Nuclear waste is very dangerous, and will remain dangerous for hundreds of thousands of years. Therefore, humanity has planned to leave warning messages to future civilisations around permanent nuclear waste storage facilities. However, this turns out to be an extremely difficult task, as the messages are being sent to a completely unknown recipient, so we need to convey the message using as little prerequisite knowledge as possible.
We can't just use our existing warning signs - whilst this would be effective for warning present-day explorers, future civilisations may not know the meaning of them. So, we have had to come up with some creative ways to convey warning messages into the very distant future.
One way of warning of the dangers of radioactive waste far into the future is to physically alter the landscape around the storage facilities, to scare away anyone who discovers it.
One method of altering the landscape would be to create "spike fields" - giant fields of steel spikes, designed to instil a natural response of fear in anyone that sees them. However, this may not work - the discoverer may not have the same reaction to sharp objects that present-day humans have.
Another way that has been suggested is to create vast planes covered in enormous concrete blocks, with very tall steel spikes sticking out the top. This, like with spike fields, is designed to instil fear in the observer, in the hope that they will not attempt to explore the facility.
Another method that has been suggested is to create enormous, house-sized, roughly cut blocks of concrete arranged in an irregular grid. This is designed to cause the observer to feel a strong sense of discomfort, dissuading them from entering the facility.
The problem with using these methods is that we cannot be sure whether the discoverer will see the landscape as scary and foreboding, or as interesting and inticing. These strange landscapes may encourage people to explore the facility, as they will be curious as to what is contained within - which is exactly what we do not want to happen.
We have come up with a written message for future civilisations, to be left at the storage facility. The message reads as follows:
This place is a message... and part of a system of messages... pay attention to it! Sending this message was important to us. We considered ourselves to be a powerful culture. This place is not a place of honor... no highly esteemed deed is commemorated here... nothing valued is here. What is here is dangerous and repulsive to us. This message is a warning about danger. The danger is in a particular location... it increases toward a center... the center of danger is here... of a particular size and shape, and below us. The danger is still present, in your time, as it was in ours. The danger is to the body, and it can kill. The form of the danger is an emanation of energy. The danger is unleashed only if you substantially disturb this place physically. This place is best shunned and left uninhabited.
The hope is that this message will be understood by whatever finds it, and will warn them of the dangers of the storage facility. The message would be translated to every UN language, as well as leaving space for future discoverers to inscribe the message in their own language.
Another suggestion is to genetically engineer bioluminescent cats, which would glow in the presence of radiation. A trusted group of people would establish an "atomic priesthood" - a religion, which through its traditions and culture, warns of the dangers of glowing cats; with the hope that the discoverer will see these glowing cats, and therefore not approach the storage facility.
The reason for this suggestion is that, if you were asked to name the longest lasting organisation that still exists today, your best bet would probably be the core of the Jewish religion, or the Catholic church. Therefore, experts suggest that the best option is to create a religion to convey this message.
It was very interesting to research this topic, and I would highly recommend these two videos that I watched whilst researching it:
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