杏吧原创

TED talks are increasingly ubiquitous in pop culture. TED鈥檚 motto is 鈥渋deas worth spreading鈥� and it has become famous for accessible, pristinely produced 10 to 15-minute presentations on big ideas.

Of course, this makes them a prime target for satire. Sometimes this will take the form of a short, tweeted statement, such as 鈥淏lack cats are the best cats!鈥�, followed by the note: 鈥淭hank you for coming to my TED talk!鈥� I have definitely been an active participant in this satirical TED talk discourse. But I am not sure I ever will be again, because I spent the first third of 2022 preparing a real TED talk and learned that giving one is actually really hard!

My talk was in April, but preparation for it began in December, when I had to formulate my big idea and begin developing a script. In the run-up to the talk, I was practising six or seven times a day to ensure I could deliver the memorised 15-minute monologue without pauses or mistakes. I had the added complication of needing to be careful about how I moved my head because of the design of the TED microphone, which is most ideal for people with short hair and no earrings.

A major part of the challenge wasn鈥檛 the actual performance, but making sure that what I said wouldn鈥檛 leave the audience behind. Of course, I was giving a talk about dark matter. My time as a public communicator 鈥� and especially the year I spent touring with my 鈥� has taught me a lot about how often people come to discussions about dark matter with pre-conceived notions of their ability to understand what is being said. A lot of people have heard that they aren鈥檛 good at mathematics from their teachers, or their exam performance indicated to them that they don鈥檛 have a mind for science.

I generally think that is hogwash, but an audience who don鈥檛 know me won鈥檛 be aware ahead of time that my goal is to welcome them into science. Even when people do know me, they still need to overcome their internal bias against their ability to understand. So I tried a variety of ways to help the TED audience take in the questions at hand.

For example, I really wanted to emphasise that 鈥渄ark matter鈥� is something of a misnomer. The word 鈥渄ark鈥� implies that there is a colour or some other kind of relationship with light. But so far everything we know about dark matter suggests that it simply doesn鈥檛 interact with light at all, and only interacts with visible matter through gravity. If it really is a particle, light goes right through clumps of it.

The only scenario where dark matter might actually be dark is if it is comprised of small black holes. This is a possibility that scientists are taking seriously in the aftermath of the direct detection of gravitational waves 鈥� little ripples in space-time caused by gravitational interactions of extremely massive objects like black holes and neutron stars.

But I am an advocate for the particle scenario, which is the most popular and, in my opinion, the most realistic paradigm. To help people think about what it would mean for the particle to have no interaction with light 鈥� to be invisible 鈥� at one point in my talk, I stopped, held out my hands and said: 鈥淚f you put out your hands and think about the weight of having a clump of dark matter in your hands 鈥� that鈥檚 how it would feel, but your hands would look exactly the same.鈥�

With my hands cupped in front of the audience, I bounced them a little to make them think about the sensation of holding something weighted. I am fond of this example because it is something almost anyone can do and it almost feels intuitive.

This led to a question from an intrepid Twitter user who watched the talk online. In the scenario where dark matter doesn鈥檛 interact with everyday matter except for gravitationally, doesn鈥檛 that mean it isn鈥檛 possible to hold a clump in your hands? The clump would go right through them, surely?

This is a delightful question that also made me cringe a little bit because it highlighted the limit of my thought experiment. First, it is unlikely that we would be able to gather a clump of dark matter because the density is extremely low: think one particle per coffee mug. Second, if it is true that dark matter doesn鈥檛 really interact with atoms via the nuclear or electromagnetic forces, it would go right through our hands.

So, confession: you will probably never be able to hold a clump of dark matter in your hands, even if we do figure out what it is. But whether it is completely impossible or not will ultimately depend on the specific properties of the dark matter particle, and whether it truly has no interactions with everyday matter. It might 鈥� and that tantalising possibility is one reason I keep trying to understand what exactly dark matter is.