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Overview

What life requires
The other planets in the solar system
How the size of a planet affects its gravity
The challenges of space travel
How long to get to Mars?
Size of the Universe
Making contact
Voyager 2
Conclusions

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Life (as we know it) needs

Appropriate elements – for bone and tissue, etc
Appropriate food
Appropriately sized planet

Smaller than earth is OK, but bigger can make it difficult to walk for a human—sized person. Feet get too heavy to lift….

Appropriate temperature

Planets closer to the sun are warmer than those further away

Appropriate atmosphere
Protection from radiation in space, and the sun

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Living Organisms

Living organisms contain relatively large amounts of oxygen, carbon, hydrogen, nitrogen, and sulphur (these five elements are known as the bulk elements)
Along with sodium, magnesium, potassium, calcium, chlorine, and phosphorus (these six elements are known as macrominerals).

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The Elements

Of the approximately 115 elements known, only the 19 highlighted in purple in Figure 1.26 are absolutely required in the human diet. These elements—called essential elements—are restricted to the first four rows of the periodic table (see Chapter 32 "Appendix H: Periodic Table of Elements"), with only two or three exceptions (molybdenum, iodine, and possibly tin in the fifth row)
Some other elements are essential for specific organisms. For example, boron is required for the growth of certain plants, bromine is widely distributed in marine organisms, and tungsten is necessary for some microorganisms
https://chem.libretexts.org/Textbook_Maps/General_Chemistry_Textbook_Maps/Map%3A_Chemistry_(Averill_and_Eldredge)/01%3A_Introduction_to_Chemistry/1.8_Essential_Elements_for_Life

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Figure 1.26 The Essential Elements in the Periodic Table. Elements that are known to be essential for human life are shown in purple; elements that are suggested to be essential are shown in green. Elements not known to be essential are shown in gray.

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Approximate Elemental Composition of a Typical 70 kg Human

Bulk Elements (kg)		Macrominerals (g)
oxygen	44	calcium	1700
carbon	12.6	phosphorus	680
hydrogen	6.6	potassium	250
nitrogen	1.8	chlorine	115
sulfur	0.1	sodium	70
		magnesium	42

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http://www.enchantedlearning.com/subjects/astronomy/planets/

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The Solar System – planet sizes to scale, but not distances�https://en.wikipedia.org/wiki/Solar_System �

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The Sun�https://en.wikipedia.org/wiki/Sun

99.9% of the mass of the solar system
73% Hydrogen
25% Helium
93 million miles from earth
Light takes 8 mins from the sun to the earth
Diameter is 860,000 miles (approx. 109 times the earth’s diameter)
One million earths would fit inside the sun
Moon is 240,000 miles from earth, Mars is 140 million miles away (average)

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Planets and Sun – Size Comparison�https://commons.wikimedia.org/wiki/File:Planets_and_sun_size_comparison.jpg

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The Solar System

Our solar system consists of the sun, eight planets, moons, many dwarf planets (or plutoids), an asteroid belt, comets, meteors, and others. The sun is the center of our solar system; the planets, their moons, a belt of asteroids, comets, and other rocks and gas orbit the sun.
The eight planets that orbit the sun are (in order from the sun): Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune. Another large body is Pluto, now classified as a dwarf planet or plutoid. A belt of asteroids (minor planets made of rock and metal) lies between Mars and Jupiter. These objects all orbit the sun in roughly circular orbits that lie in the same plane, the ecliptic (Pluto is an exception; it has an elliptical orbit tilted over 17° from the ecliptic).
Easy ways to remember the order of the planets (plus Pluto) are the mnemonics: "My Very Excellent Mother Just Sent Us Nine Pizzas"
http://www.enchantedlearning.com/subjects/astronomy/planets/

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The Earth Moves

Earth rotates around its own axis once every 24 hours – giving day and night (speed 1,000 mph)
Earth also rotates around the sun once every 365.2 days – giving the seasons (speed 67,000 mph)
Moon rotates around the earth every 27 days – gives the tides on earth due to its gravity ‘pull’ (speed 2,200 mph)
Moon rotates about its own axis to always have the same side facing earth (hence we do not see the so-called dark side of the moon, except via a satellite)

Reference: http://en.wikipedia.org/wiki/Earth%27s_orbit

http://en.wikipedia.org/wiki/Earth%27s_rotation

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Speed of light – Romer (1676)

Approx 8 mins from sun to earth
Approx 4 light years to nearest star (Centauri) – approx 1,000 years by fastest space probe
Approx 2 million light years to the nearest galaxy (Andromeda)

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Newton’s apple on the moon

Apple falls to earth about 16 ft in 1 sec
Acceleration due to gravity on the moon is approx 1/6 that on earth

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How to Escape from Earth

How heavy is the earth in tons? 6 x 10^21 tons
How big is the earth – diameter? 8,000 miles
How does this compare to the Moon?

Moon is 2,000 miles in diameter
Moon is 8 x 10^19 tons

How does this compare to the Sun?

Sun is 900,000 miles in diameter
Sun is 2 x 10^27 tons, and burns 10 million tons per sec

What is the Escape Velocity needed to escape from earth? 25,000 mph (1 million mph for Sun; 5,000 mph for Moon)

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Journey into Space? - 1

Difficulty of escaping earth’s gravity (escape velocity ~21,000 mph, about 62 miles high and an orbital speed of 5 miles/sec (18,000 mph))
Rocket technology is high risk
Difficulty of re-entry to the earth’s atmosphere due to friction/heat – 3,000 degrees F. Travelling at 17,500 mph. High G forces: 3-4G
3 days’ journey to the moon – 240,000 miles
Sun is 93 million miles from earth; Mars is 36 million to 250 million miles. Gives ~450 days to travel to Mars at the shortest distance

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Journey into Space? - 2

Living conditions?

Temperature on the Moon: -153 degrees C at night and +107 degrees C during the day. No atmosphere, water or oxygen. Need an insulated space suit to survive
Temperature on Mars – average -63 degrees C. Has ice-caps (i.e. water) and thin atmosphere of 95% carbon dioxide (plus some nitrogen and argon). Severe dust storms cover the planet
Other planets look even more inhospitable!

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How long to Mars?�http://www.space.com/24701-how-long-does-it-take-to-get-to-mars.html

Here is a list of how long it took several historical missions to reach the red planet. Their launch dates are included for perspective.

Mariner 4, the first spacecraft to go to Mars (1964 flyby): 228 days
Mariner 6 (1969 flyby): 155 days
Mariner 7 (1969 flyby): 128 days
Mariner 9, the first spacecraft to orbit Mars (1971): 168 days
Viking 1, the first U.S. craft to land on Mars (1975): 304 days
Viking 2 Orbiter/Lander (1975): 333 days
Mars Global Surveyor (1996): 308 days
Mars Pathfinder (1996): 212 days
Mars Odyssey (2001): 200 days
Mars Express Orbiter (2003): 201 days
Mars Reconnaissance Orbiter (2005): 210 days
Mars Science Laboratory (2011): 254 days

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Mars�https://en.wikipedia.org/wiki/Atmosphere_of_Mars

Mars may have had water in the past (canals), or may still have water underground
Atmosphere is mainly carbon dioxide
Currently does not appear likely that there is life, unless it is a very elementary form
Could there be earth-like planets as part of other solar systems in other galaxies?
Multiverses
https://en.wikipedia.org/wiki/Multiverse

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Size of the Universe

Very large
One light year is 5.8 million million miles
Estimated distance from earth to the edge of the observable universe is 46 billion light years
Distance from earth to moon is 240,000 miles
Distance from earth to sun is 93 million miles
Time to the nearest star (at the speed of light) is 4 years
Time to cross the Milky Way (at the speed of light) is 100,000 years

Reference: http://en.wikipedia.org/wiki/Observable_universe

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Andromeda Galaxy � (courtesy of Caltech) 2.5 million light years from earth

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International Space Station

Approx 440 tons = one Boeing 747 = 400 cars
Orbits the earth in 91 mins
Average speed 17,000 mph
6 crew
Launched 1998
Number of orbits to date 96,000 (approx)
121 degrees C on the sun side and -157 degrees C on the dark side – compare to range on earth

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The Stars

2,000 to 4,000 visible to the naked eye, but billions exist

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Arcturus (36 light years from earth)�Nearest star – 4 light years away

Type K1.5 IIIpe red giant star located in the constellation of Boötes and, seen from Earth, is the third brightest star in the night sky.

type K1.5 IIIpe

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If anyone else is out there – how would we contact them? How would they contact us?

Radio signals
Search for Extra Terrestrial Life (SEAT)
http://www.livescience.com/59153-how-to-search-for-extraterrestrial-life.html
http://www.seti.org/
https://en.wikipedia.org/wiki/Search_for_extraterrestrial_intelligence
http://www.space.com/search-for-life

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Jodrell Bank, Cheshire, 1957-� Radio telescope

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Voyager 2 (1977 to present)�http://voyager.jpl.nasa.gov/

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Voyager 2

Now 11 billion miles from earth
Launched in 1977 – so been going 39 years
Now outside the solar system
In 1990 took a picture of earth – “The Pale Blue Dot”
http://en.wikipedia.org/wiki/Pale_Blue_Dot

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