Compare the Big Bang Theory to the Steady State Theory.
The steady state theory of cosmology claims that the Universe simply exists without changing with time. This theory presents many physical as well as philosophical difficulties. Evidence suggests that the Universe is expanding. While there are ways to explain expansion in a steady state universe, few astrophysicists believe this theory, because there is little evidence to support it. As the first widely held theory about the Universe it is included here for historical completeness.
The big bang theory states that at some time in the distant past there was nothing. A process known as vacuum fluctuation created what astrophysicists call a singularity. From that singularity, which was about the size of a dime, our Universe was born.
The Big Bang Theory is naturalistic science’s preferred explanation for the origins of the universe. Even so, there are questions about the theory that persist. One attempt to fill the holes left in the Big Bang Theory is a concept first developed in the late 1940’s, known as Steady State Theory.
Steady State Theory proposes that matter is being continuously created, at the rate of a few hundred atoms per year. This would allow the density of the universe to remain constant as it expands. This violates the First Law of Thermodynamics, but then again, so does the Big Bang Theory.
Scientific discoveries have shed doubt on Steady State Theory, such as cosmic background radiation. This radiation was predicted by Steady State Theory, just as it was by the Big Bang Theory. Still, cosmic background radiation fits better into the Big Bang Theory. In the 1990’s, the discovery of accelerating galaxies renewed interest in the general concept of Steady State Theory. The accelerating universe discoveries have added a lot of uncertainty to the discussion of the Big Bang Theory.
Why is Pluto not a Planet?
Astronomers estimate that there are at least 70,000 icy objects, with the same composition as Pluto, that measure 100 km across or more in the Kuiper Belt. And according to the new rules, Pluto is not a planet. It’s just another Kuiper Belt object.
Is Pluto a planet? Does it qualify? For an object to be a planet, it needs to meet these three requirements defined by the IAU:
- It needs to be in orbit around the Sun – Yes, so maybe Pluto is a planet.
- It needs to have enough gravity to pull itself into a spherical shape – Pluto…check
- It needs to have “cleared the neighborhood” of its orbit – Uh oh. Here’s the rule breaker. According to this, Pluto is not a planet.
What does “cleared its neighborhood” mean? As planets form, they become the dominant gravitational body in their orbit in the Solar System. As they interact with other, smaller objects, they either consume them, or sling them away with their gravity. Pluto is only 0.07 times the mass of the other objects in its orbit. The Earth, in comparison, has 1.7 million times the mass of the other objects in its orbit.
Any object that doesn’t meet these 3rd criteria is considered a dwarf planet. And so, Pluto is a dwarf planet. There are still many objects with similar size and mass to Pluto jostling around in its orbit. And until Pluto crashes into many of them and gains mass, it will remain a dwarf planet. Eris suffers from the same problem.
It’s not impossible to imagine a future, though, where astronomers discover a large enough object in the distant Solar System that could qualify for planet hood status. Then our Solar System would have 9 planets again.
Even though Pluto is a dwarf planet, and no longer officially a planet, it’ll still be a fascinating target for study. And that’s why NASA has sent their New Horizons spacecraft off to visit it. New Horizons will reach Pluto in July 2015, and capture the first close-up images of the (dwarf) planet’s surface.
How would you explain the existence of life on the planet? And why are they so diverse?
The most basic requirement of life on Earth is the presence of liquid water. Water is important to life because, in liquid form, it is an excellent medium for carrying chemical and biological compounds. It is also stable as a liquid over a wide temperature range, a temperature range that (conveniently) accommodates a wide range of biological processes. In identifying places where life may exist, astrobiologists are looking for signs of water, particularly in liquid form.
Astrobiologists are also looking for the right cosmic chemistry in their search for life. The presence of organic (carbon) compounds, while not conclusive, could be suggestive of life. Atmospheric concentrations of certain substances could also be indicative of living organisms. Oxygen and methane, for example, are both found in our atmosphere, but are both highly reactive molecules. Their individual presence suggests that molecules are being constantly produced to replenish the numbers in the atmosphere, and the source of this replenishment could be life.
Given that life did emerge and evolve on Earth, it seems a logical step to look for Earth-like planets as potential hosts for extraterrestrial life. These planets would be of a similar age and size to Earth, and orbit a similar distance from sun-like stars – far enough away from the star that any water present doesn’t evaporate, but close enough that it doesn’t freeze.
If there are highly evolved life forms out there we may even intercept signals from them. This search is the whole premise of the SETI program – the Search for Extraterrestrial Intelligence. Rather than looking for chemical and biological artifacts, SETI scientists are aiming to make contact with ETI through radio astronomy.
Of course, finding all of these things does not mean that we should not expect to find life forms (particularly evolved or higher life forms) that are in any way similar to life as we know it. The Earth’s biota is the result of a set of unique conditions shaping the products of the natural life giving processes – the laws of chance dictate that finding a planet whose population has survived five great extinction events, not to mention geological, meteorological , physical, chemical and biological conditions that ensued as a result of each other, is exceedingly slim, and even if we did, the probability of life beyond Earth following exactly the same evolutionary pathway is too remote to contemplate.