Reduce plastic use – why and how

Plastic is a great substance. It keeps many products fresh and provides great protection against external influences, such as the sun, wind and rain.

Ever since marketers in the 1950s realized that you could produce a lot of plastic if the consumer immediately threw it away, we have a problem, instead of the many solutions that plastic can also offer. The mountain of plastic waste is growing enormously. If only it were on a mountain, then we were lucky! Because a large part of the plastic ends up in the environment. And plastic does not decay, or extremely slowly.

Many people in Bocas del Toro throw the plastic off into nature. Often it is the locals who do not see the environmental problem. An American who came here in this beautiful nature reserve saw all the rubbish and built a Plastic Bottle Town with a group of volunteers. Including this Plastic Bottle Castle. A statement. You can rent a condo there.

A lot of plastic ends up in animals. Many fish, birds and (sea) turtles check whether it is food, which means that quite a lot of plastic enters their gastrointestinal tract. That becomes soft and often intertwined, making it more difficult for them to eat and digest their food, and therefore die.

When the plastic gets smaller, the size of invisible plastic particles, it spreads in all plants and animals. Including us. Did you know that on average you take in the weight of 1 credit card per week? The larger part we breathe in, the rest we swallow through food. Much of this plastic does not leave the body. It disrupts the hormones and makes you less fertile. Plastic reduces the functioning of the autoimmune system, which makes it easy to get all kinds of ailments and to die more easily from, for example, a strong flu.

On the average, a person takes in the weight of 1 credit card in plastic per week.

Don’t believe in technology or government.

Don’t believe in incinerators. A lot of plastic is difficult to burn. Many plastics release toxic substances if the temperature is not extremely high. Some plastics, such as PFAs, are almost impossible to burn. PFAS will never decay and this substance will become more and more common in everyone in the body.

Don’t believe in recycling. There are far too many types to sort. And even worse, they are often combined within 1 package, often even fused in layers. The only thing that is possible is to heat the various plastic waste to about 80 degrees and then deform it.

Don’t believe in law. Legislation is now being made in the European ‘Green Deal’ to ban substances, but the Plastic Lobby in Brussels is too strong. The main principle will remain that new substances may enter the market. Instead of the principle that new substances may not enter the market unless it is proven that they do not cause environmental damage.

Do believe in yourself

It is good for your health and that of everything that lives on Mother Earth.

Of course you don’t buy plastic tableware. Ban plastic straws and buy bamboo or pasta straws instead (yes, pasta!).

Buy what you need. For example, a Fairphone seems more expensive, but it can be repaired by yourself and it will last at least five years.  That is 1 or 2 years longer than most other mobile phones.

Use wooden pegs. Slightly more expensive, but much more durability. You can easily and cheaply buy wooden clothes hangers on the second-hand market or reuse shop. Cheaper and more durable than the plastic variant and ultimately cheaper.

Believe in reuse.

Reuse plastic bags. You take them with you in a dishwashing machine and wet bags stick nicely to the tiles above the counter, where they dry.

Screw a large box to a wall and throw packing material in it. You can easily reuse it (also nice for Sinterklaas surprises).

Put a sticker on your mailbox that you don’t want any advertising brochures.


Close your front door with an empty shopping bag with your empty bottles, but also some plastic bags. You can put your new groceries in there, such as your vegetables, fruit, and so on.

Do you see a striking amount of packaging on a product that you want to buy? The simplest is not to buy the best. But a good second option is to ask the seller or cashier in the supermarket where you can leave the waste. Then you leave all the plastic packaging there. If this happens regularly, the management is not happy because disposing of waste costs a lot of money.

Going out?

Before you close your front door, bring your refillable water bottle. Saves you money too.

If you are away for a bit longer, bring your own food. That is a better, healthier and much more plastic-free alternative than the packed snacks you can buy in gas stations along the way. And it saves you a lot of money.

If you order water in a cafe or restaurant, say that you want the water straight from the tap in a glass. Say that you are happy to pay for it, but not for a plastic bottle of water. This works very well in Western countries. It works astonishingly better in Latin America, because there the people have learned to sell plastic bottles, while every restaurant or café has separate large barrels with drinking water.


Cheap electricity at home with the battery pack of your electric car

On board the Ya is a charger that can convert power from mains power for the battery bank. This charger is necessary because the batteries must be charged to 100% every three months.

This same device is also an inverter, which means that it converts battery power into regular mains power, in our case 230 Volt. various appliances such as the induction cooker, the microwave and the bread maker work on 230 Volt.

A battery bank from a Tesla

Peak and off-peak current and the battery of your electric car as a buffer

Normally you charge your electric car to drive it. But many cars have about 50 kilowatt hours and you don’t run that empty so quickly every day.

Then it’s nice to start making money with it. People who have an electricity contract with variable prices at home try to charge their car battery around noon, when electricity is cheap. The nice thing is, there is now also a smart device for the electric car with which you can convert the power from the battery and feed it back into your own socket in your home via the charging cable. In the evening when electricity is expensive, you can cook and so onwith the power from your car batteries.

Someone has already managed to earn money for a month. it saves money and you live a little more fossil-free.


The Ya has such a smart device since 2013, a Studer Xtender. In addition to charging and converting, the Xtender can also supply power back to the grid. It happened once during my first fossil-free trip around the world in 2017. I did the quarterly battery maintenance in a Panamanian marina: charging the batteries with mains power. But I stayed in the marina for a few more days and I left the plug in. The tropical sun shines brightly here, so the excess energy went back into the electricity grid via the socket on the jetty.

Now there are many American boats in Panamanian ports and Americans are major consumers (their average consumption is more than twice as high as the energy consumption of a Dutch person). Reason enough for the marina management to take a quick tour of the electricity meters on the dock every morning. On the second day, the employee said my meter was broken and put my plug in another socket.

On the third day, the employee said that the meter was also broken and plugged my plug into another socket. I asked him what the problem was and he said the meter was running backwards. I replied that it made sense, because the Ya generated more than was consumed. He couldn’t believe that. The marina manager and an engineer had to come in to show that it really was the case.

The manager thought it was almost a wonder of the world and he invited me to give a presentation in the nearby hotel. The hall was packed, the whole marina had turned out for it, especially the Americans. America is the country where electricity is a self-evident necessity of life, like water from the tap. There is a plug everywhere. If you buy a device on the internet that runs on solar energy, it will explicitly say: without plug.

Whether the fossil-free message of the presentation reached the American audience, I do not know, because the psychological distance was great.

Innovation versus Tradition

Do you also wonder if every innovation is so innovative? So let us try it out and start a race between an innovative, super light, easy to handle, light cayacu and a cayacu built in the 2000 years traditional way.
Who will winn?
An honest race between Tomas of the Ngobe tribe in Bastimentos, Panama, and me. See the race!

Who will winn?

Some tips to save yourself an airconditioned life.


At first sight the airco (or the reversed heat pump) is a great thing. How nice and cool on the hot days! But realize, it starts to take over your life. You get a bit addictive in the first place; your definition of a hot day inflates bit by bit. It is also a bit less healthy then experiencing the daily variation of temperature. And, it hurts the wallet. You quickly use many kilowatthours a day.

And, you can keep your house pretty cool without an airco.

Here are some tips, mostly from the local people here in Latin America. Now when writing this, it is 35 degrees Celsius and it is pleasantly cool. So here some tips straight from the experts.

Insulated house? Keep the air cool

Is your house well insulated, then the heat will hardly go through the walls. So:

  • Open your windows a bit in the night, to let the cool air come in. Make sure you open a window as low and as high as possible in the house. Thus you create a chimney-effect and the warm air will quickly be replaced by the coolest early morning air.
  • In the morning you shut all doors and windows, like you do in the winter time, and no hot air comes into your house.
The original house in the tropics has only one wall and the insulation is nothing. But the coverage against the sun is great: roofs with large overhangs, and a lot of trees and plants. there are hatches before the windows if one can pay it.

Cover from the sun

  • Most important is to cover the windows. The summer sun can deliver 1 kW per every square meter of (double/triple) glass. Preferably cover the outside, but if you don’t have that, close the curtains. Thus, you stop the sunrays heating up the house.
  • Do as the tropical people do and plant a tree. It is long term, cheap service delivered by nature. the higher latitudes the better it works, because the sun angle is lower.
  • Or if you prefer to spend more money, then install sun covers over your windows.

Minimize concrete, maximize vegetation.

Concrete terraces heat up and stay heated. Vegetation on the other hand, regulates the heat, by a smart way of using the water in and on it, and by taking some energy from the sun to grow.  You create a cooler local climate around your house. So:

  • Lift tiles and plant trees and plants in the earth.
  • Put pots to the outside walls  and put plants in it.

Use a fan

Just the movement of the air along your skin, has a cooling impact.

With no wind, also outside on the fan works great

There are fans from 1 watt to 300 watt. The first is silent and great to put close to your head when you sit in a chair or behind a desk.  The latter can blow your wig from your head. Such a thing is enough to put in a big room or on a terrace or porch and move all the air there.


  • Buy yourself a fan, small or large, just the one that suits you for your purposes.
  • Still to hot? Put a bunch of ice cubes, or cool, icy water before the fan. Even a wet cloth can help, especially when the air inside is dry.
The difference between your place and mine is that so now and then a monkey comes nosing around and checks if everything is cool here ;-).

Technology as the solution to the climate change problem – or not?

The technology will solve climate change – or not?

A new invention has been made that allows batteries to store twice as much as the most modern batteries. A solar panel has been invented that is hyper bendable. Something has just been invented to spray solar cells onto a surface. But will they solve climate change? That chance is small.

A look at the past says a lot. The Industrial Revolution would make the products so cheap that everyone could afford them. That’s now maybe 10% of the world population that structurally can afford that. That’s all.

You could even say that the technology destroyed more than it actually solved in the first place. Because at the beginning of the last century, a massive war industry arose and the mass production of weapons meant that anyone could be shot.

The next technology solution were the crop protection products. They would solve the world food problem. Nothing of that came true.What did help were the IMF and UN based food programmes, effective since the late 1970’s (and shrinking now). This reduced the starvation with big numbers. The crop protection products like DDT made the opposite become true, because a lot of agricultural land is now toxic in developing countries, while companies such as Bayer (bought Monsanto) and BASF have grown into large multinationals.


The industrial revolution only started to have an effect on the poor when a counterpower of workers arose. Things started with the right to strike, then insurance and more regulations whereby large groups received a wage with which they could buy the -indeed cheaper- products. Of course, this has not yet spread widely across the world, it only concerns mainly Western countries.

The crop protection industry only started working after regulations. DDT was banned and as more data became available on the damage, more and more variations of crop protection were banned. Did techonolgy help solving the starvation? The opposite has become more true, because a lot of agricultural land is now toxic in developing countries, while companies such as Bayer (buyer of Monsanto) and BASF have grown into large multinationals., but the damage is limited by regulation and control.

Choices, choices

With every new technology there is a choice as to what we will do with it. If you do nothing, the market will do its job and – in short – shareholders of a company will become very rich.

It is often a choice. What are we going to use our new technology for? It is the personal choice for solar panels, it is also the choice of what is sensible for the public interest. For example, the choice to vote. For example, we now see that many national governments are still stimulating the fossil fuel industry with tax breaks and subsidies. A study showed that, for example, the Dutch State spent 17.5 billion on fossil fuel companies. It led to questions from parliament. A self-investigation followed. The State came to 4.5 billion, but had to admit that not all figures could be revealed. It led to more questions. These numbers are still to come.

Of course, politics has perverse tendencies. But isn’t it the world upside down when our chosen establishment, with a strong policy of fossil freedom, spends billions of our tax money to fossils?

Strict and clear regulations are important now. These appear to be insufficient; our governments spend more billions to fossils than to fossil freedom and can get away with it. This leads to the question if you want that? And democracy wise, do you still want to vote for such a shady government?

So coming back to the question in the header, technology itself is just a condition and we are doing great on that. Fossil free living is already cheaper than fossil living. But nothing will happen if you don’t chose to allocate for it. For your private use, and -perhaps of more importance- for strict and clear regulations. These choices are finally your choices.

Views on sailing through the times.

For centuries people turned to the gods for good sailing. Neptune and Aeolus had to be propitiated with a lamb or a jug of wine. People later discovered sailing routes and trade winds and this is the first rationality. But, to be on the safe side, they continued to pray for a safe journey.

In the Classic Greek times, you’d better sacrifice a lamb and some wine to Neptune, or he would make a simple trip into a long and bad journey.

With the arrival of the steamships, the world view changed. The sailing routes were respected, but together with the machine you got there. This developed into the situation in which the current generation lives. An old fisher man said about this: “Nowadays you can even motor against current and wind with your yachts to wherever you want to go.”

It costed a lot of first quality coal, and oil later, but if the wind is against, the ships engine can still bring you in time.

Now, a new world view is emerging. Our rational ability is so well developed that we use more sophisticated means than just the machine-against-current-and-wind. Reliable weather forecasts, advanced means of communication and smart routing make more nuanced choices possible. There are more and more options to make a crossing, whether that is from IJmuiden to Lowestoft, or an ocean crossing. Do you want slow or fast, a lot of wind or less? The choice is broadly up to you.

That is a good thing. The other good thing is that these options do not have to harm the future of our children and children’s children.

If a simple sailing yacht requests a weather report, the skipper can get more routes, all based on various models. Here are shown three of them.

Possibly connecting a car alternator to your propeller shaft?

Something a bit more this week, for skippers only I am afraid. And only two pictures (but  one of them is artistic!).

The car alternator

As soon as a sailing yacht sails, it speeds up. The propeller in the water starts to turn. This rotation can drive a dynamo and thus generate electricity. Just as a windmill needs a little wind to deliver, the propeller only turns through the water at some speed. That’s a law of physics. At about five knots, the propeller usually turns hard enough to provide electricity.

Here is the description of whether it will fit on board your sailing yacht at all. (But there will not follow a technical description how to install it.)

Hydrogeneration works well with a fixed propeller, but it works better with a variable propeller. The propeller must be of some size. Small propellers require higher speeds.

It is striking that the rotation of the propeller on most courses has little decelerating effect on the speed of the boat. For example, at a speed of 5 knots, the loss of speed is no more than a quarter of a knot. There is a clear loss only on upwind rates. On that course, all the forward energy is needed to gain speed. With the hydrogeneration in operation, the ship becomes visibly more glued. If additional power is necessary via hydrogeneration, it is better to drop 10 or 20 degrees on that course.

In practice

In practice, hydrogeneration can already yield 50 to 100 watts from a boat speed of five knots. It depends first and foremost on the prop and then on the technology behind it. 50 to 100 watts may not seem like much, but when underway on the high seas the system works 24 hours a day and 50 to 100 watts for 24 hours is sufficient to provide an energy-efficient ship’s household with energy.

With a score of 100 watts, hydrodynamics already generates 2.4 kilowatt hours per day, which is more than solar and wind energy combined on most ships. If the boat speed increases, the efficiency becomes even higher. Hydrogeneration on fast catamarans yields ten or twenty times that.


The huge advantage of hydrogeneration is security, reliability. Long-distance sailors are often concerned about whether they will arrive at their destination with enough energy. With the use of hydrogeneration, the reverse often happens: the battery bank is full on arrival.

The propeller shaft alternator; the oldest form.

Long before solar panels or wind turbines were used on board, sailing skippers already used the propeller shaft dynamo. That was a very welcome additional energy supply because of the energy-consuming lamps and the relatively expensive batteries. Surprisingly, this system is hardly found on board anymore.

The operation of the propeller shaft dynamo is simple: when the propeller starts to turn under sail, it drives the dynamo via a pulley and a V-belt, which supplies electricity to the battery.

Schematic sketch

This is a schematic picture of a propeller shaft alternator. A dynamo is mounted next to the propeller shaft. There is a small pulley on it. A large pulley is mounted on the propeller shaft. When the propeller starts turning, the large pulley also turns and drives the small pulley on the alternator via the V-belt. The alternator therefore rotates and supplies the current to the battery.

The propeller shaft alternator is a cheaper supplier of electricity than the hydro generator from the shop, even if you have it installed.

Align propeller and alternator

When using a propeller shaft dynamo, the propeller and dynamo must be properly matched. Because when the propeller turns, the dynamo also has to turn fast enough to supply power. The speed of the propeller and alternator is matched with the size of the pulley on the propeller shaft. So there must be space around the propeller shaft to mount such a pulley. You can easily calculate how much space that requires. The starting point for the calculation is that the propeller rotates stably at a sailing speed of 5 knots.

Alternator speed

The speed of an alternator is easy to determine, because it is stated on the specifications. An ordinary car alternator usually delivers well at 1000 RPM (Rotations Per Minute). That’s what we assume here.

What is the propeller speed?

You can determine how many revolutions the propeller makes in three ways. The first and simplest is to measure the RPM with a tachometer gauge, an expensive thing that nobody has.

Sound app

The second is by using a sound app on your smartphone. Place a piece of tape on the propeller shaft with a piece of tape sticking out. Place a plank next to it and every time the protruding tape passes it, you will hear TICK. Record this on a phone for exactly one minute. If you play it in slow motion or enlarge the visual representation, you can count the taps. That is the number of revolutions per minute.


The third way is math. Let’s say you have a 14″ X 15″ propeller. The diameter is then 14 inches. The pitch is 15 inches. When the tip of the propeller has made one revolution through the water, it has theoretically traveled 15 inches. How many revolutions per minute is that at 5 knots?

5 knots, that is 5 X 1852 meters = 9260 m/hour.

RPM goes in rotations per minute, so that would be 9620 : 60 = 154 meters/minute.

In inches/minute that is 154 X 39.37 = 6076 inches/minute

To get into the RPM, we need to divide the distance through the pitch: 6076/14 =380 rpm. This is the theory. The propeller with a pitch of 15 inches appears to cover much less distance after one revolution. A propeller does not turn through water like a wood screw through wood. Water is flexible, so it has less grip on the propeller. This phenomenon is called slip. When the propeller is driven through the water, such as when loading, there is so much slip that the propeller runs at two-thirds of its theoretical speed. So: 2/3 X 380 = 253RPM. The propeller turns at 5 knots, so 253 RPM, and the alternator must turn at 1000 RPM. The ratio between the alternator pulley and the propeller shaft must then be 253 : 1000. That is 1:4. If the alternator pulley has a diameter of 5 cm, the propeller shaft pulley must be 20 cm. If that diameter fits around the propeller shaft, then the propeller shaft generator can be installed and it now only concerns the technical implementation.

Some numbers

we belong to the 10% richest in the world and we cause 50% of the environmental damage. In the first 100 years, hardly anything changed on this planet.. The Earth took it. But then, with a slow response, the nature the Earth is changing.


70% of all wildlife on earth has gone

Man and farm animals represent 94% of all mammals

Life at sea

50% of life in the oceans has gone

An estimated 80% of the fish has gone in 50 years

Since 50 years plankton is dying 1% per year

The Earth

In 1900-1930 the temperature of the Earth’s atmosphere rose 0,22 degrees Celsius each year, but now it rises about 0,33 degrees Celsius per year.

In the current pace, the earth’s temperature will have been risen 4 degrees Celsius in 2100. Not 1,5 degrees. The sea level will be risen 1,5 meters.


A long food way short: Every man eats plastic that equals the weight of one credit card per week.

My number

Statistically I would become 84 years old. So I got 20 years to live with less, value what I have, and go down with my consumption. 20 whole years to impove the world.

What is your number?

A history of water and poop management

Did you know that the French word la rue (the street) originally meant the sewer, the drain?

And so it was. You washed in a convenient place, next to the house a gutter ran into a ditch. That was sometimes more difficult in a city, but otherwise you put a plank over the gutter. There was a bit of turd here and there, but who complained about that?

Things got neater with the arrival of the poop box. In a separate hutch, on the leeward side of the house, there was a a barrel with a lid. That barrel had to be emptied. If you lived outside, the poop box was near a ditch.

This is the classic poop box. A separate room, often outside the house. There is a hole under the wooden lid and underneath it is a large barrel that is emptied once a week.

If you lived in the city, the poop box was mandatory. The poor households, often 6 or more families in a three-story house, shared a poop box that was downstairs in the small backyard. With families of an average of 5 people, it was often quite busy. So at night when the police couldn’t see it, the street was still regularly ‘la rue’. So unhygienic. It also always smelled in the city.

The poop box was emptied into a cart and it was brought outside the city, first to the farmers, but that also became too much. That lugging around with poop was also unhygienic and the manure heaps outside the city formed a new problem.

The poop bucket is emptied into the cart here. The ladies and gentlemen on the left are ready to hand in their bucket.

In the 18th century, the link between non-hygienistics and diseases such as cholera was seen. Many cities already had a water network, such as Amsterdam, but a city like Rotterdam did not. Cholera broke out there in 1832. In response, Rotterdam created a water network of canals through the city around 1850. The water slowly flowed through the city. Very easy, your poop box could now go straight into the girth. It was diluted quite a bit. And you were immediately provided with your drinking and washing water. It could not be better. The rich went to live on such a canal; that can still be seen in the beautiful large mansions and the wealth of trees.

By cleverly connecting a small river (the Rotte) and the large river (the Maas) with a network of canals, a flow-through system was created for the discharge of waste water throughout Rotterdam

It worked great. So good that the entire water network became a source of germs again. And also because at the end of the 19th century the cities became more densely populated.

What now?

A revolution in poop management

From the end of the 19th century, the water supply was introduced, followed by the sewage system. The water came into every Rottterdam house between 1900 and 1920. The water was filtered surface water with a generous portion of chlorine.

The construction of the sewage system followed and that system became a complete system in the first half of the twentieth century with a sewage treatment plant outside the city.

What was so special is that the faeces, together with the urine, were immediately diluted with water and flushed into a sewer.

In fact, we have only been disposing of our poop for a century now by diluting it sur place with water. That direct dilution made it really hygienic.

Also for the longer term?

This dilution, a flush, takes about 8 or 10 liters. Flushing accounts for the largest share of our water consumption.

We are now seeing the water quality decreasing. Even for the technically advanced water companies in the Netherlands, Rotterdam, it is becoming difficult to produce good drinking water.

What will the future look like?

Less is more, the dry toilet as a new revolution

We are now technically much further along. We now have plastic. Even plastic that breaks down fairly quickly. There are now dry toilets that do not require water to drain. It will soon have to be installed on many boats, because boats are no longer allowed to emit poop.

Poo and pee even remain separated in this dry toilet, so that no ammonia is formed and the poop quickly stops smelling.

Your poop comes in a bag and your pee goes into the sewer through a separate exit. Once a week you take out the bag (no, not a dirty job) and throw it away – for example as compost?

This saves 30-40 liters of water per person per day, which currently goes straight into the sewer as drinking water.

This is a selection of the dry toilets that are available. From DIY to classic oak models, but there are also from ‘camping fold-out rack’ to Art Deco.

There is also another option for our future. With the existing flush toilet we will eventually collect rainwater and there will be a tank on your house, with a collection and pumping installation. That tank must be a big one. Below is a picture of the smallest type of tanks.

I know what I choose. The dry toilet is already on board the Ya.

Water tanks for a (very) small household.


Future developments in batteries

As long as energy consumption continues to increase, energy storage is one of the biggest challenges for the future. Certainly for us, belonging to the ten percent richest in the world. It is precisely these countries that use the most energy.

The supercapacitor (supercapacitor) can hold electrical energy and is very light. It can be charged very quickly and can provide a lot of energy. A disadvantage is that it is not yet able to retain the electrical charge properly at the moment. The capacity is also small. Supercapacitors have long been used to power the flash light on a camera. They have recently also been used in cordless drills.

Supercapacitors are pipe-shaped and not big. You can easily put them for example in the frame of your electric bicycle.

The saltwater battery works on the same simple principle as a lead-acid battery. Only the chemical reactions are not so bright. A saltwater battery therefore requires a lot of space and is relatively heavy. However, many more charging cycles are possible. The saltwater battery has recently been industrialized and is suitable for large ships. The advantages are durability and simplicity, also of maintenance and repairs.

Make one yourself? check

A Chinese car battery manufacturer says it will soon come with a so-called ‘condensed battery’ that could contain 500 watt hours per kilo. This would be very light and even interesting for aircraft.

With silicon as a basis, a relatively light battery could be made. Even lighter than an LFP battery. The grain size of the silicon then only needs to be a few nanometers, making it more expensive than gold. A method has recently been invented to separate the silicon from old solar panels and then grind it into nano-granules. All this in a simple and cheap way. Now that the development of solar panels continues, the old panels automatically become waste. The circle seems complete: who knows, discarded solar panels may be the basis for the future battery.

It is all much promising, and all these developments makes man optimistic. If mankind makes a small step, it will end up in a giant leap.

f you want to invest in a battery at home, please don’t wait, because many promising developments are soon overtaken by new, even better discoveries. And before they become available in practice, it will be ten or twenty years later. For example, it took three or four decades before the solar panels from space projects were first found on decks of boats here on earth.