Can Interstellar Travel Be Possible?

**SPEAKER_1** (0:00)
No one goes to Hank's for his spreadsheets. They go for a darn good pizza. Lately though, the shop's been quiet. So Hank decides to bring back the $1 slice. He asks Copilot in Microsoft Excel to look at his sales and costs, help him see if he can afford it. Copilot shows Hank where the money's going, and which little extras make the dollar slice work. Now Hank says, line out the door. Hank makes the pizza, Copilot handles the spreadsheets. Learn more at m365copilot.com/work.

**SPEAKER_2** (0:30)
You said this place was steps from the water.

**SPEAKER_3** (0:32)
We just haven't found the steps yet.

**SPEAKER_4** (0:35)
How much did we save?

**SPEAKER_7** (0:37)
Enough.

**SPEAKER_6** (0:39)
Enough to get lost.

**SPEAKER_7** (0:41)
Or you could book a stay with Hilton.

**SPEAKER_2** (0:43)
Welcome to your ocean front room, just steps from the water.

**SPEAKER_7** (0:46)
The Hilton sale is on now. Book on hilton.com or the Hilton app, and save up to 20 percent to get the stay you expected. When you want savings, not surprises, it matters where you stay. Hilton. For the stay.

**Matt O'Dowd** (1:00)
Space is pretty deadly. But is it so deadly that we are effectively imprisoned in our solar system forever?
Many have claimed that this is the case, but a few scientists have actually figured it out.
Ever since Enrico Fermi asked his famous question, where is everybody? We've pondered the mystery of the Fermi paradox. In a galaxy where billions of planets have had billions of years to spawn technological civilizations, why don't we see any evidence of those that came before us? There are many possible answers to this, varying from the uplifting, like the idea that we are among the first to overcome some extreme evolutionary challenges, to the horrific, like the prospect that every civilization reaching our level of advancement subsequently annihilates itself. We've mentioned all of these before, but there is a very commonly cited explanation that we've never explored. It's perhaps the most boring explanation possible. We've avoided it because, frankly, I don't want it to be the real answer to the Fermi paradox.
It's the idea that we don't see aliens because interstellar travel is just way too hard for anyone to bother. Technological civilizations like our own may rise and fall, some may reach heights of sophistication and advancement far exceeding our own, but none ever manage to populate the galaxy because sending living creatures between the stars is so difficult that it's just not worth it. So today we're going to explore this question. Is humanity doomed to spend the rest of our species' lifespan huddled in our own solar system? There are two factors that make interstellar travel difficult. The first and most obvious, and the one you already know about, is also the most solvable, and that's the absurdly large distances involved. The nearest star, Proxima Centauri, is 4.2 light years away.
It would take the fastest spacecraft we've ever built, that's the 163 km per second of the Parker Solar Probe, over 7,000 years to reach Proxima, if it were even going in the right direction.
For humans to travel to the stars, travel time needs to at least be the order of a human lifetime, which means traveling at relativistic speeds, sizable fractions of the speed of light. But this is actually a solvable problem. The Breakthrough Starshot program proposes to send a train of tiny craft powered by solar sails which would be accelerated to 20% light speed by a giant array of lasers back on Earth. These crafts are little more than computer chips, and sending humans means many orders of magnitude more mass for life support and shielding. But there are proposed advanced forms of propulsion that could in principle accelerate a proper spacecraft to a fair fraction of the speed of light. For example, really, really, really big light sails, or compact fusion drives, or matter-antimatter engines. Some of these may be achievable in the distant but foreseeable future. The issue of the crazy distances should be completely solvable, if it weren't for the second problem, which is that interstellar space wants to murder us. ISM is the official acronym, not Interstellar Murder, but the Interstellar Medium. The space between the stars in our galaxy is far from empty. It's filled with diffused gas and dust grains. This stuff may be sparse, but at relativistic speeds, every molecule becomes a tiny bullet. And that's to say nothing of cosmic rays, particles moving fast enough to kill us all on their own. This is the number one potential deal-breaker for our future as...

**SPEAKER_9** (5:01)
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