10+ universe facts worth knowing

There is no more exciting nor more significant development in science than modern cosmology. What greater question could we ask than how we came to exist? Whence the Universe? How and why are there galaxies and atoms; carrots and quanta; what does it all mean, if there is such a thing as meaning? Here are some milestones in the development of today’s understanding of the universe.

We learn what we learn about the universe from light and almost all of our natural light comes from a nearby star we call the Sun, either directly or by reflection off the Moon. With our eyes we can see a few thousand stars and five other planets that orbit the sun like the Earth. But, we didn’t look very closely until about 1600.

In a little over 100 years, the genius of Copernicus, Kepler, Galileo and Newton removed most of the mythology from astronomy.  The sun became just another star, stars became just other suns, and gravity ruled the behavior of rocks and Moons with one unifying, universal law.

By Newton’s time the idea that the universe was infinite and contained an infinite number of stars was accepted.  But this led to problems in physics, how does one deal with an infinite amount of radiation or infinite mass?

Galaxies and Cepheids

Galileo discovered that the Milky Way is a collection of stars (galaxy) spread out as a disk over a very large space.  (The Milky Way is about 100,000 light years across and contains 200 – 400 billion stars.)

In the 18^th century the astronomer William Herschel and the philosopher Immanuel Kant had identified other patches of light seen by Galileo as galaxies, but it was not until 1920 that the American astronomer Edwin Hubble (1889 – 1955) was able to resolve other galaxies into stars using the 100-inch telescope at Mt. Wilson in California.

Measuring the distances to stars was very difficult because it had to be done by stellar parallax. 1 second of 1 minute of 1 degree (1 parsec) measures a distance of 3.26 light-years. And, there are only 11 stars, not counting the sun, within 10 light-years of Earth.

General Relativity and Black Holes

In 1915, Albert Einstein presented his General Theory of Relativity. In General Relativity (GR), gravity is explained by the warping of space by matter. This effect is only measureable in very high gravity situations, such as near stars, but explained a well-known difference in the orbit of Mercury from that calculated with Newton’s gravitational law. The theory was further verified by the measurement of light being bent by the gravity of the sun during an eclipse in 1919.

In 1916, Karl Schwarzschild using Einstein’s general relativity, proposed that if a star had sufficient mass, it could collapse into a black hole where even radiation could not escape.  (In 1970, Stephen Hawking developed a quantum mechanical mechanism whereby black holes could eventually loose matter and decay below the critical mass.  And, in 1971, C. T. Bolt detected a black hole in Cygnus X-1.)

In 1923, Hubble resolved the Andromeda Galaxy into stars and calculated its distance at 1 million light years.  (We now know there are billions of galaxies.)

The Redshift and the Big Bang

In 1931, Georges Lemaitre (1894 – 1966), a Belgian Catholic Priest and Professor of Physics and Astronomy, following on the idea of an expanding universe, published a paper proposing that there had been a single primeval atom that had exploded to form the galaxies. But, will the universe always expand?  If so, there must be an infinite place into which to expand.

In 1932, Jan Oort, in Holland, calculated the mass that would be required for gravity to make the universe eventually stop expanding and then collapse. He found that there had to be additional mass at least equal to the observable mass.  He proposed that there must be a great deal of dark matter, mass we cannot see. Today, we estimate the dark matter to make up about 90% of the mass of the universe.

Steven Weinberg (1933 – ), an American Nobel Laureate in Physics, models the Big Bang in his excellent book: The First Three Minutes (1977). The following is condensed from Weinberg’s Chapter V:

1. Starting at zero time and infinite temperature, after about .01 seconds the temperature is 10 K.  There are only a small number of nuclear particles compared to photons and electrons and neutrinos.

2. After 0.11 seconds the temperature is 3 x 10¹⁰ K and neutrons can turn into protons.

3. After 1.09 seconds the temperature is 10¹⁰ K and we have a majority of protons among the nuclear particles.  It is still too hot for nuclei to form.

4. After 13.82 seconds the temperature is 3 x 10⁹ K and electrons and positrons are starting to disappear.  Nuclei can form.  Hydrogen and helium isotopes are forming.

5. After 3 minutes and 46 seconds, the temperature is 10⁹ K deuterium nuclei are forming but still breaking apart.  But soon the temperature reaches the point that deuterium holds together and larger nuclei form.

6. After 34 minutes and 40 seconds the temperature is 3 x 10⁸ K, electron-positron annihilation has ended and there is a slight excess of electrons to balance the charge of the protons.  Cooling continues for 700,000 years and then atoms start to form.  At this point, matter condenses and stars and galaxies can be created.

7. After 10 billion years we start to try to figure it out.

As of this writing, science has not definitively proven which kind of universe we have: a Big Bang universe or a static, eternal universe.

These are only a few steps which lead to today’s understanding of the universe. If you are interested in filling the gaps, then “The Evolution of Modern Science” written by Thomas L. Isenhour is the right book for you. You can download it for free.