Travelling At 99% of The Speed Of Light Looks Strange - Project Hail Mary's Space Warp Transcript, AI Summary & Key Points

00:04 Hello, it's Scott Manley here. Project Hail Mary is probably my favorite film of the year and I love the fact that so many people who aren't fans of science fiction love the movie. Like many science fiction movies, it takes place around another star light years from Earth. But unlike a lot of sci-fi universes, there is no warp drive or hyperspace or hey those wormholes that were used in interstellar which I previously did a video on.

00:29 No, the titular hail Mary has to cross the gulf between the stars at sublight speed experiencing relativistic time dilation. And this is why when he sets course for Earth, it tells him it'll be something like 3 to 4 years. Even although the distance is about 12 lighty years, he is experiencing time dilation which will slow time for him and make it seem like the journey happens faster.

00:54 The spacecraft's propulsion system is fueled by something called astrophase which is basically a living thing that eats stars, stores up the energy, and basically can store more energy than anything else that we can imagine in real life. But it's really convenient if you want to fling a spacecraft between stars at 99.5% of the speed of light. And I've seen a lot of discussion about all this, the relativistic travel, the energy storage, etc.

01:21 I haven't seen anyone mention what it would look like if you are actually traveling at 99.5% of the speed of light. Now again, sci-fi loves to have things like the stars turning into streaks of light and hyperspace tunnels and all that, but that's not the reality of what we're dealing with. The stars are simply too far apart to become streaks. This is what it would look like if you were traveling towards the constellation of Orion at one light per second.

01:47 So that's about 10 million times the speed that you would experience if you looked out the window of the Hail Mary at the halfway point. And this is the more realistic version. Now, I know many of you out there are thinking, you know, I think he's just paused the video there. And maybe you're right. But at 60 frames per second, that means the next frame is expected in 2 days time.

02:07 Stick around, I guess. But even with the complete lack of motion in the stars around you, there would still be some very obvious evidence that you were traveling close to the speed of light. And I bet you're already thinking, "Oh yeah, Doppler effect. We would see red shift and blue shift in the stars around us." And this is just a simple visualization.

02:28 It is not accurate because at 99.5% of the speed of light, those things in the red are being redshifted beyond the infrared. And from the other side, these things are these stars become incredibly bright. If you take an object like a star and you red or blue shift, it's the same as changing its effective temperature to the observer. And at 99.5% of the speed of light, the objects in front of you have their temperature increased by a factor of 20 and behind they're decreased by a factor of 20.

02:58 So the the sun would be about 290 Kelvin, which basically would be the same temperature as the Earth, which looks fine in infrared, but is basically not emitting any visible light on its own. And so, you know, it was at this point in the story where I thought, "Oh, I'll mention that Star Trek in their warp drive scenes, they used to stretch out their stars into different colors."

03:19 And this was supposed to be a reference to the the Doppler shift. And then I looked for some images on the internet and realized that no, they weren't actually doing that. They were just doing whatever the VFX artist thought looked cool. So, yeah. Uh, I guess I remembered it that way because I was a physics nerd rather than paying attention. Now, far fewer of you are familiar with the aberration effects.

03:41 And this is where as you accelerate, you know, faster and faster, the world kind of distorts around you. If you look behind you, the world seems to start getting magnified. And if you look ahead of you, the world actually seems to be shrinking. So, naively, it looks like while you're accelerating towards your target, it appears to be getting smaller and further away.

04:03 And this is a consequence of the fact that light is moving at a finite speed. And as you are moving through these photons, you're encountering them at an angle which depends upon your velocity relative to them. Right? It is a vector problem, right? It's just like you're flying through space and you suddenly hit this photon which is coming from the side, but because you're going forwards, it seems to come from ahead of you.

04:25 It's the same as driving a car through a rainstorm. you see more rain hitting the front of the car than hitting the sides or the rear of the car. The difference being that the car typically is going faster than the rain, whereas with the speed of light, you can't actually go faster than it. And while I'm talking about this, in this sci-fi world of interstellar travel, regular astronomers have to deal with this every day or at least every night because, you know, they do things at night.

04:51 But yeah uh the velocity of the earth around the sun is 30 km/s and that means there's 60 km/s between you know 6 months separating the orbit. That means that light from distant stars finds itself bent subtly by this velocity of the the earth around the sun and so you have to subtract that out if you're doing astrometry. Anyway, this simple diagram shows how light rays coming from different angles have their apparent position adjusted based upon the velocity.

05:21 And as you go faster and faster, more and more of the objects appear to be coming in front of you as you get up to really, really high velocities. It appears that the entire universe gets sucked into a circle just in front of your spacecraft. But there's another part to this because as these light rays are getting closer and closer together, that is kind of like magnifying them.

05:42 If a patch of the sky that's say 10° by 10° gets squished down to say 1 degree by one degree, that means you've got the same amount of light coming from 100th of the area. Therefore, it has to be 100 times as bright. So you get what's called the search light effect, right? A beaming effect. And not only is the light getting brighter because of this, it's also getting blue shifted and therefore much much brighter still.

06:06 And so to help visualize this even better, there is this project on GitHub by Dimmitri Lavough which demonstrates this. On the left side, you set your acceleration and it will simulate, you know, one year per second of time lapse. Now, we're passing 60% of the speed of light and the stars ahead of us are definitely starting to get brighter. And in the bottom right, you can start to see that there's some time dilation effect.

06:31 Our ship time is getting behind the world time, which means we are aging more slowly. As we're getting up to 95% of the speed of the light, the stars ahead are all looking super super blue. Our time dilation is getting stronger and stronger. And again, the world is condensing into this small area in front of us. Everything that disappears from that is getting redshifted beyond what we can see.

06:54 And of course the visible light that we see while it is getting blue shifted up into the ultraviolet we can't see the infrared that is also getting shifted up into the visible. So we never run out of stars. The stars never disappear on the blue side. It's only on the rear side where they're getting redshifted to below zero. Now as we start going faster and faster we'll start to see things that would just be too faint, too red for humans to see.

07:20 things like nebula uh that may be glowing in the infrared. And yeah, even although you're setting constant acceleration, we can never actually reach the speed of light. The mass of the spacecraft increases due to relativity. So the amount of acceleration gets smaller and smaller as we get closer and closer to the speed of light. But yeah, as I said, some of those faint things like nebula and stuff are now getting bright enough that we can see them.

07:45 And eventually the cosmic microwave background radiation which is normally at 2.7 Kelvin is now getting raised to a temperature where it glows red. And as we go faster and faster, it too starts to get blue shifted way up until it is a shining light. We are staring into the remnants of the big bang itself. I hope you brought your sunglasses. But coming back to the Hail Mary, it isn't nearly so fast.

08:13 It's only going 99.5% of the speed of light at the halfway point. But I did want to give an idea of what you might see if you poked your head out when it was traveling that fast. And this is a basic render in Blender. Like so. The model comes from a model website. I think it's originally based on a Juno new origins build. But the skybox, it comes from Space Engine.

08:37 It's been processed with uh my code that generates the aberration and the blue shifting. I had to actually dial down the beaming somewhat. Also, the route between Saul and Taittita pretty much is perpendicular to the disc of the galaxy. So, you end up seeing the entire disc of the galaxy as a ring in the sky in front of you. The red shift angle also kind of dialed down a bit so that you could actually see that there was some texture behind the spacecraft.

09:03 And so while I used a single still image for that skybox, I did actually create a visualization of what it would look like as you were transversing the distance between Saul and the tow sittai. So yeah, it's actually a 360 render, but those 360 videos never seem to get as many as much interest as I would like. So I will share those in links so that you can actually stick on your VR headset and point your head wherever you like.

09:30 But for now again you can see how the galaxy which was out my side windows at the start is now you know collecting in front of me and getting very very blue. And again I have scaled down the beaming here because I don't have enough HDR capability inside the video you know player inside YouTube. Understand that this would be hundreds of times brighter than the image behind you.

09:54 By the time you reach 95% of the speed of light, the light from all the stars in front of you is about as bright as a full moon. Once you're at 99.5% of the speed of light, the light is something like 100 times the brightness of a full moon. So, it's equivalent to a well-lit room. But the average temperature of that light is so high that is beaming lots of ultraviolet at you.

10:16 So, you would get a sunburn really quickly. And now we're about the halfway point. We're about to hit top speed. And as soon as we get there, we flip over and we start decelerating. And now the decrease in the aberration means that it looks like we are getting closer to our target. So all this is to say that while Project Hail Mary didn't need any sci-fi warp drives to travel between the stars, space is still going to look pretty warped to an observer traveling at 99% of the speed of light.

10:43 I'm Scott Manley. Fly safe. >> [music]