How many people would we need to send to colonise Mars before natural procreation (sex) would ensure a genetically viable colony?

On Hamman Time, 5fm - Questions and answers provided by @jonoweltman


Question:

How many people would we need to send to colonise Mars before natural procreation (sex) would ensure a genetically viable colony?


Answer:

Between 14,000 & 44,000


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In 2002 Anthropologist John Moore created a model that showed that a minimum of 160 people would be needed to create a stable, genetically diverse, population that could survive in isolation for 10 generations or 200 years.

Before this study attention had mainly been focused on cryogenics, sperm banks and military-style modes of operation but scientists believe "the 'right stuff' for a journey into space is the family - a million-year-old institution designed to assist reproduction."

160 people would produce around 10 potential marriage partners per person. 

This number could be reduced to 80 people through a little social engineering. By having children later, mothers between 35 & 40, we can extend the length of a generation and then need less people. 

This study, however, assumes that after 200 years they will return to Earth or will be joined by a fresh genetic pool of humans.

In 2014 Anthropologist, Cameron Smith, presented a model showing that an initial colony for a new planet needs to be between 14,000 & 44,000 people. 

40,000 tends to be the safe number to ensure that there is sufficient genetic and demographic diversity, giving the settlement the best chance of survival.

This would consist of at least 23,000 adults of child bearing age and ensure that the group maintain good health over at least five generations despite, increased inbreeding, depressed genetic diversity due to the founder effect, demographic change through time and expectation of at least one severe population catastrophe.

How can it be said that an International Space Station Astronaut experiences 8 years in the same time we experience 6 months?

On Hamman Time, 5fm - Questions and answers provided by @jonoweltman


Question:

How can it be said that an International Space Station Astronaut experiences 8 years in the same time we experience 6 months?


Answer:

If a years is defined as 365 days and a day is defined as the time it takes the Sun to return to the same position in the sky then this will happen almost 3,000 times (or 8 years worth) in 6 months for a Space Station Astronaut or Cosmonaut.


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How does this work?
The International Space Station began in-orbit construction in 1998 and has been manned since October 2000. It is also visible to the naked eye and can be seen moving across the night sky.

It currently orbits at an average height of 400km and the Astronauts there spend their days testing the effects of Space, Space Walks and Microgravity through various Experiments. In effect it is a Space Laboratory.

In order to not fall back to Earth and burn up in the atmosphere the ISS needs to travel at a speed of around 27,000 km/hr

At this speed the ISS goes around the Earth once every 90 minutes.

If we consider a day to be the definition that we use here on Earth, being the time it takes for the Sun to return to the same position in the sky, as opposed to the passing of absolute time, then the fact that an ISS astronaut will see almost 3,000 sunrises and sunsets means that they will have experience the 8 years worth of days in a 6 month deployment.

Interestingly enough there is actually an absolute time difference of about 0.0000000014% so when an Astronaut returns after 6 months they are 0.0002 seconds younger than us.

How do Microwave Ovens Work?

On Hamman Time, 5fm - Questions and answers provided by @jonoweltman


Question:

How do Microwave Ovens work?

Answer:
Microwave ovens emit radiation (form of energy/heat transfer) in waves. These waves agitate water molecules in food which in turns creates heat which then cooks food.

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Invention
Microwave Ovens invented as a result of an accident.
Percy Spencer, self taught orphan who left school in primary school, was head of the second most important war project after the Manhattan Project - RADAR development, at the Raytheon Corporation.

In 1939 he was standing in front of an active radar and the chocolate bar in his pocket melted.

This wasn’t the first accident of this nature but he was the first to explore it. The very first thing microwaved on purpose was popcorn!

Raytheon patented Spencer’s design and it was originally called the “Radarange”.

The Science
There are two flavours of Radiation. Ionizing & non-ionizing.

Ionizing radiation has higher energy, enough to free an electron from an atom and thus make it charged or ionized. This type of radiation is extremely dangerous as it can alter the structure of cells and damage our DNA.

It comes in 2 forms - particle or wave

Non-ionizing radiation has much lower energy and ranges from a heating effect, high current (microwaves) to no thermal effect at all, low current (power lines)

This range of wave radiation is called the Electromagnetic Spectrum.

Practical impact
Radiation is the greatest challenge to extended crewed Space Exploration as radiation is how energy is transferred in a vacuum.

The Sun emits light (Electromagnetic wave) and particle radiation constantly. The majority of the harmful radiation is filtered out by our atmosphere and by UV protection here on Earth but in space there is no atmosphere to protect us.

To make matters worse the Sun can experience events from Solar Flares to Coronal Mass Ejections almost without notice, all of which can have a very deadly effect to astronauts in Space.

What happens when you put two rods, of the same metal, together in Space?

On Hamman Time, 5fm - Questions and answers provided by @jonoweltman


Question:

What happens when you put two rods, of the same metal, together in Space?


Answer:

They fuse together in a process called cold welding.




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The Science
Cold welding was first recognized as a general materials phenomenon in the 1940s.
Description by Richard Feynman:
The reason for this unexpected behavior is that when the atoms in contact are all of the same kind, there is no way for the atoms to “know” that they are in different pieces.
On earth there is a layer of oxide that separates 2 surfaces and this layer re-forms each time they are seperated. 
In Space (or a vacuum) this layer is gone after the first contact and thereafter the atoms come into direct contact with each other.

Practical impact
Many early satellites had minor to major failures due to cold welding. Even surfaces that were designed, in theory, never to come into contact with each other do come into contact due to pressurse and forces experienced during launches, maneuvers and deployments.

There has been and continues to be much study in this area and the development of materials that do not cold weld, like ceramics. In parts where metals & alloys have to be used engineers now design them such that any contact surfaces are made of different metals to avoid cold welding.

Of course there is also an upside to cold welding in that it makes fabrication and repairs in space easier than on earth, where a molten phase is required when welding surfaces together.