Anti-Matter vs. Dark Matter

The Collison Annihlation of Matter and Anti-matter

The Collison Annihlation of Matter and Anti-matter

What is the difference between anti-matter and dark matter? Is there anything anti-matter and dark matter have in common?

Anti-matter is the idea of negative matter, or matter with the same mass but opposite an charge and quantum spin than that of normal matter. Anti-matter is just like normal matter with different properties. The antimatter of the electron (e-)  is the positron (e+); similarly, the antimatter of the proton is the anti-proton (p-). When normal matter and anti-matter collide, the two annihilate each other. Scientists speculate that anti-matter and matter existed in equal quantities in the early Universe.  The apparent asymmetry of high quantities of matter and very low quantities of anti-matter is a great unsolved problem in physics. Anti-matter is only found through radioactive decay, lightning, and cosmic rays (high-energy particles from supernovae) and very expensive to produce. Practical uses of anti-matter include the positron emission tomography (PET) used for medical imaging and as triggers to nuclear weapons.

Dark matter cannot be seen and is hard to detect, because dark matter interacts by gravity and weak atomic force, not with strong atomic forces (nuclear force: holds subatomic particles, electrons, neutrons, and protons, together in an atom) or electromagnetism. Dark matter constitutes about 22.7% of the Universe. On April 3, 2013, the International Space Station’s Alpha Magnetic Spectrometer (AMS) found the first evidence of dark matter. [AMS was carried out by the Endeavor in 2011 in one of NASA’s last space shuttle flights.] Normally, detectors are blocked by Earth’s atmosphere, but by orbiting Earth above its atmosphere,  the AMS can monitor cosmos rays (have an excess of anti-matter, discovered two decades ago) without hindrance. The AMS will tell scientists whether the abundance of positrons signal the presence of dark matter.  One theory scientists are testing is supersymmetry, which speculates that the collision and annihilation of two dark matter particles could produce positrons. Another instrument that could help the dark matter hunt is the Large Underground Xenon Experiment (LUX).

References

Anderson, Natali. “Antimatter Hunter aboard International Space Station Detects Hints of Dark Matter.” Sci-News.com. Sci-News.com, 4 Apr 2013. Web. 4 Apr 2013.

Boyle, Alan. “Space station’s antimatter detector finds its first evidence of dark matter.” NBCnews.com. NBC News, 3 Apr 2013. Web. 4 Apr 2013.

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Fun Facts Cluster 2: From Space Rocks to Drones (AskAstro)

1. SPACE ROCK SUICIDE: Scientists can detect a comet or asteroid colliding into the Sun’s surface. The self-destructing comet or asteroid will explode due to pressure of traveling into the Sun’s photosphere. The brightness and impact of the collision depends on the mass of the object. A collision as such is high unlikely, however, because: 1) most comets and asteroids would to dust and vapor in the sizzling atmosphere of the Sun 2) objects will lose most of its mass as they approach the Sun 3) objects normally orbit the Sun, so the objects’ orbit must be altered or the object may be from another planetary system.

2. STELLAR DONATIONS: In a binary star system, if stars are close enough, tides can become so strong that the more gravitationally strong star call pull gas from the surface of its companion. Though the “tidal transfer” depends on the mass of the donor star, if two stars have equal mass, the accretor (the star gaining mass) will steal mass if the donor star’s radius exceeds 38 percent of the binary separation (distance between the stars) no matter the separation.

3. COLOR CODE: The dark and light horizontal bands depend on the organization of winds in Jupiter’s atmosphere. The light bands have a eastward jet on the side closest to the pole, and vice versa in the dark bands. The zones (light bands) appear bright because of colorless high-altitude clouds that contain ammonia ice. The belts (dark bands) have much thinner high altitude clouds and darker particles.

4. DANGEROUS FLYBY: NASA calculates the planetary flybys with nothing but Newton’s laws of motion. The desired closest approach depends on the mission and how much added velocity boost the mission requires.  The mass and closeness of the planet determines the bending of trajectory the probe must undergo. The approach distance can range from a few hundred to several thousand kilometers.

From: Astronomy magazine December 2012 Vol 41 Issue 12

Temperature of the Universe

What is the universe’s temperature? How has it changed and evolved? What causes the temperature to change? How is the temperature estimated? Is it continuously cooling or constant? –Pcelsus

Black Body Curve of the Cosmic Microwave Background

13.75 billion years ago, the Universe was much smaller and hotter. In the 1960s, Robert Dicke predicted a remnant “glow” from the Big Bang. In 1965 at the Bell Labs, radio astronomers Amo Penzias and Robert Wilson discovered that glow, named the cosmic microwave background radiation. The CBR was seen in all directions in empty space, with a black body curve (temperature ~3K in every direction). About 1 second after the Big Bang, the Universe was very hot, at ~1 billion K. At 3 minutes, protons and neutrons combine to form the nuclei of atoms. As space cooled, material condensed and atomic particles, then elements, molecules, stars, and galaxies formed. The hydrogen/ helium ratio (3:1) found today is about the same as what’s expected after the Big Bang. Atoms were “ionized” with electrons roaming free without being bound. At 300,000 years after the Big Bang, the Universe becomes transparent with a temperature of 3,000K. Light red-shifted by a factor of 1000, and the expansion of the Universe ensued.

Today, the Universe is 2.73K, or 2.73°C above absolute zero, but at the beginning of space and time, the Big Bang, the Universe reached over one billion degrees. From a single pinpoint, the Universe emerged as a scorching hot primordial soup of subatomic particles moving at high velocities. As the Universe expanded, the temperature cooled as more space was created and density decreased. The Universe is continuously cooling as it expands.

Measuring the temperature isn’t as simple as sticking a thermometer in space and waiting until it stabilizes at a certain temperature. Instead, scientists measure indirectly using the cosmic microwave background, or leftover radiation emitted by hot plasma 38,000 years after the Big Bang. As the Universe expanded, the electromagnetic waves of the CMR elongated and decreased in energy, leading to cooler temperatures. Using Planck’s law, scientists measured the black body radiation of the Universe. Planck’s law states that every object radiates electromagnetic energy according to temperature. Black body curves are lopsided, with the curve peaking at different wavelengths depending on the object. In fact, space has a nearly perfect black body curve, since physical objects tend to absorb and reflect light in certain wavelengths.

Age of Earth and Age of the Universe

How do scientists determine the ages of the Earth and the Universe? –Peyami

Earth

Age of Earth

Planet Earth is approximately 4.54 billion years old. But how did scientists determine this? With the radiometric dating of meteorites and the ages of the oldest known minerals. While the oldest meteorites found on Earth are approximately 4.5 billion years old, the oldest known mineral, zircon, discovered by Jack Hills in Australia is at least 4.4 billion years old. One meteorite used was the Canyon Diablo meteorite (4.55 billion years old) aged by C. C. Patterson. Since most of Earth’s minerals have undergone change in the core, mantle, and crust by plate tectonics, weathering, and hydrothermal circulation (circulation of hot water), scientists usually cannot use them in dating Earth. However, scientists used ancient Archaean lead ores of galena (natural mineral form of lead II sulfide), the earliest formed homogenous lead isotope, which very precisely dated Earth at 4.54 billion years. Furthermore, inclusions rich in calcium and aluminum in meteorites were formed within the solar system about 4.567 billion years age. As the oldest known solid component of meteorites, these Ca-Al inclusions determine the age of the solar system and set the upper limit of the age of Earth. Scientists do not known the time of Earth’s accretion (growth by gravitationally attracting more matter), but believe it started some after the Ca-Al inclusions formed.

In fact, scientists have long debated over and calculated the age of Earth. People had estimated Earth at just hundred of thousands of years! Later, scientists extended their estimates with more evidence. However, it wasn’t until Charles Darwin, who proposed the theory of natural evolution, that scientists began to make closer estimates. Using the molecular clock and the rate of genetic divergence, scientists estimate the last universal ancestor of all organisms at 3.5-3.8 billion years old.

Expansion of the Universe

Age of the Universe

The age of the Universe is 13.75 billion years old. People long thought the Universe as much younger— millions, let alone billion of years old. Edwin Hubble’s observations in the 1920s showed that the Universe has a finite age. Using Doppler Shift, Hubble discovered that the Universe was expanding. Every galaxy seemed to be moving away from each other, showing red shifts in their spectral lines. In 1958, Allan Sandage made the first calculation of a value called the Hubble’s constant, which determines the rate of the Universe’s expansion. With the Hubble’s constant, Sandage made the first accurate (closer than before) estimate of the age of the Universe at ~20 billion years. Discovered in 1965, the microwave cosmic background radiation, a remnant of the Big Bang, confirmed the expanding Universe theory. As the Universe expanded, it gradually cooled. The CBR shows the Universe at 2.7 K. In fact, scientists have recently discovered dark energy. Dark energy accelerates the expansion of the Universe, reducing earlier estimates of >14 billion years to 13.75 billion years.

Graph of Expansion: Expansion is Accelerating!

Dark Matter

Dark Matter: Visualization

In 1932, Jan Oort predicted dark matter to account for differences between mass calculated from astronomical objects’ gravitational effects and mass calculated from “luminous” matter contained in these objects (gas, stars, dust). In 1933, Fritz Zwicky observed that galaxies are moving too fast. In the Coma cluster, the gas is moving very fast, held at high temperatures. There must be a lot of gravity unseen to account for the pressure.

From 1965-1985, Vera Rubin discovered: 1. Rotation Curves – stars at the center and the edges travel at the same speeds, the closer the stars, the faster stars should travel, but evidence refuted this; 2. Gravitational Lensing – light is bent from the source as it travels to the observer.

Dark matter is believed to be a new class of subatomic particles. It cannot be seen or detected directly. Since it does not emit or absorb light and other electromagnetic waves, dark matter can only be predicted from its effects on visible matter. Astronomers believe dark matter account for 84% of matter and 23% of mass-energy in the Universe. Like “halos within halos,” dark matter surrounds galaxies, explaining such phenomena observed.

The Big Bang Theory

The Big Bang Theory

About 14 billion years ago, the Universe was much smaller and hotter. In the 1960s, Robert Dicke predicted a remnant “glow” from the Big Bang. In 1965, radio astronomers Penzias and Wilson discovered that glow, named the cosmic microwave background radiation. The CBR was seen in all directions in empty space, with a black body curve (temperature ~3K). About 1 second after the Big Bang, the Universe was very hot, at ~1 billion K. At 3 minutes, protons and neutrons combine to form the nuclei of atoms. The hydrogen/ helium ratio (3:1) found today is about the same as what’s expected after the Big Bang. Atoms were “ionized” with electrons roaming free without being bound. At 300,000 years after the Big Bang, the Universe becomes transparent with a temperature of 3,000K. Light red-shifted by a factor of 1000.

Big Bang: Timeline

*Recent measurements show the Big Bang at 13.75 billion years ago. Scientists recently discovered dark energy; the Universe is not only expanding, but accelerating in expansion. So, earlier estimates of the age of the Universe at 15 billion years have been reduced to 13.75 billion years.

The Universe: Main Points

  1. Expansion of the Universe
  2. Cosmic Microwave Background
  3. Primordial Nucleosynthesis
  4. Evolution of Galaxies and Large Scale Structure Over 14 Billion Years

The Universe: Composition

  • 0.03% heavy elements
  • 0.3% neutrinos
  • 4% stars and gas
  • 25% dark matter
  • 70% dark energy