Section 4 – Space Exploration
Current understanding of the universe
What we know about the Universe is a result of humankind’s continual curiosity about our existence. This has led to a remarkable understanding of our Universe which is continually developing. Much of this can be attributed to our continual observation of space along with our exploration of the Solar System and beyond.
Big Bang Theory (http://big-bang-theory.com)
- The Big Bang theory is an effort to explain what happened at the very beginning of our universe.
- Discoveries in astronomy and physics have shown beyond a reasonable doubt that our universe did in fact have a beginning. Prior to that moment there was nothing; during and after that moment there was something: our universe.
- Our universe sprang into existence as a “singularity” around 13.7 billion years ago.
- Singularities are zones which defy our current understanding of physics. They are thought to exist at the core of Black Holes.
- Black holes are areas of intense gravitational pressure. The pressure is thought to be so intense that finite matter is compressed into infinite density.
- Our universe is thought to have begun as an infinitesimally small, infinitely hot, infinitely dense singularity.
- After its initial appearance, the universe inflated, expanded and cooled, going from very, very small and very, very hot, to the size and temperature of our current universe.
- It continues to expand and cool to this day and we are inside of it!
- There is currently debate as to whether the universe will continue expanding, or whether it will start to contract.
Big Bang Theory – Evidence for the Theory
- Galaxies appear to be moving away from us at speeds proportional to their distance. This is called “Hubble’s Law,” named after Edwin Hubble (1889-1953) who discovered this phenomenon in 1929. This observation supports the expansion of the universe and suggests that the universe was once compacted.
- “Doppler red-shift” also provides evidence that galaxies are moving away from us. The light from galaxies appears to be more red than it should be, and the decreased frequency of the light tells us that the galaxies are moving away from us.
- If the universe was initially very, very hot as the Big Bang suggests, we should be able to find some remnant of this heat. In 1965, Arno Penzias and Robert Wilson discovered a 2.725 degree Kelvin (-270.425 degree Celsius) Cosmic Microwave Background radiation (CMB) which pervades the observable universe. This is thought to be the remnant which scientists were looking for. Penzias and Wilson shared in the 1978 Nobel Prize for Physics for their discovery.
- The abundance of the “light elements” Hydrogen and Helium found in the observable universe are thought to support the Big Bang model of origins.
Space exploration and our understanding of the Earth
Satellites have allowed us to make observations of the Earth.
Important observations of the environment have been made using monitoring satellites in orbit around the Earth, including:
- reduction of rainforest
- melting of polar icecaps
Technologies arising from space exploration
Some examples include
- Weather forecasting
- GPS and Sat Nav
- Global communication
- Satellite TV
- Protective paints
NASA has a website called “Spin-off” which shows how technologies developed in their Space Programme have benefits in everyday life –
http://spinoff.nasa.gov/index.html
http://spinoff.nasa.gov/Spinoff2008/tech_benefits.html
http://www.nasa.gov/externalflash/nasacity/index2.htm
For any technology that you provide, you must be able to describe the impact that it has on our everyday life.
Re-entry into the atmosphere
- When a spacecraft re-enters the Earth’s atmosphere, it is travelling at a velocity of around
11 000 m/s. - The force of air resistance from the Earth’s atmosphere is huge at these velocities.
- Air resistance does work on the spacecraft which changes the kinetic energy to heat (Ek→Eh).
- The heat absorbed can cause a temperature increase of around 1300 °C
Heat Shield Design
Case Study – the Shuttle
The Shuttle was the first (and only) reusable spacecraft. The first Shuttle mission was launched in 1981 and the final mission was in July 2011.
The part of the Shuttle that returns to Earth is called the Orbiter and its shape resembles an aircraft.
(For more information, see http://www.nasa.gov/mission_pages/shuttle/main/index.html).
- The Shuttle Orbiter is made from aluminium alloy covered in special tiles to protect it from the intense heat generated during re-entry.
- The Shuttle needs around 34 000 thermal protection tiles (all of different shapes and sizes).
- The tiles are made of a material called silica, which has a high specific heat capacity and a high melting point (c=1040 J/kg°C, melting point = 1610 °C).
- The tiles are painted black so that heat is lost to the surroundings. The air around the shuttle heats up. The temperature increase of the shuttle is therefore not as great.
