Dark Matter may not be Baryonic at all. The most widely accepted view is that Dark Matter may be composed of WIMPS rather than baryons, because gas clouds would be visible through an infrared lens. (We know that dark matter is invisible) Others still believe it is composed of baryons tied up in brown dwarfs or dense chunks of heavy elements, (MACHOS) but this theory is very disprovable using a “gravity lens”. • WIMPS – Weakly Interacting Massive Particles • -Axioms, Neutrinos, Neutralinos • MACHOS – MAssive Compact Halo Objects • -Black Holes, Neutron Stars, Brown Dwarfs

5. Dark Matter - WIMPS • WIMPS – Weakly Interacting Massive Particles • -Axioms, Neutrinos, Neutralinos • If they were created in the right amounts and and with the right properties soon after the Big Bang, they could very well be the Dark Matter of the Universe. • However, the neutrino does not have enough mass to be a major component of Dark Matter. Observations have not been able to detect axioms or neutralinos yet.

6. Dark Matter - MACHOS • MACHOS – MAssive Compact Halo Objects • -Black Holes, Neutron Stars, Brown Dwarfs • Neutron Stars are extremely massive, and if they are isolated, they can also be “dark”. • Because a Neutron Star is a result of a Supernova, they aren’t common. As a result of a Supernova, a release of a massive amount of energy and heavy elements should occur. However, there is no such evidence that they occur in sufficient numbers in the halo of galaxies.

7. Dark Matter Conclusion • There is simply not enough data in discovery to come to a based conclusion over the theories of Dark Matter in the Universe. The alleged 23-25% of Dark Matter that comprises the Universe could be WIMPS, but it’s been stated that they haven’t been detected. The MACHOS could comprise that percentage, but it’s also believed that they could help comprise the 4-5% of ordinary matter in the Universe. Nobody is for certain. ONTO DARK ENERGY…

8. Dark Energy • Dark Energy – the energy that causes the acceleration/deceleration of the expansion of the Universe. • The Universe is assumed to be composed of 74% Dark Energy, 22% Dark Matter, and 4% Ordinary Matter. • Astronomers know dark matter is there by its gravitational effect on the matter that we see, and there are ideas about the kinds of particles it must be made of. By contrast, dark energy remains a complete mystery. • The name "dark energy" refers to the fact that some kind of "stuff" must fill the empty space in the Universe in order to be able to make space accelerate in its expansion. In this sense, it is a "field" just like an electric field or a magnetic field, both of which are produced by electromagnetic energy. But this analogy can only be taken so far, because we can readily observe electromagnetic energy via the particle that carries it, the photon.

9. Dark Energy – Something from nothing • Energy is supposed to have a source — either matter or radiation. The notion here is that space, even when devoid of all matter and radiation, has a residual energy. That "energy of space," when considered on a cosmic scale, leads to a force that increases the expansion of the universe. • Perhaps dark energy results from weird behavior on scales smaller than atoms. The physics of the very small, called quantum mechanics, allows energy and matter to appear out of nothingness, although only for the tiniest instant. The constant brief appearance and disappearance of matter could be giving energy to otherwise empty space.

10. Dark Energy – What Could Happen • With the discovery of Dark Energy, scientists theorized that the fate of the Universe could lay in its hands. • The Universe could expand so vastly and rapidly that Gravity’s effect could be undone, causing galaxies, solar systems, and even atoms to be ripped apart. This is known as the “Big Rip”. • This eliminated the possibility of the “Big Chill”, which was a theory that the expansion of the Universe would come to a gradual halt.