Moon's Slow Farewell, Alien Civilization Odds, and NASA's Cosmic Communication

0:00 Anna: Welcome to Astronomy Daily,

0:03 your source for the latest news and

0:05 discoveries from across the cosmos.

0:08 I'm Anna.

0:09 Avery: And I'm Avery. We've got a fabulous show

0:12 lined up today with some truly mind bending

0:15 science. We're talking about how our Moon

0:18 is slowly but surely drifting away from

0:20 Earth, why alien civilizations might be

0:23 much rarer than we thought, and how

0:25 NASA guides spacecraft through the vast

0:28 emptiness of space.

0:30 Anna: Plus, we'll catch you up on this week's busy

0:33 launch schedule. So let's dive right in

0:36 with something that might surprise you.

0:39 Did you know that every single day the

0:42 Moon gets a tiny bit further away from

0:45 us?

0:46 Avery: It's true. The Moon is drifting away from

0:48 earth at about 1.5 inches per

0:51 year. That might not sound like much, but

0:53 over millions of years, it really adds up.

0:56 And we can measure this incredibly precisely,

0:59 thanks to something left behind by the Apollo

1:02 astronauts.

1:03 Anna: You're talking about those retroreflector

1:06 mirrors, right? The Apollo crews place these

1:09 special mirror arrays on the lunar surface,

1:11 and scientists have been bouncing laser beams

1:14 off them ever since to measure the exact

1:17 distance to the Moon. It's one of the most

1:19 precise measurements in all of astronomy.

1:23 Avery: Exactly. And the reason this is happening is

1:25 actually pretty fascinating. It all comes

1:28 down to tidal forces. The Moon's gravity

1:31 creates those familiar ocean tides on Earth.

1:34 But here's the Earth's rotation

1:36 is faster than the Moon's orbital period.

1:40 This creates a slight bulge in Earth's

1:42 oceans that's actually ahead of the Moon as

1:45 it orbits.

1:46 Anna: So that tidal bulge is essentially

1:49 pulling the Moon forward in its orbit, which

1:52 increases its orbital energy and makes it

1:55 spiral outward. It's like a cosmic

1:58 dance where Earth is gradually pushing its

2:00 partner away. And there's another

2:03 consequence. This process is also making

2:05 Earth's days slightly longer over time.

2:09 Avery: The evidence for this is really cool.

2:11 Scientists have studied fossilized clamshells

2:14 that show growth patterns from 70 million

2:16 years ago during the age of dinosaurs. Those

2:19 patterns tell us that back then, a day

2:22 was only about 23.5 hours

2:25 long. The Moon was closer, Earth spun

2:28 faster, it was a different world.

2:30 Anna: And if we go way back to when the Moon

2:33 first formed four and a half billion years

2:36 ago, after that massive collision between

2:38 Earth and a Mars sized object, the Moon

2:41 would have been dramatically closer. We're

2:44 talking about it appearing maybe 10 times

2:46 larger in the sky. The tides would have been

2:49 enormous and days would have been just a

2:52 few hours long. That early Earth Moon system

2:55 must have been absolutely spectacular to

2:58 witness. Can you imagine those

3:00 massive tides? We're talking about ocean

3:03 tides, potentially hundreds of feet high,

3:05 Surging across the planet Every few hours,

3:09 the moon would have looked like this enormous

3:11 disk Dominating the sky.

3:13 Avery: And here's what's really fascinating about

3:16 the physics. This process Won't continue

3:19 forever. Eventually, Earth and the moon

3:22 Will become tidally Locked to each other,

3:24 which means Earth's rotation Will slow down

3:27 until one day equals one lunar month,

3:30 roughly 47 of our current days. At

3:33 that point, the same side of Earth Will

3:35 always face the moon, Just like the same side

3:38 of the moon Always faces us.

3:40 Anna: Now, that brings up something that really

3:42 hits home for eclipse enthusiasts like us.

3:46 The moon is gradually moving away,

3:48 which means total solar eclipses Are becoming

3:51 rarer and, and will eventually disappear

3:54 altogether. Right now, the moon is

3:57 just the perfect size to block out the sun's

3:59 disk During a total eclipse. But as it moves

4:02 away and appears smaller in our sky, we'll

4:05 start seeing more annular eclipses, where you

4:07 get that beautiful ring of fire effect

4:10 Instead of totality.

4:11 Avery: The timeline is mind boggling, though. We're

4:13 talking about Hundreds of millions of years

4:15 before total solar eclipses Become

4:17 impossible. So while future generations Will

4:20 miss out on one of nature's most spectacular

4:23 shows, Human has plenty of time to catch

4:25 these incredible events. In fact, we're

4:27 living During A cosmically special time, the

4:30 brief window when the moon and sun Appear

4:33 Almost exactly the same size in our sky. It's

4:36 incredible to think about how that ancient

4:37 catastrophe Shaped not just our planet, but

4:39 continues to influence us today.

4:42 Speaking of planetary formation and what

4:44 makes world habitable, um, there's some new

4:46 research that's pretty sobering about our

4:48 prospects of finding alien civilizations.

4:51 Anna: Oh, this is the study about plate tectonics.

4:53 Right. The researchers are arguing that

4:56 technological civilizations Might need plate

4:59 tectonics and something called the carbon

5:01 silicate cycle to survive long enough to

5:04 actually develop advanced technology.

5:06 Avery: Exactly. The basic idea is that without plate

5:09 tectonics, Constantly recycling carbon

5:11 through volcanic activity and rock

5:13 weathering, CO2 levels would just keep rising

5:15 and rising. Eventually, you'd get A runaway

5:18 greenhouse effect that would make the planet

5:19 uninhabitable, Kind of like what happened to

5:21 Venus. The carbon silicate cycle

5:24 Is really the planetary thermostat that keeps

5:27 earth habitable. Here's how it works. When it

5:30 gets too hot, More water evaporates and

5:32 creates more rain, which increases rock

5:35 weathering. That weathering pulls

5:37 CO2 out of the atmosphere and locks

5:40 it into carbonate rocks. When it gets too

5:43 cold, Volcanic activity releases

5:46 stored CO2 back into the atmosphere

5:48 While warming things up again. It's this

5:51 incredible self regulating system that's

5:54 kept Earth's temperature relatively stable

5:56 for billions of years.

5:58 Anna: And Venus is the perfect cautionary tale

6:01 here. Venus probably started out much more

6:04 Earth like, but without active plate

6:06 tectonics to recycle carbon, CO2

6:09 just kept building up in the atmosphere. The

6:12 result, surface temperatures hot enough to

6:14 melt lead, cool, crushing atmospheric

6:17 pressure and sulfuric acid clouds. It's a

6:20 hellscape that shows us exactly what happens

6:22 when a, uh, planet loses its carbon silicate

6:25 cycle.

6:26 Avery: This research has huge implications for seti,

6:29 the search for Extraterrestrial intelligence.

6:31 It suggests we might need to focus more on

6:33 planets with clear signs of active geology,

6:36 not just planets in the habitable zone. We'd

6:38 want to look for atmospheric signatures that

6:40 indicate active volcanism and weathering

6:42 cycles. And it's also related to what

6:44 scientists call the Great Filter, the idea

6:46 that there might be some extremely difficult

6:48 step in the evolution from simple chemistry

6:51 to a galaxy spanning civilization.

6:53 Anna: The numbers are pretty staggering. The study

6:55 estimates that it might take anywhere from a

6:58 thousand to a million rocky planets for

7:01 just one to develop into an Earth like world

7:03 with the kind of long term climate stability

7:06 needed for complex life to evolve and, and

7:09 eventually develop technology.

7:11 Avery: And if this research is correct, it pushes

7:13 the nearest potential extraterrestrial

7:16 intelligence way out to maybe

7:18 33,000 light years away. Even

7:21 more challenging for alien civilizations to

7:23 exist at the same time as us, they'd need to

7:26 last an average of 280,000 years or more.

7:29 That's a long time for any technological

7:31 species to survive.

7:32 Anna: It really makes you appreciate how special

7:34 Earth might be. We've got this perfect

7:37 balance of plate tectonics, the right

7:39 distance from the sun, a large, large

7:41 stabilizing moon, and probably

7:44 dozens of other factors that had to line up

7:46 just right. Of course, we're still looking.

7:49 And that's where missions like the ones

7:51 launching this week come in.

7:53 Avery: Let's talk launches. It's going to be a busy

7:55 week. SpaceX has four missions on the

7:58 schedule, including three Starlink launches

8:00 to continue building out their satellite

8:02 Internet constellation. Plus one mission

8:05 called NROL 48 for the national

8:07 Reconnaissance Office. That's the secretive

8:09 one where we probably won't get many details

8:11 about the payload.

8:12 Anna: The mission I'm most excited about is Blue

8:15 Origin's New Shepard NS35,

8:18 finally launching Thursday after several

8:21 delays. This one's carrying over 40

8:24 different experiments, including 24

8:26 student payloads from NASA's TechRise student

8:29 challenge. Plus they're taking thousands of

8:32 postcards to space, which I think is just

8:34 delightful. The New Shepard mission is

8:37 particularly Interesting from a scientific

8:39 standpoint. Among those 40 plus

8:42 experiments, they're testing everything from

8:45 crystal growth in microgravity to plant

8:48 biology studies. Several experiments are

8:50 investigating how different materials behave

8:53 in the brief microgravity environment, which

8:56 is incredibly valuable for manufacturing

8:58 research. Um, the student payloads are

9:01 testing things like seed germination,

9:03 fluid dynamics, and even how social

9:06 media algorithms might work in space

9:08 environments.

9:09 Avery: The Starlink launches are pretty impressive

9:12 from, uh, a technical standpoint, too. The

9:14 Constellation now has over 5,000 active

9:17 satellites in orbit, making it by far the

9:19 largest satellite constellation ever

9:21 deployed. And SpaceX's booster

9:24 reuse program continues to break records.

9:27 Some of these Falcon 9 first stages have

9:28 flown more than 15 times each.

9:31 That's revolutionary when you consider that

9:34 just a few years ago rockets were completely

9:36 expendable. The cost savings are allowing

9:39 them to launch these massive Constellation

9:41 buildouts that would have been economically

9:43 impossible before.

9:45 Anna: I love that. And there's something

9:47 wonderfully old fashioned about sending

9:49 postcards to space in this digital age.

9:52 And don't forget about Tuesday's Chinese

9:54 launch and, uh, a Chang Zang 2C rocket

9:57 carrying what's described only as an unknown

10:00 payload. The mystery always adds a bit of

10:02 intrigue.

10:03 Speaking of space missions, we've had a query

10:05 from one of our listeners, Josh, asking how

10:08 on Earth do we maintain contact with all of

10:11 our spacecraft in deep space? Good question,

10:14 Josh. Once these spacecraft get beyond

10:17 Earth orbit, they enter a realm where GPS

10:19 doesn't work and navigation becomes

10:22 incredibly complex. And that's where

10:24 NASA's Deep Space Network comes in. It's

10:27 honestly one of the most impressive

10:29 technological achievements that most people

10:31 have never heard of.

10:33 Avery: The DSN is basically NASA's lifeline to

10:36 everything we've sent beyond Earth orbit.

10:38 It's a network that is made up of three

10:40 massive antenna complexes, one in California,

10:43 one in Spain, and one in Australia,

10:46 spaced exactly 120 degrees apart around

10:48 the globe. This means that as Earth rotates,

10:51 at least one complex always has line of sight

10:54 contact with any spacecraft in the solar

10:56 system. The navigation challenges are

10:59 absolutely staggering when you really think

11:01 about them. Take Voyager 2, for example.

11:04 It's currently at about 12.8 billion

11:06 miles from Earth in a completely unique

11:09 position below the plane of the solar system.

11:11 Command sent to Voyager 2 take over 18 hours

11:14 just to reach the spacecraft, and then

11:17 another 18 hours for any response to come

11:19 back. That means if something goes wrong,

11:22 mission controllers have to wait more than a

11:23 day and a half just to know if their fix

11:25 worked.

11:26 Anna: The precision required for antenna pointing

11:29 is just incredible. These dishes need to be

11:32 aimed so Accurately that they can target a

11:34 spacecraft millions of miles away to within a

11:37 fraction of a degree. It's like trying to hit

11:40 a coin with a laser pointer from across an

11:42 entire city. And they have to constantly

11:45 adjust for the motion of both Earth and the

11:47 spacecraft, which plus account for things

11:49 like atmospheric refraction and even

11:52 the slight bending of radio waves by the

11:54 Sun's gravity.

11:56 Avery: This incredible precision is what enables

11:58 those amazing gravity assist maneuvers that

12:00 would be impossible Otherwise. When Voyager 2

12:03 flew by Jupiter, Saturn, Uranus and

12:06 Neptune, each encounter had to be timed

12:08 within minutes and positioned within hundreds

12:11 of miles to get the trajectory exactly right

12:13 for the next target. One small navigation

12:16 error early in the mission and Voyager 2

12:18 would have missed Uranus by millions of

12:20 miles. The fact that we can execute these

12:23 cosmic billiard shots across decades of

12:25 flight time is testament to the incredible

12:27 engineering of the Deep Space Network.

12:30 Anna: The precision is mind boggling. These

12:32 antennas can track spacecraft millions of

12:35 miles away by measuring incredibly tiny

12:38 time delays in radio signals and

12:41 detecting minute Doppler shifts in

12:43 frequency. They're essentially doing

12:46 celestial GPS calculations using

12:49 the time it takes for signals to travel at

12:51 the speed of light to determine exact

12:53 positions and velocities.

12:56 Avery: And, um, the range of missions it supports is

12:58 incredible. We're talking about the Voyager

13:00 probes, which are now in interstellar space

13:03 over 15 billion miles away. Mars

13:05 rovers like Perseverance and Curiosity, all

13:08 the lunar missions and everything in between.

13:11 Each one requires constant communication for

13:14 telemetry commands and navigation updates.

13:17 Anna: The future is getting even more exciting with

13:20 optical communications. NASA's testing

13:23 something called the Deep Space Optical

13:25 Communications Experiment, or

13:27 dsoc, on the Psyche mission.

13:30 Instead of radio waves, they're using laser

13:33 light to send data back to Earth. It's like

13:36 upgrading from dial up to fiber optic

13:38 Internet, but for spacecraft. If you'd like

13:41 to find out more about the Deep Space

13:42 Network, head over to our

13:44 [email protected] and check

13:47 out our latest blog post where we take a deep

13:50 dive into the subject. I hope that answers

13:52 your question, Josh.

13:54 Avery: Before we wrap up, let's quickly touch on a

13:56 couple more stories. Firefly Aerospace got

13:59 some good news. Their Alpha rocket has been

14:01 cleared to fly again after April's failure.

14:03 The investigation found that extreme heat and

14:06 something called plume induced flow

14:09 separation caused the problem, but they've

14:11 apparently worked out the fixes.

14:14 Anna: And mark your calendars for September 23rd.

14:17 NASA's launching three space weather

14:19 missions, all at IMAP. The

14:22 Carruthers, Geocarona Observatory

14:25 and SWFOL1.

14:28 These will study how solar activity affects

14:31 our solar system and help us better predict

14:34 space weather that could could impact

14:35 satellites and astronauts.

14:37 Avery: That's particularly timely because the sun's

14:40 activity has been ramping up significantly

14:42 since 2008 after decades of

14:45 relatively quiet behavior. This has major

14:48 implications for space weather and the safety

14:50 of astronauts on future long duration

14:52 missions to the Moon and Mars.

14:55 Anna: That's all for today's Astronomy Daily. From

14:58 our slowly departing moon to the search for

15:00 alien civilizations, from busy launch

15:03 schedules, to the incredible engineering that

15:05 keeps us connected to robotic explorers

15:08 across the solar system, there's never a dull

15:11 moment in space science.

15:13 Avery: Thanks for joining us today. Keep looking up

15:15 and we'll see you tomorrow with more news

15:17 from the final frontier. I'm, um, Avery.

15:20 Anna: And I'm Anna. Until tomorrow, stay

15:22 curious about the cosmos.