Let's talk about strange things and how they happen!

Formation of Stellar Mass Black Holes

Stellar mass black holes may be produced by the collapse of the cores of massive stars during supernova outbursts.

• initially, a smallish remnant forms--a remnant of mass on the order of 1.4 M(Sun)--a neutron star
• a shock wave next propagates through the outer layers of the star iginiting nuclear reactions and pushing on the envelope of the star
• depending upon the detailed structure of the envelope of the star, the shock will eject the envelope or it will stall and allow some or all of the envelope to fall-back onto the initial neutron star remnant
• if the material falls-back onto the star, then the mass of the remnant increases
  • neutron stars are like white dwarfs in the sense that as their mass increases, they get smaller (denser) in order to generate the higher pressure needed to counteract the effects of gravity
  • this has the same consequence in that there is an upper limit for the mass of a neutron star
  • the upper limit is not as well-determined as for the white dwarfs as the upper limit depends upon the nature of the nuclear (strong) interaction which is not well-understood under the conditions found in neutron stars -- the upper limit is 2 - 3 M(Sun)
• if the mass of the neutron star increases beyond 2 - 3 M(Sun), then the neutron star collapses and forms a black hole -- after the neutron star phase there is no known type of matter which can generate sufficient pressure to overcome the effects of gravity and the star must then contiuously collapse until it compresses to infinite density and zero volume!

Worm Holes - Hmmm They are surely strange enough!

If an isolated observer sees an object fall to the floor of his or her laboratory, the observer has a dilemma. The observer does not know if the laboratory is stationary, e.g., on the surface of something like the Earth, or if the laboratory is accelerating upward, e.g., it is being carried along in a rocket. Einstein stated this in the Principle of Equivalence.

The fact that the effects of gravity cannot be distinguished from those found in experiments performed in an accelerating rocket in space (far away from any massive object) suggests that gravity isn't a real force.

Einstein sought a geometric interpretation for gravity. He noted that objects on flat surface which are not subjected to forces roll in straight lines and that objects that roll on curved surfaces follow curved paths even when they are not subjected to external forces. The natural motion of an unforced object could either be a straight line (as Newton envisioned) or a curved line (as would be incomprehensible to Newton) depending upon the shape of the surface upon which it was rolling.

Einstein suggested that mass distorts the shape of space-time so that falling objects are simply rolling into the depression and orbiting bodies are simply rolling around in the depression. The objects are not undergoing forced motion; they are simply following the lay of the land.

Black holes distort space-time in a much more extreme manner (note the cusp or point the depression comes to at its bottom). An interesting discovery was made by Einstein-Rosen in the 1930's, they found that the black holes would close down but then actually re-open into another Universe forming an Einstein-Rosen bridge. Or an alternative interpretation is that the black hole would open up into another part of the space-time of our Universe. Such a passageway (wormhole) could lead to the possibility of time travel!!

There are many complaints which can be leveled at this suggestion; both physical and philosphical. Some of the physical complaints can be eased by looking at rotating black holes where you don't have to pass through the singularity, but the problems are still severe in that event horizons are one-way membranes.

There are other types of wormholes which do not suffer from some of the physical problems. These are known as Schwarzschild wormholes where you have singularities which are not cloaked by event horizons. These do not suffer from the problem of the one-way nature of event horizons but they do suffer from related problems.

As stuff passes through the throat of the wormhole, it compresses and so its density, mass/volume, goes up ===> GM/r**2 goes up and the throat pinches itself off. To get around this, Thorne, Morris, and Yurtsever postulated that some arbitrarily advanced civilization (AAC) could develop some new form of matter to hold open the throat of the wormhole. In this case, one could travel from place to place in spacetime and, under the right circumstances, could travel in time. That is one could use wormholes as time machines!!

The impossibility of time travel has not yet been demonstrated. However, there is no evidence that it has occurred and so, it is not likely to be possible. If we can understand why it is not possible then we will have done something which is quite significant. There is nothing in our current theories which tells us how time flows. There is no reason to believe, based on theory, why cause must precede effect. Since it always seems to do so probably means that there is some physical reason that escapes us (at the moment). If we could understand why time travel is not possible would help us to understand one of the more vexing problems facing us today (known as the arrow of time).

Now for something very interesting but less enticing- Lets Review Our Solar System

Our solar system consists of an average star we call the Sun, the planets (in order of their distance from the Sun) Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto. It includes: the satellites of the planets; numerous comets, asteroids, and meteoroids; and the interplanetary medium.

The planets, most of the satellites of the planets and the asteroids revolve around the Sun in the same direction, in nearly circular orbits. When looking down from above the Sun's north pole, the planets orbit in a counter-clockwise direction. The planets orbit the Sun in or near the same plane, called the ecliptic. Pluto is a special case in that its orbit is the most highly inclined (18 degrees) and the most highly elliptical of all the planets.

Solar System Live

The Sun contains 99.85% of all the matter in the Solar System. The planets, which condensed out of the same disk of material that formed the Sun, contain only 0.135% of the mass of the solar system. Jupiter contains more than twice the matter of all the other planets combined.

The four primary terrestrial worlds are the innermost planets in the solar system, Mercury, Venus, Earth and Mars. There are an additional 8 other terrestrial worlds; the Moon, Io, Europa, Ganymede, Callisto (the four Galilean moons), Titan (a moon of Saturn), Triton (a moon of Neptune) and Pluto. They are called terrestrial because they have a compact, rocky surface like the Earth's and are spherical in shape. The other moons are not spherical and are more asteroid-like (i.e. irregular). Venus, Earth, Mars and Titan have significant atmospheres while Mercury has almost none.
Jovian Planets >

Jupiter, Saturn, Uranus, and Neptune are known as the Jovian (Jupiter-like) planets, because they are all gigantic compared with Earth, and they have a gaseous nature like Jupiter's. The Jovian planets are also referred to as the gas giants, although some or all of them might have small solid cores.

Any formation theory must explain the difference between Terrestrial worlds and Jovian worlds:

T=is rocky and small <-> J=gaseous and large

Common Elements in the Solar System:

The most common elements on each planet tell us something about its formation process and later evolution. For example, small planets have gravitational fields that are too weak to maintain light elements such as H and He. Jovian worlds are cold and have many compounds as ice rather than gas or liquids.

Jupiter:

The largest of the planets in our Solar System, the name Jupiter was an accident since the ancient astronomers did not know Jupiter's real size. Its radius is 11.3 Earth radii, its mass is 317 Earth masses. Jupiter's mean density is 1.3 gm/cc, close to that of water.

The mean density of the Jovian worlds is near the value for water, 1 gm/cc versus the terrestrial worlds which have average densities near the value of rocks, 3 to 5 gm/cc. This was due to the fact that temperatures in the outer Solar System are low due to the large distance from the warm Sun. So volatile compounds, such as ices like H₂O (water), CO₂ (carbon dioxide), NH₃ (ammonia) and CH₄ (methane) tended to evaporate in the inner Solar System (although not all of them since there was plenty leftover to form secondary atmospheres). However, in the outer Solar System, these volatiles are very abundant and make-up most of the comets, moons and rings around the Jovian worlds.

Note that H₂O, CO₂, NH₃ and CH₄ are the simplest molecules you can make with hydrogen (H), carbon (C), oxygen (O) and nitrogen (N) = often called the HCNO compounds. Jupiter is also rich in NH₄SH = ammonium hydrosulfide.

The basic premise in the understanding our origins, and the properties of all the planets we have studied this term, is that natural forces created and shaped the Solar System. And that there is a continuity to that process, i.e. it is not a sequence of random events.

The overall architecture of our Solar System is orderly and the ages of its members uniform. All indicators point to a single formation event about 4.6 billion years ago.

The formation of Jupiter (and the other Jovian worlds) starts with the accretion (build-up) of ice-covered dust in the outer, cold solar nebula

Note that as the planet's began to form they grew in mass by accreting planetesimals. Since force of gravity is proportional to mass, the largest planetesimals are accreted first. The early proto-planets are able to sweep the early Solar System clean of large bodies. The jovian worlds, having an early edge on gathering mass in the colder outer solar disk, were the most efficient at capturing planetesimals, which only served to increase their already large masses. As the planetesimals shrink in average size, collisions with proto-planets lead to fragmentation. So quickly the Solar System divided into large proto-planets and smaller and smaller planetesimals which eventually began the numerous meteors we see today. Any leftover large bodies were captured as moons or ejected by gravity assist into the Oort cloud. The start of thermonuclear fusion in the Sun's core created enough luminosity so that the remaining hydrogen and helium gas in the solar disk was removed by radiation pressure.

The exterior of Jupiter is noted by its brightly colored latitudinal zones, dark belts and thin bands dotted with numerous storms and eddies. Due to differential rotation, the equatorial zones and belts rotate faster than the higher latitudes and poles.

The zones and belts are zonal jet streams moving with velocities up to 400 miles/hr. Wind direction alternates between adjacent zones and belts. The light colored zones are regions of upward moving convective currents. The darker belts are made of downward sinking material. The two are therefore always found next to each other. The boundaries of the zones and belts (called bands) display complex turbulence and vortex phenomenon.

Note: Upward moving gases in Jupiter's atmosphere bring white clouds of ammonia/water ice from lower layers. Downward moving gases sink and allow us to view the top, darker layers.

The most obvious feature on Jupiter is the Great Red Spot which is actually the top of a large cyclone twice the size of the Earth.

Gas planets do not have solid surfaces, but rather build-up in pressure and density as one goes deeper towards the core. Different colors represent different depths into Jupiter's atmosphere. The colors (reds, browns, yellows, oranges) are due to subtle chemical reactions involving sulfur. Whites and blues are due to CO₂ and H₂O ices.

The details of Jupiter's atmosphere is dominated by physics known as fluid dynamics. Note that the atmosphere of Jupiter so dense and cold that it behaves as a fluid rather than a gas. At the point were we see features the atmosphere pressure is 5 to 10 times that of the Earth's atmospheric pressure. The simplest theories in fluid dynamics predict two types of patterns. One pattern occurs when a fluid slips by a second fluid of a different density. Such an event is known as a viscous flow and produces wave-like features at the boundary of the two fluids. A second pattern is produced by a stream of fluid in a constant medium. The stream breaks up into individual elements. These smaller sections can develop into cyclones.

Cyclones develop due to the Coriolis effect where the lower latitudes travel faster than the higher latitudes producing a net spin on a pressure zone. The cyclones on Jupiter are regions of local high or low pressure spun in such a fashion. Note that the direction of the spin differs in the two hemispheres where counter-clockwise spin is in the North and clockwise spin is in the South.

Brown ovals are low pressure cyclones/storms in the North. White ovals are high pressure cyclones/storms in the South. Both can last on the order of tens of years. The Great Red Spot is a large high pressure storm that has lasted over 600 years.

The energy needed to power all the turbulence in Jupiter's atmosphere comes from heat released from the planet's core.

Return to Fun Physics

Web Page by......email me!

This section is still under construction.