How worried to be about asteroid 2024 YR4

A student visited my office today asking about an asteroid she heard about in the news.  As though we needed something else to worry about, right? NASA now predicts a roughly 3% likelihood that asteroid 2024 YR4 will hit our planet.  On Dec 22, 2032, YR4, a football-field sized asteroid travelling around 17 km/s, will reach us and hopefully miss.

Students are usually surprised that we can predict the arrival of this body with so much precision (the exact date) so long in advance.  What makes it relatively easy to do is that the asteroid is on an elliptical path around the Sun.  All other bodies have little to no influence on it.  Knowledge of the asteroid's position, speed, and direction at any moment enables us to predict its future trajectory around the Sun with great accuracy.  The 'when' of it is extremely precise, but the 'where' of it has some uncertainty, hence the 3% chance.  For now, we can draw an area of a certain size in space that YR4 will shoot through on Dec 22, 2032, and Earth will fill a small portion of that space at that time.

The amount of energy carried by an asteroid is the key metric for assessing the level of damage its collision with Earth would cause.  The energy is usually expressed as 'equivalent to X megatons of TNT explosives', which does nothing to calm fears that the public may have.  The good news regarding 2024 YR4 is that it would collide with an energy equivalent to about '10 Megatons of TNT' (that is 10,000,000 tons, but still about 100,000 times less than the one that marked the end of the Jurassic).  

Though this is not an extinction sort of asteroid, the press has called it a city killer, because it needs to sound at least a little scary.  But the term is also appropriate, because the footprint of destruction were this asteroid to strike Earth would be in the area of 2,000 square kilometers, which is bigger than most cities.  I mean, even 1 ton of TNT is not something I'd want to set off in my backyard, so 10,000,000 of them sounds like it very well could level a city.

So, what do we do?  For now, we wait, and keep monitoring it.  With more precise data, the likelihood could eventually reduce to 0%.  The trouble is, in the unlikely event that the odds increase dramatically, a plan will need to be made and launched in a hurry.

Will the plan involve Bruce Willis and nuclear bombs being detonated from inside the asteroid?  Sadly, no.  Not only is this a way more impractical option for many reasons (like, nukes in space, what could go wrong?), we also could not be completely sure of its outcome.  A more elegant approach would be to launch a large rocket right into YR4, to change its course at just the right moment (small changes of direction lead to large deviations later in a trajectory).  This approach has been successfully tested before: NASA's DART mission successfully deflected an asteroid larger than this one in 2022.

The tricky part is determining when or if to 'pull the trigger'. DART cost over 300M USD, so it is not something to undertake just for fun (though it does sound extremely fun!).

How much should we worry?  Not much, for now, but we will take a very careful look at YR4 when it passes our neighborhood of the solar system next in 2028, and reassess.  Still, it is nice to know that we have a plan that has worked in the past if YR4's trajectory gets too close for comfort.

Viral Fake Physics Videos

I have spent most of my career with an eye towards fighting science misinformation.  This has been a losing battle, of course, but one I feel a duty to see through.  Typically, I take aim at outlandish claims made by people with hidden agendas, from classics like "Burning fossil fuels does not contribute to climate change" to "Just wear this bracelet and your ailments will disappear."  Those hits keep on coming, but there is a new kid on the block that really has me scratching my head.

As 2025 begins, there has been a sudden uptick in the number of fake physics videos appearing in my social media feeds.  Fake physics videos are not to be confused with deep fakes, which involve AI.  In these fake physics videos, we have random people setting up what look to be legitimate physics demonstrations.  They lay out spoons and batteries and suddenly a coin appears to levitate.  In the next, they show a collision between marbles that appears to defy Newton's laws.  After some digging, I discovered that the former uses a camera trick and the latter hides a magnet in some of the spheres.

I am a bit dumbfounded over this... I despise the traditional McScientists who seek to disinform people, but at least I understand that foe.  They have a purpose, misguided though it may be.  Like, the way a wasp buzzing around your head is just an unfortunate manifestation of nature, so too are McScientists.  But what to make of this new thing?

There are so many excellent physics videos out there.  The best of them show an experimental setup, allow the audience to formulate a prediction on what will happen, then run the demonstration, and finish off with a clear explanation of the physics principles at work.  Veritasium and The Slow Mo Guys are two of my favourite YouTube channels containing countless videos of this sort.  The take home message is that physics is fascinating.  Nature, without trickery, is mind-blowing on its own.  What purpose does misleading people about science serve?  Like, "I have them questioning Newton's Laws!" or "Now they'll learn physics wrong, hah!"

When you stop and think of it, magic shows are similar to this.  Whether it is sleight of hand or another illusion, magic always seeks to leave audiences surprised by what they are seeing.  But there is an important difference: in a magic show, the whole premise is "I am going to try to fool you, see if you can spot how."  The audience is, effectively, in on it.  And besides being (sometimes) entertaining, magic shows test the audience's critical thinking.  Fake physics videos are posing as the real deal.  If they began by stating, "The demo you are about to see has been faked in some way, see if you can figure out how," I could get on board with that.

I'm proud that I was able to spot that these videos were disingenuous. If I'm being honest, I kind of enjoyed debunking them.  I'm even tempted to show them to my students.

But I still don't understand the motivation for making the videos.  Is it just for attention? It is, isn't it?  Geez.  The twenty-first century is no time for an idealist like me.