101 Facts You Didn't Know About Space

Mark S. Thompson

• Publisher: White Owl
• Year: 2020
• ISBN:
  9781526744586
• Topic: Sciences physiques
• Subtopic: Science de l'espace

The author of A Space Traveller's Guide to the Solar System shares 101 fascinatingly fun facts sure to change how you see outer space—and Earth. Did you know a compost heap generates as much energy as the Sun? Or that dung beetles use the Milky Way to navigate? Maybe you have not been into space but if you have then you will know that astronauts have feet as soft as babies! 101 Facts You Didn't Know About Space takes you on a wild journey around the Universe bringing you facts galore. Whether you are a space enthusiast or a newcomer you will find plenty of facts in here to keep you amused and entertained. "A good read, and there's something for all levels of space enthusiast, from young adults to more experienced readers." — BBC Sky at Night (UK) "Everything is explained brilliantly, the illustrations are inspirational and truly breathtaking, and, if you ask me, this is the way science should be taught in schools.... With this excellent book, we will at least be prepared for what we find when we eventually do break free of our solar system and find our destiny in the stars! Exceptional!" —Books Monthly

FACT 1

Compost heap generates as much energy as the Sun!

The Sun is at the very heart of our Solar System and on average 150 million kilometres away from us. It rises in the east and sets in the west, has been there since we were born and should be there until the day we die! To many it never seems to change, but get close up and personal with the Sun and you begin to appreciate that it is so much more than just a glowing ball of light in the sky that makes us warm on a sunny day.

The Sun is a massive ball of gas, more accurately a ball of plasma, which is an electrically charged gas. It has a visible surface which we call the photosphere, where temperatures vary between 4,500 K and 6,000 K (kelvin scale of temperature measurement) and it is here where sunspots can be seen. Directly below the photosphere is the convective zone, which is 200,000 km thick, and it is here that energy from the core of the Sun is transferred through convection (the process where warmer material is less dense and rises while cooler material is more dense and sinks). Below the convective zone is the radiative zone, which is 300,000 km thick, and where the process of radiation transfers the heat. Beneath the radiative zone is the core of the Sun and it is here that the energy is actually produced. The core of the Sun has a radius of 153,000 km and the temperatures soar to a toasty 15 million K!

The process by which the Sun creates its energy is through fusion, the joining of hydrogen molecules to create helium molecules. It is actually a little more complex than that but it takes four hydrogen molecules to fuse together to produce a helium molecule, and when they do, they give off a little bit of energy. This energy is the heat and light we experience from the Sun but the figures are vast and almost incomprehensible. Every second, the fusion process converts around 700 million tonnes of matter from hydrogen into helium, but 5 million tonnes gets converted into energy (in accordance with Einstein’s famous equation E=mc2).

The nuclear fusion happens in the core, which as we have seen is 306,000 km in diameter, but the Sun itself is 1.39 million km in diameter so the vast majority of energy production happens in a relatively small volume. The power output of the core is estimated to be 276 watts per cubic metre which, when compared to a typical household light bulb of 60 or 100 watts is not a great deal and is around the same as a fairly typically sized compost heap!

Surprising? Even though the power output is 276 watts per cubic metre there are LOTS of ‘cubic metres’ in the Sun, 15 million billion cubic metres to be exact, so if you multiply the 276 watts per cubic metre you can understand how the power output volume for volume can be less than a compost heap, but the overall output of the Sun is much greater.

The Sun as seen by the SOHO (Solar and Heliospheric Observatory) spacecraft, revealing detail in the solar chromosphere. (NASA)

FACT 2

Venus smells like rotten eggs

What does Earth smell like? It is pretty tricky to name one smell because it largely depends where you are and even on the weather. For example cities and towns smell of many different things including traffic fumes whereas a forest has that lovely ‘green’ smell we associate with nature. If it rains then the impact of drops of water on soil can release aerosol gasses giving rain that ‘fresh’ smell. Other planets have smells too but until human visitors can breathe in their air (which is highly unlikely due to their atmospheric composition) we can only guess what they smell like.

Consider Venus. Whilst Venus is the second planet from the Sun it surprises most that it is hotter than Mercury, which is closer. The conditions on Venus are really quite hostile thanks to the greenhouse effect. You will have heard that phrase before and it originates from the way certain gasses cause a planet to warm up. The warmth you feel on a sunny day isn’t solely because energy from the Sun hits your body and warms you up, instead, energy from the Sun traverses through our atmosphere, warms the ground, which then re-radiates the energy back into the atmosphere, which makes the lower atmosphere where we live nice and warm. A lot of the re-radiated energy then escapes out into space, moderating the temperature. The presence of greenhouse gasses can stop the energy radiating out into space just like glass stops heat escaping from a greenhouse.

Venus has suffered from the greenhouse effect for millions of years due to its proximity to the Sun and to significant volumes of carbon dioxide, a greenhouse gas, being released into its atmosphere. The Venusian atmosphere is almost entirely carbon dioxide and, with the release of sulphuric acid from volcanoes and atmospheric chemical reactions it even rains sulphuric acid from the thick dense clouds. The temperature in the atmosphere means the raindrops evaporate before they hit the ground. Thanks to spacecraft that have visited Venus such as Vanera and Mariner we now have a very good model of its atmosphere and can infer that the presence of sulphuric acid and hydrogen sulphide will cause the spacecraft of anyone brave enough (or stupid enough) to venture to Venus to fill with the rather pungent smell of rotten eggs as you prepare for landing!

Visible light image of Venus showing the tops of its thick dense atmosphere. (NASA)

FACT 3

You are made of stardust

Look around you, what can you see? If you are at home then you might see other members of your family, a sofa and perhaps a TV, or if you are sat in a coffee shop you might see a street scene with cars and buses. Everything you can see is made up of a multitude of different atoms from iron to carbon, but when the Universe formed over 13 billion years ago the first atoms were mostly hydrogen and helium. Somehow, something happened, some physical process turned hydrogen and helium into the stuff we see in the Universe today.

The processes that cause this almost magical change occur deep inside the stars. After the Universe formed, bringing with it a seething, boiling soup of energy, eventually matter in the form of hydrogen and helium formed. In time, this matter in the form of gas started to accumulate into localised regions until the pressures inside became so high that nuclear fusion started to take place. Fusion is a physical process whereby atoms join or fuse together to form another type of atom. The onset of fusion marks the birth of a new star and this first generation of stars would have been almost entirely composed of hydrogen and helium.

For millions of years, these new stars would sit, quietly fusing hydrogen to helium in their core and as a byproduct emitting energy in the form of heat and light (among other emissions). Eventually the star would end up with a helium rich core.

Skipping forward a few billion years and the stars we see in the night sky start their lives in much the same way and can remain stable like this for billions of years. The stability is a beautiful balance between the force of gravity trying to collapse the star and the thermonuclear pressure from fusion trying to rip the star apart.

Once a star has a helium core, the temperature and pressure in the core is not high enough for helium fusion to occur, leading to a decrease in the thermonuclear pressure. For a short while, gravity starts winning and the core contracts, leading to an increase in core temperature and pressure and the start of helium fusion. The fusion of helium creates carbon in the core of the ageing star and for stars like our Sun it is the end of the road and the star will soon die. More massive stars live longer, and eventually carbon fuses into oxygen, then into silicon and finally iron. Even for the most massive stars in the Universe, this is as far as they can go. The thermonuclear pressure drops and the star collapses in an instant under the immense force of gravity leading to an explosion.

The process of synthesising elements inside stars like this is known as nucleosynthesis, and as the stars die the elements created inside them are scattered throughout the Galaxy. With the new elements distributed around space, they eventually get caught up in new regions of star formation and, as the stars form, the heavier elements can now play their part in the formation of planets and ultimately life.

It is true that every atom in your body has at some point, been through the core of a star.

Star cluster Westerlund 1 is 15,000 light years away and is revealed in all its glorious detail in this image from the Hubble Space Telescope. (NASA)

FACT 4

Footprints on the Moon will last for millions of years

Walk around the beach or across a field and you will see the imprint left by your feet. Come back to the same spot a few days later and you will more than likely find no evidence that you were ever there. The process that mysteriously removes your footprint is known as erosion and it can only occur on a world with a reasonably dense atmosphere like Earth. At the surface, there are about 100 billion billion molecules per cubic centimetre in the Earth’s atmosphere, but on a world like the Moon there are only 100 molecules per cubic centimetre.

Erosion is a term that explains the process of the movement of surface material from one location to another. This transportation of surface material can be through movement of water, wind or even ice in glaciers. Wind and water transportation are probably the more familiar to us as they can be seen on very regular basis, with wind dislodging surface particles of soil or sand and rainfall causing water movement over the surface. Both of these require an atmosphere because without an atmosphere there will be no wind nor any rain. These are plentiful on Earth, especially in the UK, and easily erase a footprint, but on the Moon the situation is very different.

The Moon does have an atmosphere but it is so thin it is of no consequence and certainly not thick enough to experience any weather. The Earth has an atmosphere thanks to a long history of strong geological activity like plate tectonics. The movement of the surface crust leads to volcanic and other activity which feeds the Earth’s atmosphere; however on the Moon there are no such processes and it is to all intents geologically dead. Any gasses that might find their way out of the lunar interior will soon be lost to space. Gravity is a significant factor in an astronomical world having an atmosphere, and the Moon, which is only 1.2% the mass of the Earth, simply does not have enough gravity to hold on to an atmosphere. The proximity to the Sun is also a factor with the constant stream of charged particles known as the solar wind pushing against any gas hugging the Moon; the weak gravity is unable to keep hold of it.

When Neil Armstrong went to the Moon back in 1969, he and Buzz Aldrin left their footprints on the surface. The lack of atmosphere means erosion on the Moon is a slow process but there is still erosion, not from the movement of surface material from wind or rain but by the solar wind itself and from space rocks known as meteorites. There is plenty of evidence of meteorites having hit the surface of the Moon from the huge dents left behind that we call craters. It is possible a big meteorite could smack into the surface and obliterate the footprints tomorrow but it is more likely that the solar wind and tiny micrometeorites will very slowly and gently wipe away the surface features. This process of erosion is much slower than the erosion we experience and it could very easily take millions if not billions of years to remove evidence that the brave astronauts of Apollo 11 visited our astronomical neighbour.

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