I was reading an article online from the Express when I read the following: “Black holes are often found at the hearts of galaxies and up until April this year have been purely theoretical.“ The statement threw me for a bit of a loop, mostly because black holes have been an active part of astrophysics since the discovery of Cygnus X-1 in 1971. Using the day to day word theoretical misleads the general public into thinking that black holes were not confirmed in science until this past April with the discovery of M87*’s shadow. This is a dangerous statement to make.
In day to day language, theory is used to mean a hunch or an educated guess. However, in the sphere of science, a theory is an explanation of what something is or how it works. Theories are often large bodies of work and research and are quite detailed.
Take gravity for example. Newton’s law of universal gravitation does not explain what gravity is, it only shows mathematically how two bodies affect each other through gravitational attraction. It is the theory of general relativity that explains how gravity works and what it is (a result of mass curving space-time). Black holes are part of the general theory of relativity. To start they were a mathematical quirk of Einstein’s field equations, but the discovery of Cygnus X-1 showed that black holes were not a mathematical quirk.
Further observations about black holes have been made over time adding to the theory and supporting the existence of these massive objects. Accretion disks, relativistic jets, active galactic nuclei, gravitational waves and other observations were all documented well before the Event Horizon Telescope document M87*’s shadow.
None of these observations, including the observation of a shadow, have moved black holes out of the realm of scientific theory. Instead, they help keep black holes as active parts of the general theory of relativity.
Science writers and communicators need to take extra caution when using terms like theory, theoretical, law, fact, hypothesis or conjecture. They have different meanings inside and outside of the sphere of science and using them inappropriately can build a false impression of what science does; that in turn can cause misunderstandings and mistrust of science as a whole.
I am not without fault and am often rereading and refamiliarizing myself with the different terms. It is part and parcel of the job as a science communicator. One of my go-to’s is this article from liveScience.com. Writer or reader, it is probably worth a second look and remember to give critical consideration when you see those terms in an article.
When I get the chance to visit my friend and his father on their family property, I always find myself whisked away to a different place or time. I’m not sure what it is about this former farmstead tucked away in the urban parts of Winnipeg, if it’s the Guffleworfs that stand watch along the driveway, the ability to feel like I’m in nature far outside of the city with an intrusive development of cookie cutter homes just behind the tree lines, or perhaps it is the tea and conversation that comes up with my friend’s father.
At 97 he is ever eager to listen and talk, to verbally parry and repost with his son in the same playful teasing way I grew up with in my family and he is always willing to talk about the war. He feels he must talk about it to make sure the sacrifices made are not forgotten and lost.
At the age of twenty and an only child, he left his widowed mother and the family farm to go to war. He could have stayed home, as the only child on a farm we would not have been obligated to go but go he did. He was part of the D-day landings, spent the war with his tank crew mostly ahead of the line, reporting back from their various observation posts. Then, he came back home, if only because, as he says, he dug more slip trenches than anyone else in the war.
The World Wars demanded great sacrifice and affected entire generations, but those individuals fought willingly for the freedoms, liberties and lifestyle we have today in hopes that we would never have to go to war again to preserve them. Yet, when we are faced with a climate crisis, as we knowingly continue to consume and put our livelihoods, liberties and freedoms at risk, we sit back and lose ourselves to the media-rich world we are a part of.
In the 1980s a small group of scientists came forward and warned us about a growing hole the ozone of Earth’s atmosphere. This small band was able to inspire, mobilize and change not only habits but laws. The world came together, and the growth of that hole stopped and has even reserved.
How is it then that when 97% of scientists agree on the human nature of climate change and that we need to act on it, we sit immobile – worse still we deny and refute. Are we that much farther in time from the Great Wars that their meaning, their importance, their sacrifice has been lost to us?
How can this be? I am only a generation removed from the war! My grandmother, God rest her soul, would be furious to see how we take all our liberties for granted, how we consume without forethought, how we squander and deny. As a spy for the resistance in Poland, she did not risk her life, suffer torture, and flee her homeland leaving family and all her possessions behind so that we should sit back and forget.
Although I know the real threats of climate change and know all too well it is happening right now, I am also guilty of my own complacencies. However, it is the memory of my grandmother, the look in the eye of my friend’s father, the Gretas, the Malalas, the students behind the Never Again movement that push me to step up and prepare myself to make sacrifices of my own, because we are already fighting World War Three for the future of our children’s lives, rights and liberties.
The enemy may not be a clear and present danger that we can name like in the past two Great Wars because it is sly, silent and ingrained. It is our own complacency, our own blurred views of what is a right and what is a privilege, our lapses in memory that privileges have responsibilities.
Freedom of movement is a right. Owning a car (or three) is a privilege.
Access to food and water is a right. Having tropical fruits and water in plastic bottles is a privilege.
We have to make changes and we are past the point of asking for them, we must take a stand and demand them! Demand reconciliation for our Indigenous populations so they can be heard!
Demand that public transit is accessible to help the impoverished and get the redundant use of personal cars off the road.
Demand for better active transportation so we can use healthy alternative means of getting around.
Demand that companies move to profit sharing so that the people who actually do the work can afford to live.
Demand that our packaging be 100% recyclable.
Demand that our governments enforce that producers and consumers take responsibility for the end use of their products.
Demand green energy sectors.
Demand, demand, demand and demand again!
How? Simple, like those who went to war before us, stand up and make sacrifices. Unlike during the Great Wars, these sacrifices are merely inconvenient at worst – they won’t kill you or those you love.
Are your vegetables wrapped in plastic? Don’t buy them and speak to the manager on the way out saying you won’t buy until they stop importing food items in plastic.
Do you drive to work alone in a car that can fit five? Carpool, take transit, walk, bike, commute!
Tempted to buy that new phone? Don’t. Use yours until it stops working and make sure it is recycled at the end.
Grow a garden, mow your lawn by hand, write to your politicians, have friends over for dinner, talk, discuss …
We have sat in our trenches of complacency too long and guess what? The sergeant is coming, and we all know what they will say, “Move soldier! Over the top! This climate war won’t win itself!”
The buzz around the lunch table and my group’s D&D table is about the image of the black hole shadow in the galaxy M87 (M87*). People are talking, discussing, conjecturing and even imagining the future of space or time travel. Moments like this are great for both the scientific community and the public as it creates intrigue, wonder, and gets both communities talking with each other.
The shadow is really quite amazing, though it should not be confused with the event horizon as some lunchtime conversations have. The shadow of M87* is something separate from the event horizon and perhaps the best way to describe the shadow is to chat D&D, or Harry Potter if you prefer. Either way, we need to talk cloaks of invisibility.
Black holes are already invisible by their own right. They pull in light that comes towards them and trap it forever. This makes photographing them directly a pipe dream because there is never any light leaving them for us to see. The only way to see the presence of black holes is either when they have an accretion disk or strong jets, like M87*, or through their gravitational influence, like Sagittarius A* at the centre of our galaxy zipping stars around it at breakneck speeds.
A perfect cloak of invisibility might not absorb light like a black hole but instead works by bending the light around the person and focusing it on the other side again, giving the appearance of no one being in the way of the light. This type of cloak will also prevent you from ever being photographed because you too are not sending out any light to be captured by a camera. Unfortunately, not every treasure chest in your dungeon will have one, nor do most average witches and wizards have access to a personal Dumbledore. Us regular dungeon crawlers and novice wizards and witches are more likely to get a cloak of partial invisibility (or a cloak of un-invisibility, which is mostly good for a half decent ghost costume at your next themed party).
If we are lucky enough to get a partial cloak of invisibility it will bend light around you, but it may have some tells. The fringes might shimmer, objects might be blurry, or your feet are clearly visible because it is too short and there goes that lovely bonus on your sneak attack rolls (and forget that practical joke of levitating your friend’s lunch with wingardium leviosa unseen).
Black holes can act as a partial cloak of invisibility when lensing distant objects behind them. We still cannot see the black hole directly, but we see the multiple images of the object behind it being projected in a ring around the black hole. In this way, it gives itself away without revealing any interesting details about itself.
Like a lensing black hole, your cloak of partial invisibility is not working out very well and you’ve been spotted. If you can’t stay out of sight, maybe try being seen but not recognized. For this trick, you’ll need a hula hoop of light, available in lower level dungeons or your local Weasleys’ Wizard Wheezes.
By keeping the hula hoop of light spinning around you, you might give yourself away, but people will probably be too distracted by the really neat shadow you’re creating between you and the hula hoop.
Most of the light from the part of the hoop that is behind you is absorbed by your faulty cloak of invisibility. Some of the light, however, is bent around you and focussed in front of you ahead of where the absorbed light should have been focused. The region where the absorbed light should have appeared is dark because it has no light being bent into it – in effect a shadow.
Ah, but what of the light from the ring in front of you that is cast backwards you say? Sharp eye young adventurer (wizard or witch), but just like the light from behind, the light going from the ring towards you gets absorbed by the faulty cloak or bent around behind you – no reflected light reaches an observer. With this disguise, you might not go unnoticed, but you could try for the Guinness Book of World Records as the first shadow to ever hula hoop.
In the case of M87* its hula hoop of light is the photon ring that surrounds it. Just like our hoop, most of the light from behind the black hole is pulled in, while some of it is bent around and refocused in front ahead of where the missing light would appear under perfect conditions – just like with our cloak.
This leaves a dark region in front of the black hole between it and the distorted image of the photon ring (The ring is larger on the bottom because it is rotating towards us at that point. The Doppler shift makes it brighter – that’s another article.). The shadow exists in front of the event horizon but behind the ring and this is why it is interesting. The shadow’s presence is sort of a rough outline of the event horizon, but unlike the event horizon, the light that goes into the shadow has a chance of escaping – albeit slim. This is also what makes the image so amazing, by seeing the shadow we are effectively looking at a black hole. We have finally taken a picture of the one thing we’ve not been able to take a picture of directly. By seeing a shadow we have an outline of the event horizon! I would call that rolling a natural 20 or a performing a perfect Patronus as far as photos go.