We continue our annual countdown of the ten most exciting, important, and fun stories from the world of science in 2020 during this Pulsar podcast brought to you by #MOSatHome. We ask questions submitted by listeners, so if you have a question you'd like us to ask an expert, send it to us at sciencequestions@mos.org.

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ANNOUNCER: 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0, ignition, liftoff, goes the Falcon 9 and Crew Dragon. Go NASA, go SpaceX! Godspeed, Bob and Doug!

ERIC: That was the countdown that our Current Science and Technology team had been waiting for a long time. And so, of course, it rated highly on our list of the top 10 science stories of 2020.

We're back with part three of our countdown of the most exciting, important, and awesome stories from the world of science last year. Joining me again to finish our Top 10 Countdown, is Sarah, from Current Science and Technology.

Sarah, thanks for coming back on.

SARAH: Let's go, number one, we're going to get there.

ERIC: All right, well, let's start where we left off, and that is a story that give us a lot of buzz in 2020. Our number five story was murder hornets, which wasn't a big impact, but it did make a ton of headlines, right in the middle of 2020, while we were all at home, and the pandemic had turned everything upside down. It was one of those, and murder hornets, type things.

SARAH: Yeah, I saw a lot of people saying, oh, great, what else is 2020 going to throw at us? Or, there are a lot of jokes about the writers room for 2020 coming up with murder hornets, now. But it turns out, it is actually a really interesting story of invasive species, and how animals move, and how animals are transported, and all these things. And it also is a sign that coming up with a catchy name, it sure can get your story heard.

ERIC: It's so true. People are asking us if they should be worried about murder hornets, and we were like, no, you shouldn't be. But I will teach you all the science about it, because it's such a cool story.

SARAH: Right, right. Not worried about it, in the way you think.

So these hornets are also known as the Asian giant hornet, and they are, oh, boy, really big-- they are like three inches long. So if you look down at your hand, this hornet would about cover the palm. That's a big bug.

ERIC: Yeah, I don't want that bug anywhere near me.

SARAH: And the murder is question, because we have to get to why they have this name, murder hornet. They do not murder humans, but bees, that is their primary prey. As you all probably are aware, we were already concerned about the population of, especially, wild bees in the United States.

When we look at the story of the murder hornet, it's not a story of crazy bugs from outer space coming to kill humans. It's actually a story about how, because of the fact that we do transport things across the ocean-- we use ships, we use planes, we use all kinds of things that animals would never have been able to access before-- that means that animals can travel huge distances. This is how the common rat was spread from Mongolia to the entire world during the 1600s, because it just caught a ride on ships, and then spread all over the place. So this hornet, which is native to East Asia, made its way to the western United States, and now, there's a small population of these hornets, who are an invasive species.

ERIC: Yeah, we've had problems with invasive species for centuries, because they can really mess with the balance of an ecosystem. They don't have any natural predators. They prey on things that are not at all prepared to defend against them, and there's a lot of other problems with it.

SARAH: Do you remember hearing people freak out about murder hornets, and then say, oh, that turned out to be nothing?

ERIC: Right. Oh, murder hornets aren't going to be descending on cities in swarms? Then, why should I care about it? And it turns out, that it's still important. We should care about it, because bees have enough to worry about. Between colony collapse and climate change and pesticide problems, the more we study how bees are doing, the less confident I feel about how bees are doing. And they're really important. They pollinate so many things. So much of our crops are pollinated by bees, that having murder hornets become endemic to the United States, and having them spread out of control, would really be very bad.

SARAH: And I think that the problem is really one of communication, which is that we want people to be aware of the fact that having an unusual species in their area can be really problematic. But this was a known problem. Entomologists, bug scientists, had already noted that this population of Asian giant hornet could make its way across the ocean. There were only two that were confirmed to be found in Washington, and then after that, everyone was like, I saw a murder hornet in my backyard! And you probably didn't. It is still a story about how we need to defend our native species, and how we need to be mindful of how human travel can affect things. But I will say that this is one where our colleagues, who are more bug experts than we are, were just groaning at this, at the name, because they were like, this is a big problem, but murder hornets, really? And then, people said, oh, it turned out to be nothing, but it is actually still a concern.

ERIC: All right. So for a number four, we lumped a couple of things together into wildfires. And there was a lot of wildfire stories in 2020, starting in the beginning of the year with Australia, and some record-setting wildfires there. And then, ending in the fall with a lot in the United States, particularly, the western United States.

SARAH: Yeah, this was-- it doesn't even feel like this year, in some ways, because Australia, being in the Southern Hemisphere, their summer, and therefore, their wildfire season, is in Northern Hemisphere winter. This was December and January, especially December 2019 into January 2020, entering into the peak of Australia's wildfire season. And, oh, boy, there were satellite pictures, pictures from space of Australia, where you could just see how much of the continent was burning. It's really, really scary.

ERIC: Yeah, and a lot of effect on wildlife. The statistic that we had in our live stream was three billion animals affected by the wildfires, in some way. But also, a lot of impact on humans, too - thousands of buildings, thousands of homes destroyed.

SARAH: The Indigenous, the Aboriginal people of Australia, they lost a huge amount of neighborhoods, of living places. And then, yeah, of course, whenever we think of Australia, we always think of that unique wildlife, right? Our honorable mention was the platypus. We love Australia for its unique and incredible array of wildlife, and these wildfires really do, genuinely, put this in peril.

Obviously, there have always been fires. Wildfires are a natural part of the process of life, for any sort of forest environment, because as trees die and vegetation dies, that tends to build up, and can eventually choke the growth of new plants. And so, wildfires are a natural part of that cleansing process.

However, there's two problems. One problem is that when you have humans living in this area, we can't really adapt to that wildfire. Obviously, we can't just let our homes get burned down every 10 years, and then build a new home-- that's not how it works. And also, we are seeing an increase in the severity and frequency of these fires. They're becoming more difficult to fight, more difficult to contain, more difficult to predict, and that's a real problem.

ERIC: And then, the wildfires in the US showed all the different ways that wildfires can start. There's natural causes like lightning, there's power lines, there's people throwing cigarettes out of windows. And then, there was a big story this year, of all things, a gender reveal party with pyrotechnics, that lit one of the most devastating fires of the whole year.

SARAH: That was a little frustrating to hear. We always want to know that people are being mindful and careful of the environment, but especially when you live in an area that has a certain risk, it's good to be aware of that risk.

ERIC: All right, we're going to end on a more positive note. And also, going to leave plenty of time for us to geek out about our number three story, because I'm sure we're going to talk about it for an hour. It was, finally, the United States launching astronauts to orbit from the United States soil, for the first time in almost a decade.

SARAH: Yeah, this was so exciting, so cool, literally groundbreaking. As Eric just said, this is a new landmark.

So this was the Dragon space capsule, launched by SpaceX on one of their Falcon 9 rockets, going up to the International Space Station, and delivering a couple of astronauts there. So you said almost a decade - when is the last time that we launched astronauts from the United States?

ERIC: So we had the space shuttle, and we had it for the '80s, the '90s, the 2000s, and then, the last flight was in 2011. And the idea was, that we'd retire the space shuttles, and then bring the next way to get to space online to overlap with that, so that by the time the space shuttle retired, we already had another rocket to launch astronauts to space.

SARAH: How did that plan go?

ERIC: Yeah, that turned into, we have a plan for the next rocket, but it won't be ready exactly on time for the space shuttle to retire. And then, it turned into, well, we don't know what we're going to do for a while. And then, it turned into, well, the Russians are still going to space-- we'll just buy a seat on their capsule, which is called the Soyuz. And that turns into the most expensive taxi ride ever. They were paying maybe $60, $70, $80 million for one seat on the Soyuz capsule to launch the American astronauts up to the Space Station, which wasn't a great situation.

SARAH: And, obviously, this has been effective. The International Space Station has been continuously occupied for 20 years now. And from 2011 until this year, there were, indeed, lots of astronauts launched up on the Soyuz spacecraft, which launches from Kazakhstan. So that involves a lot of travel. It's out in the middle of nowhere. It's a very little rocket, and what's known as a workhorse rocket, which means that this is a rocket that was designed in the '70s, and that's it. It is still doing what it's been doing since the '70s. It's a good rocket, does what it's supposed to do, but SpaceX does something totally different.

SpaceX is a company that has made many, many, many records in spaceflight, and that is for pretty much one reason, which is that their rockets are reusable.

ERIC: So exciting to watch the rockets go up, deliver their payload into space, and then come back down and land on the ground, eight minutes later.

When they first started to imagine this in 2008, or 2009, a lot of people said, that's not possible, you can't do that, you can't do it the way you're thinking. And then, they just went ahead and did it. And now, they've done it-- I don't even keep track of how many times they do it anymore. I used to have it off the top of my head, that they've done it 20 times, or 30 times. Earlier this week, they set their own record, from one rocket booster landing for the eighth time-- it's launched eight different things to space.

So just thinking about that for a second-- you don't have to build a brand new rocket every time you launch something to space. How much cheaper is your space program going to be?

SARAH: Right. And we have numbers. I know that the Falcon Heavy, which is SpaceX's largest rocket-- it's not literally three rocket strapped together, but it looks like three rockets strapped together-- and that's, currently, the largest working rocket on the planet. It was built for less than 10% of the cost of one Saturn V rocket, which is the rocket that launched the Apollo astronauts, and it can be reused. As we were seeing, 5, 6, 10 times, it can be reused. So this is incredible. It requires a huge amount of engineering. It requires some landing pads, which are basically drone ships out in the ocean, that are there to catch rockets. It's pretty incredible.

SpaceX has been working with NASA for about seven years now. They have had occasional contracts, that they've launched some things to the International Space Station, which has been really great. They've launched satellites, and things like that, for the United States. But the one thing they had not launched was people, and that's because no private spaceflight company had ever launched people.

They got these two astronauts--

ERIC: Bob and Doug.

SARAH: Bob and Doug, yeah. I was like, are their names Bob and Doug? That's in my head. They have these two astronauts, Bob and Doug, and they are in the Dragon space capsule, which is also built by SpaceX, and which is much roomier than the Soyuz capsule. If you ever look at pictures of astronauts on the Soyuz capsule, I always think it looks like pictures of someone in a car after the airbag has gone off. It looks like someone who's just squished in place. The Dragon capsule is much larger, a little bit roomier.

And, yeah, we got to watch, for the first time ever, these people walking into this new rocket, designed in just the last decade, in Florida, which is the launch site of so many incredible missions. They were able to walk up, walk into, sit down, in the rocket, and the rocket launched. It was so great to see it go up. We got to see all these stages, we got to see the footage of the astronauts just kicking it in the capsule. They don't really have to do that much, they don't have to fly it.

ERIC: Just making sure everything goes right, but the spaceship pretty much flies itself, at this point.

SARAH: And then, the rocket landed successfully, which was great, always fun to see. Although, we also like it when the rocket doesn't land correctly, because then you get to see crazy footage of a rocket exploding, which is fun.

ERIC: Remember, they don't like the term explosion.

SARAH: Oh, yes.

ERIC: They like to call it a rapid, unscheduled disassembly.

SARAH: Yes, I love to see rockets rapidly disassemble, unscheduled.

ERIC: And so, Bob and Doug went up in May, as the test for this. They went to the Space Station, they stayed for a couple of months, they came back down. Everything went great, so they approved the next mission, and now, it's just routine.

So the next mission launched later in 2020, bringing four astronauts up to the Space Station-- they're there now while we're talking. The next mission is planned for a couple of weeks from now. And so, SpaceX will continue to deliver astronauts to the Space Station.

It's really exciting that the capsule, as you mentioned, is roomy, because there's room for another person, which means the chores get spread out a lot thinner on the Space Station. There's a lot of maintenance, there's a lot of upkeep to the Space Station. What we really want to do, is maximize the amount of research that we can do, because that's what the Space Station is all about, being able to study the human body in space, to install telescopes to study the sky, to be able to look at materials, and make medicines, and all these things. That's why we have the Space Station. To get more person time on the station dedicated to science, is my favorite part of the story.

SARAH: Any time that the science gets more accessible, more reusable, cheaper, then, suddenly, it also becomes more frequent. And so, we're going to see more astronauts going up. This opens up more possibilities for astronauts from other space agencies to decide how they want to get to the Space Station.

So it's amazing. This is a great year for spaceflight, even with everything happening with the pandemic. That's another thing that's important to remember, is that all of this happened during a pandemic. They were still able to launch space missions, they were still able to launch astronauts. And, as we have said, in this year, with 2020, with the Dragon capsule, we've now entered into a new era of American spaces flight, where we're back in the time of having American astronauts launch from Cape Canaveral. Just makes you happy.

ERIC: We've got two more entries to go on our countdown. Don't miss the exciting conclusion of our Top 10 later this week. Until next time, keep asking questions.

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